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* [PATCH v6 00/17] re-enable DAX PMD support
@ 2016-10-12 22:50 ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner, linux-nvdimm,
	Christoph Hellwig, linux-xfs, linux-mm, Andreas Dilger,
	Alexander Viro, linux-fsdevel, Jan Kara, linux-ext4,
	Andrew Morton

DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
locking.  This series allows DAX PMDs to participate in the DAX radix tree
based locking scheme so that they can be re-enabled.

For now I'm still using the same baseline for this series as I did with v5.
I'll update the baseline once v4.9-rc1 is released, dropping whatever patches
have already been merged.

Changes since v5:
 - Reworked the way that DAX radix tree flags were handled. The old
   handling was correct but a bit hard for the reader to parse.  Hopefully
   this new way is more readable & maintainable.  (Jan & Christoph)
 - Made the definition of dax_radix_order() conditional based on
   CONFIG_FS_DAX_PMD.  This was necessary because PMD_SHIFT isn't defined
   on all systems. (kbuild)
 - Dropped the incorrect patch "ext2: return -EIO on ext2_iomap_end()
   failure".  (Jan)
 - A few error path fixes in grab_mapping_entry().  (Jan)
 - A few more comments in grab_mapping_entry(),
   dax_wake_mapping_entry_waiter() and dax_insert_mapping_entry(). (Jan)
 - Removed the 'inline' keyword from dax_iomap_sector().  (Dan)
 - Cleaned up the path through ops->iomap_end() in both dax_iomap_fault()
   and dax_iomap_pmd_fault().  We now pass 0 for the 'written' argument on
   error conditions.  (Jan & Christoph)
 - Improved the naming of 'size' to 'max_pgoff' in dax_iomap_pmd_fault().
   (Jan)

Thank you to Jan and Christoph for their review feedback.

Here is a tree containing my changes:
https://git.kernel.org/cgit/linux/kernel/git/zwisler/linux.git/log/?h=dax_pmd_v6

This tree has passed xfstests for ext2, ext4 and XFS both with and without
DAX, and has passed targeted testing where I inserted, removed and flushed
DAX PTEs and PMDs in every combination I could think of.

Ross Zwisler (17):
  ext4: allow DAX writeback for hole punch
  ext4: tell DAX the size of allocation holes
  dax: remove buffer_size_valid()
  ext2: remove support for DAX PMD faults
  dax: make 'wait_table' global variable static
  dax: remove the last BUG_ON() from fs/dax.c
  dax: consistent variable naming for DAX entries
  dax: coordinate locking for offsets in PMD range
  dax: remove dax_pmd_fault()
  dax: correct dax iomap code namespace
  dax: add dax_iomap_sector() helper function
  dax: dax_iomap_fault() needs to call iomap_end()
  dax: move RADIX_DAX_* defines to dax.h
  dax: move put_(un)locked_mapping_entry() in dax.c
  dax: add struct iomap based DAX PMD support
  xfs: use struct iomap based DAX PMD fault path
  dax: remove "depends on BROKEN" from FS_DAX_PMD

 fs/Kconfig          |   1 -
 fs/dax.c            | 825 +++++++++++++++++++++++++++++-----------------------
 fs/ext2/file.c      |  35 +--
 fs/ext4/inode.c     |   7 +-
 fs/xfs/xfs_aops.c   |  26 +-
 fs/xfs/xfs_aops.h   |   3 -
 fs/xfs/xfs_file.c   |  10 +-
 include/linux/dax.h |  58 +++-
 mm/filemap.c        |   5 +-
 9 files changed, 538 insertions(+), 432 deletions(-)

-- 
2.9.0

_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

^ permalink raw reply	[flat|nested] 126+ messages in thread
* [PATCH v6 00/17] re-enable DAX PMD support
@ 2016-10-12 22:50 ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
locking.  This series allows DAX PMDs to participate in the DAX radix tree
based locking scheme so that they can be re-enabled.

For now I'm still using the same baseline for this series as I did with v5.
I'll update the baseline once v4.9-rc1 is released, dropping whatever patches
have already been merged.

Changes since v5:
 - Reworked the way that DAX radix tree flags were handled. The old
   handling was correct but a bit hard for the reader to parse.  Hopefully
   this new way is more readable & maintainable.  (Jan & Christoph)
 - Made the definition of dax_radix_order() conditional based on
   CONFIG_FS_DAX_PMD.  This was necessary because PMD_SHIFT isn't defined
   on all systems. (kbuild)
 - Dropped the incorrect patch "ext2: return -EIO on ext2_iomap_end()
   failure".  (Jan)
 - A few error path fixes in grab_mapping_entry().  (Jan)
 - A few more comments in grab_mapping_entry(),
   dax_wake_mapping_entry_waiter() and dax_insert_mapping_entry(). (Jan)
 - Removed the 'inline' keyword from dax_iomap_sector().  (Dan)
 - Cleaned up the path through ops->iomap_end() in both dax_iomap_fault()
   and dax_iomap_pmd_fault().  We now pass 0 for the 'written' argument on
   error conditions.  (Jan & Christoph)
 - Improved the naming of 'size' to 'max_pgoff' in dax_iomap_pmd_fault().
   (Jan)

Thank you to Jan and Christoph for their review feedback.

Here is a tree containing my changes:
https://git.kernel.org/cgit/linux/kernel/git/zwisler/linux.git/log/?h=dax_pmd_v6

This tree has passed xfstests for ext2, ext4 and XFS both with and without
DAX, and has passed targeted testing where I inserted, removed and flushed
DAX PTEs and PMDs in every combination I could think of.

Ross Zwisler (17):
  ext4: allow DAX writeback for hole punch
  ext4: tell DAX the size of allocation holes
  dax: remove buffer_size_valid()
  ext2: remove support for DAX PMD faults
  dax: make 'wait_table' global variable static
  dax: remove the last BUG_ON() from fs/dax.c
  dax: consistent variable naming for DAX entries
  dax: coordinate locking for offsets in PMD range
  dax: remove dax_pmd_fault()
  dax: correct dax iomap code namespace
  dax: add dax_iomap_sector() helper function
  dax: dax_iomap_fault() needs to call iomap_end()
  dax: move RADIX_DAX_* defines to dax.h
  dax: move put_(un)locked_mapping_entry() in dax.c
  dax: add struct iomap based DAX PMD support
  xfs: use struct iomap based DAX PMD fault path
  dax: remove "depends on BROKEN" from FS_DAX_PMD

 fs/Kconfig          |   1 -
 fs/dax.c            | 825 +++++++++++++++++++++++++++++-----------------------
 fs/ext2/file.c      |  35 +--
 fs/ext4/inode.c     |   7 +-
 fs/xfs/xfs_aops.c   |  26 +-
 fs/xfs/xfs_aops.h   |   3 -
 fs/xfs/xfs_file.c   |  10 +-
 include/linux/dax.h |  58 +++-
 mm/filemap.c        |   5 +-
 9 files changed, 538 insertions(+), 432 deletions(-)

-- 
2.9.0

^ permalink raw reply	[flat|nested] 126+ messages in thread
* [PATCH v6 00/17] re-enable DAX PMD support
@ 2016-10-12 22:50 ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
locking.  This series allows DAX PMDs to participate in the DAX radix tree
based locking scheme so that they can be re-enabled.

For now I'm still using the same baseline for this series as I did with v5.
I'll update the baseline once v4.9-rc1 is released, dropping whatever patches
have already been merged.

Changes since v5:
 - Reworked the way that DAX radix tree flags were handled. The old
   handling was correct but a bit hard for the reader to parse.  Hopefully
   this new way is more readable & maintainable.  (Jan & Christoph)
 - Made the definition of dax_radix_order() conditional based on
   CONFIG_FS_DAX_PMD.  This was necessary because PMD_SHIFT isn't defined
   on all systems. (kbuild)
 - Dropped the incorrect patch "ext2: return -EIO on ext2_iomap_end()
   failure".  (Jan)
 - A few error path fixes in grab_mapping_entry().  (Jan)
 - A few more comments in grab_mapping_entry(),
   dax_wake_mapping_entry_waiter() and dax_insert_mapping_entry(). (Jan)
 - Removed the 'inline' keyword from dax_iomap_sector().  (Dan)
 - Cleaned up the path through ops->iomap_end() in both dax_iomap_fault()
   and dax_iomap_pmd_fault().  We now pass 0 for the 'written' argument on
   error conditions.  (Jan & Christoph)
 - Improved the naming of 'size' to 'max_pgoff' in dax_iomap_pmd_fault().
   (Jan)

Thank you to Jan and Christoph for their review feedback.

Here is a tree containing my changes:
https://git.kernel.org/cgit/linux/kernel/git/zwisler/linux.git/log/?h=dax_pmd_v6

This tree has passed xfstests for ext2, ext4 and XFS both with and without
DAX, and has passed targeted testing where I inserted, removed and flushed
DAX PTEs and PMDs in every combination I could think of.

Ross Zwisler (17):
  ext4: allow DAX writeback for hole punch
  ext4: tell DAX the size of allocation holes
  dax: remove buffer_size_valid()
  ext2: remove support for DAX PMD faults
  dax: make 'wait_table' global variable static
  dax: remove the last BUG_ON() from fs/dax.c
  dax: consistent variable naming for DAX entries
  dax: coordinate locking for offsets in PMD range
  dax: remove dax_pmd_fault()
  dax: correct dax iomap code namespace
  dax: add dax_iomap_sector() helper function
  dax: dax_iomap_fault() needs to call iomap_end()
  dax: move RADIX_DAX_* defines to dax.h
  dax: move put_(un)locked_mapping_entry() in dax.c
  dax: add struct iomap based DAX PMD support
  xfs: use struct iomap based DAX PMD fault path
  dax: remove "depends on BROKEN" from FS_DAX_PMD

 fs/Kconfig          |   1 -
 fs/dax.c            | 825 +++++++++++++++++++++++++++++-----------------------
 fs/ext2/file.c      |  35 +--
 fs/ext4/inode.c     |   7 +-
 fs/xfs/xfs_aops.c   |  26 +-
 fs/xfs/xfs_aops.h   |   3 -
 fs/xfs/xfs_file.c   |  10 +-
 include/linux/dax.h |  58 +++-
 mm/filemap.c        |   5 +-
 9 files changed, 538 insertions(+), 432 deletions(-)

-- 
2.9.0

--
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^ permalink raw reply	[flat|nested] 126+ messages in thread
* [PATCH v6 00/17] re-enable DAX PMD support
@ 2016-10-12 22:50 ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel-u79uwXL29TY76Z2rM5mHXA
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner,
	linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw, Christoph Hellwig,
	linux-xfs-u79uwXL29TY76Z2rM5mHXA,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg, Andreas Dilger, Alexander Viro,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA, Jan Kara,
	linux-ext4-u79uwXL29TY76Z2rM5mHXA, Andrew Morton

DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
locking.  This series allows DAX PMDs to participate in the DAX radix tree
based locking scheme so that they can be re-enabled.

For now I'm still using the same baseline for this series as I did with v5.
I'll update the baseline once v4.9-rc1 is released, dropping whatever patches
have already been merged.

Changes since v5:
 - Reworked the way that DAX radix tree flags were handled. The old
   handling was correct but a bit hard for the reader to parse.  Hopefully
   this new way is more readable & maintainable.  (Jan & Christoph)
 - Made the definition of dax_radix_order() conditional based on
   CONFIG_FS_DAX_PMD.  This was necessary because PMD_SHIFT isn't defined
   on all systems. (kbuild)
 - Dropped the incorrect patch "ext2: return -EIO on ext2_iomap_end()
   failure".  (Jan)
 - A few error path fixes in grab_mapping_entry().  (Jan)
 - A few more comments in grab_mapping_entry(),
   dax_wake_mapping_entry_waiter() and dax_insert_mapping_entry(). (Jan)
 - Removed the 'inline' keyword from dax_iomap_sector().  (Dan)
 - Cleaned up the path through ops->iomap_end() in both dax_iomap_fault()
   and dax_iomap_pmd_fault().  We now pass 0 for the 'written' argument on
   error conditions.  (Jan & Christoph)
 - Improved the naming of 'size' to 'max_pgoff' in dax_iomap_pmd_fault().
   (Jan)

Thank you to Jan and Christoph for their review feedback.

Here is a tree containing my changes:
https://git.kernel.org/cgit/linux/kernel/git/zwisler/linux.git/log/?h=dax_pmd_v6

This tree has passed xfstests for ext2, ext4 and XFS both with and without
DAX, and has passed targeted testing where I inserted, removed and flushed
DAX PTEs and PMDs in every combination I could think of.

Ross Zwisler (17):
  ext4: allow DAX writeback for hole punch
  ext4: tell DAX the size of allocation holes
  dax: remove buffer_size_valid()
  ext2: remove support for DAX PMD faults
  dax: make 'wait_table' global variable static
  dax: remove the last BUG_ON() from fs/dax.c
  dax: consistent variable naming for DAX entries
  dax: coordinate locking for offsets in PMD range
  dax: remove dax_pmd_fault()
  dax: correct dax iomap code namespace
  dax: add dax_iomap_sector() helper function
  dax: dax_iomap_fault() needs to call iomap_end()
  dax: move RADIX_DAX_* defines to dax.h
  dax: move put_(un)locked_mapping_entry() in dax.c
  dax: add struct iomap based DAX PMD support
  xfs: use struct iomap based DAX PMD fault path
  dax: remove "depends on BROKEN" from FS_DAX_PMD

 fs/Kconfig          |   1 -
 fs/dax.c            | 825 +++++++++++++++++++++++++++++-----------------------
 fs/ext2/file.c      |  35 +--
 fs/ext4/inode.c     |   7 +-
 fs/xfs/xfs_aops.c   |  26 +-
 fs/xfs/xfs_aops.h   |   3 -
 fs/xfs/xfs_file.c   |  10 +-
 include/linux/dax.h |  58 +++-
 mm/filemap.c        |   5 +-
 9 files changed, 538 insertions(+), 432 deletions(-)

-- 
2.9.0

^ permalink raw reply	[flat|nested] 126+ messages in thread
* [PATCH v6 00/17] re-enable DAX PMD support
@ 2016-10-12 22:50 ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
locking.  This series allows DAX PMDs to participate in the DAX radix tree
based locking scheme so that they can be re-enabled.

For now I'm still using the same baseline for this series as I did with v5.
I'll update the baseline once v4.9-rc1 is released, dropping whatever patches
have already been merged.

Changes since v5:
 - Reworked the way that DAX radix tree flags were handled. The old
   handling was correct but a bit hard for the reader to parse.  Hopefully
   this new way is more readable & maintainable.  (Jan & Christoph)
 - Made the definition of dax_radix_order() conditional based on
   CONFIG_FS_DAX_PMD.  This was necessary because PMD_SHIFT isn't defined
   on all systems. (kbuild)
 - Dropped the incorrect patch "ext2: return -EIO on ext2_iomap_end()
   failure".  (Jan)
 - A few error path fixes in grab_mapping_entry().  (Jan)
 - A few more comments in grab_mapping_entry(),
   dax_wake_mapping_entry_waiter() and dax_insert_mapping_entry(). (Jan)
 - Removed the 'inline' keyword from dax_iomap_sector().  (Dan)
 - Cleaned up the path through ops->iomap_end() in both dax_iomap_fault()
   and dax_iomap_pmd_fault().  We now pass 0 for the 'written' argument on
   error conditions.  (Jan & Christoph)
 - Improved the naming of 'size' to 'max_pgoff' in dax_iomap_pmd_fault().
   (Jan)

Thank you to Jan and Christoph for their review feedback.

Here is a tree containing my changes:
https://git.kernel.org/cgit/linux/kernel/git/zwisler/linux.git/log/?h=dax_pmd_v6

This tree has passed xfstests for ext2, ext4 and XFS both with and without
DAX, and has passed targeted testing where I inserted, removed and flushed
DAX PTEs and PMDs in every combination I could think of.

Ross Zwisler (17):
  ext4: allow DAX writeback for hole punch
  ext4: tell DAX the size of allocation holes
  dax: remove buffer_size_valid()
  ext2: remove support for DAX PMD faults
  dax: make 'wait_table' global variable static
  dax: remove the last BUG_ON() from fs/dax.c
  dax: consistent variable naming for DAX entries
  dax: coordinate locking for offsets in PMD range
  dax: remove dax_pmd_fault()
  dax: correct dax iomap code namespace
  dax: add dax_iomap_sector() helper function
  dax: dax_iomap_fault() needs to call iomap_end()
  dax: move RADIX_DAX_* defines to dax.h
  dax: move put_(un)locked_mapping_entry() in dax.c
  dax: add struct iomap based DAX PMD support
  xfs: use struct iomap based DAX PMD fault path
  dax: remove "depends on BROKEN" from FS_DAX_PMD

 fs/Kconfig          |   1 -
 fs/dax.c            | 825 +++++++++++++++++++++++++++++-----------------------
 fs/ext2/file.c      |  35 +--
 fs/ext4/inode.c     |   7 +-
 fs/xfs/xfs_aops.c   |  26 +-
 fs/xfs/xfs_aops.h   |   3 -
 fs/xfs/xfs_file.c   |  10 +-
 include/linux/dax.h |  58 +++-
 mm/filemap.c        |   5 +-
 9 files changed, 538 insertions(+), 432 deletions(-)

-- 
2.9.0


^ permalink raw reply	[flat|nested] 126+ messages in thread
* [PATCH v6 01/17] ext4: allow DAX writeback for hole punch
  2016-10-12 22:50 ` Ross Zwisler
                     ` (2 preceding siblings ...)
  (?)
@ 2016-10-12 22:50   ` Ross Zwisler
  -1 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner, linux-nvdimm,
	stable, Christoph Hellwig, linux-xfs, linux-mm, Andreas Dilger,
	Alexander Viro, linux-fsdevel, Jan Kara, linux-ext4,
	Andrew Morton

Currently when doing a DAX hole punch with ext4 we fail to do a writeback.
This is because the logic around filemap_write_and_wait_range() in
ext4_punch_hole() only looks for dirty page cache pages in the radix tree,
not for dirty DAX exceptional entries.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: <stable@vger.kernel.org>
---
 fs/ext4/inode.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 3131747..0900cb4 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3890,7 +3890,7 @@ int ext4_update_disksize_before_punch(struct inode *inode, loff_t offset,
 }
 
 /*
- * ext4_punch_hole: punches a hole in a file by releaseing the blocks
+ * ext4_punch_hole: punches a hole in a file by releasing the blocks
  * associated with the given offset and length
  *
  * @inode:  File inode
@@ -3919,7 +3919,7 @@ int ext4_punch_hole(struct inode *inode, loff_t offset, loff_t length)
 	 * Write out all dirty pages to avoid race conditions
 	 * Then release them.
 	 */
-	if (mapping->nrpages && mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
+	if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
 		ret = filemap_write_and_wait_range(mapping, offset,
 						   offset + length - 1);
 		if (ret)
-- 
2.9.0

_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 01/17] ext4: allow DAX writeback for hole punch
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs, stable

Currently when doing a DAX hole punch with ext4 we fail to do a writeback.
This is because the logic around filemap_write_and_wait_range() in
ext4_punch_hole() only looks for dirty page cache pages in the radix tree,
not for dirty DAX exceptional entries.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: <stable@vger.kernel.org>
---
 fs/ext4/inode.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 3131747..0900cb4 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3890,7 +3890,7 @@ int ext4_update_disksize_before_punch(struct inode *inode, loff_t offset,
 }
 
 /*
- * ext4_punch_hole: punches a hole in a file by releaseing the blocks
+ * ext4_punch_hole: punches a hole in a file by releasing the blocks
  * associated with the given offset and length
  *
  * @inode:  File inode
@@ -3919,7 +3919,7 @@ int ext4_punch_hole(struct inode *inode, loff_t offset, loff_t length)
 	 * Write out all dirty pages to avoid race conditions
 	 * Then release them.
 	 */
-	if (mapping->nrpages && mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
+	if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
 		ret = filemap_write_and_wait_range(mapping, offset,
 						   offset + length - 1);
 		if (ret)
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 01/17] ext4: allow DAX writeback for hole punch
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs, stable

Currently when doing a DAX hole punch with ext4 we fail to do a writeback.
This is because the logic around filemap_write_and_wait_range() in
ext4_punch_hole() only looks for dirty page cache pages in the radix tree,
not for dirty DAX exceptional entries.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: <stable@vger.kernel.org>
---
 fs/ext4/inode.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 3131747..0900cb4 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3890,7 +3890,7 @@ int ext4_update_disksize_before_punch(struct inode *inode, loff_t offset,
 }
 
 /*
- * ext4_punch_hole: punches a hole in a file by releaseing the blocks
+ * ext4_punch_hole: punches a hole in a file by releasing the blocks
  * associated with the given offset and length
  *
  * @inode:  File inode
@@ -3919,7 +3919,7 @@ int ext4_punch_hole(struct inode *inode, loff_t offset, loff_t length)
 	 * Write out all dirty pages to avoid race conditions
 	 * Then release them.
 	 */
-	if (mapping->nrpages && mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
+	if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
 		ret = filemap_write_and_wait_range(mapping, offset,
 						   offset + length - 1);
 		if (ret)
-- 
2.9.0

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 01/17] ext4: allow DAX writeback for hole punch
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel-u79uwXL29TY76Z2rM5mHXA
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner,
	linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw,
	stable-u79uwXL29TY76Z2rM5mHXA, Christoph Hellwig,
	linux-xfs-u79uwXL29TY76Z2rM5mHXA,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg, Andreas Dilger, Alexander Viro,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA, Jan Kara,
	linux-ext4-u79uwXL29TY76Z2rM5mHXA, Andrew Morton

Currently when doing a DAX hole punch with ext4 we fail to do a writeback.
This is because the logic around filemap_write_and_wait_range() in
ext4_punch_hole() only looks for dirty page cache pages in the radix tree,
not for dirty DAX exceptional entries.

Signed-off-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Reviewed-by: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>
Cc: <stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
---
 fs/ext4/inode.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 3131747..0900cb4 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3890,7 +3890,7 @@ int ext4_update_disksize_before_punch(struct inode *inode, loff_t offset,
 }
 
 /*
- * ext4_punch_hole: punches a hole in a file by releaseing the blocks
+ * ext4_punch_hole: punches a hole in a file by releasing the blocks
  * associated with the given offset and length
  *
  * @inode:  File inode
@@ -3919,7 +3919,7 @@ int ext4_punch_hole(struct inode *inode, loff_t offset, loff_t length)
 	 * Write out all dirty pages to avoid race conditions
 	 * Then release them.
 	 */
-	if (mapping->nrpages && mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
+	if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
 		ret = filemap_write_and_wait_range(mapping, offset,
 						   offset + length - 1);
 		if (ret)
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 01/17] ext4: allow DAX writeback for hole punch
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs, stable

Currently when doing a DAX hole punch with ext4 we fail to do a writeback.
This is because the logic around filemap_write_and_wait_range() in
ext4_punch_hole() only looks for dirty page cache pages in the radix tree,
not for dirty DAX exceptional entries.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: <stable@vger.kernel.org>
---
 fs/ext4/inode.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 3131747..0900cb4 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3890,7 +3890,7 @@ int ext4_update_disksize_before_punch(struct inode *inode, loff_t offset,
 }
 
 /*
- * ext4_punch_hole: punches a hole in a file by releaseing the blocks
+ * ext4_punch_hole: punches a hole in a file by releasing the blocks
  * associated with the given offset and length
  *
  * @inode:  File inode
@@ -3919,7 +3919,7 @@ int ext4_punch_hole(struct inode *inode, loff_t offset, loff_t length)
 	 * Write out all dirty pages to avoid race conditions
 	 * Then release them.
 	 */
-	if (mapping->nrpages && mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
+	if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
 		ret = filemap_write_and_wait_range(mapping, offset,
 						   offset + length - 1);
 		if (ret)
-- 
2.9.0


^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 02/17] ext4: tell DAX the size of allocation holes
  2016-10-12 22:50 ` Ross Zwisler
  (?)
  (?)
@ 2016-10-12 22:50   ` Ross Zwisler
  -1 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

When DAX calls _ext4_get_block() and the file offset points to a hole we
currently don't set bh->b_size.  This is current worked around via
buffer_size_valid() in fs/dax.c.

_ext4_get_block() has the hole size information from ext4_map_blocks(), so
populate bh->b_size so we can remove buffer_size_valid() in a later patch.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/ext4/inode.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 0900cb4..9075fac 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -759,6 +759,9 @@ static int _ext4_get_block(struct inode *inode, sector_t iblock,
 		ext4_update_bh_state(bh, map.m_flags);
 		bh->b_size = inode->i_sb->s_blocksize * map.m_len;
 		ret = 0;
+	} else if (ret == 0) {
+		/* hole case, need to fill in bh->b_size */
+		bh->b_size = inode->i_sb->s_blocksize * map.m_len;
 	}
 	return ret;
 }
-- 
2.9.0

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
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^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 02/17] ext4: tell DAX the size of allocation holes
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

When DAX calls _ext4_get_block() and the file offset points to a hole we
currently don't set bh->b_size.  This is current worked around via
buffer_size_valid() in fs/dax.c.

_ext4_get_block() has the hole size information from ext4_map_blocks(), so
populate bh->b_size so we can remove buffer_size_valid() in a later patch.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/ext4/inode.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 0900cb4..9075fac 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -759,6 +759,9 @@ static int _ext4_get_block(struct inode *inode, sector_t iblock,
 		ext4_update_bh_state(bh, map.m_flags);
 		bh->b_size = inode->i_sb->s_blocksize * map.m_len;
 		ret = 0;
+	} else if (ret == 0) {
+		/* hole case, need to fill in bh->b_size */
+		bh->b_size = inode->i_sb->s_blocksize * map.m_len;
 	}
 	return ret;
 }
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 02/17] ext4: tell DAX the size of allocation holes
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel-u79uwXL29TY76Z2rM5mHXA
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner,
	linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw, Christoph Hellwig,
	linux-xfs-u79uwXL29TY76Z2rM5mHXA,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg, Andreas Dilger, Alexander Viro,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA, Jan Kara,
	linux-ext4-u79uwXL29TY76Z2rM5mHXA, Andrew Morton

When DAX calls _ext4_get_block() and the file offset points to a hole we
currently don't set bh->b_size.  This is current worked around via
buffer_size_valid() in fs/dax.c.

_ext4_get_block() has the hole size information from ext4_map_blocks(), so
populate bh->b_size so we can remove buffer_size_valid() in a later patch.

Signed-off-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Reviewed-by: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>
---
 fs/ext4/inode.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 0900cb4..9075fac 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -759,6 +759,9 @@ static int _ext4_get_block(struct inode *inode, sector_t iblock,
 		ext4_update_bh_state(bh, map.m_flags);
 		bh->b_size = inode->i_sb->s_blocksize * map.m_len;
 		ret = 0;
+	} else if (ret == 0) {
+		/* hole case, need to fill in bh->b_size */
+		bh->b_size = inode->i_sb->s_blocksize * map.m_len;
 	}
 	return ret;
 }
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 02/17] ext4: tell DAX the size of allocation holes
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

When DAX calls _ext4_get_block() and the file offset points to a hole we
currently don't set bh->b_size.  This is current worked around via
buffer_size_valid() in fs/dax.c.

_ext4_get_block() has the hole size information from ext4_map_blocks(), so
populate bh->b_size so we can remove buffer_size_valid() in a later patch.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/ext4/inode.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 0900cb4..9075fac 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -759,6 +759,9 @@ static int _ext4_get_block(struct inode *inode, sector_t iblock,
 		ext4_update_bh_state(bh, map.m_flags);
 		bh->b_size = inode->i_sb->s_blocksize * map.m_len;
 		ret = 0;
+	} else if (ret == 0) {
+		/* hole case, need to fill in bh->b_size */
+		bh->b_size = inode->i_sb->s_blocksize * map.m_len;
 	}
 	return ret;
 }
-- 
2.9.0


^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 03/17] dax: remove buffer_size_valid()
  2016-10-12 22:50 ` Ross Zwisler
                     ` (2 preceding siblings ...)
  (?)
@ 2016-10-12 22:50   ` Ross Zwisler
  -1 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner, linux-nvdimm,
	Christoph Hellwig, linux-xfs, linux-mm, Andreas Dilger,
	Alexander Viro, linux-fsdevel, Jan Kara, linux-ext4,
	Andrew Morton

Now that ext4 properly sets bh.b_size when we call get_block() for a hole,
rely on that value and remove the buffer_size_valid() sanity check.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/dax.c | 22 +---------------------
 1 file changed, 1 insertion(+), 21 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index cc025f8..9b9be8a 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -123,19 +123,6 @@ static bool buffer_written(struct buffer_head *bh)
 	return buffer_mapped(bh) && !buffer_unwritten(bh);
 }
 
-/*
- * When ext4 encounters a hole, it returns without modifying the buffer_head
- * which means that we can't trust b_size.  To cope with this, we set b_state
- * to 0 before calling get_block and, if any bit is set, we know we can trust
- * b_size.  Unfortunate, really, since ext4 knows precisely how long a hole is
- * and would save us time calling get_block repeatedly.
- */
-static bool buffer_size_valid(struct buffer_head *bh)
-{
-	return bh->b_state != 0;
-}
-
-
 static sector_t to_sector(const struct buffer_head *bh,
 		const struct inode *inode)
 {
@@ -177,8 +164,6 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
 				rc = get_block(inode, block, bh, rw == WRITE);
 				if (rc)
 					break;
-				if (!buffer_size_valid(bh))
-					bh->b_size = 1 << blkbits;
 				bh_max = pos - first + bh->b_size;
 				bdev = bh->b_bdev;
 				/*
@@ -1012,12 +997,7 @@ int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
 
 	bdev = bh.b_bdev;
 
-	/*
-	 * If the filesystem isn't willing to tell us the length of a hole,
-	 * just fall back to PTEs.  Calling get_block 512 times in a loop
-	 * would be silly.
-	 */
-	if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE) {
+	if (bh.b_size < PMD_SIZE) {
 		dax_pmd_dbg(&bh, address, "allocated block too small");
 		return VM_FAULT_FALLBACK;
 	}
-- 
2.9.0

_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 03/17] dax: remove buffer_size_valid()
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

Now that ext4 properly sets bh.b_size when we call get_block() for a hole,
rely on that value and remove the buffer_size_valid() sanity check.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/dax.c | 22 +---------------------
 1 file changed, 1 insertion(+), 21 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index cc025f8..9b9be8a 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -123,19 +123,6 @@ static bool buffer_written(struct buffer_head *bh)
 	return buffer_mapped(bh) && !buffer_unwritten(bh);
 }
 
-/*
- * When ext4 encounters a hole, it returns without modifying the buffer_head
- * which means that we can't trust b_size.  To cope with this, we set b_state
- * to 0 before calling get_block and, if any bit is set, we know we can trust
- * b_size.  Unfortunate, really, since ext4 knows precisely how long a hole is
- * and would save us time calling get_block repeatedly.
- */
-static bool buffer_size_valid(struct buffer_head *bh)
-{
-	return bh->b_state != 0;
-}
-
-
 static sector_t to_sector(const struct buffer_head *bh,
 		const struct inode *inode)
 {
@@ -177,8 +164,6 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
 				rc = get_block(inode, block, bh, rw == WRITE);
 				if (rc)
 					break;
-				if (!buffer_size_valid(bh))
-					bh->b_size = 1 << blkbits;
 				bh_max = pos - first + bh->b_size;
 				bdev = bh->b_bdev;
 				/*
@@ -1012,12 +997,7 @@ int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
 
 	bdev = bh.b_bdev;
 
-	/*
-	 * If the filesystem isn't willing to tell us the length of a hole,
-	 * just fall back to PTEs.  Calling get_block 512 times in a loop
-	 * would be silly.
-	 */
-	if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE) {
+	if (bh.b_size < PMD_SIZE) {
 		dax_pmd_dbg(&bh, address, "allocated block too small");
 		return VM_FAULT_FALLBACK;
 	}
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 03/17] dax: remove buffer_size_valid()
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

Now that ext4 properly sets bh.b_size when we call get_block() for a hole,
rely on that value and remove the buffer_size_valid() sanity check.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/dax.c | 22 +---------------------
 1 file changed, 1 insertion(+), 21 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index cc025f8..9b9be8a 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -123,19 +123,6 @@ static bool buffer_written(struct buffer_head *bh)
 	return buffer_mapped(bh) && !buffer_unwritten(bh);
 }
 
-/*
- * When ext4 encounters a hole, it returns without modifying the buffer_head
- * which means that we can't trust b_size.  To cope with this, we set b_state
- * to 0 before calling get_block and, if any bit is set, we know we can trust
- * b_size.  Unfortunate, really, since ext4 knows precisely how long a hole is
- * and would save us time calling get_block repeatedly.
- */
-static bool buffer_size_valid(struct buffer_head *bh)
-{
-	return bh->b_state != 0;
-}
-
-
 static sector_t to_sector(const struct buffer_head *bh,
 		const struct inode *inode)
 {
@@ -177,8 +164,6 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
 				rc = get_block(inode, block, bh, rw == WRITE);
 				if (rc)
 					break;
-				if (!buffer_size_valid(bh))
-					bh->b_size = 1 << blkbits;
 				bh_max = pos - first + bh->b_size;
 				bdev = bh->b_bdev;
 				/*
@@ -1012,12 +997,7 @@ int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
 
 	bdev = bh.b_bdev;
 
-	/*
-	 * If the filesystem isn't willing to tell us the length of a hole,
-	 * just fall back to PTEs.  Calling get_block 512 times in a loop
-	 * would be silly.
-	 */
-	if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE) {
+	if (bh.b_size < PMD_SIZE) {
 		dax_pmd_dbg(&bh, address, "allocated block too small");
 		return VM_FAULT_FALLBACK;
 	}
-- 
2.9.0

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
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^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 03/17] dax: remove buffer_size_valid()
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel-u79uwXL29TY76Z2rM5mHXA
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner,
	linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw, Christoph Hellwig,
	linux-xfs-u79uwXL29TY76Z2rM5mHXA,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg, Andreas Dilger, Alexander Viro,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA, Jan Kara,
	linux-ext4-u79uwXL29TY76Z2rM5mHXA, Andrew Morton

Now that ext4 properly sets bh.b_size when we call get_block() for a hole,
rely on that value and remove the buffer_size_valid() sanity check.

Signed-off-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Reviewed-by: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>
Reviewed-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
---
 fs/dax.c | 22 +---------------------
 1 file changed, 1 insertion(+), 21 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index cc025f8..9b9be8a 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -123,19 +123,6 @@ static bool buffer_written(struct buffer_head *bh)
 	return buffer_mapped(bh) && !buffer_unwritten(bh);
 }
 
-/*
- * When ext4 encounters a hole, it returns without modifying the buffer_head
- * which means that we can't trust b_size.  To cope with this, we set b_state
- * to 0 before calling get_block and, if any bit is set, we know we can trust
- * b_size.  Unfortunate, really, since ext4 knows precisely how long a hole is
- * and would save us time calling get_block repeatedly.
- */
-static bool buffer_size_valid(struct buffer_head *bh)
-{
-	return bh->b_state != 0;
-}
-
-
 static sector_t to_sector(const struct buffer_head *bh,
 		const struct inode *inode)
 {
@@ -177,8 +164,6 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
 				rc = get_block(inode, block, bh, rw == WRITE);
 				if (rc)
 					break;
-				if (!buffer_size_valid(bh))
-					bh->b_size = 1 << blkbits;
 				bh_max = pos - first + bh->b_size;
 				bdev = bh->b_bdev;
 				/*
@@ -1012,12 +997,7 @@ int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
 
 	bdev = bh.b_bdev;
 
-	/*
-	 * If the filesystem isn't willing to tell us the length of a hole,
-	 * just fall back to PTEs.  Calling get_block 512 times in a loop
-	 * would be silly.
-	 */
-	if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE) {
+	if (bh.b_size < PMD_SIZE) {
 		dax_pmd_dbg(&bh, address, "allocated block too small");
 		return VM_FAULT_FALLBACK;
 	}
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 03/17] dax: remove buffer_size_valid()
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

Now that ext4 properly sets bh.b_size when we call get_block() for a hole,
rely on that value and remove the buffer_size_valid() sanity check.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/dax.c | 22 +---------------------
 1 file changed, 1 insertion(+), 21 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index cc025f8..9b9be8a 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -123,19 +123,6 @@ static bool buffer_written(struct buffer_head *bh)
 	return buffer_mapped(bh) && !buffer_unwritten(bh);
 }
 
-/*
- * When ext4 encounters a hole, it returns without modifying the buffer_head
- * which means that we can't trust b_size.  To cope with this, we set b_state
- * to 0 before calling get_block and, if any bit is set, we know we can trust
- * b_size.  Unfortunate, really, since ext4 knows precisely how long a hole is
- * and would save us time calling get_block repeatedly.
- */
-static bool buffer_size_valid(struct buffer_head *bh)
-{
-	return bh->b_state != 0;
-}
-
-
 static sector_t to_sector(const struct buffer_head *bh,
 		const struct inode *inode)
 {
@@ -177,8 +164,6 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
 				rc = get_block(inode, block, bh, rw == WRITE);
 				if (rc)
 					break;
-				if (!buffer_size_valid(bh))
-					bh->b_size = 1 << blkbits;
 				bh_max = pos - first + bh->b_size;
 				bdev = bh->b_bdev;
 				/*
@@ -1012,12 +997,7 @@ int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
 
 	bdev = bh.b_bdev;
 
-	/*
-	 * If the filesystem isn't willing to tell us the length of a hole,
-	 * just fall back to PTEs.  Calling get_block 512 times in a loop
-	 * would be silly.
-	 */
-	if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE) {
+	if (bh.b_size < PMD_SIZE) {
 		dax_pmd_dbg(&bh, address, "allocated block too small");
 		return VM_FAULT_FALLBACK;
 	}
-- 
2.9.0


^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 04/17] ext2: remove support for DAX PMD faults
  2016-10-12 22:50 ` Ross Zwisler
                     ` (2 preceding siblings ...)
  (?)
@ 2016-10-12 22:50   ` Ross Zwisler
  -1 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner, linux-nvdimm,
	Christoph Hellwig, linux-xfs, linux-mm, Andreas Dilger,
	Alexander Viro, linux-fsdevel, Jan Kara, linux-ext4,
	Andrew Morton

DAX PMD support was added via the following commit:

commit e7b1ea2ad658 ("ext2: huge page fault support")

I believe this path to be untested as ext2 doesn't reliably provide block
allocations that are aligned to 2MiB.  In my testing I've been unable to
get ext2 to actually fault in a PMD.  It always fails with a "pfn
unaligned" message because the sector returned by ext2_get_block() isn't
aligned.

I've tried various settings for the "stride" and "stripe_width" extended
options to mkfs.ext2, without any luck.

Since we can't reliably get PMDs, remove support so that we don't have an
untested code path that we may someday traverse when we happen to get an
aligned block allocation.  This should also make 4k DAX faults in ext2 a
bit faster since they will no longer have to call the PMD fault handler
only to get a response of VM_FAULT_FALLBACK.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/ext2/file.c | 29 ++++++-----------------------
 1 file changed, 6 insertions(+), 23 deletions(-)

diff --git a/fs/ext2/file.c b/fs/ext2/file.c
index 0ca363d..0f257f8 100644
--- a/fs/ext2/file.c
+++ b/fs/ext2/file.c
@@ -107,27 +107,6 @@ static int ext2_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 	return ret;
 }
 
-static int ext2_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
-						pmd_t *pmd, unsigned int flags)
-{
-	struct inode *inode = file_inode(vma->vm_file);
-	struct ext2_inode_info *ei = EXT2_I(inode);
-	int ret;
-
-	if (flags & FAULT_FLAG_WRITE) {
-		sb_start_pagefault(inode->i_sb);
-		file_update_time(vma->vm_file);
-	}
-	down_read(&ei->dax_sem);
-
-	ret = dax_pmd_fault(vma, addr, pmd, flags, ext2_get_block);
-
-	up_read(&ei->dax_sem);
-	if (flags & FAULT_FLAG_WRITE)
-		sb_end_pagefault(inode->i_sb);
-	return ret;
-}
-
 static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
 		struct vm_fault *vmf)
 {
@@ -154,7 +133,11 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
 
 static const struct vm_operations_struct ext2_dax_vm_ops = {
 	.fault		= ext2_dax_fault,
-	.pmd_fault	= ext2_dax_pmd_fault,
+	/*
+	 * .pmd_fault is not supported for DAX because allocation in ext2
+	 * cannot be reliably aligned to huge page sizes and so pmd faults
+	 * will always fail and fail back to regular faults.
+	 */
 	.page_mkwrite	= ext2_dax_fault,
 	.pfn_mkwrite	= ext2_dax_pfn_mkwrite,
 };
@@ -166,7 +149,7 @@ static int ext2_file_mmap(struct file *file, struct vm_area_struct *vma)
 
 	file_accessed(file);
 	vma->vm_ops = &ext2_dax_vm_ops;
-	vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE;
+	vma->vm_flags |= VM_MIXEDMAP;
 	return 0;
 }
 #else
-- 
2.9.0

_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 04/17] ext2: remove support for DAX PMD faults
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

DAX PMD support was added via the following commit:

commit e7b1ea2ad658 ("ext2: huge page fault support")

I believe this path to be untested as ext2 doesn't reliably provide block
allocations that are aligned to 2MiB.  In my testing I've been unable to
get ext2 to actually fault in a PMD.  It always fails with a "pfn
unaligned" message because the sector returned by ext2_get_block() isn't
aligned.

I've tried various settings for the "stride" and "stripe_width" extended
options to mkfs.ext2, without any luck.

Since we can't reliably get PMDs, remove support so that we don't have an
untested code path that we may someday traverse when we happen to get an
aligned block allocation.  This should also make 4k DAX faults in ext2 a
bit faster since they will no longer have to call the PMD fault handler
only to get a response of VM_FAULT_FALLBACK.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/ext2/file.c | 29 ++++++-----------------------
 1 file changed, 6 insertions(+), 23 deletions(-)

diff --git a/fs/ext2/file.c b/fs/ext2/file.c
index 0ca363d..0f257f8 100644
--- a/fs/ext2/file.c
+++ b/fs/ext2/file.c
@@ -107,27 +107,6 @@ static int ext2_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 	return ret;
 }
 
-static int ext2_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
-						pmd_t *pmd, unsigned int flags)
-{
-	struct inode *inode = file_inode(vma->vm_file);
-	struct ext2_inode_info *ei = EXT2_I(inode);
-	int ret;
-
-	if (flags & FAULT_FLAG_WRITE) {
-		sb_start_pagefault(inode->i_sb);
-		file_update_time(vma->vm_file);
-	}
-	down_read(&ei->dax_sem);
-
-	ret = dax_pmd_fault(vma, addr, pmd, flags, ext2_get_block);
-
-	up_read(&ei->dax_sem);
-	if (flags & FAULT_FLAG_WRITE)
-		sb_end_pagefault(inode->i_sb);
-	return ret;
-}
-
 static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
 		struct vm_fault *vmf)
 {
@@ -154,7 +133,11 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
 
 static const struct vm_operations_struct ext2_dax_vm_ops = {
 	.fault		= ext2_dax_fault,
-	.pmd_fault	= ext2_dax_pmd_fault,
+	/*
+	 * .pmd_fault is not supported for DAX because allocation in ext2
+	 * cannot be reliably aligned to huge page sizes and so pmd faults
+	 * will always fail and fail back to regular faults.
+	 */
 	.page_mkwrite	= ext2_dax_fault,
 	.pfn_mkwrite	= ext2_dax_pfn_mkwrite,
 };
@@ -166,7 +149,7 @@ static int ext2_file_mmap(struct file *file, struct vm_area_struct *vma)
 
 	file_accessed(file);
 	vma->vm_ops = &ext2_dax_vm_ops;
-	vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE;
+	vma->vm_flags |= VM_MIXEDMAP;
 	return 0;
 }
 #else
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 04/17] ext2: remove support for DAX PMD faults
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

DAX PMD support was added via the following commit:

commit e7b1ea2ad658 ("ext2: huge page fault support")

I believe this path to be untested as ext2 doesn't reliably provide block
allocations that are aligned to 2MiB.  In my testing I've been unable to
get ext2 to actually fault in a PMD.  It always fails with a "pfn
unaligned" message because the sector returned by ext2_get_block() isn't
aligned.

I've tried various settings for the "stride" and "stripe_width" extended
options to mkfs.ext2, without any luck.

Since we can't reliably get PMDs, remove support so that we don't have an
untested code path that we may someday traverse when we happen to get an
aligned block allocation.  This should also make 4k DAX faults in ext2 a
bit faster since they will no longer have to call the PMD fault handler
only to get a response of VM_FAULT_FALLBACK.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/ext2/file.c | 29 ++++++-----------------------
 1 file changed, 6 insertions(+), 23 deletions(-)

diff --git a/fs/ext2/file.c b/fs/ext2/file.c
index 0ca363d..0f257f8 100644
--- a/fs/ext2/file.c
+++ b/fs/ext2/file.c
@@ -107,27 +107,6 @@ static int ext2_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 	return ret;
 }
 
-static int ext2_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
-						pmd_t *pmd, unsigned int flags)
-{
-	struct inode *inode = file_inode(vma->vm_file);
-	struct ext2_inode_info *ei = EXT2_I(inode);
-	int ret;
-
-	if (flags & FAULT_FLAG_WRITE) {
-		sb_start_pagefault(inode->i_sb);
-		file_update_time(vma->vm_file);
-	}
-	down_read(&ei->dax_sem);
-
-	ret = dax_pmd_fault(vma, addr, pmd, flags, ext2_get_block);
-
-	up_read(&ei->dax_sem);
-	if (flags & FAULT_FLAG_WRITE)
-		sb_end_pagefault(inode->i_sb);
-	return ret;
-}
-
 static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
 		struct vm_fault *vmf)
 {
@@ -154,7 +133,11 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
 
 static const struct vm_operations_struct ext2_dax_vm_ops = {
 	.fault		= ext2_dax_fault,
-	.pmd_fault	= ext2_dax_pmd_fault,
+	/*
+	 * .pmd_fault is not supported for DAX because allocation in ext2
+	 * cannot be reliably aligned to huge page sizes and so pmd faults
+	 * will always fail and fail back to regular faults.
+	 */
 	.page_mkwrite	= ext2_dax_fault,
 	.pfn_mkwrite	= ext2_dax_pfn_mkwrite,
 };
@@ -166,7 +149,7 @@ static int ext2_file_mmap(struct file *file, struct vm_area_struct *vma)
 
 	file_accessed(file);
 	vma->vm_ops = &ext2_dax_vm_ops;
-	vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE;
+	vma->vm_flags |= VM_MIXEDMAP;
 	return 0;
 }
 #else
-- 
2.9.0

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 04/17] ext2: remove support for DAX PMD faults
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel-u79uwXL29TY76Z2rM5mHXA
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner,
	linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw, Christoph Hellwig,
	linux-xfs-u79uwXL29TY76Z2rM5mHXA,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg, Andreas Dilger, Alexander Viro,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA, Jan Kara,
	linux-ext4-u79uwXL29TY76Z2rM5mHXA, Andrew Morton

DAX PMD support was added via the following commit:

commit e7b1ea2ad658 ("ext2: huge page fault support")

I believe this path to be untested as ext2 doesn't reliably provide block
allocations that are aligned to 2MiB.  In my testing I've been unable to
get ext2 to actually fault in a PMD.  It always fails with a "pfn
unaligned" message because the sector returned by ext2_get_block() isn't
aligned.

I've tried various settings for the "stride" and "stripe_width" extended
options to mkfs.ext2, without any luck.

Since we can't reliably get PMDs, remove support so that we don't have an
untested code path that we may someday traverse when we happen to get an
aligned block allocation.  This should also make 4k DAX faults in ext2 a
bit faster since they will no longer have to call the PMD fault handler
only to get a response of VM_FAULT_FALLBACK.

Signed-off-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Reviewed-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
Reviewed-by: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>
---
 fs/ext2/file.c | 29 ++++++-----------------------
 1 file changed, 6 insertions(+), 23 deletions(-)

diff --git a/fs/ext2/file.c b/fs/ext2/file.c
index 0ca363d..0f257f8 100644
--- a/fs/ext2/file.c
+++ b/fs/ext2/file.c
@@ -107,27 +107,6 @@ static int ext2_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 	return ret;
 }
 
-static int ext2_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
-						pmd_t *pmd, unsigned int flags)
-{
-	struct inode *inode = file_inode(vma->vm_file);
-	struct ext2_inode_info *ei = EXT2_I(inode);
-	int ret;
-
-	if (flags & FAULT_FLAG_WRITE) {
-		sb_start_pagefault(inode->i_sb);
-		file_update_time(vma->vm_file);
-	}
-	down_read(&ei->dax_sem);
-
-	ret = dax_pmd_fault(vma, addr, pmd, flags, ext2_get_block);
-
-	up_read(&ei->dax_sem);
-	if (flags & FAULT_FLAG_WRITE)
-		sb_end_pagefault(inode->i_sb);
-	return ret;
-}
-
 static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
 		struct vm_fault *vmf)
 {
@@ -154,7 +133,11 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
 
 static const struct vm_operations_struct ext2_dax_vm_ops = {
 	.fault		= ext2_dax_fault,
-	.pmd_fault	= ext2_dax_pmd_fault,
+	/*
+	 * .pmd_fault is not supported for DAX because allocation in ext2
+	 * cannot be reliably aligned to huge page sizes and so pmd faults
+	 * will always fail and fail back to regular faults.
+	 */
 	.page_mkwrite	= ext2_dax_fault,
 	.pfn_mkwrite	= ext2_dax_pfn_mkwrite,
 };
@@ -166,7 +149,7 @@ static int ext2_file_mmap(struct file *file, struct vm_area_struct *vma)
 
 	file_accessed(file);
 	vma->vm_ops = &ext2_dax_vm_ops;
-	vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE;
+	vma->vm_flags |= VM_MIXEDMAP;
 	return 0;
 }
 #else
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 04/17] ext2: remove support for DAX PMD faults
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

DAX PMD support was added via the following commit:

commit e7b1ea2ad658 ("ext2: huge page fault support")

I believe this path to be untested as ext2 doesn't reliably provide block
allocations that are aligned to 2MiB.  In my testing I've been unable to
get ext2 to actually fault in a PMD.  It always fails with a "pfn
unaligned" message because the sector returned by ext2_get_block() isn't
aligned.

I've tried various settings for the "stride" and "stripe_width" extended
options to mkfs.ext2, without any luck.

Since we can't reliably get PMDs, remove support so that we don't have an
untested code path that we may someday traverse when we happen to get an
aligned block allocation.  This should also make 4k DAX faults in ext2 a
bit faster since they will no longer have to call the PMD fault handler
only to get a response of VM_FAULT_FALLBACK.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/ext2/file.c | 29 ++++++-----------------------
 1 file changed, 6 insertions(+), 23 deletions(-)

diff --git a/fs/ext2/file.c b/fs/ext2/file.c
index 0ca363d..0f257f8 100644
--- a/fs/ext2/file.c
+++ b/fs/ext2/file.c
@@ -107,27 +107,6 @@ static int ext2_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 	return ret;
 }
 
-static int ext2_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
-						pmd_t *pmd, unsigned int flags)
-{
-	struct inode *inode = file_inode(vma->vm_file);
-	struct ext2_inode_info *ei = EXT2_I(inode);
-	int ret;
-
-	if (flags & FAULT_FLAG_WRITE) {
-		sb_start_pagefault(inode->i_sb);
-		file_update_time(vma->vm_file);
-	}
-	down_read(&ei->dax_sem);
-
-	ret = dax_pmd_fault(vma, addr, pmd, flags, ext2_get_block);
-
-	up_read(&ei->dax_sem);
-	if (flags & FAULT_FLAG_WRITE)
-		sb_end_pagefault(inode->i_sb);
-	return ret;
-}
-
 static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
 		struct vm_fault *vmf)
 {
@@ -154,7 +133,11 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
 
 static const struct vm_operations_struct ext2_dax_vm_ops = {
 	.fault		= ext2_dax_fault,
-	.pmd_fault	= ext2_dax_pmd_fault,
+	/*
+	 * .pmd_fault is not supported for DAX because allocation in ext2
+	 * cannot be reliably aligned to huge page sizes and so pmd faults
+	 * will always fail and fail back to regular faults.
+	 */
 	.page_mkwrite	= ext2_dax_fault,
 	.pfn_mkwrite	= ext2_dax_pfn_mkwrite,
 };
@@ -166,7 +149,7 @@ static int ext2_file_mmap(struct file *file, struct vm_area_struct *vma)
 
 	file_accessed(file);
 	vma->vm_ops = &ext2_dax_vm_ops;
-	vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE;
+	vma->vm_flags |= VM_MIXEDMAP;
 	return 0;
 }
 #else
-- 
2.9.0


^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 05/17] dax: make 'wait_table' global variable static
  2016-10-12 22:50 ` Ross Zwisler
  (?)
  (?)
@ 2016-10-12 22:50   ` Ross Zwisler
  -1 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner, linux-nvdimm,
	Christoph Hellwig, linux-xfs, linux-mm, Andreas Dilger,
	Alexander Viro, linux-fsdevel, Jan Kara, linux-ext4,
	Andrew Morton

The global 'wait_table' variable is only used within fs/dax.c, and
generates the following sparse warning:

fs/dax.c:39:19: warning: symbol 'wait_table' was not declared. Should it be static?

Make it static so it has scope local to fs/dax.c, and to make sparse happy.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/dax.c b/fs/dax.c
index 9b9be8a..ac28cdf 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -52,7 +52,7 @@
 #define DAX_WAIT_TABLE_BITS 12
 #define DAX_WAIT_TABLE_ENTRIES (1 << DAX_WAIT_TABLE_BITS)
 
-wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
+static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
 
 static int __init init_dax_wait_table(void)
 {
-- 
2.9.0

_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 05/17] dax: make 'wait_table' global variable static
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

The global 'wait_table' variable is only used within fs/dax.c, and
generates the following sparse warning:

fs/dax.c:39:19: warning: symbol 'wait_table' was not declared. Should it be static?

Make it static so it has scope local to fs/dax.c, and to make sparse happy.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/dax.c b/fs/dax.c
index 9b9be8a..ac28cdf 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -52,7 +52,7 @@
 #define DAX_WAIT_TABLE_BITS 12
 #define DAX_WAIT_TABLE_ENTRIES (1 << DAX_WAIT_TABLE_BITS)
 
-wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
+static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
 
 static int __init init_dax_wait_table(void)
 {
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 05/17] dax: make 'wait_table' global variable static
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

The global 'wait_table' variable is only used within fs/dax.c, and
generates the following sparse warning:

fs/dax.c:39:19: warning: symbol 'wait_table' was not declared. Should it be static?

Make it static so it has scope local to fs/dax.c, and to make sparse happy.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/dax.c b/fs/dax.c
index 9b9be8a..ac28cdf 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -52,7 +52,7 @@
 #define DAX_WAIT_TABLE_BITS 12
 #define DAX_WAIT_TABLE_ENTRIES (1 << DAX_WAIT_TABLE_BITS)
 
-wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
+static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
 
 static int __init init_dax_wait_table(void)
 {
-- 
2.9.0

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
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^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 05/17] dax: make 'wait_table' global variable static
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

The global 'wait_table' variable is only used within fs/dax.c, and
generates the following sparse warning:

fs/dax.c:39:19: warning: symbol 'wait_table' was not declared. Should it be static?

Make it static so it has scope local to fs/dax.c, and to make sparse happy.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/dax.c b/fs/dax.c
index 9b9be8a..ac28cdf 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -52,7 +52,7 @@
 #define DAX_WAIT_TABLE_BITS 12
 #define DAX_WAIT_TABLE_ENTRIES (1 << DAX_WAIT_TABLE_BITS)
 
-wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
+static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
 
 static int __init init_dax_wait_table(void)
 {
-- 
2.9.0


^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 06/17] dax: remove the last BUG_ON() from fs/dax.c
  2016-10-12 22:50 ` Ross Zwisler
  (?)
  (?)
@ 2016-10-12 22:50   ` Ross Zwisler
  -1 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner, linux-nvdimm,
	Christoph Hellwig, linux-xfs, linux-mm, Andreas Dilger,
	Alexander Viro, linux-fsdevel, Jan Kara, linux-ext4,
	Andrew Morton

Don't take down the kernel if we get an invalid 'from' and 'length'
argument pair.  Just warn once and return an error.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/dax.c b/fs/dax.c
index ac28cdf..98189ac 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1194,7 +1194,8 @@ int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length,
 	/* Block boundary? Nothing to do */
 	if (!length)
 		return 0;
-	BUG_ON((offset + length) > PAGE_SIZE);
+	if (WARN_ON_ONCE((offset + length) > PAGE_SIZE))
+		return -EINVAL;
 
 	memset(&bh, 0, sizeof(bh));
 	bh.b_bdev = inode->i_sb->s_bdev;
-- 
2.9.0

_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 06/17] dax: remove the last BUG_ON() from fs/dax.c
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

Don't take down the kernel if we get an invalid 'from' and 'length'
argument pair.  Just warn once and return an error.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/dax.c b/fs/dax.c
index ac28cdf..98189ac 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1194,7 +1194,8 @@ int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length,
 	/* Block boundary? Nothing to do */
 	if (!length)
 		return 0;
-	BUG_ON((offset + length) > PAGE_SIZE);
+	if (WARN_ON_ONCE((offset + length) > PAGE_SIZE))
+		return -EINVAL;
 
 	memset(&bh, 0, sizeof(bh));
 	bh.b_bdev = inode->i_sb->s_bdev;
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 06/17] dax: remove the last BUG_ON() from fs/dax.c
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

Don't take down the kernel if we get an invalid 'from' and 'length'
argument pair.  Just warn once and return an error.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/dax.c b/fs/dax.c
index ac28cdf..98189ac 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1194,7 +1194,8 @@ int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length,
 	/* Block boundary? Nothing to do */
 	if (!length)
 		return 0;
-	BUG_ON((offset + length) > PAGE_SIZE);
+	if (WARN_ON_ONCE((offset + length) > PAGE_SIZE))
+		return -EINVAL;
 
 	memset(&bh, 0, sizeof(bh));
 	bh.b_bdev = inode->i_sb->s_bdev;
-- 
2.9.0

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 06/17] dax: remove the last BUG_ON() from fs/dax.c
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

Don't take down the kernel if we get an invalid 'from' and 'length'
argument pair.  Just warn once and return an error.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/dax.c b/fs/dax.c
index ac28cdf..98189ac 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1194,7 +1194,8 @@ int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length,
 	/* Block boundary? Nothing to do */
 	if (!length)
 		return 0;
-	BUG_ON((offset + length) > PAGE_SIZE);
+	if (WARN_ON_ONCE((offset + length) > PAGE_SIZE))
+		return -EINVAL;
 
 	memset(&bh, 0, sizeof(bh));
 	bh.b_bdev = inode->i_sb->s_bdev;
-- 
2.9.0


^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 07/17] dax: consistent variable naming for DAX entries
  2016-10-12 22:50 ` Ross Zwisler
                     ` (2 preceding siblings ...)
  (?)
@ 2016-10-12 22:50   ` Ross Zwisler
  -1 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner, linux-nvdimm,
	Christoph Hellwig, linux-xfs, linux-mm, Andreas Dilger,
	Alexander Viro, linux-fsdevel, Jan Kara, linux-ext4,
	Andrew Morton

No functional change.

Consistently use the variable name 'entry' instead of 'ret' for DAX radix
tree entries.  This was already happening in most of the code, so update
get_unlocked_mapping_entry(), grab_mapping_entry() and
dax_unlock_mapping_entry().

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c | 34 +++++++++++++++++-----------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 98189ac..152a6e1 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -357,7 +357,7 @@ static inline void *unlock_slot(struct address_space *mapping, void **slot)
 static void *get_unlocked_mapping_entry(struct address_space *mapping,
 					pgoff_t index, void ***slotp)
 {
-	void *ret, **slot;
+	void *entry, **slot;
 	struct wait_exceptional_entry_queue ewait;
 	wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index);
 
@@ -367,13 +367,13 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
 	ewait.key.index = index;
 
 	for (;;) {
-		ret = __radix_tree_lookup(&mapping->page_tree, index, NULL,
+		entry = __radix_tree_lookup(&mapping->page_tree, index, NULL,
 					  &slot);
-		if (!ret || !radix_tree_exceptional_entry(ret) ||
+		if (!entry || !radix_tree_exceptional_entry(entry) ||
 		    !slot_locked(mapping, slot)) {
 			if (slotp)
 				*slotp = slot;
-			return ret;
+			return entry;
 		}
 		prepare_to_wait_exclusive(wq, &ewait.wait,
 					  TASK_UNINTERRUPTIBLE);
@@ -396,13 +396,13 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
  */
 static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index)
 {
-	void *ret, **slot;
+	void *entry, **slot;
 
 restart:
 	spin_lock_irq(&mapping->tree_lock);
-	ret = get_unlocked_mapping_entry(mapping, index, &slot);
+	entry = get_unlocked_mapping_entry(mapping, index, &slot);
 	/* No entry for given index? Make sure radix tree is big enough. */
-	if (!ret) {
+	if (!entry) {
 		int err;
 
 		spin_unlock_irq(&mapping->tree_lock);
@@ -410,10 +410,10 @@ restart:
 				mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
 		if (err)
 			return ERR_PTR(err);
-		ret = (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
+		entry = (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
 			       RADIX_DAX_ENTRY_LOCK);
 		spin_lock_irq(&mapping->tree_lock);
-		err = radix_tree_insert(&mapping->page_tree, index, ret);
+		err = radix_tree_insert(&mapping->page_tree, index, entry);
 		radix_tree_preload_end();
 		if (err) {
 			spin_unlock_irq(&mapping->tree_lock);
@@ -425,11 +425,11 @@ restart:
 		/* Good, we have inserted empty locked entry into the tree. */
 		mapping->nrexceptional++;
 		spin_unlock_irq(&mapping->tree_lock);
-		return ret;
+		return entry;
 	}
 	/* Normal page in radix tree? */
-	if (!radix_tree_exceptional_entry(ret)) {
-		struct page *page = ret;
+	if (!radix_tree_exceptional_entry(entry)) {
+		struct page *page = entry;
 
 		get_page(page);
 		spin_unlock_irq(&mapping->tree_lock);
@@ -442,9 +442,9 @@ restart:
 		}
 		return page;
 	}
-	ret = lock_slot(mapping, slot);
+	entry = lock_slot(mapping, slot);
 	spin_unlock_irq(&mapping->tree_lock);
-	return ret;
+	return entry;
 }
 
 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
@@ -469,11 +469,11 @@ void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 
 void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
 {
-	void *ret, **slot;
+	void *entry, **slot;
 
 	spin_lock_irq(&mapping->tree_lock);
-	ret = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot);
-	if (WARN_ON_ONCE(!ret || !radix_tree_exceptional_entry(ret) ||
+	entry = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot);
+	if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry) ||
 			 !slot_locked(mapping, slot))) {
 		spin_unlock_irq(&mapping->tree_lock);
 		return;
-- 
2.9.0

_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 07/17] dax: consistent variable naming for DAX entries
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

No functional change.

Consistently use the variable name 'entry' instead of 'ret' for DAX radix
tree entries.  This was already happening in most of the code, so update
get_unlocked_mapping_entry(), grab_mapping_entry() and
dax_unlock_mapping_entry().

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c | 34 +++++++++++++++++-----------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 98189ac..152a6e1 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -357,7 +357,7 @@ static inline void *unlock_slot(struct address_space *mapping, void **slot)
 static void *get_unlocked_mapping_entry(struct address_space *mapping,
 					pgoff_t index, void ***slotp)
 {
-	void *ret, **slot;
+	void *entry, **slot;
 	struct wait_exceptional_entry_queue ewait;
 	wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index);
 
@@ -367,13 +367,13 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
 	ewait.key.index = index;
 
 	for (;;) {
-		ret = __radix_tree_lookup(&mapping->page_tree, index, NULL,
+		entry = __radix_tree_lookup(&mapping->page_tree, index, NULL,
 					  &slot);
-		if (!ret || !radix_tree_exceptional_entry(ret) ||
+		if (!entry || !radix_tree_exceptional_entry(entry) ||
 		    !slot_locked(mapping, slot)) {
 			if (slotp)
 				*slotp = slot;
-			return ret;
+			return entry;
 		}
 		prepare_to_wait_exclusive(wq, &ewait.wait,
 					  TASK_UNINTERRUPTIBLE);
@@ -396,13 +396,13 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
  */
 static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index)
 {
-	void *ret, **slot;
+	void *entry, **slot;
 
 restart:
 	spin_lock_irq(&mapping->tree_lock);
-	ret = get_unlocked_mapping_entry(mapping, index, &slot);
+	entry = get_unlocked_mapping_entry(mapping, index, &slot);
 	/* No entry for given index? Make sure radix tree is big enough. */
-	if (!ret) {
+	if (!entry) {
 		int err;
 
 		spin_unlock_irq(&mapping->tree_lock);
@@ -410,10 +410,10 @@ restart:
 				mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
 		if (err)
 			return ERR_PTR(err);
-		ret = (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
+		entry = (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
 			       RADIX_DAX_ENTRY_LOCK);
 		spin_lock_irq(&mapping->tree_lock);
-		err = radix_tree_insert(&mapping->page_tree, index, ret);
+		err = radix_tree_insert(&mapping->page_tree, index, entry);
 		radix_tree_preload_end();
 		if (err) {
 			spin_unlock_irq(&mapping->tree_lock);
@@ -425,11 +425,11 @@ restart:
 		/* Good, we have inserted empty locked entry into the tree. */
 		mapping->nrexceptional++;
 		spin_unlock_irq(&mapping->tree_lock);
-		return ret;
+		return entry;
 	}
 	/* Normal page in radix tree? */
-	if (!radix_tree_exceptional_entry(ret)) {
-		struct page *page = ret;
+	if (!radix_tree_exceptional_entry(entry)) {
+		struct page *page = entry;
 
 		get_page(page);
 		spin_unlock_irq(&mapping->tree_lock);
@@ -442,9 +442,9 @@ restart:
 		}
 		return page;
 	}
-	ret = lock_slot(mapping, slot);
+	entry = lock_slot(mapping, slot);
 	spin_unlock_irq(&mapping->tree_lock);
-	return ret;
+	return entry;
 }
 
 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
@@ -469,11 +469,11 @@ void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 
 void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
 {
-	void *ret, **slot;
+	void *entry, **slot;
 
 	spin_lock_irq(&mapping->tree_lock);
-	ret = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot);
-	if (WARN_ON_ONCE(!ret || !radix_tree_exceptional_entry(ret) ||
+	entry = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot);
+	if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry) ||
 			 !slot_locked(mapping, slot))) {
 		spin_unlock_irq(&mapping->tree_lock);
 		return;
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 07/17] dax: consistent variable naming for DAX entries
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

No functional change.

Consistently use the variable name 'entry' instead of 'ret' for DAX radix
tree entries.  This was already happening in most of the code, so update
get_unlocked_mapping_entry(), grab_mapping_entry() and
dax_unlock_mapping_entry().

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c | 34 +++++++++++++++++-----------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 98189ac..152a6e1 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -357,7 +357,7 @@ static inline void *unlock_slot(struct address_space *mapping, void **slot)
 static void *get_unlocked_mapping_entry(struct address_space *mapping,
 					pgoff_t index, void ***slotp)
 {
-	void *ret, **slot;
+	void *entry, **slot;
 	struct wait_exceptional_entry_queue ewait;
 	wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index);
 
@@ -367,13 +367,13 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
 	ewait.key.index = index;
 
 	for (;;) {
-		ret = __radix_tree_lookup(&mapping->page_tree, index, NULL,
+		entry = __radix_tree_lookup(&mapping->page_tree, index, NULL,
 					  &slot);
-		if (!ret || !radix_tree_exceptional_entry(ret) ||
+		if (!entry || !radix_tree_exceptional_entry(entry) ||
 		    !slot_locked(mapping, slot)) {
 			if (slotp)
 				*slotp = slot;
-			return ret;
+			return entry;
 		}
 		prepare_to_wait_exclusive(wq, &ewait.wait,
 					  TASK_UNINTERRUPTIBLE);
@@ -396,13 +396,13 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
  */
 static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index)
 {
-	void *ret, **slot;
+	void *entry, **slot;
 
 restart:
 	spin_lock_irq(&mapping->tree_lock);
-	ret = get_unlocked_mapping_entry(mapping, index, &slot);
+	entry = get_unlocked_mapping_entry(mapping, index, &slot);
 	/* No entry for given index? Make sure radix tree is big enough. */
-	if (!ret) {
+	if (!entry) {
 		int err;
 
 		spin_unlock_irq(&mapping->tree_lock);
@@ -410,10 +410,10 @@ restart:
 				mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
 		if (err)
 			return ERR_PTR(err);
-		ret = (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
+		entry = (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
 			       RADIX_DAX_ENTRY_LOCK);
 		spin_lock_irq(&mapping->tree_lock);
-		err = radix_tree_insert(&mapping->page_tree, index, ret);
+		err = radix_tree_insert(&mapping->page_tree, index, entry);
 		radix_tree_preload_end();
 		if (err) {
 			spin_unlock_irq(&mapping->tree_lock);
@@ -425,11 +425,11 @@ restart:
 		/* Good, we have inserted empty locked entry into the tree. */
 		mapping->nrexceptional++;
 		spin_unlock_irq(&mapping->tree_lock);
-		return ret;
+		return entry;
 	}
 	/* Normal page in radix tree? */
-	if (!radix_tree_exceptional_entry(ret)) {
-		struct page *page = ret;
+	if (!radix_tree_exceptional_entry(entry)) {
+		struct page *page = entry;
 
 		get_page(page);
 		spin_unlock_irq(&mapping->tree_lock);
@@ -442,9 +442,9 @@ restart:
 		}
 		return page;
 	}
-	ret = lock_slot(mapping, slot);
+	entry = lock_slot(mapping, slot);
 	spin_unlock_irq(&mapping->tree_lock);
-	return ret;
+	return entry;
 }
 
 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
@@ -469,11 +469,11 @@ void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 
 void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
 {
-	void *ret, **slot;
+	void *entry, **slot;
 
 	spin_lock_irq(&mapping->tree_lock);
-	ret = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot);
-	if (WARN_ON_ONCE(!ret || !radix_tree_exceptional_entry(ret) ||
+	entry = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot);
+	if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry) ||
 			 !slot_locked(mapping, slot))) {
 		spin_unlock_irq(&mapping->tree_lock);
 		return;
-- 
2.9.0

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 07/17] dax: consistent variable naming for DAX entries
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel-u79uwXL29TY76Z2rM5mHXA
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner,
	linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw, Christoph Hellwig,
	linux-xfs-u79uwXL29TY76Z2rM5mHXA,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg, Andreas Dilger, Alexander Viro,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA, Jan Kara,
	linux-ext4-u79uwXL29TY76Z2rM5mHXA, Andrew Morton

No functional change.

Consistently use the variable name 'entry' instead of 'ret' for DAX radix
tree entries.  This was already happening in most of the code, so update
get_unlocked_mapping_entry(), grab_mapping_entry() and
dax_unlock_mapping_entry().

Signed-off-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Reviewed-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
Reviewed-by: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>
---
 fs/dax.c | 34 +++++++++++++++++-----------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 98189ac..152a6e1 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -357,7 +357,7 @@ static inline void *unlock_slot(struct address_space *mapping, void **slot)
 static void *get_unlocked_mapping_entry(struct address_space *mapping,
 					pgoff_t index, void ***slotp)
 {
-	void *ret, **slot;
+	void *entry, **slot;
 	struct wait_exceptional_entry_queue ewait;
 	wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index);
 
@@ -367,13 +367,13 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
 	ewait.key.index = index;
 
 	for (;;) {
-		ret = __radix_tree_lookup(&mapping->page_tree, index, NULL,
+		entry = __radix_tree_lookup(&mapping->page_tree, index, NULL,
 					  &slot);
-		if (!ret || !radix_tree_exceptional_entry(ret) ||
+		if (!entry || !radix_tree_exceptional_entry(entry) ||
 		    !slot_locked(mapping, slot)) {
 			if (slotp)
 				*slotp = slot;
-			return ret;
+			return entry;
 		}
 		prepare_to_wait_exclusive(wq, &ewait.wait,
 					  TASK_UNINTERRUPTIBLE);
@@ -396,13 +396,13 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
  */
 static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index)
 {
-	void *ret, **slot;
+	void *entry, **slot;
 
 restart:
 	spin_lock_irq(&mapping->tree_lock);
-	ret = get_unlocked_mapping_entry(mapping, index, &slot);
+	entry = get_unlocked_mapping_entry(mapping, index, &slot);
 	/* No entry for given index? Make sure radix tree is big enough. */
-	if (!ret) {
+	if (!entry) {
 		int err;
 
 		spin_unlock_irq(&mapping->tree_lock);
@@ -410,10 +410,10 @@ restart:
 				mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
 		if (err)
 			return ERR_PTR(err);
-		ret = (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
+		entry = (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
 			       RADIX_DAX_ENTRY_LOCK);
 		spin_lock_irq(&mapping->tree_lock);
-		err = radix_tree_insert(&mapping->page_tree, index, ret);
+		err = radix_tree_insert(&mapping->page_tree, index, entry);
 		radix_tree_preload_end();
 		if (err) {
 			spin_unlock_irq(&mapping->tree_lock);
@@ -425,11 +425,11 @@ restart:
 		/* Good, we have inserted empty locked entry into the tree. */
 		mapping->nrexceptional++;
 		spin_unlock_irq(&mapping->tree_lock);
-		return ret;
+		return entry;
 	}
 	/* Normal page in radix tree? */
-	if (!radix_tree_exceptional_entry(ret)) {
-		struct page *page = ret;
+	if (!radix_tree_exceptional_entry(entry)) {
+		struct page *page = entry;
 
 		get_page(page);
 		spin_unlock_irq(&mapping->tree_lock);
@@ -442,9 +442,9 @@ restart:
 		}
 		return page;
 	}
-	ret = lock_slot(mapping, slot);
+	entry = lock_slot(mapping, slot);
 	spin_unlock_irq(&mapping->tree_lock);
-	return ret;
+	return entry;
 }
 
 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
@@ -469,11 +469,11 @@ void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 
 void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
 {
-	void *ret, **slot;
+	void *entry, **slot;
 
 	spin_lock_irq(&mapping->tree_lock);
-	ret = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot);
-	if (WARN_ON_ONCE(!ret || !radix_tree_exceptional_entry(ret) ||
+	entry = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot);
+	if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry) ||
 			 !slot_locked(mapping, slot))) {
 		spin_unlock_irq(&mapping->tree_lock);
 		return;
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 07/17] dax: consistent variable naming for DAX entries
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

No functional change.

Consistently use the variable name 'entry' instead of 'ret' for DAX radix
tree entries.  This was already happening in most of the code, so update
get_unlocked_mapping_entry(), grab_mapping_entry() and
dax_unlock_mapping_entry().

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c | 34 +++++++++++++++++-----------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 98189ac..152a6e1 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -357,7 +357,7 @@ static inline void *unlock_slot(struct address_space *mapping, void **slot)
 static void *get_unlocked_mapping_entry(struct address_space *mapping,
 					pgoff_t index, void ***slotp)
 {
-	void *ret, **slot;
+	void *entry, **slot;
 	struct wait_exceptional_entry_queue ewait;
 	wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index);
 
@@ -367,13 +367,13 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
 	ewait.key.index = index;
 
 	for (;;) {
-		ret = __radix_tree_lookup(&mapping->page_tree, index, NULL,
+		entry = __radix_tree_lookup(&mapping->page_tree, index, NULL,
 					  &slot);
-		if (!ret || !radix_tree_exceptional_entry(ret) ||
+		if (!entry || !radix_tree_exceptional_entry(entry) ||
 		    !slot_locked(mapping, slot)) {
 			if (slotp)
 				*slotp = slot;
-			return ret;
+			return entry;
 		}
 		prepare_to_wait_exclusive(wq, &ewait.wait,
 					  TASK_UNINTERRUPTIBLE);
@@ -396,13 +396,13 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
  */
 static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index)
 {
-	void *ret, **slot;
+	void *entry, **slot;
 
 restart:
 	spin_lock_irq(&mapping->tree_lock);
-	ret = get_unlocked_mapping_entry(mapping, index, &slot);
+	entry = get_unlocked_mapping_entry(mapping, index, &slot);
 	/* No entry for given index? Make sure radix tree is big enough. */
-	if (!ret) {
+	if (!entry) {
 		int err;
 
 		spin_unlock_irq(&mapping->tree_lock);
@@ -410,10 +410,10 @@ restart:
 				mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
 		if (err)
 			return ERR_PTR(err);
-		ret = (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
+		entry = (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
 			       RADIX_DAX_ENTRY_LOCK);
 		spin_lock_irq(&mapping->tree_lock);
-		err = radix_tree_insert(&mapping->page_tree, index, ret);
+		err = radix_tree_insert(&mapping->page_tree, index, entry);
 		radix_tree_preload_end();
 		if (err) {
 			spin_unlock_irq(&mapping->tree_lock);
@@ -425,11 +425,11 @@ restart:
 		/* Good, we have inserted empty locked entry into the tree. */
 		mapping->nrexceptional++;
 		spin_unlock_irq(&mapping->tree_lock);
-		return ret;
+		return entry;
 	}
 	/* Normal page in radix tree? */
-	if (!radix_tree_exceptional_entry(ret)) {
-		struct page *page = ret;
+	if (!radix_tree_exceptional_entry(entry)) {
+		struct page *page = entry;
 
 		get_page(page);
 		spin_unlock_irq(&mapping->tree_lock);
@@ -442,9 +442,9 @@ restart:
 		}
 		return page;
 	}
-	ret = lock_slot(mapping, slot);
+	entry = lock_slot(mapping, slot);
 	spin_unlock_irq(&mapping->tree_lock);
-	return ret;
+	return entry;
 }
 
 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
@@ -469,11 +469,11 @@ void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 
 void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
 {
-	void *ret, **slot;
+	void *entry, **slot;
 
 	spin_lock_irq(&mapping->tree_lock);
-	ret = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot);
-	if (WARN_ON_ONCE(!ret || !radix_tree_exceptional_entry(ret) ||
+	entry = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot);
+	if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry) ||
 			 !slot_locked(mapping, slot))) {
 		spin_unlock_irq(&mapping->tree_lock);
 		return;
-- 
2.9.0


^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 08/17] dax: coordinate locking for offsets in PMD range
  2016-10-12 22:50 ` Ross Zwisler
                     ` (2 preceding siblings ...)
  (?)
@ 2016-10-12 22:50   ` Ross Zwisler
  -1 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner, linux-nvdimm,
	Christoph Hellwig, linux-xfs, linux-mm, Andreas Dilger,
	Alexander Viro, linux-fsdevel, Jan Kara, linux-ext4,
	Andrew Morton

DAX radix tree locking currently locks entries based on the unique
combination of the 'mapping' pointer and the pgoff_t 'index' for the entry.
This works for PTEs, but as we move to PMDs we will need to have all the
offsets within the range covered by the PMD to map to the same bit lock.
To accomplish this, for ranges covered by a PMD entry we will instead lock
based on the page offset of the beginning of the PMD entry.  The 'mapping'
pointer is still used in the same way.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c            | 65 +++++++++++++++++++++++++++++++++--------------------
 include/linux/dax.h |  2 +-
 mm/filemap.c        |  2 +-
 3 files changed, 43 insertions(+), 26 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 152a6e1..e103053 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -64,14 +64,6 @@ static int __init init_dax_wait_table(void)
 }
 fs_initcall(init_dax_wait_table);
 
-static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
-					      pgoff_t index)
-{
-	unsigned long hash = hash_long((unsigned long)mapping ^ index,
-				       DAX_WAIT_TABLE_BITS);
-	return wait_table + hash;
-}
-
 static long dax_map_atomic(struct block_device *bdev, struct blk_dax_ctl *dax)
 {
 	struct request_queue *q = bdev->bd_queue;
@@ -285,7 +277,7 @@ EXPORT_SYMBOL_GPL(dax_do_io);
  */
 struct exceptional_entry_key {
 	struct address_space *mapping;
-	unsigned long index;
+	pgoff_t entry_start;
 };
 
 struct wait_exceptional_entry_queue {
@@ -293,6 +285,26 @@ struct wait_exceptional_entry_queue {
 	struct exceptional_entry_key key;
 };
 
+static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
+		pgoff_t index, void *entry, struct exceptional_entry_key *key)
+{
+	unsigned long hash;
+
+	/*
+	 * If 'entry' is a PMD, align the 'index' that we use for the wait
+	 * queue to the start of that PMD.  This ensures that all offsets in
+	 * the range covered by the PMD map to the same bit lock.
+	 */
+	if (RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
+		index &= ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1);
+
+	key->mapping = mapping;
+	key->entry_start = index;
+
+	hash = hash_long((unsigned long)mapping ^ index, DAX_WAIT_TABLE_BITS);
+	return wait_table + hash;
+}
+
 static int wake_exceptional_entry_func(wait_queue_t *wait, unsigned int mode,
 				       int sync, void *keyp)
 {
@@ -301,7 +313,7 @@ static int wake_exceptional_entry_func(wait_queue_t *wait, unsigned int mode,
 		container_of(wait, struct wait_exceptional_entry_queue, wait);
 
 	if (key->mapping != ewait->key.mapping ||
-	    key->index != ewait->key.index)
+	    key->entry_start != ewait->key.entry_start)
 		return 0;
 	return autoremove_wake_function(wait, mode, sync, NULL);
 }
@@ -359,12 +371,10 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
 {
 	void *entry, **slot;
 	struct wait_exceptional_entry_queue ewait;
-	wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index);
+	wait_queue_head_t *wq;
 
 	init_wait(&ewait.wait);
 	ewait.wait.func = wake_exceptional_entry_func;
-	ewait.key.mapping = mapping;
-	ewait.key.index = index;
 
 	for (;;) {
 		entry = __radix_tree_lookup(&mapping->page_tree, index, NULL,
@@ -375,6 +385,8 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
 				*slotp = slot;
 			return entry;
 		}
+
+		wq = dax_entry_waitqueue(mapping, index, entry, &ewait.key);
 		prepare_to_wait_exclusive(wq, &ewait.wait,
 					  TASK_UNINTERRUPTIBLE);
 		spin_unlock_irq(&mapping->tree_lock);
@@ -447,10 +459,20 @@ restart:
 	return entry;
 }
 
+/*
+ * We do not necessarily hold the mapping->tree_lock when we call this
+ * function so it is possible that 'entry' is no longer a valid item in the
+ * radix tree.  This is okay, though, because all we really need to do is to
+ * find the correct waitqueue where tasks might be sleeping waiting for that
+ * old 'entry' and wake them.
+ */
 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
-				   pgoff_t index, bool wake_all)
+		pgoff_t index, void *entry, bool wake_all)
 {
-	wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index);
+	struct exceptional_entry_key key;
+	wait_queue_head_t *wq;
+
+	wq = dax_entry_waitqueue(mapping, index, entry, &key);
 
 	/*
 	 * Checking for locked entry and prepare_to_wait_exclusive() happens
@@ -458,13 +480,8 @@ void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 	 * So at this point all tasks that could have seen our entry locked
 	 * must be in the waitqueue and the following check will see them.
 	 */
-	if (waitqueue_active(wq)) {
-		struct exceptional_entry_key key;
-
-		key.mapping = mapping;
-		key.index = index;
+	if (waitqueue_active(wq))
 		__wake_up(wq, TASK_NORMAL, wake_all ? 0 : 1, &key);
-	}
 }
 
 void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
@@ -480,7 +497,7 @@ void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
 	}
 	unlock_slot(mapping, slot);
 	spin_unlock_irq(&mapping->tree_lock);
-	dax_wake_mapping_entry_waiter(mapping, index, false);
+	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
 }
 
 static void put_locked_mapping_entry(struct address_space *mapping,
@@ -505,7 +522,7 @@ static void put_unlocked_mapping_entry(struct address_space *mapping,
 		return;
 
 	/* We have to wake up next waiter for the radix tree entry lock */
-	dax_wake_mapping_entry_waiter(mapping, index, false);
+	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
 }
 
 /*
@@ -532,7 +549,7 @@ int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index)
 	radix_tree_delete(&mapping->page_tree, index);
 	mapping->nrexceptional--;
 	spin_unlock_irq(&mapping->tree_lock);
-	dax_wake_mapping_entry_waiter(mapping, index, true);
+	dax_wake_mapping_entry_waiter(mapping, index, entry, true);
 
 	return 1;
 }
diff --git a/include/linux/dax.h b/include/linux/dax.h
index add6c4b..a41a747 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -22,7 +22,7 @@ int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 int dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t);
 int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index);
 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
-				   pgoff_t index, bool wake_all);
+		pgoff_t index, void *entry, bool wake_all);
 
 #ifdef CONFIG_FS_DAX
 struct page *read_dax_sector(struct block_device *bdev, sector_t n);
diff --git a/mm/filemap.c b/mm/filemap.c
index 2f1175e..a596462 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -617,7 +617,7 @@ static int page_cache_tree_insert(struct address_space *mapping,
 			if (node)
 				workingset_node_pages_dec(node);
 			/* Wakeup waiters for exceptional entry lock */
-			dax_wake_mapping_entry_waiter(mapping, page->index,
+			dax_wake_mapping_entry_waiter(mapping, page->index, p,
 						      false);
 		}
 	}
-- 
2.9.0

_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 08/17] dax: coordinate locking for offsets in PMD range
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

DAX radix tree locking currently locks entries based on the unique
combination of the 'mapping' pointer and the pgoff_t 'index' for the entry.
This works for PTEs, but as we move to PMDs we will need to have all the
offsets within the range covered by the PMD to map to the same bit lock.
To accomplish this, for ranges covered by a PMD entry we will instead lock
based on the page offset of the beginning of the PMD entry.  The 'mapping'
pointer is still used in the same way.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c            | 65 +++++++++++++++++++++++++++++++++--------------------
 include/linux/dax.h |  2 +-
 mm/filemap.c        |  2 +-
 3 files changed, 43 insertions(+), 26 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 152a6e1..e103053 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -64,14 +64,6 @@ static int __init init_dax_wait_table(void)
 }
 fs_initcall(init_dax_wait_table);
 
-static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
-					      pgoff_t index)
-{
-	unsigned long hash = hash_long((unsigned long)mapping ^ index,
-				       DAX_WAIT_TABLE_BITS);
-	return wait_table + hash;
-}
-
 static long dax_map_atomic(struct block_device *bdev, struct blk_dax_ctl *dax)
 {
 	struct request_queue *q = bdev->bd_queue;
@@ -285,7 +277,7 @@ EXPORT_SYMBOL_GPL(dax_do_io);
  */
 struct exceptional_entry_key {
 	struct address_space *mapping;
-	unsigned long index;
+	pgoff_t entry_start;
 };
 
 struct wait_exceptional_entry_queue {
@@ -293,6 +285,26 @@ struct wait_exceptional_entry_queue {
 	struct exceptional_entry_key key;
 };
 
+static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
+		pgoff_t index, void *entry, struct exceptional_entry_key *key)
+{
+	unsigned long hash;
+
+	/*
+	 * If 'entry' is a PMD, align the 'index' that we use for the wait
+	 * queue to the start of that PMD.  This ensures that all offsets in
+	 * the range covered by the PMD map to the same bit lock.
+	 */
+	if (RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
+		index &= ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1);
+
+	key->mapping = mapping;
+	key->entry_start = index;
+
+	hash = hash_long((unsigned long)mapping ^ index, DAX_WAIT_TABLE_BITS);
+	return wait_table + hash;
+}
+
 static int wake_exceptional_entry_func(wait_queue_t *wait, unsigned int mode,
 				       int sync, void *keyp)
 {
@@ -301,7 +313,7 @@ static int wake_exceptional_entry_func(wait_queue_t *wait, unsigned int mode,
 		container_of(wait, struct wait_exceptional_entry_queue, wait);
 
 	if (key->mapping != ewait->key.mapping ||
-	    key->index != ewait->key.index)
+	    key->entry_start != ewait->key.entry_start)
 		return 0;
 	return autoremove_wake_function(wait, mode, sync, NULL);
 }
@@ -359,12 +371,10 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
 {
 	void *entry, **slot;
 	struct wait_exceptional_entry_queue ewait;
-	wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index);
+	wait_queue_head_t *wq;
 
 	init_wait(&ewait.wait);
 	ewait.wait.func = wake_exceptional_entry_func;
-	ewait.key.mapping = mapping;
-	ewait.key.index = index;
 
 	for (;;) {
 		entry = __radix_tree_lookup(&mapping->page_tree, index, NULL,
@@ -375,6 +385,8 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
 				*slotp = slot;
 			return entry;
 		}
+
+		wq = dax_entry_waitqueue(mapping, index, entry, &ewait.key);
 		prepare_to_wait_exclusive(wq, &ewait.wait,
 					  TASK_UNINTERRUPTIBLE);
 		spin_unlock_irq(&mapping->tree_lock);
@@ -447,10 +459,20 @@ restart:
 	return entry;
 }
 
+/*
+ * We do not necessarily hold the mapping->tree_lock when we call this
+ * function so it is possible that 'entry' is no longer a valid item in the
+ * radix tree.  This is okay, though, because all we really need to do is to
+ * find the correct waitqueue where tasks might be sleeping waiting for that
+ * old 'entry' and wake them.
+ */
 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
-				   pgoff_t index, bool wake_all)
+		pgoff_t index, void *entry, bool wake_all)
 {
-	wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index);
+	struct exceptional_entry_key key;
+	wait_queue_head_t *wq;
+
+	wq = dax_entry_waitqueue(mapping, index, entry, &key);
 
 	/*
 	 * Checking for locked entry and prepare_to_wait_exclusive() happens
@@ -458,13 +480,8 @@ void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 	 * So at this point all tasks that could have seen our entry locked
 	 * must be in the waitqueue and the following check will see them.
 	 */
-	if (waitqueue_active(wq)) {
-		struct exceptional_entry_key key;
-
-		key.mapping = mapping;
-		key.index = index;
+	if (waitqueue_active(wq))
 		__wake_up(wq, TASK_NORMAL, wake_all ? 0 : 1, &key);
-	}
 }
 
 void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
@@ -480,7 +497,7 @@ void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
 	}
 	unlock_slot(mapping, slot);
 	spin_unlock_irq(&mapping->tree_lock);
-	dax_wake_mapping_entry_waiter(mapping, index, false);
+	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
 }
 
 static void put_locked_mapping_entry(struct address_space *mapping,
@@ -505,7 +522,7 @@ static void put_unlocked_mapping_entry(struct address_space *mapping,
 		return;
 
 	/* We have to wake up next waiter for the radix tree entry lock */
-	dax_wake_mapping_entry_waiter(mapping, index, false);
+	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
 }
 
 /*
@@ -532,7 +549,7 @@ int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index)
 	radix_tree_delete(&mapping->page_tree, index);
 	mapping->nrexceptional--;
 	spin_unlock_irq(&mapping->tree_lock);
-	dax_wake_mapping_entry_waiter(mapping, index, true);
+	dax_wake_mapping_entry_waiter(mapping, index, entry, true);
 
 	return 1;
 }
diff --git a/include/linux/dax.h b/include/linux/dax.h
index add6c4b..a41a747 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -22,7 +22,7 @@ int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 int dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t);
 int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index);
 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
-				   pgoff_t index, bool wake_all);
+		pgoff_t index, void *entry, bool wake_all);
 
 #ifdef CONFIG_FS_DAX
 struct page *read_dax_sector(struct block_device *bdev, sector_t n);
diff --git a/mm/filemap.c b/mm/filemap.c
index 2f1175e..a596462 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -617,7 +617,7 @@ static int page_cache_tree_insert(struct address_space *mapping,
 			if (node)
 				workingset_node_pages_dec(node);
 			/* Wakeup waiters for exceptional entry lock */
-			dax_wake_mapping_entry_waiter(mapping, page->index,
+			dax_wake_mapping_entry_waiter(mapping, page->index, p,
 						      false);
 		}
 	}
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 08/17] dax: coordinate locking for offsets in PMD range
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

DAX radix tree locking currently locks entries based on the unique
combination of the 'mapping' pointer and the pgoff_t 'index' for the entry.
This works for PTEs, but as we move to PMDs we will need to have all the
offsets within the range covered by the PMD to map to the same bit lock.
To accomplish this, for ranges covered by a PMD entry we will instead lock
based on the page offset of the beginning of the PMD entry.  The 'mapping'
pointer is still used in the same way.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c            | 65 +++++++++++++++++++++++++++++++++--------------------
 include/linux/dax.h |  2 +-
 mm/filemap.c        |  2 +-
 3 files changed, 43 insertions(+), 26 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 152a6e1..e103053 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -64,14 +64,6 @@ static int __init init_dax_wait_table(void)
 }
 fs_initcall(init_dax_wait_table);
 
-static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
-					      pgoff_t index)
-{
-	unsigned long hash = hash_long((unsigned long)mapping ^ index,
-				       DAX_WAIT_TABLE_BITS);
-	return wait_table + hash;
-}
-
 static long dax_map_atomic(struct block_device *bdev, struct blk_dax_ctl *dax)
 {
 	struct request_queue *q = bdev->bd_queue;
@@ -285,7 +277,7 @@ EXPORT_SYMBOL_GPL(dax_do_io);
  */
 struct exceptional_entry_key {
 	struct address_space *mapping;
-	unsigned long index;
+	pgoff_t entry_start;
 };
 
 struct wait_exceptional_entry_queue {
@@ -293,6 +285,26 @@ struct wait_exceptional_entry_queue {
 	struct exceptional_entry_key key;
 };
 
+static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
+		pgoff_t index, void *entry, struct exceptional_entry_key *key)
+{
+	unsigned long hash;
+
+	/*
+	 * If 'entry' is a PMD, align the 'index' that we use for the wait
+	 * queue to the start of that PMD.  This ensures that all offsets in
+	 * the range covered by the PMD map to the same bit lock.
+	 */
+	if (RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
+		index &= ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1);
+
+	key->mapping = mapping;
+	key->entry_start = index;
+
+	hash = hash_long((unsigned long)mapping ^ index, DAX_WAIT_TABLE_BITS);
+	return wait_table + hash;
+}
+
 static int wake_exceptional_entry_func(wait_queue_t *wait, unsigned int mode,
 				       int sync, void *keyp)
 {
@@ -301,7 +313,7 @@ static int wake_exceptional_entry_func(wait_queue_t *wait, unsigned int mode,
 		container_of(wait, struct wait_exceptional_entry_queue, wait);
 
 	if (key->mapping != ewait->key.mapping ||
-	    key->index != ewait->key.index)
+	    key->entry_start != ewait->key.entry_start)
 		return 0;
 	return autoremove_wake_function(wait, mode, sync, NULL);
 }
@@ -359,12 +371,10 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
 {
 	void *entry, **slot;
 	struct wait_exceptional_entry_queue ewait;
-	wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index);
+	wait_queue_head_t *wq;
 
 	init_wait(&ewait.wait);
 	ewait.wait.func = wake_exceptional_entry_func;
-	ewait.key.mapping = mapping;
-	ewait.key.index = index;
 
 	for (;;) {
 		entry = __radix_tree_lookup(&mapping->page_tree, index, NULL,
@@ -375,6 +385,8 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
 				*slotp = slot;
 			return entry;
 		}
+
+		wq = dax_entry_waitqueue(mapping, index, entry, &ewait.key);
 		prepare_to_wait_exclusive(wq, &ewait.wait,
 					  TASK_UNINTERRUPTIBLE);
 		spin_unlock_irq(&mapping->tree_lock);
@@ -447,10 +459,20 @@ restart:
 	return entry;
 }
 
+/*
+ * We do not necessarily hold the mapping->tree_lock when we call this
+ * function so it is possible that 'entry' is no longer a valid item in the
+ * radix tree.  This is okay, though, because all we really need to do is to
+ * find the correct waitqueue where tasks might be sleeping waiting for that
+ * old 'entry' and wake them.
+ */
 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
-				   pgoff_t index, bool wake_all)
+		pgoff_t index, void *entry, bool wake_all)
 {
-	wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index);
+	struct exceptional_entry_key key;
+	wait_queue_head_t *wq;
+
+	wq = dax_entry_waitqueue(mapping, index, entry, &key);
 
 	/*
 	 * Checking for locked entry and prepare_to_wait_exclusive() happens
@@ -458,13 +480,8 @@ void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 	 * So at this point all tasks that could have seen our entry locked
 	 * must be in the waitqueue and the following check will see them.
 	 */
-	if (waitqueue_active(wq)) {
-		struct exceptional_entry_key key;
-
-		key.mapping = mapping;
-		key.index = index;
+	if (waitqueue_active(wq))
 		__wake_up(wq, TASK_NORMAL, wake_all ? 0 : 1, &key);
-	}
 }
 
 void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
@@ -480,7 +497,7 @@ void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
 	}
 	unlock_slot(mapping, slot);
 	spin_unlock_irq(&mapping->tree_lock);
-	dax_wake_mapping_entry_waiter(mapping, index, false);
+	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
 }
 
 static void put_locked_mapping_entry(struct address_space *mapping,
@@ -505,7 +522,7 @@ static void put_unlocked_mapping_entry(struct address_space *mapping,
 		return;
 
 	/* We have to wake up next waiter for the radix tree entry lock */
-	dax_wake_mapping_entry_waiter(mapping, index, false);
+	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
 }
 
 /*
@@ -532,7 +549,7 @@ int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index)
 	radix_tree_delete(&mapping->page_tree, index);
 	mapping->nrexceptional--;
 	spin_unlock_irq(&mapping->tree_lock);
-	dax_wake_mapping_entry_waiter(mapping, index, true);
+	dax_wake_mapping_entry_waiter(mapping, index, entry, true);
 
 	return 1;
 }
diff --git a/include/linux/dax.h b/include/linux/dax.h
index add6c4b..a41a747 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -22,7 +22,7 @@ int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 int dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t);
 int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index);
 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
-				   pgoff_t index, bool wake_all);
+		pgoff_t index, void *entry, bool wake_all);
 
 #ifdef CONFIG_FS_DAX
 struct page *read_dax_sector(struct block_device *bdev, sector_t n);
diff --git a/mm/filemap.c b/mm/filemap.c
index 2f1175e..a596462 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -617,7 +617,7 @@ static int page_cache_tree_insert(struct address_space *mapping,
 			if (node)
 				workingset_node_pages_dec(node);
 			/* Wakeup waiters for exceptional entry lock */
-			dax_wake_mapping_entry_waiter(mapping, page->index,
+			dax_wake_mapping_entry_waiter(mapping, page->index, p,
 						      false);
 		}
 	}
-- 
2.9.0

--
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^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 08/17] dax: coordinate locking for offsets in PMD range
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel-u79uwXL29TY76Z2rM5mHXA
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner,
	linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw, Christoph Hellwig,
	linux-xfs-u79uwXL29TY76Z2rM5mHXA,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg, Andreas Dilger, Alexander Viro,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA, Jan Kara,
	linux-ext4-u79uwXL29TY76Z2rM5mHXA, Andrew Morton

DAX radix tree locking currently locks entries based on the unique
combination of the 'mapping' pointer and the pgoff_t 'index' for the entry.
This works for PTEs, but as we move to PMDs we will need to have all the
offsets within the range covered by the PMD to map to the same bit lock.
To accomplish this, for ranges covered by a PMD entry we will instead lock
based on the page offset of the beginning of the PMD entry.  The 'mapping'
pointer is still used in the same way.

Signed-off-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Reviewed-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
Reviewed-by: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>
---
 fs/dax.c            | 65 +++++++++++++++++++++++++++++++++--------------------
 include/linux/dax.h |  2 +-
 mm/filemap.c        |  2 +-
 3 files changed, 43 insertions(+), 26 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 152a6e1..e103053 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -64,14 +64,6 @@ static int __init init_dax_wait_table(void)
 }
 fs_initcall(init_dax_wait_table);
 
-static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
-					      pgoff_t index)
-{
-	unsigned long hash = hash_long((unsigned long)mapping ^ index,
-				       DAX_WAIT_TABLE_BITS);
-	return wait_table + hash;
-}
-
 static long dax_map_atomic(struct block_device *bdev, struct blk_dax_ctl *dax)
 {
 	struct request_queue *q = bdev->bd_queue;
@@ -285,7 +277,7 @@ EXPORT_SYMBOL_GPL(dax_do_io);
  */
 struct exceptional_entry_key {
 	struct address_space *mapping;
-	unsigned long index;
+	pgoff_t entry_start;
 };
 
 struct wait_exceptional_entry_queue {
@@ -293,6 +285,26 @@ struct wait_exceptional_entry_queue {
 	struct exceptional_entry_key key;
 };
 
+static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
+		pgoff_t index, void *entry, struct exceptional_entry_key *key)
+{
+	unsigned long hash;
+
+	/*
+	 * If 'entry' is a PMD, align the 'index' that we use for the wait
+	 * queue to the start of that PMD.  This ensures that all offsets in
+	 * the range covered by the PMD map to the same bit lock.
+	 */
+	if (RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
+		index &= ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1);
+
+	key->mapping = mapping;
+	key->entry_start = index;
+
+	hash = hash_long((unsigned long)mapping ^ index, DAX_WAIT_TABLE_BITS);
+	return wait_table + hash;
+}
+
 static int wake_exceptional_entry_func(wait_queue_t *wait, unsigned int mode,
 				       int sync, void *keyp)
 {
@@ -301,7 +313,7 @@ static int wake_exceptional_entry_func(wait_queue_t *wait, unsigned int mode,
 		container_of(wait, struct wait_exceptional_entry_queue, wait);
 
 	if (key->mapping != ewait->key.mapping ||
-	    key->index != ewait->key.index)
+	    key->entry_start != ewait->key.entry_start)
 		return 0;
 	return autoremove_wake_function(wait, mode, sync, NULL);
 }
@@ -359,12 +371,10 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
 {
 	void *entry, **slot;
 	struct wait_exceptional_entry_queue ewait;
-	wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index);
+	wait_queue_head_t *wq;
 
 	init_wait(&ewait.wait);
 	ewait.wait.func = wake_exceptional_entry_func;
-	ewait.key.mapping = mapping;
-	ewait.key.index = index;
 
 	for (;;) {
 		entry = __radix_tree_lookup(&mapping->page_tree, index, NULL,
@@ -375,6 +385,8 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
 				*slotp = slot;
 			return entry;
 		}
+
+		wq = dax_entry_waitqueue(mapping, index, entry, &ewait.key);
 		prepare_to_wait_exclusive(wq, &ewait.wait,
 					  TASK_UNINTERRUPTIBLE);
 		spin_unlock_irq(&mapping->tree_lock);
@@ -447,10 +459,20 @@ restart:
 	return entry;
 }
 
+/*
+ * We do not necessarily hold the mapping->tree_lock when we call this
+ * function so it is possible that 'entry' is no longer a valid item in the
+ * radix tree.  This is okay, though, because all we really need to do is to
+ * find the correct waitqueue where tasks might be sleeping waiting for that
+ * old 'entry' and wake them.
+ */
 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
-				   pgoff_t index, bool wake_all)
+		pgoff_t index, void *entry, bool wake_all)
 {
-	wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index);
+	struct exceptional_entry_key key;
+	wait_queue_head_t *wq;
+
+	wq = dax_entry_waitqueue(mapping, index, entry, &key);
 
 	/*
 	 * Checking for locked entry and prepare_to_wait_exclusive() happens
@@ -458,13 +480,8 @@ void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 	 * So at this point all tasks that could have seen our entry locked
 	 * must be in the waitqueue and the following check will see them.
 	 */
-	if (waitqueue_active(wq)) {
-		struct exceptional_entry_key key;
-
-		key.mapping = mapping;
-		key.index = index;
+	if (waitqueue_active(wq))
 		__wake_up(wq, TASK_NORMAL, wake_all ? 0 : 1, &key);
-	}
 }
 
 void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
@@ -480,7 +497,7 @@ void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
 	}
 	unlock_slot(mapping, slot);
 	spin_unlock_irq(&mapping->tree_lock);
-	dax_wake_mapping_entry_waiter(mapping, index, false);
+	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
 }
 
 static void put_locked_mapping_entry(struct address_space *mapping,
@@ -505,7 +522,7 @@ static void put_unlocked_mapping_entry(struct address_space *mapping,
 		return;
 
 	/* We have to wake up next waiter for the radix tree entry lock */
-	dax_wake_mapping_entry_waiter(mapping, index, false);
+	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
 }
 
 /*
@@ -532,7 +549,7 @@ int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index)
 	radix_tree_delete(&mapping->page_tree, index);
 	mapping->nrexceptional--;
 	spin_unlock_irq(&mapping->tree_lock);
-	dax_wake_mapping_entry_waiter(mapping, index, true);
+	dax_wake_mapping_entry_waiter(mapping, index, entry, true);
 
 	return 1;
 }
diff --git a/include/linux/dax.h b/include/linux/dax.h
index add6c4b..a41a747 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -22,7 +22,7 @@ int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 int dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t);
 int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index);
 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
-				   pgoff_t index, bool wake_all);
+		pgoff_t index, void *entry, bool wake_all);
 
 #ifdef CONFIG_FS_DAX
 struct page *read_dax_sector(struct block_device *bdev, sector_t n);
diff --git a/mm/filemap.c b/mm/filemap.c
index 2f1175e..a596462 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -617,7 +617,7 @@ static int page_cache_tree_insert(struct address_space *mapping,
 			if (node)
 				workingset_node_pages_dec(node);
 			/* Wakeup waiters for exceptional entry lock */
-			dax_wake_mapping_entry_waiter(mapping, page->index,
+			dax_wake_mapping_entry_waiter(mapping, page->index, p,
 						      false);
 		}
 	}
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 08/17] dax: coordinate locking for offsets in PMD range
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

DAX radix tree locking currently locks entries based on the unique
combination of the 'mapping' pointer and the pgoff_t 'index' for the entry.
This works for PTEs, but as we move to PMDs we will need to have all the
offsets within the range covered by the PMD to map to the same bit lock.
To accomplish this, for ranges covered by a PMD entry we will instead lock
based on the page offset of the beginning of the PMD entry.  The 'mapping'
pointer is still used in the same way.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c            | 65 +++++++++++++++++++++++++++++++++--------------------
 include/linux/dax.h |  2 +-
 mm/filemap.c        |  2 +-
 3 files changed, 43 insertions(+), 26 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 152a6e1..e103053 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -64,14 +64,6 @@ static int __init init_dax_wait_table(void)
 }
 fs_initcall(init_dax_wait_table);
 
-static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
-					      pgoff_t index)
-{
-	unsigned long hash = hash_long((unsigned long)mapping ^ index,
-				       DAX_WAIT_TABLE_BITS);
-	return wait_table + hash;
-}
-
 static long dax_map_atomic(struct block_device *bdev, struct blk_dax_ctl *dax)
 {
 	struct request_queue *q = bdev->bd_queue;
@@ -285,7 +277,7 @@ EXPORT_SYMBOL_GPL(dax_do_io);
  */
 struct exceptional_entry_key {
 	struct address_space *mapping;
-	unsigned long index;
+	pgoff_t entry_start;
 };
 
 struct wait_exceptional_entry_queue {
@@ -293,6 +285,26 @@ struct wait_exceptional_entry_queue {
 	struct exceptional_entry_key key;
 };
 
+static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
+		pgoff_t index, void *entry, struct exceptional_entry_key *key)
+{
+	unsigned long hash;
+
+	/*
+	 * If 'entry' is a PMD, align the 'index' that we use for the wait
+	 * queue to the start of that PMD.  This ensures that all offsets in
+	 * the range covered by the PMD map to the same bit lock.
+	 */
+	if (RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
+		index &= ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1);
+
+	key->mapping = mapping;
+	key->entry_start = index;
+
+	hash = hash_long((unsigned long)mapping ^ index, DAX_WAIT_TABLE_BITS);
+	return wait_table + hash;
+}
+
 static int wake_exceptional_entry_func(wait_queue_t *wait, unsigned int mode,
 				       int sync, void *keyp)
 {
@@ -301,7 +313,7 @@ static int wake_exceptional_entry_func(wait_queue_t *wait, unsigned int mode,
 		container_of(wait, struct wait_exceptional_entry_queue, wait);
 
 	if (key->mapping != ewait->key.mapping ||
-	    key->index != ewait->key.index)
+	    key->entry_start != ewait->key.entry_start)
 		return 0;
 	return autoremove_wake_function(wait, mode, sync, NULL);
 }
@@ -359,12 +371,10 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
 {
 	void *entry, **slot;
 	struct wait_exceptional_entry_queue ewait;
-	wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index);
+	wait_queue_head_t *wq;
 
 	init_wait(&ewait.wait);
 	ewait.wait.func = wake_exceptional_entry_func;
-	ewait.key.mapping = mapping;
-	ewait.key.index = index;
 
 	for (;;) {
 		entry = __radix_tree_lookup(&mapping->page_tree, index, NULL,
@@ -375,6 +385,8 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
 				*slotp = slot;
 			return entry;
 		}
+
+		wq = dax_entry_waitqueue(mapping, index, entry, &ewait.key);
 		prepare_to_wait_exclusive(wq, &ewait.wait,
 					  TASK_UNINTERRUPTIBLE);
 		spin_unlock_irq(&mapping->tree_lock);
@@ -447,10 +459,20 @@ restart:
 	return entry;
 }
 
+/*
+ * We do not necessarily hold the mapping->tree_lock when we call this
+ * function so it is possible that 'entry' is no longer a valid item in the
+ * radix tree.  This is okay, though, because all we really need to do is to
+ * find the correct waitqueue where tasks might be sleeping waiting for that
+ * old 'entry' and wake them.
+ */
 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
-				   pgoff_t index, bool wake_all)
+		pgoff_t index, void *entry, bool wake_all)
 {
-	wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index);
+	struct exceptional_entry_key key;
+	wait_queue_head_t *wq;
+
+	wq = dax_entry_waitqueue(mapping, index, entry, &key);
 
 	/*
 	 * Checking for locked entry and prepare_to_wait_exclusive() happens
@@ -458,13 +480,8 @@ void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 	 * So at this point all tasks that could have seen our entry locked
 	 * must be in the waitqueue and the following check will see them.
 	 */
-	if (waitqueue_active(wq)) {
-		struct exceptional_entry_key key;
-
-		key.mapping = mapping;
-		key.index = index;
+	if (waitqueue_active(wq))
 		__wake_up(wq, TASK_NORMAL, wake_all ? 0 : 1, &key);
-	}
 }
 
 void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
@@ -480,7 +497,7 @@ void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
 	}
 	unlock_slot(mapping, slot);
 	spin_unlock_irq(&mapping->tree_lock);
-	dax_wake_mapping_entry_waiter(mapping, index, false);
+	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
 }
 
 static void put_locked_mapping_entry(struct address_space *mapping,
@@ -505,7 +522,7 @@ static void put_unlocked_mapping_entry(struct address_space *mapping,
 		return;
 
 	/* We have to wake up next waiter for the radix tree entry lock */
-	dax_wake_mapping_entry_waiter(mapping, index, false);
+	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
 }
 
 /*
@@ -532,7 +549,7 @@ int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index)
 	radix_tree_delete(&mapping->page_tree, index);
 	mapping->nrexceptional--;
 	spin_unlock_irq(&mapping->tree_lock);
-	dax_wake_mapping_entry_waiter(mapping, index, true);
+	dax_wake_mapping_entry_waiter(mapping, index, entry, true);
 
 	return 1;
 }
diff --git a/include/linux/dax.h b/include/linux/dax.h
index add6c4b..a41a747 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -22,7 +22,7 @@ int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 int dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t);
 int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index);
 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
-				   pgoff_t index, bool wake_all);
+		pgoff_t index, void *entry, bool wake_all);
 
 #ifdef CONFIG_FS_DAX
 struct page *read_dax_sector(struct block_device *bdev, sector_t n);
diff --git a/mm/filemap.c b/mm/filemap.c
index 2f1175e..a596462 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -617,7 +617,7 @@ static int page_cache_tree_insert(struct address_space *mapping,
 			if (node)
 				workingset_node_pages_dec(node);
 			/* Wakeup waiters for exceptional entry lock */
-			dax_wake_mapping_entry_waiter(mapping, page->index,
+			dax_wake_mapping_entry_waiter(mapping, page->index, p,
 						      false);
 		}
 	}
-- 
2.9.0


^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 09/17] dax: remove dax_pmd_fault()
  2016-10-12 22:50 ` Ross Zwisler
                     ` (2 preceding siblings ...)
  (?)
@ 2016-10-12 22:50   ` Ross Zwisler
  -1 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner, linux-nvdimm,
	Christoph Hellwig, linux-xfs, linux-mm, Andreas Dilger,
	Alexander Viro, linux-fsdevel, Jan Kara, linux-ext4,
	Andrew Morton

dax_pmd_fault() is the old struct buffer_head + get_block_t based 2 MiB DAX
fault handler.  This fault handler has been disabled for several kernel
releases, and support for PMDs will be reintroduced using the struct iomap
interface instead.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c            | 213 ----------------------------------------------------
 include/linux/dax.h |   6 +-
 2 files changed, 1 insertion(+), 218 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index e103053..3d0b103 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -915,219 +915,6 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 }
 EXPORT_SYMBOL_GPL(dax_fault);
 
-#if defined(CONFIG_TRANSPARENT_HUGEPAGE)
-/*
- * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
- * more often than one might expect in the below function.
- */
-#define PG_PMD_COLOUR	((PMD_SIZE >> PAGE_SHIFT) - 1)
-
-static void __dax_dbg(struct buffer_head *bh, unsigned long address,
-		const char *reason, const char *fn)
-{
-	if (bh) {
-		char bname[BDEVNAME_SIZE];
-		bdevname(bh->b_bdev, bname);
-		pr_debug("%s: %s addr: %lx dev %s state %lx start %lld "
-			"length %zd fallback: %s\n", fn, current->comm,
-			address, bname, bh->b_state, (u64)bh->b_blocknr,
-			bh->b_size, reason);
-	} else {
-		pr_debug("%s: %s addr: %lx fallback: %s\n", fn,
-			current->comm, address, reason);
-	}
-}
-
-#define dax_pmd_dbg(bh, address, reason)	__dax_dbg(bh, address, reason, "dax_pmd")
-
-/**
- * dax_pmd_fault - handle a PMD fault on a DAX file
- * @vma: The virtual memory area where the fault occurred
- * @vmf: The description of the fault
- * @get_block: The filesystem method used to translate file offsets to blocks
- *
- * When a page fault occurs, filesystems may call this helper in their
- * pmd_fault handler for DAX files.
- */
-int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
-		pmd_t *pmd, unsigned int flags, get_block_t get_block)
-{
-	struct file *file = vma->vm_file;
-	struct address_space *mapping = file->f_mapping;
-	struct inode *inode = mapping->host;
-	struct buffer_head bh;
-	unsigned blkbits = inode->i_blkbits;
-	unsigned long pmd_addr = address & PMD_MASK;
-	bool write = flags & FAULT_FLAG_WRITE;
-	struct block_device *bdev;
-	pgoff_t size, pgoff;
-	sector_t block;
-	int result = 0;
-	bool alloc = false;
-
-	/* dax pmd mappings require pfn_t_devmap() */
-	if (!IS_ENABLED(CONFIG_FS_DAX_PMD))
-		return VM_FAULT_FALLBACK;
-
-	/* Fall back to PTEs if we're going to COW */
-	if (write && !(vma->vm_flags & VM_SHARED)) {
-		split_huge_pmd(vma, pmd, address);
-		dax_pmd_dbg(NULL, address, "cow write");
-		return VM_FAULT_FALLBACK;
-	}
-	/* If the PMD would extend outside the VMA */
-	if (pmd_addr < vma->vm_start) {
-		dax_pmd_dbg(NULL, address, "vma start unaligned");
-		return VM_FAULT_FALLBACK;
-	}
-	if ((pmd_addr + PMD_SIZE) > vma->vm_end) {
-		dax_pmd_dbg(NULL, address, "vma end unaligned");
-		return VM_FAULT_FALLBACK;
-	}
-
-	pgoff = linear_page_index(vma, pmd_addr);
-	size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
-	if (pgoff >= size)
-		return VM_FAULT_SIGBUS;
-	/* If the PMD would cover blocks out of the file */
-	if ((pgoff | PG_PMD_COLOUR) >= size) {
-		dax_pmd_dbg(NULL, address,
-				"offset + huge page size > file size");
-		return VM_FAULT_FALLBACK;
-	}
-
-	memset(&bh, 0, sizeof(bh));
-	bh.b_bdev = inode->i_sb->s_bdev;
-	block = (sector_t)pgoff << (PAGE_SHIFT - blkbits);
-
-	bh.b_size = PMD_SIZE;
-
-	if (get_block(inode, block, &bh, 0) != 0)
-		return VM_FAULT_SIGBUS;
-
-	if (!buffer_mapped(&bh) && write) {
-		if (get_block(inode, block, &bh, 1) != 0)
-			return VM_FAULT_SIGBUS;
-		alloc = true;
-		WARN_ON_ONCE(buffer_unwritten(&bh) || buffer_new(&bh));
-	}
-
-	bdev = bh.b_bdev;
-
-	if (bh.b_size < PMD_SIZE) {
-		dax_pmd_dbg(&bh, address, "allocated block too small");
-		return VM_FAULT_FALLBACK;
-	}
-
-	/*
-	 * If we allocated new storage, make sure no process has any
-	 * zero pages covering this hole
-	 */
-	if (alloc) {
-		loff_t lstart = pgoff << PAGE_SHIFT;
-		loff_t lend = lstart + PMD_SIZE - 1; /* inclusive */
-
-		truncate_pagecache_range(inode, lstart, lend);
-	}
-
-	if (!write && !buffer_mapped(&bh)) {
-		spinlock_t *ptl;
-		pmd_t entry;
-		struct page *zero_page = get_huge_zero_page();
-
-		if (unlikely(!zero_page)) {
-			dax_pmd_dbg(&bh, address, "no zero page");
-			goto fallback;
-		}
-
-		ptl = pmd_lock(vma->vm_mm, pmd);
-		if (!pmd_none(*pmd)) {
-			spin_unlock(ptl);
-			dax_pmd_dbg(&bh, address, "pmd already present");
-			goto fallback;
-		}
-
-		dev_dbg(part_to_dev(bdev->bd_part),
-				"%s: %s addr: %lx pfn: <zero> sect: %llx\n",
-				__func__, current->comm, address,
-				(unsigned long long) to_sector(&bh, inode));
-
-		entry = mk_pmd(zero_page, vma->vm_page_prot);
-		entry = pmd_mkhuge(entry);
-		set_pmd_at(vma->vm_mm, pmd_addr, pmd, entry);
-		result = VM_FAULT_NOPAGE;
-		spin_unlock(ptl);
-	} else {
-		struct blk_dax_ctl dax = {
-			.sector = to_sector(&bh, inode),
-			.size = PMD_SIZE,
-		};
-		long length = dax_map_atomic(bdev, &dax);
-
-		if (length < 0) {
-			dax_pmd_dbg(&bh, address, "dax-error fallback");
-			goto fallback;
-		}
-		if (length < PMD_SIZE) {
-			dax_pmd_dbg(&bh, address, "dax-length too small");
-			dax_unmap_atomic(bdev, &dax);
-			goto fallback;
-		}
-		if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR) {
-			dax_pmd_dbg(&bh, address, "pfn unaligned");
-			dax_unmap_atomic(bdev, &dax);
-			goto fallback;
-		}
-
-		if (!pfn_t_devmap(dax.pfn)) {
-			dax_unmap_atomic(bdev, &dax);
-			dax_pmd_dbg(&bh, address, "pfn not in memmap");
-			goto fallback;
-		}
-		dax_unmap_atomic(bdev, &dax);
-
-		/*
-		 * For PTE faults we insert a radix tree entry for reads, and
-		 * leave it clean.  Then on the first write we dirty the radix
-		 * tree entry via the dax_pfn_mkwrite() path.  This sequence
-		 * allows the dax_pfn_mkwrite() call to be simpler and avoid a
-		 * call into get_block() to translate the pgoff to a sector in
-		 * order to be able to create a new radix tree entry.
-		 *
-		 * The PMD path doesn't have an equivalent to
-		 * dax_pfn_mkwrite(), though, so for a read followed by a
-		 * write we traverse all the way through dax_pmd_fault()
-		 * twice.  This means we can just skip inserting a radix tree
-		 * entry completely on the initial read and just wait until
-		 * the write to insert a dirty entry.
-		 */
-		if (write) {
-			/*
-			 * We should insert radix-tree entry and dirty it here.
-			 * For now this is broken...
-			 */
-		}
-
-		dev_dbg(part_to_dev(bdev->bd_part),
-				"%s: %s addr: %lx pfn: %lx sect: %llx\n",
-				__func__, current->comm, address,
-				pfn_t_to_pfn(dax.pfn),
-				(unsigned long long) dax.sector);
-		result |= vmf_insert_pfn_pmd(vma, address, pmd,
-				dax.pfn, write);
-	}
-
- out:
-	return result;
-
- fallback:
-	count_vm_event(THP_FAULT_FALLBACK);
-	result = VM_FAULT_FALLBACK;
-	goto out;
-}
-EXPORT_SYMBOL_GPL(dax_pmd_fault);
-#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
-
 /**
  * dax_pfn_mkwrite - handle first write to DAX page
  * @vma: The virtual memory area where the fault occurred
diff --git a/include/linux/dax.h b/include/linux/dax.h
index a41a747..0f74866 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -48,16 +48,12 @@ static inline int __dax_zero_page_range(struct block_device *bdev,
 }
 #endif
 
-#if defined(CONFIG_TRANSPARENT_HUGEPAGE)
-int dax_pmd_fault(struct vm_area_struct *, unsigned long addr, pmd_t *,
-				unsigned int flags, get_block_t);
-#else
 static inline int dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
 				pmd_t *pmd, unsigned int flags, get_block_t gb)
 {
 	return VM_FAULT_FALLBACK;
 }
-#endif
+
 int dax_pfn_mkwrite(struct vm_area_struct *, struct vm_fault *);
 #define dax_mkwrite(vma, vmf, gb)	dax_fault(vma, vmf, gb)
 
-- 
2.9.0

_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 09/17] dax: remove dax_pmd_fault()
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

dax_pmd_fault() is the old struct buffer_head + get_block_t based 2 MiB DAX
fault handler.  This fault handler has been disabled for several kernel
releases, and support for PMDs will be reintroduced using the struct iomap
interface instead.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c            | 213 ----------------------------------------------------
 include/linux/dax.h |   6 +-
 2 files changed, 1 insertion(+), 218 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index e103053..3d0b103 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -915,219 +915,6 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 }
 EXPORT_SYMBOL_GPL(dax_fault);
 
-#if defined(CONFIG_TRANSPARENT_HUGEPAGE)
-/*
- * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
- * more often than one might expect in the below function.
- */
-#define PG_PMD_COLOUR	((PMD_SIZE >> PAGE_SHIFT) - 1)
-
-static void __dax_dbg(struct buffer_head *bh, unsigned long address,
-		const char *reason, const char *fn)
-{
-	if (bh) {
-		char bname[BDEVNAME_SIZE];
-		bdevname(bh->b_bdev, bname);
-		pr_debug("%s: %s addr: %lx dev %s state %lx start %lld "
-			"length %zd fallback: %s\n", fn, current->comm,
-			address, bname, bh->b_state, (u64)bh->b_blocknr,
-			bh->b_size, reason);
-	} else {
-		pr_debug("%s: %s addr: %lx fallback: %s\n", fn,
-			current->comm, address, reason);
-	}
-}
-
-#define dax_pmd_dbg(bh, address, reason)	__dax_dbg(bh, address, reason, "dax_pmd")
-
-/**
- * dax_pmd_fault - handle a PMD fault on a DAX file
- * @vma: The virtual memory area where the fault occurred
- * @vmf: The description of the fault
- * @get_block: The filesystem method used to translate file offsets to blocks
- *
- * When a page fault occurs, filesystems may call this helper in their
- * pmd_fault handler for DAX files.
- */
-int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
-		pmd_t *pmd, unsigned int flags, get_block_t get_block)
-{
-	struct file *file = vma->vm_file;
-	struct address_space *mapping = file->f_mapping;
-	struct inode *inode = mapping->host;
-	struct buffer_head bh;
-	unsigned blkbits = inode->i_blkbits;
-	unsigned long pmd_addr = address & PMD_MASK;
-	bool write = flags & FAULT_FLAG_WRITE;
-	struct block_device *bdev;
-	pgoff_t size, pgoff;
-	sector_t block;
-	int result = 0;
-	bool alloc = false;
-
-	/* dax pmd mappings require pfn_t_devmap() */
-	if (!IS_ENABLED(CONFIG_FS_DAX_PMD))
-		return VM_FAULT_FALLBACK;
-
-	/* Fall back to PTEs if we're going to COW */
-	if (write && !(vma->vm_flags & VM_SHARED)) {
-		split_huge_pmd(vma, pmd, address);
-		dax_pmd_dbg(NULL, address, "cow write");
-		return VM_FAULT_FALLBACK;
-	}
-	/* If the PMD would extend outside the VMA */
-	if (pmd_addr < vma->vm_start) {
-		dax_pmd_dbg(NULL, address, "vma start unaligned");
-		return VM_FAULT_FALLBACK;
-	}
-	if ((pmd_addr + PMD_SIZE) > vma->vm_end) {
-		dax_pmd_dbg(NULL, address, "vma end unaligned");
-		return VM_FAULT_FALLBACK;
-	}
-
-	pgoff = linear_page_index(vma, pmd_addr);
-	size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
-	if (pgoff >= size)
-		return VM_FAULT_SIGBUS;
-	/* If the PMD would cover blocks out of the file */
-	if ((pgoff | PG_PMD_COLOUR) >= size) {
-		dax_pmd_dbg(NULL, address,
-				"offset + huge page size > file size");
-		return VM_FAULT_FALLBACK;
-	}
-
-	memset(&bh, 0, sizeof(bh));
-	bh.b_bdev = inode->i_sb->s_bdev;
-	block = (sector_t)pgoff << (PAGE_SHIFT - blkbits);
-
-	bh.b_size = PMD_SIZE;
-
-	if (get_block(inode, block, &bh, 0) != 0)
-		return VM_FAULT_SIGBUS;
-
-	if (!buffer_mapped(&bh) && write) {
-		if (get_block(inode, block, &bh, 1) != 0)
-			return VM_FAULT_SIGBUS;
-		alloc = true;
-		WARN_ON_ONCE(buffer_unwritten(&bh) || buffer_new(&bh));
-	}
-
-	bdev = bh.b_bdev;
-
-	if (bh.b_size < PMD_SIZE) {
-		dax_pmd_dbg(&bh, address, "allocated block too small");
-		return VM_FAULT_FALLBACK;
-	}
-
-	/*
-	 * If we allocated new storage, make sure no process has any
-	 * zero pages covering this hole
-	 */
-	if (alloc) {
-		loff_t lstart = pgoff << PAGE_SHIFT;
-		loff_t lend = lstart + PMD_SIZE - 1; /* inclusive */
-
-		truncate_pagecache_range(inode, lstart, lend);
-	}
-
-	if (!write && !buffer_mapped(&bh)) {
-		spinlock_t *ptl;
-		pmd_t entry;
-		struct page *zero_page = get_huge_zero_page();
-
-		if (unlikely(!zero_page)) {
-			dax_pmd_dbg(&bh, address, "no zero page");
-			goto fallback;
-		}
-
-		ptl = pmd_lock(vma->vm_mm, pmd);
-		if (!pmd_none(*pmd)) {
-			spin_unlock(ptl);
-			dax_pmd_dbg(&bh, address, "pmd already present");
-			goto fallback;
-		}
-
-		dev_dbg(part_to_dev(bdev->bd_part),
-				"%s: %s addr: %lx pfn: <zero> sect: %llx\n",
-				__func__, current->comm, address,
-				(unsigned long long) to_sector(&bh, inode));
-
-		entry = mk_pmd(zero_page, vma->vm_page_prot);
-		entry = pmd_mkhuge(entry);
-		set_pmd_at(vma->vm_mm, pmd_addr, pmd, entry);
-		result = VM_FAULT_NOPAGE;
-		spin_unlock(ptl);
-	} else {
-		struct blk_dax_ctl dax = {
-			.sector = to_sector(&bh, inode),
-			.size = PMD_SIZE,
-		};
-		long length = dax_map_atomic(bdev, &dax);
-
-		if (length < 0) {
-			dax_pmd_dbg(&bh, address, "dax-error fallback");
-			goto fallback;
-		}
-		if (length < PMD_SIZE) {
-			dax_pmd_dbg(&bh, address, "dax-length too small");
-			dax_unmap_atomic(bdev, &dax);
-			goto fallback;
-		}
-		if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR) {
-			dax_pmd_dbg(&bh, address, "pfn unaligned");
-			dax_unmap_atomic(bdev, &dax);
-			goto fallback;
-		}
-
-		if (!pfn_t_devmap(dax.pfn)) {
-			dax_unmap_atomic(bdev, &dax);
-			dax_pmd_dbg(&bh, address, "pfn not in memmap");
-			goto fallback;
-		}
-		dax_unmap_atomic(bdev, &dax);
-
-		/*
-		 * For PTE faults we insert a radix tree entry for reads, and
-		 * leave it clean.  Then on the first write we dirty the radix
-		 * tree entry via the dax_pfn_mkwrite() path.  This sequence
-		 * allows the dax_pfn_mkwrite() call to be simpler and avoid a
-		 * call into get_block() to translate the pgoff to a sector in
-		 * order to be able to create a new radix tree entry.
-		 *
-		 * The PMD path doesn't have an equivalent to
-		 * dax_pfn_mkwrite(), though, so for a read followed by a
-		 * write we traverse all the way through dax_pmd_fault()
-		 * twice.  This means we can just skip inserting a radix tree
-		 * entry completely on the initial read and just wait until
-		 * the write to insert a dirty entry.
-		 */
-		if (write) {
-			/*
-			 * We should insert radix-tree entry and dirty it here.
-			 * For now this is broken...
-			 */
-		}
-
-		dev_dbg(part_to_dev(bdev->bd_part),
-				"%s: %s addr: %lx pfn: %lx sect: %llx\n",
-				__func__, current->comm, address,
-				pfn_t_to_pfn(dax.pfn),
-				(unsigned long long) dax.sector);
-		result |= vmf_insert_pfn_pmd(vma, address, pmd,
-				dax.pfn, write);
-	}
-
- out:
-	return result;
-
- fallback:
-	count_vm_event(THP_FAULT_FALLBACK);
-	result = VM_FAULT_FALLBACK;
-	goto out;
-}
-EXPORT_SYMBOL_GPL(dax_pmd_fault);
-#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
-
 /**
  * dax_pfn_mkwrite - handle first write to DAX page
  * @vma: The virtual memory area where the fault occurred
diff --git a/include/linux/dax.h b/include/linux/dax.h
index a41a747..0f74866 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -48,16 +48,12 @@ static inline int __dax_zero_page_range(struct block_device *bdev,
 }
 #endif
 
-#if defined(CONFIG_TRANSPARENT_HUGEPAGE)
-int dax_pmd_fault(struct vm_area_struct *, unsigned long addr, pmd_t *,
-				unsigned int flags, get_block_t);
-#else
 static inline int dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
 				pmd_t *pmd, unsigned int flags, get_block_t gb)
 {
 	return VM_FAULT_FALLBACK;
 }
-#endif
+
 int dax_pfn_mkwrite(struct vm_area_struct *, struct vm_fault *);
 #define dax_mkwrite(vma, vmf, gb)	dax_fault(vma, vmf, gb)
 
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 09/17] dax: remove dax_pmd_fault()
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

dax_pmd_fault() is the old struct buffer_head + get_block_t based 2 MiB DAX
fault handler.  This fault handler has been disabled for several kernel
releases, and support for PMDs will be reintroduced using the struct iomap
interface instead.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c            | 213 ----------------------------------------------------
 include/linux/dax.h |   6 +-
 2 files changed, 1 insertion(+), 218 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index e103053..3d0b103 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -915,219 +915,6 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 }
 EXPORT_SYMBOL_GPL(dax_fault);
 
-#if defined(CONFIG_TRANSPARENT_HUGEPAGE)
-/*
- * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
- * more often than one might expect in the below function.
- */
-#define PG_PMD_COLOUR	((PMD_SIZE >> PAGE_SHIFT) - 1)
-
-static void __dax_dbg(struct buffer_head *bh, unsigned long address,
-		const char *reason, const char *fn)
-{
-	if (bh) {
-		char bname[BDEVNAME_SIZE];
-		bdevname(bh->b_bdev, bname);
-		pr_debug("%s: %s addr: %lx dev %s state %lx start %lld "
-			"length %zd fallback: %s\n", fn, current->comm,
-			address, bname, bh->b_state, (u64)bh->b_blocknr,
-			bh->b_size, reason);
-	} else {
-		pr_debug("%s: %s addr: %lx fallback: %s\n", fn,
-			current->comm, address, reason);
-	}
-}
-
-#define dax_pmd_dbg(bh, address, reason)	__dax_dbg(bh, address, reason, "dax_pmd")
-
-/**
- * dax_pmd_fault - handle a PMD fault on a DAX file
- * @vma: The virtual memory area where the fault occurred
- * @vmf: The description of the fault
- * @get_block: The filesystem method used to translate file offsets to blocks
- *
- * When a page fault occurs, filesystems may call this helper in their
- * pmd_fault handler for DAX files.
- */
-int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
-		pmd_t *pmd, unsigned int flags, get_block_t get_block)
-{
-	struct file *file = vma->vm_file;
-	struct address_space *mapping = file->f_mapping;
-	struct inode *inode = mapping->host;
-	struct buffer_head bh;
-	unsigned blkbits = inode->i_blkbits;
-	unsigned long pmd_addr = address & PMD_MASK;
-	bool write = flags & FAULT_FLAG_WRITE;
-	struct block_device *bdev;
-	pgoff_t size, pgoff;
-	sector_t block;
-	int result = 0;
-	bool alloc = false;
-
-	/* dax pmd mappings require pfn_t_devmap() */
-	if (!IS_ENABLED(CONFIG_FS_DAX_PMD))
-		return VM_FAULT_FALLBACK;
-
-	/* Fall back to PTEs if we're going to COW */
-	if (write && !(vma->vm_flags & VM_SHARED)) {
-		split_huge_pmd(vma, pmd, address);
-		dax_pmd_dbg(NULL, address, "cow write");
-		return VM_FAULT_FALLBACK;
-	}
-	/* If the PMD would extend outside the VMA */
-	if (pmd_addr < vma->vm_start) {
-		dax_pmd_dbg(NULL, address, "vma start unaligned");
-		return VM_FAULT_FALLBACK;
-	}
-	if ((pmd_addr + PMD_SIZE) > vma->vm_end) {
-		dax_pmd_dbg(NULL, address, "vma end unaligned");
-		return VM_FAULT_FALLBACK;
-	}
-
-	pgoff = linear_page_index(vma, pmd_addr);
-	size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
-	if (pgoff >= size)
-		return VM_FAULT_SIGBUS;
-	/* If the PMD would cover blocks out of the file */
-	if ((pgoff | PG_PMD_COLOUR) >= size) {
-		dax_pmd_dbg(NULL, address,
-				"offset + huge page size > file size");
-		return VM_FAULT_FALLBACK;
-	}
-
-	memset(&bh, 0, sizeof(bh));
-	bh.b_bdev = inode->i_sb->s_bdev;
-	block = (sector_t)pgoff << (PAGE_SHIFT - blkbits);
-
-	bh.b_size = PMD_SIZE;
-
-	if (get_block(inode, block, &bh, 0) != 0)
-		return VM_FAULT_SIGBUS;
-
-	if (!buffer_mapped(&bh) && write) {
-		if (get_block(inode, block, &bh, 1) != 0)
-			return VM_FAULT_SIGBUS;
-		alloc = true;
-		WARN_ON_ONCE(buffer_unwritten(&bh) || buffer_new(&bh));
-	}
-
-	bdev = bh.b_bdev;
-
-	if (bh.b_size < PMD_SIZE) {
-		dax_pmd_dbg(&bh, address, "allocated block too small");
-		return VM_FAULT_FALLBACK;
-	}
-
-	/*
-	 * If we allocated new storage, make sure no process has any
-	 * zero pages covering this hole
-	 */
-	if (alloc) {
-		loff_t lstart = pgoff << PAGE_SHIFT;
-		loff_t lend = lstart + PMD_SIZE - 1; /* inclusive */
-
-		truncate_pagecache_range(inode, lstart, lend);
-	}
-
-	if (!write && !buffer_mapped(&bh)) {
-		spinlock_t *ptl;
-		pmd_t entry;
-		struct page *zero_page = get_huge_zero_page();
-
-		if (unlikely(!zero_page)) {
-			dax_pmd_dbg(&bh, address, "no zero page");
-			goto fallback;
-		}
-
-		ptl = pmd_lock(vma->vm_mm, pmd);
-		if (!pmd_none(*pmd)) {
-			spin_unlock(ptl);
-			dax_pmd_dbg(&bh, address, "pmd already present");
-			goto fallback;
-		}
-
-		dev_dbg(part_to_dev(bdev->bd_part),
-				"%s: %s addr: %lx pfn: <zero> sect: %llx\n",
-				__func__, current->comm, address,
-				(unsigned long long) to_sector(&bh, inode));
-
-		entry = mk_pmd(zero_page, vma->vm_page_prot);
-		entry = pmd_mkhuge(entry);
-		set_pmd_at(vma->vm_mm, pmd_addr, pmd, entry);
-		result = VM_FAULT_NOPAGE;
-		spin_unlock(ptl);
-	} else {
-		struct blk_dax_ctl dax = {
-			.sector = to_sector(&bh, inode),
-			.size = PMD_SIZE,
-		};
-		long length = dax_map_atomic(bdev, &dax);
-
-		if (length < 0) {
-			dax_pmd_dbg(&bh, address, "dax-error fallback");
-			goto fallback;
-		}
-		if (length < PMD_SIZE) {
-			dax_pmd_dbg(&bh, address, "dax-length too small");
-			dax_unmap_atomic(bdev, &dax);
-			goto fallback;
-		}
-		if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR) {
-			dax_pmd_dbg(&bh, address, "pfn unaligned");
-			dax_unmap_atomic(bdev, &dax);
-			goto fallback;
-		}
-
-		if (!pfn_t_devmap(dax.pfn)) {
-			dax_unmap_atomic(bdev, &dax);
-			dax_pmd_dbg(&bh, address, "pfn not in memmap");
-			goto fallback;
-		}
-		dax_unmap_atomic(bdev, &dax);
-
-		/*
-		 * For PTE faults we insert a radix tree entry for reads, and
-		 * leave it clean.  Then on the first write we dirty the radix
-		 * tree entry via the dax_pfn_mkwrite() path.  This sequence
-		 * allows the dax_pfn_mkwrite() call to be simpler and avoid a
-		 * call into get_block() to translate the pgoff to a sector in
-		 * order to be able to create a new radix tree entry.
-		 *
-		 * The PMD path doesn't have an equivalent to
-		 * dax_pfn_mkwrite(), though, so for a read followed by a
-		 * write we traverse all the way through dax_pmd_fault()
-		 * twice.  This means we can just skip inserting a radix tree
-		 * entry completely on the initial read and just wait until
-		 * the write to insert a dirty entry.
-		 */
-		if (write) {
-			/*
-			 * We should insert radix-tree entry and dirty it here.
-			 * For now this is broken...
-			 */
-		}
-
-		dev_dbg(part_to_dev(bdev->bd_part),
-				"%s: %s addr: %lx pfn: %lx sect: %llx\n",
-				__func__, current->comm, address,
-				pfn_t_to_pfn(dax.pfn),
-				(unsigned long long) dax.sector);
-		result |= vmf_insert_pfn_pmd(vma, address, pmd,
-				dax.pfn, write);
-	}
-
- out:
-	return result;
-
- fallback:
-	count_vm_event(THP_FAULT_FALLBACK);
-	result = VM_FAULT_FALLBACK;
-	goto out;
-}
-EXPORT_SYMBOL_GPL(dax_pmd_fault);
-#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
-
 /**
  * dax_pfn_mkwrite - handle first write to DAX page
  * @vma: The virtual memory area where the fault occurred
diff --git a/include/linux/dax.h b/include/linux/dax.h
index a41a747..0f74866 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -48,16 +48,12 @@ static inline int __dax_zero_page_range(struct block_device *bdev,
 }
 #endif
 
-#if defined(CONFIG_TRANSPARENT_HUGEPAGE)
-int dax_pmd_fault(struct vm_area_struct *, unsigned long addr, pmd_t *,
-				unsigned int flags, get_block_t);
-#else
 static inline int dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
 				pmd_t *pmd, unsigned int flags, get_block_t gb)
 {
 	return VM_FAULT_FALLBACK;
 }
-#endif
+
 int dax_pfn_mkwrite(struct vm_area_struct *, struct vm_fault *);
 #define dax_mkwrite(vma, vmf, gb)	dax_fault(vma, vmf, gb)
 
-- 
2.9.0

--
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^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 09/17] dax: remove dax_pmd_fault()
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel-u79uwXL29TY76Z2rM5mHXA
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner,
	linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw, Christoph Hellwig,
	linux-xfs-u79uwXL29TY76Z2rM5mHXA,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg, Andreas Dilger, Alexander Viro,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA, Jan Kara,
	linux-ext4-u79uwXL29TY76Z2rM5mHXA, Andrew Morton

dax_pmd_fault() is the old struct buffer_head + get_block_t based 2 MiB DAX
fault handler.  This fault handler has been disabled for several kernel
releases, and support for PMDs will be reintroduced using the struct iomap
interface instead.

Signed-off-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Reviewed-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
Reviewed-by: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>
---
 fs/dax.c            | 213 ----------------------------------------------------
 include/linux/dax.h |   6 +-
 2 files changed, 1 insertion(+), 218 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index e103053..3d0b103 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -915,219 +915,6 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 }
 EXPORT_SYMBOL_GPL(dax_fault);
 
-#if defined(CONFIG_TRANSPARENT_HUGEPAGE)
-/*
- * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
- * more often than one might expect in the below function.
- */
-#define PG_PMD_COLOUR	((PMD_SIZE >> PAGE_SHIFT) - 1)
-
-static void __dax_dbg(struct buffer_head *bh, unsigned long address,
-		const char *reason, const char *fn)
-{
-	if (bh) {
-		char bname[BDEVNAME_SIZE];
-		bdevname(bh->b_bdev, bname);
-		pr_debug("%s: %s addr: %lx dev %s state %lx start %lld "
-			"length %zd fallback: %s\n", fn, current->comm,
-			address, bname, bh->b_state, (u64)bh->b_blocknr,
-			bh->b_size, reason);
-	} else {
-		pr_debug("%s: %s addr: %lx fallback: %s\n", fn,
-			current->comm, address, reason);
-	}
-}
-
-#define dax_pmd_dbg(bh, address, reason)	__dax_dbg(bh, address, reason, "dax_pmd")
-
-/**
- * dax_pmd_fault - handle a PMD fault on a DAX file
- * @vma: The virtual memory area where the fault occurred
- * @vmf: The description of the fault
- * @get_block: The filesystem method used to translate file offsets to blocks
- *
- * When a page fault occurs, filesystems may call this helper in their
- * pmd_fault handler for DAX files.
- */
-int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
-		pmd_t *pmd, unsigned int flags, get_block_t get_block)
-{
-	struct file *file = vma->vm_file;
-	struct address_space *mapping = file->f_mapping;
-	struct inode *inode = mapping->host;
-	struct buffer_head bh;
-	unsigned blkbits = inode->i_blkbits;
-	unsigned long pmd_addr = address & PMD_MASK;
-	bool write = flags & FAULT_FLAG_WRITE;
-	struct block_device *bdev;
-	pgoff_t size, pgoff;
-	sector_t block;
-	int result = 0;
-	bool alloc = false;
-
-	/* dax pmd mappings require pfn_t_devmap() */
-	if (!IS_ENABLED(CONFIG_FS_DAX_PMD))
-		return VM_FAULT_FALLBACK;
-
-	/* Fall back to PTEs if we're going to COW */
-	if (write && !(vma->vm_flags & VM_SHARED)) {
-		split_huge_pmd(vma, pmd, address);
-		dax_pmd_dbg(NULL, address, "cow write");
-		return VM_FAULT_FALLBACK;
-	}
-	/* If the PMD would extend outside the VMA */
-	if (pmd_addr < vma->vm_start) {
-		dax_pmd_dbg(NULL, address, "vma start unaligned");
-		return VM_FAULT_FALLBACK;
-	}
-	if ((pmd_addr + PMD_SIZE) > vma->vm_end) {
-		dax_pmd_dbg(NULL, address, "vma end unaligned");
-		return VM_FAULT_FALLBACK;
-	}
-
-	pgoff = linear_page_index(vma, pmd_addr);
-	size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
-	if (pgoff >= size)
-		return VM_FAULT_SIGBUS;
-	/* If the PMD would cover blocks out of the file */
-	if ((pgoff | PG_PMD_COLOUR) >= size) {
-		dax_pmd_dbg(NULL, address,
-				"offset + huge page size > file size");
-		return VM_FAULT_FALLBACK;
-	}
-
-	memset(&bh, 0, sizeof(bh));
-	bh.b_bdev = inode->i_sb->s_bdev;
-	block = (sector_t)pgoff << (PAGE_SHIFT - blkbits);
-
-	bh.b_size = PMD_SIZE;
-
-	if (get_block(inode, block, &bh, 0) != 0)
-		return VM_FAULT_SIGBUS;
-
-	if (!buffer_mapped(&bh) && write) {
-		if (get_block(inode, block, &bh, 1) != 0)
-			return VM_FAULT_SIGBUS;
-		alloc = true;
-		WARN_ON_ONCE(buffer_unwritten(&bh) || buffer_new(&bh));
-	}
-
-	bdev = bh.b_bdev;
-
-	if (bh.b_size < PMD_SIZE) {
-		dax_pmd_dbg(&bh, address, "allocated block too small");
-		return VM_FAULT_FALLBACK;
-	}
-
-	/*
-	 * If we allocated new storage, make sure no process has any
-	 * zero pages covering this hole
-	 */
-	if (alloc) {
-		loff_t lstart = pgoff << PAGE_SHIFT;
-		loff_t lend = lstart + PMD_SIZE - 1; /* inclusive */
-
-		truncate_pagecache_range(inode, lstart, lend);
-	}
-
-	if (!write && !buffer_mapped(&bh)) {
-		spinlock_t *ptl;
-		pmd_t entry;
-		struct page *zero_page = get_huge_zero_page();
-
-		if (unlikely(!zero_page)) {
-			dax_pmd_dbg(&bh, address, "no zero page");
-			goto fallback;
-		}
-
-		ptl = pmd_lock(vma->vm_mm, pmd);
-		if (!pmd_none(*pmd)) {
-			spin_unlock(ptl);
-			dax_pmd_dbg(&bh, address, "pmd already present");
-			goto fallback;
-		}
-
-		dev_dbg(part_to_dev(bdev->bd_part),
-				"%s: %s addr: %lx pfn: <zero> sect: %llx\n",
-				__func__, current->comm, address,
-				(unsigned long long) to_sector(&bh, inode));
-
-		entry = mk_pmd(zero_page, vma->vm_page_prot);
-		entry = pmd_mkhuge(entry);
-		set_pmd_at(vma->vm_mm, pmd_addr, pmd, entry);
-		result = VM_FAULT_NOPAGE;
-		spin_unlock(ptl);
-	} else {
-		struct blk_dax_ctl dax = {
-			.sector = to_sector(&bh, inode),
-			.size = PMD_SIZE,
-		};
-		long length = dax_map_atomic(bdev, &dax);
-
-		if (length < 0) {
-			dax_pmd_dbg(&bh, address, "dax-error fallback");
-			goto fallback;
-		}
-		if (length < PMD_SIZE) {
-			dax_pmd_dbg(&bh, address, "dax-length too small");
-			dax_unmap_atomic(bdev, &dax);
-			goto fallback;
-		}
-		if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR) {
-			dax_pmd_dbg(&bh, address, "pfn unaligned");
-			dax_unmap_atomic(bdev, &dax);
-			goto fallback;
-		}
-
-		if (!pfn_t_devmap(dax.pfn)) {
-			dax_unmap_atomic(bdev, &dax);
-			dax_pmd_dbg(&bh, address, "pfn not in memmap");
-			goto fallback;
-		}
-		dax_unmap_atomic(bdev, &dax);
-
-		/*
-		 * For PTE faults we insert a radix tree entry for reads, and
-		 * leave it clean.  Then on the first write we dirty the radix
-		 * tree entry via the dax_pfn_mkwrite() path.  This sequence
-		 * allows the dax_pfn_mkwrite() call to be simpler and avoid a
-		 * call into get_block() to translate the pgoff to a sector in
-		 * order to be able to create a new radix tree entry.
-		 *
-		 * The PMD path doesn't have an equivalent to
-		 * dax_pfn_mkwrite(), though, so for a read followed by a
-		 * write we traverse all the way through dax_pmd_fault()
-		 * twice.  This means we can just skip inserting a radix tree
-		 * entry completely on the initial read and just wait until
-		 * the write to insert a dirty entry.
-		 */
-		if (write) {
-			/*
-			 * We should insert radix-tree entry and dirty it here.
-			 * For now this is broken...
-			 */
-		}
-
-		dev_dbg(part_to_dev(bdev->bd_part),
-				"%s: %s addr: %lx pfn: %lx sect: %llx\n",
-				__func__, current->comm, address,
-				pfn_t_to_pfn(dax.pfn),
-				(unsigned long long) dax.sector);
-		result |= vmf_insert_pfn_pmd(vma, address, pmd,
-				dax.pfn, write);
-	}
-
- out:
-	return result;
-
- fallback:
-	count_vm_event(THP_FAULT_FALLBACK);
-	result = VM_FAULT_FALLBACK;
-	goto out;
-}
-EXPORT_SYMBOL_GPL(dax_pmd_fault);
-#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
-
 /**
  * dax_pfn_mkwrite - handle first write to DAX page
  * @vma: The virtual memory area where the fault occurred
diff --git a/include/linux/dax.h b/include/linux/dax.h
index a41a747..0f74866 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -48,16 +48,12 @@ static inline int __dax_zero_page_range(struct block_device *bdev,
 }
 #endif
 
-#if defined(CONFIG_TRANSPARENT_HUGEPAGE)
-int dax_pmd_fault(struct vm_area_struct *, unsigned long addr, pmd_t *,
-				unsigned int flags, get_block_t);
-#else
 static inline int dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
 				pmd_t *pmd, unsigned int flags, get_block_t gb)
 {
 	return VM_FAULT_FALLBACK;
 }
-#endif
+
 int dax_pfn_mkwrite(struct vm_area_struct *, struct vm_fault *);
 #define dax_mkwrite(vma, vmf, gb)	dax_fault(vma, vmf, gb)
 
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 09/17] dax: remove dax_pmd_fault()
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

dax_pmd_fault() is the old struct buffer_head + get_block_t based 2 MiB DAX
fault handler.  This fault handler has been disabled for several kernel
releases, and support for PMDs will be reintroduced using the struct iomap
interface instead.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c            | 213 ----------------------------------------------------
 include/linux/dax.h |   6 +-
 2 files changed, 1 insertion(+), 218 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index e103053..3d0b103 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -915,219 +915,6 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 }
 EXPORT_SYMBOL_GPL(dax_fault);
 
-#if defined(CONFIG_TRANSPARENT_HUGEPAGE)
-/*
- * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
- * more often than one might expect in the below function.
- */
-#define PG_PMD_COLOUR	((PMD_SIZE >> PAGE_SHIFT) - 1)
-
-static void __dax_dbg(struct buffer_head *bh, unsigned long address,
-		const char *reason, const char *fn)
-{
-	if (bh) {
-		char bname[BDEVNAME_SIZE];
-		bdevname(bh->b_bdev, bname);
-		pr_debug("%s: %s addr: %lx dev %s state %lx start %lld "
-			"length %zd fallback: %s\n", fn, current->comm,
-			address, bname, bh->b_state, (u64)bh->b_blocknr,
-			bh->b_size, reason);
-	} else {
-		pr_debug("%s: %s addr: %lx fallback: %s\n", fn,
-			current->comm, address, reason);
-	}
-}
-
-#define dax_pmd_dbg(bh, address, reason)	__dax_dbg(bh, address, reason, "dax_pmd")
-
-/**
- * dax_pmd_fault - handle a PMD fault on a DAX file
- * @vma: The virtual memory area where the fault occurred
- * @vmf: The description of the fault
- * @get_block: The filesystem method used to translate file offsets to blocks
- *
- * When a page fault occurs, filesystems may call this helper in their
- * pmd_fault handler for DAX files.
- */
-int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
-		pmd_t *pmd, unsigned int flags, get_block_t get_block)
-{
-	struct file *file = vma->vm_file;
-	struct address_space *mapping = file->f_mapping;
-	struct inode *inode = mapping->host;
-	struct buffer_head bh;
-	unsigned blkbits = inode->i_blkbits;
-	unsigned long pmd_addr = address & PMD_MASK;
-	bool write = flags & FAULT_FLAG_WRITE;
-	struct block_device *bdev;
-	pgoff_t size, pgoff;
-	sector_t block;
-	int result = 0;
-	bool alloc = false;
-
-	/* dax pmd mappings require pfn_t_devmap() */
-	if (!IS_ENABLED(CONFIG_FS_DAX_PMD))
-		return VM_FAULT_FALLBACK;
-
-	/* Fall back to PTEs if we're going to COW */
-	if (write && !(vma->vm_flags & VM_SHARED)) {
-		split_huge_pmd(vma, pmd, address);
-		dax_pmd_dbg(NULL, address, "cow write");
-		return VM_FAULT_FALLBACK;
-	}
-	/* If the PMD would extend outside the VMA */
-	if (pmd_addr < vma->vm_start) {
-		dax_pmd_dbg(NULL, address, "vma start unaligned");
-		return VM_FAULT_FALLBACK;
-	}
-	if ((pmd_addr + PMD_SIZE) > vma->vm_end) {
-		dax_pmd_dbg(NULL, address, "vma end unaligned");
-		return VM_FAULT_FALLBACK;
-	}
-
-	pgoff = linear_page_index(vma, pmd_addr);
-	size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
-	if (pgoff >= size)
-		return VM_FAULT_SIGBUS;
-	/* If the PMD would cover blocks out of the file */
-	if ((pgoff | PG_PMD_COLOUR) >= size) {
-		dax_pmd_dbg(NULL, address,
-				"offset + huge page size > file size");
-		return VM_FAULT_FALLBACK;
-	}
-
-	memset(&bh, 0, sizeof(bh));
-	bh.b_bdev = inode->i_sb->s_bdev;
-	block = (sector_t)pgoff << (PAGE_SHIFT - blkbits);
-
-	bh.b_size = PMD_SIZE;
-
-	if (get_block(inode, block, &bh, 0) != 0)
-		return VM_FAULT_SIGBUS;
-
-	if (!buffer_mapped(&bh) && write) {
-		if (get_block(inode, block, &bh, 1) != 0)
-			return VM_FAULT_SIGBUS;
-		alloc = true;
-		WARN_ON_ONCE(buffer_unwritten(&bh) || buffer_new(&bh));
-	}
-
-	bdev = bh.b_bdev;
-
-	if (bh.b_size < PMD_SIZE) {
-		dax_pmd_dbg(&bh, address, "allocated block too small");
-		return VM_FAULT_FALLBACK;
-	}
-
-	/*
-	 * If we allocated new storage, make sure no process has any
-	 * zero pages covering this hole
-	 */
-	if (alloc) {
-		loff_t lstart = pgoff << PAGE_SHIFT;
-		loff_t lend = lstart + PMD_SIZE - 1; /* inclusive */
-
-		truncate_pagecache_range(inode, lstart, lend);
-	}
-
-	if (!write && !buffer_mapped(&bh)) {
-		spinlock_t *ptl;
-		pmd_t entry;
-		struct page *zero_page = get_huge_zero_page();
-
-		if (unlikely(!zero_page)) {
-			dax_pmd_dbg(&bh, address, "no zero page");
-			goto fallback;
-		}
-
-		ptl = pmd_lock(vma->vm_mm, pmd);
-		if (!pmd_none(*pmd)) {
-			spin_unlock(ptl);
-			dax_pmd_dbg(&bh, address, "pmd already present");
-			goto fallback;
-		}
-
-		dev_dbg(part_to_dev(bdev->bd_part),
-				"%s: %s addr: %lx pfn: <zero> sect: %llx\n",
-				__func__, current->comm, address,
-				(unsigned long long) to_sector(&bh, inode));
-
-		entry = mk_pmd(zero_page, vma->vm_page_prot);
-		entry = pmd_mkhuge(entry);
-		set_pmd_at(vma->vm_mm, pmd_addr, pmd, entry);
-		result = VM_FAULT_NOPAGE;
-		spin_unlock(ptl);
-	} else {
-		struct blk_dax_ctl dax = {
-			.sector = to_sector(&bh, inode),
-			.size = PMD_SIZE,
-		};
-		long length = dax_map_atomic(bdev, &dax);
-
-		if (length < 0) {
-			dax_pmd_dbg(&bh, address, "dax-error fallback");
-			goto fallback;
-		}
-		if (length < PMD_SIZE) {
-			dax_pmd_dbg(&bh, address, "dax-length too small");
-			dax_unmap_atomic(bdev, &dax);
-			goto fallback;
-		}
-		if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR) {
-			dax_pmd_dbg(&bh, address, "pfn unaligned");
-			dax_unmap_atomic(bdev, &dax);
-			goto fallback;
-		}
-
-		if (!pfn_t_devmap(dax.pfn)) {
-			dax_unmap_atomic(bdev, &dax);
-			dax_pmd_dbg(&bh, address, "pfn not in memmap");
-			goto fallback;
-		}
-		dax_unmap_atomic(bdev, &dax);
-
-		/*
-		 * For PTE faults we insert a radix tree entry for reads, and
-		 * leave it clean.  Then on the first write we dirty the radix
-		 * tree entry via the dax_pfn_mkwrite() path.  This sequence
-		 * allows the dax_pfn_mkwrite() call to be simpler and avoid a
-		 * call into get_block() to translate the pgoff to a sector in
-		 * order to be able to create a new radix tree entry.
-		 *
-		 * The PMD path doesn't have an equivalent to
-		 * dax_pfn_mkwrite(), though, so for a read followed by a
-		 * write we traverse all the way through dax_pmd_fault()
-		 * twice.  This means we can just skip inserting a radix tree
-		 * entry completely on the initial read and just wait until
-		 * the write to insert a dirty entry.
-		 */
-		if (write) {
-			/*
-			 * We should insert radix-tree entry and dirty it here.
-			 * For now this is broken...
-			 */
-		}
-
-		dev_dbg(part_to_dev(bdev->bd_part),
-				"%s: %s addr: %lx pfn: %lx sect: %llx\n",
-				__func__, current->comm, address,
-				pfn_t_to_pfn(dax.pfn),
-				(unsigned long long) dax.sector);
-		result |= vmf_insert_pfn_pmd(vma, address, pmd,
-				dax.pfn, write);
-	}
-
- out:
-	return result;
-
- fallback:
-	count_vm_event(THP_FAULT_FALLBACK);
-	result = VM_FAULT_FALLBACK;
-	goto out;
-}
-EXPORT_SYMBOL_GPL(dax_pmd_fault);
-#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
-
 /**
  * dax_pfn_mkwrite - handle first write to DAX page
  * @vma: The virtual memory area where the fault occurred
diff --git a/include/linux/dax.h b/include/linux/dax.h
index a41a747..0f74866 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -48,16 +48,12 @@ static inline int __dax_zero_page_range(struct block_device *bdev,
 }
 #endif
 
-#if defined(CONFIG_TRANSPARENT_HUGEPAGE)
-int dax_pmd_fault(struct vm_area_struct *, unsigned long addr, pmd_t *,
-				unsigned int flags, get_block_t);
-#else
 static inline int dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
 				pmd_t *pmd, unsigned int flags, get_block_t gb)
 {
 	return VM_FAULT_FALLBACK;
 }
-#endif
+
 int dax_pfn_mkwrite(struct vm_area_struct *, struct vm_fault *);
 #define dax_mkwrite(vma, vmf, gb)	dax_fault(vma, vmf, gb)
 
-- 
2.9.0


^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 10/17] dax: correct dax iomap code namespace
  2016-10-12 22:50 ` Ross Zwisler
                     ` (2 preceding siblings ...)
  (?)
@ 2016-10-12 22:50   ` Ross Zwisler
  -1 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner, linux-nvdimm,
	Christoph Hellwig, linux-xfs, linux-mm, Andreas Dilger,
	Alexander Viro, linux-fsdevel, Jan Kara, linux-ext4,
	Andrew Morton

The recently added DAX functions that use the new struct iomap data
structure were named iomap_dax_rw(), iomap_dax_fault() and
iomap_dax_actor().  These are actually defined in fs/dax.c, though, so
should be part of the "dax" namespace and not the "iomap" namespace.
Rename them to dax_iomap_rw(), dax_iomap_fault() and dax_iomap_actor()
respectively.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Suggested-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c            | 16 ++++++++--------
 fs/ext2/file.c      |  6 +++---
 fs/xfs/xfs_file.c   |  8 ++++----
 include/linux/dax.h |  4 ++--
 4 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 3d0b103..fdbd7a1 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1031,7 +1031,7 @@ EXPORT_SYMBOL_GPL(dax_truncate_page);
 
 #ifdef CONFIG_FS_IOMAP
 static loff_t
-iomap_dax_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
+dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 		struct iomap *iomap)
 {
 	struct iov_iter *iter = data;
@@ -1088,7 +1088,7 @@ iomap_dax_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 }
 
 /**
- * iomap_dax_rw - Perform I/O to a DAX file
+ * dax_iomap_rw - Perform I/O to a DAX file
  * @iocb:	The control block for this I/O
  * @iter:	The addresses to do I/O from or to
  * @ops:	iomap ops passed from the file system
@@ -1098,7 +1098,7 @@ iomap_dax_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
  * and evicting any page cache pages in the region under I/O.
  */
 ssize_t
-iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
+dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_ops *ops)
 {
 	struct address_space *mapping = iocb->ki_filp->f_mapping;
@@ -1128,7 +1128,7 @@ iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
 
 	while (iov_iter_count(iter)) {
 		ret = iomap_apply(inode, pos, iov_iter_count(iter), flags, ops,
-				iter, iomap_dax_actor);
+				iter, dax_iomap_actor);
 		if (ret <= 0)
 			break;
 		pos += ret;
@@ -1138,10 +1138,10 @@ iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
 	iocb->ki_pos += done;
 	return done ? done : ret;
 }
-EXPORT_SYMBOL_GPL(iomap_dax_rw);
+EXPORT_SYMBOL_GPL(dax_iomap_rw);
 
 /**
- * iomap_dax_fault - handle a page fault on a DAX file
+ * dax_iomap_fault - handle a page fault on a DAX file
  * @vma: The virtual memory area where the fault occurred
  * @vmf: The description of the fault
  * @ops: iomap ops passed from the file system
@@ -1150,7 +1150,7 @@ EXPORT_SYMBOL_GPL(iomap_dax_rw);
  * or mkwrite handler for DAX files. Assumes the caller has done all the
  * necessary locking for the page fault to proceed successfully.
  */
-int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
+int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 			struct iomap_ops *ops)
 {
 	struct address_space *mapping = vma->vm_file->f_mapping;
@@ -1252,5 +1252,5 @@ int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		return VM_FAULT_SIGBUS | major;
 	return VM_FAULT_NOPAGE | major;
 }
-EXPORT_SYMBOL_GPL(iomap_dax_fault);
+EXPORT_SYMBOL_GPL(dax_iomap_fault);
 #endif /* CONFIG_FS_IOMAP */
diff --git a/fs/ext2/file.c b/fs/ext2/file.c
index 0f257f8..32a4913 100644
--- a/fs/ext2/file.c
+++ b/fs/ext2/file.c
@@ -38,7 +38,7 @@ static ssize_t ext2_dax_read_iter(struct kiocb *iocb, struct iov_iter *to)
 		return 0; /* skip atime */
 
 	inode_lock_shared(inode);
-	ret = iomap_dax_rw(iocb, to, &ext2_iomap_ops);
+	ret = dax_iomap_rw(iocb, to, &ext2_iomap_ops);
 	inode_unlock_shared(inode);
 
 	file_accessed(iocb->ki_filp);
@@ -62,7 +62,7 @@ static ssize_t ext2_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	if (ret)
 		goto out_unlock;
 
-	ret = iomap_dax_rw(iocb, from, &ext2_iomap_ops);
+	ret = dax_iomap_rw(iocb, from, &ext2_iomap_ops);
 	if (ret > 0 && iocb->ki_pos > i_size_read(inode)) {
 		i_size_write(inode, iocb->ki_pos);
 		mark_inode_dirty(inode);
@@ -99,7 +99,7 @@ static int ext2_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 	}
 	down_read(&ei->dax_sem);
 
-	ret = iomap_dax_fault(vma, vmf, &ext2_iomap_ops);
+	ret = dax_iomap_fault(vma, vmf, &ext2_iomap_ops);
 
 	up_read(&ei->dax_sem);
 	if (vmf->flags & FAULT_FLAG_WRITE)
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index de7c53c..8f12152 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -344,7 +344,7 @@ xfs_file_dax_read(
 		return 0; /* skip atime */
 
 	xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
-	ret = iomap_dax_rw(iocb, to, &xfs_iomap_ops);
+	ret = dax_iomap_rw(iocb, to, &xfs_iomap_ops);
 	xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
 
 	file_accessed(iocb->ki_filp);
@@ -730,7 +730,7 @@ xfs_file_dax_write(
 
 	trace_xfs_file_dax_write(ip, count, pos);
 
-	ret = iomap_dax_rw(iocb, from, &xfs_iomap_ops);
+	ret = dax_iomap_rw(iocb, from, &xfs_iomap_ops);
 	if (ret > 0 && iocb->ki_pos > i_size_read(inode)) {
 		i_size_write(inode, iocb->ki_pos);
 		error = xfs_setfilesize(ip, pos, ret);
@@ -1679,7 +1679,7 @@ xfs_filemap_page_mkwrite(
 	xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
 
 	if (IS_DAX(inode)) {
-		ret = iomap_dax_fault(vma, vmf, &xfs_iomap_ops);
+		ret = dax_iomap_fault(vma, vmf, &xfs_iomap_ops);
 	} else {
 		ret = iomap_page_mkwrite(vma, vmf, &xfs_iomap_ops);
 		ret = block_page_mkwrite_return(ret);
@@ -1713,7 +1713,7 @@ xfs_filemap_fault(
 		 * changes to xfs_get_blocks_direct() to map unwritten extent
 		 * ioend for conversion on read-only mappings.
 		 */
-		ret = iomap_dax_fault(vma, vmf, &xfs_iomap_ops);
+		ret = dax_iomap_fault(vma, vmf, &xfs_iomap_ops);
 	} else
 		ret = filemap_fault(vma, vmf);
 	xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 0f74866..a3dfee4 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -11,13 +11,13 @@ struct iomap_ops;
 /* We use lowest available exceptional entry bit for locking */
 #define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
 
-ssize_t iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
+ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_ops *ops);
 ssize_t dax_do_io(struct kiocb *, struct inode *, struct iov_iter *,
 		  get_block_t, dio_iodone_t, int flags);
 int dax_zero_page_range(struct inode *, loff_t from, unsigned len, get_block_t);
 int dax_truncate_page(struct inode *, loff_t from, get_block_t);
-int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
+int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 			struct iomap_ops *ops);
 int dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t);
 int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index);
-- 
2.9.0

_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 10/17] dax: correct dax iomap code namespace
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

The recently added DAX functions that use the new struct iomap data
structure were named iomap_dax_rw(), iomap_dax_fault() and
iomap_dax_actor().  These are actually defined in fs/dax.c, though, so
should be part of the "dax" namespace and not the "iomap" namespace.
Rename them to dax_iomap_rw(), dax_iomap_fault() and dax_iomap_actor()
respectively.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Suggested-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c            | 16 ++++++++--------
 fs/ext2/file.c      |  6 +++---
 fs/xfs/xfs_file.c   |  8 ++++----
 include/linux/dax.h |  4 ++--
 4 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 3d0b103..fdbd7a1 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1031,7 +1031,7 @@ EXPORT_SYMBOL_GPL(dax_truncate_page);
 
 #ifdef CONFIG_FS_IOMAP
 static loff_t
-iomap_dax_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
+dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 		struct iomap *iomap)
 {
 	struct iov_iter *iter = data;
@@ -1088,7 +1088,7 @@ iomap_dax_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 }
 
 /**
- * iomap_dax_rw - Perform I/O to a DAX file
+ * dax_iomap_rw - Perform I/O to a DAX file
  * @iocb:	The control block for this I/O
  * @iter:	The addresses to do I/O from or to
  * @ops:	iomap ops passed from the file system
@@ -1098,7 +1098,7 @@ iomap_dax_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
  * and evicting any page cache pages in the region under I/O.
  */
 ssize_t
-iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
+dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_ops *ops)
 {
 	struct address_space *mapping = iocb->ki_filp->f_mapping;
@@ -1128,7 +1128,7 @@ iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
 
 	while (iov_iter_count(iter)) {
 		ret = iomap_apply(inode, pos, iov_iter_count(iter), flags, ops,
-				iter, iomap_dax_actor);
+				iter, dax_iomap_actor);
 		if (ret <= 0)
 			break;
 		pos += ret;
@@ -1138,10 +1138,10 @@ iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
 	iocb->ki_pos += done;
 	return done ? done : ret;
 }
-EXPORT_SYMBOL_GPL(iomap_dax_rw);
+EXPORT_SYMBOL_GPL(dax_iomap_rw);
 
 /**
- * iomap_dax_fault - handle a page fault on a DAX file
+ * dax_iomap_fault - handle a page fault on a DAX file
  * @vma: The virtual memory area where the fault occurred
  * @vmf: The description of the fault
  * @ops: iomap ops passed from the file system
@@ -1150,7 +1150,7 @@ EXPORT_SYMBOL_GPL(iomap_dax_rw);
  * or mkwrite handler for DAX files. Assumes the caller has done all the
  * necessary locking for the page fault to proceed successfully.
  */
-int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
+int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 			struct iomap_ops *ops)
 {
 	struct address_space *mapping = vma->vm_file->f_mapping;
@@ -1252,5 +1252,5 @@ int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		return VM_FAULT_SIGBUS | major;
 	return VM_FAULT_NOPAGE | major;
 }
-EXPORT_SYMBOL_GPL(iomap_dax_fault);
+EXPORT_SYMBOL_GPL(dax_iomap_fault);
 #endif /* CONFIG_FS_IOMAP */
diff --git a/fs/ext2/file.c b/fs/ext2/file.c
index 0f257f8..32a4913 100644
--- a/fs/ext2/file.c
+++ b/fs/ext2/file.c
@@ -38,7 +38,7 @@ static ssize_t ext2_dax_read_iter(struct kiocb *iocb, struct iov_iter *to)
 		return 0; /* skip atime */
 
 	inode_lock_shared(inode);
-	ret = iomap_dax_rw(iocb, to, &ext2_iomap_ops);
+	ret = dax_iomap_rw(iocb, to, &ext2_iomap_ops);
 	inode_unlock_shared(inode);
 
 	file_accessed(iocb->ki_filp);
@@ -62,7 +62,7 @@ static ssize_t ext2_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	if (ret)
 		goto out_unlock;
 
-	ret = iomap_dax_rw(iocb, from, &ext2_iomap_ops);
+	ret = dax_iomap_rw(iocb, from, &ext2_iomap_ops);
 	if (ret > 0 && iocb->ki_pos > i_size_read(inode)) {
 		i_size_write(inode, iocb->ki_pos);
 		mark_inode_dirty(inode);
@@ -99,7 +99,7 @@ static int ext2_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 	}
 	down_read(&ei->dax_sem);
 
-	ret = iomap_dax_fault(vma, vmf, &ext2_iomap_ops);
+	ret = dax_iomap_fault(vma, vmf, &ext2_iomap_ops);
 
 	up_read(&ei->dax_sem);
 	if (vmf->flags & FAULT_FLAG_WRITE)
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index de7c53c..8f12152 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -344,7 +344,7 @@ xfs_file_dax_read(
 		return 0; /* skip atime */
 
 	xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
-	ret = iomap_dax_rw(iocb, to, &xfs_iomap_ops);
+	ret = dax_iomap_rw(iocb, to, &xfs_iomap_ops);
 	xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
 
 	file_accessed(iocb->ki_filp);
@@ -730,7 +730,7 @@ xfs_file_dax_write(
 
 	trace_xfs_file_dax_write(ip, count, pos);
 
-	ret = iomap_dax_rw(iocb, from, &xfs_iomap_ops);
+	ret = dax_iomap_rw(iocb, from, &xfs_iomap_ops);
 	if (ret > 0 && iocb->ki_pos > i_size_read(inode)) {
 		i_size_write(inode, iocb->ki_pos);
 		error = xfs_setfilesize(ip, pos, ret);
@@ -1679,7 +1679,7 @@ xfs_filemap_page_mkwrite(
 	xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
 
 	if (IS_DAX(inode)) {
-		ret = iomap_dax_fault(vma, vmf, &xfs_iomap_ops);
+		ret = dax_iomap_fault(vma, vmf, &xfs_iomap_ops);
 	} else {
 		ret = iomap_page_mkwrite(vma, vmf, &xfs_iomap_ops);
 		ret = block_page_mkwrite_return(ret);
@@ -1713,7 +1713,7 @@ xfs_filemap_fault(
 		 * changes to xfs_get_blocks_direct() to map unwritten extent
 		 * ioend for conversion on read-only mappings.
 		 */
-		ret = iomap_dax_fault(vma, vmf, &xfs_iomap_ops);
+		ret = dax_iomap_fault(vma, vmf, &xfs_iomap_ops);
 	} else
 		ret = filemap_fault(vma, vmf);
 	xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 0f74866..a3dfee4 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -11,13 +11,13 @@ struct iomap_ops;
 /* We use lowest available exceptional entry bit for locking */
 #define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
 
-ssize_t iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
+ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_ops *ops);
 ssize_t dax_do_io(struct kiocb *, struct inode *, struct iov_iter *,
 		  get_block_t, dio_iodone_t, int flags);
 int dax_zero_page_range(struct inode *, loff_t from, unsigned len, get_block_t);
 int dax_truncate_page(struct inode *, loff_t from, get_block_t);
-int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
+int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 			struct iomap_ops *ops);
 int dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t);
 int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index);
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 10/17] dax: correct dax iomap code namespace
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

The recently added DAX functions that use the new struct iomap data
structure were named iomap_dax_rw(), iomap_dax_fault() and
iomap_dax_actor().  These are actually defined in fs/dax.c, though, so
should be part of the "dax" namespace and not the "iomap" namespace.
Rename them to dax_iomap_rw(), dax_iomap_fault() and dax_iomap_actor()
respectively.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Suggested-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c            | 16 ++++++++--------
 fs/ext2/file.c      |  6 +++---
 fs/xfs/xfs_file.c   |  8 ++++----
 include/linux/dax.h |  4 ++--
 4 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 3d0b103..fdbd7a1 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1031,7 +1031,7 @@ EXPORT_SYMBOL_GPL(dax_truncate_page);
 
 #ifdef CONFIG_FS_IOMAP
 static loff_t
-iomap_dax_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
+dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 		struct iomap *iomap)
 {
 	struct iov_iter *iter = data;
@@ -1088,7 +1088,7 @@ iomap_dax_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 }
 
 /**
- * iomap_dax_rw - Perform I/O to a DAX file
+ * dax_iomap_rw - Perform I/O to a DAX file
  * @iocb:	The control block for this I/O
  * @iter:	The addresses to do I/O from or to
  * @ops:	iomap ops passed from the file system
@@ -1098,7 +1098,7 @@ iomap_dax_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
  * and evicting any page cache pages in the region under I/O.
  */
 ssize_t
-iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
+dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_ops *ops)
 {
 	struct address_space *mapping = iocb->ki_filp->f_mapping;
@@ -1128,7 +1128,7 @@ iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
 
 	while (iov_iter_count(iter)) {
 		ret = iomap_apply(inode, pos, iov_iter_count(iter), flags, ops,
-				iter, iomap_dax_actor);
+				iter, dax_iomap_actor);
 		if (ret <= 0)
 			break;
 		pos += ret;
@@ -1138,10 +1138,10 @@ iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
 	iocb->ki_pos += done;
 	return done ? done : ret;
 }
-EXPORT_SYMBOL_GPL(iomap_dax_rw);
+EXPORT_SYMBOL_GPL(dax_iomap_rw);
 
 /**
- * iomap_dax_fault - handle a page fault on a DAX file
+ * dax_iomap_fault - handle a page fault on a DAX file
  * @vma: The virtual memory area where the fault occurred
  * @vmf: The description of the fault
  * @ops: iomap ops passed from the file system
@@ -1150,7 +1150,7 @@ EXPORT_SYMBOL_GPL(iomap_dax_rw);
  * or mkwrite handler for DAX files. Assumes the caller has done all the
  * necessary locking for the page fault to proceed successfully.
  */
-int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
+int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 			struct iomap_ops *ops)
 {
 	struct address_space *mapping = vma->vm_file->f_mapping;
@@ -1252,5 +1252,5 @@ int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		return VM_FAULT_SIGBUS | major;
 	return VM_FAULT_NOPAGE | major;
 }
-EXPORT_SYMBOL_GPL(iomap_dax_fault);
+EXPORT_SYMBOL_GPL(dax_iomap_fault);
 #endif /* CONFIG_FS_IOMAP */
diff --git a/fs/ext2/file.c b/fs/ext2/file.c
index 0f257f8..32a4913 100644
--- a/fs/ext2/file.c
+++ b/fs/ext2/file.c
@@ -38,7 +38,7 @@ static ssize_t ext2_dax_read_iter(struct kiocb *iocb, struct iov_iter *to)
 		return 0; /* skip atime */
 
 	inode_lock_shared(inode);
-	ret = iomap_dax_rw(iocb, to, &ext2_iomap_ops);
+	ret = dax_iomap_rw(iocb, to, &ext2_iomap_ops);
 	inode_unlock_shared(inode);
 
 	file_accessed(iocb->ki_filp);
@@ -62,7 +62,7 @@ static ssize_t ext2_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	if (ret)
 		goto out_unlock;
 
-	ret = iomap_dax_rw(iocb, from, &ext2_iomap_ops);
+	ret = dax_iomap_rw(iocb, from, &ext2_iomap_ops);
 	if (ret > 0 && iocb->ki_pos > i_size_read(inode)) {
 		i_size_write(inode, iocb->ki_pos);
 		mark_inode_dirty(inode);
@@ -99,7 +99,7 @@ static int ext2_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 	}
 	down_read(&ei->dax_sem);
 
-	ret = iomap_dax_fault(vma, vmf, &ext2_iomap_ops);
+	ret = dax_iomap_fault(vma, vmf, &ext2_iomap_ops);
 
 	up_read(&ei->dax_sem);
 	if (vmf->flags & FAULT_FLAG_WRITE)
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index de7c53c..8f12152 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -344,7 +344,7 @@ xfs_file_dax_read(
 		return 0; /* skip atime */
 
 	xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
-	ret = iomap_dax_rw(iocb, to, &xfs_iomap_ops);
+	ret = dax_iomap_rw(iocb, to, &xfs_iomap_ops);
 	xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
 
 	file_accessed(iocb->ki_filp);
@@ -730,7 +730,7 @@ xfs_file_dax_write(
 
 	trace_xfs_file_dax_write(ip, count, pos);
 
-	ret = iomap_dax_rw(iocb, from, &xfs_iomap_ops);
+	ret = dax_iomap_rw(iocb, from, &xfs_iomap_ops);
 	if (ret > 0 && iocb->ki_pos > i_size_read(inode)) {
 		i_size_write(inode, iocb->ki_pos);
 		error = xfs_setfilesize(ip, pos, ret);
@@ -1679,7 +1679,7 @@ xfs_filemap_page_mkwrite(
 	xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
 
 	if (IS_DAX(inode)) {
-		ret = iomap_dax_fault(vma, vmf, &xfs_iomap_ops);
+		ret = dax_iomap_fault(vma, vmf, &xfs_iomap_ops);
 	} else {
 		ret = iomap_page_mkwrite(vma, vmf, &xfs_iomap_ops);
 		ret = block_page_mkwrite_return(ret);
@@ -1713,7 +1713,7 @@ xfs_filemap_fault(
 		 * changes to xfs_get_blocks_direct() to map unwritten extent
 		 * ioend for conversion on read-only mappings.
 		 */
-		ret = iomap_dax_fault(vma, vmf, &xfs_iomap_ops);
+		ret = dax_iomap_fault(vma, vmf, &xfs_iomap_ops);
 	} else
 		ret = filemap_fault(vma, vmf);
 	xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 0f74866..a3dfee4 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -11,13 +11,13 @@ struct iomap_ops;
 /* We use lowest available exceptional entry bit for locking */
 #define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
 
-ssize_t iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
+ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_ops *ops);
 ssize_t dax_do_io(struct kiocb *, struct inode *, struct iov_iter *,
 		  get_block_t, dio_iodone_t, int flags);
 int dax_zero_page_range(struct inode *, loff_t from, unsigned len, get_block_t);
 int dax_truncate_page(struct inode *, loff_t from, get_block_t);
-int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
+int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 			struct iomap_ops *ops);
 int dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t);
 int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index);
-- 
2.9.0

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^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 10/17] dax: correct dax iomap code namespace
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel-u79uwXL29TY76Z2rM5mHXA
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner,
	linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw, Christoph Hellwig,
	linux-xfs-u79uwXL29TY76Z2rM5mHXA,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg, Andreas Dilger, Alexander Viro,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA, Jan Kara,
	linux-ext4-u79uwXL29TY76Z2rM5mHXA, Andrew Morton

The recently added DAX functions that use the new struct iomap data
structure were named iomap_dax_rw(), iomap_dax_fault() and
iomap_dax_actor().  These are actually defined in fs/dax.c, though, so
should be part of the "dax" namespace and not the "iomap" namespace.
Rename them to dax_iomap_rw(), dax_iomap_fault() and dax_iomap_actor()
respectively.

Signed-off-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Suggested-by: Dave Chinner <david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org>
Reviewed-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
Reviewed-by: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>
---
 fs/dax.c            | 16 ++++++++--------
 fs/ext2/file.c      |  6 +++---
 fs/xfs/xfs_file.c   |  8 ++++----
 include/linux/dax.h |  4 ++--
 4 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 3d0b103..fdbd7a1 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1031,7 +1031,7 @@ EXPORT_SYMBOL_GPL(dax_truncate_page);
 
 #ifdef CONFIG_FS_IOMAP
 static loff_t
-iomap_dax_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
+dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 		struct iomap *iomap)
 {
 	struct iov_iter *iter = data;
@@ -1088,7 +1088,7 @@ iomap_dax_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 }
 
 /**
- * iomap_dax_rw - Perform I/O to a DAX file
+ * dax_iomap_rw - Perform I/O to a DAX file
  * @iocb:	The control block for this I/O
  * @iter:	The addresses to do I/O from or to
  * @ops:	iomap ops passed from the file system
@@ -1098,7 +1098,7 @@ iomap_dax_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
  * and evicting any page cache pages in the region under I/O.
  */
 ssize_t
-iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
+dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_ops *ops)
 {
 	struct address_space *mapping = iocb->ki_filp->f_mapping;
@@ -1128,7 +1128,7 @@ iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
 
 	while (iov_iter_count(iter)) {
 		ret = iomap_apply(inode, pos, iov_iter_count(iter), flags, ops,
-				iter, iomap_dax_actor);
+				iter, dax_iomap_actor);
 		if (ret <= 0)
 			break;
 		pos += ret;
@@ -1138,10 +1138,10 @@ iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
 	iocb->ki_pos += done;
 	return done ? done : ret;
 }
-EXPORT_SYMBOL_GPL(iomap_dax_rw);
+EXPORT_SYMBOL_GPL(dax_iomap_rw);
 
 /**
- * iomap_dax_fault - handle a page fault on a DAX file
+ * dax_iomap_fault - handle a page fault on a DAX file
  * @vma: The virtual memory area where the fault occurred
  * @vmf: The description of the fault
  * @ops: iomap ops passed from the file system
@@ -1150,7 +1150,7 @@ EXPORT_SYMBOL_GPL(iomap_dax_rw);
  * or mkwrite handler for DAX files. Assumes the caller has done all the
  * necessary locking for the page fault to proceed successfully.
  */
-int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
+int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 			struct iomap_ops *ops)
 {
 	struct address_space *mapping = vma->vm_file->f_mapping;
@@ -1252,5 +1252,5 @@ int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		return VM_FAULT_SIGBUS | major;
 	return VM_FAULT_NOPAGE | major;
 }
-EXPORT_SYMBOL_GPL(iomap_dax_fault);
+EXPORT_SYMBOL_GPL(dax_iomap_fault);
 #endif /* CONFIG_FS_IOMAP */
diff --git a/fs/ext2/file.c b/fs/ext2/file.c
index 0f257f8..32a4913 100644
--- a/fs/ext2/file.c
+++ b/fs/ext2/file.c
@@ -38,7 +38,7 @@ static ssize_t ext2_dax_read_iter(struct kiocb *iocb, struct iov_iter *to)
 		return 0; /* skip atime */
 
 	inode_lock_shared(inode);
-	ret = iomap_dax_rw(iocb, to, &ext2_iomap_ops);
+	ret = dax_iomap_rw(iocb, to, &ext2_iomap_ops);
 	inode_unlock_shared(inode);
 
 	file_accessed(iocb->ki_filp);
@@ -62,7 +62,7 @@ static ssize_t ext2_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	if (ret)
 		goto out_unlock;
 
-	ret = iomap_dax_rw(iocb, from, &ext2_iomap_ops);
+	ret = dax_iomap_rw(iocb, from, &ext2_iomap_ops);
 	if (ret > 0 && iocb->ki_pos > i_size_read(inode)) {
 		i_size_write(inode, iocb->ki_pos);
 		mark_inode_dirty(inode);
@@ -99,7 +99,7 @@ static int ext2_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 	}
 	down_read(&ei->dax_sem);
 
-	ret = iomap_dax_fault(vma, vmf, &ext2_iomap_ops);
+	ret = dax_iomap_fault(vma, vmf, &ext2_iomap_ops);
 
 	up_read(&ei->dax_sem);
 	if (vmf->flags & FAULT_FLAG_WRITE)
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index de7c53c..8f12152 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -344,7 +344,7 @@ xfs_file_dax_read(
 		return 0; /* skip atime */
 
 	xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
-	ret = iomap_dax_rw(iocb, to, &xfs_iomap_ops);
+	ret = dax_iomap_rw(iocb, to, &xfs_iomap_ops);
 	xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
 
 	file_accessed(iocb->ki_filp);
@@ -730,7 +730,7 @@ xfs_file_dax_write(
 
 	trace_xfs_file_dax_write(ip, count, pos);
 
-	ret = iomap_dax_rw(iocb, from, &xfs_iomap_ops);
+	ret = dax_iomap_rw(iocb, from, &xfs_iomap_ops);
 	if (ret > 0 && iocb->ki_pos > i_size_read(inode)) {
 		i_size_write(inode, iocb->ki_pos);
 		error = xfs_setfilesize(ip, pos, ret);
@@ -1679,7 +1679,7 @@ xfs_filemap_page_mkwrite(
 	xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
 
 	if (IS_DAX(inode)) {
-		ret = iomap_dax_fault(vma, vmf, &xfs_iomap_ops);
+		ret = dax_iomap_fault(vma, vmf, &xfs_iomap_ops);
 	} else {
 		ret = iomap_page_mkwrite(vma, vmf, &xfs_iomap_ops);
 		ret = block_page_mkwrite_return(ret);
@@ -1713,7 +1713,7 @@ xfs_filemap_fault(
 		 * changes to xfs_get_blocks_direct() to map unwritten extent
 		 * ioend for conversion on read-only mappings.
 		 */
-		ret = iomap_dax_fault(vma, vmf, &xfs_iomap_ops);
+		ret = dax_iomap_fault(vma, vmf, &xfs_iomap_ops);
 	} else
 		ret = filemap_fault(vma, vmf);
 	xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 0f74866..a3dfee4 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -11,13 +11,13 @@ struct iomap_ops;
 /* We use lowest available exceptional entry bit for locking */
 #define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
 
-ssize_t iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
+ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_ops *ops);
 ssize_t dax_do_io(struct kiocb *, struct inode *, struct iov_iter *,
 		  get_block_t, dio_iodone_t, int flags);
 int dax_zero_page_range(struct inode *, loff_t from, unsigned len, get_block_t);
 int dax_truncate_page(struct inode *, loff_t from, get_block_t);
-int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
+int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 			struct iomap_ops *ops);
 int dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t);
 int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index);
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 10/17] dax: correct dax iomap code namespace
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

The recently added DAX functions that use the new struct iomap data
structure were named iomap_dax_rw(), iomap_dax_fault() and
iomap_dax_actor().  These are actually defined in fs/dax.c, though, so
should be part of the "dax" namespace and not the "iomap" namespace.
Rename them to dax_iomap_rw(), dax_iomap_fault() and dax_iomap_actor()
respectively.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Suggested-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c            | 16 ++++++++--------
 fs/ext2/file.c      |  6 +++---
 fs/xfs/xfs_file.c   |  8 ++++----
 include/linux/dax.h |  4 ++--
 4 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 3d0b103..fdbd7a1 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1031,7 +1031,7 @@ EXPORT_SYMBOL_GPL(dax_truncate_page);
 
 #ifdef CONFIG_FS_IOMAP
 static loff_t
-iomap_dax_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
+dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 		struct iomap *iomap)
 {
 	struct iov_iter *iter = data;
@@ -1088,7 +1088,7 @@ iomap_dax_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 }
 
 /**
- * iomap_dax_rw - Perform I/O to a DAX file
+ * dax_iomap_rw - Perform I/O to a DAX file
  * @iocb:	The control block for this I/O
  * @iter:	The addresses to do I/O from or to
  * @ops:	iomap ops passed from the file system
@@ -1098,7 +1098,7 @@ iomap_dax_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
  * and evicting any page cache pages in the region under I/O.
  */
 ssize_t
-iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
+dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_ops *ops)
 {
 	struct address_space *mapping = iocb->ki_filp->f_mapping;
@@ -1128,7 +1128,7 @@ iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
 
 	while (iov_iter_count(iter)) {
 		ret = iomap_apply(inode, pos, iov_iter_count(iter), flags, ops,
-				iter, iomap_dax_actor);
+				iter, dax_iomap_actor);
 		if (ret <= 0)
 			break;
 		pos += ret;
@@ -1138,10 +1138,10 @@ iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
 	iocb->ki_pos += done;
 	return done ? done : ret;
 }
-EXPORT_SYMBOL_GPL(iomap_dax_rw);
+EXPORT_SYMBOL_GPL(dax_iomap_rw);
 
 /**
- * iomap_dax_fault - handle a page fault on a DAX file
+ * dax_iomap_fault - handle a page fault on a DAX file
  * @vma: The virtual memory area where the fault occurred
  * @vmf: The description of the fault
  * @ops: iomap ops passed from the file system
@@ -1150,7 +1150,7 @@ EXPORT_SYMBOL_GPL(iomap_dax_rw);
  * or mkwrite handler for DAX files. Assumes the caller has done all the
  * necessary locking for the page fault to proceed successfully.
  */
-int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
+int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 			struct iomap_ops *ops)
 {
 	struct address_space *mapping = vma->vm_file->f_mapping;
@@ -1252,5 +1252,5 @@ int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		return VM_FAULT_SIGBUS | major;
 	return VM_FAULT_NOPAGE | major;
 }
-EXPORT_SYMBOL_GPL(iomap_dax_fault);
+EXPORT_SYMBOL_GPL(dax_iomap_fault);
 #endif /* CONFIG_FS_IOMAP */
diff --git a/fs/ext2/file.c b/fs/ext2/file.c
index 0f257f8..32a4913 100644
--- a/fs/ext2/file.c
+++ b/fs/ext2/file.c
@@ -38,7 +38,7 @@ static ssize_t ext2_dax_read_iter(struct kiocb *iocb, struct iov_iter *to)
 		return 0; /* skip atime */
 
 	inode_lock_shared(inode);
-	ret = iomap_dax_rw(iocb, to, &ext2_iomap_ops);
+	ret = dax_iomap_rw(iocb, to, &ext2_iomap_ops);
 	inode_unlock_shared(inode);
 
 	file_accessed(iocb->ki_filp);
@@ -62,7 +62,7 @@ static ssize_t ext2_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	if (ret)
 		goto out_unlock;
 
-	ret = iomap_dax_rw(iocb, from, &ext2_iomap_ops);
+	ret = dax_iomap_rw(iocb, from, &ext2_iomap_ops);
 	if (ret > 0 && iocb->ki_pos > i_size_read(inode)) {
 		i_size_write(inode, iocb->ki_pos);
 		mark_inode_dirty(inode);
@@ -99,7 +99,7 @@ static int ext2_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 	}
 	down_read(&ei->dax_sem);
 
-	ret = iomap_dax_fault(vma, vmf, &ext2_iomap_ops);
+	ret = dax_iomap_fault(vma, vmf, &ext2_iomap_ops);
 
 	up_read(&ei->dax_sem);
 	if (vmf->flags & FAULT_FLAG_WRITE)
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index de7c53c..8f12152 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -344,7 +344,7 @@ xfs_file_dax_read(
 		return 0; /* skip atime */
 
 	xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
-	ret = iomap_dax_rw(iocb, to, &xfs_iomap_ops);
+	ret = dax_iomap_rw(iocb, to, &xfs_iomap_ops);
 	xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
 
 	file_accessed(iocb->ki_filp);
@@ -730,7 +730,7 @@ xfs_file_dax_write(
 
 	trace_xfs_file_dax_write(ip, count, pos);
 
-	ret = iomap_dax_rw(iocb, from, &xfs_iomap_ops);
+	ret = dax_iomap_rw(iocb, from, &xfs_iomap_ops);
 	if (ret > 0 && iocb->ki_pos > i_size_read(inode)) {
 		i_size_write(inode, iocb->ki_pos);
 		error = xfs_setfilesize(ip, pos, ret);
@@ -1679,7 +1679,7 @@ xfs_filemap_page_mkwrite(
 	xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
 
 	if (IS_DAX(inode)) {
-		ret = iomap_dax_fault(vma, vmf, &xfs_iomap_ops);
+		ret = dax_iomap_fault(vma, vmf, &xfs_iomap_ops);
 	} else {
 		ret = iomap_page_mkwrite(vma, vmf, &xfs_iomap_ops);
 		ret = block_page_mkwrite_return(ret);
@@ -1713,7 +1713,7 @@ xfs_filemap_fault(
 		 * changes to xfs_get_blocks_direct() to map unwritten extent
 		 * ioend for conversion on read-only mappings.
 		 */
-		ret = iomap_dax_fault(vma, vmf, &xfs_iomap_ops);
+		ret = dax_iomap_fault(vma, vmf, &xfs_iomap_ops);
 	} else
 		ret = filemap_fault(vma, vmf);
 	xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 0f74866..a3dfee4 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -11,13 +11,13 @@ struct iomap_ops;
 /* We use lowest available exceptional entry bit for locking */
 #define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
 
-ssize_t iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
+ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_ops *ops);
 ssize_t dax_do_io(struct kiocb *, struct inode *, struct iov_iter *,
 		  get_block_t, dio_iodone_t, int flags);
 int dax_zero_page_range(struct inode *, loff_t from, unsigned len, get_block_t);
 int dax_truncate_page(struct inode *, loff_t from, get_block_t);
-int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
+int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 			struct iomap_ops *ops);
 int dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t);
 int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index);
-- 
2.9.0


^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 11/17] dax: add dax_iomap_sector() helper function
  2016-10-12 22:50 ` Ross Zwisler
                     ` (2 preceding siblings ...)
  (?)
@ 2016-10-12 22:50   ` Ross Zwisler
  -1 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner, linux-nvdimm,
	Christoph Hellwig, linux-xfs, linux-mm, Andreas Dilger,
	Alexander Viro, linux-fsdevel, Jan Kara, linux-ext4,
	Andrew Morton

To be able to correctly calculate the sector from a file position and a
struct iomap there is a complex little bit of logic that currently happens
in both dax_iomap_actor() and dax_iomap_fault().  This will need to be
repeated yet again in the DAX PMD fault handler when it is added, so break
it out into a helper function.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index fdbd7a1..7737954 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1030,6 +1030,11 @@ int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block)
 EXPORT_SYMBOL_GPL(dax_truncate_page);
 
 #ifdef CONFIG_FS_IOMAP
+static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
+{
+	return iomap->blkno + (((pos & PAGE_MASK) - iomap->offset) >> 9);
+}
+
 static loff_t
 dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 		struct iomap *iomap)
@@ -1055,8 +1060,7 @@ dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 		struct blk_dax_ctl dax = { 0 };
 		ssize_t map_len;
 
-		dax.sector = iomap->blkno +
-			(((pos & PAGE_MASK) - iomap->offset) >> 9);
+		dax.sector = dax_iomap_sector(iomap, pos);
 		dax.size = (length + offset + PAGE_SIZE - 1) & PAGE_MASK;
 		map_len = dax_map_atomic(iomap->bdev, &dax);
 		if (map_len < 0) {
@@ -1193,7 +1197,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		goto unlock_entry;
 	}
 
-	sector = iomap.blkno + (((pos & PAGE_MASK) - iomap.offset) >> 9);
+	sector = dax_iomap_sector(&iomap, pos);
 
 	if (vmf->cow_page) {
 		switch (iomap.type) {
-- 
2.9.0

_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 11/17] dax: add dax_iomap_sector() helper function
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

To be able to correctly calculate the sector from a file position and a
struct iomap there is a complex little bit of logic that currently happens
in both dax_iomap_actor() and dax_iomap_fault().  This will need to be
repeated yet again in the DAX PMD fault handler when it is added, so break
it out into a helper function.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index fdbd7a1..7737954 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1030,6 +1030,11 @@ int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block)
 EXPORT_SYMBOL_GPL(dax_truncate_page);
 
 #ifdef CONFIG_FS_IOMAP
+static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
+{
+	return iomap->blkno + (((pos & PAGE_MASK) - iomap->offset) >> 9);
+}
+
 static loff_t
 dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 		struct iomap *iomap)
@@ -1055,8 +1060,7 @@ dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 		struct blk_dax_ctl dax = { 0 };
 		ssize_t map_len;
 
-		dax.sector = iomap->blkno +
-			(((pos & PAGE_MASK) - iomap->offset) >> 9);
+		dax.sector = dax_iomap_sector(iomap, pos);
 		dax.size = (length + offset + PAGE_SIZE - 1) & PAGE_MASK;
 		map_len = dax_map_atomic(iomap->bdev, &dax);
 		if (map_len < 0) {
@@ -1193,7 +1197,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		goto unlock_entry;
 	}
 
-	sector = iomap.blkno + (((pos & PAGE_MASK) - iomap.offset) >> 9);
+	sector = dax_iomap_sector(&iomap, pos);
 
 	if (vmf->cow_page) {
 		switch (iomap.type) {
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 11/17] dax: add dax_iomap_sector() helper function
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

To be able to correctly calculate the sector from a file position and a
struct iomap there is a complex little bit of logic that currently happens
in both dax_iomap_actor() and dax_iomap_fault().  This will need to be
repeated yet again in the DAX PMD fault handler when it is added, so break
it out into a helper function.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index fdbd7a1..7737954 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1030,6 +1030,11 @@ int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block)
 EXPORT_SYMBOL_GPL(dax_truncate_page);
 
 #ifdef CONFIG_FS_IOMAP
+static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
+{
+	return iomap->blkno + (((pos & PAGE_MASK) - iomap->offset) >> 9);
+}
+
 static loff_t
 dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 		struct iomap *iomap)
@@ -1055,8 +1060,7 @@ dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 		struct blk_dax_ctl dax = { 0 };
 		ssize_t map_len;
 
-		dax.sector = iomap->blkno +
-			(((pos & PAGE_MASK) - iomap->offset) >> 9);
+		dax.sector = dax_iomap_sector(iomap, pos);
 		dax.size = (length + offset + PAGE_SIZE - 1) & PAGE_MASK;
 		map_len = dax_map_atomic(iomap->bdev, &dax);
 		if (map_len < 0) {
@@ -1193,7 +1197,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		goto unlock_entry;
 	}
 
-	sector = iomap.blkno + (((pos & PAGE_MASK) - iomap.offset) >> 9);
+	sector = dax_iomap_sector(&iomap, pos);
 
 	if (vmf->cow_page) {
 		switch (iomap.type) {
-- 
2.9.0

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 11/17] dax: add dax_iomap_sector() helper function
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel-u79uwXL29TY76Z2rM5mHXA
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner,
	linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw, Christoph Hellwig,
	linux-xfs-u79uwXL29TY76Z2rM5mHXA,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg, Andreas Dilger, Alexander Viro,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA, Jan Kara,
	linux-ext4-u79uwXL29TY76Z2rM5mHXA, Andrew Morton

To be able to correctly calculate the sector from a file position and a
struct iomap there is a complex little bit of logic that currently happens
in both dax_iomap_actor() and dax_iomap_fault().  This will need to be
repeated yet again in the DAX PMD fault handler when it is added, so break
it out into a helper function.

Signed-off-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Reviewed-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
Reviewed-by: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>
---
 fs/dax.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index fdbd7a1..7737954 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1030,6 +1030,11 @@ int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block)
 EXPORT_SYMBOL_GPL(dax_truncate_page);
 
 #ifdef CONFIG_FS_IOMAP
+static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
+{
+	return iomap->blkno + (((pos & PAGE_MASK) - iomap->offset) >> 9);
+}
+
 static loff_t
 dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 		struct iomap *iomap)
@@ -1055,8 +1060,7 @@ dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 		struct blk_dax_ctl dax = { 0 };
 		ssize_t map_len;
 
-		dax.sector = iomap->blkno +
-			(((pos & PAGE_MASK) - iomap->offset) >> 9);
+		dax.sector = dax_iomap_sector(iomap, pos);
 		dax.size = (length + offset + PAGE_SIZE - 1) & PAGE_MASK;
 		map_len = dax_map_atomic(iomap->bdev, &dax);
 		if (map_len < 0) {
@@ -1193,7 +1197,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		goto unlock_entry;
 	}
 
-	sector = iomap.blkno + (((pos & PAGE_MASK) - iomap.offset) >> 9);
+	sector = dax_iomap_sector(&iomap, pos);
 
 	if (vmf->cow_page) {
 		switch (iomap.type) {
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 11/17] dax: add dax_iomap_sector() helper function
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

To be able to correctly calculate the sector from a file position and a
struct iomap there is a complex little bit of logic that currently happens
in both dax_iomap_actor() and dax_iomap_fault().  This will need to be
repeated yet again in the DAX PMD fault handler when it is added, so break
it out into a helper function.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index fdbd7a1..7737954 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1030,6 +1030,11 @@ int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block)
 EXPORT_SYMBOL_GPL(dax_truncate_page);
 
 #ifdef CONFIG_FS_IOMAP
+static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
+{
+	return iomap->blkno + (((pos & PAGE_MASK) - iomap->offset) >> 9);
+}
+
 static loff_t
 dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 		struct iomap *iomap)
@@ -1055,8 +1060,7 @@ dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 		struct blk_dax_ctl dax = { 0 };
 		ssize_t map_len;
 
-		dax.sector = iomap->blkno +
-			(((pos & PAGE_MASK) - iomap->offset) >> 9);
+		dax.sector = dax_iomap_sector(iomap, pos);
 		dax.size = (length + offset + PAGE_SIZE - 1) & PAGE_MASK;
 		map_len = dax_map_atomic(iomap->bdev, &dax);
 		if (map_len < 0) {
@@ -1193,7 +1197,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		goto unlock_entry;
 	}
 
-	sector = iomap.blkno + (((pos & PAGE_MASK) - iomap.offset) >> 9);
+	sector = dax_iomap_sector(&iomap, pos);
 
 	if (vmf->cow_page) {
 		switch (iomap.type) {
-- 
2.9.0


^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 12/17] dax: dax_iomap_fault() needs to call iomap_end()
  2016-10-12 22:50 ` Ross Zwisler
                     ` (2 preceding siblings ...)
  (?)
@ 2016-10-12 22:50   ` Ross Zwisler
  -1 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner, linux-nvdimm,
	Christoph Hellwig, linux-xfs, linux-mm, Andreas Dilger,
	Alexander Viro, linux-fsdevel, Jan Kara, linux-ext4,
	Andrew Morton

Currently iomap_end() doesn't do anything for DAX page faults for both ext2
and XFS.  ext2_iomap_end() just checks for a write underrun, and
xfs_file_iomap_end() checks to see if it needs to finish a delayed
allocation.  However, in the future iomap_end() calls might be needed to
make sure we have balanced allocations, locks, etc.  So, add calls to
iomap_end() with appropriate error handling to dax_iomap_fault().

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c | 37 +++++++++++++++++++++++++++++--------
 1 file changed, 29 insertions(+), 8 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 7737954..6edd89b 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1165,6 +1165,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	struct iomap iomap = { 0 };
 	unsigned flags = 0;
 	int error, major = 0;
+	int locked_status = 0;
 	void *entry;
 
 	/*
@@ -1194,7 +1195,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		goto unlock_entry;
 	if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
 		error = -EIO;		/* fs corruption? */
-		goto unlock_entry;
+		goto finish_iomap;
 	}
 
 	sector = dax_iomap_sector(&iomap, pos);
@@ -1216,13 +1217,15 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		}
 
 		if (error)
-			goto unlock_entry;
+			goto finish_iomap;
 		if (!radix_tree_exceptional_entry(entry)) {
 			vmf->page = entry;
-			return VM_FAULT_LOCKED;
+			locked_status = VM_FAULT_LOCKED;
+		} else {
+			vmf->entry = entry;
+			locked_status = VM_FAULT_DAX_LOCKED;
 		}
-		vmf->entry = entry;
-		return VM_FAULT_DAX_LOCKED;
+		goto finish_iomap;
 	}
 
 	switch (iomap.type) {
@@ -1237,8 +1240,10 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		break;
 	case IOMAP_UNWRITTEN:
 	case IOMAP_HOLE:
-		if (!(vmf->flags & FAULT_FLAG_WRITE))
-			return dax_load_hole(mapping, entry, vmf);
+		if (!(vmf->flags & FAULT_FLAG_WRITE)) {
+			locked_status = dax_load_hole(mapping, entry, vmf);
+			break;
+		}
 		/*FALLTHRU*/
 	default:
 		WARN_ON_ONCE(1);
@@ -1246,14 +1251,30 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		break;
 	}
 
+ finish_iomap:
+	if (ops->iomap_end) {
+		if (error) {
+			/* keep previous error */
+			ops->iomap_end(inode, pos, PAGE_SIZE, 0, flags,
+					&iomap);
+		} else {
+			error = ops->iomap_end(inode, pos, PAGE_SIZE,
+					PAGE_SIZE, flags, &iomap);
+		}
+	}
  unlock_entry:
-	put_locked_mapping_entry(mapping, vmf->pgoff, entry);
+	if (!locked_status || error)
+		put_locked_mapping_entry(mapping, vmf->pgoff, entry);
  out:
 	if (error == -ENOMEM)
 		return VM_FAULT_OOM | major;
 	/* -EBUSY is fine, somebody else faulted on the same PTE */
 	if (error < 0 && error != -EBUSY)
 		return VM_FAULT_SIGBUS | major;
+	if (locked_status) {
+		WARN_ON_ONCE(error); /* -EBUSY from ops->iomap_end? */
+		return locked_status;
+	}
 	return VM_FAULT_NOPAGE | major;
 }
 EXPORT_SYMBOL_GPL(dax_iomap_fault);
-- 
2.9.0

_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 12/17] dax: dax_iomap_fault() needs to call iomap_end()
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

Currently iomap_end() doesn't do anything for DAX page faults for both ext2
and XFS.  ext2_iomap_end() just checks for a write underrun, and
xfs_file_iomap_end() checks to see if it needs to finish a delayed
allocation.  However, in the future iomap_end() calls might be needed to
make sure we have balanced allocations, locks, etc.  So, add calls to
iomap_end() with appropriate error handling to dax_iomap_fault().

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c | 37 +++++++++++++++++++++++++++++--------
 1 file changed, 29 insertions(+), 8 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 7737954..6edd89b 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1165,6 +1165,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	struct iomap iomap = { 0 };
 	unsigned flags = 0;
 	int error, major = 0;
+	int locked_status = 0;
 	void *entry;
 
 	/*
@@ -1194,7 +1195,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		goto unlock_entry;
 	if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
 		error = -EIO;		/* fs corruption? */
-		goto unlock_entry;
+		goto finish_iomap;
 	}
 
 	sector = dax_iomap_sector(&iomap, pos);
@@ -1216,13 +1217,15 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		}
 
 		if (error)
-			goto unlock_entry;
+			goto finish_iomap;
 		if (!radix_tree_exceptional_entry(entry)) {
 			vmf->page = entry;
-			return VM_FAULT_LOCKED;
+			locked_status = VM_FAULT_LOCKED;
+		} else {
+			vmf->entry = entry;
+			locked_status = VM_FAULT_DAX_LOCKED;
 		}
-		vmf->entry = entry;
-		return VM_FAULT_DAX_LOCKED;
+		goto finish_iomap;
 	}
 
 	switch (iomap.type) {
@@ -1237,8 +1240,10 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		break;
 	case IOMAP_UNWRITTEN:
 	case IOMAP_HOLE:
-		if (!(vmf->flags & FAULT_FLAG_WRITE))
-			return dax_load_hole(mapping, entry, vmf);
+		if (!(vmf->flags & FAULT_FLAG_WRITE)) {
+			locked_status = dax_load_hole(mapping, entry, vmf);
+			break;
+		}
 		/*FALLTHRU*/
 	default:
 		WARN_ON_ONCE(1);
@@ -1246,14 +1251,30 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		break;
 	}
 
+ finish_iomap:
+	if (ops->iomap_end) {
+		if (error) {
+			/* keep previous error */
+			ops->iomap_end(inode, pos, PAGE_SIZE, 0, flags,
+					&iomap);
+		} else {
+			error = ops->iomap_end(inode, pos, PAGE_SIZE,
+					PAGE_SIZE, flags, &iomap);
+		}
+	}
  unlock_entry:
-	put_locked_mapping_entry(mapping, vmf->pgoff, entry);
+	if (!locked_status || error)
+		put_locked_mapping_entry(mapping, vmf->pgoff, entry);
  out:
 	if (error == -ENOMEM)
 		return VM_FAULT_OOM | major;
 	/* -EBUSY is fine, somebody else faulted on the same PTE */
 	if (error < 0 && error != -EBUSY)
 		return VM_FAULT_SIGBUS | major;
+	if (locked_status) {
+		WARN_ON_ONCE(error); /* -EBUSY from ops->iomap_end? */
+		return locked_status;
+	}
 	return VM_FAULT_NOPAGE | major;
 }
 EXPORT_SYMBOL_GPL(dax_iomap_fault);
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 12/17] dax: dax_iomap_fault() needs to call iomap_end()
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

Currently iomap_end() doesn't do anything for DAX page faults for both ext2
and XFS.  ext2_iomap_end() just checks for a write underrun, and
xfs_file_iomap_end() checks to see if it needs to finish a delayed
allocation.  However, in the future iomap_end() calls might be needed to
make sure we have balanced allocations, locks, etc.  So, add calls to
iomap_end() with appropriate error handling to dax_iomap_fault().

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c | 37 +++++++++++++++++++++++++++++--------
 1 file changed, 29 insertions(+), 8 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 7737954..6edd89b 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1165,6 +1165,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	struct iomap iomap = { 0 };
 	unsigned flags = 0;
 	int error, major = 0;
+	int locked_status = 0;
 	void *entry;
 
 	/*
@@ -1194,7 +1195,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		goto unlock_entry;
 	if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
 		error = -EIO;		/* fs corruption? */
-		goto unlock_entry;
+		goto finish_iomap;
 	}
 
 	sector = dax_iomap_sector(&iomap, pos);
@@ -1216,13 +1217,15 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		}
 
 		if (error)
-			goto unlock_entry;
+			goto finish_iomap;
 		if (!radix_tree_exceptional_entry(entry)) {
 			vmf->page = entry;
-			return VM_FAULT_LOCKED;
+			locked_status = VM_FAULT_LOCKED;
+		} else {
+			vmf->entry = entry;
+			locked_status = VM_FAULT_DAX_LOCKED;
 		}
-		vmf->entry = entry;
-		return VM_FAULT_DAX_LOCKED;
+		goto finish_iomap;
 	}
 
 	switch (iomap.type) {
@@ -1237,8 +1240,10 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		break;
 	case IOMAP_UNWRITTEN:
 	case IOMAP_HOLE:
-		if (!(vmf->flags & FAULT_FLAG_WRITE))
-			return dax_load_hole(mapping, entry, vmf);
+		if (!(vmf->flags & FAULT_FLAG_WRITE)) {
+			locked_status = dax_load_hole(mapping, entry, vmf);
+			break;
+		}
 		/*FALLTHRU*/
 	default:
 		WARN_ON_ONCE(1);
@@ -1246,14 +1251,30 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		break;
 	}
 
+ finish_iomap:
+	if (ops->iomap_end) {
+		if (error) {
+			/* keep previous error */
+			ops->iomap_end(inode, pos, PAGE_SIZE, 0, flags,
+					&iomap);
+		} else {
+			error = ops->iomap_end(inode, pos, PAGE_SIZE,
+					PAGE_SIZE, flags, &iomap);
+		}
+	}
  unlock_entry:
-	put_locked_mapping_entry(mapping, vmf->pgoff, entry);
+	if (!locked_status || error)
+		put_locked_mapping_entry(mapping, vmf->pgoff, entry);
  out:
 	if (error == -ENOMEM)
 		return VM_FAULT_OOM | major;
 	/* -EBUSY is fine, somebody else faulted on the same PTE */
 	if (error < 0 && error != -EBUSY)
 		return VM_FAULT_SIGBUS | major;
+	if (locked_status) {
+		WARN_ON_ONCE(error); /* -EBUSY from ops->iomap_end? */
+		return locked_status;
+	}
 	return VM_FAULT_NOPAGE | major;
 }
 EXPORT_SYMBOL_GPL(dax_iomap_fault);
-- 
2.9.0

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 12/17] dax: dax_iomap_fault() needs to call iomap_end()
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel-u79uwXL29TY76Z2rM5mHXA
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner,
	linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw, Christoph Hellwig,
	linux-xfs-u79uwXL29TY76Z2rM5mHXA,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg, Andreas Dilger, Alexander Viro,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA, Jan Kara,
	linux-ext4-u79uwXL29TY76Z2rM5mHXA, Andrew Morton

Currently iomap_end() doesn't do anything for DAX page faults for both ext2
and XFS.  ext2_iomap_end() just checks for a write underrun, and
xfs_file_iomap_end() checks to see if it needs to finish a delayed
allocation.  However, in the future iomap_end() calls might be needed to
make sure we have balanced allocations, locks, etc.  So, add calls to
iomap_end() with appropriate error handling to dax_iomap_fault().

Signed-off-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Suggested-by: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>
Reviewed-by: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>
---
 fs/dax.c | 37 +++++++++++++++++++++++++++++--------
 1 file changed, 29 insertions(+), 8 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 7737954..6edd89b 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1165,6 +1165,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	struct iomap iomap = { 0 };
 	unsigned flags = 0;
 	int error, major = 0;
+	int locked_status = 0;
 	void *entry;
 
 	/*
@@ -1194,7 +1195,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		goto unlock_entry;
 	if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
 		error = -EIO;		/* fs corruption? */
-		goto unlock_entry;
+		goto finish_iomap;
 	}
 
 	sector = dax_iomap_sector(&iomap, pos);
@@ -1216,13 +1217,15 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		}
 
 		if (error)
-			goto unlock_entry;
+			goto finish_iomap;
 		if (!radix_tree_exceptional_entry(entry)) {
 			vmf->page = entry;
-			return VM_FAULT_LOCKED;
+			locked_status = VM_FAULT_LOCKED;
+		} else {
+			vmf->entry = entry;
+			locked_status = VM_FAULT_DAX_LOCKED;
 		}
-		vmf->entry = entry;
-		return VM_FAULT_DAX_LOCKED;
+		goto finish_iomap;
 	}
 
 	switch (iomap.type) {
@@ -1237,8 +1240,10 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		break;
 	case IOMAP_UNWRITTEN:
 	case IOMAP_HOLE:
-		if (!(vmf->flags & FAULT_FLAG_WRITE))
-			return dax_load_hole(mapping, entry, vmf);
+		if (!(vmf->flags & FAULT_FLAG_WRITE)) {
+			locked_status = dax_load_hole(mapping, entry, vmf);
+			break;
+		}
 		/*FALLTHRU*/
 	default:
 		WARN_ON_ONCE(1);
@@ -1246,14 +1251,30 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		break;
 	}
 
+ finish_iomap:
+	if (ops->iomap_end) {
+		if (error) {
+			/* keep previous error */
+			ops->iomap_end(inode, pos, PAGE_SIZE, 0, flags,
+					&iomap);
+		} else {
+			error = ops->iomap_end(inode, pos, PAGE_SIZE,
+					PAGE_SIZE, flags, &iomap);
+		}
+	}
  unlock_entry:
-	put_locked_mapping_entry(mapping, vmf->pgoff, entry);
+	if (!locked_status || error)
+		put_locked_mapping_entry(mapping, vmf->pgoff, entry);
  out:
 	if (error == -ENOMEM)
 		return VM_FAULT_OOM | major;
 	/* -EBUSY is fine, somebody else faulted on the same PTE */
 	if (error < 0 && error != -EBUSY)
 		return VM_FAULT_SIGBUS | major;
+	if (locked_status) {
+		WARN_ON_ONCE(error); /* -EBUSY from ops->iomap_end? */
+		return locked_status;
+	}
 	return VM_FAULT_NOPAGE | major;
 }
 EXPORT_SYMBOL_GPL(dax_iomap_fault);
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 12/17] dax: dax_iomap_fault() needs to call iomap_end()
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

Currently iomap_end() doesn't do anything for DAX page faults for both ext2
and XFS.  ext2_iomap_end() just checks for a write underrun, and
xfs_file_iomap_end() checks to see if it needs to finish a delayed
allocation.  However, in the future iomap_end() calls might be needed to
make sure we have balanced allocations, locks, etc.  So, add calls to
iomap_end() with appropriate error handling to dax_iomap_fault().

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c | 37 +++++++++++++++++++++++++++++--------
 1 file changed, 29 insertions(+), 8 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 7737954..6edd89b 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1165,6 +1165,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	struct iomap iomap = { 0 };
 	unsigned flags = 0;
 	int error, major = 0;
+	int locked_status = 0;
 	void *entry;
 
 	/*
@@ -1194,7 +1195,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		goto unlock_entry;
 	if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
 		error = -EIO;		/* fs corruption? */
-		goto unlock_entry;
+		goto finish_iomap;
 	}
 
 	sector = dax_iomap_sector(&iomap, pos);
@@ -1216,13 +1217,15 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		}
 
 		if (error)
-			goto unlock_entry;
+			goto finish_iomap;
 		if (!radix_tree_exceptional_entry(entry)) {
 			vmf->page = entry;
-			return VM_FAULT_LOCKED;
+			locked_status = VM_FAULT_LOCKED;
+		} else {
+			vmf->entry = entry;
+			locked_status = VM_FAULT_DAX_LOCKED;
 		}
-		vmf->entry = entry;
-		return VM_FAULT_DAX_LOCKED;
+		goto finish_iomap;
 	}
 
 	switch (iomap.type) {
@@ -1237,8 +1240,10 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		break;
 	case IOMAP_UNWRITTEN:
 	case IOMAP_HOLE:
-		if (!(vmf->flags & FAULT_FLAG_WRITE))
-			return dax_load_hole(mapping, entry, vmf);
+		if (!(vmf->flags & FAULT_FLAG_WRITE)) {
+			locked_status = dax_load_hole(mapping, entry, vmf);
+			break;
+		}
 		/*FALLTHRU*/
 	default:
 		WARN_ON_ONCE(1);
@@ -1246,14 +1251,30 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		break;
 	}
 
+ finish_iomap:
+	if (ops->iomap_end) {
+		if (error) {
+			/* keep previous error */
+			ops->iomap_end(inode, pos, PAGE_SIZE, 0, flags,
+					&iomap);
+		} else {
+			error = ops->iomap_end(inode, pos, PAGE_SIZE,
+					PAGE_SIZE, flags, &iomap);
+		}
+	}
  unlock_entry:
-	put_locked_mapping_entry(mapping, vmf->pgoff, entry);
+	if (!locked_status || error)
+		put_locked_mapping_entry(mapping, vmf->pgoff, entry);
  out:
 	if (error == -ENOMEM)
 		return VM_FAULT_OOM | major;
 	/* -EBUSY is fine, somebody else faulted on the same PTE */
 	if (error < 0 && error != -EBUSY)
 		return VM_FAULT_SIGBUS | major;
+	if (locked_status) {
+		WARN_ON_ONCE(error); /* -EBUSY from ops->iomap_end? */
+		return locked_status;
+	}
 	return VM_FAULT_NOPAGE | major;
 }
 EXPORT_SYMBOL_GPL(dax_iomap_fault);
-- 
2.9.0


^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 13/17] dax: move RADIX_DAX_* defines to dax.h
  2016-10-12 22:50 ` Ross Zwisler
                     ` (2 preceding siblings ...)
  (?)
@ 2016-10-12 22:50   ` Ross Zwisler
  -1 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner, linux-nvdimm,
	Christoph Hellwig, linux-xfs, linux-mm, Andreas Dilger,
	Alexander Viro, linux-fsdevel, Jan Kara, linux-ext4,
	Andrew Morton

The RADIX_DAX_* defines currently mostly live in fs/dax.c, with just
RADIX_DAX_ENTRY_LOCK being in include/linux/dax.h so it can be used in
mm/filemap.c.  When we add PMD support, though, mm/filemap.c will also need
access to the RADIX_DAX_PTE type so it can properly construct a 4k sized
empty entry.

Instead of shifting the defines between dax.c and dax.h as they are
individually used in other code, just move them wholesale to dax.h so
they'll be available when we need them.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c            | 14 --------------
 include/linux/dax.h | 15 ++++++++++++++-
 2 files changed, 14 insertions(+), 15 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 6edd89b..c45cc4d 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -34,20 +34,6 @@
 #include <linux/iomap.h>
 #include "internal.h"
 
-/*
- * We use lowest available bit in exceptional entry for locking, other two
- * bits to determine entry type. In total 3 special bits.
- */
-#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 3)
-#define RADIX_DAX_PTE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
-#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
-#define RADIX_DAX_TYPE_MASK (RADIX_DAX_PTE | RADIX_DAX_PMD)
-#define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_TYPE_MASK)
-#define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
-#define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
-		RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE) | \
-		RADIX_TREE_EXCEPTIONAL_ENTRY))
-
 /* We choose 4096 entries - same as per-zone page wait tables */
 #define DAX_WAIT_TABLE_BITS 12
 #define DAX_WAIT_TABLE_ENTRIES (1 << DAX_WAIT_TABLE_BITS)
diff --git a/include/linux/dax.h b/include/linux/dax.h
index a3dfee4..e9ea78c 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -8,8 +8,21 @@
 
 struct iomap_ops;
 
-/* We use lowest available exceptional entry bit for locking */
+/*
+ * We use lowest available bit in exceptional entry for locking, other two
+ * bits to determine entry type. In total 3 special bits.
+ */
+#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 3)
 #define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
+#define RADIX_DAX_PTE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
+#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
+#define RADIX_DAX_TYPE_MASK (RADIX_DAX_PTE | RADIX_DAX_PMD)
+#define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_TYPE_MASK)
+#define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
+#define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
+		RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE) | \
+		RADIX_TREE_EXCEPTIONAL_ENTRY))
+
 
 ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_ops *ops);
-- 
2.9.0

_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 13/17] dax: move RADIX_DAX_* defines to dax.h
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

The RADIX_DAX_* defines currently mostly live in fs/dax.c, with just
RADIX_DAX_ENTRY_LOCK being in include/linux/dax.h so it can be used in
mm/filemap.c.  When we add PMD support, though, mm/filemap.c will also need
access to the RADIX_DAX_PTE type so it can properly construct a 4k sized
empty entry.

Instead of shifting the defines between dax.c and dax.h as they are
individually used in other code, just move them wholesale to dax.h so
they'll be available when we need them.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c            | 14 --------------
 include/linux/dax.h | 15 ++++++++++++++-
 2 files changed, 14 insertions(+), 15 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 6edd89b..c45cc4d 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -34,20 +34,6 @@
 #include <linux/iomap.h>
 #include "internal.h"
 
-/*
- * We use lowest available bit in exceptional entry for locking, other two
- * bits to determine entry type. In total 3 special bits.
- */
-#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 3)
-#define RADIX_DAX_PTE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
-#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
-#define RADIX_DAX_TYPE_MASK (RADIX_DAX_PTE | RADIX_DAX_PMD)
-#define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_TYPE_MASK)
-#define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
-#define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
-		RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE) | \
-		RADIX_TREE_EXCEPTIONAL_ENTRY))
-
 /* We choose 4096 entries - same as per-zone page wait tables */
 #define DAX_WAIT_TABLE_BITS 12
 #define DAX_WAIT_TABLE_ENTRIES (1 << DAX_WAIT_TABLE_BITS)
diff --git a/include/linux/dax.h b/include/linux/dax.h
index a3dfee4..e9ea78c 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -8,8 +8,21 @@
 
 struct iomap_ops;
 
-/* We use lowest available exceptional entry bit for locking */
+/*
+ * We use lowest available bit in exceptional entry for locking, other two
+ * bits to determine entry type. In total 3 special bits.
+ */
+#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 3)
 #define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
+#define RADIX_DAX_PTE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
+#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
+#define RADIX_DAX_TYPE_MASK (RADIX_DAX_PTE | RADIX_DAX_PMD)
+#define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_TYPE_MASK)
+#define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
+#define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
+		RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE) | \
+		RADIX_TREE_EXCEPTIONAL_ENTRY))
+
 
 ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_ops *ops);
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 13/17] dax: move RADIX_DAX_* defines to dax.h
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

The RADIX_DAX_* defines currently mostly live in fs/dax.c, with just
RADIX_DAX_ENTRY_LOCK being in include/linux/dax.h so it can be used in
mm/filemap.c.  When we add PMD support, though, mm/filemap.c will also need
access to the RADIX_DAX_PTE type so it can properly construct a 4k sized
empty entry.

Instead of shifting the defines between dax.c and dax.h as they are
individually used in other code, just move them wholesale to dax.h so
they'll be available when we need them.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c            | 14 --------------
 include/linux/dax.h | 15 ++++++++++++++-
 2 files changed, 14 insertions(+), 15 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 6edd89b..c45cc4d 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -34,20 +34,6 @@
 #include <linux/iomap.h>
 #include "internal.h"
 
-/*
- * We use lowest available bit in exceptional entry for locking, other two
- * bits to determine entry type. In total 3 special bits.
- */
-#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 3)
-#define RADIX_DAX_PTE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
-#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
-#define RADIX_DAX_TYPE_MASK (RADIX_DAX_PTE | RADIX_DAX_PMD)
-#define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_TYPE_MASK)
-#define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
-#define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
-		RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE) | \
-		RADIX_TREE_EXCEPTIONAL_ENTRY))
-
 /* We choose 4096 entries - same as per-zone page wait tables */
 #define DAX_WAIT_TABLE_BITS 12
 #define DAX_WAIT_TABLE_ENTRIES (1 << DAX_WAIT_TABLE_BITS)
diff --git a/include/linux/dax.h b/include/linux/dax.h
index a3dfee4..e9ea78c 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -8,8 +8,21 @@
 
 struct iomap_ops;
 
-/* We use lowest available exceptional entry bit for locking */
+/*
+ * We use lowest available bit in exceptional entry for locking, other two
+ * bits to determine entry type. In total 3 special bits.
+ */
+#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 3)
 #define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
+#define RADIX_DAX_PTE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
+#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
+#define RADIX_DAX_TYPE_MASK (RADIX_DAX_PTE | RADIX_DAX_PMD)
+#define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_TYPE_MASK)
+#define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
+#define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
+		RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE) | \
+		RADIX_TREE_EXCEPTIONAL_ENTRY))
+
 
 ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_ops *ops);
-- 
2.9.0

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
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^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 13/17] dax: move RADIX_DAX_* defines to dax.h
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel-u79uwXL29TY76Z2rM5mHXA
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner,
	linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw, Christoph Hellwig,
	linux-xfs-u79uwXL29TY76Z2rM5mHXA,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg, Andreas Dilger, Alexander Viro,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA, Jan Kara,
	linux-ext4-u79uwXL29TY76Z2rM5mHXA, Andrew Morton

The RADIX_DAX_* defines currently mostly live in fs/dax.c, with just
RADIX_DAX_ENTRY_LOCK being in include/linux/dax.h so it can be used in
mm/filemap.c.  When we add PMD support, though, mm/filemap.c will also need
access to the RADIX_DAX_PTE type so it can properly construct a 4k sized
empty entry.

Instead of shifting the defines between dax.c and dax.h as they are
individually used in other code, just move them wholesale to dax.h so
they'll be available when we need them.

Signed-off-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Reviewed-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
Reviewed-by: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>
---
 fs/dax.c            | 14 --------------
 include/linux/dax.h | 15 ++++++++++++++-
 2 files changed, 14 insertions(+), 15 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 6edd89b..c45cc4d 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -34,20 +34,6 @@
 #include <linux/iomap.h>
 #include "internal.h"
 
-/*
- * We use lowest available bit in exceptional entry for locking, other two
- * bits to determine entry type. In total 3 special bits.
- */
-#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 3)
-#define RADIX_DAX_PTE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
-#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
-#define RADIX_DAX_TYPE_MASK (RADIX_DAX_PTE | RADIX_DAX_PMD)
-#define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_TYPE_MASK)
-#define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
-#define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
-		RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE) | \
-		RADIX_TREE_EXCEPTIONAL_ENTRY))
-
 /* We choose 4096 entries - same as per-zone page wait tables */
 #define DAX_WAIT_TABLE_BITS 12
 #define DAX_WAIT_TABLE_ENTRIES (1 << DAX_WAIT_TABLE_BITS)
diff --git a/include/linux/dax.h b/include/linux/dax.h
index a3dfee4..e9ea78c 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -8,8 +8,21 @@
 
 struct iomap_ops;
 
-/* We use lowest available exceptional entry bit for locking */
+/*
+ * We use lowest available bit in exceptional entry for locking, other two
+ * bits to determine entry type. In total 3 special bits.
+ */
+#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 3)
 #define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
+#define RADIX_DAX_PTE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
+#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
+#define RADIX_DAX_TYPE_MASK (RADIX_DAX_PTE | RADIX_DAX_PMD)
+#define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_TYPE_MASK)
+#define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
+#define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
+		RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE) | \
+		RADIX_TREE_EXCEPTIONAL_ENTRY))
+
 
 ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_ops *ops);
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 13/17] dax: move RADIX_DAX_* defines to dax.h
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

The RADIX_DAX_* defines currently mostly live in fs/dax.c, with just
RADIX_DAX_ENTRY_LOCK being in include/linux/dax.h so it can be used in
mm/filemap.c.  When we add PMD support, though, mm/filemap.c will also need
access to the RADIX_DAX_PTE type so it can properly construct a 4k sized
empty entry.

Instead of shifting the defines between dax.c and dax.h as they are
individually used in other code, just move them wholesale to dax.h so
they'll be available when we need them.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c            | 14 --------------
 include/linux/dax.h | 15 ++++++++++++++-
 2 files changed, 14 insertions(+), 15 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 6edd89b..c45cc4d 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -34,20 +34,6 @@
 #include <linux/iomap.h>
 #include "internal.h"
 
-/*
- * We use lowest available bit in exceptional entry for locking, other two
- * bits to determine entry type. In total 3 special bits.
- */
-#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 3)
-#define RADIX_DAX_PTE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
-#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
-#define RADIX_DAX_TYPE_MASK (RADIX_DAX_PTE | RADIX_DAX_PMD)
-#define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_TYPE_MASK)
-#define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
-#define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
-		RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE) | \
-		RADIX_TREE_EXCEPTIONAL_ENTRY))
-
 /* We choose 4096 entries - same as per-zone page wait tables */
 #define DAX_WAIT_TABLE_BITS 12
 #define DAX_WAIT_TABLE_ENTRIES (1 << DAX_WAIT_TABLE_BITS)
diff --git a/include/linux/dax.h b/include/linux/dax.h
index a3dfee4..e9ea78c 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -8,8 +8,21 @@
 
 struct iomap_ops;
 
-/* We use lowest available exceptional entry bit for locking */
+/*
+ * We use lowest available bit in exceptional entry for locking, other two
+ * bits to determine entry type. In total 3 special bits.
+ */
+#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 3)
 #define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
+#define RADIX_DAX_PTE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
+#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
+#define RADIX_DAX_TYPE_MASK (RADIX_DAX_PTE | RADIX_DAX_PMD)
+#define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_TYPE_MASK)
+#define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
+#define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
+		RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE) | \
+		RADIX_TREE_EXCEPTIONAL_ENTRY))
+
 
 ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_ops *ops);
-- 
2.9.0


^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 14/17] dax: move put_(un)locked_mapping_entry() in dax.c
  2016-10-12 22:50 ` Ross Zwisler
                     ` (2 preceding siblings ...)
  (?)
@ 2016-10-12 22:50   ` Ross Zwisler
  -1 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner, linux-nvdimm,
	Christoph Hellwig, linux-xfs, linux-mm, Andreas Dilger,
	Alexander Viro, linux-fsdevel, Jan Kara, linux-ext4,
	Andrew Morton

No functional change.

The static functions put_locked_mapping_entry() and
put_unlocked_mapping_entry() will soon be used in error cases in
grab_mapping_entry(), so move their definitions above this function.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
---
 fs/dax.c | 50 +++++++++++++++++++++++++-------------------------
 1 file changed, 25 insertions(+), 25 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index c45cc4d..0582c7c 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -382,6 +382,31 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
 	}
 }
 
+static void put_locked_mapping_entry(struct address_space *mapping,
+				     pgoff_t index, void *entry)
+{
+	if (!radix_tree_exceptional_entry(entry)) {
+		unlock_page(entry);
+		put_page(entry);
+	} else {
+		dax_unlock_mapping_entry(mapping, index);
+	}
+}
+
+/*
+ * Called when we are done with radix tree entry we looked up via
+ * get_unlocked_mapping_entry() and which we didn't lock in the end.
+ */
+static void put_unlocked_mapping_entry(struct address_space *mapping,
+				       pgoff_t index, void *entry)
+{
+	if (!radix_tree_exceptional_entry(entry))
+		return;
+
+	/* We have to wake up next waiter for the radix tree entry lock */
+	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
+}
+
 /*
  * Find radix tree entry at given index. If it points to a page, return with
  * the page locked. If it points to the exceptional entry, return with the
@@ -486,31 +511,6 @@ void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
 	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
 }
 
-static void put_locked_mapping_entry(struct address_space *mapping,
-				     pgoff_t index, void *entry)
-{
-	if (!radix_tree_exceptional_entry(entry)) {
-		unlock_page(entry);
-		put_page(entry);
-	} else {
-		dax_unlock_mapping_entry(mapping, index);
-	}
-}
-
-/*
- * Called when we are done with radix tree entry we looked up via
- * get_unlocked_mapping_entry() and which we didn't lock in the end.
- */
-static void put_unlocked_mapping_entry(struct address_space *mapping,
-				       pgoff_t index, void *entry)
-{
-	if (!radix_tree_exceptional_entry(entry))
-		return;
-
-	/* We have to wake up next waiter for the radix tree entry lock */
-	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
-}
-
 /*
  * Delete exceptional DAX entry at @index from @mapping. Wait for radix tree
  * entry to get unlocked before deleting it.
-- 
2.9.0

_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 14/17] dax: move put_(un)locked_mapping_entry() in dax.c
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

No functional change.

The static functions put_locked_mapping_entry() and
put_unlocked_mapping_entry() will soon be used in error cases in
grab_mapping_entry(), so move their definitions above this function.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
---
 fs/dax.c | 50 +++++++++++++++++++++++++-------------------------
 1 file changed, 25 insertions(+), 25 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index c45cc4d..0582c7c 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -382,6 +382,31 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
 	}
 }
 
+static void put_locked_mapping_entry(struct address_space *mapping,
+				     pgoff_t index, void *entry)
+{
+	if (!radix_tree_exceptional_entry(entry)) {
+		unlock_page(entry);
+		put_page(entry);
+	} else {
+		dax_unlock_mapping_entry(mapping, index);
+	}
+}
+
+/*
+ * Called when we are done with radix tree entry we looked up via
+ * get_unlocked_mapping_entry() and which we didn't lock in the end.
+ */
+static void put_unlocked_mapping_entry(struct address_space *mapping,
+				       pgoff_t index, void *entry)
+{
+	if (!radix_tree_exceptional_entry(entry))
+		return;
+
+	/* We have to wake up next waiter for the radix tree entry lock */
+	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
+}
+
 /*
  * Find radix tree entry at given index. If it points to a page, return with
  * the page locked. If it points to the exceptional entry, return with the
@@ -486,31 +511,6 @@ void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
 	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
 }
 
-static void put_locked_mapping_entry(struct address_space *mapping,
-				     pgoff_t index, void *entry)
-{
-	if (!radix_tree_exceptional_entry(entry)) {
-		unlock_page(entry);
-		put_page(entry);
-	} else {
-		dax_unlock_mapping_entry(mapping, index);
-	}
-}
-
-/*
- * Called when we are done with radix tree entry we looked up via
- * get_unlocked_mapping_entry() and which we didn't lock in the end.
- */
-static void put_unlocked_mapping_entry(struct address_space *mapping,
-				       pgoff_t index, void *entry)
-{
-	if (!radix_tree_exceptional_entry(entry))
-		return;
-
-	/* We have to wake up next waiter for the radix tree entry lock */
-	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
-}
-
 /*
  * Delete exceptional DAX entry at @index from @mapping. Wait for radix tree
  * entry to get unlocked before deleting it.
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 14/17] dax: move put_(un)locked_mapping_entry() in dax.c
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

No functional change.

The static functions put_locked_mapping_entry() and
put_unlocked_mapping_entry() will soon be used in error cases in
grab_mapping_entry(), so move their definitions above this function.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
---
 fs/dax.c | 50 +++++++++++++++++++++++++-------------------------
 1 file changed, 25 insertions(+), 25 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index c45cc4d..0582c7c 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -382,6 +382,31 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
 	}
 }
 
+static void put_locked_mapping_entry(struct address_space *mapping,
+				     pgoff_t index, void *entry)
+{
+	if (!radix_tree_exceptional_entry(entry)) {
+		unlock_page(entry);
+		put_page(entry);
+	} else {
+		dax_unlock_mapping_entry(mapping, index);
+	}
+}
+
+/*
+ * Called when we are done with radix tree entry we looked up via
+ * get_unlocked_mapping_entry() and which we didn't lock in the end.
+ */
+static void put_unlocked_mapping_entry(struct address_space *mapping,
+				       pgoff_t index, void *entry)
+{
+	if (!radix_tree_exceptional_entry(entry))
+		return;
+
+	/* We have to wake up next waiter for the radix tree entry lock */
+	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
+}
+
 /*
  * Find radix tree entry at given index. If it points to a page, return with
  * the page locked. If it points to the exceptional entry, return with the
@@ -486,31 +511,6 @@ void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
 	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
 }
 
-static void put_locked_mapping_entry(struct address_space *mapping,
-				     pgoff_t index, void *entry)
-{
-	if (!radix_tree_exceptional_entry(entry)) {
-		unlock_page(entry);
-		put_page(entry);
-	} else {
-		dax_unlock_mapping_entry(mapping, index);
-	}
-}
-
-/*
- * Called when we are done with radix tree entry we looked up via
- * get_unlocked_mapping_entry() and which we didn't lock in the end.
- */
-static void put_unlocked_mapping_entry(struct address_space *mapping,
-				       pgoff_t index, void *entry)
-{
-	if (!radix_tree_exceptional_entry(entry))
-		return;
-
-	/* We have to wake up next waiter for the radix tree entry lock */
-	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
-}
-
 /*
  * Delete exceptional DAX entry at @index from @mapping. Wait for radix tree
  * entry to get unlocked before deleting it.
-- 
2.9.0

--
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^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 14/17] dax: move put_(un)locked_mapping_entry() in dax.c
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel-u79uwXL29TY76Z2rM5mHXA
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner,
	linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw, Christoph Hellwig,
	linux-xfs-u79uwXL29TY76Z2rM5mHXA,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg, Andreas Dilger, Alexander Viro,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA, Jan Kara,
	linux-ext4-u79uwXL29TY76Z2rM5mHXA, Andrew Morton

No functional change.

The static functions put_locked_mapping_entry() and
put_unlocked_mapping_entry() will soon be used in error cases in
grab_mapping_entry(), so move their definitions above this function.

Signed-off-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
---
 fs/dax.c | 50 +++++++++++++++++++++++++-------------------------
 1 file changed, 25 insertions(+), 25 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index c45cc4d..0582c7c 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -382,6 +382,31 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
 	}
 }
 
+static void put_locked_mapping_entry(struct address_space *mapping,
+				     pgoff_t index, void *entry)
+{
+	if (!radix_tree_exceptional_entry(entry)) {
+		unlock_page(entry);
+		put_page(entry);
+	} else {
+		dax_unlock_mapping_entry(mapping, index);
+	}
+}
+
+/*
+ * Called when we are done with radix tree entry we looked up via
+ * get_unlocked_mapping_entry() and which we didn't lock in the end.
+ */
+static void put_unlocked_mapping_entry(struct address_space *mapping,
+				       pgoff_t index, void *entry)
+{
+	if (!radix_tree_exceptional_entry(entry))
+		return;
+
+	/* We have to wake up next waiter for the radix tree entry lock */
+	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
+}
+
 /*
  * Find radix tree entry at given index. If it points to a page, return with
  * the page locked. If it points to the exceptional entry, return with the
@@ -486,31 +511,6 @@ void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
 	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
 }
 
-static void put_locked_mapping_entry(struct address_space *mapping,
-				     pgoff_t index, void *entry)
-{
-	if (!radix_tree_exceptional_entry(entry)) {
-		unlock_page(entry);
-		put_page(entry);
-	} else {
-		dax_unlock_mapping_entry(mapping, index);
-	}
-}
-
-/*
- * Called when we are done with radix tree entry we looked up via
- * get_unlocked_mapping_entry() and which we didn't lock in the end.
- */
-static void put_unlocked_mapping_entry(struct address_space *mapping,
-				       pgoff_t index, void *entry)
-{
-	if (!radix_tree_exceptional_entry(entry))
-		return;
-
-	/* We have to wake up next waiter for the radix tree entry lock */
-	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
-}
-
 /*
  * Delete exceptional DAX entry at @index from @mapping. Wait for radix tree
  * entry to get unlocked before deleting it.
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 14/17] dax: move put_(un)locked_mapping_entry() in dax.c
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

No functional change.

The static functions put_locked_mapping_entry() and
put_unlocked_mapping_entry() will soon be used in error cases in
grab_mapping_entry(), so move their definitions above this function.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
---
 fs/dax.c | 50 +++++++++++++++++++++++++-------------------------
 1 file changed, 25 insertions(+), 25 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index c45cc4d..0582c7c 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -382,6 +382,31 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
 	}
 }
 
+static void put_locked_mapping_entry(struct address_space *mapping,
+				     pgoff_t index, void *entry)
+{
+	if (!radix_tree_exceptional_entry(entry)) {
+		unlock_page(entry);
+		put_page(entry);
+	} else {
+		dax_unlock_mapping_entry(mapping, index);
+	}
+}
+
+/*
+ * Called when we are done with radix tree entry we looked up via
+ * get_unlocked_mapping_entry() and which we didn't lock in the end.
+ */
+static void put_unlocked_mapping_entry(struct address_space *mapping,
+				       pgoff_t index, void *entry)
+{
+	if (!radix_tree_exceptional_entry(entry))
+		return;
+
+	/* We have to wake up next waiter for the radix tree entry lock */
+	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
+}
+
 /*
  * Find radix tree entry at given index. If it points to a page, return with
  * the page locked. If it points to the exceptional entry, return with the
@@ -486,31 +511,6 @@ void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
 	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
 }
 
-static void put_locked_mapping_entry(struct address_space *mapping,
-				     pgoff_t index, void *entry)
-{
-	if (!radix_tree_exceptional_entry(entry)) {
-		unlock_page(entry);
-		put_page(entry);
-	} else {
-		dax_unlock_mapping_entry(mapping, index);
-	}
-}
-
-/*
- * Called when we are done with radix tree entry we looked up via
- * get_unlocked_mapping_entry() and which we didn't lock in the end.
- */
-static void put_unlocked_mapping_entry(struct address_space *mapping,
-				       pgoff_t index, void *entry)
-{
-	if (!radix_tree_exceptional_entry(entry))
-		return;
-
-	/* We have to wake up next waiter for the radix tree entry lock */
-	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
-}
-
 /*
  * Delete exceptional DAX entry at @index from @mapping. Wait for radix tree
  * entry to get unlocked before deleting it.
-- 
2.9.0


^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 15/17] dax: add struct iomap based DAX PMD support
  2016-10-12 22:50 ` Ross Zwisler
                     ` (2 preceding siblings ...)
  (?)
@ 2016-10-12 22:50   ` Ross Zwisler
  -1 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner, linux-nvdimm,
	Christoph Hellwig, linux-xfs, linux-mm, Andreas Dilger,
	Alexander Viro, linux-fsdevel, Jan Kara, linux-ext4,
	Andrew Morton

DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
locking.  This patch allows DAX PMDs to participate in the DAX radix tree
based locking scheme so that they can be re-enabled using the new struct
iomap based fault handlers.

There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
mappings that have an associated block allocation, and 4k DAX empty
entries.  The empty entries exist to provide locking for the duration of a
given page fault.

This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
entries, PMD DAX entries that have associated block allocations, and 2 MiB
DAX empty entries.

Unlike the 4k case where we insert a struct page* into the radix tree for
4k zero pages, for HZP we insert a DAX exceptional entry with the new
RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
every 2MiB hole mapping, and it doesn't make sense to have that same struct
page* with multiple entries in multiple trees.  This would cause contention
on the single page lock for the one Huge Zero Page, and it would break the
page->index and page->mapping associations that are assumed to be valid in
many other places in the kernel.

One difficult use case is when one thread is trying to use 4k entries in
radix tree for a given offset, and another thread is using 2 MiB entries
for that same offset.  The current code handles this by making the 2 MiB
user fall back to 4k entries for most cases.  This was done because it is
the simplest solution, and because the use of 2MiB pages is already
opportunistic.

If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
we run into the problem of how we lock out 4k page faults for the entire
2MiB range while we clean out the radix tree so we can insert the 2MiB
entry.  We can solve this problem if we need to, but I think that the cases
where both 2MiB entries and 4K entries are being used for the same range
will be rare enough and the gain small enough that it probably won't be
worth the complexity.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
---
 fs/dax.c            | 377 ++++++++++++++++++++++++++++++++++++++++++++++------
 include/linux/dax.h |  55 ++++++--
 mm/filemap.c        |   3 +-
 3 files changed, 385 insertions(+), 50 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 0582c7c..39b41ea 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -76,6 +76,26 @@ static void dax_unmap_atomic(struct block_device *bdev,
 	blk_queue_exit(bdev->bd_queue);
 }
 
+static int dax_is_pmd_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_PMD;
+}
+
+static int dax_is_pte_entry(void *entry)
+{
+	return !((unsigned long)entry & RADIX_DAX_PMD);
+}
+
+static int dax_is_zero_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_HZP;
+}
+
+static int dax_is_empty_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_EMPTY;
+}
+
 struct page *read_dax_sector(struct block_device *bdev, sector_t n)
 {
 	struct page *page = alloc_pages(GFP_KERNEL, 0);
@@ -281,7 +301,7 @@ static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
 	 * queue to the start of that PMD.  This ensures that all offsets in
 	 * the range covered by the PMD map to the same bit lock.
 	 */
-	if (RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
+	if (dax_is_pmd_entry(entry))
 		index &= ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1);
 
 	key->mapping = mapping;
@@ -413,36 +433,115 @@ static void put_unlocked_mapping_entry(struct address_space *mapping,
  * radix tree entry locked. If the radix tree doesn't contain given index,
  * create empty exceptional entry for the index and return with it locked.
  *
+ * When requesting an entry with size RADIX_DAX_PMD, grab_mapping_entry() will
+ * either return that locked entry or will return an error.  This error will
+ * happen if there are any 4k entries (either zero pages or DAX entries)
+ * within the 2MiB range that we are requesting.
+ *
+ * We always favor 4k entries over 2MiB entries. There isn't a flow where we
+ * evict 4k entries in order to 'upgrade' them to a 2MiB entry.  A 2MiB
+ * insertion will fail if it finds any 4k entries already in the tree, and a
+ * 4k insertion will cause an existing 2MiB entry to be unmapped and
+ * downgraded to 4k entries.  This happens for both 2MiB huge zero pages as
+ * well as 2MiB empty entries.
+ *
+ * The exception to this downgrade path is for 2MiB DAX PMD entries that have
+ * real storage backing them.  We will leave these real 2MiB DAX entries in
+ * the tree, and PTE writes will simply dirty the entire 2MiB DAX entry.
+ *
  * Note: Unlike filemap_fault() we don't honor FAULT_FLAG_RETRY flags. For
  * persistent memory the benefit is doubtful. We can add that later if we can
  * show it helps.
  */
-static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index)
+static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
+		unsigned long size_flag)
 {
+	bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */
 	void *entry, **slot;
 
 restart:
 	spin_lock_irq(&mapping->tree_lock);
 	entry = get_unlocked_mapping_entry(mapping, index, &slot);
+
+	if (entry) {
+		if (size_flag & RADIX_DAX_PMD) {
+			if (!radix_tree_exceptional_entry(entry) ||
+			    dax_is_pte_entry(entry)) {
+				put_unlocked_mapping_entry(mapping, index,
+						entry);
+				entry = ERR_PTR(-EEXIST);
+				goto out_unlock;
+			}
+		} else { /* trying to grab a PTE entry */
+			if (radix_tree_exceptional_entry(entry) &&
+			    dax_is_pmd_entry(entry) &&
+			    (dax_is_zero_entry(entry) ||
+			     dax_is_empty_entry(entry))) {
+				pmd_downgrade = true;
+			}
+		}
+	}
+
 	/* No entry for given index? Make sure radix tree is big enough. */
-	if (!entry) {
+	if (!entry || pmd_downgrade) {
 		int err;
 
+		if (pmd_downgrade) {
+			/*
+			 * Make sure 'entry' remains valid while we drop
+			 * mapping->tree_lock.
+			 */
+			entry = lock_slot(mapping, slot);
+		}
+
 		spin_unlock_irq(&mapping->tree_lock);
 		err = radix_tree_preload(
 				mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
-		if (err)
+		if (err) {
+			put_locked_mapping_entry(mapping, index, entry);
 			return ERR_PTR(err);
-		entry = (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
-			       RADIX_DAX_ENTRY_LOCK);
+		}
+
+		/*
+		 * Besides huge zero pages the only other thing that gets
+		 * downgraded are empty entries which don't need to be
+		 * unmapped.
+		 */
+		if (pmd_downgrade && dax_is_zero_entry(entry))
+			unmap_mapping_range(mapping,
+				(index << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
+
 		spin_lock_irq(&mapping->tree_lock);
-		err = radix_tree_insert(&mapping->page_tree, index, entry);
+
+		if (pmd_downgrade) {
+			radix_tree_delete(&mapping->page_tree, index);
+			mapping->nrexceptional--;
+			dax_wake_mapping_entry_waiter(mapping, index, entry,
+					true);
+		}
+
+		entry = dax_radix_locked_entry(0, size_flag | RADIX_DAX_EMPTY);
+
+		err = __radix_tree_insert(&mapping->page_tree, index,
+				dax_radix_order(entry), entry);
 		radix_tree_preload_end();
 		if (err) {
 			spin_unlock_irq(&mapping->tree_lock);
-			/* Someone already created the entry? */
-			if (err == -EEXIST)
+			/*
+			 * Someone already created the entry?  This is a
+			 * normal failure when inserting PMDs in a range
+			 * that already contains PTEs.  In that case we want
+			 * to return -EEXIST immediately.
+			 */
+			if (err == -EEXIST && !(size_flag & RADIX_DAX_PMD))
 				goto restart;
+			/*
+			 * Our insertion of a DAX PMD entry failed, most
+			 * likely because it collided with a PTE sized entry
+			 * at a different index in the PMD range.  We haven't
+			 * inserted anything into the radix tree and have no
+			 * waiters to wake.
+			 */
 			return ERR_PTR(err);
 		}
 		/* Good, we have inserted empty locked entry into the tree. */
@@ -466,6 +565,7 @@ restart:
 		return page;
 	}
 	entry = lock_slot(mapping, slot);
+ out_unlock:
 	spin_unlock_irq(&mapping->tree_lock);
 	return entry;
 }
@@ -473,9 +573,9 @@ restart:
 /*
  * We do not necessarily hold the mapping->tree_lock when we call this
  * function so it is possible that 'entry' is no longer a valid item in the
- * radix tree.  This is okay, though, because all we really need to do is to
- * find the correct waitqueue where tasks might be sleeping waiting for that
- * old 'entry' and wake them.
+ * radix tree.  This is okay because all we really need to do is to find the
+ * correct waitqueue where tasks might be waiting for that old 'entry' and
+ * wake them.
  */
 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 		pgoff_t index, void *entry, bool wake_all)
@@ -588,11 +688,17 @@ static int copy_user_dax(struct block_device *bdev, sector_t sector, size_t size
 	return 0;
 }
 
-#define DAX_PMD_INDEX(page_index) (page_index & (PMD_MASK >> PAGE_SHIFT))
-
+/*
+ * By this point grab_mapping_entry() has ensured that we have a locked entry
+ * of the appropriate size so we don't have to worry about downgrading PMDs to
+ * PTEs.  If we happen to be trying to insert a PTE and there is a PMD
+ * already in the tree, we will skip the insertion and just dirty the PMD as
+ * appropriate.
+ */
 static void *dax_insert_mapping_entry(struct address_space *mapping,
 				      struct vm_fault *vmf,
-				      void *entry, sector_t sector)
+				      void *entry, sector_t sector,
+				      unsigned long flags)
 {
 	struct radix_tree_root *page_tree = &mapping->page_tree;
 	int error = 0;
@@ -615,22 +721,35 @@ static void *dax_insert_mapping_entry(struct address_space *mapping,
 		error = radix_tree_preload(vmf->gfp_mask & ~__GFP_HIGHMEM);
 		if (error)
 			return ERR_PTR(error);
+	} else if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_HZP)) {
+		/* replacing huge zero page with PMD block mapping */
+		unmap_mapping_range(mapping,
+			(vmf->pgoff << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
 	}
 
 	spin_lock_irq(&mapping->tree_lock);
-	new_entry = (void *)((unsigned long)RADIX_DAX_ENTRY(sector, false) |
-		       RADIX_DAX_ENTRY_LOCK);
+	new_entry = dax_radix_locked_entry(sector, flags);
+
 	if (hole_fill) {
 		__delete_from_page_cache(entry, NULL);
 		/* Drop pagecache reference */
 		put_page(entry);
-		error = radix_tree_insert(page_tree, index, new_entry);
+		error = __radix_tree_insert(page_tree, index,
+				dax_radix_order(new_entry), new_entry);
 		if (error) {
 			new_entry = ERR_PTR(error);
 			goto unlock;
 		}
 		mapping->nrexceptional++;
-	} else {
+	} else if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
+		/*
+		 * Only swap our new entry into the radix tree if the current
+		 * entry is a zero page or an empty entry.  If a normal PTE or
+		 * PMD entry is already in the tree, we leave it alone.  This
+		 * means that if we are trying to insert a PTE and the
+		 * existing entry is a PMD, we will just leave the PMD in the
+		 * tree and dirty it if necessary.
+		 */
 		void **slot;
 		void *ret;
 
@@ -660,7 +779,6 @@ static int dax_writeback_one(struct block_device *bdev,
 		struct address_space *mapping, pgoff_t index, void *entry)
 {
 	struct radix_tree_root *page_tree = &mapping->page_tree;
-	int type = RADIX_DAX_TYPE(entry);
 	struct radix_tree_node *node;
 	struct blk_dax_ctl dax;
 	void **slot;
@@ -681,13 +799,21 @@ static int dax_writeback_one(struct block_device *bdev,
 	if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
 		goto unlock;
 
-	if (WARN_ON_ONCE(type != RADIX_DAX_PTE && type != RADIX_DAX_PMD)) {
+	if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
+				dax_is_zero_entry(entry))) {
 		ret = -EIO;
 		goto unlock;
 	}
 
-	dax.sector = RADIX_DAX_SECTOR(entry);
-	dax.size = (type == RADIX_DAX_PMD ? PMD_SIZE : PAGE_SIZE);
+	/*
+	 * Even if dax_writeback_mapping_range() was given a wbc->range_start
+	 * in the middle of a PMD, the 'index' we are given will be aligned to
+	 * the start index of the PMD, as will the sector we pull from
+	 * 'entry'.  This allows us to flush for PMD_SIZE and not have to
+	 * worry about partial PMD writebacks.
+	 */
+	dax.sector = dax_radix_sector(entry);
+	dax.size = PAGE_SIZE << dax_radix_order(entry);
 	spin_unlock_irq(&mapping->tree_lock);
 
 	/*
@@ -726,12 +852,11 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 		struct block_device *bdev, struct writeback_control *wbc)
 {
 	struct inode *inode = mapping->host;
-	pgoff_t start_index, end_index, pmd_index;
+	pgoff_t start_index, end_index;
 	pgoff_t indices[PAGEVEC_SIZE];
 	struct pagevec pvec;
 	bool done = false;
 	int i, ret = 0;
-	void *entry;
 
 	if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
 		return -EIO;
@@ -741,15 +866,6 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 
 	start_index = wbc->range_start >> PAGE_SHIFT;
 	end_index = wbc->range_end >> PAGE_SHIFT;
-	pmd_index = DAX_PMD_INDEX(start_index);
-
-	rcu_read_lock();
-	entry = radix_tree_lookup(&mapping->page_tree, pmd_index);
-	rcu_read_unlock();
-
-	/* see if the start of our range is covered by a PMD entry */
-	if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
-		start_index = pmd_index;
 
 	tag_pages_for_writeback(mapping, start_index, end_index);
 
@@ -794,7 +910,7 @@ static int dax_insert_mapping(struct address_space *mapping,
 		return PTR_ERR(dax.addr);
 	dax_unmap_atomic(bdev, &dax);
 
-	ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector);
+	ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector, 0);
 	if (IS_ERR(ret))
 		return PTR_ERR(ret);
 	*entryp = ret;
@@ -841,7 +957,7 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	bh.b_bdev = inode->i_sb->s_bdev;
 	bh.b_size = PAGE_SIZE;
 
-	entry = grab_mapping_entry(mapping, vmf->pgoff);
+	entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
 	if (IS_ERR(entry)) {
 		error = PTR_ERR(entry);
 		goto out;
@@ -1162,7 +1278,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	if (pos >= i_size_read(inode))
 		return VM_FAULT_SIGBUS;
 
-	entry = grab_mapping_entry(mapping, vmf->pgoff);
+	entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
 	if (IS_ERR(entry)) {
 		error = PTR_ERR(entry);
 		goto out;
@@ -1264,4 +1380,191 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	return VM_FAULT_NOPAGE | major;
 }
 EXPORT_SYMBOL_GPL(dax_iomap_fault);
+
+#ifdef CONFIG_FS_DAX_PMD
+/*
+ * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
+ * more often than one might expect in the below functions.
+ */
+#define PG_PMD_COLOUR	((PMD_SIZE >> PAGE_SHIFT) - 1)
+
+static int dax_pmd_insert_mapping(struct vm_area_struct *vma, pmd_t *pmd,
+		struct vm_fault *vmf, unsigned long address,
+		struct iomap *iomap, loff_t pos, bool write, void **entryp)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	struct block_device *bdev = iomap->bdev;
+	struct blk_dax_ctl dax = {
+		.sector = dax_iomap_sector(iomap, pos),
+		.size = PMD_SIZE,
+	};
+	long length = dax_map_atomic(bdev, &dax);
+	void *ret;
+
+	if (length < 0) /* dax_map_atomic() failed */
+		return VM_FAULT_FALLBACK;
+	if (length < PMD_SIZE)
+		goto unmap_fallback;
+	if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR)
+		goto unmap_fallback;
+	if (!pfn_t_devmap(dax.pfn))
+		goto unmap_fallback;
+
+	dax_unmap_atomic(bdev, &dax);
+
+	ret = dax_insert_mapping_entry(mapping, vmf, *entryp, dax.sector,
+			RADIX_DAX_PMD);
+	if (IS_ERR(ret))
+		return VM_FAULT_FALLBACK;
+	*entryp = ret;
+
+	return vmf_insert_pfn_pmd(vma, address, pmd, dax.pfn, write);
+
+ unmap_fallback:
+	dax_unmap_atomic(bdev, &dax);
+	return VM_FAULT_FALLBACK;
+}
+
+static int dax_pmd_load_hole(struct vm_area_struct *vma, pmd_t *pmd,
+		struct vm_fault *vmf, unsigned long address,
+		struct iomap *iomap, void **entryp)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	unsigned long pmd_addr = address & PMD_MASK;
+	struct page *zero_page;
+	spinlock_t *ptl;
+	pmd_t pmd_entry;
+	void *ret;
+
+	zero_page = get_huge_zero_page();
+
+	if (unlikely(!zero_page))
+		return VM_FAULT_FALLBACK;
+
+	ret = dax_insert_mapping_entry(mapping, vmf, *entryp, 0,
+			RADIX_DAX_PMD | RADIX_DAX_HZP);
+	if (IS_ERR(ret))
+		return VM_FAULT_FALLBACK;
+	*entryp = ret;
+
+	ptl = pmd_lock(vma->vm_mm, pmd);
+	if (!pmd_none(*pmd)) {
+		spin_unlock(ptl);
+		return VM_FAULT_FALLBACK;
+	}
+
+	pmd_entry = mk_pmd(zero_page, vma->vm_page_prot);
+	pmd_entry = pmd_mkhuge(pmd_entry);
+	set_pmd_at(vma->vm_mm, pmd_addr, pmd, pmd_entry);
+	spin_unlock(ptl);
+	return VM_FAULT_NOPAGE;
+}
+
+int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
+		pmd_t *pmd, unsigned int flags, struct iomap_ops *ops)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	unsigned long pmd_addr = address & PMD_MASK;
+	bool write = flags & FAULT_FLAG_WRITE;
+	unsigned int iomap_flags = write ? IOMAP_WRITE : 0;
+	struct inode *inode = mapping->host;
+	int result = VM_FAULT_FALLBACK;
+	struct iomap iomap = { 0 };
+	pgoff_t max_pgoff, pgoff;
+	struct vm_fault vmf;
+	void *entry;
+	loff_t pos;
+	int error;
+
+	/* Fall back to PTEs if we're going to COW */
+	if (write && !(vma->vm_flags & VM_SHARED)) {
+		split_huge_pmd(vma, pmd, address);
+		goto fallback;
+	}
+
+	/* If the PMD would extend outside the VMA */
+	if (pmd_addr < vma->vm_start)
+		goto fallback;
+	if ((pmd_addr + PMD_SIZE) > vma->vm_end)
+		goto fallback;
+
+	/*
+	 * Check whether offset isn't beyond end of file now. Caller is
+	 * supposed to hold locks serializing us with truncate / punch hole so
+	 * this is a reliable test.
+	 */
+	pgoff = linear_page_index(vma, pmd_addr);
+	max_pgoff = (i_size_read(inode) - 1) >> PAGE_SHIFT;
+
+	if (pgoff > max_pgoff)
+		return VM_FAULT_SIGBUS;
+
+	/* If the PMD would extend beyond the file size */
+	if ((pgoff | PG_PMD_COLOUR) > max_pgoff)
+		goto fallback;
+
+	/*
+	 * grab_mapping_entry() will make sure we get a 2M empty entry, a DAX
+	 * PMD or a HZP entry.  If it can't (because a 4k page is already in
+	 * the tree, for instance), it will return -EEXIST and we just fall
+	 * back to 4k entries.
+	 */
+	entry = grab_mapping_entry(mapping, pgoff, RADIX_DAX_PMD);
+	if (IS_ERR(entry))
+		goto fallback;
+
+	/*
+	 * Note that we don't use iomap_apply here.  We aren't doing I/O, only
+	 * setting up a mapping, so really we're using iomap_begin() as a way
+	 * to look up our filesystem block.
+	 */
+	pos = (loff_t)pgoff << PAGE_SHIFT;
+	error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap);
+	if (error)
+		goto unlock_entry;
+	if (iomap.offset + iomap.length < pos + PMD_SIZE)
+		goto finish_iomap;
+
+	vmf.pgoff = pgoff;
+	vmf.flags = flags;
+	vmf.gfp_mask = mapping_gfp_mask(mapping) | __GFP_IO;
+
+	switch (iomap.type) {
+	case IOMAP_MAPPED:
+		result = dax_pmd_insert_mapping(vma, pmd, &vmf, address,
+				&iomap, pos, write, &entry);
+		break;
+	case IOMAP_UNWRITTEN:
+	case IOMAP_HOLE:
+		if (WARN_ON_ONCE(write))
+			goto finish_iomap;
+		result = dax_pmd_load_hole(vma, pmd, &vmf, address, &iomap,
+				&entry);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		break;
+	}
+
+ finish_iomap:
+	if (ops->iomap_end) {
+		if (result == VM_FAULT_FALLBACK) {
+			ops->iomap_end(inode, pos, PMD_SIZE, 0, iomap_flags,
+					&iomap);
+		} else {
+			error = ops->iomap_end(inode, pos, PMD_SIZE, PMD_SIZE,
+					iomap_flags, &iomap);
+			if (error)
+				result = VM_FAULT_FALLBACK;
+		}
+	}
+ unlock_entry:
+	put_locked_mapping_entry(mapping, pgoff, entry);
+ fallback:
+	if (result == VM_FAULT_FALLBACK)
+		count_vm_event(THP_FAULT_FALLBACK);
+	return result;
+}
+EXPORT_SYMBOL_GPL(dax_iomap_pmd_fault);
+#endif /* CONFIG_FS_DAX_PMD */
 #endif /* CONFIG_FS_IOMAP */
diff --git a/include/linux/dax.h b/include/linux/dax.h
index e9ea78c..8d1a5c4 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -9,20 +9,32 @@
 struct iomap_ops;
 
 /*
- * We use lowest available bit in exceptional entry for locking, other two
- * bits to determine entry type. In total 3 special bits.
+ * We use lowest available bit in exceptional entry for locking, one bit for
+ * the entry size (PMD) and two more to tell us if the entry is a huge zero
+ * page (HZP) or an empty entry that is just used for locking.  In total four
+ * special bits.
+ *
+ * If the PMD bit isn't set the entry has size PAGE_SIZE, and if the HZP and
+ * EMPTY bits aren't set the entry is a normal DAX entry with a filesystem
+ * block allocation.
  */
-#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 3)
+#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 4)
 #define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
-#define RADIX_DAX_PTE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
-#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
-#define RADIX_DAX_TYPE_MASK (RADIX_DAX_PTE | RADIX_DAX_PMD)
-#define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_TYPE_MASK)
-#define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
-#define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
-		RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE) | \
-		RADIX_TREE_EXCEPTIONAL_ENTRY))
+#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
+#define RADIX_DAX_HZP (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
+#define RADIX_DAX_EMPTY (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 3))
 
+static inline unsigned long dax_radix_sector(void *entry)
+{
+	return (unsigned long)entry >> RADIX_DAX_SHIFT;
+}
+
+static inline void *dax_radix_locked_entry(sector_t sector, unsigned long flags)
+{
+	return (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY | flags |
+			((unsigned long)sector << RADIX_DAX_SHIFT) |
+			RADIX_DAX_ENTRY_LOCK);
+}
 
 ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_ops *ops);
@@ -67,6 +79,27 @@ static inline int dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
 	return VM_FAULT_FALLBACK;
 }
 
+#ifdef CONFIG_FS_DAX_PMD
+static inline unsigned int dax_radix_order(void *entry)
+{
+	if ((unsigned long)entry & RADIX_DAX_PMD)
+		return PMD_SHIFT - PAGE_SHIFT;
+	return 0;
+}
+int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
+		pmd_t *pmd, unsigned int flags, struct iomap_ops *ops);
+#else
+static inline unsigned int dax_radix_order(void *entry)
+{
+	return 0;
+}
+static inline int dax_iomap_pmd_fault(struct vm_area_struct *vma,
+		unsigned long address, pmd_t *pmd, unsigned int flags,
+		struct iomap_ops *ops)
+{
+	return VM_FAULT_FALLBACK;
+}
+#endif
 int dax_pfn_mkwrite(struct vm_area_struct *, struct vm_fault *);
 #define dax_mkwrite(vma, vmf, gb)	dax_fault(vma, vmf, gb)
 
diff --git a/mm/filemap.c b/mm/filemap.c
index a596462..592e6e9 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -611,8 +611,7 @@ static int page_cache_tree_insert(struct address_space *mapping,
 		} else {
 			/* DAX can replace empty locked entry with a hole */
 			WARN_ON_ONCE(p !=
-				(void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
-					 RADIX_DAX_ENTRY_LOCK));
+				dax_radix_locked_entry(0, RADIX_DAX_EMPTY));
 			/* DAX accounts exceptional entries as normal pages */
 			if (node)
 				workingset_node_pages_dec(node);
-- 
2.9.0

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^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 15/17] dax: add struct iomap based DAX PMD support
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
locking.  This patch allows DAX PMDs to participate in the DAX radix tree
based locking scheme so that they can be re-enabled using the new struct
iomap based fault handlers.

There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
mappings that have an associated block allocation, and 4k DAX empty
entries.  The empty entries exist to provide locking for the duration of a
given page fault.

This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
entries, PMD DAX entries that have associated block allocations, and 2 MiB
DAX empty entries.

Unlike the 4k case where we insert a struct page* into the radix tree for
4k zero pages, for HZP we insert a DAX exceptional entry with the new
RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
every 2MiB hole mapping, and it doesn't make sense to have that same struct
page* with multiple entries in multiple trees.  This would cause contention
on the single page lock for the one Huge Zero Page, and it would break the
page->index and page->mapping associations that are assumed to be valid in
many other places in the kernel.

One difficult use case is when one thread is trying to use 4k entries in
radix tree for a given offset, and another thread is using 2 MiB entries
for that same offset.  The current code handles this by making the 2 MiB
user fall back to 4k entries for most cases.  This was done because it is
the simplest solution, and because the use of 2MiB pages is already
opportunistic.

If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
we run into the problem of how we lock out 4k page faults for the entire
2MiB range while we clean out the radix tree so we can insert the 2MiB
entry.  We can solve this problem if we need to, but I think that the cases
where both 2MiB entries and 4K entries are being used for the same range
will be rare enough and the gain small enough that it probably won't be
worth the complexity.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
---
 fs/dax.c            | 377 ++++++++++++++++++++++++++++++++++++++++++++++------
 include/linux/dax.h |  55 ++++++--
 mm/filemap.c        |   3 +-
 3 files changed, 385 insertions(+), 50 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 0582c7c..39b41ea 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -76,6 +76,26 @@ static void dax_unmap_atomic(struct block_device *bdev,
 	blk_queue_exit(bdev->bd_queue);
 }
 
+static int dax_is_pmd_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_PMD;
+}
+
+static int dax_is_pte_entry(void *entry)
+{
+	return !((unsigned long)entry & RADIX_DAX_PMD);
+}
+
+static int dax_is_zero_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_HZP;
+}
+
+static int dax_is_empty_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_EMPTY;
+}
+
 struct page *read_dax_sector(struct block_device *bdev, sector_t n)
 {
 	struct page *page = alloc_pages(GFP_KERNEL, 0);
@@ -281,7 +301,7 @@ static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
 	 * queue to the start of that PMD.  This ensures that all offsets in
 	 * the range covered by the PMD map to the same bit lock.
 	 */
-	if (RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
+	if (dax_is_pmd_entry(entry))
 		index &= ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1);
 
 	key->mapping = mapping;
@@ -413,36 +433,115 @@ static void put_unlocked_mapping_entry(struct address_space *mapping,
  * radix tree entry locked. If the radix tree doesn't contain given index,
  * create empty exceptional entry for the index and return with it locked.
  *
+ * When requesting an entry with size RADIX_DAX_PMD, grab_mapping_entry() will
+ * either return that locked entry or will return an error.  This error will
+ * happen if there are any 4k entries (either zero pages or DAX entries)
+ * within the 2MiB range that we are requesting.
+ *
+ * We always favor 4k entries over 2MiB entries. There isn't a flow where we
+ * evict 4k entries in order to 'upgrade' them to a 2MiB entry.  A 2MiB
+ * insertion will fail if it finds any 4k entries already in the tree, and a
+ * 4k insertion will cause an existing 2MiB entry to be unmapped and
+ * downgraded to 4k entries.  This happens for both 2MiB huge zero pages as
+ * well as 2MiB empty entries.
+ *
+ * The exception to this downgrade path is for 2MiB DAX PMD entries that have
+ * real storage backing them.  We will leave these real 2MiB DAX entries in
+ * the tree, and PTE writes will simply dirty the entire 2MiB DAX entry.
+ *
  * Note: Unlike filemap_fault() we don't honor FAULT_FLAG_RETRY flags. For
  * persistent memory the benefit is doubtful. We can add that later if we can
  * show it helps.
  */
-static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index)
+static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
+		unsigned long size_flag)
 {
+	bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */
 	void *entry, **slot;
 
 restart:
 	spin_lock_irq(&mapping->tree_lock);
 	entry = get_unlocked_mapping_entry(mapping, index, &slot);
+
+	if (entry) {
+		if (size_flag & RADIX_DAX_PMD) {
+			if (!radix_tree_exceptional_entry(entry) ||
+			    dax_is_pte_entry(entry)) {
+				put_unlocked_mapping_entry(mapping, index,
+						entry);
+				entry = ERR_PTR(-EEXIST);
+				goto out_unlock;
+			}
+		} else { /* trying to grab a PTE entry */
+			if (radix_tree_exceptional_entry(entry) &&
+			    dax_is_pmd_entry(entry) &&
+			    (dax_is_zero_entry(entry) ||
+			     dax_is_empty_entry(entry))) {
+				pmd_downgrade = true;
+			}
+		}
+	}
+
 	/* No entry for given index? Make sure radix tree is big enough. */
-	if (!entry) {
+	if (!entry || pmd_downgrade) {
 		int err;
 
+		if (pmd_downgrade) {
+			/*
+			 * Make sure 'entry' remains valid while we drop
+			 * mapping->tree_lock.
+			 */
+			entry = lock_slot(mapping, slot);
+		}
+
 		spin_unlock_irq(&mapping->tree_lock);
 		err = radix_tree_preload(
 				mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
-		if (err)
+		if (err) {
+			put_locked_mapping_entry(mapping, index, entry);
 			return ERR_PTR(err);
-		entry = (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
-			       RADIX_DAX_ENTRY_LOCK);
+		}
+
+		/*
+		 * Besides huge zero pages the only other thing that gets
+		 * downgraded are empty entries which don't need to be
+		 * unmapped.
+		 */
+		if (pmd_downgrade && dax_is_zero_entry(entry))
+			unmap_mapping_range(mapping,
+				(index << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
+
 		spin_lock_irq(&mapping->tree_lock);
-		err = radix_tree_insert(&mapping->page_tree, index, entry);
+
+		if (pmd_downgrade) {
+			radix_tree_delete(&mapping->page_tree, index);
+			mapping->nrexceptional--;
+			dax_wake_mapping_entry_waiter(mapping, index, entry,
+					true);
+		}
+
+		entry = dax_radix_locked_entry(0, size_flag | RADIX_DAX_EMPTY);
+
+		err = __radix_tree_insert(&mapping->page_tree, index,
+				dax_radix_order(entry), entry);
 		radix_tree_preload_end();
 		if (err) {
 			spin_unlock_irq(&mapping->tree_lock);
-			/* Someone already created the entry? */
-			if (err == -EEXIST)
+			/*
+			 * Someone already created the entry?  This is a
+			 * normal failure when inserting PMDs in a range
+			 * that already contains PTEs.  In that case we want
+			 * to return -EEXIST immediately.
+			 */
+			if (err == -EEXIST && !(size_flag & RADIX_DAX_PMD))
 				goto restart;
+			/*
+			 * Our insertion of a DAX PMD entry failed, most
+			 * likely because it collided with a PTE sized entry
+			 * at a different index in the PMD range.  We haven't
+			 * inserted anything into the radix tree and have no
+			 * waiters to wake.
+			 */
 			return ERR_PTR(err);
 		}
 		/* Good, we have inserted empty locked entry into the tree. */
@@ -466,6 +565,7 @@ restart:
 		return page;
 	}
 	entry = lock_slot(mapping, slot);
+ out_unlock:
 	spin_unlock_irq(&mapping->tree_lock);
 	return entry;
 }
@@ -473,9 +573,9 @@ restart:
 /*
  * We do not necessarily hold the mapping->tree_lock when we call this
  * function so it is possible that 'entry' is no longer a valid item in the
- * radix tree.  This is okay, though, because all we really need to do is to
- * find the correct waitqueue where tasks might be sleeping waiting for that
- * old 'entry' and wake them.
+ * radix tree.  This is okay because all we really need to do is to find the
+ * correct waitqueue where tasks might be waiting for that old 'entry' and
+ * wake them.
  */
 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 		pgoff_t index, void *entry, bool wake_all)
@@ -588,11 +688,17 @@ static int copy_user_dax(struct block_device *bdev, sector_t sector, size_t size
 	return 0;
 }
 
-#define DAX_PMD_INDEX(page_index) (page_index & (PMD_MASK >> PAGE_SHIFT))
-
+/*
+ * By this point grab_mapping_entry() has ensured that we have a locked entry
+ * of the appropriate size so we don't have to worry about downgrading PMDs to
+ * PTEs.  If we happen to be trying to insert a PTE and there is a PMD
+ * already in the tree, we will skip the insertion and just dirty the PMD as
+ * appropriate.
+ */
 static void *dax_insert_mapping_entry(struct address_space *mapping,
 				      struct vm_fault *vmf,
-				      void *entry, sector_t sector)
+				      void *entry, sector_t sector,
+				      unsigned long flags)
 {
 	struct radix_tree_root *page_tree = &mapping->page_tree;
 	int error = 0;
@@ -615,22 +721,35 @@ static void *dax_insert_mapping_entry(struct address_space *mapping,
 		error = radix_tree_preload(vmf->gfp_mask & ~__GFP_HIGHMEM);
 		if (error)
 			return ERR_PTR(error);
+	} else if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_HZP)) {
+		/* replacing huge zero page with PMD block mapping */
+		unmap_mapping_range(mapping,
+			(vmf->pgoff << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
 	}
 
 	spin_lock_irq(&mapping->tree_lock);
-	new_entry = (void *)((unsigned long)RADIX_DAX_ENTRY(sector, false) |
-		       RADIX_DAX_ENTRY_LOCK);
+	new_entry = dax_radix_locked_entry(sector, flags);
+
 	if (hole_fill) {
 		__delete_from_page_cache(entry, NULL);
 		/* Drop pagecache reference */
 		put_page(entry);
-		error = radix_tree_insert(page_tree, index, new_entry);
+		error = __radix_tree_insert(page_tree, index,
+				dax_radix_order(new_entry), new_entry);
 		if (error) {
 			new_entry = ERR_PTR(error);
 			goto unlock;
 		}
 		mapping->nrexceptional++;
-	} else {
+	} else if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
+		/*
+		 * Only swap our new entry into the radix tree if the current
+		 * entry is a zero page or an empty entry.  If a normal PTE or
+		 * PMD entry is already in the tree, we leave it alone.  This
+		 * means that if we are trying to insert a PTE and the
+		 * existing entry is a PMD, we will just leave the PMD in the
+		 * tree and dirty it if necessary.
+		 */
 		void **slot;
 		void *ret;
 
@@ -660,7 +779,6 @@ static int dax_writeback_one(struct block_device *bdev,
 		struct address_space *mapping, pgoff_t index, void *entry)
 {
 	struct radix_tree_root *page_tree = &mapping->page_tree;
-	int type = RADIX_DAX_TYPE(entry);
 	struct radix_tree_node *node;
 	struct blk_dax_ctl dax;
 	void **slot;
@@ -681,13 +799,21 @@ static int dax_writeback_one(struct block_device *bdev,
 	if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
 		goto unlock;
 
-	if (WARN_ON_ONCE(type != RADIX_DAX_PTE && type != RADIX_DAX_PMD)) {
+	if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
+				dax_is_zero_entry(entry))) {
 		ret = -EIO;
 		goto unlock;
 	}
 
-	dax.sector = RADIX_DAX_SECTOR(entry);
-	dax.size = (type == RADIX_DAX_PMD ? PMD_SIZE : PAGE_SIZE);
+	/*
+	 * Even if dax_writeback_mapping_range() was given a wbc->range_start
+	 * in the middle of a PMD, the 'index' we are given will be aligned to
+	 * the start index of the PMD, as will the sector we pull from
+	 * 'entry'.  This allows us to flush for PMD_SIZE and not have to
+	 * worry about partial PMD writebacks.
+	 */
+	dax.sector = dax_radix_sector(entry);
+	dax.size = PAGE_SIZE << dax_radix_order(entry);
 	spin_unlock_irq(&mapping->tree_lock);
 
 	/*
@@ -726,12 +852,11 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 		struct block_device *bdev, struct writeback_control *wbc)
 {
 	struct inode *inode = mapping->host;
-	pgoff_t start_index, end_index, pmd_index;
+	pgoff_t start_index, end_index;
 	pgoff_t indices[PAGEVEC_SIZE];
 	struct pagevec pvec;
 	bool done = false;
 	int i, ret = 0;
-	void *entry;
 
 	if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
 		return -EIO;
@@ -741,15 +866,6 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 
 	start_index = wbc->range_start >> PAGE_SHIFT;
 	end_index = wbc->range_end >> PAGE_SHIFT;
-	pmd_index = DAX_PMD_INDEX(start_index);
-
-	rcu_read_lock();
-	entry = radix_tree_lookup(&mapping->page_tree, pmd_index);
-	rcu_read_unlock();
-
-	/* see if the start of our range is covered by a PMD entry */
-	if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
-		start_index = pmd_index;
 
 	tag_pages_for_writeback(mapping, start_index, end_index);
 
@@ -794,7 +910,7 @@ static int dax_insert_mapping(struct address_space *mapping,
 		return PTR_ERR(dax.addr);
 	dax_unmap_atomic(bdev, &dax);
 
-	ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector);
+	ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector, 0);
 	if (IS_ERR(ret))
 		return PTR_ERR(ret);
 	*entryp = ret;
@@ -841,7 +957,7 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	bh.b_bdev = inode->i_sb->s_bdev;
 	bh.b_size = PAGE_SIZE;
 
-	entry = grab_mapping_entry(mapping, vmf->pgoff);
+	entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
 	if (IS_ERR(entry)) {
 		error = PTR_ERR(entry);
 		goto out;
@@ -1162,7 +1278,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	if (pos >= i_size_read(inode))
 		return VM_FAULT_SIGBUS;
 
-	entry = grab_mapping_entry(mapping, vmf->pgoff);
+	entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
 	if (IS_ERR(entry)) {
 		error = PTR_ERR(entry);
 		goto out;
@@ -1264,4 +1380,191 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	return VM_FAULT_NOPAGE | major;
 }
 EXPORT_SYMBOL_GPL(dax_iomap_fault);
+
+#ifdef CONFIG_FS_DAX_PMD
+/*
+ * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
+ * more often than one might expect in the below functions.
+ */
+#define PG_PMD_COLOUR	((PMD_SIZE >> PAGE_SHIFT) - 1)
+
+static int dax_pmd_insert_mapping(struct vm_area_struct *vma, pmd_t *pmd,
+		struct vm_fault *vmf, unsigned long address,
+		struct iomap *iomap, loff_t pos, bool write, void **entryp)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	struct block_device *bdev = iomap->bdev;
+	struct blk_dax_ctl dax = {
+		.sector = dax_iomap_sector(iomap, pos),
+		.size = PMD_SIZE,
+	};
+	long length = dax_map_atomic(bdev, &dax);
+	void *ret;
+
+	if (length < 0) /* dax_map_atomic() failed */
+		return VM_FAULT_FALLBACK;
+	if (length < PMD_SIZE)
+		goto unmap_fallback;
+	if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR)
+		goto unmap_fallback;
+	if (!pfn_t_devmap(dax.pfn))
+		goto unmap_fallback;
+
+	dax_unmap_atomic(bdev, &dax);
+
+	ret = dax_insert_mapping_entry(mapping, vmf, *entryp, dax.sector,
+			RADIX_DAX_PMD);
+	if (IS_ERR(ret))
+		return VM_FAULT_FALLBACK;
+	*entryp = ret;
+
+	return vmf_insert_pfn_pmd(vma, address, pmd, dax.pfn, write);
+
+ unmap_fallback:
+	dax_unmap_atomic(bdev, &dax);
+	return VM_FAULT_FALLBACK;
+}
+
+static int dax_pmd_load_hole(struct vm_area_struct *vma, pmd_t *pmd,
+		struct vm_fault *vmf, unsigned long address,
+		struct iomap *iomap, void **entryp)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	unsigned long pmd_addr = address & PMD_MASK;
+	struct page *zero_page;
+	spinlock_t *ptl;
+	pmd_t pmd_entry;
+	void *ret;
+
+	zero_page = get_huge_zero_page();
+
+	if (unlikely(!zero_page))
+		return VM_FAULT_FALLBACK;
+
+	ret = dax_insert_mapping_entry(mapping, vmf, *entryp, 0,
+			RADIX_DAX_PMD | RADIX_DAX_HZP);
+	if (IS_ERR(ret))
+		return VM_FAULT_FALLBACK;
+	*entryp = ret;
+
+	ptl = pmd_lock(vma->vm_mm, pmd);
+	if (!pmd_none(*pmd)) {
+		spin_unlock(ptl);
+		return VM_FAULT_FALLBACK;
+	}
+
+	pmd_entry = mk_pmd(zero_page, vma->vm_page_prot);
+	pmd_entry = pmd_mkhuge(pmd_entry);
+	set_pmd_at(vma->vm_mm, pmd_addr, pmd, pmd_entry);
+	spin_unlock(ptl);
+	return VM_FAULT_NOPAGE;
+}
+
+int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
+		pmd_t *pmd, unsigned int flags, struct iomap_ops *ops)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	unsigned long pmd_addr = address & PMD_MASK;
+	bool write = flags & FAULT_FLAG_WRITE;
+	unsigned int iomap_flags = write ? IOMAP_WRITE : 0;
+	struct inode *inode = mapping->host;
+	int result = VM_FAULT_FALLBACK;
+	struct iomap iomap = { 0 };
+	pgoff_t max_pgoff, pgoff;
+	struct vm_fault vmf;
+	void *entry;
+	loff_t pos;
+	int error;
+
+	/* Fall back to PTEs if we're going to COW */
+	if (write && !(vma->vm_flags & VM_SHARED)) {
+		split_huge_pmd(vma, pmd, address);
+		goto fallback;
+	}
+
+	/* If the PMD would extend outside the VMA */
+	if (pmd_addr < vma->vm_start)
+		goto fallback;
+	if ((pmd_addr + PMD_SIZE) > vma->vm_end)
+		goto fallback;
+
+	/*
+	 * Check whether offset isn't beyond end of file now. Caller is
+	 * supposed to hold locks serializing us with truncate / punch hole so
+	 * this is a reliable test.
+	 */
+	pgoff = linear_page_index(vma, pmd_addr);
+	max_pgoff = (i_size_read(inode) - 1) >> PAGE_SHIFT;
+
+	if (pgoff > max_pgoff)
+		return VM_FAULT_SIGBUS;
+
+	/* If the PMD would extend beyond the file size */
+	if ((pgoff | PG_PMD_COLOUR) > max_pgoff)
+		goto fallback;
+
+	/*
+	 * grab_mapping_entry() will make sure we get a 2M empty entry, a DAX
+	 * PMD or a HZP entry.  If it can't (because a 4k page is already in
+	 * the tree, for instance), it will return -EEXIST and we just fall
+	 * back to 4k entries.
+	 */
+	entry = grab_mapping_entry(mapping, pgoff, RADIX_DAX_PMD);
+	if (IS_ERR(entry))
+		goto fallback;
+
+	/*
+	 * Note that we don't use iomap_apply here.  We aren't doing I/O, only
+	 * setting up a mapping, so really we're using iomap_begin() as a way
+	 * to look up our filesystem block.
+	 */
+	pos = (loff_t)pgoff << PAGE_SHIFT;
+	error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap);
+	if (error)
+		goto unlock_entry;
+	if (iomap.offset + iomap.length < pos + PMD_SIZE)
+		goto finish_iomap;
+
+	vmf.pgoff = pgoff;
+	vmf.flags = flags;
+	vmf.gfp_mask = mapping_gfp_mask(mapping) | __GFP_IO;
+
+	switch (iomap.type) {
+	case IOMAP_MAPPED:
+		result = dax_pmd_insert_mapping(vma, pmd, &vmf, address,
+				&iomap, pos, write, &entry);
+		break;
+	case IOMAP_UNWRITTEN:
+	case IOMAP_HOLE:
+		if (WARN_ON_ONCE(write))
+			goto finish_iomap;
+		result = dax_pmd_load_hole(vma, pmd, &vmf, address, &iomap,
+				&entry);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		break;
+	}
+
+ finish_iomap:
+	if (ops->iomap_end) {
+		if (result == VM_FAULT_FALLBACK) {
+			ops->iomap_end(inode, pos, PMD_SIZE, 0, iomap_flags,
+					&iomap);
+		} else {
+			error = ops->iomap_end(inode, pos, PMD_SIZE, PMD_SIZE,
+					iomap_flags, &iomap);
+			if (error)
+				result = VM_FAULT_FALLBACK;
+		}
+	}
+ unlock_entry:
+	put_locked_mapping_entry(mapping, pgoff, entry);
+ fallback:
+	if (result == VM_FAULT_FALLBACK)
+		count_vm_event(THP_FAULT_FALLBACK);
+	return result;
+}
+EXPORT_SYMBOL_GPL(dax_iomap_pmd_fault);
+#endif /* CONFIG_FS_DAX_PMD */
 #endif /* CONFIG_FS_IOMAP */
diff --git a/include/linux/dax.h b/include/linux/dax.h
index e9ea78c..8d1a5c4 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -9,20 +9,32 @@
 struct iomap_ops;
 
 /*
- * We use lowest available bit in exceptional entry for locking, other two
- * bits to determine entry type. In total 3 special bits.
+ * We use lowest available bit in exceptional entry for locking, one bit for
+ * the entry size (PMD) and two more to tell us if the entry is a huge zero
+ * page (HZP) or an empty entry that is just used for locking.  In total four
+ * special bits.
+ *
+ * If the PMD bit isn't set the entry has size PAGE_SIZE, and if the HZP and
+ * EMPTY bits aren't set the entry is a normal DAX entry with a filesystem
+ * block allocation.
  */
-#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 3)
+#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 4)
 #define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
-#define RADIX_DAX_PTE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
-#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
-#define RADIX_DAX_TYPE_MASK (RADIX_DAX_PTE | RADIX_DAX_PMD)
-#define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_TYPE_MASK)
-#define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
-#define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
-		RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE) | \
-		RADIX_TREE_EXCEPTIONAL_ENTRY))
+#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
+#define RADIX_DAX_HZP (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
+#define RADIX_DAX_EMPTY (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 3))
 
+static inline unsigned long dax_radix_sector(void *entry)
+{
+	return (unsigned long)entry >> RADIX_DAX_SHIFT;
+}
+
+static inline void *dax_radix_locked_entry(sector_t sector, unsigned long flags)
+{
+	return (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY | flags |
+			((unsigned long)sector << RADIX_DAX_SHIFT) |
+			RADIX_DAX_ENTRY_LOCK);
+}
 
 ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_ops *ops);
@@ -67,6 +79,27 @@ static inline int dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
 	return VM_FAULT_FALLBACK;
 }
 
+#ifdef CONFIG_FS_DAX_PMD
+static inline unsigned int dax_radix_order(void *entry)
+{
+	if ((unsigned long)entry & RADIX_DAX_PMD)
+		return PMD_SHIFT - PAGE_SHIFT;
+	return 0;
+}
+int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
+		pmd_t *pmd, unsigned int flags, struct iomap_ops *ops);
+#else
+static inline unsigned int dax_radix_order(void *entry)
+{
+	return 0;
+}
+static inline int dax_iomap_pmd_fault(struct vm_area_struct *vma,
+		unsigned long address, pmd_t *pmd, unsigned int flags,
+		struct iomap_ops *ops)
+{
+	return VM_FAULT_FALLBACK;
+}
+#endif
 int dax_pfn_mkwrite(struct vm_area_struct *, struct vm_fault *);
 #define dax_mkwrite(vma, vmf, gb)	dax_fault(vma, vmf, gb)
 
diff --git a/mm/filemap.c b/mm/filemap.c
index a596462..592e6e9 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -611,8 +611,7 @@ static int page_cache_tree_insert(struct address_space *mapping,
 		} else {
 			/* DAX can replace empty locked entry with a hole */
 			WARN_ON_ONCE(p !=
-				(void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
-					 RADIX_DAX_ENTRY_LOCK));
+				dax_radix_locked_entry(0, RADIX_DAX_EMPTY));
 			/* DAX accounts exceptional entries as normal pages */
 			if (node)
 				workingset_node_pages_dec(node);
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 15/17] dax: add struct iomap based DAX PMD support
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
locking.  This patch allows DAX PMDs to participate in the DAX radix tree
based locking scheme so that they can be re-enabled using the new struct
iomap based fault handlers.

There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
mappings that have an associated block allocation, and 4k DAX empty
entries.  The empty entries exist to provide locking for the duration of a
given page fault.

This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
entries, PMD DAX entries that have associated block allocations, and 2 MiB
DAX empty entries.

Unlike the 4k case where we insert a struct page* into the radix tree for
4k zero pages, for HZP we insert a DAX exceptional entry with the new
RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
every 2MiB hole mapping, and it doesn't make sense to have that same struct
page* with multiple entries in multiple trees.  This would cause contention
on the single page lock for the one Huge Zero Page, and it would break the
page->index and page->mapping associations that are assumed to be valid in
many other places in the kernel.

One difficult use case is when one thread is trying to use 4k entries in
radix tree for a given offset, and another thread is using 2 MiB entries
for that same offset.  The current code handles this by making the 2 MiB
user fall back to 4k entries for most cases.  This was done because it is
the simplest solution, and because the use of 2MiB pages is already
opportunistic.

If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
we run into the problem of how we lock out 4k page faults for the entire
2MiB range while we clean out the radix tree so we can insert the 2MiB
entry.  We can solve this problem if we need to, but I think that the cases
where both 2MiB entries and 4K entries are being used for the same range
will be rare enough and the gain small enough that it probably won't be
worth the complexity.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
---
 fs/dax.c            | 377 ++++++++++++++++++++++++++++++++++++++++++++++------
 include/linux/dax.h |  55 ++++++--
 mm/filemap.c        |   3 +-
 3 files changed, 385 insertions(+), 50 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 0582c7c..39b41ea 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -76,6 +76,26 @@ static void dax_unmap_atomic(struct block_device *bdev,
 	blk_queue_exit(bdev->bd_queue);
 }
 
+static int dax_is_pmd_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_PMD;
+}
+
+static int dax_is_pte_entry(void *entry)
+{
+	return !((unsigned long)entry & RADIX_DAX_PMD);
+}
+
+static int dax_is_zero_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_HZP;
+}
+
+static int dax_is_empty_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_EMPTY;
+}
+
 struct page *read_dax_sector(struct block_device *bdev, sector_t n)
 {
 	struct page *page = alloc_pages(GFP_KERNEL, 0);
@@ -281,7 +301,7 @@ static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
 	 * queue to the start of that PMD.  This ensures that all offsets in
 	 * the range covered by the PMD map to the same bit lock.
 	 */
-	if (RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
+	if (dax_is_pmd_entry(entry))
 		index &= ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1);
 
 	key->mapping = mapping;
@@ -413,36 +433,115 @@ static void put_unlocked_mapping_entry(struct address_space *mapping,
  * radix tree entry locked. If the radix tree doesn't contain given index,
  * create empty exceptional entry for the index and return with it locked.
  *
+ * When requesting an entry with size RADIX_DAX_PMD, grab_mapping_entry() will
+ * either return that locked entry or will return an error.  This error will
+ * happen if there are any 4k entries (either zero pages or DAX entries)
+ * within the 2MiB range that we are requesting.
+ *
+ * We always favor 4k entries over 2MiB entries. There isn't a flow where we
+ * evict 4k entries in order to 'upgrade' them to a 2MiB entry.  A 2MiB
+ * insertion will fail if it finds any 4k entries already in the tree, and a
+ * 4k insertion will cause an existing 2MiB entry to be unmapped and
+ * downgraded to 4k entries.  This happens for both 2MiB huge zero pages as
+ * well as 2MiB empty entries.
+ *
+ * The exception to this downgrade path is for 2MiB DAX PMD entries that have
+ * real storage backing them.  We will leave these real 2MiB DAX entries in
+ * the tree, and PTE writes will simply dirty the entire 2MiB DAX entry.
+ *
  * Note: Unlike filemap_fault() we don't honor FAULT_FLAG_RETRY flags. For
  * persistent memory the benefit is doubtful. We can add that later if we can
  * show it helps.
  */
-static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index)
+static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
+		unsigned long size_flag)
 {
+	bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */
 	void *entry, **slot;
 
 restart:
 	spin_lock_irq(&mapping->tree_lock);
 	entry = get_unlocked_mapping_entry(mapping, index, &slot);
+
+	if (entry) {
+		if (size_flag & RADIX_DAX_PMD) {
+			if (!radix_tree_exceptional_entry(entry) ||
+			    dax_is_pte_entry(entry)) {
+				put_unlocked_mapping_entry(mapping, index,
+						entry);
+				entry = ERR_PTR(-EEXIST);
+				goto out_unlock;
+			}
+		} else { /* trying to grab a PTE entry */
+			if (radix_tree_exceptional_entry(entry) &&
+			    dax_is_pmd_entry(entry) &&
+			    (dax_is_zero_entry(entry) ||
+			     dax_is_empty_entry(entry))) {
+				pmd_downgrade = true;
+			}
+		}
+	}
+
 	/* No entry for given index? Make sure radix tree is big enough. */
-	if (!entry) {
+	if (!entry || pmd_downgrade) {
 		int err;
 
+		if (pmd_downgrade) {
+			/*
+			 * Make sure 'entry' remains valid while we drop
+			 * mapping->tree_lock.
+			 */
+			entry = lock_slot(mapping, slot);
+		}
+
 		spin_unlock_irq(&mapping->tree_lock);
 		err = radix_tree_preload(
 				mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
-		if (err)
+		if (err) {
+			put_locked_mapping_entry(mapping, index, entry);
 			return ERR_PTR(err);
-		entry = (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
-			       RADIX_DAX_ENTRY_LOCK);
+		}
+
+		/*
+		 * Besides huge zero pages the only other thing that gets
+		 * downgraded are empty entries which don't need to be
+		 * unmapped.
+		 */
+		if (pmd_downgrade && dax_is_zero_entry(entry))
+			unmap_mapping_range(mapping,
+				(index << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
+
 		spin_lock_irq(&mapping->tree_lock);
-		err = radix_tree_insert(&mapping->page_tree, index, entry);
+
+		if (pmd_downgrade) {
+			radix_tree_delete(&mapping->page_tree, index);
+			mapping->nrexceptional--;
+			dax_wake_mapping_entry_waiter(mapping, index, entry,
+					true);
+		}
+
+		entry = dax_radix_locked_entry(0, size_flag | RADIX_DAX_EMPTY);
+
+		err = __radix_tree_insert(&mapping->page_tree, index,
+				dax_radix_order(entry), entry);
 		radix_tree_preload_end();
 		if (err) {
 			spin_unlock_irq(&mapping->tree_lock);
-			/* Someone already created the entry? */
-			if (err == -EEXIST)
+			/*
+			 * Someone already created the entry?  This is a
+			 * normal failure when inserting PMDs in a range
+			 * that already contains PTEs.  In that case we want
+			 * to return -EEXIST immediately.
+			 */
+			if (err == -EEXIST && !(size_flag & RADIX_DAX_PMD))
 				goto restart;
+			/*
+			 * Our insertion of a DAX PMD entry failed, most
+			 * likely because it collided with a PTE sized entry
+			 * at a different index in the PMD range.  We haven't
+			 * inserted anything into the radix tree and have no
+			 * waiters to wake.
+			 */
 			return ERR_PTR(err);
 		}
 		/* Good, we have inserted empty locked entry into the tree. */
@@ -466,6 +565,7 @@ restart:
 		return page;
 	}
 	entry = lock_slot(mapping, slot);
+ out_unlock:
 	spin_unlock_irq(&mapping->tree_lock);
 	return entry;
 }
@@ -473,9 +573,9 @@ restart:
 /*
  * We do not necessarily hold the mapping->tree_lock when we call this
  * function so it is possible that 'entry' is no longer a valid item in the
- * radix tree.  This is okay, though, because all we really need to do is to
- * find the correct waitqueue where tasks might be sleeping waiting for that
- * old 'entry' and wake them.
+ * radix tree.  This is okay because all we really need to do is to find the
+ * correct waitqueue where tasks might be waiting for that old 'entry' and
+ * wake them.
  */
 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 		pgoff_t index, void *entry, bool wake_all)
@@ -588,11 +688,17 @@ static int copy_user_dax(struct block_device *bdev, sector_t sector, size_t size
 	return 0;
 }
 
-#define DAX_PMD_INDEX(page_index) (page_index & (PMD_MASK >> PAGE_SHIFT))
-
+/*
+ * By this point grab_mapping_entry() has ensured that we have a locked entry
+ * of the appropriate size so we don't have to worry about downgrading PMDs to
+ * PTEs.  If we happen to be trying to insert a PTE and there is a PMD
+ * already in the tree, we will skip the insertion and just dirty the PMD as
+ * appropriate.
+ */
 static void *dax_insert_mapping_entry(struct address_space *mapping,
 				      struct vm_fault *vmf,
-				      void *entry, sector_t sector)
+				      void *entry, sector_t sector,
+				      unsigned long flags)
 {
 	struct radix_tree_root *page_tree = &mapping->page_tree;
 	int error = 0;
@@ -615,22 +721,35 @@ static void *dax_insert_mapping_entry(struct address_space *mapping,
 		error = radix_tree_preload(vmf->gfp_mask & ~__GFP_HIGHMEM);
 		if (error)
 			return ERR_PTR(error);
+	} else if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_HZP)) {
+		/* replacing huge zero page with PMD block mapping */
+		unmap_mapping_range(mapping,
+			(vmf->pgoff << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
 	}
 
 	spin_lock_irq(&mapping->tree_lock);
-	new_entry = (void *)((unsigned long)RADIX_DAX_ENTRY(sector, false) |
-		       RADIX_DAX_ENTRY_LOCK);
+	new_entry = dax_radix_locked_entry(sector, flags);
+
 	if (hole_fill) {
 		__delete_from_page_cache(entry, NULL);
 		/* Drop pagecache reference */
 		put_page(entry);
-		error = radix_tree_insert(page_tree, index, new_entry);
+		error = __radix_tree_insert(page_tree, index,
+				dax_radix_order(new_entry), new_entry);
 		if (error) {
 			new_entry = ERR_PTR(error);
 			goto unlock;
 		}
 		mapping->nrexceptional++;
-	} else {
+	} else if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
+		/*
+		 * Only swap our new entry into the radix tree if the current
+		 * entry is a zero page or an empty entry.  If a normal PTE or
+		 * PMD entry is already in the tree, we leave it alone.  This
+		 * means that if we are trying to insert a PTE and the
+		 * existing entry is a PMD, we will just leave the PMD in the
+		 * tree and dirty it if necessary.
+		 */
 		void **slot;
 		void *ret;
 
@@ -660,7 +779,6 @@ static int dax_writeback_one(struct block_device *bdev,
 		struct address_space *mapping, pgoff_t index, void *entry)
 {
 	struct radix_tree_root *page_tree = &mapping->page_tree;
-	int type = RADIX_DAX_TYPE(entry);
 	struct radix_tree_node *node;
 	struct blk_dax_ctl dax;
 	void **slot;
@@ -681,13 +799,21 @@ static int dax_writeback_one(struct block_device *bdev,
 	if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
 		goto unlock;
 
-	if (WARN_ON_ONCE(type != RADIX_DAX_PTE && type != RADIX_DAX_PMD)) {
+	if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
+				dax_is_zero_entry(entry))) {
 		ret = -EIO;
 		goto unlock;
 	}
 
-	dax.sector = RADIX_DAX_SECTOR(entry);
-	dax.size = (type == RADIX_DAX_PMD ? PMD_SIZE : PAGE_SIZE);
+	/*
+	 * Even if dax_writeback_mapping_range() was given a wbc->range_start
+	 * in the middle of a PMD, the 'index' we are given will be aligned to
+	 * the start index of the PMD, as will the sector we pull from
+	 * 'entry'.  This allows us to flush for PMD_SIZE and not have to
+	 * worry about partial PMD writebacks.
+	 */
+	dax.sector = dax_radix_sector(entry);
+	dax.size = PAGE_SIZE << dax_radix_order(entry);
 	spin_unlock_irq(&mapping->tree_lock);
 
 	/*
@@ -726,12 +852,11 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 		struct block_device *bdev, struct writeback_control *wbc)
 {
 	struct inode *inode = mapping->host;
-	pgoff_t start_index, end_index, pmd_index;
+	pgoff_t start_index, end_index;
 	pgoff_t indices[PAGEVEC_SIZE];
 	struct pagevec pvec;
 	bool done = false;
 	int i, ret = 0;
-	void *entry;
 
 	if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
 		return -EIO;
@@ -741,15 +866,6 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 
 	start_index = wbc->range_start >> PAGE_SHIFT;
 	end_index = wbc->range_end >> PAGE_SHIFT;
-	pmd_index = DAX_PMD_INDEX(start_index);
-
-	rcu_read_lock();
-	entry = radix_tree_lookup(&mapping->page_tree, pmd_index);
-	rcu_read_unlock();
-
-	/* see if the start of our range is covered by a PMD entry */
-	if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
-		start_index = pmd_index;
 
 	tag_pages_for_writeback(mapping, start_index, end_index);
 
@@ -794,7 +910,7 @@ static int dax_insert_mapping(struct address_space *mapping,
 		return PTR_ERR(dax.addr);
 	dax_unmap_atomic(bdev, &dax);
 
-	ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector);
+	ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector, 0);
 	if (IS_ERR(ret))
 		return PTR_ERR(ret);
 	*entryp = ret;
@@ -841,7 +957,7 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	bh.b_bdev = inode->i_sb->s_bdev;
 	bh.b_size = PAGE_SIZE;
 
-	entry = grab_mapping_entry(mapping, vmf->pgoff);
+	entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
 	if (IS_ERR(entry)) {
 		error = PTR_ERR(entry);
 		goto out;
@@ -1162,7 +1278,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	if (pos >= i_size_read(inode))
 		return VM_FAULT_SIGBUS;
 
-	entry = grab_mapping_entry(mapping, vmf->pgoff);
+	entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
 	if (IS_ERR(entry)) {
 		error = PTR_ERR(entry);
 		goto out;
@@ -1264,4 +1380,191 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	return VM_FAULT_NOPAGE | major;
 }
 EXPORT_SYMBOL_GPL(dax_iomap_fault);
+
+#ifdef CONFIG_FS_DAX_PMD
+/*
+ * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
+ * more often than one might expect in the below functions.
+ */
+#define PG_PMD_COLOUR	((PMD_SIZE >> PAGE_SHIFT) - 1)
+
+static int dax_pmd_insert_mapping(struct vm_area_struct *vma, pmd_t *pmd,
+		struct vm_fault *vmf, unsigned long address,
+		struct iomap *iomap, loff_t pos, bool write, void **entryp)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	struct block_device *bdev = iomap->bdev;
+	struct blk_dax_ctl dax = {
+		.sector = dax_iomap_sector(iomap, pos),
+		.size = PMD_SIZE,
+	};
+	long length = dax_map_atomic(bdev, &dax);
+	void *ret;
+
+	if (length < 0) /* dax_map_atomic() failed */
+		return VM_FAULT_FALLBACK;
+	if (length < PMD_SIZE)
+		goto unmap_fallback;
+	if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR)
+		goto unmap_fallback;
+	if (!pfn_t_devmap(dax.pfn))
+		goto unmap_fallback;
+
+	dax_unmap_atomic(bdev, &dax);
+
+	ret = dax_insert_mapping_entry(mapping, vmf, *entryp, dax.sector,
+			RADIX_DAX_PMD);
+	if (IS_ERR(ret))
+		return VM_FAULT_FALLBACK;
+	*entryp = ret;
+
+	return vmf_insert_pfn_pmd(vma, address, pmd, dax.pfn, write);
+
+ unmap_fallback:
+	dax_unmap_atomic(bdev, &dax);
+	return VM_FAULT_FALLBACK;
+}
+
+static int dax_pmd_load_hole(struct vm_area_struct *vma, pmd_t *pmd,
+		struct vm_fault *vmf, unsigned long address,
+		struct iomap *iomap, void **entryp)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	unsigned long pmd_addr = address & PMD_MASK;
+	struct page *zero_page;
+	spinlock_t *ptl;
+	pmd_t pmd_entry;
+	void *ret;
+
+	zero_page = get_huge_zero_page();
+
+	if (unlikely(!zero_page))
+		return VM_FAULT_FALLBACK;
+
+	ret = dax_insert_mapping_entry(mapping, vmf, *entryp, 0,
+			RADIX_DAX_PMD | RADIX_DAX_HZP);
+	if (IS_ERR(ret))
+		return VM_FAULT_FALLBACK;
+	*entryp = ret;
+
+	ptl = pmd_lock(vma->vm_mm, pmd);
+	if (!pmd_none(*pmd)) {
+		spin_unlock(ptl);
+		return VM_FAULT_FALLBACK;
+	}
+
+	pmd_entry = mk_pmd(zero_page, vma->vm_page_prot);
+	pmd_entry = pmd_mkhuge(pmd_entry);
+	set_pmd_at(vma->vm_mm, pmd_addr, pmd, pmd_entry);
+	spin_unlock(ptl);
+	return VM_FAULT_NOPAGE;
+}
+
+int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
+		pmd_t *pmd, unsigned int flags, struct iomap_ops *ops)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	unsigned long pmd_addr = address & PMD_MASK;
+	bool write = flags & FAULT_FLAG_WRITE;
+	unsigned int iomap_flags = write ? IOMAP_WRITE : 0;
+	struct inode *inode = mapping->host;
+	int result = VM_FAULT_FALLBACK;
+	struct iomap iomap = { 0 };
+	pgoff_t max_pgoff, pgoff;
+	struct vm_fault vmf;
+	void *entry;
+	loff_t pos;
+	int error;
+
+	/* Fall back to PTEs if we're going to COW */
+	if (write && !(vma->vm_flags & VM_SHARED)) {
+		split_huge_pmd(vma, pmd, address);
+		goto fallback;
+	}
+
+	/* If the PMD would extend outside the VMA */
+	if (pmd_addr < vma->vm_start)
+		goto fallback;
+	if ((pmd_addr + PMD_SIZE) > vma->vm_end)
+		goto fallback;
+
+	/*
+	 * Check whether offset isn't beyond end of file now. Caller is
+	 * supposed to hold locks serializing us with truncate / punch hole so
+	 * this is a reliable test.
+	 */
+	pgoff = linear_page_index(vma, pmd_addr);
+	max_pgoff = (i_size_read(inode) - 1) >> PAGE_SHIFT;
+
+	if (pgoff > max_pgoff)
+		return VM_FAULT_SIGBUS;
+
+	/* If the PMD would extend beyond the file size */
+	if ((pgoff | PG_PMD_COLOUR) > max_pgoff)
+		goto fallback;
+
+	/*
+	 * grab_mapping_entry() will make sure we get a 2M empty entry, a DAX
+	 * PMD or a HZP entry.  If it can't (because a 4k page is already in
+	 * the tree, for instance), it will return -EEXIST and we just fall
+	 * back to 4k entries.
+	 */
+	entry = grab_mapping_entry(mapping, pgoff, RADIX_DAX_PMD);
+	if (IS_ERR(entry))
+		goto fallback;
+
+	/*
+	 * Note that we don't use iomap_apply here.  We aren't doing I/O, only
+	 * setting up a mapping, so really we're using iomap_begin() as a way
+	 * to look up our filesystem block.
+	 */
+	pos = (loff_t)pgoff << PAGE_SHIFT;
+	error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap);
+	if (error)
+		goto unlock_entry;
+	if (iomap.offset + iomap.length < pos + PMD_SIZE)
+		goto finish_iomap;
+
+	vmf.pgoff = pgoff;
+	vmf.flags = flags;
+	vmf.gfp_mask = mapping_gfp_mask(mapping) | __GFP_IO;
+
+	switch (iomap.type) {
+	case IOMAP_MAPPED:
+		result = dax_pmd_insert_mapping(vma, pmd, &vmf, address,
+				&iomap, pos, write, &entry);
+		break;
+	case IOMAP_UNWRITTEN:
+	case IOMAP_HOLE:
+		if (WARN_ON_ONCE(write))
+			goto finish_iomap;
+		result = dax_pmd_load_hole(vma, pmd, &vmf, address, &iomap,
+				&entry);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		break;
+	}
+
+ finish_iomap:
+	if (ops->iomap_end) {
+		if (result == VM_FAULT_FALLBACK) {
+			ops->iomap_end(inode, pos, PMD_SIZE, 0, iomap_flags,
+					&iomap);
+		} else {
+			error = ops->iomap_end(inode, pos, PMD_SIZE, PMD_SIZE,
+					iomap_flags, &iomap);
+			if (error)
+				result = VM_FAULT_FALLBACK;
+		}
+	}
+ unlock_entry:
+	put_locked_mapping_entry(mapping, pgoff, entry);
+ fallback:
+	if (result == VM_FAULT_FALLBACK)
+		count_vm_event(THP_FAULT_FALLBACK);
+	return result;
+}
+EXPORT_SYMBOL_GPL(dax_iomap_pmd_fault);
+#endif /* CONFIG_FS_DAX_PMD */
 #endif /* CONFIG_FS_IOMAP */
diff --git a/include/linux/dax.h b/include/linux/dax.h
index e9ea78c..8d1a5c4 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -9,20 +9,32 @@
 struct iomap_ops;
 
 /*
- * We use lowest available bit in exceptional entry for locking, other two
- * bits to determine entry type. In total 3 special bits.
+ * We use lowest available bit in exceptional entry for locking, one bit for
+ * the entry size (PMD) and two more to tell us if the entry is a huge zero
+ * page (HZP) or an empty entry that is just used for locking.  In total four
+ * special bits.
+ *
+ * If the PMD bit isn't set the entry has size PAGE_SIZE, and if the HZP and
+ * EMPTY bits aren't set the entry is a normal DAX entry with a filesystem
+ * block allocation.
  */
-#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 3)
+#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 4)
 #define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
-#define RADIX_DAX_PTE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
-#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
-#define RADIX_DAX_TYPE_MASK (RADIX_DAX_PTE | RADIX_DAX_PMD)
-#define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_TYPE_MASK)
-#define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
-#define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
-		RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE) | \
-		RADIX_TREE_EXCEPTIONAL_ENTRY))
+#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
+#define RADIX_DAX_HZP (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
+#define RADIX_DAX_EMPTY (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 3))
 
+static inline unsigned long dax_radix_sector(void *entry)
+{
+	return (unsigned long)entry >> RADIX_DAX_SHIFT;
+}
+
+static inline void *dax_radix_locked_entry(sector_t sector, unsigned long flags)
+{
+	return (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY | flags |
+			((unsigned long)sector << RADIX_DAX_SHIFT) |
+			RADIX_DAX_ENTRY_LOCK);
+}
 
 ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_ops *ops);
@@ -67,6 +79,27 @@ static inline int dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
 	return VM_FAULT_FALLBACK;
 }
 
+#ifdef CONFIG_FS_DAX_PMD
+static inline unsigned int dax_radix_order(void *entry)
+{
+	if ((unsigned long)entry & RADIX_DAX_PMD)
+		return PMD_SHIFT - PAGE_SHIFT;
+	return 0;
+}
+int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
+		pmd_t *pmd, unsigned int flags, struct iomap_ops *ops);
+#else
+static inline unsigned int dax_radix_order(void *entry)
+{
+	return 0;
+}
+static inline int dax_iomap_pmd_fault(struct vm_area_struct *vma,
+		unsigned long address, pmd_t *pmd, unsigned int flags,
+		struct iomap_ops *ops)
+{
+	return VM_FAULT_FALLBACK;
+}
+#endif
 int dax_pfn_mkwrite(struct vm_area_struct *, struct vm_fault *);
 #define dax_mkwrite(vma, vmf, gb)	dax_fault(vma, vmf, gb)
 
diff --git a/mm/filemap.c b/mm/filemap.c
index a596462..592e6e9 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -611,8 +611,7 @@ static int page_cache_tree_insert(struct address_space *mapping,
 		} else {
 			/* DAX can replace empty locked entry with a hole */
 			WARN_ON_ONCE(p !=
-				(void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
-					 RADIX_DAX_ENTRY_LOCK));
+				dax_radix_locked_entry(0, RADIX_DAX_EMPTY));
 			/* DAX accounts exceptional entries as normal pages */
 			if (node)
 				workingset_node_pages_dec(node);
-- 
2.9.0

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^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 15/17] dax: add struct iomap based DAX PMD support
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel-u79uwXL29TY76Z2rM5mHXA
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner,
	linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw, Christoph Hellwig,
	linux-xfs-u79uwXL29TY76Z2rM5mHXA,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg, Andreas Dilger, Alexander Viro,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA, Jan Kara,
	linux-ext4-u79uwXL29TY76Z2rM5mHXA, Andrew Morton

DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
locking.  This patch allows DAX PMDs to participate in the DAX radix tree
based locking scheme so that they can be re-enabled using the new struct
iomap based fault handlers.

There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
mappings that have an associated block allocation, and 4k DAX empty
entries.  The empty entries exist to provide locking for the duration of a
given page fault.

This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
entries, PMD DAX entries that have associated block allocations, and 2 MiB
DAX empty entries.

Unlike the 4k case where we insert a struct page* into the radix tree for
4k zero pages, for HZP we insert a DAX exceptional entry with the new
RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
every 2MiB hole mapping, and it doesn't make sense to have that same struct
page* with multiple entries in multiple trees.  This would cause contention
on the single page lock for the one Huge Zero Page, and it would break the
page->index and page->mapping associations that are assumed to be valid in
many other places in the kernel.

One difficult use case is when one thread is trying to use 4k entries in
radix tree for a given offset, and another thread is using 2 MiB entries
for that same offset.  The current code handles this by making the 2 MiB
user fall back to 4k entries for most cases.  This was done because it is
the simplest solution, and because the use of 2MiB pages is already
opportunistic.

If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
we run into the problem of how we lock out 4k page faults for the entire
2MiB range while we clean out the radix tree so we can insert the 2MiB
entry.  We can solve this problem if we need to, but I think that the cases
where both 2MiB entries and 4K entries are being used for the same range
will be rare enough and the gain small enough that it probably won't be
worth the complexity.

Signed-off-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
---
 fs/dax.c            | 377 ++++++++++++++++++++++++++++++++++++++++++++++------
 include/linux/dax.h |  55 ++++++--
 mm/filemap.c        |   3 +-
 3 files changed, 385 insertions(+), 50 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 0582c7c..39b41ea 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -76,6 +76,26 @@ static void dax_unmap_atomic(struct block_device *bdev,
 	blk_queue_exit(bdev->bd_queue);
 }
 
+static int dax_is_pmd_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_PMD;
+}
+
+static int dax_is_pte_entry(void *entry)
+{
+	return !((unsigned long)entry & RADIX_DAX_PMD);
+}
+
+static int dax_is_zero_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_HZP;
+}
+
+static int dax_is_empty_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_EMPTY;
+}
+
 struct page *read_dax_sector(struct block_device *bdev, sector_t n)
 {
 	struct page *page = alloc_pages(GFP_KERNEL, 0);
@@ -281,7 +301,7 @@ static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
 	 * queue to the start of that PMD.  This ensures that all offsets in
 	 * the range covered by the PMD map to the same bit lock.
 	 */
-	if (RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
+	if (dax_is_pmd_entry(entry))
 		index &= ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1);
 
 	key->mapping = mapping;
@@ -413,36 +433,115 @@ static void put_unlocked_mapping_entry(struct address_space *mapping,
  * radix tree entry locked. If the radix tree doesn't contain given index,
  * create empty exceptional entry for the index and return with it locked.
  *
+ * When requesting an entry with size RADIX_DAX_PMD, grab_mapping_entry() will
+ * either return that locked entry or will return an error.  This error will
+ * happen if there are any 4k entries (either zero pages or DAX entries)
+ * within the 2MiB range that we are requesting.
+ *
+ * We always favor 4k entries over 2MiB entries. There isn't a flow where we
+ * evict 4k entries in order to 'upgrade' them to a 2MiB entry.  A 2MiB
+ * insertion will fail if it finds any 4k entries already in the tree, and a
+ * 4k insertion will cause an existing 2MiB entry to be unmapped and
+ * downgraded to 4k entries.  This happens for both 2MiB huge zero pages as
+ * well as 2MiB empty entries.
+ *
+ * The exception to this downgrade path is for 2MiB DAX PMD entries that have
+ * real storage backing them.  We will leave these real 2MiB DAX entries in
+ * the tree, and PTE writes will simply dirty the entire 2MiB DAX entry.
+ *
  * Note: Unlike filemap_fault() we don't honor FAULT_FLAG_RETRY flags. For
  * persistent memory the benefit is doubtful. We can add that later if we can
  * show it helps.
  */
-static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index)
+static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
+		unsigned long size_flag)
 {
+	bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */
 	void *entry, **slot;
 
 restart:
 	spin_lock_irq(&mapping->tree_lock);
 	entry = get_unlocked_mapping_entry(mapping, index, &slot);
+
+	if (entry) {
+		if (size_flag & RADIX_DAX_PMD) {
+			if (!radix_tree_exceptional_entry(entry) ||
+			    dax_is_pte_entry(entry)) {
+				put_unlocked_mapping_entry(mapping, index,
+						entry);
+				entry = ERR_PTR(-EEXIST);
+				goto out_unlock;
+			}
+		} else { /* trying to grab a PTE entry */
+			if (radix_tree_exceptional_entry(entry) &&
+			    dax_is_pmd_entry(entry) &&
+			    (dax_is_zero_entry(entry) ||
+			     dax_is_empty_entry(entry))) {
+				pmd_downgrade = true;
+			}
+		}
+	}
+
 	/* No entry for given index? Make sure radix tree is big enough. */
-	if (!entry) {
+	if (!entry || pmd_downgrade) {
 		int err;
 
+		if (pmd_downgrade) {
+			/*
+			 * Make sure 'entry' remains valid while we drop
+			 * mapping->tree_lock.
+			 */
+			entry = lock_slot(mapping, slot);
+		}
+
 		spin_unlock_irq(&mapping->tree_lock);
 		err = radix_tree_preload(
 				mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
-		if (err)
+		if (err) {
+			put_locked_mapping_entry(mapping, index, entry);
 			return ERR_PTR(err);
-		entry = (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
-			       RADIX_DAX_ENTRY_LOCK);
+		}
+
+		/*
+		 * Besides huge zero pages the only other thing that gets
+		 * downgraded are empty entries which don't need to be
+		 * unmapped.
+		 */
+		if (pmd_downgrade && dax_is_zero_entry(entry))
+			unmap_mapping_range(mapping,
+				(index << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
+
 		spin_lock_irq(&mapping->tree_lock);
-		err = radix_tree_insert(&mapping->page_tree, index, entry);
+
+		if (pmd_downgrade) {
+			radix_tree_delete(&mapping->page_tree, index);
+			mapping->nrexceptional--;
+			dax_wake_mapping_entry_waiter(mapping, index, entry,
+					true);
+		}
+
+		entry = dax_radix_locked_entry(0, size_flag | RADIX_DAX_EMPTY);
+
+		err = __radix_tree_insert(&mapping->page_tree, index,
+				dax_radix_order(entry), entry);
 		radix_tree_preload_end();
 		if (err) {
 			spin_unlock_irq(&mapping->tree_lock);
-			/* Someone already created the entry? */
-			if (err == -EEXIST)
+			/*
+			 * Someone already created the entry?  This is a
+			 * normal failure when inserting PMDs in a range
+			 * that already contains PTEs.  In that case we want
+			 * to return -EEXIST immediately.
+			 */
+			if (err == -EEXIST && !(size_flag & RADIX_DAX_PMD))
 				goto restart;
+			/*
+			 * Our insertion of a DAX PMD entry failed, most
+			 * likely because it collided with a PTE sized entry
+			 * at a different index in the PMD range.  We haven't
+			 * inserted anything into the radix tree and have no
+			 * waiters to wake.
+			 */
 			return ERR_PTR(err);
 		}
 		/* Good, we have inserted empty locked entry into the tree. */
@@ -466,6 +565,7 @@ restart:
 		return page;
 	}
 	entry = lock_slot(mapping, slot);
+ out_unlock:
 	spin_unlock_irq(&mapping->tree_lock);
 	return entry;
 }
@@ -473,9 +573,9 @@ restart:
 /*
  * We do not necessarily hold the mapping->tree_lock when we call this
  * function so it is possible that 'entry' is no longer a valid item in the
- * radix tree.  This is okay, though, because all we really need to do is to
- * find the correct waitqueue where tasks might be sleeping waiting for that
- * old 'entry' and wake them.
+ * radix tree.  This is okay because all we really need to do is to find the
+ * correct waitqueue where tasks might be waiting for that old 'entry' and
+ * wake them.
  */
 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 		pgoff_t index, void *entry, bool wake_all)
@@ -588,11 +688,17 @@ static int copy_user_dax(struct block_device *bdev, sector_t sector, size_t size
 	return 0;
 }
 
-#define DAX_PMD_INDEX(page_index) (page_index & (PMD_MASK >> PAGE_SHIFT))
-
+/*
+ * By this point grab_mapping_entry() has ensured that we have a locked entry
+ * of the appropriate size so we don't have to worry about downgrading PMDs to
+ * PTEs.  If we happen to be trying to insert a PTE and there is a PMD
+ * already in the tree, we will skip the insertion and just dirty the PMD as
+ * appropriate.
+ */
 static void *dax_insert_mapping_entry(struct address_space *mapping,
 				      struct vm_fault *vmf,
-				      void *entry, sector_t sector)
+				      void *entry, sector_t sector,
+				      unsigned long flags)
 {
 	struct radix_tree_root *page_tree = &mapping->page_tree;
 	int error = 0;
@@ -615,22 +721,35 @@ static void *dax_insert_mapping_entry(struct address_space *mapping,
 		error = radix_tree_preload(vmf->gfp_mask & ~__GFP_HIGHMEM);
 		if (error)
 			return ERR_PTR(error);
+	} else if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_HZP)) {
+		/* replacing huge zero page with PMD block mapping */
+		unmap_mapping_range(mapping,
+			(vmf->pgoff << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
 	}
 
 	spin_lock_irq(&mapping->tree_lock);
-	new_entry = (void *)((unsigned long)RADIX_DAX_ENTRY(sector, false) |
-		       RADIX_DAX_ENTRY_LOCK);
+	new_entry = dax_radix_locked_entry(sector, flags);
+
 	if (hole_fill) {
 		__delete_from_page_cache(entry, NULL);
 		/* Drop pagecache reference */
 		put_page(entry);
-		error = radix_tree_insert(page_tree, index, new_entry);
+		error = __radix_tree_insert(page_tree, index,
+				dax_radix_order(new_entry), new_entry);
 		if (error) {
 			new_entry = ERR_PTR(error);
 			goto unlock;
 		}
 		mapping->nrexceptional++;
-	} else {
+	} else if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
+		/*
+		 * Only swap our new entry into the radix tree if the current
+		 * entry is a zero page or an empty entry.  If a normal PTE or
+		 * PMD entry is already in the tree, we leave it alone.  This
+		 * means that if we are trying to insert a PTE and the
+		 * existing entry is a PMD, we will just leave the PMD in the
+		 * tree and dirty it if necessary.
+		 */
 		void **slot;
 		void *ret;
 
@@ -660,7 +779,6 @@ static int dax_writeback_one(struct block_device *bdev,
 		struct address_space *mapping, pgoff_t index, void *entry)
 {
 	struct radix_tree_root *page_tree = &mapping->page_tree;
-	int type = RADIX_DAX_TYPE(entry);
 	struct radix_tree_node *node;
 	struct blk_dax_ctl dax;
 	void **slot;
@@ -681,13 +799,21 @@ static int dax_writeback_one(struct block_device *bdev,
 	if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
 		goto unlock;
 
-	if (WARN_ON_ONCE(type != RADIX_DAX_PTE && type != RADIX_DAX_PMD)) {
+	if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
+				dax_is_zero_entry(entry))) {
 		ret = -EIO;
 		goto unlock;
 	}
 
-	dax.sector = RADIX_DAX_SECTOR(entry);
-	dax.size = (type == RADIX_DAX_PMD ? PMD_SIZE : PAGE_SIZE);
+	/*
+	 * Even if dax_writeback_mapping_range() was given a wbc->range_start
+	 * in the middle of a PMD, the 'index' we are given will be aligned to
+	 * the start index of the PMD, as will the sector we pull from
+	 * 'entry'.  This allows us to flush for PMD_SIZE and not have to
+	 * worry about partial PMD writebacks.
+	 */
+	dax.sector = dax_radix_sector(entry);
+	dax.size = PAGE_SIZE << dax_radix_order(entry);
 	spin_unlock_irq(&mapping->tree_lock);
 
 	/*
@@ -726,12 +852,11 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 		struct block_device *bdev, struct writeback_control *wbc)
 {
 	struct inode *inode = mapping->host;
-	pgoff_t start_index, end_index, pmd_index;
+	pgoff_t start_index, end_index;
 	pgoff_t indices[PAGEVEC_SIZE];
 	struct pagevec pvec;
 	bool done = false;
 	int i, ret = 0;
-	void *entry;
 
 	if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
 		return -EIO;
@@ -741,15 +866,6 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 
 	start_index = wbc->range_start >> PAGE_SHIFT;
 	end_index = wbc->range_end >> PAGE_SHIFT;
-	pmd_index = DAX_PMD_INDEX(start_index);
-
-	rcu_read_lock();
-	entry = radix_tree_lookup(&mapping->page_tree, pmd_index);
-	rcu_read_unlock();
-
-	/* see if the start of our range is covered by a PMD entry */
-	if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
-		start_index = pmd_index;
 
 	tag_pages_for_writeback(mapping, start_index, end_index);
 
@@ -794,7 +910,7 @@ static int dax_insert_mapping(struct address_space *mapping,
 		return PTR_ERR(dax.addr);
 	dax_unmap_atomic(bdev, &dax);
 
-	ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector);
+	ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector, 0);
 	if (IS_ERR(ret))
 		return PTR_ERR(ret);
 	*entryp = ret;
@@ -841,7 +957,7 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	bh.b_bdev = inode->i_sb->s_bdev;
 	bh.b_size = PAGE_SIZE;
 
-	entry = grab_mapping_entry(mapping, vmf->pgoff);
+	entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
 	if (IS_ERR(entry)) {
 		error = PTR_ERR(entry);
 		goto out;
@@ -1162,7 +1278,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	if (pos >= i_size_read(inode))
 		return VM_FAULT_SIGBUS;
 
-	entry = grab_mapping_entry(mapping, vmf->pgoff);
+	entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
 	if (IS_ERR(entry)) {
 		error = PTR_ERR(entry);
 		goto out;
@@ -1264,4 +1380,191 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	return VM_FAULT_NOPAGE | major;
 }
 EXPORT_SYMBOL_GPL(dax_iomap_fault);
+
+#ifdef CONFIG_FS_DAX_PMD
+/*
+ * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
+ * more often than one might expect in the below functions.
+ */
+#define PG_PMD_COLOUR	((PMD_SIZE >> PAGE_SHIFT) - 1)
+
+static int dax_pmd_insert_mapping(struct vm_area_struct *vma, pmd_t *pmd,
+		struct vm_fault *vmf, unsigned long address,
+		struct iomap *iomap, loff_t pos, bool write, void **entryp)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	struct block_device *bdev = iomap->bdev;
+	struct blk_dax_ctl dax = {
+		.sector = dax_iomap_sector(iomap, pos),
+		.size = PMD_SIZE,
+	};
+	long length = dax_map_atomic(bdev, &dax);
+	void *ret;
+
+	if (length < 0) /* dax_map_atomic() failed */
+		return VM_FAULT_FALLBACK;
+	if (length < PMD_SIZE)
+		goto unmap_fallback;
+	if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR)
+		goto unmap_fallback;
+	if (!pfn_t_devmap(dax.pfn))
+		goto unmap_fallback;
+
+	dax_unmap_atomic(bdev, &dax);
+
+	ret = dax_insert_mapping_entry(mapping, vmf, *entryp, dax.sector,
+			RADIX_DAX_PMD);
+	if (IS_ERR(ret))
+		return VM_FAULT_FALLBACK;
+	*entryp = ret;
+
+	return vmf_insert_pfn_pmd(vma, address, pmd, dax.pfn, write);
+
+ unmap_fallback:
+	dax_unmap_atomic(bdev, &dax);
+	return VM_FAULT_FALLBACK;
+}
+
+static int dax_pmd_load_hole(struct vm_area_struct *vma, pmd_t *pmd,
+		struct vm_fault *vmf, unsigned long address,
+		struct iomap *iomap, void **entryp)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	unsigned long pmd_addr = address & PMD_MASK;
+	struct page *zero_page;
+	spinlock_t *ptl;
+	pmd_t pmd_entry;
+	void *ret;
+
+	zero_page = get_huge_zero_page();
+
+	if (unlikely(!zero_page))
+		return VM_FAULT_FALLBACK;
+
+	ret = dax_insert_mapping_entry(mapping, vmf, *entryp, 0,
+			RADIX_DAX_PMD | RADIX_DAX_HZP);
+	if (IS_ERR(ret))
+		return VM_FAULT_FALLBACK;
+	*entryp = ret;
+
+	ptl = pmd_lock(vma->vm_mm, pmd);
+	if (!pmd_none(*pmd)) {
+		spin_unlock(ptl);
+		return VM_FAULT_FALLBACK;
+	}
+
+	pmd_entry = mk_pmd(zero_page, vma->vm_page_prot);
+	pmd_entry = pmd_mkhuge(pmd_entry);
+	set_pmd_at(vma->vm_mm, pmd_addr, pmd, pmd_entry);
+	spin_unlock(ptl);
+	return VM_FAULT_NOPAGE;
+}
+
+int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
+		pmd_t *pmd, unsigned int flags, struct iomap_ops *ops)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	unsigned long pmd_addr = address & PMD_MASK;
+	bool write = flags & FAULT_FLAG_WRITE;
+	unsigned int iomap_flags = write ? IOMAP_WRITE : 0;
+	struct inode *inode = mapping->host;
+	int result = VM_FAULT_FALLBACK;
+	struct iomap iomap = { 0 };
+	pgoff_t max_pgoff, pgoff;
+	struct vm_fault vmf;
+	void *entry;
+	loff_t pos;
+	int error;
+
+	/* Fall back to PTEs if we're going to COW */
+	if (write && !(vma->vm_flags & VM_SHARED)) {
+		split_huge_pmd(vma, pmd, address);
+		goto fallback;
+	}
+
+	/* If the PMD would extend outside the VMA */
+	if (pmd_addr < vma->vm_start)
+		goto fallback;
+	if ((pmd_addr + PMD_SIZE) > vma->vm_end)
+		goto fallback;
+
+	/*
+	 * Check whether offset isn't beyond end of file now. Caller is
+	 * supposed to hold locks serializing us with truncate / punch hole so
+	 * this is a reliable test.
+	 */
+	pgoff = linear_page_index(vma, pmd_addr);
+	max_pgoff = (i_size_read(inode) - 1) >> PAGE_SHIFT;
+
+	if (pgoff > max_pgoff)
+		return VM_FAULT_SIGBUS;
+
+	/* If the PMD would extend beyond the file size */
+	if ((pgoff | PG_PMD_COLOUR) > max_pgoff)
+		goto fallback;
+
+	/*
+	 * grab_mapping_entry() will make sure we get a 2M empty entry, a DAX
+	 * PMD or a HZP entry.  If it can't (because a 4k page is already in
+	 * the tree, for instance), it will return -EEXIST and we just fall
+	 * back to 4k entries.
+	 */
+	entry = grab_mapping_entry(mapping, pgoff, RADIX_DAX_PMD);
+	if (IS_ERR(entry))
+		goto fallback;
+
+	/*
+	 * Note that we don't use iomap_apply here.  We aren't doing I/O, only
+	 * setting up a mapping, so really we're using iomap_begin() as a way
+	 * to look up our filesystem block.
+	 */
+	pos = (loff_t)pgoff << PAGE_SHIFT;
+	error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap);
+	if (error)
+		goto unlock_entry;
+	if (iomap.offset + iomap.length < pos + PMD_SIZE)
+		goto finish_iomap;
+
+	vmf.pgoff = pgoff;
+	vmf.flags = flags;
+	vmf.gfp_mask = mapping_gfp_mask(mapping) | __GFP_IO;
+
+	switch (iomap.type) {
+	case IOMAP_MAPPED:
+		result = dax_pmd_insert_mapping(vma, pmd, &vmf, address,
+				&iomap, pos, write, &entry);
+		break;
+	case IOMAP_UNWRITTEN:
+	case IOMAP_HOLE:
+		if (WARN_ON_ONCE(write))
+			goto finish_iomap;
+		result = dax_pmd_load_hole(vma, pmd, &vmf, address, &iomap,
+				&entry);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		break;
+	}
+
+ finish_iomap:
+	if (ops->iomap_end) {
+		if (result == VM_FAULT_FALLBACK) {
+			ops->iomap_end(inode, pos, PMD_SIZE, 0, iomap_flags,
+					&iomap);
+		} else {
+			error = ops->iomap_end(inode, pos, PMD_SIZE, PMD_SIZE,
+					iomap_flags, &iomap);
+			if (error)
+				result = VM_FAULT_FALLBACK;
+		}
+	}
+ unlock_entry:
+	put_locked_mapping_entry(mapping, pgoff, entry);
+ fallback:
+	if (result == VM_FAULT_FALLBACK)
+		count_vm_event(THP_FAULT_FALLBACK);
+	return result;
+}
+EXPORT_SYMBOL_GPL(dax_iomap_pmd_fault);
+#endif /* CONFIG_FS_DAX_PMD */
 #endif /* CONFIG_FS_IOMAP */
diff --git a/include/linux/dax.h b/include/linux/dax.h
index e9ea78c..8d1a5c4 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -9,20 +9,32 @@
 struct iomap_ops;
 
 /*
- * We use lowest available bit in exceptional entry for locking, other two
- * bits to determine entry type. In total 3 special bits.
+ * We use lowest available bit in exceptional entry for locking, one bit for
+ * the entry size (PMD) and two more to tell us if the entry is a huge zero
+ * page (HZP) or an empty entry that is just used for locking.  In total four
+ * special bits.
+ *
+ * If the PMD bit isn't set the entry has size PAGE_SIZE, and if the HZP and
+ * EMPTY bits aren't set the entry is a normal DAX entry with a filesystem
+ * block allocation.
  */
-#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 3)
+#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 4)
 #define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
-#define RADIX_DAX_PTE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
-#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
-#define RADIX_DAX_TYPE_MASK (RADIX_DAX_PTE | RADIX_DAX_PMD)
-#define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_TYPE_MASK)
-#define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
-#define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
-		RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE) | \
-		RADIX_TREE_EXCEPTIONAL_ENTRY))
+#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
+#define RADIX_DAX_HZP (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
+#define RADIX_DAX_EMPTY (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 3))
 
+static inline unsigned long dax_radix_sector(void *entry)
+{
+	return (unsigned long)entry >> RADIX_DAX_SHIFT;
+}
+
+static inline void *dax_radix_locked_entry(sector_t sector, unsigned long flags)
+{
+	return (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY | flags |
+			((unsigned long)sector << RADIX_DAX_SHIFT) |
+			RADIX_DAX_ENTRY_LOCK);
+}
 
 ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_ops *ops);
@@ -67,6 +79,27 @@ static inline int dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
 	return VM_FAULT_FALLBACK;
 }
 
+#ifdef CONFIG_FS_DAX_PMD
+static inline unsigned int dax_radix_order(void *entry)
+{
+	if ((unsigned long)entry & RADIX_DAX_PMD)
+		return PMD_SHIFT - PAGE_SHIFT;
+	return 0;
+}
+int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
+		pmd_t *pmd, unsigned int flags, struct iomap_ops *ops);
+#else
+static inline unsigned int dax_radix_order(void *entry)
+{
+	return 0;
+}
+static inline int dax_iomap_pmd_fault(struct vm_area_struct *vma,
+		unsigned long address, pmd_t *pmd, unsigned int flags,
+		struct iomap_ops *ops)
+{
+	return VM_FAULT_FALLBACK;
+}
+#endif
 int dax_pfn_mkwrite(struct vm_area_struct *, struct vm_fault *);
 #define dax_mkwrite(vma, vmf, gb)	dax_fault(vma, vmf, gb)
 
diff --git a/mm/filemap.c b/mm/filemap.c
index a596462..592e6e9 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -611,8 +611,7 @@ static int page_cache_tree_insert(struct address_space *mapping,
 		} else {
 			/* DAX can replace empty locked entry with a hole */
 			WARN_ON_ONCE(p !=
-				(void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
-					 RADIX_DAX_ENTRY_LOCK));
+				dax_radix_locked_entry(0, RADIX_DAX_EMPTY));
 			/* DAX accounts exceptional entries as normal pages */
 			if (node)
 				workingset_node_pages_dec(node);
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 15/17] dax: add struct iomap based DAX PMD support
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
locking.  This patch allows DAX PMDs to participate in the DAX radix tree
based locking scheme so that they can be re-enabled using the new struct
iomap based fault handlers.

There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
mappings that have an associated block allocation, and 4k DAX empty
entries.  The empty entries exist to provide locking for the duration of a
given page fault.

This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
entries, PMD DAX entries that have associated block allocations, and 2 MiB
DAX empty entries.

Unlike the 4k case where we insert a struct page* into the radix tree for
4k zero pages, for HZP we insert a DAX exceptional entry with the new
RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
every 2MiB hole mapping, and it doesn't make sense to have that same struct
page* with multiple entries in multiple trees.  This would cause contention
on the single page lock for the one Huge Zero Page, and it would break the
page->index and page->mapping associations that are assumed to be valid in
many other places in the kernel.

One difficult use case is when one thread is trying to use 4k entries in
radix tree for a given offset, and another thread is using 2 MiB entries
for that same offset.  The current code handles this by making the 2 MiB
user fall back to 4k entries for most cases.  This was done because it is
the simplest solution, and because the use of 2MiB pages is already
opportunistic.

If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
we run into the problem of how we lock out 4k page faults for the entire
2MiB range while we clean out the radix tree so we can insert the 2MiB
entry.  We can solve this problem if we need to, but I think that the cases
where both 2MiB entries and 4K entries are being used for the same range
will be rare enough and the gain small enough that it probably won't be
worth the complexity.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
---
 fs/dax.c            | 377 ++++++++++++++++++++++++++++++++++++++++++++++------
 include/linux/dax.h |  55 ++++++--
 mm/filemap.c        |   3 +-
 3 files changed, 385 insertions(+), 50 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 0582c7c..39b41ea 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -76,6 +76,26 @@ static void dax_unmap_atomic(struct block_device *bdev,
 	blk_queue_exit(bdev->bd_queue);
 }
 
+static int dax_is_pmd_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_PMD;
+}
+
+static int dax_is_pte_entry(void *entry)
+{
+	return !((unsigned long)entry & RADIX_DAX_PMD);
+}
+
+static int dax_is_zero_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_HZP;
+}
+
+static int dax_is_empty_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_EMPTY;
+}
+
 struct page *read_dax_sector(struct block_device *bdev, sector_t n)
 {
 	struct page *page = alloc_pages(GFP_KERNEL, 0);
@@ -281,7 +301,7 @@ static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
 	 * queue to the start of that PMD.  This ensures that all offsets in
 	 * the range covered by the PMD map to the same bit lock.
 	 */
-	if (RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
+	if (dax_is_pmd_entry(entry))
 		index &= ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1);
 
 	key->mapping = mapping;
@@ -413,36 +433,115 @@ static void put_unlocked_mapping_entry(struct address_space *mapping,
  * radix tree entry locked. If the radix tree doesn't contain given index,
  * create empty exceptional entry for the index and return with it locked.
  *
+ * When requesting an entry with size RADIX_DAX_PMD, grab_mapping_entry() will
+ * either return that locked entry or will return an error.  This error will
+ * happen if there are any 4k entries (either zero pages or DAX entries)
+ * within the 2MiB range that we are requesting.
+ *
+ * We always favor 4k entries over 2MiB entries. There isn't a flow where we
+ * evict 4k entries in order to 'upgrade' them to a 2MiB entry.  A 2MiB
+ * insertion will fail if it finds any 4k entries already in the tree, and a
+ * 4k insertion will cause an existing 2MiB entry to be unmapped and
+ * downgraded to 4k entries.  This happens for both 2MiB huge zero pages as
+ * well as 2MiB empty entries.
+ *
+ * The exception to this downgrade path is for 2MiB DAX PMD entries that have
+ * real storage backing them.  We will leave these real 2MiB DAX entries in
+ * the tree, and PTE writes will simply dirty the entire 2MiB DAX entry.
+ *
  * Note: Unlike filemap_fault() we don't honor FAULT_FLAG_RETRY flags. For
  * persistent memory the benefit is doubtful. We can add that later if we can
  * show it helps.
  */
-static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index)
+static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
+		unsigned long size_flag)
 {
+	bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */
 	void *entry, **slot;
 
 restart:
 	spin_lock_irq(&mapping->tree_lock);
 	entry = get_unlocked_mapping_entry(mapping, index, &slot);
+
+	if (entry) {
+		if (size_flag & RADIX_DAX_PMD) {
+			if (!radix_tree_exceptional_entry(entry) ||
+			    dax_is_pte_entry(entry)) {
+				put_unlocked_mapping_entry(mapping, index,
+						entry);
+				entry = ERR_PTR(-EEXIST);
+				goto out_unlock;
+			}
+		} else { /* trying to grab a PTE entry */
+			if (radix_tree_exceptional_entry(entry) &&
+			    dax_is_pmd_entry(entry) &&
+			    (dax_is_zero_entry(entry) ||
+			     dax_is_empty_entry(entry))) {
+				pmd_downgrade = true;
+			}
+		}
+	}
+
 	/* No entry for given index? Make sure radix tree is big enough. */
-	if (!entry) {
+	if (!entry || pmd_downgrade) {
 		int err;
 
+		if (pmd_downgrade) {
+			/*
+			 * Make sure 'entry' remains valid while we drop
+			 * mapping->tree_lock.
+			 */
+			entry = lock_slot(mapping, slot);
+		}
+
 		spin_unlock_irq(&mapping->tree_lock);
 		err = radix_tree_preload(
 				mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
-		if (err)
+		if (err) {
+			put_locked_mapping_entry(mapping, index, entry);
 			return ERR_PTR(err);
-		entry = (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
-			       RADIX_DAX_ENTRY_LOCK);
+		}
+
+		/*
+		 * Besides huge zero pages the only other thing that gets
+		 * downgraded are empty entries which don't need to be
+		 * unmapped.
+		 */
+		if (pmd_downgrade && dax_is_zero_entry(entry))
+			unmap_mapping_range(mapping,
+				(index << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
+
 		spin_lock_irq(&mapping->tree_lock);
-		err = radix_tree_insert(&mapping->page_tree, index, entry);
+
+		if (pmd_downgrade) {
+			radix_tree_delete(&mapping->page_tree, index);
+			mapping->nrexceptional--;
+			dax_wake_mapping_entry_waiter(mapping, index, entry,
+					true);
+		}
+
+		entry = dax_radix_locked_entry(0, size_flag | RADIX_DAX_EMPTY);
+
+		err = __radix_tree_insert(&mapping->page_tree, index,
+				dax_radix_order(entry), entry);
 		radix_tree_preload_end();
 		if (err) {
 			spin_unlock_irq(&mapping->tree_lock);
-			/* Someone already created the entry? */
-			if (err == -EEXIST)
+			/*
+			 * Someone already created the entry?  This is a
+			 * normal failure when inserting PMDs in a range
+			 * that already contains PTEs.  In that case we want
+			 * to return -EEXIST immediately.
+			 */
+			if (err == -EEXIST && !(size_flag & RADIX_DAX_PMD))
 				goto restart;
+			/*
+			 * Our insertion of a DAX PMD entry failed, most
+			 * likely because it collided with a PTE sized entry
+			 * at a different index in the PMD range.  We haven't
+			 * inserted anything into the radix tree and have no
+			 * waiters to wake.
+			 */
 			return ERR_PTR(err);
 		}
 		/* Good, we have inserted empty locked entry into the tree. */
@@ -466,6 +565,7 @@ restart:
 		return page;
 	}
 	entry = lock_slot(mapping, slot);
+ out_unlock:
 	spin_unlock_irq(&mapping->tree_lock);
 	return entry;
 }
@@ -473,9 +573,9 @@ restart:
 /*
  * We do not necessarily hold the mapping->tree_lock when we call this
  * function so it is possible that 'entry' is no longer a valid item in the
- * radix tree.  This is okay, though, because all we really need to do is to
- * find the correct waitqueue where tasks might be sleeping waiting for that
- * old 'entry' and wake them.
+ * radix tree.  This is okay because all we really need to do is to find the
+ * correct waitqueue where tasks might be waiting for that old 'entry' and
+ * wake them.
  */
 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 		pgoff_t index, void *entry, bool wake_all)
@@ -588,11 +688,17 @@ static int copy_user_dax(struct block_device *bdev, sector_t sector, size_t size
 	return 0;
 }
 
-#define DAX_PMD_INDEX(page_index) (page_index & (PMD_MASK >> PAGE_SHIFT))
-
+/*
+ * By this point grab_mapping_entry() has ensured that we have a locked entry
+ * of the appropriate size so we don't have to worry about downgrading PMDs to
+ * PTEs.  If we happen to be trying to insert a PTE and there is a PMD
+ * already in the tree, we will skip the insertion and just dirty the PMD as
+ * appropriate.
+ */
 static void *dax_insert_mapping_entry(struct address_space *mapping,
 				      struct vm_fault *vmf,
-				      void *entry, sector_t sector)
+				      void *entry, sector_t sector,
+				      unsigned long flags)
 {
 	struct radix_tree_root *page_tree = &mapping->page_tree;
 	int error = 0;
@@ -615,22 +721,35 @@ static void *dax_insert_mapping_entry(struct address_space *mapping,
 		error = radix_tree_preload(vmf->gfp_mask & ~__GFP_HIGHMEM);
 		if (error)
 			return ERR_PTR(error);
+	} else if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_HZP)) {
+		/* replacing huge zero page with PMD block mapping */
+		unmap_mapping_range(mapping,
+			(vmf->pgoff << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
 	}
 
 	spin_lock_irq(&mapping->tree_lock);
-	new_entry = (void *)((unsigned long)RADIX_DAX_ENTRY(sector, false) |
-		       RADIX_DAX_ENTRY_LOCK);
+	new_entry = dax_radix_locked_entry(sector, flags);
+
 	if (hole_fill) {
 		__delete_from_page_cache(entry, NULL);
 		/* Drop pagecache reference */
 		put_page(entry);
-		error = radix_tree_insert(page_tree, index, new_entry);
+		error = __radix_tree_insert(page_tree, index,
+				dax_radix_order(new_entry), new_entry);
 		if (error) {
 			new_entry = ERR_PTR(error);
 			goto unlock;
 		}
 		mapping->nrexceptional++;
-	} else {
+	} else if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
+		/*
+		 * Only swap our new entry into the radix tree if the current
+		 * entry is a zero page or an empty entry.  If a normal PTE or
+		 * PMD entry is already in the tree, we leave it alone.  This
+		 * means that if we are trying to insert a PTE and the
+		 * existing entry is a PMD, we will just leave the PMD in the
+		 * tree and dirty it if necessary.
+		 */
 		void **slot;
 		void *ret;
 
@@ -660,7 +779,6 @@ static int dax_writeback_one(struct block_device *bdev,
 		struct address_space *mapping, pgoff_t index, void *entry)
 {
 	struct radix_tree_root *page_tree = &mapping->page_tree;
-	int type = RADIX_DAX_TYPE(entry);
 	struct radix_tree_node *node;
 	struct blk_dax_ctl dax;
 	void **slot;
@@ -681,13 +799,21 @@ static int dax_writeback_one(struct block_device *bdev,
 	if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
 		goto unlock;
 
-	if (WARN_ON_ONCE(type != RADIX_DAX_PTE && type != RADIX_DAX_PMD)) {
+	if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
+				dax_is_zero_entry(entry))) {
 		ret = -EIO;
 		goto unlock;
 	}
 
-	dax.sector = RADIX_DAX_SECTOR(entry);
-	dax.size = (type == RADIX_DAX_PMD ? PMD_SIZE : PAGE_SIZE);
+	/*
+	 * Even if dax_writeback_mapping_range() was given a wbc->range_start
+	 * in the middle of a PMD, the 'index' we are given will be aligned to
+	 * the start index of the PMD, as will the sector we pull from
+	 * 'entry'.  This allows us to flush for PMD_SIZE and not have to
+	 * worry about partial PMD writebacks.
+	 */
+	dax.sector = dax_radix_sector(entry);
+	dax.size = PAGE_SIZE << dax_radix_order(entry);
 	spin_unlock_irq(&mapping->tree_lock);
 
 	/*
@@ -726,12 +852,11 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 		struct block_device *bdev, struct writeback_control *wbc)
 {
 	struct inode *inode = mapping->host;
-	pgoff_t start_index, end_index, pmd_index;
+	pgoff_t start_index, end_index;
 	pgoff_t indices[PAGEVEC_SIZE];
 	struct pagevec pvec;
 	bool done = false;
 	int i, ret = 0;
-	void *entry;
 
 	if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
 		return -EIO;
@@ -741,15 +866,6 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 
 	start_index = wbc->range_start >> PAGE_SHIFT;
 	end_index = wbc->range_end >> PAGE_SHIFT;
-	pmd_index = DAX_PMD_INDEX(start_index);
-
-	rcu_read_lock();
-	entry = radix_tree_lookup(&mapping->page_tree, pmd_index);
-	rcu_read_unlock();
-
-	/* see if the start of our range is covered by a PMD entry */
-	if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
-		start_index = pmd_index;
 
 	tag_pages_for_writeback(mapping, start_index, end_index);
 
@@ -794,7 +910,7 @@ static int dax_insert_mapping(struct address_space *mapping,
 		return PTR_ERR(dax.addr);
 	dax_unmap_atomic(bdev, &dax);
 
-	ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector);
+	ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector, 0);
 	if (IS_ERR(ret))
 		return PTR_ERR(ret);
 	*entryp = ret;
@@ -841,7 +957,7 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	bh.b_bdev = inode->i_sb->s_bdev;
 	bh.b_size = PAGE_SIZE;
 
-	entry = grab_mapping_entry(mapping, vmf->pgoff);
+	entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
 	if (IS_ERR(entry)) {
 		error = PTR_ERR(entry);
 		goto out;
@@ -1162,7 +1278,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	if (pos >= i_size_read(inode))
 		return VM_FAULT_SIGBUS;
 
-	entry = grab_mapping_entry(mapping, vmf->pgoff);
+	entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
 	if (IS_ERR(entry)) {
 		error = PTR_ERR(entry);
 		goto out;
@@ -1264,4 +1380,191 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	return VM_FAULT_NOPAGE | major;
 }
 EXPORT_SYMBOL_GPL(dax_iomap_fault);
+
+#ifdef CONFIG_FS_DAX_PMD
+/*
+ * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
+ * more often than one might expect in the below functions.
+ */
+#define PG_PMD_COLOUR	((PMD_SIZE >> PAGE_SHIFT) - 1)
+
+static int dax_pmd_insert_mapping(struct vm_area_struct *vma, pmd_t *pmd,
+		struct vm_fault *vmf, unsigned long address,
+		struct iomap *iomap, loff_t pos, bool write, void **entryp)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	struct block_device *bdev = iomap->bdev;
+	struct blk_dax_ctl dax = {
+		.sector = dax_iomap_sector(iomap, pos),
+		.size = PMD_SIZE,
+	};
+	long length = dax_map_atomic(bdev, &dax);
+	void *ret;
+
+	if (length < 0) /* dax_map_atomic() failed */
+		return VM_FAULT_FALLBACK;
+	if (length < PMD_SIZE)
+		goto unmap_fallback;
+	if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR)
+		goto unmap_fallback;
+	if (!pfn_t_devmap(dax.pfn))
+		goto unmap_fallback;
+
+	dax_unmap_atomic(bdev, &dax);
+
+	ret = dax_insert_mapping_entry(mapping, vmf, *entryp, dax.sector,
+			RADIX_DAX_PMD);
+	if (IS_ERR(ret))
+		return VM_FAULT_FALLBACK;
+	*entryp = ret;
+
+	return vmf_insert_pfn_pmd(vma, address, pmd, dax.pfn, write);
+
+ unmap_fallback:
+	dax_unmap_atomic(bdev, &dax);
+	return VM_FAULT_FALLBACK;
+}
+
+static int dax_pmd_load_hole(struct vm_area_struct *vma, pmd_t *pmd,
+		struct vm_fault *vmf, unsigned long address,
+		struct iomap *iomap, void **entryp)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	unsigned long pmd_addr = address & PMD_MASK;
+	struct page *zero_page;
+	spinlock_t *ptl;
+	pmd_t pmd_entry;
+	void *ret;
+
+	zero_page = get_huge_zero_page();
+
+	if (unlikely(!zero_page))
+		return VM_FAULT_FALLBACK;
+
+	ret = dax_insert_mapping_entry(mapping, vmf, *entryp, 0,
+			RADIX_DAX_PMD | RADIX_DAX_HZP);
+	if (IS_ERR(ret))
+		return VM_FAULT_FALLBACK;
+	*entryp = ret;
+
+	ptl = pmd_lock(vma->vm_mm, pmd);
+	if (!pmd_none(*pmd)) {
+		spin_unlock(ptl);
+		return VM_FAULT_FALLBACK;
+	}
+
+	pmd_entry = mk_pmd(zero_page, vma->vm_page_prot);
+	pmd_entry = pmd_mkhuge(pmd_entry);
+	set_pmd_at(vma->vm_mm, pmd_addr, pmd, pmd_entry);
+	spin_unlock(ptl);
+	return VM_FAULT_NOPAGE;
+}
+
+int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
+		pmd_t *pmd, unsigned int flags, struct iomap_ops *ops)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	unsigned long pmd_addr = address & PMD_MASK;
+	bool write = flags & FAULT_FLAG_WRITE;
+	unsigned int iomap_flags = write ? IOMAP_WRITE : 0;
+	struct inode *inode = mapping->host;
+	int result = VM_FAULT_FALLBACK;
+	struct iomap iomap = { 0 };
+	pgoff_t max_pgoff, pgoff;
+	struct vm_fault vmf;
+	void *entry;
+	loff_t pos;
+	int error;
+
+	/* Fall back to PTEs if we're going to COW */
+	if (write && !(vma->vm_flags & VM_SHARED)) {
+		split_huge_pmd(vma, pmd, address);
+		goto fallback;
+	}
+
+	/* If the PMD would extend outside the VMA */
+	if (pmd_addr < vma->vm_start)
+		goto fallback;
+	if ((pmd_addr + PMD_SIZE) > vma->vm_end)
+		goto fallback;
+
+	/*
+	 * Check whether offset isn't beyond end of file now. Caller is
+	 * supposed to hold locks serializing us with truncate / punch hole so
+	 * this is a reliable test.
+	 */
+	pgoff = linear_page_index(vma, pmd_addr);
+	max_pgoff = (i_size_read(inode) - 1) >> PAGE_SHIFT;
+
+	if (pgoff > max_pgoff)
+		return VM_FAULT_SIGBUS;
+
+	/* If the PMD would extend beyond the file size */
+	if ((pgoff | PG_PMD_COLOUR) > max_pgoff)
+		goto fallback;
+
+	/*
+	 * grab_mapping_entry() will make sure we get a 2M empty entry, a DAX
+	 * PMD or a HZP entry.  If it can't (because a 4k page is already in
+	 * the tree, for instance), it will return -EEXIST and we just fall
+	 * back to 4k entries.
+	 */
+	entry = grab_mapping_entry(mapping, pgoff, RADIX_DAX_PMD);
+	if (IS_ERR(entry))
+		goto fallback;
+
+	/*
+	 * Note that we don't use iomap_apply here.  We aren't doing I/O, only
+	 * setting up a mapping, so really we're using iomap_begin() as a way
+	 * to look up our filesystem block.
+	 */
+	pos = (loff_t)pgoff << PAGE_SHIFT;
+	error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap);
+	if (error)
+		goto unlock_entry;
+	if (iomap.offset + iomap.length < pos + PMD_SIZE)
+		goto finish_iomap;
+
+	vmf.pgoff = pgoff;
+	vmf.flags = flags;
+	vmf.gfp_mask = mapping_gfp_mask(mapping) | __GFP_IO;
+
+	switch (iomap.type) {
+	case IOMAP_MAPPED:
+		result = dax_pmd_insert_mapping(vma, pmd, &vmf, address,
+				&iomap, pos, write, &entry);
+		break;
+	case IOMAP_UNWRITTEN:
+	case IOMAP_HOLE:
+		if (WARN_ON_ONCE(write))
+			goto finish_iomap;
+		result = dax_pmd_load_hole(vma, pmd, &vmf, address, &iomap,
+				&entry);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		break;
+	}
+
+ finish_iomap:
+	if (ops->iomap_end) {
+		if (result == VM_FAULT_FALLBACK) {
+			ops->iomap_end(inode, pos, PMD_SIZE, 0, iomap_flags,
+					&iomap);
+		} else {
+			error = ops->iomap_end(inode, pos, PMD_SIZE, PMD_SIZE,
+					iomap_flags, &iomap);
+			if (error)
+				result = VM_FAULT_FALLBACK;
+		}
+	}
+ unlock_entry:
+	put_locked_mapping_entry(mapping, pgoff, entry);
+ fallback:
+	if (result == VM_FAULT_FALLBACK)
+		count_vm_event(THP_FAULT_FALLBACK);
+	return result;
+}
+EXPORT_SYMBOL_GPL(dax_iomap_pmd_fault);
+#endif /* CONFIG_FS_DAX_PMD */
 #endif /* CONFIG_FS_IOMAP */
diff --git a/include/linux/dax.h b/include/linux/dax.h
index e9ea78c..8d1a5c4 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -9,20 +9,32 @@
 struct iomap_ops;
 
 /*
- * We use lowest available bit in exceptional entry for locking, other two
- * bits to determine entry type. In total 3 special bits.
+ * We use lowest available bit in exceptional entry for locking, one bit for
+ * the entry size (PMD) and two more to tell us if the entry is a huge zero
+ * page (HZP) or an empty entry that is just used for locking.  In total four
+ * special bits.
+ *
+ * If the PMD bit isn't set the entry has size PAGE_SIZE, and if the HZP and
+ * EMPTY bits aren't set the entry is a normal DAX entry with a filesystem
+ * block allocation.
  */
-#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 3)
+#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 4)
 #define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
-#define RADIX_DAX_PTE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
-#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
-#define RADIX_DAX_TYPE_MASK (RADIX_DAX_PTE | RADIX_DAX_PMD)
-#define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_TYPE_MASK)
-#define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
-#define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
-		RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE) | \
-		RADIX_TREE_EXCEPTIONAL_ENTRY))
+#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
+#define RADIX_DAX_HZP (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
+#define RADIX_DAX_EMPTY (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 3))
 
+static inline unsigned long dax_radix_sector(void *entry)
+{
+	return (unsigned long)entry >> RADIX_DAX_SHIFT;
+}
+
+static inline void *dax_radix_locked_entry(sector_t sector, unsigned long flags)
+{
+	return (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY | flags |
+			((unsigned long)sector << RADIX_DAX_SHIFT) |
+			RADIX_DAX_ENTRY_LOCK);
+}
 
 ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_ops *ops);
@@ -67,6 +79,27 @@ static inline int dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
 	return VM_FAULT_FALLBACK;
 }
 
+#ifdef CONFIG_FS_DAX_PMD
+static inline unsigned int dax_radix_order(void *entry)
+{
+	if ((unsigned long)entry & RADIX_DAX_PMD)
+		return PMD_SHIFT - PAGE_SHIFT;
+	return 0;
+}
+int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
+		pmd_t *pmd, unsigned int flags, struct iomap_ops *ops);
+#else
+static inline unsigned int dax_radix_order(void *entry)
+{
+	return 0;
+}
+static inline int dax_iomap_pmd_fault(struct vm_area_struct *vma,
+		unsigned long address, pmd_t *pmd, unsigned int flags,
+		struct iomap_ops *ops)
+{
+	return VM_FAULT_FALLBACK;
+}
+#endif
 int dax_pfn_mkwrite(struct vm_area_struct *, struct vm_fault *);
 #define dax_mkwrite(vma, vmf, gb)	dax_fault(vma, vmf, gb)
 
diff --git a/mm/filemap.c b/mm/filemap.c
index a596462..592e6e9 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -611,8 +611,7 @@ static int page_cache_tree_insert(struct address_space *mapping,
 		} else {
 			/* DAX can replace empty locked entry with a hole */
 			WARN_ON_ONCE(p !=
-				(void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
-					 RADIX_DAX_ENTRY_LOCK));
+				dax_radix_locked_entry(0, RADIX_DAX_EMPTY));
 			/* DAX accounts exceptional entries as normal pages */
 			if (node)
 				workingset_node_pages_dec(node);
-- 
2.9.0


^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 16/17] xfs: use struct iomap based DAX PMD fault path
  2016-10-12 22:50 ` Ross Zwisler
                     ` (2 preceding siblings ...)
  (?)
@ 2016-10-12 22:50   ` Ross Zwisler
  -1 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner, linux-nvdimm,
	Christoph Hellwig, linux-xfs, linux-mm, Andreas Dilger,
	Alexander Viro, linux-fsdevel, Jan Kara, linux-ext4,
	Andrew Morton

Switch xfs_filemap_pmd_fault() from using dax_pmd_fault() to the new and
improved dax_iomap_pmd_fault().  Also, now that it has no more users,
remove xfs_get_blocks_dax_fault().

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/xfs/xfs_aops.c | 26 +++++---------------------
 fs/xfs/xfs_aops.h |  3 ---
 fs/xfs/xfs_file.c |  2 +-
 3 files changed, 6 insertions(+), 25 deletions(-)

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 0e2a931..1c73d0a 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -1298,8 +1298,7 @@ __xfs_get_blocks(
 	sector_t		iblock,
 	struct buffer_head	*bh_result,
 	int			create,
-	bool			direct,
-	bool			dax_fault)
+	bool			direct)
 {
 	struct xfs_inode	*ip = XFS_I(inode);
 	struct xfs_mount	*mp = ip->i_mount;
@@ -1420,13 +1419,8 @@ __xfs_get_blocks(
 		if (ISUNWRITTEN(&imap))
 			set_buffer_unwritten(bh_result);
 		/* direct IO needs special help */
-		if (create) {
-			if (dax_fault)
-				ASSERT(!ISUNWRITTEN(&imap));
-			else
-				xfs_map_direct(inode, bh_result, &imap, offset,
-						is_cow);
-		}
+		if (create)
+			xfs_map_direct(inode, bh_result, &imap, offset, is_cow);
 	}
 
 	/*
@@ -1466,7 +1460,7 @@ xfs_get_blocks(
 	struct buffer_head	*bh_result,
 	int			create)
 {
-	return __xfs_get_blocks(inode, iblock, bh_result, create, false, false);
+	return __xfs_get_blocks(inode, iblock, bh_result, create, false);
 }
 
 int
@@ -1476,17 +1470,7 @@ xfs_get_blocks_direct(
 	struct buffer_head	*bh_result,
 	int			create)
 {
-	return __xfs_get_blocks(inode, iblock, bh_result, create, true, false);
-}
-
-int
-xfs_get_blocks_dax_fault(
-	struct inode		*inode,
-	sector_t		iblock,
-	struct buffer_head	*bh_result,
-	int			create)
-{
-	return __xfs_get_blocks(inode, iblock, bh_result, create, true, true);
+	return __xfs_get_blocks(inode, iblock, bh_result, create, true);
 }
 
 /*
diff --git a/fs/xfs/xfs_aops.h b/fs/xfs/xfs_aops.h
index b3c6634..34dc00d 100644
--- a/fs/xfs/xfs_aops.h
+++ b/fs/xfs/xfs_aops.h
@@ -59,9 +59,6 @@ int	xfs_get_blocks(struct inode *inode, sector_t offset,
 		       struct buffer_head *map_bh, int create);
 int	xfs_get_blocks_direct(struct inode *inode, sector_t offset,
 			      struct buffer_head *map_bh, int create);
-int	xfs_get_blocks_dax_fault(struct inode *inode, sector_t offset,
-			         struct buffer_head *map_bh, int create);
-
 int	xfs_end_io_direct_write(struct kiocb *iocb, loff_t offset,
 		ssize_t size, void *private);
 int	xfs_setfilesize(struct xfs_inode *ip, xfs_off_t offset, size_t size);
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 8f12152..7b13dda 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1750,7 +1750,7 @@ xfs_filemap_pmd_fault(
 	}
 
 	xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
-	ret = dax_pmd_fault(vma, addr, pmd, flags, xfs_get_blocks_dax_fault);
+	ret = dax_iomap_pmd_fault(vma, addr, pmd, flags, &xfs_iomap_ops);
 	xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
 
 	if (flags & FAULT_FLAG_WRITE)
-- 
2.9.0

_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 16/17] xfs: use struct iomap based DAX PMD fault path
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

Switch xfs_filemap_pmd_fault() from using dax_pmd_fault() to the new and
improved dax_iomap_pmd_fault().  Also, now that it has no more users,
remove xfs_get_blocks_dax_fault().

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/xfs/xfs_aops.c | 26 +++++---------------------
 fs/xfs/xfs_aops.h |  3 ---
 fs/xfs/xfs_file.c |  2 +-
 3 files changed, 6 insertions(+), 25 deletions(-)

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 0e2a931..1c73d0a 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -1298,8 +1298,7 @@ __xfs_get_blocks(
 	sector_t		iblock,
 	struct buffer_head	*bh_result,
 	int			create,
-	bool			direct,
-	bool			dax_fault)
+	bool			direct)
 {
 	struct xfs_inode	*ip = XFS_I(inode);
 	struct xfs_mount	*mp = ip->i_mount;
@@ -1420,13 +1419,8 @@ __xfs_get_blocks(
 		if (ISUNWRITTEN(&imap))
 			set_buffer_unwritten(bh_result);
 		/* direct IO needs special help */
-		if (create) {
-			if (dax_fault)
-				ASSERT(!ISUNWRITTEN(&imap));
-			else
-				xfs_map_direct(inode, bh_result, &imap, offset,
-						is_cow);
-		}
+		if (create)
+			xfs_map_direct(inode, bh_result, &imap, offset, is_cow);
 	}
 
 	/*
@@ -1466,7 +1460,7 @@ xfs_get_blocks(
 	struct buffer_head	*bh_result,
 	int			create)
 {
-	return __xfs_get_blocks(inode, iblock, bh_result, create, false, false);
+	return __xfs_get_blocks(inode, iblock, bh_result, create, false);
 }
 
 int
@@ -1476,17 +1470,7 @@ xfs_get_blocks_direct(
 	struct buffer_head	*bh_result,
 	int			create)
 {
-	return __xfs_get_blocks(inode, iblock, bh_result, create, true, false);
-}
-
-int
-xfs_get_blocks_dax_fault(
-	struct inode		*inode,
-	sector_t		iblock,
-	struct buffer_head	*bh_result,
-	int			create)
-{
-	return __xfs_get_blocks(inode, iblock, bh_result, create, true, true);
+	return __xfs_get_blocks(inode, iblock, bh_result, create, true);
 }
 
 /*
diff --git a/fs/xfs/xfs_aops.h b/fs/xfs/xfs_aops.h
index b3c6634..34dc00d 100644
--- a/fs/xfs/xfs_aops.h
+++ b/fs/xfs/xfs_aops.h
@@ -59,9 +59,6 @@ int	xfs_get_blocks(struct inode *inode, sector_t offset,
 		       struct buffer_head *map_bh, int create);
 int	xfs_get_blocks_direct(struct inode *inode, sector_t offset,
 			      struct buffer_head *map_bh, int create);
-int	xfs_get_blocks_dax_fault(struct inode *inode, sector_t offset,
-			         struct buffer_head *map_bh, int create);
-
 int	xfs_end_io_direct_write(struct kiocb *iocb, loff_t offset,
 		ssize_t size, void *private);
 int	xfs_setfilesize(struct xfs_inode *ip, xfs_off_t offset, size_t size);
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 8f12152..7b13dda 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1750,7 +1750,7 @@ xfs_filemap_pmd_fault(
 	}
 
 	xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
-	ret = dax_pmd_fault(vma, addr, pmd, flags, xfs_get_blocks_dax_fault);
+	ret = dax_iomap_pmd_fault(vma, addr, pmd, flags, &xfs_iomap_ops);
 	xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
 
 	if (flags & FAULT_FLAG_WRITE)
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 16/17] xfs: use struct iomap based DAX PMD fault path
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

Switch xfs_filemap_pmd_fault() from using dax_pmd_fault() to the new and
improved dax_iomap_pmd_fault().  Also, now that it has no more users,
remove xfs_get_blocks_dax_fault().

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/xfs/xfs_aops.c | 26 +++++---------------------
 fs/xfs/xfs_aops.h |  3 ---
 fs/xfs/xfs_file.c |  2 +-
 3 files changed, 6 insertions(+), 25 deletions(-)

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 0e2a931..1c73d0a 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -1298,8 +1298,7 @@ __xfs_get_blocks(
 	sector_t		iblock,
 	struct buffer_head	*bh_result,
 	int			create,
-	bool			direct,
-	bool			dax_fault)
+	bool			direct)
 {
 	struct xfs_inode	*ip = XFS_I(inode);
 	struct xfs_mount	*mp = ip->i_mount;
@@ -1420,13 +1419,8 @@ __xfs_get_blocks(
 		if (ISUNWRITTEN(&imap))
 			set_buffer_unwritten(bh_result);
 		/* direct IO needs special help */
-		if (create) {
-			if (dax_fault)
-				ASSERT(!ISUNWRITTEN(&imap));
-			else
-				xfs_map_direct(inode, bh_result, &imap, offset,
-						is_cow);
-		}
+		if (create)
+			xfs_map_direct(inode, bh_result, &imap, offset, is_cow);
 	}
 
 	/*
@@ -1466,7 +1460,7 @@ xfs_get_blocks(
 	struct buffer_head	*bh_result,
 	int			create)
 {
-	return __xfs_get_blocks(inode, iblock, bh_result, create, false, false);
+	return __xfs_get_blocks(inode, iblock, bh_result, create, false);
 }
 
 int
@@ -1476,17 +1470,7 @@ xfs_get_blocks_direct(
 	struct buffer_head	*bh_result,
 	int			create)
 {
-	return __xfs_get_blocks(inode, iblock, bh_result, create, true, false);
-}
-
-int
-xfs_get_blocks_dax_fault(
-	struct inode		*inode,
-	sector_t		iblock,
-	struct buffer_head	*bh_result,
-	int			create)
-{
-	return __xfs_get_blocks(inode, iblock, bh_result, create, true, true);
+	return __xfs_get_blocks(inode, iblock, bh_result, create, true);
 }
 
 /*
diff --git a/fs/xfs/xfs_aops.h b/fs/xfs/xfs_aops.h
index b3c6634..34dc00d 100644
--- a/fs/xfs/xfs_aops.h
+++ b/fs/xfs/xfs_aops.h
@@ -59,9 +59,6 @@ int	xfs_get_blocks(struct inode *inode, sector_t offset,
 		       struct buffer_head *map_bh, int create);
 int	xfs_get_blocks_direct(struct inode *inode, sector_t offset,
 			      struct buffer_head *map_bh, int create);
-int	xfs_get_blocks_dax_fault(struct inode *inode, sector_t offset,
-			         struct buffer_head *map_bh, int create);
-
 int	xfs_end_io_direct_write(struct kiocb *iocb, loff_t offset,
 		ssize_t size, void *private);
 int	xfs_setfilesize(struct xfs_inode *ip, xfs_off_t offset, size_t size);
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 8f12152..7b13dda 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1750,7 +1750,7 @@ xfs_filemap_pmd_fault(
 	}
 
 	xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
-	ret = dax_pmd_fault(vma, addr, pmd, flags, xfs_get_blocks_dax_fault);
+	ret = dax_iomap_pmd_fault(vma, addr, pmd, flags, &xfs_iomap_ops);
 	xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
 
 	if (flags & FAULT_FLAG_WRITE)
-- 
2.9.0

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
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^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 16/17] xfs: use struct iomap based DAX PMD fault path
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel-u79uwXL29TY76Z2rM5mHXA
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner,
	linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw, Christoph Hellwig,
	linux-xfs-u79uwXL29TY76Z2rM5mHXA,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg, Andreas Dilger, Alexander Viro,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA, Jan Kara,
	linux-ext4-u79uwXL29TY76Z2rM5mHXA, Andrew Morton

Switch xfs_filemap_pmd_fault() from using dax_pmd_fault() to the new and
improved dax_iomap_pmd_fault().  Also, now that it has no more users,
remove xfs_get_blocks_dax_fault().

Signed-off-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Reviewed-by: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>
---
 fs/xfs/xfs_aops.c | 26 +++++---------------------
 fs/xfs/xfs_aops.h |  3 ---
 fs/xfs/xfs_file.c |  2 +-
 3 files changed, 6 insertions(+), 25 deletions(-)

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 0e2a931..1c73d0a 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -1298,8 +1298,7 @@ __xfs_get_blocks(
 	sector_t		iblock,
 	struct buffer_head	*bh_result,
 	int			create,
-	bool			direct,
-	bool			dax_fault)
+	bool			direct)
 {
 	struct xfs_inode	*ip = XFS_I(inode);
 	struct xfs_mount	*mp = ip->i_mount;
@@ -1420,13 +1419,8 @@ __xfs_get_blocks(
 		if (ISUNWRITTEN(&imap))
 			set_buffer_unwritten(bh_result);
 		/* direct IO needs special help */
-		if (create) {
-			if (dax_fault)
-				ASSERT(!ISUNWRITTEN(&imap));
-			else
-				xfs_map_direct(inode, bh_result, &imap, offset,
-						is_cow);
-		}
+		if (create)
+			xfs_map_direct(inode, bh_result, &imap, offset, is_cow);
 	}
 
 	/*
@@ -1466,7 +1460,7 @@ xfs_get_blocks(
 	struct buffer_head	*bh_result,
 	int			create)
 {
-	return __xfs_get_blocks(inode, iblock, bh_result, create, false, false);
+	return __xfs_get_blocks(inode, iblock, bh_result, create, false);
 }
 
 int
@@ -1476,17 +1470,7 @@ xfs_get_blocks_direct(
 	struct buffer_head	*bh_result,
 	int			create)
 {
-	return __xfs_get_blocks(inode, iblock, bh_result, create, true, false);
-}
-
-int
-xfs_get_blocks_dax_fault(
-	struct inode		*inode,
-	sector_t		iblock,
-	struct buffer_head	*bh_result,
-	int			create)
-{
-	return __xfs_get_blocks(inode, iblock, bh_result, create, true, true);
+	return __xfs_get_blocks(inode, iblock, bh_result, create, true);
 }
 
 /*
diff --git a/fs/xfs/xfs_aops.h b/fs/xfs/xfs_aops.h
index b3c6634..34dc00d 100644
--- a/fs/xfs/xfs_aops.h
+++ b/fs/xfs/xfs_aops.h
@@ -59,9 +59,6 @@ int	xfs_get_blocks(struct inode *inode, sector_t offset,
 		       struct buffer_head *map_bh, int create);
 int	xfs_get_blocks_direct(struct inode *inode, sector_t offset,
 			      struct buffer_head *map_bh, int create);
-int	xfs_get_blocks_dax_fault(struct inode *inode, sector_t offset,
-			         struct buffer_head *map_bh, int create);
-
 int	xfs_end_io_direct_write(struct kiocb *iocb, loff_t offset,
 		ssize_t size, void *private);
 int	xfs_setfilesize(struct xfs_inode *ip, xfs_off_t offset, size_t size);
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 8f12152..7b13dda 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1750,7 +1750,7 @@ xfs_filemap_pmd_fault(
 	}
 
 	xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
-	ret = dax_pmd_fault(vma, addr, pmd, flags, xfs_get_blocks_dax_fault);
+	ret = dax_iomap_pmd_fault(vma, addr, pmd, flags, &xfs_iomap_ops);
 	xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
 
 	if (flags & FAULT_FLAG_WRITE)
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 16/17] xfs: use struct iomap based DAX PMD fault path
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

Switch xfs_filemap_pmd_fault() from using dax_pmd_fault() to the new and
improved dax_iomap_pmd_fault().  Also, now that it has no more users,
remove xfs_get_blocks_dax_fault().

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/xfs/xfs_aops.c | 26 +++++---------------------
 fs/xfs/xfs_aops.h |  3 ---
 fs/xfs/xfs_file.c |  2 +-
 3 files changed, 6 insertions(+), 25 deletions(-)

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 0e2a931..1c73d0a 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -1298,8 +1298,7 @@ __xfs_get_blocks(
 	sector_t		iblock,
 	struct buffer_head	*bh_result,
 	int			create,
-	bool			direct,
-	bool			dax_fault)
+	bool			direct)
 {
 	struct xfs_inode	*ip = XFS_I(inode);
 	struct xfs_mount	*mp = ip->i_mount;
@@ -1420,13 +1419,8 @@ __xfs_get_blocks(
 		if (ISUNWRITTEN(&imap))
 			set_buffer_unwritten(bh_result);
 		/* direct IO needs special help */
-		if (create) {
-			if (dax_fault)
-				ASSERT(!ISUNWRITTEN(&imap));
-			else
-				xfs_map_direct(inode, bh_result, &imap, offset,
-						is_cow);
-		}
+		if (create)
+			xfs_map_direct(inode, bh_result, &imap, offset, is_cow);
 	}
 
 	/*
@@ -1466,7 +1460,7 @@ xfs_get_blocks(
 	struct buffer_head	*bh_result,
 	int			create)
 {
-	return __xfs_get_blocks(inode, iblock, bh_result, create, false, false);
+	return __xfs_get_blocks(inode, iblock, bh_result, create, false);
 }
 
 int
@@ -1476,17 +1470,7 @@ xfs_get_blocks_direct(
 	struct buffer_head	*bh_result,
 	int			create)
 {
-	return __xfs_get_blocks(inode, iblock, bh_result, create, true, false);
-}
-
-int
-xfs_get_blocks_dax_fault(
-	struct inode		*inode,
-	sector_t		iblock,
-	struct buffer_head	*bh_result,
-	int			create)
-{
-	return __xfs_get_blocks(inode, iblock, bh_result, create, true, true);
+	return __xfs_get_blocks(inode, iblock, bh_result, create, true);
 }
 
 /*
diff --git a/fs/xfs/xfs_aops.h b/fs/xfs/xfs_aops.h
index b3c6634..34dc00d 100644
--- a/fs/xfs/xfs_aops.h
+++ b/fs/xfs/xfs_aops.h
@@ -59,9 +59,6 @@ int	xfs_get_blocks(struct inode *inode, sector_t offset,
 		       struct buffer_head *map_bh, int create);
 int	xfs_get_blocks_direct(struct inode *inode, sector_t offset,
 			      struct buffer_head *map_bh, int create);
-int	xfs_get_blocks_dax_fault(struct inode *inode, sector_t offset,
-			         struct buffer_head *map_bh, int create);
-
 int	xfs_end_io_direct_write(struct kiocb *iocb, loff_t offset,
 		ssize_t size, void *private);
 int	xfs_setfilesize(struct xfs_inode *ip, xfs_off_t offset, size_t size);
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 8f12152..7b13dda 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1750,7 +1750,7 @@ xfs_filemap_pmd_fault(
 	}
 
 	xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
-	ret = dax_pmd_fault(vma, addr, pmd, flags, xfs_get_blocks_dax_fault);
+	ret = dax_iomap_pmd_fault(vma, addr, pmd, flags, &xfs_iomap_ops);
 	xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
 
 	if (flags & FAULT_FLAG_WRITE)
-- 
2.9.0


^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD
  2016-10-12 22:50 ` Ross Zwisler
                     ` (2 preceding siblings ...)
  (?)
@ 2016-10-12 22:50   ` Ross Zwisler
  -1 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner, linux-nvdimm,
	Christoph Hellwig, linux-xfs, linux-mm, Andreas Dilger,
	Alexander Viro, linux-fsdevel, Jan Kara, linux-ext4,
	Andrew Morton

Now that DAX PMD faults are once again working and are now participating in
DAX's radix tree locking scheme, allow their config option to be enabled.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
---
 fs/Kconfig | 1 -
 1 file changed, 1 deletion(-)

diff --git a/fs/Kconfig b/fs/Kconfig
index 2bc7ad7..b6f0fce 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -55,7 +55,6 @@ config FS_DAX_PMD
 	depends on FS_DAX
 	depends on ZONE_DEVICE
 	depends on TRANSPARENT_HUGEPAGE
-	depends on BROKEN
 
 endif # BLOCK
 
-- 
2.9.0

_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

Now that DAX PMD faults are once again working and are now participating in
DAX's radix tree locking scheme, allow their config option to be enabled.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
---
 fs/Kconfig | 1 -
 1 file changed, 1 deletion(-)

diff --git a/fs/Kconfig b/fs/Kconfig
index 2bc7ad7..b6f0fce 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -55,7 +55,6 @@ config FS_DAX_PMD
 	depends on FS_DAX
 	depends on ZONE_DEVICE
 	depends on TRANSPARENT_HUGEPAGE
-	depends on BROKEN
 
 endif # BLOCK
 
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

Now that DAX PMD faults are once again working and are now participating in
DAX's radix tree locking scheme, allow their config option to be enabled.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
---
 fs/Kconfig | 1 -
 1 file changed, 1 deletion(-)

diff --git a/fs/Kconfig b/fs/Kconfig
index 2bc7ad7..b6f0fce 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -55,7 +55,6 @@ config FS_DAX_PMD
 	depends on FS_DAX
 	depends on ZONE_DEVICE
 	depends on TRANSPARENT_HUGEPAGE
-	depends on BROKEN
 
 endif # BLOCK
 
-- 
2.9.0

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel-u79uwXL29TY76Z2rM5mHXA
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner,
	linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw, Christoph Hellwig,
	linux-xfs-u79uwXL29TY76Z2rM5mHXA,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg, Andreas Dilger, Alexander Viro,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA, Jan Kara,
	linux-ext4-u79uwXL29TY76Z2rM5mHXA, Andrew Morton

Now that DAX PMD faults are once again working and are now participating in
DAX's radix tree locking scheme, allow their config option to be enabled.

Signed-off-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
---
 fs/Kconfig | 1 -
 1 file changed, 1 deletion(-)

diff --git a/fs/Kconfig b/fs/Kconfig
index 2bc7ad7..b6f0fce 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -55,7 +55,6 @@ config FS_DAX_PMD
 	depends on FS_DAX
 	depends on ZONE_DEVICE
 	depends on TRANSPARENT_HUGEPAGE
-	depends on BROKEN
 
 endif # BLOCK
 
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v6 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD
@ 2016-10-12 22:50   ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-12 22:50 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

Now that DAX PMD faults are once again working and are now participating in
DAX's radix tree locking scheme, allow their config option to be enabled.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
---
 fs/Kconfig | 1 -
 1 file changed, 1 deletion(-)

diff --git a/fs/Kconfig b/fs/Kconfig
index 2bc7ad7..b6f0fce 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -55,7 +55,6 @@ config FS_DAX_PMD
 	depends on FS_DAX
 	depends on ZONE_DEVICE
 	depends on TRANSPARENT_HUGEPAGE
-	depends on BROKEN
 
 endif # BLOCK
 
-- 
2.9.0


^ permalink raw reply related	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 14/17] dax: move put_(un)locked_mapping_entry() in dax.c
  2016-10-12 22:50   ` Ross Zwisler
  (?)
@ 2016-10-13 15:11     ` Jan Kara
  -1 siblings, 0 replies; 126+ messages in thread
From: Jan Kara @ 2016-10-13 15:11 UTC (permalink / raw)
  To: Ross Zwisler
  Cc: linux-kernel, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

On Wed 12-10-16 16:50:19, Ross Zwisler wrote:
> No functional change.
> 
> The static functions put_locked_mapping_entry() and
> put_unlocked_mapping_entry() will soon be used in error cases in
> grab_mapping_entry(), so move their definitions above this function.
> 
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>

Looks good. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/dax.c | 50 +++++++++++++++++++++++++-------------------------
>  1 file changed, 25 insertions(+), 25 deletions(-)
> 
> diff --git a/fs/dax.c b/fs/dax.c
> index c45cc4d..0582c7c 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -382,6 +382,31 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
>  	}
>  }
>  
> +static void put_locked_mapping_entry(struct address_space *mapping,
> +				     pgoff_t index, void *entry)
> +{
> +	if (!radix_tree_exceptional_entry(entry)) {
> +		unlock_page(entry);
> +		put_page(entry);
> +	} else {
> +		dax_unlock_mapping_entry(mapping, index);
> +	}
> +}
> +
> +/*
> + * Called when we are done with radix tree entry we looked up via
> + * get_unlocked_mapping_entry() and which we didn't lock in the end.
> + */
> +static void put_unlocked_mapping_entry(struct address_space *mapping,
> +				       pgoff_t index, void *entry)
> +{
> +	if (!radix_tree_exceptional_entry(entry))
> +		return;
> +
> +	/* We have to wake up next waiter for the radix tree entry lock */
> +	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
> +}
> +
>  /*
>   * Find radix tree entry at given index. If it points to a page, return with
>   * the page locked. If it points to the exceptional entry, return with the
> @@ -486,31 +511,6 @@ void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
>  	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
>  }
>  
> -static void put_locked_mapping_entry(struct address_space *mapping,
> -				     pgoff_t index, void *entry)
> -{
> -	if (!radix_tree_exceptional_entry(entry)) {
> -		unlock_page(entry);
> -		put_page(entry);
> -	} else {
> -		dax_unlock_mapping_entry(mapping, index);
> -	}
> -}
> -
> -/*
> - * Called when we are done with radix tree entry we looked up via
> - * get_unlocked_mapping_entry() and which we didn't lock in the end.
> - */
> -static void put_unlocked_mapping_entry(struct address_space *mapping,
> -				       pgoff_t index, void *entry)
> -{
> -	if (!radix_tree_exceptional_entry(entry))
> -		return;
> -
> -	/* We have to wake up next waiter for the radix tree entry lock */
> -	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
> -}
> -
>  /*
>   * Delete exceptional DAX entry at @index from @mapping. Wait for radix tree
>   * entry to get unlocked before deleting it.
> -- 
> 2.9.0
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
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^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 14/17] dax: move put_(un)locked_mapping_entry() in dax.c
@ 2016-10-13 15:11     ` Jan Kara
  0 siblings, 0 replies; 126+ messages in thread
From: Jan Kara @ 2016-10-13 15:11 UTC (permalink / raw)
  To: Ross Zwisler
  Cc: linux-kernel, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

On Wed 12-10-16 16:50:19, Ross Zwisler wrote:
> No functional change.
> 
> The static functions put_locked_mapping_entry() and
> put_unlocked_mapping_entry() will soon be used in error cases in
> grab_mapping_entry(), so move their definitions above this function.
> 
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>

Looks good. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/dax.c | 50 +++++++++++++++++++++++++-------------------------
>  1 file changed, 25 insertions(+), 25 deletions(-)
> 
> diff --git a/fs/dax.c b/fs/dax.c
> index c45cc4d..0582c7c 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -382,6 +382,31 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
>  	}
>  }
>  
> +static void put_locked_mapping_entry(struct address_space *mapping,
> +				     pgoff_t index, void *entry)
> +{
> +	if (!radix_tree_exceptional_entry(entry)) {
> +		unlock_page(entry);
> +		put_page(entry);
> +	} else {
> +		dax_unlock_mapping_entry(mapping, index);
> +	}
> +}
> +
> +/*
> + * Called when we are done with radix tree entry we looked up via
> + * get_unlocked_mapping_entry() and which we didn't lock in the end.
> + */
> +static void put_unlocked_mapping_entry(struct address_space *mapping,
> +				       pgoff_t index, void *entry)
> +{
> +	if (!radix_tree_exceptional_entry(entry))
> +		return;
> +
> +	/* We have to wake up next waiter for the radix tree entry lock */
> +	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
> +}
> +
>  /*
>   * Find radix tree entry at given index. If it points to a page, return with
>   * the page locked. If it points to the exceptional entry, return with the
> @@ -486,31 +511,6 @@ void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
>  	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
>  }
>  
> -static void put_locked_mapping_entry(struct address_space *mapping,
> -				     pgoff_t index, void *entry)
> -{
> -	if (!radix_tree_exceptional_entry(entry)) {
> -		unlock_page(entry);
> -		put_page(entry);
> -	} else {
> -		dax_unlock_mapping_entry(mapping, index);
> -	}
> -}
> -
> -/*
> - * Called when we are done with radix tree entry we looked up via
> - * get_unlocked_mapping_entry() and which we didn't lock in the end.
> - */
> -static void put_unlocked_mapping_entry(struct address_space *mapping,
> -				       pgoff_t index, void *entry)
> -{
> -	if (!radix_tree_exceptional_entry(entry))
> -		return;
> -
> -	/* We have to wake up next waiter for the radix tree entry lock */
> -	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
> -}
> -
>  /*
>   * Delete exceptional DAX entry at @index from @mapping. Wait for radix tree
>   * entry to get unlocked before deleting it.
> -- 
> 2.9.0
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 14/17] dax: move put_(un)locked_mapping_entry() in dax.c
@ 2016-10-13 15:11     ` Jan Kara
  0 siblings, 0 replies; 126+ messages in thread
From: Jan Kara @ 2016-10-13 15:11 UTC (permalink / raw)
  To: Ross Zwisler
  Cc: linux-kernel, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

On Wed 12-10-16 16:50:19, Ross Zwisler wrote:
> No functional change.
> 
> The static functions put_locked_mapping_entry() and
> put_unlocked_mapping_entry() will soon be used in error cases in
> grab_mapping_entry(), so move their definitions above this function.
> 
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>

Looks good. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/dax.c | 50 +++++++++++++++++++++++++-------------------------
>  1 file changed, 25 insertions(+), 25 deletions(-)
> 
> diff --git a/fs/dax.c b/fs/dax.c
> index c45cc4d..0582c7c 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -382,6 +382,31 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
>  	}
>  }
>  
> +static void put_locked_mapping_entry(struct address_space *mapping,
> +				     pgoff_t index, void *entry)
> +{
> +	if (!radix_tree_exceptional_entry(entry)) {
> +		unlock_page(entry);
> +		put_page(entry);
> +	} else {
> +		dax_unlock_mapping_entry(mapping, index);
> +	}
> +}
> +
> +/*
> + * Called when we are done with radix tree entry we looked up via
> + * get_unlocked_mapping_entry() and which we didn't lock in the end.
> + */
> +static void put_unlocked_mapping_entry(struct address_space *mapping,
> +				       pgoff_t index, void *entry)
> +{
> +	if (!radix_tree_exceptional_entry(entry))
> +		return;
> +
> +	/* We have to wake up next waiter for the radix tree entry lock */
> +	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
> +}
> +
>  /*
>   * Find radix tree entry at given index. If it points to a page, return with
>   * the page locked. If it points to the exceptional entry, return with the
> @@ -486,31 +511,6 @@ void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
>  	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
>  }
>  
> -static void put_locked_mapping_entry(struct address_space *mapping,
> -				     pgoff_t index, void *entry)
> -{
> -	if (!radix_tree_exceptional_entry(entry)) {
> -		unlock_page(entry);
> -		put_page(entry);
> -	} else {
> -		dax_unlock_mapping_entry(mapping, index);
> -	}
> -}
> -
> -/*
> - * Called when we are done with radix tree entry we looked up via
> - * get_unlocked_mapping_entry() and which we didn't lock in the end.
> - */
> -static void put_unlocked_mapping_entry(struct address_space *mapping,
> -				       pgoff_t index, void *entry)
> -{
> -	if (!radix_tree_exceptional_entry(entry))
> -		return;
> -
> -	/* We have to wake up next waiter for the radix tree entry lock */
> -	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
> -}
> -
>  /*
>   * Delete exceptional DAX entry at @index from @mapping. Wait for radix tree
>   * entry to get unlocked before deleting it.
> -- 
> 2.9.0
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 15/17] dax: add struct iomap based DAX PMD support
  2016-10-12 22:50   ` Ross Zwisler
                       ` (2 preceding siblings ...)
  (?)
@ 2016-10-13 15:42     ` Jan Kara
  -1 siblings, 0 replies; 126+ messages in thread
From: Jan Kara @ 2016-10-13 15:42 UTC (permalink / raw)
  To: Ross Zwisler
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner, linux-nvdimm,
	linux-kernel, linux-xfs, linux-mm, Andreas Dilger,
	Alexander Viro, linux-fsdevel, Jan Kara, Andrew Morton,
	linux-ext4, Christoph Hellwig

On Wed 12-10-16 16:50:20, Ross Zwisler wrote:
> DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
> locking.  This patch allows DAX PMDs to participate in the DAX radix tree
> based locking scheme so that they can be re-enabled using the new struct
> iomap based fault handlers.
> 
> There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
> mappings that have an associated block allocation, and 4k DAX empty
> entries.  The empty entries exist to provide locking for the duration of a
> given page fault.
> 
> This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
> entries, PMD DAX entries that have associated block allocations, and 2 MiB
> DAX empty entries.
> 
> Unlike the 4k case where we insert a struct page* into the radix tree for
> 4k zero pages, for HZP we insert a DAX exceptional entry with the new
> RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
> every 2MiB hole mapping, and it doesn't make sense to have that same struct
> page* with multiple entries in multiple trees.  This would cause contention
> on the single page lock for the one Huge Zero Page, and it would break the
> page->index and page->mapping associations that are assumed to be valid in
> many other places in the kernel.
> 
> One difficult use case is when one thread is trying to use 4k entries in
> radix tree for a given offset, and another thread is using 2 MiB entries
> for that same offset.  The current code handles this by making the 2 MiB
> user fall back to 4k entries for most cases.  This was done because it is
> the simplest solution, and because the use of 2MiB pages is already
> opportunistic.
> 
> If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
> we run into the problem of how we lock out 4k page faults for the entire
> 2MiB range while we clean out the radix tree so we can insert the 2MiB
> entry.  We can solve this problem if we need to, but I think that the cases
> where both 2MiB entries and 4K entries are being used for the same range
> will be rare enough and the gain small enough that it probably won't be
> worth the complexity.
> 
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>

Just one small bug below. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

after fixing that.

>  	/* No entry for given index? Make sure radix tree is big enough. */
> -	if (!entry) {
> +	if (!entry || pmd_downgrade) {
>  		int err;
>  
> +		if (pmd_downgrade) {
> +			/*
> +			 * Make sure 'entry' remains valid while we drop
> +			 * mapping->tree_lock.
> +			 */
> +			entry = lock_slot(mapping, slot);
> +		}
> +
>  		spin_unlock_irq(&mapping->tree_lock);
>  		err = radix_tree_preload(
>  				mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
> -		if (err)
> +		if (err) {
> +			put_locked_mapping_entry(mapping, index, entry);

Better do this only in pmd_downgrade case...

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR
_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 15/17] dax: add struct iomap based DAX PMD support
@ 2016-10-13 15:42     ` Jan Kara
  0 siblings, 0 replies; 126+ messages in thread
From: Jan Kara @ 2016-10-13 15:42 UTC (permalink / raw)
  To: Ross Zwisler
  Cc: linux-kernel, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

On Wed 12-10-16 16:50:20, Ross Zwisler wrote:
> DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
> locking.  This patch allows DAX PMDs to participate in the DAX radix tree
> based locking scheme so that they can be re-enabled using the new struct
> iomap based fault handlers.
> 
> There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
> mappings that have an associated block allocation, and 4k DAX empty
> entries.  The empty entries exist to provide locking for the duration of a
> given page fault.
> 
> This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
> entries, PMD DAX entries that have associated block allocations, and 2 MiB
> DAX empty entries.
> 
> Unlike the 4k case where we insert a struct page* into the radix tree for
> 4k zero pages, for HZP we insert a DAX exceptional entry with the new
> RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
> every 2MiB hole mapping, and it doesn't make sense to have that same struct
> page* with multiple entries in multiple trees.  This would cause contention
> on the single page lock for the one Huge Zero Page, and it would break the
> page->index and page->mapping associations that are assumed to be valid in
> many other places in the kernel.
> 
> One difficult use case is when one thread is trying to use 4k entries in
> radix tree for a given offset, and another thread is using 2 MiB entries
> for that same offset.  The current code handles this by making the 2 MiB
> user fall back to 4k entries for most cases.  This was done because it is
> the simplest solution, and because the use of 2MiB pages is already
> opportunistic.
> 
> If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
> we run into the problem of how we lock out 4k page faults for the entire
> 2MiB range while we clean out the radix tree so we can insert the 2MiB
> entry.  We can solve this problem if we need to, but I think that the cases
> where both 2MiB entries and 4K entries are being used for the same range
> will be rare enough and the gain small enough that it probably won't be
> worth the complexity.
> 
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>

Just one small bug below. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

after fixing that.

>  	/* No entry for given index? Make sure radix tree is big enough. */
> -	if (!entry) {
> +	if (!entry || pmd_downgrade) {
>  		int err;
>  
> +		if (pmd_downgrade) {
> +			/*
> +			 * Make sure 'entry' remains valid while we drop
> +			 * mapping->tree_lock.
> +			 */
> +			entry = lock_slot(mapping, slot);
> +		}
> +
>  		spin_unlock_irq(&mapping->tree_lock);
>  		err = radix_tree_preload(
>  				mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
> -		if (err)
> +		if (err) {
> +			put_locked_mapping_entry(mapping, index, entry);

Better do this only in pmd_downgrade case...

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 15/17] dax: add struct iomap based DAX PMD support
@ 2016-10-13 15:42     ` Jan Kara
  0 siblings, 0 replies; 126+ messages in thread
From: Jan Kara @ 2016-10-13 15:42 UTC (permalink / raw)
  To: Ross Zwisler
  Cc: linux-kernel, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

On Wed 12-10-16 16:50:20, Ross Zwisler wrote:
> DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
> locking.  This patch allows DAX PMDs to participate in the DAX radix tree
> based locking scheme so that they can be re-enabled using the new struct
> iomap based fault handlers.
> 
> There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
> mappings that have an associated block allocation, and 4k DAX empty
> entries.  The empty entries exist to provide locking for the duration of a
> given page fault.
> 
> This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
> entries, PMD DAX entries that have associated block allocations, and 2 MiB
> DAX empty entries.
> 
> Unlike the 4k case where we insert a struct page* into the radix tree for
> 4k zero pages, for HZP we insert a DAX exceptional entry with the new
> RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
> every 2MiB hole mapping, and it doesn't make sense to have that same struct
> page* with multiple entries in multiple trees.  This would cause contention
> on the single page lock for the one Huge Zero Page, and it would break the
> page->index and page->mapping associations that are assumed to be valid in
> many other places in the kernel.
> 
> One difficult use case is when one thread is trying to use 4k entries in
> radix tree for a given offset, and another thread is using 2 MiB entries
> for that same offset.  The current code handles this by making the 2 MiB
> user fall back to 4k entries for most cases.  This was done because it is
> the simplest solution, and because the use of 2MiB pages is already
> opportunistic.
> 
> If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
> we run into the problem of how we lock out 4k page faults for the entire
> 2MiB range while we clean out the radix tree so we can insert the 2MiB
> entry.  We can solve this problem if we need to, but I think that the cases
> where both 2MiB entries and 4K entries are being used for the same range
> will be rare enough and the gain small enough that it probably won't be
> worth the complexity.
> 
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>

Just one small bug below. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

after fixing that.

>  	/* No entry for given index? Make sure radix tree is big enough. */
> -	if (!entry) {
> +	if (!entry || pmd_downgrade) {
>  		int err;
>  
> +		if (pmd_downgrade) {
> +			/*
> +			 * Make sure 'entry' remains valid while we drop
> +			 * mapping->tree_lock.
> +			 */
> +			entry = lock_slot(mapping, slot);
> +		}
> +
>  		spin_unlock_irq(&mapping->tree_lock);
>  		err = radix_tree_preload(
>  				mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
> -		if (err)
> +		if (err) {
> +			put_locked_mapping_entry(mapping, index, entry);

Better do this only in pmd_downgrade case...

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 15/17] dax: add struct iomap based DAX PMD support
@ 2016-10-13 15:42     ` Jan Kara
  0 siblings, 0 replies; 126+ messages in thread
From: Jan Kara @ 2016-10-13 15:42 UTC (permalink / raw)
  To: Ross Zwisler
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner,
	linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA,
	linux-xfs-u79uwXL29TY76Z2rM5mHXA,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg, Andreas Dilger, Alexander Viro,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA, Jan Kara, Andrew Morton,
	linux-ext4-u79uwXL29TY76Z2rM5mHXA, Christoph Hellwig

On Wed 12-10-16 16:50:20, Ross Zwisler wrote:
> DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
> locking.  This patch allows DAX PMDs to participate in the DAX radix tree
> based locking scheme so that they can be re-enabled using the new struct
> iomap based fault handlers.
> 
> There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
> mappings that have an associated block allocation, and 4k DAX empty
> entries.  The empty entries exist to provide locking for the duration of a
> given page fault.
> 
> This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
> entries, PMD DAX entries that have associated block allocations, and 2 MiB
> DAX empty entries.
> 
> Unlike the 4k case where we insert a struct page* into the radix tree for
> 4k zero pages, for HZP we insert a DAX exceptional entry with the new
> RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
> every 2MiB hole mapping, and it doesn't make sense to have that same struct
> page* with multiple entries in multiple trees.  This would cause contention
> on the single page lock for the one Huge Zero Page, and it would break the
> page->index and page->mapping associations that are assumed to be valid in
> many other places in the kernel.
> 
> One difficult use case is when one thread is trying to use 4k entries in
> radix tree for a given offset, and another thread is using 2 MiB entries
> for that same offset.  The current code handles this by making the 2 MiB
> user fall back to 4k entries for most cases.  This was done because it is
> the simplest solution, and because the use of 2MiB pages is already
> opportunistic.
> 
> If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
> we run into the problem of how we lock out 4k page faults for the entire
> 2MiB range while we clean out the radix tree so we can insert the 2MiB
> entry.  We can solve this problem if we need to, but I think that the cases
> where both 2MiB entries and 4K entries are being used for the same range
> will be rare enough and the gain small enough that it probably won't be
> worth the complexity.
> 
> Signed-off-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>

Just one small bug below. Feel free to add:

Reviewed-by: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>

after fixing that.

>  	/* No entry for given index? Make sure radix tree is big enough. */
> -	if (!entry) {
> +	if (!entry || pmd_downgrade) {
>  		int err;
>  
> +		if (pmd_downgrade) {
> +			/*
> +			 * Make sure 'entry' remains valid while we drop
> +			 * mapping->tree_lock.
> +			 */
> +			entry = lock_slot(mapping, slot);
> +		}
> +
>  		spin_unlock_irq(&mapping->tree_lock);
>  		err = radix_tree_preload(
>  				mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
> -		if (err)
> +		if (err) {
> +			put_locked_mapping_entry(mapping, index, entry);

Better do this only in pmd_downgrade case...

								Honza
-- 
Jan Kara <jack-IBi9RG/b67k@public.gmane.org>
SUSE Labs, CR

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 15/17] dax: add struct iomap based DAX PMD support
@ 2016-10-13 15:42     ` Jan Kara
  0 siblings, 0 replies; 126+ messages in thread
From: Jan Kara @ 2016-10-13 15:42 UTC (permalink / raw)
  To: Ross Zwisler
  Cc: linux-kernel, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

On Wed 12-10-16 16:50:20, Ross Zwisler wrote:
> DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
> locking.  This patch allows DAX PMDs to participate in the DAX radix tree
> based locking scheme so that they can be re-enabled using the new struct
> iomap based fault handlers.
> 
> There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
> mappings that have an associated block allocation, and 4k DAX empty
> entries.  The empty entries exist to provide locking for the duration of a
> given page fault.
> 
> This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
> entries, PMD DAX entries that have associated block allocations, and 2 MiB
> DAX empty entries.
> 
> Unlike the 4k case where we insert a struct page* into the radix tree for
> 4k zero pages, for HZP we insert a DAX exceptional entry with the new
> RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
> every 2MiB hole mapping, and it doesn't make sense to have that same struct
> page* with multiple entries in multiple trees.  This would cause contention
> on the single page lock for the one Huge Zero Page, and it would break the
> page->index and page->mapping associations that are assumed to be valid in
> many other places in the kernel.
> 
> One difficult use case is when one thread is trying to use 4k entries in
> radix tree for a given offset, and another thread is using 2 MiB entries
> for that same offset.  The current code handles this by making the 2 MiB
> user fall back to 4k entries for most cases.  This was done because it is
> the simplest solution, and because the use of 2MiB pages is already
> opportunistic.
> 
> If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
> we run into the problem of how we lock out 4k page faults for the entire
> 2MiB range while we clean out the radix tree so we can insert the 2MiB
> entry.  We can solve this problem if we need to, but I think that the cases
> where both 2MiB entries and 4K entries are being used for the same range
> will be rare enough and the gain small enough that it probably won't be
> worth the complexity.
> 
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>

Just one small bug below. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

after fixing that.

>  	/* No entry for given index? Make sure radix tree is big enough. */
> -	if (!entry) {
> +	if (!entry || pmd_downgrade) {
>  		int err;
>  
> +		if (pmd_downgrade) {
> +			/*
> +			 * Make sure 'entry' remains valid while we drop
> +			 * mapping->tree_lock.
> +			 */
> +			entry = lock_slot(mapping, slot);
> +		}
> +
>  		spin_unlock_irq(&mapping->tree_lock);
>  		err = radix_tree_preload(
>  				mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
> -		if (err)
> +		if (err) {
> +			put_locked_mapping_entry(mapping, index, entry);

Better do this only in pmd_downgrade case...

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD
  2016-10-12 22:50   ` Ross Zwisler
  (?)
  (?)
@ 2016-10-13 15:42     ` Jan Kara
  -1 siblings, 0 replies; 126+ messages in thread
From: Jan Kara @ 2016-10-13 15:42 UTC (permalink / raw)
  To: Ross Zwisler
  Cc: linux-kernel, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

On Wed 12-10-16 16:50:22, Ross Zwisler wrote:
> Now that DAX PMD faults are once again working and are now participating in
> DAX's radix tree locking scheme, allow their config option to be enabled.
> 
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>

Looks good. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/Kconfig | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 2bc7ad7..b6f0fce 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -55,7 +55,6 @@ config FS_DAX_PMD
>  	depends on FS_DAX
>  	depends on ZONE_DEVICE
>  	depends on TRANSPARENT_HUGEPAGE
> -	depends on BROKEN
>  
>  endif # BLOCK
>  
> -- 
> 2.9.0
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD
@ 2016-10-13 15:42     ` Jan Kara
  0 siblings, 0 replies; 126+ messages in thread
From: Jan Kara @ 2016-10-13 15:42 UTC (permalink / raw)
  To: Ross Zwisler
  Cc: linux-kernel, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

On Wed 12-10-16 16:50:22, Ross Zwisler wrote:
> Now that DAX PMD faults are once again working and are now participating in
> DAX's radix tree locking scheme, allow their config option to be enabled.
> 
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>

Looks good. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/Kconfig | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 2bc7ad7..b6f0fce 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -55,7 +55,6 @@ config FS_DAX_PMD
>  	depends on FS_DAX
>  	depends on ZONE_DEVICE
>  	depends on TRANSPARENT_HUGEPAGE
> -	depends on BROKEN
>  
>  endif # BLOCK
>  
> -- 
> 2.9.0
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD
@ 2016-10-13 15:42     ` Jan Kara
  0 siblings, 0 replies; 126+ messages in thread
From: Jan Kara @ 2016-10-13 15:42 UTC (permalink / raw)
  To: Ross Zwisler
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner,
	linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA,
	linux-xfs-u79uwXL29TY76Z2rM5mHXA,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg, Andreas Dilger, Alexander Viro,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA, Jan Kara, Andrew Morton,
	linux-ext4-u79uwXL29TY76Z2rM5mHXA, Christoph Hellwig

On Wed 12-10-16 16:50:22, Ross Zwisler wrote:
> Now that DAX PMD faults are once again working and are now participating in
> DAX's radix tree locking scheme, allow their config option to be enabled.
> 
> Signed-off-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>

Looks good. You can add:

Reviewed-by: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>

								Honza

> ---
>  fs/Kconfig | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 2bc7ad7..b6f0fce 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -55,7 +55,6 @@ config FS_DAX_PMD
>  	depends on FS_DAX
>  	depends on ZONE_DEVICE
>  	depends on TRANSPARENT_HUGEPAGE
> -	depends on BROKEN
>  
>  endif # BLOCK
>  
> -- 
> 2.9.0
> 
-- 
Jan Kara <jack-IBi9RG/b67k@public.gmane.org>
SUSE Labs, CR

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD
@ 2016-10-13 15:42     ` Jan Kara
  0 siblings, 0 replies; 126+ messages in thread
From: Jan Kara @ 2016-10-13 15:42 UTC (permalink / raw)
  To: Ross Zwisler
  Cc: linux-kernel, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

On Wed 12-10-16 16:50:22, Ross Zwisler wrote:
> Now that DAX PMD faults are once again working and are now participating in
> DAX's radix tree locking scheme, allow their config option to be enabled.
> 
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>

Looks good. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/Kconfig | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 2bc7ad7..b6f0fce 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -55,7 +55,6 @@ config FS_DAX_PMD
>  	depends on FS_DAX
>  	depends on ZONE_DEVICE
>  	depends on TRANSPARENT_HUGEPAGE
> -	depends on BROKEN
>  
>  endif # BLOCK
>  
> -- 
> 2.9.0
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

^ permalink raw reply	[flat|nested] 126+ messages in thread
* [PATCH v7 15/17] dax: add struct iomap based DAX PMD support
  2016-10-13 15:42     ` Jan Kara
  (?)
  (?)
@ 2016-10-13 19:23       ` Ross Zwisler
  -1 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-13 19:23 UTC (permalink / raw)
  To: linux-kernel
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner, linux-nvdimm,
	Christoph Hellwig, linux-xfs, linux-mm, Andreas Dilger,
	Alexander Viro, linux-fsdevel, Jan Kara, linux-ext4,
	Andrew Morton

DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
locking.  This patch allows DAX PMDs to participate in the DAX radix tree
based locking scheme so that they can be re-enabled using the new struct
iomap based fault handlers.

There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
mappings that have an associated block allocation, and 4k DAX empty
entries.  The empty entries exist to provide locking for the duration of a
given page fault.

This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
entries, PMD DAX entries that have associated block allocations, and 2 MiB
DAX empty entries.

Unlike the 4k case where we insert a struct page* into the radix tree for
4k zero pages, for HZP we insert a DAX exceptional entry with the new
RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
every 2MiB hole mapping, and it doesn't make sense to have that same struct
page* with multiple entries in multiple trees.  This would cause contention
on the single page lock for the one Huge Zero Page, and it would break the
page->index and page->mapping associations that are assumed to be valid in
many other places in the kernel.

One difficult use case is when one thread is trying to use 4k entries in
radix tree for a given offset, and another thread is using 2 MiB entries
for that same offset.  The current code handles this by making the 2 MiB
user fall back to 4k entries for most cases.  This was done because it is
the simplest solution, and because the use of 2MiB pages is already
opportunistic.

If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
we run into the problem of how we lock out 4k page faults for the entire
2MiB range while we clean out the radix tree so we can insert the 2MiB
entry.  We can solve this problem if we need to, but I think that the cases
where both 2MiB entries and 4K entries are being used for the same range
will be rare enough and the gain small enough that it probably won't be
worth the complexity.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c            | 378 +++++++++++++++++++++++++++++++++++++++++++++++-----
 include/linux/dax.h |  55 ++++++--
 mm/filemap.c        |   3 +-
 3 files changed, 386 insertions(+), 50 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 0582c7c..153cfd5 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -76,6 +76,26 @@ static void dax_unmap_atomic(struct block_device *bdev,
 	blk_queue_exit(bdev->bd_queue);
 }
 
+static int dax_is_pmd_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_PMD;
+}
+
+static int dax_is_pte_entry(void *entry)
+{
+	return !((unsigned long)entry & RADIX_DAX_PMD);
+}
+
+static int dax_is_zero_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_HZP;
+}
+
+static int dax_is_empty_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_EMPTY;
+}
+
 struct page *read_dax_sector(struct block_device *bdev, sector_t n)
 {
 	struct page *page = alloc_pages(GFP_KERNEL, 0);
@@ -281,7 +301,7 @@ static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
 	 * queue to the start of that PMD.  This ensures that all offsets in
 	 * the range covered by the PMD map to the same bit lock.
 	 */
-	if (RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
+	if (dax_is_pmd_entry(entry))
 		index &= ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1);
 
 	key->mapping = mapping;
@@ -413,36 +433,116 @@ static void put_unlocked_mapping_entry(struct address_space *mapping,
  * radix tree entry locked. If the radix tree doesn't contain given index,
  * create empty exceptional entry for the index and return with it locked.
  *
+ * When requesting an entry with size RADIX_DAX_PMD, grab_mapping_entry() will
+ * either return that locked entry or will return an error.  This error will
+ * happen if there are any 4k entries (either zero pages or DAX entries)
+ * within the 2MiB range that we are requesting.
+ *
+ * We always favor 4k entries over 2MiB entries. There isn't a flow where we
+ * evict 4k entries in order to 'upgrade' them to a 2MiB entry.  A 2MiB
+ * insertion will fail if it finds any 4k entries already in the tree, and a
+ * 4k insertion will cause an existing 2MiB entry to be unmapped and
+ * downgraded to 4k entries.  This happens for both 2MiB huge zero pages as
+ * well as 2MiB empty entries.
+ *
+ * The exception to this downgrade path is for 2MiB DAX PMD entries that have
+ * real storage backing them.  We will leave these real 2MiB DAX entries in
+ * the tree, and PTE writes will simply dirty the entire 2MiB DAX entry.
+ *
  * Note: Unlike filemap_fault() we don't honor FAULT_FLAG_RETRY flags. For
  * persistent memory the benefit is doubtful. We can add that later if we can
  * show it helps.
  */
-static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index)
+static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
+		unsigned long size_flag)
 {
+	bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */
 	void *entry, **slot;
 
 restart:
 	spin_lock_irq(&mapping->tree_lock);
 	entry = get_unlocked_mapping_entry(mapping, index, &slot);
+
+	if (entry) {
+		if (size_flag & RADIX_DAX_PMD) {
+			if (!radix_tree_exceptional_entry(entry) ||
+			    dax_is_pte_entry(entry)) {
+				put_unlocked_mapping_entry(mapping, index,
+						entry);
+				entry = ERR_PTR(-EEXIST);
+				goto out_unlock;
+			}
+		} else { /* trying to grab a PTE entry */
+			if (radix_tree_exceptional_entry(entry) &&
+			    dax_is_pmd_entry(entry) &&
+			    (dax_is_zero_entry(entry) ||
+			     dax_is_empty_entry(entry))) {
+				pmd_downgrade = true;
+			}
+		}
+	}
+
 	/* No entry for given index? Make sure radix tree is big enough. */
-	if (!entry) {
+	if (!entry || pmd_downgrade) {
 		int err;
 
+		if (pmd_downgrade) {
+			/*
+			 * Make sure 'entry' remains valid while we drop
+			 * mapping->tree_lock.
+			 */
+			entry = lock_slot(mapping, slot);
+		}
+
 		spin_unlock_irq(&mapping->tree_lock);
 		err = radix_tree_preload(
 				mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
-		if (err)
+		if (err) {
+			if (pmd_downgrade)
+				put_locked_mapping_entry(mapping, index, entry);
 			return ERR_PTR(err);
-		entry = (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
-			       RADIX_DAX_ENTRY_LOCK);
+		}
+
+		/*
+		 * Besides huge zero pages the only other thing that gets
+		 * downgraded are empty entries which don't need to be
+		 * unmapped.
+		 */
+		if (pmd_downgrade && dax_is_zero_entry(entry))
+			unmap_mapping_range(mapping,
+				(index << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
+
 		spin_lock_irq(&mapping->tree_lock);
-		err = radix_tree_insert(&mapping->page_tree, index, entry);
+
+		if (pmd_downgrade) {
+			radix_tree_delete(&mapping->page_tree, index);
+			mapping->nrexceptional--;
+			dax_wake_mapping_entry_waiter(mapping, index, entry,
+					true);
+		}
+
+		entry = dax_radix_locked_entry(0, size_flag | RADIX_DAX_EMPTY);
+
+		err = __radix_tree_insert(&mapping->page_tree, index,
+				dax_radix_order(entry), entry);
 		radix_tree_preload_end();
 		if (err) {
 			spin_unlock_irq(&mapping->tree_lock);
-			/* Someone already created the entry? */
-			if (err == -EEXIST)
+			/*
+			 * Someone already created the entry?  This is a
+			 * normal failure when inserting PMDs in a range
+			 * that already contains PTEs.  In that case we want
+			 * to return -EEXIST immediately.
+			 */
+			if (err == -EEXIST && !(size_flag & RADIX_DAX_PMD))
 				goto restart;
+			/*
+			 * Our insertion of a DAX PMD entry failed, most
+			 * likely because it collided with a PTE sized entry
+			 * at a different index in the PMD range.  We haven't
+			 * inserted anything into the radix tree and have no
+			 * waiters to wake.
+			 */
 			return ERR_PTR(err);
 		}
 		/* Good, we have inserted empty locked entry into the tree. */
@@ -466,6 +566,7 @@ restart:
 		return page;
 	}
 	entry = lock_slot(mapping, slot);
+ out_unlock:
 	spin_unlock_irq(&mapping->tree_lock);
 	return entry;
 }
@@ -473,9 +574,9 @@ restart:
 /*
  * We do not necessarily hold the mapping->tree_lock when we call this
  * function so it is possible that 'entry' is no longer a valid item in the
- * radix tree.  This is okay, though, because all we really need to do is to
- * find the correct waitqueue where tasks might be sleeping waiting for that
- * old 'entry' and wake them.
+ * radix tree.  This is okay because all we really need to do is to find the
+ * correct waitqueue where tasks might be waiting for that old 'entry' and
+ * wake them.
  */
 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 		pgoff_t index, void *entry, bool wake_all)
@@ -588,11 +689,17 @@ static int copy_user_dax(struct block_device *bdev, sector_t sector, size_t size
 	return 0;
 }
 
-#define DAX_PMD_INDEX(page_index) (page_index & (PMD_MASK >> PAGE_SHIFT))
-
+/*
+ * By this point grab_mapping_entry() has ensured that we have a locked entry
+ * of the appropriate size so we don't have to worry about downgrading PMDs to
+ * PTEs.  If we happen to be trying to insert a PTE and there is a PMD
+ * already in the tree, we will skip the insertion and just dirty the PMD as
+ * appropriate.
+ */
 static void *dax_insert_mapping_entry(struct address_space *mapping,
 				      struct vm_fault *vmf,
-				      void *entry, sector_t sector)
+				      void *entry, sector_t sector,
+				      unsigned long flags)
 {
 	struct radix_tree_root *page_tree = &mapping->page_tree;
 	int error = 0;
@@ -615,22 +722,35 @@ static void *dax_insert_mapping_entry(struct address_space *mapping,
 		error = radix_tree_preload(vmf->gfp_mask & ~__GFP_HIGHMEM);
 		if (error)
 			return ERR_PTR(error);
+	} else if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_HZP)) {
+		/* replacing huge zero page with PMD block mapping */
+		unmap_mapping_range(mapping,
+			(vmf->pgoff << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
 	}
 
 	spin_lock_irq(&mapping->tree_lock);
-	new_entry = (void *)((unsigned long)RADIX_DAX_ENTRY(sector, false) |
-		       RADIX_DAX_ENTRY_LOCK);
+	new_entry = dax_radix_locked_entry(sector, flags);
+
 	if (hole_fill) {
 		__delete_from_page_cache(entry, NULL);
 		/* Drop pagecache reference */
 		put_page(entry);
-		error = radix_tree_insert(page_tree, index, new_entry);
+		error = __radix_tree_insert(page_tree, index,
+				dax_radix_order(new_entry), new_entry);
 		if (error) {
 			new_entry = ERR_PTR(error);
 			goto unlock;
 		}
 		mapping->nrexceptional++;
-	} else {
+	} else if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
+		/*
+		 * Only swap our new entry into the radix tree if the current
+		 * entry is a zero page or an empty entry.  If a normal PTE or
+		 * PMD entry is already in the tree, we leave it alone.  This
+		 * means that if we are trying to insert a PTE and the
+		 * existing entry is a PMD, we will just leave the PMD in the
+		 * tree and dirty it if necessary.
+		 */
 		void **slot;
 		void *ret;
 
@@ -660,7 +780,6 @@ static int dax_writeback_one(struct block_device *bdev,
 		struct address_space *mapping, pgoff_t index, void *entry)
 {
 	struct radix_tree_root *page_tree = &mapping->page_tree;
-	int type = RADIX_DAX_TYPE(entry);
 	struct radix_tree_node *node;
 	struct blk_dax_ctl dax;
 	void **slot;
@@ -681,13 +800,21 @@ static int dax_writeback_one(struct block_device *bdev,
 	if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
 		goto unlock;
 
-	if (WARN_ON_ONCE(type != RADIX_DAX_PTE && type != RADIX_DAX_PMD)) {
+	if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
+				dax_is_zero_entry(entry))) {
 		ret = -EIO;
 		goto unlock;
 	}
 
-	dax.sector = RADIX_DAX_SECTOR(entry);
-	dax.size = (type == RADIX_DAX_PMD ? PMD_SIZE : PAGE_SIZE);
+	/*
+	 * Even if dax_writeback_mapping_range() was given a wbc->range_start
+	 * in the middle of a PMD, the 'index' we are given will be aligned to
+	 * the start index of the PMD, as will the sector we pull from
+	 * 'entry'.  This allows us to flush for PMD_SIZE and not have to
+	 * worry about partial PMD writebacks.
+	 */
+	dax.sector = dax_radix_sector(entry);
+	dax.size = PAGE_SIZE << dax_radix_order(entry);
 	spin_unlock_irq(&mapping->tree_lock);
 
 	/*
@@ -726,12 +853,11 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 		struct block_device *bdev, struct writeback_control *wbc)
 {
 	struct inode *inode = mapping->host;
-	pgoff_t start_index, end_index, pmd_index;
+	pgoff_t start_index, end_index;
 	pgoff_t indices[PAGEVEC_SIZE];
 	struct pagevec pvec;
 	bool done = false;
 	int i, ret = 0;
-	void *entry;
 
 	if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
 		return -EIO;
@@ -741,15 +867,6 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 
 	start_index = wbc->range_start >> PAGE_SHIFT;
 	end_index = wbc->range_end >> PAGE_SHIFT;
-	pmd_index = DAX_PMD_INDEX(start_index);
-
-	rcu_read_lock();
-	entry = radix_tree_lookup(&mapping->page_tree, pmd_index);
-	rcu_read_unlock();
-
-	/* see if the start of our range is covered by a PMD entry */
-	if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
-		start_index = pmd_index;
 
 	tag_pages_for_writeback(mapping, start_index, end_index);
 
@@ -794,7 +911,7 @@ static int dax_insert_mapping(struct address_space *mapping,
 		return PTR_ERR(dax.addr);
 	dax_unmap_atomic(bdev, &dax);
 
-	ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector);
+	ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector, 0);
 	if (IS_ERR(ret))
 		return PTR_ERR(ret);
 	*entryp = ret;
@@ -841,7 +958,7 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	bh.b_bdev = inode->i_sb->s_bdev;
 	bh.b_size = PAGE_SIZE;
 
-	entry = grab_mapping_entry(mapping, vmf->pgoff);
+	entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
 	if (IS_ERR(entry)) {
 		error = PTR_ERR(entry);
 		goto out;
@@ -1162,7 +1279,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	if (pos >= i_size_read(inode))
 		return VM_FAULT_SIGBUS;
 
-	entry = grab_mapping_entry(mapping, vmf->pgoff);
+	entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
 	if (IS_ERR(entry)) {
 		error = PTR_ERR(entry);
 		goto out;
@@ -1264,4 +1381,191 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	return VM_FAULT_NOPAGE | major;
 }
 EXPORT_SYMBOL_GPL(dax_iomap_fault);
+
+#ifdef CONFIG_FS_DAX_PMD
+/*
+ * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
+ * more often than one might expect in the below functions.
+ */
+#define PG_PMD_COLOUR	((PMD_SIZE >> PAGE_SHIFT) - 1)
+
+static int dax_pmd_insert_mapping(struct vm_area_struct *vma, pmd_t *pmd,
+		struct vm_fault *vmf, unsigned long address,
+		struct iomap *iomap, loff_t pos, bool write, void **entryp)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	struct block_device *bdev = iomap->bdev;
+	struct blk_dax_ctl dax = {
+		.sector = dax_iomap_sector(iomap, pos),
+		.size = PMD_SIZE,
+	};
+	long length = dax_map_atomic(bdev, &dax);
+	void *ret;
+
+	if (length < 0) /* dax_map_atomic() failed */
+		return VM_FAULT_FALLBACK;
+	if (length < PMD_SIZE)
+		goto unmap_fallback;
+	if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR)
+		goto unmap_fallback;
+	if (!pfn_t_devmap(dax.pfn))
+		goto unmap_fallback;
+
+	dax_unmap_atomic(bdev, &dax);
+
+	ret = dax_insert_mapping_entry(mapping, vmf, *entryp, dax.sector,
+			RADIX_DAX_PMD);
+	if (IS_ERR(ret))
+		return VM_FAULT_FALLBACK;
+	*entryp = ret;
+
+	return vmf_insert_pfn_pmd(vma, address, pmd, dax.pfn, write);
+
+ unmap_fallback:
+	dax_unmap_atomic(bdev, &dax);
+	return VM_FAULT_FALLBACK;
+}
+
+static int dax_pmd_load_hole(struct vm_area_struct *vma, pmd_t *pmd,
+		struct vm_fault *vmf, unsigned long address,
+		struct iomap *iomap, void **entryp)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	unsigned long pmd_addr = address & PMD_MASK;
+	struct page *zero_page;
+	spinlock_t *ptl;
+	pmd_t pmd_entry;
+	void *ret;
+
+	zero_page = get_huge_zero_page();
+
+	if (unlikely(!zero_page))
+		return VM_FAULT_FALLBACK;
+
+	ret = dax_insert_mapping_entry(mapping, vmf, *entryp, 0,
+			RADIX_DAX_PMD | RADIX_DAX_HZP);
+	if (IS_ERR(ret))
+		return VM_FAULT_FALLBACK;
+	*entryp = ret;
+
+	ptl = pmd_lock(vma->vm_mm, pmd);
+	if (!pmd_none(*pmd)) {
+		spin_unlock(ptl);
+		return VM_FAULT_FALLBACK;
+	}
+
+	pmd_entry = mk_pmd(zero_page, vma->vm_page_prot);
+	pmd_entry = pmd_mkhuge(pmd_entry);
+	set_pmd_at(vma->vm_mm, pmd_addr, pmd, pmd_entry);
+	spin_unlock(ptl);
+	return VM_FAULT_NOPAGE;
+}
+
+int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
+		pmd_t *pmd, unsigned int flags, struct iomap_ops *ops)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	unsigned long pmd_addr = address & PMD_MASK;
+	bool write = flags & FAULT_FLAG_WRITE;
+	unsigned int iomap_flags = write ? IOMAP_WRITE : 0;
+	struct inode *inode = mapping->host;
+	int result = VM_FAULT_FALLBACK;
+	struct iomap iomap = { 0 };
+	pgoff_t max_pgoff, pgoff;
+	struct vm_fault vmf;
+	void *entry;
+	loff_t pos;
+	int error;
+
+	/* Fall back to PTEs if we're going to COW */
+	if (write && !(vma->vm_flags & VM_SHARED)) {
+		split_huge_pmd(vma, pmd, address);
+		goto fallback;
+	}
+
+	/* If the PMD would extend outside the VMA */
+	if (pmd_addr < vma->vm_start)
+		goto fallback;
+	if ((pmd_addr + PMD_SIZE) > vma->vm_end)
+		goto fallback;
+
+	/*
+	 * Check whether offset isn't beyond end of file now. Caller is
+	 * supposed to hold locks serializing us with truncate / punch hole so
+	 * this is a reliable test.
+	 */
+	pgoff = linear_page_index(vma, pmd_addr);
+	max_pgoff = (i_size_read(inode) - 1) >> PAGE_SHIFT;
+
+	if (pgoff > max_pgoff)
+		return VM_FAULT_SIGBUS;
+
+	/* If the PMD would extend beyond the file size */
+	if ((pgoff | PG_PMD_COLOUR) > max_pgoff)
+		goto fallback;
+
+	/*
+	 * grab_mapping_entry() will make sure we get a 2M empty entry, a DAX
+	 * PMD or a HZP entry.  If it can't (because a 4k page is already in
+	 * the tree, for instance), it will return -EEXIST and we just fall
+	 * back to 4k entries.
+	 */
+	entry = grab_mapping_entry(mapping, pgoff, RADIX_DAX_PMD);
+	if (IS_ERR(entry))
+		goto fallback;
+
+	/*
+	 * Note that we don't use iomap_apply here.  We aren't doing I/O, only
+	 * setting up a mapping, so really we're using iomap_begin() as a way
+	 * to look up our filesystem block.
+	 */
+	pos = (loff_t)pgoff << PAGE_SHIFT;
+	error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap);
+	if (error)
+		goto unlock_entry;
+	if (iomap.offset + iomap.length < pos + PMD_SIZE)
+		goto finish_iomap;
+
+	vmf.pgoff = pgoff;
+	vmf.flags = flags;
+	vmf.gfp_mask = mapping_gfp_mask(mapping) | __GFP_IO;
+
+	switch (iomap.type) {
+	case IOMAP_MAPPED:
+		result = dax_pmd_insert_mapping(vma, pmd, &vmf, address,
+				&iomap, pos, write, &entry);
+		break;
+	case IOMAP_UNWRITTEN:
+	case IOMAP_HOLE:
+		if (WARN_ON_ONCE(write))
+			goto finish_iomap;
+		result = dax_pmd_load_hole(vma, pmd, &vmf, address, &iomap,
+				&entry);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		break;
+	}
+
+ finish_iomap:
+	if (ops->iomap_end) {
+		if (result == VM_FAULT_FALLBACK) {
+			ops->iomap_end(inode, pos, PMD_SIZE, 0, iomap_flags,
+					&iomap);
+		} else {
+			error = ops->iomap_end(inode, pos, PMD_SIZE, PMD_SIZE,
+					iomap_flags, &iomap);
+			if (error)
+				result = VM_FAULT_FALLBACK;
+		}
+	}
+ unlock_entry:
+	put_locked_mapping_entry(mapping, pgoff, entry);
+ fallback:
+	if (result == VM_FAULT_FALLBACK)
+		count_vm_event(THP_FAULT_FALLBACK);
+	return result;
+}
+EXPORT_SYMBOL_GPL(dax_iomap_pmd_fault);
+#endif /* CONFIG_FS_DAX_PMD */
 #endif /* CONFIG_FS_IOMAP */
diff --git a/include/linux/dax.h b/include/linux/dax.h
index e9ea78c..8d1a5c4 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -9,20 +9,32 @@
 struct iomap_ops;
 
 /*
- * We use lowest available bit in exceptional entry for locking, other two
- * bits to determine entry type. In total 3 special bits.
+ * We use lowest available bit in exceptional entry for locking, one bit for
+ * the entry size (PMD) and two more to tell us if the entry is a huge zero
+ * page (HZP) or an empty entry that is just used for locking.  In total four
+ * special bits.
+ *
+ * If the PMD bit isn't set the entry has size PAGE_SIZE, and if the HZP and
+ * EMPTY bits aren't set the entry is a normal DAX entry with a filesystem
+ * block allocation.
  */
-#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 3)
+#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 4)
 #define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
-#define RADIX_DAX_PTE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
-#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
-#define RADIX_DAX_TYPE_MASK (RADIX_DAX_PTE | RADIX_DAX_PMD)
-#define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_TYPE_MASK)
-#define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
-#define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
-		RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE) | \
-		RADIX_TREE_EXCEPTIONAL_ENTRY))
+#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
+#define RADIX_DAX_HZP (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
+#define RADIX_DAX_EMPTY (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 3))
 
+static inline unsigned long dax_radix_sector(void *entry)
+{
+	return (unsigned long)entry >> RADIX_DAX_SHIFT;
+}
+
+static inline void *dax_radix_locked_entry(sector_t sector, unsigned long flags)
+{
+	return (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY | flags |
+			((unsigned long)sector << RADIX_DAX_SHIFT) |
+			RADIX_DAX_ENTRY_LOCK);
+}
 
 ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_ops *ops);
@@ -67,6 +79,27 @@ static inline int dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
 	return VM_FAULT_FALLBACK;
 }
 
+#ifdef CONFIG_FS_DAX_PMD
+static inline unsigned int dax_radix_order(void *entry)
+{
+	if ((unsigned long)entry & RADIX_DAX_PMD)
+		return PMD_SHIFT - PAGE_SHIFT;
+	return 0;
+}
+int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
+		pmd_t *pmd, unsigned int flags, struct iomap_ops *ops);
+#else
+static inline unsigned int dax_radix_order(void *entry)
+{
+	return 0;
+}
+static inline int dax_iomap_pmd_fault(struct vm_area_struct *vma,
+		unsigned long address, pmd_t *pmd, unsigned int flags,
+		struct iomap_ops *ops)
+{
+	return VM_FAULT_FALLBACK;
+}
+#endif
 int dax_pfn_mkwrite(struct vm_area_struct *, struct vm_fault *);
 #define dax_mkwrite(vma, vmf, gb)	dax_fault(vma, vmf, gb)
 
diff --git a/mm/filemap.c b/mm/filemap.c
index a596462..592e6e9 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -611,8 +611,7 @@ static int page_cache_tree_insert(struct address_space *mapping,
 		} else {
 			/* DAX can replace empty locked entry with a hole */
 			WARN_ON_ONCE(p !=
-				(void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
-					 RADIX_DAX_ENTRY_LOCK));
+				dax_radix_locked_entry(0, RADIX_DAX_EMPTY));
 			/* DAX accounts exceptional entries as normal pages */
 			if (node)
 				workingset_node_pages_dec(node);
-- 
2.7.4

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^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v7 15/17] dax: add struct iomap based DAX PMD support
@ 2016-10-13 19:23       ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-13 19:23 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
locking.  This patch allows DAX PMDs to participate in the DAX radix tree
based locking scheme so that they can be re-enabled using the new struct
iomap based fault handlers.

There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
mappings that have an associated block allocation, and 4k DAX empty
entries.  The empty entries exist to provide locking for the duration of a
given page fault.

This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
entries, PMD DAX entries that have associated block allocations, and 2 MiB
DAX empty entries.

Unlike the 4k case where we insert a struct page* into the radix tree for
4k zero pages, for HZP we insert a DAX exceptional entry with the new
RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
every 2MiB hole mapping, and it doesn't make sense to have that same struct
page* with multiple entries in multiple trees.  This would cause contention
on the single page lock for the one Huge Zero Page, and it would break the
page->index and page->mapping associations that are assumed to be valid in
many other places in the kernel.

One difficult use case is when one thread is trying to use 4k entries in
radix tree for a given offset, and another thread is using 2 MiB entries
for that same offset.  The current code handles this by making the 2 MiB
user fall back to 4k entries for most cases.  This was done because it is
the simplest solution, and because the use of 2MiB pages is already
opportunistic.

If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
we run into the problem of how we lock out 4k page faults for the entire
2MiB range while we clean out the radix tree so we can insert the 2MiB
entry.  We can solve this problem if we need to, but I think that the cases
where both 2MiB entries and 4K entries are being used for the same range
will be rare enough and the gain small enough that it probably won't be
worth the complexity.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c            | 378 +++++++++++++++++++++++++++++++++++++++++++++++-----
 include/linux/dax.h |  55 ++++++--
 mm/filemap.c        |   3 +-
 3 files changed, 386 insertions(+), 50 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 0582c7c..153cfd5 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -76,6 +76,26 @@ static void dax_unmap_atomic(struct block_device *bdev,
 	blk_queue_exit(bdev->bd_queue);
 }
 
+static int dax_is_pmd_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_PMD;
+}
+
+static int dax_is_pte_entry(void *entry)
+{
+	return !((unsigned long)entry & RADIX_DAX_PMD);
+}
+
+static int dax_is_zero_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_HZP;
+}
+
+static int dax_is_empty_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_EMPTY;
+}
+
 struct page *read_dax_sector(struct block_device *bdev, sector_t n)
 {
 	struct page *page = alloc_pages(GFP_KERNEL, 0);
@@ -281,7 +301,7 @@ static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
 	 * queue to the start of that PMD.  This ensures that all offsets in
 	 * the range covered by the PMD map to the same bit lock.
 	 */
-	if (RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
+	if (dax_is_pmd_entry(entry))
 		index &= ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1);
 
 	key->mapping = mapping;
@@ -413,36 +433,116 @@ static void put_unlocked_mapping_entry(struct address_space *mapping,
  * radix tree entry locked. If the radix tree doesn't contain given index,
  * create empty exceptional entry for the index and return with it locked.
  *
+ * When requesting an entry with size RADIX_DAX_PMD, grab_mapping_entry() will
+ * either return that locked entry or will return an error.  This error will
+ * happen if there are any 4k entries (either zero pages or DAX entries)
+ * within the 2MiB range that we are requesting.
+ *
+ * We always favor 4k entries over 2MiB entries. There isn't a flow where we
+ * evict 4k entries in order to 'upgrade' them to a 2MiB entry.  A 2MiB
+ * insertion will fail if it finds any 4k entries already in the tree, and a
+ * 4k insertion will cause an existing 2MiB entry to be unmapped and
+ * downgraded to 4k entries.  This happens for both 2MiB huge zero pages as
+ * well as 2MiB empty entries.
+ *
+ * The exception to this downgrade path is for 2MiB DAX PMD entries that have
+ * real storage backing them.  We will leave these real 2MiB DAX entries in
+ * the tree, and PTE writes will simply dirty the entire 2MiB DAX entry.
+ *
  * Note: Unlike filemap_fault() we don't honor FAULT_FLAG_RETRY flags. For
  * persistent memory the benefit is doubtful. We can add that later if we can
  * show it helps.
  */
-static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index)
+static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
+		unsigned long size_flag)
 {
+	bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */
 	void *entry, **slot;
 
 restart:
 	spin_lock_irq(&mapping->tree_lock);
 	entry = get_unlocked_mapping_entry(mapping, index, &slot);
+
+	if (entry) {
+		if (size_flag & RADIX_DAX_PMD) {
+			if (!radix_tree_exceptional_entry(entry) ||
+			    dax_is_pte_entry(entry)) {
+				put_unlocked_mapping_entry(mapping, index,
+						entry);
+				entry = ERR_PTR(-EEXIST);
+				goto out_unlock;
+			}
+		} else { /* trying to grab a PTE entry */
+			if (radix_tree_exceptional_entry(entry) &&
+			    dax_is_pmd_entry(entry) &&
+			    (dax_is_zero_entry(entry) ||
+			     dax_is_empty_entry(entry))) {
+				pmd_downgrade = true;
+			}
+		}
+	}
+
 	/* No entry for given index? Make sure radix tree is big enough. */
-	if (!entry) {
+	if (!entry || pmd_downgrade) {
 		int err;
 
+		if (pmd_downgrade) {
+			/*
+			 * Make sure 'entry' remains valid while we drop
+			 * mapping->tree_lock.
+			 */
+			entry = lock_slot(mapping, slot);
+		}
+
 		spin_unlock_irq(&mapping->tree_lock);
 		err = radix_tree_preload(
 				mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
-		if (err)
+		if (err) {
+			if (pmd_downgrade)
+				put_locked_mapping_entry(mapping, index, entry);
 			return ERR_PTR(err);
-		entry = (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
-			       RADIX_DAX_ENTRY_LOCK);
+		}
+
+		/*
+		 * Besides huge zero pages the only other thing that gets
+		 * downgraded are empty entries which don't need to be
+		 * unmapped.
+		 */
+		if (pmd_downgrade && dax_is_zero_entry(entry))
+			unmap_mapping_range(mapping,
+				(index << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
+
 		spin_lock_irq(&mapping->tree_lock);
-		err = radix_tree_insert(&mapping->page_tree, index, entry);
+
+		if (pmd_downgrade) {
+			radix_tree_delete(&mapping->page_tree, index);
+			mapping->nrexceptional--;
+			dax_wake_mapping_entry_waiter(mapping, index, entry,
+					true);
+		}
+
+		entry = dax_radix_locked_entry(0, size_flag | RADIX_DAX_EMPTY);
+
+		err = __radix_tree_insert(&mapping->page_tree, index,
+				dax_radix_order(entry), entry);
 		radix_tree_preload_end();
 		if (err) {
 			spin_unlock_irq(&mapping->tree_lock);
-			/* Someone already created the entry? */
-			if (err == -EEXIST)
+			/*
+			 * Someone already created the entry?  This is a
+			 * normal failure when inserting PMDs in a range
+			 * that already contains PTEs.  In that case we want
+			 * to return -EEXIST immediately.
+			 */
+			if (err == -EEXIST && !(size_flag & RADIX_DAX_PMD))
 				goto restart;
+			/*
+			 * Our insertion of a DAX PMD entry failed, most
+			 * likely because it collided with a PTE sized entry
+			 * at a different index in the PMD range.  We haven't
+			 * inserted anything into the radix tree and have no
+			 * waiters to wake.
+			 */
 			return ERR_PTR(err);
 		}
 		/* Good, we have inserted empty locked entry into the tree. */
@@ -466,6 +566,7 @@ restart:
 		return page;
 	}
 	entry = lock_slot(mapping, slot);
+ out_unlock:
 	spin_unlock_irq(&mapping->tree_lock);
 	return entry;
 }
@@ -473,9 +574,9 @@ restart:
 /*
  * We do not necessarily hold the mapping->tree_lock when we call this
  * function so it is possible that 'entry' is no longer a valid item in the
- * radix tree.  This is okay, though, because all we really need to do is to
- * find the correct waitqueue where tasks might be sleeping waiting for that
- * old 'entry' and wake them.
+ * radix tree.  This is okay because all we really need to do is to find the
+ * correct waitqueue where tasks might be waiting for that old 'entry' and
+ * wake them.
  */
 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 		pgoff_t index, void *entry, bool wake_all)
@@ -588,11 +689,17 @@ static int copy_user_dax(struct block_device *bdev, sector_t sector, size_t size
 	return 0;
 }
 
-#define DAX_PMD_INDEX(page_index) (page_index & (PMD_MASK >> PAGE_SHIFT))
-
+/*
+ * By this point grab_mapping_entry() has ensured that we have a locked entry
+ * of the appropriate size so we don't have to worry about downgrading PMDs to
+ * PTEs.  If we happen to be trying to insert a PTE and there is a PMD
+ * already in the tree, we will skip the insertion and just dirty the PMD as
+ * appropriate.
+ */
 static void *dax_insert_mapping_entry(struct address_space *mapping,
 				      struct vm_fault *vmf,
-				      void *entry, sector_t sector)
+				      void *entry, sector_t sector,
+				      unsigned long flags)
 {
 	struct radix_tree_root *page_tree = &mapping->page_tree;
 	int error = 0;
@@ -615,22 +722,35 @@ static void *dax_insert_mapping_entry(struct address_space *mapping,
 		error = radix_tree_preload(vmf->gfp_mask & ~__GFP_HIGHMEM);
 		if (error)
 			return ERR_PTR(error);
+	} else if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_HZP)) {
+		/* replacing huge zero page with PMD block mapping */
+		unmap_mapping_range(mapping,
+			(vmf->pgoff << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
 	}
 
 	spin_lock_irq(&mapping->tree_lock);
-	new_entry = (void *)((unsigned long)RADIX_DAX_ENTRY(sector, false) |
-		       RADIX_DAX_ENTRY_LOCK);
+	new_entry = dax_radix_locked_entry(sector, flags);
+
 	if (hole_fill) {
 		__delete_from_page_cache(entry, NULL);
 		/* Drop pagecache reference */
 		put_page(entry);
-		error = radix_tree_insert(page_tree, index, new_entry);
+		error = __radix_tree_insert(page_tree, index,
+				dax_radix_order(new_entry), new_entry);
 		if (error) {
 			new_entry = ERR_PTR(error);
 			goto unlock;
 		}
 		mapping->nrexceptional++;
-	} else {
+	} else if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
+		/*
+		 * Only swap our new entry into the radix tree if the current
+		 * entry is a zero page or an empty entry.  If a normal PTE or
+		 * PMD entry is already in the tree, we leave it alone.  This
+		 * means that if we are trying to insert a PTE and the
+		 * existing entry is a PMD, we will just leave the PMD in the
+		 * tree and dirty it if necessary.
+		 */
 		void **slot;
 		void *ret;
 
@@ -660,7 +780,6 @@ static int dax_writeback_one(struct block_device *bdev,
 		struct address_space *mapping, pgoff_t index, void *entry)
 {
 	struct radix_tree_root *page_tree = &mapping->page_tree;
-	int type = RADIX_DAX_TYPE(entry);
 	struct radix_tree_node *node;
 	struct blk_dax_ctl dax;
 	void **slot;
@@ -681,13 +800,21 @@ static int dax_writeback_one(struct block_device *bdev,
 	if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
 		goto unlock;
 
-	if (WARN_ON_ONCE(type != RADIX_DAX_PTE && type != RADIX_DAX_PMD)) {
+	if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
+				dax_is_zero_entry(entry))) {
 		ret = -EIO;
 		goto unlock;
 	}
 
-	dax.sector = RADIX_DAX_SECTOR(entry);
-	dax.size = (type == RADIX_DAX_PMD ? PMD_SIZE : PAGE_SIZE);
+	/*
+	 * Even if dax_writeback_mapping_range() was given a wbc->range_start
+	 * in the middle of a PMD, the 'index' we are given will be aligned to
+	 * the start index of the PMD, as will the sector we pull from
+	 * 'entry'.  This allows us to flush for PMD_SIZE and not have to
+	 * worry about partial PMD writebacks.
+	 */
+	dax.sector = dax_radix_sector(entry);
+	dax.size = PAGE_SIZE << dax_radix_order(entry);
 	spin_unlock_irq(&mapping->tree_lock);
 
 	/*
@@ -726,12 +853,11 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 		struct block_device *bdev, struct writeback_control *wbc)
 {
 	struct inode *inode = mapping->host;
-	pgoff_t start_index, end_index, pmd_index;
+	pgoff_t start_index, end_index;
 	pgoff_t indices[PAGEVEC_SIZE];
 	struct pagevec pvec;
 	bool done = false;
 	int i, ret = 0;
-	void *entry;
 
 	if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
 		return -EIO;
@@ -741,15 +867,6 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 
 	start_index = wbc->range_start >> PAGE_SHIFT;
 	end_index = wbc->range_end >> PAGE_SHIFT;
-	pmd_index = DAX_PMD_INDEX(start_index);
-
-	rcu_read_lock();
-	entry = radix_tree_lookup(&mapping->page_tree, pmd_index);
-	rcu_read_unlock();
-
-	/* see if the start of our range is covered by a PMD entry */
-	if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
-		start_index = pmd_index;
 
 	tag_pages_for_writeback(mapping, start_index, end_index);
 
@@ -794,7 +911,7 @@ static int dax_insert_mapping(struct address_space *mapping,
 		return PTR_ERR(dax.addr);
 	dax_unmap_atomic(bdev, &dax);
 
-	ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector);
+	ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector, 0);
 	if (IS_ERR(ret))
 		return PTR_ERR(ret);
 	*entryp = ret;
@@ -841,7 +958,7 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	bh.b_bdev = inode->i_sb->s_bdev;
 	bh.b_size = PAGE_SIZE;
 
-	entry = grab_mapping_entry(mapping, vmf->pgoff);
+	entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
 	if (IS_ERR(entry)) {
 		error = PTR_ERR(entry);
 		goto out;
@@ -1162,7 +1279,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	if (pos >= i_size_read(inode))
 		return VM_FAULT_SIGBUS;
 
-	entry = grab_mapping_entry(mapping, vmf->pgoff);
+	entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
 	if (IS_ERR(entry)) {
 		error = PTR_ERR(entry);
 		goto out;
@@ -1264,4 +1381,191 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	return VM_FAULT_NOPAGE | major;
 }
 EXPORT_SYMBOL_GPL(dax_iomap_fault);
+
+#ifdef CONFIG_FS_DAX_PMD
+/*
+ * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
+ * more often than one might expect in the below functions.
+ */
+#define PG_PMD_COLOUR	((PMD_SIZE >> PAGE_SHIFT) - 1)
+
+static int dax_pmd_insert_mapping(struct vm_area_struct *vma, pmd_t *pmd,
+		struct vm_fault *vmf, unsigned long address,
+		struct iomap *iomap, loff_t pos, bool write, void **entryp)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	struct block_device *bdev = iomap->bdev;
+	struct blk_dax_ctl dax = {
+		.sector = dax_iomap_sector(iomap, pos),
+		.size = PMD_SIZE,
+	};
+	long length = dax_map_atomic(bdev, &dax);
+	void *ret;
+
+	if (length < 0) /* dax_map_atomic() failed */
+		return VM_FAULT_FALLBACK;
+	if (length < PMD_SIZE)
+		goto unmap_fallback;
+	if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR)
+		goto unmap_fallback;
+	if (!pfn_t_devmap(dax.pfn))
+		goto unmap_fallback;
+
+	dax_unmap_atomic(bdev, &dax);
+
+	ret = dax_insert_mapping_entry(mapping, vmf, *entryp, dax.sector,
+			RADIX_DAX_PMD);
+	if (IS_ERR(ret))
+		return VM_FAULT_FALLBACK;
+	*entryp = ret;
+
+	return vmf_insert_pfn_pmd(vma, address, pmd, dax.pfn, write);
+
+ unmap_fallback:
+	dax_unmap_atomic(bdev, &dax);
+	return VM_FAULT_FALLBACK;
+}
+
+static int dax_pmd_load_hole(struct vm_area_struct *vma, pmd_t *pmd,
+		struct vm_fault *vmf, unsigned long address,
+		struct iomap *iomap, void **entryp)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	unsigned long pmd_addr = address & PMD_MASK;
+	struct page *zero_page;
+	spinlock_t *ptl;
+	pmd_t pmd_entry;
+	void *ret;
+
+	zero_page = get_huge_zero_page();
+
+	if (unlikely(!zero_page))
+		return VM_FAULT_FALLBACK;
+
+	ret = dax_insert_mapping_entry(mapping, vmf, *entryp, 0,
+			RADIX_DAX_PMD | RADIX_DAX_HZP);
+	if (IS_ERR(ret))
+		return VM_FAULT_FALLBACK;
+	*entryp = ret;
+
+	ptl = pmd_lock(vma->vm_mm, pmd);
+	if (!pmd_none(*pmd)) {
+		spin_unlock(ptl);
+		return VM_FAULT_FALLBACK;
+	}
+
+	pmd_entry = mk_pmd(zero_page, vma->vm_page_prot);
+	pmd_entry = pmd_mkhuge(pmd_entry);
+	set_pmd_at(vma->vm_mm, pmd_addr, pmd, pmd_entry);
+	spin_unlock(ptl);
+	return VM_FAULT_NOPAGE;
+}
+
+int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
+		pmd_t *pmd, unsigned int flags, struct iomap_ops *ops)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	unsigned long pmd_addr = address & PMD_MASK;
+	bool write = flags & FAULT_FLAG_WRITE;
+	unsigned int iomap_flags = write ? IOMAP_WRITE : 0;
+	struct inode *inode = mapping->host;
+	int result = VM_FAULT_FALLBACK;
+	struct iomap iomap = { 0 };
+	pgoff_t max_pgoff, pgoff;
+	struct vm_fault vmf;
+	void *entry;
+	loff_t pos;
+	int error;
+
+	/* Fall back to PTEs if we're going to COW */
+	if (write && !(vma->vm_flags & VM_SHARED)) {
+		split_huge_pmd(vma, pmd, address);
+		goto fallback;
+	}
+
+	/* If the PMD would extend outside the VMA */
+	if (pmd_addr < vma->vm_start)
+		goto fallback;
+	if ((pmd_addr + PMD_SIZE) > vma->vm_end)
+		goto fallback;
+
+	/*
+	 * Check whether offset isn't beyond end of file now. Caller is
+	 * supposed to hold locks serializing us with truncate / punch hole so
+	 * this is a reliable test.
+	 */
+	pgoff = linear_page_index(vma, pmd_addr);
+	max_pgoff = (i_size_read(inode) - 1) >> PAGE_SHIFT;
+
+	if (pgoff > max_pgoff)
+		return VM_FAULT_SIGBUS;
+
+	/* If the PMD would extend beyond the file size */
+	if ((pgoff | PG_PMD_COLOUR) > max_pgoff)
+		goto fallback;
+
+	/*
+	 * grab_mapping_entry() will make sure we get a 2M empty entry, a DAX
+	 * PMD or a HZP entry.  If it can't (because a 4k page is already in
+	 * the tree, for instance), it will return -EEXIST and we just fall
+	 * back to 4k entries.
+	 */
+	entry = grab_mapping_entry(mapping, pgoff, RADIX_DAX_PMD);
+	if (IS_ERR(entry))
+		goto fallback;
+
+	/*
+	 * Note that we don't use iomap_apply here.  We aren't doing I/O, only
+	 * setting up a mapping, so really we're using iomap_begin() as a way
+	 * to look up our filesystem block.
+	 */
+	pos = (loff_t)pgoff << PAGE_SHIFT;
+	error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap);
+	if (error)
+		goto unlock_entry;
+	if (iomap.offset + iomap.length < pos + PMD_SIZE)
+		goto finish_iomap;
+
+	vmf.pgoff = pgoff;
+	vmf.flags = flags;
+	vmf.gfp_mask = mapping_gfp_mask(mapping) | __GFP_IO;
+
+	switch (iomap.type) {
+	case IOMAP_MAPPED:
+		result = dax_pmd_insert_mapping(vma, pmd, &vmf, address,
+				&iomap, pos, write, &entry);
+		break;
+	case IOMAP_UNWRITTEN:
+	case IOMAP_HOLE:
+		if (WARN_ON_ONCE(write))
+			goto finish_iomap;
+		result = dax_pmd_load_hole(vma, pmd, &vmf, address, &iomap,
+				&entry);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		break;
+	}
+
+ finish_iomap:
+	if (ops->iomap_end) {
+		if (result == VM_FAULT_FALLBACK) {
+			ops->iomap_end(inode, pos, PMD_SIZE, 0, iomap_flags,
+					&iomap);
+		} else {
+			error = ops->iomap_end(inode, pos, PMD_SIZE, PMD_SIZE,
+					iomap_flags, &iomap);
+			if (error)
+				result = VM_FAULT_FALLBACK;
+		}
+	}
+ unlock_entry:
+	put_locked_mapping_entry(mapping, pgoff, entry);
+ fallback:
+	if (result == VM_FAULT_FALLBACK)
+		count_vm_event(THP_FAULT_FALLBACK);
+	return result;
+}
+EXPORT_SYMBOL_GPL(dax_iomap_pmd_fault);
+#endif /* CONFIG_FS_DAX_PMD */
 #endif /* CONFIG_FS_IOMAP */
diff --git a/include/linux/dax.h b/include/linux/dax.h
index e9ea78c..8d1a5c4 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -9,20 +9,32 @@
 struct iomap_ops;
 
 /*
- * We use lowest available bit in exceptional entry for locking, other two
- * bits to determine entry type. In total 3 special bits.
+ * We use lowest available bit in exceptional entry for locking, one bit for
+ * the entry size (PMD) and two more to tell us if the entry is a huge zero
+ * page (HZP) or an empty entry that is just used for locking.  In total four
+ * special bits.
+ *
+ * If the PMD bit isn't set the entry has size PAGE_SIZE, and if the HZP and
+ * EMPTY bits aren't set the entry is a normal DAX entry with a filesystem
+ * block allocation.
  */
-#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 3)
+#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 4)
 #define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
-#define RADIX_DAX_PTE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
-#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
-#define RADIX_DAX_TYPE_MASK (RADIX_DAX_PTE | RADIX_DAX_PMD)
-#define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_TYPE_MASK)
-#define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
-#define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
-		RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE) | \
-		RADIX_TREE_EXCEPTIONAL_ENTRY))
+#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
+#define RADIX_DAX_HZP (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
+#define RADIX_DAX_EMPTY (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 3))
 
+static inline unsigned long dax_radix_sector(void *entry)
+{
+	return (unsigned long)entry >> RADIX_DAX_SHIFT;
+}
+
+static inline void *dax_radix_locked_entry(sector_t sector, unsigned long flags)
+{
+	return (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY | flags |
+			((unsigned long)sector << RADIX_DAX_SHIFT) |
+			RADIX_DAX_ENTRY_LOCK);
+}
 
 ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_ops *ops);
@@ -67,6 +79,27 @@ static inline int dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
 	return VM_FAULT_FALLBACK;
 }
 
+#ifdef CONFIG_FS_DAX_PMD
+static inline unsigned int dax_radix_order(void *entry)
+{
+	if ((unsigned long)entry & RADIX_DAX_PMD)
+		return PMD_SHIFT - PAGE_SHIFT;
+	return 0;
+}
+int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
+		pmd_t *pmd, unsigned int flags, struct iomap_ops *ops);
+#else
+static inline unsigned int dax_radix_order(void *entry)
+{
+	return 0;
+}
+static inline int dax_iomap_pmd_fault(struct vm_area_struct *vma,
+		unsigned long address, pmd_t *pmd, unsigned int flags,
+		struct iomap_ops *ops)
+{
+	return VM_FAULT_FALLBACK;
+}
+#endif
 int dax_pfn_mkwrite(struct vm_area_struct *, struct vm_fault *);
 #define dax_mkwrite(vma, vmf, gb)	dax_fault(vma, vmf, gb)
 
diff --git a/mm/filemap.c b/mm/filemap.c
index a596462..592e6e9 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -611,8 +611,7 @@ static int page_cache_tree_insert(struct address_space *mapping,
 		} else {
 			/* DAX can replace empty locked entry with a hole */
 			WARN_ON_ONCE(p !=
-				(void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
-					 RADIX_DAX_ENTRY_LOCK));
+				dax_radix_locked_entry(0, RADIX_DAX_EMPTY));
 			/* DAX accounts exceptional entries as normal pages */
 			if (node)
 				workingset_node_pages_dec(node);
-- 
2.7.4

^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v7 15/17] dax: add struct iomap based DAX PMD support
@ 2016-10-13 19:23       ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-13 19:23 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
locking.  This patch allows DAX PMDs to participate in the DAX radix tree
based locking scheme so that they can be re-enabled using the new struct
iomap based fault handlers.

There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
mappings that have an associated block allocation, and 4k DAX empty
entries.  The empty entries exist to provide locking for the duration of a
given page fault.

This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
entries, PMD DAX entries that have associated block allocations, and 2 MiB
DAX empty entries.

Unlike the 4k case where we insert a struct page* into the radix tree for
4k zero pages, for HZP we insert a DAX exceptional entry with the new
RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
every 2MiB hole mapping, and it doesn't make sense to have that same struct
page* with multiple entries in multiple trees.  This would cause contention
on the single page lock for the one Huge Zero Page, and it would break the
page->index and page->mapping associations that are assumed to be valid in
many other places in the kernel.

One difficult use case is when one thread is trying to use 4k entries in
radix tree for a given offset, and another thread is using 2 MiB entries
for that same offset.  The current code handles this by making the 2 MiB
user fall back to 4k entries for most cases.  This was done because it is
the simplest solution, and because the use of 2MiB pages is already
opportunistic.

If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
we run into the problem of how we lock out 4k page faults for the entire
2MiB range while we clean out the radix tree so we can insert the 2MiB
entry.  We can solve this problem if we need to, but I think that the cases
where both 2MiB entries and 4K entries are being used for the same range
will be rare enough and the gain small enough that it probably won't be
worth the complexity.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c            | 378 +++++++++++++++++++++++++++++++++++++++++++++++-----
 include/linux/dax.h |  55 ++++++--
 mm/filemap.c        |   3 +-
 3 files changed, 386 insertions(+), 50 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 0582c7c..153cfd5 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -76,6 +76,26 @@ static void dax_unmap_atomic(struct block_device *bdev,
 	blk_queue_exit(bdev->bd_queue);
 }
 
+static int dax_is_pmd_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_PMD;
+}
+
+static int dax_is_pte_entry(void *entry)
+{
+	return !((unsigned long)entry & RADIX_DAX_PMD);
+}
+
+static int dax_is_zero_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_HZP;
+}
+
+static int dax_is_empty_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_EMPTY;
+}
+
 struct page *read_dax_sector(struct block_device *bdev, sector_t n)
 {
 	struct page *page = alloc_pages(GFP_KERNEL, 0);
@@ -281,7 +301,7 @@ static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
 	 * queue to the start of that PMD.  This ensures that all offsets in
 	 * the range covered by the PMD map to the same bit lock.
 	 */
-	if (RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
+	if (dax_is_pmd_entry(entry))
 		index &= ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1);
 
 	key->mapping = mapping;
@@ -413,36 +433,116 @@ static void put_unlocked_mapping_entry(struct address_space *mapping,
  * radix tree entry locked. If the radix tree doesn't contain given index,
  * create empty exceptional entry for the index and return with it locked.
  *
+ * When requesting an entry with size RADIX_DAX_PMD, grab_mapping_entry() will
+ * either return that locked entry or will return an error.  This error will
+ * happen if there are any 4k entries (either zero pages or DAX entries)
+ * within the 2MiB range that we are requesting.
+ *
+ * We always favor 4k entries over 2MiB entries. There isn't a flow where we
+ * evict 4k entries in order to 'upgrade' them to a 2MiB entry.  A 2MiB
+ * insertion will fail if it finds any 4k entries already in the tree, and a
+ * 4k insertion will cause an existing 2MiB entry to be unmapped and
+ * downgraded to 4k entries.  This happens for both 2MiB huge zero pages as
+ * well as 2MiB empty entries.
+ *
+ * The exception to this downgrade path is for 2MiB DAX PMD entries that have
+ * real storage backing them.  We will leave these real 2MiB DAX entries in
+ * the tree, and PTE writes will simply dirty the entire 2MiB DAX entry.
+ *
  * Note: Unlike filemap_fault() we don't honor FAULT_FLAG_RETRY flags. For
  * persistent memory the benefit is doubtful. We can add that later if we can
  * show it helps.
  */
-static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index)
+static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
+		unsigned long size_flag)
 {
+	bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */
 	void *entry, **slot;
 
 restart:
 	spin_lock_irq(&mapping->tree_lock);
 	entry = get_unlocked_mapping_entry(mapping, index, &slot);
+
+	if (entry) {
+		if (size_flag & RADIX_DAX_PMD) {
+			if (!radix_tree_exceptional_entry(entry) ||
+			    dax_is_pte_entry(entry)) {
+				put_unlocked_mapping_entry(mapping, index,
+						entry);
+				entry = ERR_PTR(-EEXIST);
+				goto out_unlock;
+			}
+		} else { /* trying to grab a PTE entry */
+			if (radix_tree_exceptional_entry(entry) &&
+			    dax_is_pmd_entry(entry) &&
+			    (dax_is_zero_entry(entry) ||
+			     dax_is_empty_entry(entry))) {
+				pmd_downgrade = true;
+			}
+		}
+	}
+
 	/* No entry for given index? Make sure radix tree is big enough. */
-	if (!entry) {
+	if (!entry || pmd_downgrade) {
 		int err;
 
+		if (pmd_downgrade) {
+			/*
+			 * Make sure 'entry' remains valid while we drop
+			 * mapping->tree_lock.
+			 */
+			entry = lock_slot(mapping, slot);
+		}
+
 		spin_unlock_irq(&mapping->tree_lock);
 		err = radix_tree_preload(
 				mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
-		if (err)
+		if (err) {
+			if (pmd_downgrade)
+				put_locked_mapping_entry(mapping, index, entry);
 			return ERR_PTR(err);
-		entry = (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
-			       RADIX_DAX_ENTRY_LOCK);
+		}
+
+		/*
+		 * Besides huge zero pages the only other thing that gets
+		 * downgraded are empty entries which don't need to be
+		 * unmapped.
+		 */
+		if (pmd_downgrade && dax_is_zero_entry(entry))
+			unmap_mapping_range(mapping,
+				(index << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
+
 		spin_lock_irq(&mapping->tree_lock);
-		err = radix_tree_insert(&mapping->page_tree, index, entry);
+
+		if (pmd_downgrade) {
+			radix_tree_delete(&mapping->page_tree, index);
+			mapping->nrexceptional--;
+			dax_wake_mapping_entry_waiter(mapping, index, entry,
+					true);
+		}
+
+		entry = dax_radix_locked_entry(0, size_flag | RADIX_DAX_EMPTY);
+
+		err = __radix_tree_insert(&mapping->page_tree, index,
+				dax_radix_order(entry), entry);
 		radix_tree_preload_end();
 		if (err) {
 			spin_unlock_irq(&mapping->tree_lock);
-			/* Someone already created the entry? */
-			if (err == -EEXIST)
+			/*
+			 * Someone already created the entry?  This is a
+			 * normal failure when inserting PMDs in a range
+			 * that already contains PTEs.  In that case we want
+			 * to return -EEXIST immediately.
+			 */
+			if (err == -EEXIST && !(size_flag & RADIX_DAX_PMD))
 				goto restart;
+			/*
+			 * Our insertion of a DAX PMD entry failed, most
+			 * likely because it collided with a PTE sized entry
+			 * at a different index in the PMD range.  We haven't
+			 * inserted anything into the radix tree and have no
+			 * waiters to wake.
+			 */
 			return ERR_PTR(err);
 		}
 		/* Good, we have inserted empty locked entry into the tree. */
@@ -466,6 +566,7 @@ restart:
 		return page;
 	}
 	entry = lock_slot(mapping, slot);
+ out_unlock:
 	spin_unlock_irq(&mapping->tree_lock);
 	return entry;
 }
@@ -473,9 +574,9 @@ restart:
 /*
  * We do not necessarily hold the mapping->tree_lock when we call this
  * function so it is possible that 'entry' is no longer a valid item in the
- * radix tree.  This is okay, though, because all we really need to do is to
- * find the correct waitqueue where tasks might be sleeping waiting for that
- * old 'entry' and wake them.
+ * radix tree.  This is okay because all we really need to do is to find the
+ * correct waitqueue where tasks might be waiting for that old 'entry' and
+ * wake them.
  */
 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 		pgoff_t index, void *entry, bool wake_all)
@@ -588,11 +689,17 @@ static int copy_user_dax(struct block_device *bdev, sector_t sector, size_t size
 	return 0;
 }
 
-#define DAX_PMD_INDEX(page_index) (page_index & (PMD_MASK >> PAGE_SHIFT))
-
+/*
+ * By this point grab_mapping_entry() has ensured that we have a locked entry
+ * of the appropriate size so we don't have to worry about downgrading PMDs to
+ * PTEs.  If we happen to be trying to insert a PTE and there is a PMD
+ * already in the tree, we will skip the insertion and just dirty the PMD as
+ * appropriate.
+ */
 static void *dax_insert_mapping_entry(struct address_space *mapping,
 				      struct vm_fault *vmf,
-				      void *entry, sector_t sector)
+				      void *entry, sector_t sector,
+				      unsigned long flags)
 {
 	struct radix_tree_root *page_tree = &mapping->page_tree;
 	int error = 0;
@@ -615,22 +722,35 @@ static void *dax_insert_mapping_entry(struct address_space *mapping,
 		error = radix_tree_preload(vmf->gfp_mask & ~__GFP_HIGHMEM);
 		if (error)
 			return ERR_PTR(error);
+	} else if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_HZP)) {
+		/* replacing huge zero page with PMD block mapping */
+		unmap_mapping_range(mapping,
+			(vmf->pgoff << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
 	}
 
 	spin_lock_irq(&mapping->tree_lock);
-	new_entry = (void *)((unsigned long)RADIX_DAX_ENTRY(sector, false) |
-		       RADIX_DAX_ENTRY_LOCK);
+	new_entry = dax_radix_locked_entry(sector, flags);
+
 	if (hole_fill) {
 		__delete_from_page_cache(entry, NULL);
 		/* Drop pagecache reference */
 		put_page(entry);
-		error = radix_tree_insert(page_tree, index, new_entry);
+		error = __radix_tree_insert(page_tree, index,
+				dax_radix_order(new_entry), new_entry);
 		if (error) {
 			new_entry = ERR_PTR(error);
 			goto unlock;
 		}
 		mapping->nrexceptional++;
-	} else {
+	} else if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
+		/*
+		 * Only swap our new entry into the radix tree if the current
+		 * entry is a zero page or an empty entry.  If a normal PTE or
+		 * PMD entry is already in the tree, we leave it alone.  This
+		 * means that if we are trying to insert a PTE and the
+		 * existing entry is a PMD, we will just leave the PMD in the
+		 * tree and dirty it if necessary.
+		 */
 		void **slot;
 		void *ret;
 
@@ -660,7 +780,6 @@ static int dax_writeback_one(struct block_device *bdev,
 		struct address_space *mapping, pgoff_t index, void *entry)
 {
 	struct radix_tree_root *page_tree = &mapping->page_tree;
-	int type = RADIX_DAX_TYPE(entry);
 	struct radix_tree_node *node;
 	struct blk_dax_ctl dax;
 	void **slot;
@@ -681,13 +800,21 @@ static int dax_writeback_one(struct block_device *bdev,
 	if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
 		goto unlock;
 
-	if (WARN_ON_ONCE(type != RADIX_DAX_PTE && type != RADIX_DAX_PMD)) {
+	if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
+				dax_is_zero_entry(entry))) {
 		ret = -EIO;
 		goto unlock;
 	}
 
-	dax.sector = RADIX_DAX_SECTOR(entry);
-	dax.size = (type == RADIX_DAX_PMD ? PMD_SIZE : PAGE_SIZE);
+	/*
+	 * Even if dax_writeback_mapping_range() was given a wbc->range_start
+	 * in the middle of a PMD, the 'index' we are given will be aligned to
+	 * the start index of the PMD, as will the sector we pull from
+	 * 'entry'.  This allows us to flush for PMD_SIZE and not have to
+	 * worry about partial PMD writebacks.
+	 */
+	dax.sector = dax_radix_sector(entry);
+	dax.size = PAGE_SIZE << dax_radix_order(entry);
 	spin_unlock_irq(&mapping->tree_lock);
 
 	/*
@@ -726,12 +853,11 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 		struct block_device *bdev, struct writeback_control *wbc)
 {
 	struct inode *inode = mapping->host;
-	pgoff_t start_index, end_index, pmd_index;
+	pgoff_t start_index, end_index;
 	pgoff_t indices[PAGEVEC_SIZE];
 	struct pagevec pvec;
 	bool done = false;
 	int i, ret = 0;
-	void *entry;
 
 	if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
 		return -EIO;
@@ -741,15 +867,6 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 
 	start_index = wbc->range_start >> PAGE_SHIFT;
 	end_index = wbc->range_end >> PAGE_SHIFT;
-	pmd_index = DAX_PMD_INDEX(start_index);
-
-	rcu_read_lock();
-	entry = radix_tree_lookup(&mapping->page_tree, pmd_index);
-	rcu_read_unlock();
-
-	/* see if the start of our range is covered by a PMD entry */
-	if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
-		start_index = pmd_index;
 
 	tag_pages_for_writeback(mapping, start_index, end_index);
 
@@ -794,7 +911,7 @@ static int dax_insert_mapping(struct address_space *mapping,
 		return PTR_ERR(dax.addr);
 	dax_unmap_atomic(bdev, &dax);
 
-	ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector);
+	ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector, 0);
 	if (IS_ERR(ret))
 		return PTR_ERR(ret);
 	*entryp = ret;
@@ -841,7 +958,7 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	bh.b_bdev = inode->i_sb->s_bdev;
 	bh.b_size = PAGE_SIZE;
 
-	entry = grab_mapping_entry(mapping, vmf->pgoff);
+	entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
 	if (IS_ERR(entry)) {
 		error = PTR_ERR(entry);
 		goto out;
@@ -1162,7 +1279,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	if (pos >= i_size_read(inode))
 		return VM_FAULT_SIGBUS;
 
-	entry = grab_mapping_entry(mapping, vmf->pgoff);
+	entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
 	if (IS_ERR(entry)) {
 		error = PTR_ERR(entry);
 		goto out;
@@ -1264,4 +1381,191 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	return VM_FAULT_NOPAGE | major;
 }
 EXPORT_SYMBOL_GPL(dax_iomap_fault);
+
+#ifdef CONFIG_FS_DAX_PMD
+/*
+ * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
+ * more often than one might expect in the below functions.
+ */
+#define PG_PMD_COLOUR	((PMD_SIZE >> PAGE_SHIFT) - 1)
+
+static int dax_pmd_insert_mapping(struct vm_area_struct *vma, pmd_t *pmd,
+		struct vm_fault *vmf, unsigned long address,
+		struct iomap *iomap, loff_t pos, bool write, void **entryp)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	struct block_device *bdev = iomap->bdev;
+	struct blk_dax_ctl dax = {
+		.sector = dax_iomap_sector(iomap, pos),
+		.size = PMD_SIZE,
+	};
+	long length = dax_map_atomic(bdev, &dax);
+	void *ret;
+
+	if (length < 0) /* dax_map_atomic() failed */
+		return VM_FAULT_FALLBACK;
+	if (length < PMD_SIZE)
+		goto unmap_fallback;
+	if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR)
+		goto unmap_fallback;
+	if (!pfn_t_devmap(dax.pfn))
+		goto unmap_fallback;
+
+	dax_unmap_atomic(bdev, &dax);
+
+	ret = dax_insert_mapping_entry(mapping, vmf, *entryp, dax.sector,
+			RADIX_DAX_PMD);
+	if (IS_ERR(ret))
+		return VM_FAULT_FALLBACK;
+	*entryp = ret;
+
+	return vmf_insert_pfn_pmd(vma, address, pmd, dax.pfn, write);
+
+ unmap_fallback:
+	dax_unmap_atomic(bdev, &dax);
+	return VM_FAULT_FALLBACK;
+}
+
+static int dax_pmd_load_hole(struct vm_area_struct *vma, pmd_t *pmd,
+		struct vm_fault *vmf, unsigned long address,
+		struct iomap *iomap, void **entryp)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	unsigned long pmd_addr = address & PMD_MASK;
+	struct page *zero_page;
+	spinlock_t *ptl;
+	pmd_t pmd_entry;
+	void *ret;
+
+	zero_page = get_huge_zero_page();
+
+	if (unlikely(!zero_page))
+		return VM_FAULT_FALLBACK;
+
+	ret = dax_insert_mapping_entry(mapping, vmf, *entryp, 0,
+			RADIX_DAX_PMD | RADIX_DAX_HZP);
+	if (IS_ERR(ret))
+		return VM_FAULT_FALLBACK;
+	*entryp = ret;
+
+	ptl = pmd_lock(vma->vm_mm, pmd);
+	if (!pmd_none(*pmd)) {
+		spin_unlock(ptl);
+		return VM_FAULT_FALLBACK;
+	}
+
+	pmd_entry = mk_pmd(zero_page, vma->vm_page_prot);
+	pmd_entry = pmd_mkhuge(pmd_entry);
+	set_pmd_at(vma->vm_mm, pmd_addr, pmd, pmd_entry);
+	spin_unlock(ptl);
+	return VM_FAULT_NOPAGE;
+}
+
+int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
+		pmd_t *pmd, unsigned int flags, struct iomap_ops *ops)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	unsigned long pmd_addr = address & PMD_MASK;
+	bool write = flags & FAULT_FLAG_WRITE;
+	unsigned int iomap_flags = write ? IOMAP_WRITE : 0;
+	struct inode *inode = mapping->host;
+	int result = VM_FAULT_FALLBACK;
+	struct iomap iomap = { 0 };
+	pgoff_t max_pgoff, pgoff;
+	struct vm_fault vmf;
+	void *entry;
+	loff_t pos;
+	int error;
+
+	/* Fall back to PTEs if we're going to COW */
+	if (write && !(vma->vm_flags & VM_SHARED)) {
+		split_huge_pmd(vma, pmd, address);
+		goto fallback;
+	}
+
+	/* If the PMD would extend outside the VMA */
+	if (pmd_addr < vma->vm_start)
+		goto fallback;
+	if ((pmd_addr + PMD_SIZE) > vma->vm_end)
+		goto fallback;
+
+	/*
+	 * Check whether offset isn't beyond end of file now. Caller is
+	 * supposed to hold locks serializing us with truncate / punch hole so
+	 * this is a reliable test.
+	 */
+	pgoff = linear_page_index(vma, pmd_addr);
+	max_pgoff = (i_size_read(inode) - 1) >> PAGE_SHIFT;
+
+	if (pgoff > max_pgoff)
+		return VM_FAULT_SIGBUS;
+
+	/* If the PMD would extend beyond the file size */
+	if ((pgoff | PG_PMD_COLOUR) > max_pgoff)
+		goto fallback;
+
+	/*
+	 * grab_mapping_entry() will make sure we get a 2M empty entry, a DAX
+	 * PMD or a HZP entry.  If it can't (because a 4k page is already in
+	 * the tree, for instance), it will return -EEXIST and we just fall
+	 * back to 4k entries.
+	 */
+	entry = grab_mapping_entry(mapping, pgoff, RADIX_DAX_PMD);
+	if (IS_ERR(entry))
+		goto fallback;
+
+	/*
+	 * Note that we don't use iomap_apply here.  We aren't doing I/O, only
+	 * setting up a mapping, so really we're using iomap_begin() as a way
+	 * to look up our filesystem block.
+	 */
+	pos = (loff_t)pgoff << PAGE_SHIFT;
+	error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap);
+	if (error)
+		goto unlock_entry;
+	if (iomap.offset + iomap.length < pos + PMD_SIZE)
+		goto finish_iomap;
+
+	vmf.pgoff = pgoff;
+	vmf.flags = flags;
+	vmf.gfp_mask = mapping_gfp_mask(mapping) | __GFP_IO;
+
+	switch (iomap.type) {
+	case IOMAP_MAPPED:
+		result = dax_pmd_insert_mapping(vma, pmd, &vmf, address,
+				&iomap, pos, write, &entry);
+		break;
+	case IOMAP_UNWRITTEN:
+	case IOMAP_HOLE:
+		if (WARN_ON_ONCE(write))
+			goto finish_iomap;
+		result = dax_pmd_load_hole(vma, pmd, &vmf, address, &iomap,
+				&entry);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		break;
+	}
+
+ finish_iomap:
+	if (ops->iomap_end) {
+		if (result == VM_FAULT_FALLBACK) {
+			ops->iomap_end(inode, pos, PMD_SIZE, 0, iomap_flags,
+					&iomap);
+		} else {
+			error = ops->iomap_end(inode, pos, PMD_SIZE, PMD_SIZE,
+					iomap_flags, &iomap);
+			if (error)
+				result = VM_FAULT_FALLBACK;
+		}
+	}
+ unlock_entry:
+	put_locked_mapping_entry(mapping, pgoff, entry);
+ fallback:
+	if (result == VM_FAULT_FALLBACK)
+		count_vm_event(THP_FAULT_FALLBACK);
+	return result;
+}
+EXPORT_SYMBOL_GPL(dax_iomap_pmd_fault);
+#endif /* CONFIG_FS_DAX_PMD */
 #endif /* CONFIG_FS_IOMAP */
diff --git a/include/linux/dax.h b/include/linux/dax.h
index e9ea78c..8d1a5c4 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -9,20 +9,32 @@
 struct iomap_ops;
 
 /*
- * We use lowest available bit in exceptional entry for locking, other two
- * bits to determine entry type. In total 3 special bits.
+ * We use lowest available bit in exceptional entry for locking, one bit for
+ * the entry size (PMD) and two more to tell us if the entry is a huge zero
+ * page (HZP) or an empty entry that is just used for locking.  In total four
+ * special bits.
+ *
+ * If the PMD bit isn't set the entry has size PAGE_SIZE, and if the HZP and
+ * EMPTY bits aren't set the entry is a normal DAX entry with a filesystem
+ * block allocation.
  */
-#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 3)
+#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 4)
 #define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
-#define RADIX_DAX_PTE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
-#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
-#define RADIX_DAX_TYPE_MASK (RADIX_DAX_PTE | RADIX_DAX_PMD)
-#define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_TYPE_MASK)
-#define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
-#define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
-		RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE) | \
-		RADIX_TREE_EXCEPTIONAL_ENTRY))
+#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
+#define RADIX_DAX_HZP (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
+#define RADIX_DAX_EMPTY (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 3))
 
+static inline unsigned long dax_radix_sector(void *entry)
+{
+	return (unsigned long)entry >> RADIX_DAX_SHIFT;
+}
+
+static inline void *dax_radix_locked_entry(sector_t sector, unsigned long flags)
+{
+	return (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY | flags |
+			((unsigned long)sector << RADIX_DAX_SHIFT) |
+			RADIX_DAX_ENTRY_LOCK);
+}
 
 ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_ops *ops);
@@ -67,6 +79,27 @@ static inline int dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
 	return VM_FAULT_FALLBACK;
 }
 
+#ifdef CONFIG_FS_DAX_PMD
+static inline unsigned int dax_radix_order(void *entry)
+{
+	if ((unsigned long)entry & RADIX_DAX_PMD)
+		return PMD_SHIFT - PAGE_SHIFT;
+	return 0;
+}
+int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
+		pmd_t *pmd, unsigned int flags, struct iomap_ops *ops);
+#else
+static inline unsigned int dax_radix_order(void *entry)
+{
+	return 0;
+}
+static inline int dax_iomap_pmd_fault(struct vm_area_struct *vma,
+		unsigned long address, pmd_t *pmd, unsigned int flags,
+		struct iomap_ops *ops)
+{
+	return VM_FAULT_FALLBACK;
+}
+#endif
 int dax_pfn_mkwrite(struct vm_area_struct *, struct vm_fault *);
 #define dax_mkwrite(vma, vmf, gb)	dax_fault(vma, vmf, gb)
 
diff --git a/mm/filemap.c b/mm/filemap.c
index a596462..592e6e9 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -611,8 +611,7 @@ static int page_cache_tree_insert(struct address_space *mapping,
 		} else {
 			/* DAX can replace empty locked entry with a hole */
 			WARN_ON_ONCE(p !=
-				(void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
-					 RADIX_DAX_ENTRY_LOCK));
+				dax_radix_locked_entry(0, RADIX_DAX_EMPTY));
 			/* DAX accounts exceptional entries as normal pages */
 			if (node)
 				workingset_node_pages_dec(node);
-- 
2.7.4

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^ permalink raw reply related	[flat|nested] 126+ messages in thread
* [PATCH v7 15/17] dax: add struct iomap based DAX PMD support
@ 2016-10-13 19:23       ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-13 19:23 UTC (permalink / raw)
  To: linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
locking.  This patch allows DAX PMDs to participate in the DAX radix tree
based locking scheme so that they can be re-enabled using the new struct
iomap based fault handlers.

There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
mappings that have an associated block allocation, and 4k DAX empty
entries.  The empty entries exist to provide locking for the duration of a
given page fault.

This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
entries, PMD DAX entries that have associated block allocations, and 2 MiB
DAX empty entries.

Unlike the 4k case where we insert a struct page* into the radix tree for
4k zero pages, for HZP we insert a DAX exceptional entry with the new
RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
every 2MiB hole mapping, and it doesn't make sense to have that same struct
page* with multiple entries in multiple trees.  This would cause contention
on the single page lock for the one Huge Zero Page, and it would break the
page->index and page->mapping associations that are assumed to be valid in
many other places in the kernel.

One difficult use case is when one thread is trying to use 4k entries in
radix tree for a given offset, and another thread is using 2 MiB entries
for that same offset.  The current code handles this by making the 2 MiB
user fall back to 4k entries for most cases.  This was done because it is
the simplest solution, and because the use of 2MiB pages is already
opportunistic.

If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
we run into the problem of how we lock out 4k page faults for the entire
2MiB range while we clean out the radix tree so we can insert the 2MiB
entry.  We can solve this problem if we need to, but I think that the cases
where both 2MiB entries and 4K entries are being used for the same range
will be rare enough and the gain small enough that it probably won't be
worth the complexity.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c            | 378 +++++++++++++++++++++++++++++++++++++++++++++++-----
 include/linux/dax.h |  55 ++++++--
 mm/filemap.c        |   3 +-
 3 files changed, 386 insertions(+), 50 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 0582c7c..153cfd5 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -76,6 +76,26 @@ static void dax_unmap_atomic(struct block_device *bdev,
 	blk_queue_exit(bdev->bd_queue);
 }
 
+static int dax_is_pmd_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_PMD;
+}
+
+static int dax_is_pte_entry(void *entry)
+{
+	return !((unsigned long)entry & RADIX_DAX_PMD);
+}
+
+static int dax_is_zero_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_HZP;
+}
+
+static int dax_is_empty_entry(void *entry)
+{
+	return (unsigned long)entry & RADIX_DAX_EMPTY;
+}
+
 struct page *read_dax_sector(struct block_device *bdev, sector_t n)
 {
 	struct page *page = alloc_pages(GFP_KERNEL, 0);
@@ -281,7 +301,7 @@ static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
 	 * queue to the start of that PMD.  This ensures that all offsets in
 	 * the range covered by the PMD map to the same bit lock.
 	 */
-	if (RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
+	if (dax_is_pmd_entry(entry))
 		index &= ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1);
 
 	key->mapping = mapping;
@@ -413,36 +433,116 @@ static void put_unlocked_mapping_entry(struct address_space *mapping,
  * radix tree entry locked. If the radix tree doesn't contain given index,
  * create empty exceptional entry for the index and return with it locked.
  *
+ * When requesting an entry with size RADIX_DAX_PMD, grab_mapping_entry() will
+ * either return that locked entry or will return an error.  This error will
+ * happen if there are any 4k entries (either zero pages or DAX entries)
+ * within the 2MiB range that we are requesting.
+ *
+ * We always favor 4k entries over 2MiB entries. There isn't a flow where we
+ * evict 4k entries in order to 'upgrade' them to a 2MiB entry.  A 2MiB
+ * insertion will fail if it finds any 4k entries already in the tree, and a
+ * 4k insertion will cause an existing 2MiB entry to be unmapped and
+ * downgraded to 4k entries.  This happens for both 2MiB huge zero pages as
+ * well as 2MiB empty entries.
+ *
+ * The exception to this downgrade path is for 2MiB DAX PMD entries that have
+ * real storage backing them.  We will leave these real 2MiB DAX entries in
+ * the tree, and PTE writes will simply dirty the entire 2MiB DAX entry.
+ *
  * Note: Unlike filemap_fault() we don't honor FAULT_FLAG_RETRY flags. For
  * persistent memory the benefit is doubtful. We can add that later if we can
  * show it helps.
  */
-static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index)
+static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
+		unsigned long size_flag)
 {
+	bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */
 	void *entry, **slot;
 
 restart:
 	spin_lock_irq(&mapping->tree_lock);
 	entry = get_unlocked_mapping_entry(mapping, index, &slot);
+
+	if (entry) {
+		if (size_flag & RADIX_DAX_PMD) {
+			if (!radix_tree_exceptional_entry(entry) ||
+			    dax_is_pte_entry(entry)) {
+				put_unlocked_mapping_entry(mapping, index,
+						entry);
+				entry = ERR_PTR(-EEXIST);
+				goto out_unlock;
+			}
+		} else { /* trying to grab a PTE entry */
+			if (radix_tree_exceptional_entry(entry) &&
+			    dax_is_pmd_entry(entry) &&
+			    (dax_is_zero_entry(entry) ||
+			     dax_is_empty_entry(entry))) {
+				pmd_downgrade = true;
+			}
+		}
+	}
+
 	/* No entry for given index? Make sure radix tree is big enough. */
-	if (!entry) {
+	if (!entry || pmd_downgrade) {
 		int err;
 
+		if (pmd_downgrade) {
+			/*
+			 * Make sure 'entry' remains valid while we drop
+			 * mapping->tree_lock.
+			 */
+			entry = lock_slot(mapping, slot);
+		}
+
 		spin_unlock_irq(&mapping->tree_lock);
 		err = radix_tree_preload(
 				mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
-		if (err)
+		if (err) {
+			if (pmd_downgrade)
+				put_locked_mapping_entry(mapping, index, entry);
 			return ERR_PTR(err);
-		entry = (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
-			       RADIX_DAX_ENTRY_LOCK);
+		}
+
+		/*
+		 * Besides huge zero pages the only other thing that gets
+		 * downgraded are empty entries which don't need to be
+		 * unmapped.
+		 */
+		if (pmd_downgrade && dax_is_zero_entry(entry))
+			unmap_mapping_range(mapping,
+				(index << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
+
 		spin_lock_irq(&mapping->tree_lock);
-		err = radix_tree_insert(&mapping->page_tree, index, entry);
+
+		if (pmd_downgrade) {
+			radix_tree_delete(&mapping->page_tree, index);
+			mapping->nrexceptional--;
+			dax_wake_mapping_entry_waiter(mapping, index, entry,
+					true);
+		}
+
+		entry = dax_radix_locked_entry(0, size_flag | RADIX_DAX_EMPTY);
+
+		err = __radix_tree_insert(&mapping->page_tree, index,
+				dax_radix_order(entry), entry);
 		radix_tree_preload_end();
 		if (err) {
 			spin_unlock_irq(&mapping->tree_lock);
-			/* Someone already created the entry? */
-			if (err == -EEXIST)
+			/*
+			 * Someone already created the entry?  This is a
+			 * normal failure when inserting PMDs in a range
+			 * that already contains PTEs.  In that case we want
+			 * to return -EEXIST immediately.
+			 */
+			if (err == -EEXIST && !(size_flag & RADIX_DAX_PMD))
 				goto restart;
+			/*
+			 * Our insertion of a DAX PMD entry failed, most
+			 * likely because it collided with a PTE sized entry
+			 * at a different index in the PMD range.  We haven't
+			 * inserted anything into the radix tree and have no
+			 * waiters to wake.
+			 */
 			return ERR_PTR(err);
 		}
 		/* Good, we have inserted empty locked entry into the tree. */
@@ -466,6 +566,7 @@ restart:
 		return page;
 	}
 	entry = lock_slot(mapping, slot);
+ out_unlock:
 	spin_unlock_irq(&mapping->tree_lock);
 	return entry;
 }
@@ -473,9 +574,9 @@ restart:
 /*
  * We do not necessarily hold the mapping->tree_lock when we call this
  * function so it is possible that 'entry' is no longer a valid item in the
- * radix tree.  This is okay, though, because all we really need to do is to
- * find the correct waitqueue where tasks might be sleeping waiting for that
- * old 'entry' and wake them.
+ * radix tree.  This is okay because all we really need to do is to find the
+ * correct waitqueue where tasks might be waiting for that old 'entry' and
+ * wake them.
  */
 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 		pgoff_t index, void *entry, bool wake_all)
@@ -588,11 +689,17 @@ static int copy_user_dax(struct block_device *bdev, sector_t sector, size_t size
 	return 0;
 }
 
-#define DAX_PMD_INDEX(page_index) (page_index & (PMD_MASK >> PAGE_SHIFT))
-
+/*
+ * By this point grab_mapping_entry() has ensured that we have a locked entry
+ * of the appropriate size so we don't have to worry about downgrading PMDs to
+ * PTEs.  If we happen to be trying to insert a PTE and there is a PMD
+ * already in the tree, we will skip the insertion and just dirty the PMD as
+ * appropriate.
+ */
 static void *dax_insert_mapping_entry(struct address_space *mapping,
 				      struct vm_fault *vmf,
-				      void *entry, sector_t sector)
+				      void *entry, sector_t sector,
+				      unsigned long flags)
 {
 	struct radix_tree_root *page_tree = &mapping->page_tree;
 	int error = 0;
@@ -615,22 +722,35 @@ static void *dax_insert_mapping_entry(struct address_space *mapping,
 		error = radix_tree_preload(vmf->gfp_mask & ~__GFP_HIGHMEM);
 		if (error)
 			return ERR_PTR(error);
+	} else if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_HZP)) {
+		/* replacing huge zero page with PMD block mapping */
+		unmap_mapping_range(mapping,
+			(vmf->pgoff << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
 	}
 
 	spin_lock_irq(&mapping->tree_lock);
-	new_entry = (void *)((unsigned long)RADIX_DAX_ENTRY(sector, false) |
-		       RADIX_DAX_ENTRY_LOCK);
+	new_entry = dax_radix_locked_entry(sector, flags);
+
 	if (hole_fill) {
 		__delete_from_page_cache(entry, NULL);
 		/* Drop pagecache reference */
 		put_page(entry);
-		error = radix_tree_insert(page_tree, index, new_entry);
+		error = __radix_tree_insert(page_tree, index,
+				dax_radix_order(new_entry), new_entry);
 		if (error) {
 			new_entry = ERR_PTR(error);
 			goto unlock;
 		}
 		mapping->nrexceptional++;
-	} else {
+	} else if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
+		/*
+		 * Only swap our new entry into the radix tree if the current
+		 * entry is a zero page or an empty entry.  If a normal PTE or
+		 * PMD entry is already in the tree, we leave it alone.  This
+		 * means that if we are trying to insert a PTE and the
+		 * existing entry is a PMD, we will just leave the PMD in the
+		 * tree and dirty it if necessary.
+		 */
 		void **slot;
 		void *ret;
 
@@ -660,7 +780,6 @@ static int dax_writeback_one(struct block_device *bdev,
 		struct address_space *mapping, pgoff_t index, void *entry)
 {
 	struct radix_tree_root *page_tree = &mapping->page_tree;
-	int type = RADIX_DAX_TYPE(entry);
 	struct radix_tree_node *node;
 	struct blk_dax_ctl dax;
 	void **slot;
@@ -681,13 +800,21 @@ static int dax_writeback_one(struct block_device *bdev,
 	if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
 		goto unlock;
 
-	if (WARN_ON_ONCE(type != RADIX_DAX_PTE && type != RADIX_DAX_PMD)) {
+	if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
+				dax_is_zero_entry(entry))) {
 		ret = -EIO;
 		goto unlock;
 	}
 
-	dax.sector = RADIX_DAX_SECTOR(entry);
-	dax.size = (type == RADIX_DAX_PMD ? PMD_SIZE : PAGE_SIZE);
+	/*
+	 * Even if dax_writeback_mapping_range() was given a wbc->range_start
+	 * in the middle of a PMD, the 'index' we are given will be aligned to
+	 * the start index of the PMD, as will the sector we pull from
+	 * 'entry'.  This allows us to flush for PMD_SIZE and not have to
+	 * worry about partial PMD writebacks.
+	 */
+	dax.sector = dax_radix_sector(entry);
+	dax.size = PAGE_SIZE << dax_radix_order(entry);
 	spin_unlock_irq(&mapping->tree_lock);
 
 	/*
@@ -726,12 +853,11 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 		struct block_device *bdev, struct writeback_control *wbc)
 {
 	struct inode *inode = mapping->host;
-	pgoff_t start_index, end_index, pmd_index;
+	pgoff_t start_index, end_index;
 	pgoff_t indices[PAGEVEC_SIZE];
 	struct pagevec pvec;
 	bool done = false;
 	int i, ret = 0;
-	void *entry;
 
 	if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
 		return -EIO;
@@ -741,15 +867,6 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 
 	start_index = wbc->range_start >> PAGE_SHIFT;
 	end_index = wbc->range_end >> PAGE_SHIFT;
-	pmd_index = DAX_PMD_INDEX(start_index);
-
-	rcu_read_lock();
-	entry = radix_tree_lookup(&mapping->page_tree, pmd_index);
-	rcu_read_unlock();
-
-	/* see if the start of our range is covered by a PMD entry */
-	if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
-		start_index = pmd_index;
 
 	tag_pages_for_writeback(mapping, start_index, end_index);
 
@@ -794,7 +911,7 @@ static int dax_insert_mapping(struct address_space *mapping,
 		return PTR_ERR(dax.addr);
 	dax_unmap_atomic(bdev, &dax);
 
-	ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector);
+	ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector, 0);
 	if (IS_ERR(ret))
 		return PTR_ERR(ret);
 	*entryp = ret;
@@ -841,7 +958,7 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	bh.b_bdev = inode->i_sb->s_bdev;
 	bh.b_size = PAGE_SIZE;
 
-	entry = grab_mapping_entry(mapping, vmf->pgoff);
+	entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
 	if (IS_ERR(entry)) {
 		error = PTR_ERR(entry);
 		goto out;
@@ -1162,7 +1279,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	if (pos >= i_size_read(inode))
 		return VM_FAULT_SIGBUS;
 
-	entry = grab_mapping_entry(mapping, vmf->pgoff);
+	entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
 	if (IS_ERR(entry)) {
 		error = PTR_ERR(entry);
 		goto out;
@@ -1264,4 +1381,191 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	return VM_FAULT_NOPAGE | major;
 }
 EXPORT_SYMBOL_GPL(dax_iomap_fault);
+
+#ifdef CONFIG_FS_DAX_PMD
+/*
+ * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
+ * more often than one might expect in the below functions.
+ */
+#define PG_PMD_COLOUR	((PMD_SIZE >> PAGE_SHIFT) - 1)
+
+static int dax_pmd_insert_mapping(struct vm_area_struct *vma, pmd_t *pmd,
+		struct vm_fault *vmf, unsigned long address,
+		struct iomap *iomap, loff_t pos, bool write, void **entryp)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	struct block_device *bdev = iomap->bdev;
+	struct blk_dax_ctl dax = {
+		.sector = dax_iomap_sector(iomap, pos),
+		.size = PMD_SIZE,
+	};
+	long length = dax_map_atomic(bdev, &dax);
+	void *ret;
+
+	if (length < 0) /* dax_map_atomic() failed */
+		return VM_FAULT_FALLBACK;
+	if (length < PMD_SIZE)
+		goto unmap_fallback;
+	if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR)
+		goto unmap_fallback;
+	if (!pfn_t_devmap(dax.pfn))
+		goto unmap_fallback;
+
+	dax_unmap_atomic(bdev, &dax);
+
+	ret = dax_insert_mapping_entry(mapping, vmf, *entryp, dax.sector,
+			RADIX_DAX_PMD);
+	if (IS_ERR(ret))
+		return VM_FAULT_FALLBACK;
+	*entryp = ret;
+
+	return vmf_insert_pfn_pmd(vma, address, pmd, dax.pfn, write);
+
+ unmap_fallback:
+	dax_unmap_atomic(bdev, &dax);
+	return VM_FAULT_FALLBACK;
+}
+
+static int dax_pmd_load_hole(struct vm_area_struct *vma, pmd_t *pmd,
+		struct vm_fault *vmf, unsigned long address,
+		struct iomap *iomap, void **entryp)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	unsigned long pmd_addr = address & PMD_MASK;
+	struct page *zero_page;
+	spinlock_t *ptl;
+	pmd_t pmd_entry;
+	void *ret;
+
+	zero_page = get_huge_zero_page();
+
+	if (unlikely(!zero_page))
+		return VM_FAULT_FALLBACK;
+
+	ret = dax_insert_mapping_entry(mapping, vmf, *entryp, 0,
+			RADIX_DAX_PMD | RADIX_DAX_HZP);
+	if (IS_ERR(ret))
+		return VM_FAULT_FALLBACK;
+	*entryp = ret;
+
+	ptl = pmd_lock(vma->vm_mm, pmd);
+	if (!pmd_none(*pmd)) {
+		spin_unlock(ptl);
+		return VM_FAULT_FALLBACK;
+	}
+
+	pmd_entry = mk_pmd(zero_page, vma->vm_page_prot);
+	pmd_entry = pmd_mkhuge(pmd_entry);
+	set_pmd_at(vma->vm_mm, pmd_addr, pmd, pmd_entry);
+	spin_unlock(ptl);
+	return VM_FAULT_NOPAGE;
+}
+
+int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
+		pmd_t *pmd, unsigned int flags, struct iomap_ops *ops)
+{
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	unsigned long pmd_addr = address & PMD_MASK;
+	bool write = flags & FAULT_FLAG_WRITE;
+	unsigned int iomap_flags = write ? IOMAP_WRITE : 0;
+	struct inode *inode = mapping->host;
+	int result = VM_FAULT_FALLBACK;
+	struct iomap iomap = { 0 };
+	pgoff_t max_pgoff, pgoff;
+	struct vm_fault vmf;
+	void *entry;
+	loff_t pos;
+	int error;
+
+	/* Fall back to PTEs if we're going to COW */
+	if (write && !(vma->vm_flags & VM_SHARED)) {
+		split_huge_pmd(vma, pmd, address);
+		goto fallback;
+	}
+
+	/* If the PMD would extend outside the VMA */
+	if (pmd_addr < vma->vm_start)
+		goto fallback;
+	if ((pmd_addr + PMD_SIZE) > vma->vm_end)
+		goto fallback;
+
+	/*
+	 * Check whether offset isn't beyond end of file now. Caller is
+	 * supposed to hold locks serializing us with truncate / punch hole so
+	 * this is a reliable test.
+	 */
+	pgoff = linear_page_index(vma, pmd_addr);
+	max_pgoff = (i_size_read(inode) - 1) >> PAGE_SHIFT;
+
+	if (pgoff > max_pgoff)
+		return VM_FAULT_SIGBUS;
+
+	/* If the PMD would extend beyond the file size */
+	if ((pgoff | PG_PMD_COLOUR) > max_pgoff)
+		goto fallback;
+
+	/*
+	 * grab_mapping_entry() will make sure we get a 2M empty entry, a DAX
+	 * PMD or a HZP entry.  If it can't (because a 4k page is already in
+	 * the tree, for instance), it will return -EEXIST and we just fall
+	 * back to 4k entries.
+	 */
+	entry = grab_mapping_entry(mapping, pgoff, RADIX_DAX_PMD);
+	if (IS_ERR(entry))
+		goto fallback;
+
+	/*
+	 * Note that we don't use iomap_apply here.  We aren't doing I/O, only
+	 * setting up a mapping, so really we're using iomap_begin() as a way
+	 * to look up our filesystem block.
+	 */
+	pos = (loff_t)pgoff << PAGE_SHIFT;
+	error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap);
+	if (error)
+		goto unlock_entry;
+	if (iomap.offset + iomap.length < pos + PMD_SIZE)
+		goto finish_iomap;
+
+	vmf.pgoff = pgoff;
+	vmf.flags = flags;
+	vmf.gfp_mask = mapping_gfp_mask(mapping) | __GFP_IO;
+
+	switch (iomap.type) {
+	case IOMAP_MAPPED:
+		result = dax_pmd_insert_mapping(vma, pmd, &vmf, address,
+				&iomap, pos, write, &entry);
+		break;
+	case IOMAP_UNWRITTEN:
+	case IOMAP_HOLE:
+		if (WARN_ON_ONCE(write))
+			goto finish_iomap;
+		result = dax_pmd_load_hole(vma, pmd, &vmf, address, &iomap,
+				&entry);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		break;
+	}
+
+ finish_iomap:
+	if (ops->iomap_end) {
+		if (result == VM_FAULT_FALLBACK) {
+			ops->iomap_end(inode, pos, PMD_SIZE, 0, iomap_flags,
+					&iomap);
+		} else {
+			error = ops->iomap_end(inode, pos, PMD_SIZE, PMD_SIZE,
+					iomap_flags, &iomap);
+			if (error)
+				result = VM_FAULT_FALLBACK;
+		}
+	}
+ unlock_entry:
+	put_locked_mapping_entry(mapping, pgoff, entry);
+ fallback:
+	if (result == VM_FAULT_FALLBACK)
+		count_vm_event(THP_FAULT_FALLBACK);
+	return result;
+}
+EXPORT_SYMBOL_GPL(dax_iomap_pmd_fault);
+#endif /* CONFIG_FS_DAX_PMD */
 #endif /* CONFIG_FS_IOMAP */
diff --git a/include/linux/dax.h b/include/linux/dax.h
index e9ea78c..8d1a5c4 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -9,20 +9,32 @@
 struct iomap_ops;
 
 /*
- * We use lowest available bit in exceptional entry for locking, other two
- * bits to determine entry type. In total 3 special bits.
+ * We use lowest available bit in exceptional entry for locking, one bit for
+ * the entry size (PMD) and two more to tell us if the entry is a huge zero
+ * page (HZP) or an empty entry that is just used for locking.  In total four
+ * special bits.
+ *
+ * If the PMD bit isn't set the entry has size PAGE_SIZE, and if the HZP and
+ * EMPTY bits aren't set the entry is a normal DAX entry with a filesystem
+ * block allocation.
  */
-#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 3)
+#define RADIX_DAX_SHIFT	(RADIX_TREE_EXCEPTIONAL_SHIFT + 4)
 #define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
-#define RADIX_DAX_PTE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
-#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
-#define RADIX_DAX_TYPE_MASK (RADIX_DAX_PTE | RADIX_DAX_PMD)
-#define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_TYPE_MASK)
-#define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
-#define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
-		RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE) | \
-		RADIX_TREE_EXCEPTIONAL_ENTRY))
+#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
+#define RADIX_DAX_HZP (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
+#define RADIX_DAX_EMPTY (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 3))
 
+static inline unsigned long dax_radix_sector(void *entry)
+{
+	return (unsigned long)entry >> RADIX_DAX_SHIFT;
+}
+
+static inline void *dax_radix_locked_entry(sector_t sector, unsigned long flags)
+{
+	return (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY | flags |
+			((unsigned long)sector << RADIX_DAX_SHIFT) |
+			RADIX_DAX_ENTRY_LOCK);
+}
 
 ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_ops *ops);
@@ -67,6 +79,27 @@ static inline int dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
 	return VM_FAULT_FALLBACK;
 }
 
+#ifdef CONFIG_FS_DAX_PMD
+static inline unsigned int dax_radix_order(void *entry)
+{
+	if ((unsigned long)entry & RADIX_DAX_PMD)
+		return PMD_SHIFT - PAGE_SHIFT;
+	return 0;
+}
+int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
+		pmd_t *pmd, unsigned int flags, struct iomap_ops *ops);
+#else
+static inline unsigned int dax_radix_order(void *entry)
+{
+	return 0;
+}
+static inline int dax_iomap_pmd_fault(struct vm_area_struct *vma,
+		unsigned long address, pmd_t *pmd, unsigned int flags,
+		struct iomap_ops *ops)
+{
+	return VM_FAULT_FALLBACK;
+}
+#endif
 int dax_pfn_mkwrite(struct vm_area_struct *, struct vm_fault *);
 #define dax_mkwrite(vma, vmf, gb)	dax_fault(vma, vmf, gb)
 
diff --git a/mm/filemap.c b/mm/filemap.c
index a596462..592e6e9 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -611,8 +611,7 @@ static int page_cache_tree_insert(struct address_space *mapping,
 		} else {
 			/* DAX can replace empty locked entry with a hole */
 			WARN_ON_ONCE(p !=
-				(void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
-					 RADIX_DAX_ENTRY_LOCK));
+				dax_radix_locked_entry(0, RADIX_DAX_EMPTY));
 			/* DAX accounts exceptional entries as normal pages */
 			if (node)
 				workingset_node_pages_dec(node);
-- 
2.7.4


^ permalink raw reply related	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 15/17] dax: add struct iomap based DAX PMD support
  2016-10-13 15:42     ` Jan Kara
  (?)
  (?)
@ 2016-10-13 19:25       ` Ross Zwisler
  -1 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-13 19:25 UTC (permalink / raw)
  To: Jan Kara
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner, linux-nvdimm,
	linux-kernel, Christoph Hellwig, linux-xfs, linux-mm,
	Andreas Dilger, Alexander Viro, linux-fsdevel, linux-ext4,
	Andrew Morton

On Thu, Oct 13, 2016 at 05:42:24PM +0200, Jan Kara wrote:
> On Wed 12-10-16 16:50:20, Ross Zwisler wrote:
> > DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
> > locking.  This patch allows DAX PMDs to participate in the DAX radix tree
> > based locking scheme so that they can be re-enabled using the new struct
> > iomap based fault handlers.
> > 
> > There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
> > mappings that have an associated block allocation, and 4k DAX empty
> > entries.  The empty entries exist to provide locking for the duration of a
> > given page fault.
> > 
> > This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
> > entries, PMD DAX entries that have associated block allocations, and 2 MiB
> > DAX empty entries.
> > 
> > Unlike the 4k case where we insert a struct page* into the radix tree for
> > 4k zero pages, for HZP we insert a DAX exceptional entry with the new
> > RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
> > every 2MiB hole mapping, and it doesn't make sense to have that same struct
> > page* with multiple entries in multiple trees.  This would cause contention
> > on the single page lock for the one Huge Zero Page, and it would break the
> > page->index and page->mapping associations that are assumed to be valid in
> > many other places in the kernel.
> > 
> > One difficult use case is when one thread is trying to use 4k entries in
> > radix tree for a given offset, and another thread is using 2 MiB entries
> > for that same offset.  The current code handles this by making the 2 MiB
> > user fall back to 4k entries for most cases.  This was done because it is
> > the simplest solution, and because the use of 2MiB pages is already
> > opportunistic.
> > 
> > If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
> > we run into the problem of how we lock out 4k page faults for the entire
> > 2MiB range while we clean out the radix tree so we can insert the 2MiB
> > entry.  We can solve this problem if we need to, but I think that the cases
> > where both 2MiB entries and 4K entries are being used for the same range
> > will be rare enough and the gain small enough that it probably won't be
> > worth the complexity.
> > 
> > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> 
> Just one small bug below. Feel free to add:
> 
> Reviewed-by: Jan Kara <jack@suse.cz>
> 
> after fixing that.

Fixed, thank you for the catch and the review!
_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 15/17] dax: add struct iomap based DAX PMD support
@ 2016-10-13 19:25       ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-13 19:25 UTC (permalink / raw)
  To: Jan Kara
  Cc: Ross Zwisler, linux-kernel, Theodore Ts'o, Alexander Viro,
	Andreas Dilger, Andrew Morton, Christoph Hellwig, Dan Williams,
	Dave Chinner, Matthew Wilcox, linux-ext4, linux-fsdevel,
	linux-mm, linux-nvdimm, linux-xfs

On Thu, Oct 13, 2016 at 05:42:24PM +0200, Jan Kara wrote:
> On Wed 12-10-16 16:50:20, Ross Zwisler wrote:
> > DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
> > locking.  This patch allows DAX PMDs to participate in the DAX radix tree
> > based locking scheme so that they can be re-enabled using the new struct
> > iomap based fault handlers.
> > 
> > There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
> > mappings that have an associated block allocation, and 4k DAX empty
> > entries.  The empty entries exist to provide locking for the duration of a
> > given page fault.
> > 
> > This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
> > entries, PMD DAX entries that have associated block allocations, and 2 MiB
> > DAX empty entries.
> > 
> > Unlike the 4k case where we insert a struct page* into the radix tree for
> > 4k zero pages, for HZP we insert a DAX exceptional entry with the new
> > RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
> > every 2MiB hole mapping, and it doesn't make sense to have that same struct
> > page* with multiple entries in multiple trees.  This would cause contention
> > on the single page lock for the one Huge Zero Page, and it would break the
> > page->index and page->mapping associations that are assumed to be valid in
> > many other places in the kernel.
> > 
> > One difficult use case is when one thread is trying to use 4k entries in
> > radix tree for a given offset, and another thread is using 2 MiB entries
> > for that same offset.  The current code handles this by making the 2 MiB
> > user fall back to 4k entries for most cases.  This was done because it is
> > the simplest solution, and because the use of 2MiB pages is already
> > opportunistic.
> > 
> > If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
> > we run into the problem of how we lock out 4k page faults for the entire
> > 2MiB range while we clean out the radix tree so we can insert the 2MiB
> > entry.  We can solve this problem if we need to, but I think that the cases
> > where both 2MiB entries and 4K entries are being used for the same range
> > will be rare enough and the gain small enough that it probably won't be
> > worth the complexity.
> > 
> > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> 
> Just one small bug below. Feel free to add:
> 
> Reviewed-by: Jan Kara <jack@suse.cz>
> 
> after fixing that.

Fixed, thank you for the catch and the review!

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 15/17] dax: add struct iomap based DAX PMD support
@ 2016-10-13 19:25       ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-13 19:25 UTC (permalink / raw)
  To: Jan Kara
  Cc: Ross Zwisler, linux-kernel, Theodore Ts'o, Alexander Viro,
	Andreas Dilger, Andrew Morton, Christoph Hellwig, Dan Williams,
	Dave Chinner, Matthew Wilcox, linux-ext4, linux-fsdevel,
	linux-mm, linux-nvdimm, linux-xfs

On Thu, Oct 13, 2016 at 05:42:24PM +0200, Jan Kara wrote:
> On Wed 12-10-16 16:50:20, Ross Zwisler wrote:
> > DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
> > locking.  This patch allows DAX PMDs to participate in the DAX radix tree
> > based locking scheme so that they can be re-enabled using the new struct
> > iomap based fault handlers.
> > 
> > There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
> > mappings that have an associated block allocation, and 4k DAX empty
> > entries.  The empty entries exist to provide locking for the duration of a
> > given page fault.
> > 
> > This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
> > entries, PMD DAX entries that have associated block allocations, and 2 MiB
> > DAX empty entries.
> > 
> > Unlike the 4k case where we insert a struct page* into the radix tree for
> > 4k zero pages, for HZP we insert a DAX exceptional entry with the new
> > RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
> > every 2MiB hole mapping, and it doesn't make sense to have that same struct
> > page* with multiple entries in multiple trees.  This would cause contention
> > on the single page lock for the one Huge Zero Page, and it would break the
> > page->index and page->mapping associations that are assumed to be valid in
> > many other places in the kernel.
> > 
> > One difficult use case is when one thread is trying to use 4k entries in
> > radix tree for a given offset, and another thread is using 2 MiB entries
> > for that same offset.  The current code handles this by making the 2 MiB
> > user fall back to 4k entries for most cases.  This was done because it is
> > the simplest solution, and because the use of 2MiB pages is already
> > opportunistic.
> > 
> > If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
> > we run into the problem of how we lock out 4k page faults for the entire
> > 2MiB range while we clean out the radix tree so we can insert the 2MiB
> > entry.  We can solve this problem if we need to, but I think that the cases
> > where both 2MiB entries and 4K entries are being used for the same range
> > will be rare enough and the gain small enough that it probably won't be
> > worth the complexity.
> > 
> > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> 
> Just one small bug below. Feel free to add:
> 
> Reviewed-by: Jan Kara <jack@suse.cz>
> 
> after fixing that.

Fixed, thank you for the catch and the review!

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
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^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 15/17] dax: add struct iomap based DAX PMD support
@ 2016-10-13 19:25       ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-13 19:25 UTC (permalink / raw)
  To: Jan Kara
  Cc: Ross Zwisler, linux-kernel, Theodore Ts'o, Alexander Viro,
	Andreas Dilger, Andrew Morton, Christoph Hellwig, Dan Williams,
	Dave Chinner, Matthew Wilcox, linux-ext4, linux-fsdevel,
	linux-mm, linux-nvdimm, linux-xfs

On Thu, Oct 13, 2016 at 05:42:24PM +0200, Jan Kara wrote:
> On Wed 12-10-16 16:50:20, Ross Zwisler wrote:
> > DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
> > locking.  This patch allows DAX PMDs to participate in the DAX radix tree
> > based locking scheme so that they can be re-enabled using the new struct
> > iomap based fault handlers.
> > 
> > There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
> > mappings that have an associated block allocation, and 4k DAX empty
> > entries.  The empty entries exist to provide locking for the duration of a
> > given page fault.
> > 
> > This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
> > entries, PMD DAX entries that have associated block allocations, and 2 MiB
> > DAX empty entries.
> > 
> > Unlike the 4k case where we insert a struct page* into the radix tree for
> > 4k zero pages, for HZP we insert a DAX exceptional entry with the new
> > RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
> > every 2MiB hole mapping, and it doesn't make sense to have that same struct
> > page* with multiple entries in multiple trees.  This would cause contention
> > on the single page lock for the one Huge Zero Page, and it would break the
> > page->index and page->mapping associations that are assumed to be valid in
> > many other places in the kernel.
> > 
> > One difficult use case is when one thread is trying to use 4k entries in
> > radix tree for a given offset, and another thread is using 2 MiB entries
> > for that same offset.  The current code handles this by making the 2 MiB
> > user fall back to 4k entries for most cases.  This was done because it is
> > the simplest solution, and because the use of 2MiB pages is already
> > opportunistic.
> > 
> > If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
> > we run into the problem of how we lock out 4k page faults for the entire
> > 2MiB range while we clean out the radix tree so we can insert the 2MiB
> > entry.  We can solve this problem if we need to, but I think that the cases
> > where both 2MiB entries and 4K entries are being used for the same range
> > will be rare enough and the gain small enough that it probably won't be
> > worth the complexity.
> > 
> > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> 
> Just one small bug below. Feel free to add:
> 
> Reviewed-by: Jan Kara <jack@suse.cz>
> 
> after fixing that.

Fixed, thank you for the catch and the review!

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD
  2016-10-12 22:50   ` Ross Zwisler
                       ` (3 preceding siblings ...)
  (?)
@ 2016-10-17  5:57     ` Aneesh Kumar K.V
  -1 siblings, 0 replies; 126+ messages in thread
From: Aneesh Kumar K.V @ 2016-10-17  5:57 UTC (permalink / raw)
  To: Ross Zwisler, linux-kernel
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner, linux-nvdimm,
	Christoph Hellwig, linux-xfs, linux-mm, Andreas Dilger,
	Alexander Viro, linux-fsdevel, Jan Kara, linux-ext4,
	Andrew Morton

Ross Zwisler <ross.zwisler@linux.intel.com> writes:

> Now that DAX PMD faults are once again working and are now participating in
> DAX's radix tree locking scheme, allow their config option to be enabled.
>
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> ---
>  fs/Kconfig | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 2bc7ad7..b6f0fce 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -55,7 +55,6 @@ config FS_DAX_PMD
>  	depends on FS_DAX
>  	depends on ZONE_DEVICE
>  	depends on TRANSPARENT_HUGEPAGE
> -	depends on BROKEN
>  
>  endif # BLOCK


This series made dax_pmd_fault return VM_FAULT_FALLBACK in [PATCH v6 09/17] dax: remove dax_pmd_fault(). 
That essentially disable dax pmd for ext4. Any plans to fix that ?

-aneesh

_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD
@ 2016-10-17  5:57     ` Aneesh Kumar K.V
  0 siblings, 0 replies; 126+ messages in thread
From: Aneesh Kumar K.V @ 2016-10-17  5:57 UTC (permalink / raw)
  To: Ross Zwisler, linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

Ross Zwisler <ross.zwisler@linux.intel.com> writes:

> Now that DAX PMD faults are once again working and are now participating in
> DAX's radix tree locking scheme, allow their config option to be enabled.
>
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> ---
>  fs/Kconfig | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 2bc7ad7..b6f0fce 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -55,7 +55,6 @@ config FS_DAX_PMD
>  	depends on FS_DAX
>  	depends on ZONE_DEVICE
>  	depends on TRANSPARENT_HUGEPAGE
> -	depends on BROKEN
>  
>  endif # BLOCK


This series made dax_pmd_fault return VM_FAULT_FALLBACK in [PATCH v6 09/17] dax: remove dax_pmd_fault(). 
That essentially disable dax pmd for ext4. Any plans to fix that ?

-aneesh

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD
@ 2016-10-17  5:57     ` Aneesh Kumar K.V
  0 siblings, 0 replies; 126+ messages in thread
From: Aneesh Kumar K.V @ 2016-10-17  5:57 UTC (permalink / raw)
  To: Ross Zwisler, linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

Ross Zwisler <ross.zwisler@linux.intel.com> writes:

> Now that DAX PMD faults are once again working and are now participating in
> DAX's radix tree locking scheme, allow their config option to be enabled.
>
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> ---
>  fs/Kconfig | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 2bc7ad7..b6f0fce 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -55,7 +55,6 @@ config FS_DAX_PMD
>  	depends on FS_DAX
>  	depends on ZONE_DEVICE
>  	depends on TRANSPARENT_HUGEPAGE
> -	depends on BROKEN
>  
>  endif # BLOCK


This series made dax_pmd_fault return VM_FAULT_FALLBACK in [PATCH v6 09/17] dax: remove dax_pmd_fault(). 
That essentially disable dax pmd for ext4. Any plans to fix that ?

-aneesh

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD
@ 2016-10-17  5:57     ` Aneesh Kumar K.V
  0 siblings, 0 replies; 126+ messages in thread
From: Aneesh Kumar K.V @ 2016-10-17  5:57 UTC (permalink / raw)
  To: Ross Zwisler, linux-kernel-u79uwXL29TY76Z2rM5mHXA
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner,
	linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw, Christoph Hellwig,
	linux-xfs-u79uwXL29TY76Z2rM5mHXA,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg, Andreas Dilger, Alexander Viro,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA, Jan Kara,
	linux-ext4-u79uwXL29TY76Z2rM5mHXA, Andrew Morton

Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org> writes:

> Now that DAX PMD faults are once again working and are now participating in
> DAX's radix tree locking scheme, allow their config option to be enabled.
>
> Signed-off-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
> ---
>  fs/Kconfig | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 2bc7ad7..b6f0fce 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -55,7 +55,6 @@ config FS_DAX_PMD
>  	depends on FS_DAX
>  	depends on ZONE_DEVICE
>  	depends on TRANSPARENT_HUGEPAGE
> -	depends on BROKEN
>  
>  endif # BLOCK


This series made dax_pmd_fault return VM_FAULT_FALLBACK in [PATCH v6 09/17] dax: remove dax_pmd_fault(). 
That essentially disable dax pmd for ext4. Any plans to fix that ?

-aneesh

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD
@ 2016-10-17  5:57     ` Aneesh Kumar K.V
  0 siblings, 0 replies; 126+ messages in thread
From: Aneesh Kumar K.V @ 2016-10-17  5:57 UTC (permalink / raw)
  To: Ross Zwisler, linux-kernel
  Cc: Theodore Ts'o, Alexander Viro, Andreas Dilger, Andrew Morton,
	Christoph Hellwig, Dan Williams, Dave Chinner, Jan Kara,
	Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

Ross Zwisler <ross.zwisler@linux.intel.com> writes:

> Now that DAX PMD faults are once again working and are now participating in
> DAX's radix tree locking scheme, allow their config option to be enabled.
>
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> ---
>  fs/Kconfig | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 2bc7ad7..b6f0fce 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -55,7 +55,6 @@ config FS_DAX_PMD
>  	depends on FS_DAX
>  	depends on ZONE_DEVICE
>  	depends on TRANSPARENT_HUGEPAGE
> -	depends on BROKEN
>  
>  endif # BLOCK


This series made dax_pmd_fault return VM_FAULT_FALLBACK in [PATCH v6 09/17] dax: remove dax_pmd_fault(). 
That essentially disable dax pmd for ext4. Any plans to fix that ?

-aneesh


^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD
@ 2016-10-17  5:57     ` Aneesh Kumar K.V
  0 siblings, 0 replies; 126+ messages in thread
From: Aneesh Kumar K.V @ 2016-10-17  5:57 UTC (permalink / raw)
  To: Ross Zwisler, linux-kernel
  Cc: Theodore Ts'o, Alexander Viro, Andreas Dilger, Andrew Morton,
	Christoph Hellwig, Dan Williams, Dave Chinner, Jan Kara,
	Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

Ross Zwisler <ross.zwisler@linux.intel.com> writes:

> Now that DAX PMD faults are once again working and are now participating in
> DAX's radix tree locking scheme, allow their config option to be enabled.
>
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> ---
>  fs/Kconfig | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 2bc7ad7..b6f0fce 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -55,7 +55,6 @@ config FS_DAX_PMD
>  	depends on FS_DAX
>  	depends on ZONE_DEVICE
>  	depends on TRANSPARENT_HUGEPAGE
> -	depends on BROKEN
>  
>  endif # BLOCK


This series made dax_pmd_fault return VM_FAULT_FALLBACK in [PATCH v6 09/17] dax: remove dax_pmd_fault(). 
That essentially disable dax pmd for ext4. Any plans to fix that ?

-aneesh

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v7 15/17] dax: add struct iomap based DAX PMD support
  2016-10-13 19:23       ` Ross Zwisler
                           ` (2 preceding siblings ...)
  (?)
@ 2016-10-17  6:06         ` Aneesh Kumar K.V
  -1 siblings, 0 replies; 126+ messages in thread
From: Aneesh Kumar K.V @ 2016-10-17  6:06 UTC (permalink / raw)
  To: Ross Zwisler, linux-kernel
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner, linux-nvdimm,
	Christoph Hellwig, linux-xfs, linux-mm, Andreas Dilger,
	Alexander Viro, linux-fsdevel, Jan Kara, linux-ext4,
	Andrew Morton

Ross Zwisler <ross.zwisler@linux.intel.com> writes:

> DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
> locking.  This patch allows DAX PMDs to participate in the DAX radix tree
> based locking scheme so that they can be re-enabled using the new struct
> iomap based fault handlers.
>
> There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
> mappings that have an associated block allocation, and 4k DAX empty
> entries.  The empty entries exist to provide locking for the duration of a
> given page fault.
>
> This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
> entries, PMD DAX entries that have associated block allocations, and 2 MiB
> DAX empty entries.
>
> Unlike the 4k case where we insert a struct page* into the radix tree for
> 4k zero pages, for HZP we insert a DAX exceptional entry with the new
> RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
> every 2MiB hole mapping, and it doesn't make sense to have that same struct
> page* with multiple entries in multiple trees.  This would cause contention
> on the single page lock for the one Huge Zero Page, and it would break the
> page->index and page->mapping associations that are assumed to be valid in
> many other places in the kernel.
>
> One difficult use case is when one thread is trying to use 4k entries in
> radix tree for a given offset, and another thread is using 2 MiB entries
> for that same offset.  The current code handles this by making the 2 MiB
> user fall back to 4k entries for most cases.  This was done because it is
> the simplest solution, and because the use of 2MiB pages is already
> opportunistic.
>
> If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
> we run into the problem of how we lock out 4k page faults for the entire
> 2MiB range while we clean out the radix tree so we can insert the 2MiB
> entry.  We can solve this problem if we need to, but I think that the cases
> where both 2MiB entries and 4K entries are being used for the same range
> will be rare enough and the gain small enough that it probably won't be
> worth the complexity.
>
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> Reviewed-by: Jan Kara <jack@suse.cz>
> ---
>  fs/dax.c            | 378 +++++++++++++++++++++++++++++++++++++++++++++++-----
>  include/linux/dax.h |  55 ++++++--
>  mm/filemap.c        |   3 +-
>  3 files changed, 386 insertions(+), 50 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 0582c7c..153cfd5 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -76,6 +76,26 @@ static void dax_unmap_atomic(struct block_device *bdev,
>  	blk_queue_exit(bdev->bd_queue);
>  }
>  
> +static int dax_is_pmd_entry(void *entry)
> +{
> +	return (unsigned long)entry & RADIX_DAX_PMD;
> +}
> +
> +static int dax_is_pte_entry(void *entry)
> +{
> +	return !((unsigned long)entry & RADIX_DAX_PMD);
> +}
> +
> +static int dax_is_zero_entry(void *entry)
> +{
> +	return (unsigned long)entry & RADIX_DAX_HZP;
> +}

How about dax_is_pmd_zero_entry() ?


> +
> +static int dax_is_empty_entry(void *entry)
> +{
> +	return (unsigned long)entry & RADIX_DAX_EMPTY;
> +}
> +

-aneesh

_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v7 15/17] dax: add struct iomap based DAX PMD support
@ 2016-10-17  6:06         ` Aneesh Kumar K.V
  0 siblings, 0 replies; 126+ messages in thread
From: Aneesh Kumar K.V @ 2016-10-17  6:06 UTC (permalink / raw)
  To: Ross Zwisler, linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

Ross Zwisler <ross.zwisler@linux.intel.com> writes:

> DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
> locking.  This patch allows DAX PMDs to participate in the DAX radix tree
> based locking scheme so that they can be re-enabled using the new struct
> iomap based fault handlers.
>
> There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
> mappings that have an associated block allocation, and 4k DAX empty
> entries.  The empty entries exist to provide locking for the duration of a
> given page fault.
>
> This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
> entries, PMD DAX entries that have associated block allocations, and 2 MiB
> DAX empty entries.
>
> Unlike the 4k case where we insert a struct page* into the radix tree for
> 4k zero pages, for HZP we insert a DAX exceptional entry with the new
> RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
> every 2MiB hole mapping, and it doesn't make sense to have that same struct
> page* with multiple entries in multiple trees.  This would cause contention
> on the single page lock for the one Huge Zero Page, and it would break the
> page->index and page->mapping associations that are assumed to be valid in
> many other places in the kernel.
>
> One difficult use case is when one thread is trying to use 4k entries in
> radix tree for a given offset, and another thread is using 2 MiB entries
> for that same offset.  The current code handles this by making the 2 MiB
> user fall back to 4k entries for most cases.  This was done because it is
> the simplest solution, and because the use of 2MiB pages is already
> opportunistic.
>
> If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
> we run into the problem of how we lock out 4k page faults for the entire
> 2MiB range while we clean out the radix tree so we can insert the 2MiB
> entry.  We can solve this problem if we need to, but I think that the cases
> where both 2MiB entries and 4K entries are being used for the same range
> will be rare enough and the gain small enough that it probably won't be
> worth the complexity.
>
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> Reviewed-by: Jan Kara <jack@suse.cz>
> ---
>  fs/dax.c            | 378 +++++++++++++++++++++++++++++++++++++++++++++++-----
>  include/linux/dax.h |  55 ++++++--
>  mm/filemap.c        |   3 +-
>  3 files changed, 386 insertions(+), 50 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 0582c7c..153cfd5 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -76,6 +76,26 @@ static void dax_unmap_atomic(struct block_device *bdev,
>  	blk_queue_exit(bdev->bd_queue);
>  }
>  
> +static int dax_is_pmd_entry(void *entry)
> +{
> +	return (unsigned long)entry & RADIX_DAX_PMD;
> +}
> +
> +static int dax_is_pte_entry(void *entry)
> +{
> +	return !((unsigned long)entry & RADIX_DAX_PMD);
> +}
> +
> +static int dax_is_zero_entry(void *entry)
> +{
> +	return (unsigned long)entry & RADIX_DAX_HZP;
> +}

How about dax_is_pmd_zero_entry() ?


> +
> +static int dax_is_empty_entry(void *entry)
> +{
> +	return (unsigned long)entry & RADIX_DAX_EMPTY;
> +}
> +

-aneesh

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v7 15/17] dax: add struct iomap based DAX PMD support
@ 2016-10-17  6:06         ` Aneesh Kumar K.V
  0 siblings, 0 replies; 126+ messages in thread
From: Aneesh Kumar K.V @ 2016-10-17  6:06 UTC (permalink / raw)
  To: Ross Zwisler, linux-kernel
  Cc: Ross Zwisler, Theodore Ts'o, Alexander Viro, Andreas Dilger,
	Andrew Morton, Christoph Hellwig, Dan Williams, Dave Chinner,
	Jan Kara, Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

Ross Zwisler <ross.zwisler@linux.intel.com> writes:

> DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
> locking.  This patch allows DAX PMDs to participate in the DAX radix tree
> based locking scheme so that they can be re-enabled using the new struct
> iomap based fault handlers.
>
> There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
> mappings that have an associated block allocation, and 4k DAX empty
> entries.  The empty entries exist to provide locking for the duration of a
> given page fault.
>
> This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
> entries, PMD DAX entries that have associated block allocations, and 2 MiB
> DAX empty entries.
>
> Unlike the 4k case where we insert a struct page* into the radix tree for
> 4k zero pages, for HZP we insert a DAX exceptional entry with the new
> RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
> every 2MiB hole mapping, and it doesn't make sense to have that same struct
> page* with multiple entries in multiple trees.  This would cause contention
> on the single page lock for the one Huge Zero Page, and it would break the
> page->index and page->mapping associations that are assumed to be valid in
> many other places in the kernel.
>
> One difficult use case is when one thread is trying to use 4k entries in
> radix tree for a given offset, and another thread is using 2 MiB entries
> for that same offset.  The current code handles this by making the 2 MiB
> user fall back to 4k entries for most cases.  This was done because it is
> the simplest solution, and because the use of 2MiB pages is already
> opportunistic.
>
> If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
> we run into the problem of how we lock out 4k page faults for the entire
> 2MiB range while we clean out the radix tree so we can insert the 2MiB
> entry.  We can solve this problem if we need to, but I think that the cases
> where both 2MiB entries and 4K entries are being used for the same range
> will be rare enough and the gain small enough that it probably won't be
> worth the complexity.
>
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> Reviewed-by: Jan Kara <jack@suse.cz>
> ---
>  fs/dax.c            | 378 +++++++++++++++++++++++++++++++++++++++++++++++-----
>  include/linux/dax.h |  55 ++++++--
>  mm/filemap.c        |   3 +-
>  3 files changed, 386 insertions(+), 50 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 0582c7c..153cfd5 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -76,6 +76,26 @@ static void dax_unmap_atomic(struct block_device *bdev,
>  	blk_queue_exit(bdev->bd_queue);
>  }
>  
> +static int dax_is_pmd_entry(void *entry)
> +{
> +	return (unsigned long)entry & RADIX_DAX_PMD;
> +}
> +
> +static int dax_is_pte_entry(void *entry)
> +{
> +	return !((unsigned long)entry & RADIX_DAX_PMD);
> +}
> +
> +static int dax_is_zero_entry(void *entry)
> +{
> +	return (unsigned long)entry & RADIX_DAX_HZP;
> +}

How about dax_is_pmd_zero_entry() ?


> +
> +static int dax_is_empty_entry(void *entry)
> +{
> +	return (unsigned long)entry & RADIX_DAX_EMPTY;
> +}
> +

-aneesh

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v7 15/17] dax: add struct iomap based DAX PMD support
@ 2016-10-17  6:06         ` Aneesh Kumar K.V
  0 siblings, 0 replies; 126+ messages in thread
From: Aneesh Kumar K.V @ 2016-10-17  6:06 UTC (permalink / raw)
  To: Ross Zwisler, linux-kernel
  Cc: Theodore Ts'o, Alexander Viro, Andreas Dilger, Andrew Morton,
	Christoph Hellwig, Dan Williams, Dave Chinner, Jan Kara,
	Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

Ross Zwisler <ross.zwisler@linux.intel.com> writes:

> DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
> locking.  This patch allows DAX PMDs to participate in the DAX radix tree
> based locking scheme so that they can be re-enabled using the new struct
> iomap based fault handlers.
>
> There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
> mappings that have an associated block allocation, and 4k DAX empty
> entries.  The empty entries exist to provide locking for the duration of a
> given page fault.
>
> This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
> entries, PMD DAX entries that have associated block allocations, and 2 MiB
> DAX empty entries.
>
> Unlike the 4k case where we insert a struct page* into the radix tree for
> 4k zero pages, for HZP we insert a DAX exceptional entry with the new
> RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
> every 2MiB hole mapping, and it doesn't make sense to have that same struct
> page* with multiple entries in multiple trees.  This would cause contention
> on the single page lock for the one Huge Zero Page, and it would break the
> page->index and page->mapping associations that are assumed to be valid in
> many other places in the kernel.
>
> One difficult use case is when one thread is trying to use 4k entries in
> radix tree for a given offset, and another thread is using 2 MiB entries
> for that same offset.  The current code handles this by making the 2 MiB
> user fall back to 4k entries for most cases.  This was done because it is
> the simplest solution, and because the use of 2MiB pages is already
> opportunistic.
>
> If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
> we run into the problem of how we lock out 4k page faults for the entire
> 2MiB range while we clean out the radix tree so we can insert the 2MiB
> entry.  We can solve this problem if we need to, but I think that the cases
> where both 2MiB entries and 4K entries are being used for the same range
> will be rare enough and the gain small enough that it probably won't be
> worth the complexity.
>
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> Reviewed-by: Jan Kara <jack@suse.cz>
> ---
>  fs/dax.c            | 378 +++++++++++++++++++++++++++++++++++++++++++++++-----
>  include/linux/dax.h |  55 ++++++--
>  mm/filemap.c        |   3 +-
>  3 files changed, 386 insertions(+), 50 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 0582c7c..153cfd5 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -76,6 +76,26 @@ static void dax_unmap_atomic(struct block_device *bdev,
>  	blk_queue_exit(bdev->bd_queue);
>  }
>  
> +static int dax_is_pmd_entry(void *entry)
> +{
> +	return (unsigned long)entry & RADIX_DAX_PMD;
> +}
> +
> +static int dax_is_pte_entry(void *entry)
> +{
> +	return !((unsigned long)entry & RADIX_DAX_PMD);
> +}
> +
> +static int dax_is_zero_entry(void *entry)
> +{
> +	return (unsigned long)entry & RADIX_DAX_HZP;
> +}

How about dax_is_pmd_zero_entry() ?


> +
> +static int dax_is_empty_entry(void *entry)
> +{
> +	return (unsigned long)entry & RADIX_DAX_EMPTY;
> +}
> +

-aneesh


^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v7 15/17] dax: add struct iomap based DAX PMD support
@ 2016-10-17  6:06         ` Aneesh Kumar K.V
  0 siblings, 0 replies; 126+ messages in thread
From: Aneesh Kumar K.V @ 2016-10-17  6:06 UTC (permalink / raw)
  To: Ross Zwisler, linux-kernel
  Cc: Theodore Ts'o, Alexander Viro, Andreas Dilger, Andrew Morton,
	Christoph Hellwig, Dan Williams, Dave Chinner, Jan Kara,
	Matthew Wilcox, linux-ext4, linux-fsdevel, linux-mm,
	linux-nvdimm, linux-xfs

Ross Zwisler <ross.zwisler@linux.intel.com> writes:

> DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
> locking.  This patch allows DAX PMDs to participate in the DAX radix tree
> based locking scheme so that they can be re-enabled using the new struct
> iomap based fault handlers.
>
> There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
> mappings that have an associated block allocation, and 4k DAX empty
> entries.  The empty entries exist to provide locking for the duration of a
> given page fault.
>
> This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
> entries, PMD DAX entries that have associated block allocations, and 2 MiB
> DAX empty entries.
>
> Unlike the 4k case where we insert a struct page* into the radix tree for
> 4k zero pages, for HZP we insert a DAX exceptional entry with the new
> RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
> every 2MiB hole mapping, and it doesn't make sense to have that same struct
> page* with multiple entries in multiple trees.  This would cause contention
> on the single page lock for the one Huge Zero Page, and it would break the
> page->index and page->mapping associations that are assumed to be valid in
> many other places in the kernel.
>
> One difficult use case is when one thread is trying to use 4k entries in
> radix tree for a given offset, and another thread is using 2 MiB entries
> for that same offset.  The current code handles this by making the 2 MiB
> user fall back to 4k entries for most cases.  This was done because it is
> the simplest solution, and because the use of 2MiB pages is already
> opportunistic.
>
> If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
> we run into the problem of how we lock out 4k page faults for the entire
> 2MiB range while we clean out the radix tree so we can insert the 2MiB
> entry.  We can solve this problem if we need to, but I think that the cases
> where both 2MiB entries and 4K entries are being used for the same range
> will be rare enough and the gain small enough that it probably won't be
> worth the complexity.
>
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> Reviewed-by: Jan Kara <jack@suse.cz>
> ---
>  fs/dax.c            | 378 +++++++++++++++++++++++++++++++++++++++++++++++-----
>  include/linux/dax.h |  55 ++++++--
>  mm/filemap.c        |   3 +-
>  3 files changed, 386 insertions(+), 50 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 0582c7c..153cfd5 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -76,6 +76,26 @@ static void dax_unmap_atomic(struct block_device *bdev,
>  	blk_queue_exit(bdev->bd_queue);
>  }
>  
> +static int dax_is_pmd_entry(void *entry)
> +{
> +	return (unsigned long)entry & RADIX_DAX_PMD;
> +}
> +
> +static int dax_is_pte_entry(void *entry)
> +{
> +	return !((unsigned long)entry & RADIX_DAX_PMD);
> +}
> +
> +static int dax_is_zero_entry(void *entry)
> +{
> +	return (unsigned long)entry & RADIX_DAX_HZP;
> +}

How about dax_is_pmd_zero_entry() ?


> +
> +static int dax_is_empty_entry(void *entry)
> +{
> +	return (unsigned long)entry & RADIX_DAX_EMPTY;
> +}
> +

-aneesh

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD
  2016-10-17  5:57     ` Aneesh Kumar K.V
  (?)
  (?)
@ 2016-10-17  9:09       ` Jan Kara
  -1 siblings, 0 replies; 126+ messages in thread
From: Jan Kara @ 2016-10-17  9:09 UTC (permalink / raw)
  To: Aneesh Kumar K.V
  Cc: Ross Zwisler, linux-kernel, Theodore Ts'o, Alexander Viro,
	Andreas Dilger, Andrew Morton, Christoph Hellwig, Dan Williams,
	Dave Chinner, Jan Kara, Matthew Wilcox, linux-ext4,
	linux-fsdevel, linux-mm, linux-nvdimm, linux-xfs

On Mon 17-10-16 11:27:24, Aneesh Kumar K.V wrote:
> Ross Zwisler <ross.zwisler@linux.intel.com> writes:
> 
> > Now that DAX PMD faults are once again working and are now participating in
> > DAX's radix tree locking scheme, allow their config option to be enabled.
> >
> > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> > ---
> >  fs/Kconfig | 1 -
> >  1 file changed, 1 deletion(-)
> >
> > diff --git a/fs/Kconfig b/fs/Kconfig
> > index 2bc7ad7..b6f0fce 100644
> > --- a/fs/Kconfig
> > +++ b/fs/Kconfig
> > @@ -55,7 +55,6 @@ config FS_DAX_PMD
> >  	depends on FS_DAX
> >  	depends on ZONE_DEVICE
> >  	depends on TRANSPARENT_HUGEPAGE
> > -	depends on BROKEN
> >  
> >  endif # BLOCK
> 
> 
> This series made dax_pmd_fault return VM_FAULT_FALLBACK in [PATCH v6 09/17] dax: remove dax_pmd_fault(). 
> That essentially disable dax pmd for ext4. Any plans to fix that ?

I'm working on converting ext4 to the new iomap infrastructure. Once that
is done, it can use new DAX helpers for PMD faults easily.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
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^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD
@ 2016-10-17  9:09       ` Jan Kara
  0 siblings, 0 replies; 126+ messages in thread
From: Jan Kara @ 2016-10-17  9:09 UTC (permalink / raw)
  To: Aneesh Kumar K.V
  Cc: Ross Zwisler, linux-kernel, Theodore Ts'o, Alexander Viro,
	Andreas Dilger, Andrew Morton, Christoph Hellwig, Dan Williams,
	Dave Chinner, Jan Kara, Matthew Wilcox, linux-ext4,
	linux-fsdevel, linux-mm, linux-nvdimm, linux-xfs

On Mon 17-10-16 11:27:24, Aneesh Kumar K.V wrote:
> Ross Zwisler <ross.zwisler@linux.intel.com> writes:
> 
> > Now that DAX PMD faults are once again working and are now participating in
> > DAX's radix tree locking scheme, allow their config option to be enabled.
> >
> > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> > ---
> >  fs/Kconfig | 1 -
> >  1 file changed, 1 deletion(-)
> >
> > diff --git a/fs/Kconfig b/fs/Kconfig
> > index 2bc7ad7..b6f0fce 100644
> > --- a/fs/Kconfig
> > +++ b/fs/Kconfig
> > @@ -55,7 +55,6 @@ config FS_DAX_PMD
> >  	depends on FS_DAX
> >  	depends on ZONE_DEVICE
> >  	depends on TRANSPARENT_HUGEPAGE
> > -	depends on BROKEN
> >  
> >  endif # BLOCK
> 
> 
> This series made dax_pmd_fault return VM_FAULT_FALLBACK in [PATCH v6 09/17] dax: remove dax_pmd_fault(). 
> That essentially disable dax pmd for ext4. Any plans to fix that ?

I'm working on converting ext4 to the new iomap infrastructure. Once that
is done, it can use new DAX helpers for PMD faults easily.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD
@ 2016-10-17  9:09       ` Jan Kara
  0 siblings, 0 replies; 126+ messages in thread
From: Jan Kara @ 2016-10-17  9:09 UTC (permalink / raw)
  To: Aneesh Kumar K.V
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner,
	linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA, Christoph Hellwig,
	linux-xfs-u79uwXL29TY76Z2rM5mHXA,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg, Andreas Dilger, Alexander Viro,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA, Jan Kara,
	linux-ext4-u79uwXL29TY76Z2rM5mHXA, Andrew Morton

On Mon 17-10-16 11:27:24, Aneesh Kumar K.V wrote:
> Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org> writes:
> 
> > Now that DAX PMD faults are once again working and are now participating in
> > DAX's radix tree locking scheme, allow their config option to be enabled.
> >
> > Signed-off-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
> > ---
> >  fs/Kconfig | 1 -
> >  1 file changed, 1 deletion(-)
> >
> > diff --git a/fs/Kconfig b/fs/Kconfig
> > index 2bc7ad7..b6f0fce 100644
> > --- a/fs/Kconfig
> > +++ b/fs/Kconfig
> > @@ -55,7 +55,6 @@ config FS_DAX_PMD
> >  	depends on FS_DAX
> >  	depends on ZONE_DEVICE
> >  	depends on TRANSPARENT_HUGEPAGE
> > -	depends on BROKEN
> >  
> >  endif # BLOCK
> 
> 
> This series made dax_pmd_fault return VM_FAULT_FALLBACK in [PATCH v6 09/17] dax: remove dax_pmd_fault(). 
> That essentially disable dax pmd for ext4. Any plans to fix that ?

I'm working on converting ext4 to the new iomap infrastructure. Once that
is done, it can use new DAX helpers for PMD faults easily.

								Honza
-- 
Jan Kara <jack-IBi9RG/b67k@public.gmane.org>
SUSE Labs, CR

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v6 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD
@ 2016-10-17  9:09       ` Jan Kara
  0 siblings, 0 replies; 126+ messages in thread
From: Jan Kara @ 2016-10-17  9:09 UTC (permalink / raw)
  To: Aneesh Kumar K.V
  Cc: Ross Zwisler, linux-kernel, Theodore Ts'o, Alexander Viro,
	Andreas Dilger, Andrew Morton, Christoph Hellwig, Dan Williams,
	Dave Chinner, Jan Kara, Matthew Wilcox, linux-ext4,
	linux-fsdevel, linux-mm, linux-nvdimm, linux-xfs

On Mon 17-10-16 11:27:24, Aneesh Kumar K.V wrote:
> Ross Zwisler <ross.zwisler@linux.intel.com> writes:
> 
> > Now that DAX PMD faults are once again working and are now participating in
> > DAX's radix tree locking scheme, allow their config option to be enabled.
> >
> > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> > ---
> >  fs/Kconfig | 1 -
> >  1 file changed, 1 deletion(-)
> >
> > diff --git a/fs/Kconfig b/fs/Kconfig
> > index 2bc7ad7..b6f0fce 100644
> > --- a/fs/Kconfig
> > +++ b/fs/Kconfig
> > @@ -55,7 +55,6 @@ config FS_DAX_PMD
> >  	depends on FS_DAX
> >  	depends on ZONE_DEVICE
> >  	depends on TRANSPARENT_HUGEPAGE
> > -	depends on BROKEN
> >  
> >  endif # BLOCK
> 
> 
> This series made dax_pmd_fault return VM_FAULT_FALLBACK in [PATCH v6 09/17] dax: remove dax_pmd_fault(). 
> That essentially disable dax pmd for ext4. Any plans to fix that ?

I'm working on converting ext4 to the new iomap infrastructure. Once that
is done, it can use new DAX helpers for PMD faults easily.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v7 15/17] dax: add struct iomap based DAX PMD support
  2016-10-17  6:06         ` Aneesh Kumar K.V
  (?)
  (?)
@ 2016-10-17 14:55           ` Ross Zwisler
  -1 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-17 14:55 UTC (permalink / raw)
  To: Aneesh Kumar K.V
  Cc: Theodore Ts'o, Matthew Wilcox, Dave Chinner, linux-nvdimm,
	linux-kernel, Christoph Hellwig, linux-xfs, linux-mm,
	Andreas Dilger, Alexander Viro, linux-fsdevel, Jan Kara,
	linux-ext4, Andrew Morton

On Mon, Oct 17, 2016 at 11:36:55AM +0530, Aneesh Kumar K.V wrote:
> Ross Zwisler <ross.zwisler@linux.intel.com> writes:
> 
> > DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
> > locking.  This patch allows DAX PMDs to participate in the DAX radix tree
> > based locking scheme so that they can be re-enabled using the new struct
> > iomap based fault handlers.
> >
> > There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
> > mappings that have an associated block allocation, and 4k DAX empty
> > entries.  The empty entries exist to provide locking for the duration of a
> > given page fault.
> >
> > This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
> > entries, PMD DAX entries that have associated block allocations, and 2 MiB
> > DAX empty entries.
> >
> > Unlike the 4k case where we insert a struct page* into the radix tree for
> > 4k zero pages, for HZP we insert a DAX exceptional entry with the new
> > RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
> > every 2MiB hole mapping, and it doesn't make sense to have that same struct
> > page* with multiple entries in multiple trees.  This would cause contention
> > on the single page lock for the one Huge Zero Page, and it would break the
> > page->index and page->mapping associations that are assumed to be valid in
> > many other places in the kernel.
> >
> > One difficult use case is when one thread is trying to use 4k entries in
> > radix tree for a given offset, and another thread is using 2 MiB entries
> > for that same offset.  The current code handles this by making the 2 MiB
> > user fall back to 4k entries for most cases.  This was done because it is
> > the simplest solution, and because the use of 2MiB pages is already
> > opportunistic.
> >
> > If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
> > we run into the problem of how we lock out 4k page faults for the entire
> > 2MiB range while we clean out the radix tree so we can insert the 2MiB
> > entry.  We can solve this problem if we need to, but I think that the cases
> > where both 2MiB entries and 4K entries are being used for the same range
> > will be rare enough and the gain small enough that it probably won't be
> > worth the complexity.
> >
> > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> > Reviewed-by: Jan Kara <jack@suse.cz>
> > ---
> >  fs/dax.c            | 378 +++++++++++++++++++++++++++++++++++++++++++++++-----
> >  include/linux/dax.h |  55 ++++++--
> >  mm/filemap.c        |   3 +-
> >  3 files changed, 386 insertions(+), 50 deletions(-)
> >
> > diff --git a/fs/dax.c b/fs/dax.c
> > index 0582c7c..153cfd5 100644
> > --- a/fs/dax.c
> > +++ b/fs/dax.c
> > @@ -76,6 +76,26 @@ static void dax_unmap_atomic(struct block_device *bdev,
> >  	blk_queue_exit(bdev->bd_queue);
> >  }
> >  
> > +static int dax_is_pmd_entry(void *entry)
> > +{
> > +	return (unsigned long)entry & RADIX_DAX_PMD;
> > +}
> > +
> > +static int dax_is_pte_entry(void *entry)
> > +{
> > +	return !((unsigned long)entry & RADIX_DAX_PMD);
> > +}
> > +
> > +static int dax_is_zero_entry(void *entry)
> > +{
> > +	return (unsigned long)entry & RADIX_DAX_HZP;
> > +}
> 
> How about dax_is_pmd_zero_entry() ?

It's on my to-do list to convert the 4k DAX zero page case to use a singleton
page as well, in which case it's my plan to reuse this helper for both the 4k
and the PMD case.  Having it called dax_is_zero_entry() instead of
dax_is_pmd_zero_entry() allows for this - we'll just have to rename the
underling flag.
_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v7 15/17] dax: add struct iomap based DAX PMD support
@ 2016-10-17 14:55           ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-17 14:55 UTC (permalink / raw)
  To: Aneesh Kumar K.V
  Cc: Ross Zwisler, linux-kernel, Theodore Ts'o, Alexander Viro,
	Andreas Dilger, Andrew Morton, Christoph Hellwig, Dan Williams,
	Dave Chinner, Jan Kara, Matthew Wilcox, linux-ext4,
	linux-fsdevel, linux-mm, linux-nvdimm, linux-xfs

On Mon, Oct 17, 2016 at 11:36:55AM +0530, Aneesh Kumar K.V wrote:
> Ross Zwisler <ross.zwisler@linux.intel.com> writes:
> 
> > DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
> > locking.  This patch allows DAX PMDs to participate in the DAX radix tree
> > based locking scheme so that they can be re-enabled using the new struct
> > iomap based fault handlers.
> >
> > There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
> > mappings that have an associated block allocation, and 4k DAX empty
> > entries.  The empty entries exist to provide locking for the duration of a
> > given page fault.
> >
> > This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
> > entries, PMD DAX entries that have associated block allocations, and 2 MiB
> > DAX empty entries.
> >
> > Unlike the 4k case where we insert a struct page* into the radix tree for
> > 4k zero pages, for HZP we insert a DAX exceptional entry with the new
> > RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
> > every 2MiB hole mapping, and it doesn't make sense to have that same struct
> > page* with multiple entries in multiple trees.  This would cause contention
> > on the single page lock for the one Huge Zero Page, and it would break the
> > page->index and page->mapping associations that are assumed to be valid in
> > many other places in the kernel.
> >
> > One difficult use case is when one thread is trying to use 4k entries in
> > radix tree for a given offset, and another thread is using 2 MiB entries
> > for that same offset.  The current code handles this by making the 2 MiB
> > user fall back to 4k entries for most cases.  This was done because it is
> > the simplest solution, and because the use of 2MiB pages is already
> > opportunistic.
> >
> > If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
> > we run into the problem of how we lock out 4k page faults for the entire
> > 2MiB range while we clean out the radix tree so we can insert the 2MiB
> > entry.  We can solve this problem if we need to, but I think that the cases
> > where both 2MiB entries and 4K entries are being used for the same range
> > will be rare enough and the gain small enough that it probably won't be
> > worth the complexity.
> >
> > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> > Reviewed-by: Jan Kara <jack@suse.cz>
> > ---
> >  fs/dax.c            | 378 +++++++++++++++++++++++++++++++++++++++++++++++-----
> >  include/linux/dax.h |  55 ++++++--
> >  mm/filemap.c        |   3 +-
> >  3 files changed, 386 insertions(+), 50 deletions(-)
> >
> > diff --git a/fs/dax.c b/fs/dax.c
> > index 0582c7c..153cfd5 100644
> > --- a/fs/dax.c
> > +++ b/fs/dax.c
> > @@ -76,6 +76,26 @@ static void dax_unmap_atomic(struct block_device *bdev,
> >  	blk_queue_exit(bdev->bd_queue);
> >  }
> >  
> > +static int dax_is_pmd_entry(void *entry)
> > +{
> > +	return (unsigned long)entry & RADIX_DAX_PMD;
> > +}
> > +
> > +static int dax_is_pte_entry(void *entry)
> > +{
> > +	return !((unsigned long)entry & RADIX_DAX_PMD);
> > +}
> > +
> > +static int dax_is_zero_entry(void *entry)
> > +{
> > +	return (unsigned long)entry & RADIX_DAX_HZP;
> > +}
> 
> How about dax_is_pmd_zero_entry() ?

It's on my to-do list to convert the 4k DAX zero page case to use a singleton
page as well, in which case it's my plan to reuse this helper for both the 4k
and the PMD case.  Having it called dax_is_zero_entry() instead of
dax_is_pmd_zero_entry() allows for this - we'll just have to rename the
underling flag.

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v7 15/17] dax: add struct iomap based DAX PMD support
@ 2016-10-17 14:55           ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-17 14:55 UTC (permalink / raw)
  To: Aneesh Kumar K.V
  Cc: Ross Zwisler, linux-kernel, Theodore Ts'o, Alexander Viro,
	Andreas Dilger, Andrew Morton, Christoph Hellwig, Dan Williams,
	Dave Chinner, Jan Kara, Matthew Wilcox, linux-ext4,
	linux-fsdevel, linux-mm, linux-nvdimm, linux-xfs

On Mon, Oct 17, 2016 at 11:36:55AM +0530, Aneesh Kumar K.V wrote:
> Ross Zwisler <ross.zwisler@linux.intel.com> writes:
> 
> > DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
> > locking.  This patch allows DAX PMDs to participate in the DAX radix tree
> > based locking scheme so that they can be re-enabled using the new struct
> > iomap based fault handlers.
> >
> > There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
> > mappings that have an associated block allocation, and 4k DAX empty
> > entries.  The empty entries exist to provide locking for the duration of a
> > given page fault.
> >
> > This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
> > entries, PMD DAX entries that have associated block allocations, and 2 MiB
> > DAX empty entries.
> >
> > Unlike the 4k case where we insert a struct page* into the radix tree for
> > 4k zero pages, for HZP we insert a DAX exceptional entry with the new
> > RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
> > every 2MiB hole mapping, and it doesn't make sense to have that same struct
> > page* with multiple entries in multiple trees.  This would cause contention
> > on the single page lock for the one Huge Zero Page, and it would break the
> > page->index and page->mapping associations that are assumed to be valid in
> > many other places in the kernel.
> >
> > One difficult use case is when one thread is trying to use 4k entries in
> > radix tree for a given offset, and another thread is using 2 MiB entries
> > for that same offset.  The current code handles this by making the 2 MiB
> > user fall back to 4k entries for most cases.  This was done because it is
> > the simplest solution, and because the use of 2MiB pages is already
> > opportunistic.
> >
> > If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
> > we run into the problem of how we lock out 4k page faults for the entire
> > 2MiB range while we clean out the radix tree so we can insert the 2MiB
> > entry.  We can solve this problem if we need to, but I think that the cases
> > where both 2MiB entries and 4K entries are being used for the same range
> > will be rare enough and the gain small enough that it probably won't be
> > worth the complexity.
> >
> > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> > Reviewed-by: Jan Kara <jack@suse.cz>
> > ---
> >  fs/dax.c            | 378 +++++++++++++++++++++++++++++++++++++++++++++++-----
> >  include/linux/dax.h |  55 ++++++--
> >  mm/filemap.c        |   3 +-
> >  3 files changed, 386 insertions(+), 50 deletions(-)
> >
> > diff --git a/fs/dax.c b/fs/dax.c
> > index 0582c7c..153cfd5 100644
> > --- a/fs/dax.c
> > +++ b/fs/dax.c
> > @@ -76,6 +76,26 @@ static void dax_unmap_atomic(struct block_device *bdev,
> >  	blk_queue_exit(bdev->bd_queue);
> >  }
> >  
> > +static int dax_is_pmd_entry(void *entry)
> > +{
> > +	return (unsigned long)entry & RADIX_DAX_PMD;
> > +}
> > +
> > +static int dax_is_pte_entry(void *entry)
> > +{
> > +	return !((unsigned long)entry & RADIX_DAX_PMD);
> > +}
> > +
> > +static int dax_is_zero_entry(void *entry)
> > +{
> > +	return (unsigned long)entry & RADIX_DAX_HZP;
> > +}
> 
> How about dax_is_pmd_zero_entry() ?

It's on my to-do list to convert the 4k DAX zero page case to use a singleton
page as well, in which case it's my plan to reuse this helper for both the 4k
and the PMD case.  Having it called dax_is_zero_entry() instead of
dax_is_pmd_zero_entry() allows for this - we'll just have to rename the
underling flag.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

^ permalink raw reply	[flat|nested] 126+ messages in thread
* Re: [PATCH v7 15/17] dax: add struct iomap based DAX PMD support
@ 2016-10-17 14:55           ` Ross Zwisler
  0 siblings, 0 replies; 126+ messages in thread
From: Ross Zwisler @ 2016-10-17 14:55 UTC (permalink / raw)
  To: Aneesh Kumar K.V
  Cc: Ross Zwisler, linux-kernel, Theodore Ts'o, Alexander Viro,
	Andreas Dilger, Andrew Morton, Christoph Hellwig, Dan Williams,
	Dave Chinner, Jan Kara, Matthew Wilcox, linux-ext4,
	linux-fsdevel, linux-mm, linux-nvdimm, linux-xfs

On Mon, Oct 17, 2016 at 11:36:55AM +0530, Aneesh Kumar K.V wrote:
> Ross Zwisler <ross.zwisler@linux.intel.com> writes:
> 
> > DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based
> > locking.  This patch allows DAX PMDs to participate in the DAX radix tree
> > based locking scheme so that they can be re-enabled using the new struct
> > iomap based fault handlers.
> >
> > There are currently three types of DAX 4k entries: 4k zero pages, 4k DAX
> > mappings that have an associated block allocation, and 4k DAX empty
> > entries.  The empty entries exist to provide locking for the duration of a
> > given page fault.
> >
> > This patch adds three equivalent 2MiB DAX entries: Huge Zero Page (HZP)
> > entries, PMD DAX entries that have associated block allocations, and 2 MiB
> > DAX empty entries.
> >
> > Unlike the 4k case where we insert a struct page* into the radix tree for
> > 4k zero pages, for HZP we insert a DAX exceptional entry with the new
> > RADIX_DAX_HZP flag set.  This is because we use a single 2 MiB zero page in
> > every 2MiB hole mapping, and it doesn't make sense to have that same struct
> > page* with multiple entries in multiple trees.  This would cause contention
> > on the single page lock for the one Huge Zero Page, and it would break the
> > page->index and page->mapping associations that are assumed to be valid in
> > many other places in the kernel.
> >
> > One difficult use case is when one thread is trying to use 4k entries in
> > radix tree for a given offset, and another thread is using 2 MiB entries
> > for that same offset.  The current code handles this by making the 2 MiB
> > user fall back to 4k entries for most cases.  This was done because it is
> > the simplest solution, and because the use of 2MiB pages is already
> > opportunistic.
> >
> > If we were to try to upgrade from 4k pages to 2MiB pages for a given range,
> > we run into the problem of how we lock out 4k page faults for the entire
> > 2MiB range while we clean out the radix tree so we can insert the 2MiB
> > entry.  We can solve this problem if we need to, but I think that the cases
> > where both 2MiB entries and 4K entries are being used for the same range
> > will be rare enough and the gain small enough that it probably won't be
> > worth the complexity.
> >
> > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> > Reviewed-by: Jan Kara <jack@suse.cz>
> > ---
> >  fs/dax.c            | 378 +++++++++++++++++++++++++++++++++++++++++++++++-----
> >  include/linux/dax.h |  55 ++++++--
> >  mm/filemap.c        |   3 +-
> >  3 files changed, 386 insertions(+), 50 deletions(-)
> >
> > diff --git a/fs/dax.c b/fs/dax.c
> > index 0582c7c..153cfd5 100644
> > --- a/fs/dax.c
> > +++ b/fs/dax.c
> > @@ -76,6 +76,26 @@ static void dax_unmap_atomic(struct block_device *bdev,
> >  	blk_queue_exit(bdev->bd_queue);
> >  }
> >  
> > +static int dax_is_pmd_entry(void *entry)
> > +{
> > +	return (unsigned long)entry & RADIX_DAX_PMD;
> > +}
> > +
> > +static int dax_is_pte_entry(void *entry)
> > +{
> > +	return !((unsigned long)entry & RADIX_DAX_PMD);
> > +}
> > +
> > +static int dax_is_zero_entry(void *entry)
> > +{
> > +	return (unsigned long)entry & RADIX_DAX_HZP;
> > +}
> 
> How about dax_is_pmd_zero_entry() ?

It's on my to-do list to convert the 4k DAX zero page case to use a singleton
page as well, in which case it's my plan to reuse this helper for both the 4k
and the PMD case.  Having it called dax_is_zero_entry() instead of
dax_is_pmd_zero_entry() allows for this - we'll just have to rename the
underling flag.

^ permalink raw reply	[flat|nested] 126+ messages in thread
end of thread, other threads:[~2016-10-17 14:55 UTC | newest]

Thread overview: 126+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-10-12 22:50 [PATCH v6 00/17] re-enable DAX PMD support Ross Zwisler
2016-10-12 22:50 ` Ross Zwisler
2016-10-12 22:50 ` Ross Zwisler
2016-10-12 22:50 ` Ross Zwisler
2016-10-12 22:50 ` Ross Zwisler
2016-10-12 22:50 ` [PATCH v6 01/17] ext4: allow DAX writeback for hole punch Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50 ` [PATCH v6 02/17] ext4: tell DAX the size of allocation holes Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50 ` [PATCH v6 03/17] dax: remove buffer_size_valid() Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50 ` [PATCH v6 04/17] ext2: remove support for DAX PMD faults Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50 ` [PATCH v6 05/17] dax: make 'wait_table' global variable static Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50 ` [PATCH v6 06/17] dax: remove the last BUG_ON() from fs/dax.c Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50 ` [PATCH v6 07/17] dax: consistent variable naming for DAX entries Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50 ` [PATCH v6 08/17] dax: coordinate locking for offsets in PMD range Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50 ` [PATCH v6 09/17] dax: remove dax_pmd_fault() Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50 ` [PATCH v6 10/17] dax: correct dax iomap code namespace Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50 ` [PATCH v6 11/17] dax: add dax_iomap_sector() helper function Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50 ` [PATCH v6 12/17] dax: dax_iomap_fault() needs to call iomap_end() Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50 ` [PATCH v6 13/17] dax: move RADIX_DAX_* defines to dax.h Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50 ` [PATCH v6 14/17] dax: move put_(un)locked_mapping_entry() in dax.c Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-13 15:11   ` Jan Kara
2016-10-13 15:11     ` Jan Kara
2016-10-13 15:11     ` Jan Kara
2016-10-12 22:50 ` [PATCH v6 15/17] dax: add struct iomap based DAX PMD support Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-13 15:42   ` Jan Kara
2016-10-13 15:42     ` Jan Kara
2016-10-13 15:42     ` Jan Kara
2016-10-13 15:42     ` Jan Kara
2016-10-13 15:42     ` Jan Kara
2016-10-13 19:23     ` [PATCH v7 " Ross Zwisler
2016-10-13 19:23       ` Ross Zwisler
2016-10-13 19:23       ` Ross Zwisler
2016-10-13 19:23       ` Ross Zwisler
2016-10-17  6:06       ` Aneesh Kumar K.V
2016-10-17  6:06         ` Aneesh Kumar K.V
2016-10-17  6:06         ` Aneesh Kumar K.V
2016-10-17  6:06         ` Aneesh Kumar K.V
2016-10-17  6:06         ` Aneesh Kumar K.V
2016-10-17 14:55         ` Ross Zwisler
2016-10-17 14:55           ` Ross Zwisler
2016-10-17 14:55           ` Ross Zwisler
2016-10-17 14:55           ` Ross Zwisler
2016-10-13 19:25     ` [PATCH v6 " Ross Zwisler
2016-10-13 19:25       ` Ross Zwisler
2016-10-13 19:25       ` Ross Zwisler
2016-10-13 19:25       ` Ross Zwisler
2016-10-12 22:50 ` [PATCH v6 16/17] xfs: use struct iomap based DAX PMD fault path Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50 ` [PATCH v6 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-12 22:50   ` Ross Zwisler
2016-10-13 15:42   ` Jan Kara
2016-10-13 15:42     ` Jan Kara
2016-10-13 15:42     ` Jan Kara
2016-10-13 15:42     ` Jan Kara
2016-10-17  5:57   ` Aneesh Kumar K.V
2016-10-17  5:57     ` Aneesh Kumar K.V
2016-10-17  5:57     ` Aneesh Kumar K.V
2016-10-17  5:57     ` Aneesh Kumar K.V
2016-10-17  5:57     ` Aneesh Kumar K.V
2016-10-17  5:57     ` Aneesh Kumar K.V
2016-10-17  9:09     ` Jan Kara
2016-10-17  9:09       ` Jan Kara
2016-10-17  9:09       ` Jan Kara
2016-10-17  9:09       ` Jan Kara

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