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* [PATCH v2 2/2] [PATCH] xfs: Close race between direct IO and xfs_break_layouts()
@ 2018-08-08 17:31 Dave Jiang
  2018-08-10 15:48 ` Darrick J. Wong
  2018-08-10 18:31 ` Eric Sandeen
  0 siblings, 2 replies; 12+ messages in thread
From: Dave Jiang @ 2018-08-08 17:31 UTC (permalink / raw)
  To: tytso, darrick.wong, jack, zwisler
  Cc: linux-nvdimm, david, linux-xfs, linux-fsdevel, lczerner, linux-ext4, hch

This patch is the duplicate of ross's fix for ext4 for xfs.

If the refcount of a page is lowered between the time that it is returned
by dax_busy_page() and when the refcount is again checked in
xfs_break_layouts() => ___wait_var_event(), the waiting function
xfs_wait_dax_page() will never be called.  This means that
xfs_break_layouts() will still have 'retry' set to false, so we'll stop
looping and never check the refcount of other pages in this inode.

Instead, always continue looping as long as dax_layout_busy_page() gives us
a page which it found with an elevated refcount.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---

Sorry resend, forgot to add Jan's reviewed-by.

v2:
- Rename parameter from did_unlock to retry (Jan)

 fs/xfs/xfs_file.c |    9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index a3e7767a5715..cd6f0d8c4922 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -721,12 +721,10 @@ xfs_file_write_iter(
 
 static void
 xfs_wait_dax_page(
-	struct inode		*inode,
-	bool			*did_unlock)
+	struct inode		*inode)
 {
 	struct xfs_inode        *ip = XFS_I(inode);
 
-	*did_unlock = true;
 	xfs_iunlock(ip, XFS_MMAPLOCK_EXCL);
 	schedule();
 	xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
@@ -736,7 +734,7 @@ static int
 xfs_break_dax_layouts(
 	struct inode		*inode,
 	uint			iolock,
-	bool			*did_unlock)
+	bool			*retry)
 {
 	struct page		*page;
 
@@ -746,9 +744,10 @@ xfs_break_dax_layouts(
 	if (!page)
 		return 0;
 
+	*retry = true;
 	return ___wait_var_event(&page->_refcount,
 			atomic_read(&page->_refcount) == 1, TASK_INTERRUPTIBLE,
-			0, 0, xfs_wait_dax_page(inode, did_unlock));
+			0, 0, xfs_wait_dax_page(inode));
 }
 
 int

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^ permalink raw reply related	[flat|nested] 12+ messages in thread
* [PATCH v2 1/2] ext4: Close race between direct IO and ext4_break_layouts()
@ 2018-08-08 17:25 Dave Jiang
  2018-08-08 17:26 ` [PATCH v2 2/2] [PATCH] xfs: Close race between direct IO and xfs_break_layouts() Dave Jiang
  0 siblings, 1 reply; 12+ messages in thread
From: Dave Jiang @ 2018-08-08 17:25 UTC (permalink / raw)
  To: tytso, darrick.wong, jack, zwisler
  Cc: linux-nvdimm, david, linux-xfs, linux-fsdevel, lczerner, linux-ext4, hch

From: Ross Zwisler <zwisler@kernel.org>

If the refcount of a page is lowered between the time that it is returned
by dax_busy_page() and when the refcount is again checked in
ext4_break_layouts() => ___wait_var_event(), the waiting function
ext4_wait_dax_page() will never be called.  This means that
ext4_break_layouts() will still have 'retry' set to false, so we'll stop
looping and never check the refcount of other pages in this inode.

Instead, always continue looping as long as dax_layout_busy_page() gives us
a page which it found with an elevated refcount.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---

v2:
- remove verbiage in comment header (Jan)

 fs/ext4/inode.c |    9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 8f6ad7667974..d2663a1e3ec2 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4191,9 +4191,8 @@ int ext4_update_disksize_before_punch(struct inode *inode, loff_t offset,
 	return 0;
 }
 
-static void ext4_wait_dax_page(struct ext4_inode_info *ei, bool *did_unlock)
+static void ext4_wait_dax_page(struct ext4_inode_info *ei)
 {
-	*did_unlock = true;
 	up_write(&ei->i_mmap_sem);
 	schedule();
 	down_write(&ei->i_mmap_sem);
@@ -4203,14 +4202,12 @@ int ext4_break_layouts(struct inode *inode)
 {
 	struct ext4_inode_info *ei = EXT4_I(inode);
 	struct page *page;
-	bool retry;
 	int error;
 
 	if (WARN_ON_ONCE(!rwsem_is_locked(&ei->i_mmap_sem)))
 		return -EINVAL;
 
 	do {
-		retry = false;
 		page = dax_layout_busy_page(inode->i_mapping);
 		if (!page)
 			return 0;
@@ -4218,8 +4215,8 @@ int ext4_break_layouts(struct inode *inode)
 		error = ___wait_var_event(&page->_refcount,
 				atomic_read(&page->_refcount) == 1,
 				TASK_INTERRUPTIBLE, 0, 0,
-				ext4_wait_dax_page(ei, &retry));
-	} while (error == 0 && retry);
+				ext4_wait_dax_page(ei));
+	} while (error == 0);
 
 	return error;
 }

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^ permalink raw reply related	[flat|nested] 12+ messages in thread

end of thread, other threads:[~2018-08-10 19:26 UTC | newest]

Thread overview: 12+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-08-08 17:31 [PATCH v2 2/2] [PATCH] xfs: Close race between direct IO and xfs_break_layouts() Dave Jiang
2018-08-10 15:48 ` Darrick J. Wong
2018-08-10 15:54   ` Dave Jiang
2018-08-10 16:02     ` Darrick J. Wong
2018-08-10 16:05       ` Dave Jiang
2018-08-10 18:31 ` Eric Sandeen
2018-08-10 19:23   ` Dave Jiang
2018-08-10 19:24     ` Ross Zwisler
2018-08-10 19:26       ` Eric Sandeen
  -- strict thread matches above, loose matches on Subject: below --
2018-08-08 17:25 [PATCH v2 1/2] ext4: Close race between direct IO and ext4_break_layouts() Dave Jiang
2018-08-08 17:26 ` [PATCH v2 2/2] [PATCH] xfs: Close race between direct IO and xfs_break_layouts() Dave Jiang
2018-08-09  8:57   ` Jan Kara
2018-08-09 16:21     ` Dave Jiang

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