[PATCH 00/33] Network fs helper library & fscache kiocb API [ver #3]

[PATCH 00/33] Network fs helper library & fscache kiocb API [ver #3]

[David Howells]

Here's a set of patches to do two things:

 (1) Add a helper library to handle the new VM readahead interface.  This
     is intended to be used unconditionally by the filesystem (whether or
     not caching is enabled) and provides a common framework for doing
     caching, transparent huge pages and, in the future, possibly fscrypt
     and read bandwidth maximisation.  It also allows the netfs and the
     cache to align, expand and slice up a read request from the VM in
     various ways; the netfs need only provide a function to read a stretch
     of data to the pagecache and the helper takes care of the rest.

 (2) Add an alternative fscache/cachfiles I/O API that uses the kiocb
     facility to do async DIO to transfer data to/from the netfs's pages,
     rather than using readpage with wait queue snooping on one side and
     vfs_write() on the other.  It also uses less memory, since it doesn't
     do buffered I/O on the backing file.

     Note that this uses SEEK_HOLE/SEEK_DATA to locate the data available
     to be read from the cache.  Whilst this is an improvement from the
     bmap interface, it still has a problem with regard to a modern
     extent-based filesystem inserting or removing bridging blocks of
     zeros.  Fixing that requires a much greater overhaul.

This is a step towards overhauling the fscache API.  The change is opt-in
on the part of the network filesystem.  A netfs should not try to mix the
old and the new API because of conflicting ways of handling pages and the
PG_fscache page flag and because it would be mixing DIO with buffered I/O.
Further, the helper library can't be used with the old API.

This does not change any of the fscache cookie handling APIs or the way
invalidation is done.

In the near term, I intend to deprecate and remove the old I/O API
(fscache_allocate_page{,s}(), fscache_read_or_alloc_page{,s}(),
fscache_write_page() and fscache_uncache_page()) and eventually replace
most of fscache/cachefiles with something simpler and easier to follow.

The patchset contains five parts:

 (1) Some helper patches, including provision of an ITER_XARRAY iov
     iterator and a function to do readahead expansion.

 (2) Patches to add the netfs helper library.

 (3) A patch to add the fscache/cachefiles kiocb API.

 (4) Patches to add support in AFS for this.

 (5) Patches from Jeff Layton to add support in Ceph for this.

Dave Wysochanski also has patches for NFS for this, though they're not
included on this branch as there's an issue with PNFS.

With this, AFS without a cache passes all expected xfstests; with a cache,
there's an extra failure, but that's also there before these patches.
Fixing that probably requires a greater overhaul.  Ceph and NFS also pass
the expected tests.

These patches can be found also on:

	https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=fscache-netfs-lib

For diffing reference, the tag for the 9th Feb pull request is
fscache-ioapi-20210203 and can be found in the same repository.



Changes
=======

 (v3) Rolled in the bug fixes.

      Adjusted the functions that unlock and wait for PG_fscache according
      to Linus's suggestion.

      Hold a ref on a page when PG_fscache is set as per Linus's
      suggestion.

      Dropped NFS support and added Ceph support.

 (v2) Fixed some bugs and added NFS support.


References
==========

These patches have been published for review before, firstly as part of a
larger set:

Link: https://lore.kernel.org/linux-fsdevel/158861203563.340223.7585359869938129395.stgit@warthog.procyon.org.uk/

Link: https://lore.kernel.org/linux-fsdevel/159465766378.1376105.11619976251039287525.stgit@warthog.procyon.org.uk/
Link: https://lore.kernel.org/linux-fsdevel/159465784033.1376674.18106463693989811037.stgit@warthog.procyon.org.uk/
Link: https://lore.kernel.org/linux-fsdevel/159465821598.1377938.2046362270225008168.stgit@warthog.procyon.org.uk/

Link: https://lore.kernel.org/linux-fsdevel/160588455242.3465195.3214733858273019178.stgit@warthog.procyon.org.uk/

Then as a cut-down set:

Link: https://lore.kernel.org/linux-fsdevel/161118128472.1232039.11746799833066425131.stgit@warthog.procyon.org.uk/

Link: https://lore.kernel.org/linux-fsdevel/161161025063.2537118.2009249444682241405.stgit@warthog.procyon.org.uk/


Proposals/information about the design has been published here:

Link: https://lore.kernel.org/lkml/24942.1573667720@warthog.procyon.org.uk/
Link: https://lore.kernel.org/linux-fsdevel/2758811.1610621106@warthog.procyon.org.uk/
Link: https://lore.kernel.org/linux-fsdevel/1441311.1598547738@warthog.procyon.org.uk/
Link: https://lore.kernel.org/linux-fsdevel/160655.1611012999@warthog.procyon.org.uk/

And requests for information:

Link: https://lore.kernel.org/linux-fsdevel/3326.1579019665@warthog.procyon.org.uk/
Link: https://lore.kernel.org/linux-fsdevel/4467.1579020509@warthog.procyon.org.uk/
Link: https://lore.kernel.org/linux-fsdevel/3577430.1579705075@warthog.procyon.org.uk/

The NFS parts, though not included here, have been tested by someone who's
using fscache in production:

Link: https://listman.redhat.com/archives/linux-cachefs/2020-December/msg00000.html

I've posted partial patches to try and help 9p and cifs along:

Link: https://lore.kernel.org/linux-fsdevel/1514086.1605697347@warthog.procyon.org.uk/
Link: https://lore.kernel.org/linux-cifs/1794123.1605713481@warthog.procyon.org.uk/
Link: https://lore.kernel.org/linux-fsdevel/241017.1612263863@warthog.procyon.org.uk/
Link: https://lore.kernel.org/linux-cifs/270998.1612265397@warthog.procyon.org.uk/

David
---
David Howells (27):
      iov_iter: Add ITER_XARRAY
      mm: Add an unlock function for PG_private_2/PG_fscache
      mm: Implement readahead_control pageset expansion
      vfs: Export rw_verify_area() for use by cachefiles
      netfs: Make a netfs helper module
      netfs, mm: Move PG_fscache helper funcs to linux/netfs.h
      netfs, mm: Add unlock_page_fscache() and wait_on_page_fscache()
      netfs: Provide readahead and readpage netfs helpers
      netfs: Add tracepoints
      netfs: Gather stats
      netfs: Add write_begin helper
      netfs: Define an interface to talk to a cache
      netfs: Hold a ref on a page when PG_private_2 is set
      fscache, cachefiles: Add alternate API to use kiocb for read/write to cache
      afs: Disable use of the fscache I/O routines
      afs: Pass page into dirty region helpers to provide THP size
      afs: Print the operation debug_id when logging an unexpected data version
      afs: Move key to afs_read struct
      afs: Don't truncate iter during data fetch
      afs: Log remote unmarshalling errors
      afs: Set up the iov_iter before calling afs_extract_data()
      afs: Use ITER_XARRAY for writing
      afs: Wait on PG_fscache before modifying/releasing a page
      afs: Extract writeback extension into its own function
      afs: Prepare for use of THPs
      afs: Use the fs operation ops to handle FetchData completion
      afs: Use new fscache read helper API

Jeff Layton (6):
      ceph: disable old fscache readpage handling
      ceph: rework PageFsCache handling
      ceph: fix fscache invalidation
      ceph: convert readpage to fscache read helper
      ceph: plug write_begin into read helper
      ceph: convert ceph_readpages to ceph_readahead


 fs/Kconfig                    |    1 +
 fs/Makefile                   |    1 +
 fs/afs/Kconfig                |    1 +
 fs/afs/dir.c                  |  225 ++++---
 fs/afs/file.c                 |  470 ++++---------
 fs/afs/fs_operation.c         |    4 +-
 fs/afs/fsclient.c             |  108 +--
 fs/afs/inode.c                |    7 +-
 fs/afs/internal.h             |   58 +-
 fs/afs/rxrpc.c                |  150 ++---
 fs/afs/write.c                |  610 +++++++++--------
 fs/afs/yfsclient.c            |   82 +--
 fs/cachefiles/Makefile        |    1 +
 fs/cachefiles/interface.c     |    5 +-
 fs/cachefiles/internal.h      |    9 +
 fs/cachefiles/rdwr2.c         |  412 ++++++++++++
 fs/ceph/Kconfig               |    1 +
 fs/ceph/addr.c                |  535 ++++++---------
 fs/ceph/cache.c               |  125 ----
 fs/ceph/cache.h               |  101 +--
 fs/ceph/caps.c                |   10 +-
 fs/ceph/inode.c               |    1 +
 fs/ceph/super.h               |    1 +
 fs/fscache/Kconfig            |    1 +
 fs/fscache/Makefile           |    3 +-
 fs/fscache/internal.h         |    3 +
 fs/fscache/page.c             |    2 +-
 fs/fscache/page2.c            |  117 ++++
 fs/fscache/stats.c            |    1 +
 fs/internal.h                 |    5 -
 fs/netfs/Kconfig              |   23 +
 fs/netfs/Makefile             |    5 +
 fs/netfs/internal.h           |   97 +++
 fs/netfs/read_helper.c        | 1169 +++++++++++++++++++++++++++++++++
 fs/netfs/stats.c              |   59 ++
 fs/read_write.c               |    1 +
 include/linux/fs.h            |    1 +
 include/linux/fscache-cache.h |    4 +
 include/linux/fscache.h       |   40 +-
 include/linux/netfs.h         |  195 ++++++
 include/linux/pagemap.h       |    3 +
 include/net/af_rxrpc.h        |    2 +-
 include/trace/events/afs.h    |   74 +--
 include/trace/events/netfs.h  |  201 ++++++
 mm/filemap.c                  |   20 +
 mm/readahead.c                |   70 ++
 net/rxrpc/recvmsg.c           |    9 +-
 47 files changed, 3473 insertions(+), 1550 deletions(-)
 create mode 100644 fs/cachefiles/rdwr2.c
 create mode 100644 fs/fscache/page2.c
 create mode 100644 fs/netfs/Kconfig
 create mode 100644 fs/netfs/Makefile
 create mode 100644 fs/netfs/internal.h
 create mode 100644 fs/netfs/read_helper.c
 create mode 100644 fs/netfs/stats.c
 create mode 100644 include/linux/netfs.h
 create mode 100644 include/trace/events/netfs.h

[PATCH 01/33] iov_iter: Add ITER_XARRAY

[David Howells]

Add an iterator, ITER_XARRAY, that walks through a set of pages attached to
an xarray, starting at a given page and offset and walking for the
specified amount of bytes.  The iterator supports transparent huge pages.

The caller must guarantee that the pages are all present and they must be
locked using PG_locked, PG_writeback or PG_fscache to prevent them from
going away or being migrated whilst they're being accessed.

This is useful for copying data from socket buffers to inodes in network
filesystems and for transferring data between those inodes and the cache
using direct I/O.

Whilst it is true that ITER_BVEC could be used instead, that would require
a bio_vec array to be allocated to refer to all the pages - which should be
redundant if inode->i_pages also points to all these pages.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Alexander Viro <viro@zeniv.linux.org.uk>
cc: Matthew Wilcox (Oracle) <willy@infradead.org>
cc: Christoph Hellwig <hch@lst.de>
cc: linux-mm@kvack.org
cc: linux-cachefs@redhat.com
cc: linux-afs@lists.infradead.org
cc: linux-nfs@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: ceph-devel@vger.kernel.org
cc: v9fs-developer@lists.sourceforge.net
cc: linux-fsdevel@vger.kernel.org
---

 include/linux/uio.h |   11 ++
 lib/iov_iter.c      |  313 +++++++++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 301 insertions(+), 23 deletions(-)

diff --git a/include/linux/uio.h b/include/linux/uio.h
index 72d88566694e..08b186df54ac 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -10,6 +10,7 @@
 #include <uapi/linux/uio.h>
 
 struct page;
+struct address_space;
 struct pipe_inode_info;
 
 struct kvec {
@@ -24,6 +25,7 @@ enum iter_type {
 	ITER_BVEC = 16,
 	ITER_PIPE = 32,
 	ITER_DISCARD = 64,
+	ITER_XARRAY = 128,
 };
 
 struct iov_iter {
@@ -39,6 +41,7 @@ struct iov_iter {
 		const struct iovec *iov;
 		const struct kvec *kvec;
 		const struct bio_vec *bvec;
+		struct xarray *xarray;
 		struct pipe_inode_info *pipe;
 	};
 	union {
@@ -47,6 +50,7 @@ struct iov_iter {
 			unsigned int head;
 			unsigned int start_head;
 		};
+		loff_t xarray_start;
 	};
 };
 
@@ -80,6 +84,11 @@ static inline bool iov_iter_is_discard(const struct iov_iter *i)
 	return iov_iter_type(i) == ITER_DISCARD;
 }
 
+static inline bool iov_iter_is_xarray(const struct iov_iter *i)
+{
+	return iov_iter_type(i) == ITER_XARRAY;
+}
+
 static inline unsigned char iov_iter_rw(const struct iov_iter *i)
 {
 	return i->type & (READ | WRITE);
@@ -221,6 +230,8 @@ void iov_iter_bvec(struct iov_iter *i, unsigned int direction, const struct bio_
 void iov_iter_pipe(struct iov_iter *i, unsigned int direction, struct pipe_inode_info *pipe,
 			size_t count);
 void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count);
+void iov_iter_xarray(struct iov_iter *i, unsigned int direction, struct xarray *xarray,
+		     loff_t start, size_t count);
 ssize_t iov_iter_get_pages(struct iov_iter *i, struct page **pages,
 			size_t maxsize, unsigned maxpages, size_t *start);
 ssize_t iov_iter_get_pages_alloc(struct iov_iter *i, struct page ***pages,
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index a21e6a5792c5..f53a57588489 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -78,7 +78,44 @@
 	}						\
 }
 
-#define iterate_all_kinds(i, n, v, I, B, K) {			\
+#define iterate_xarray(i, n, __v, skip, STEP) {		\
+	struct page *head = NULL;				\
+	size_t wanted = n, seg, offset;				\
+	loff_t start = i->xarray_start + skip;			\
+	pgoff_t index = start >> PAGE_SHIFT;			\
+	int j;							\
+								\
+	XA_STATE(xas, i->xarray, index);			\
+								\
+	rcu_read_lock();						\
+	xas_for_each(&xas, head, ULONG_MAX) {				\
+		if (xas_retry(&xas, head))				\
+			continue;					\
+		if (WARN_ON(xa_is_value(head)))				\
+			break;						\
+		if (WARN_ON(PageHuge(head)))				\
+			break;						\
+		for (j = (head->index < index) ? index - head->index : 0; \
+		     j < thp_nr_pages(head); j++) {			\
+			__v.bv_page = head + j;				\
+			offset = (i->xarray_start + skip) & ~PAGE_MASK;	\
+			seg = PAGE_SIZE - offset;			\
+			__v.bv_offset = offset;				\
+			__v.bv_len = min(n, seg);			\
+			(void)(STEP);					\
+			n -= __v.bv_len;				\
+			skip += __v.bv_len;				\
+			if (n == 0)					\
+				break;					\
+		}							\
+		if (n == 0)						\
+			break;						\
+	}							\
+	rcu_read_unlock();					\
+	n = wanted - n;						\
+}
+
+#define iterate_all_kinds(i, n, v, I, B, K, X) {		\
 	if (likely(n)) {					\
 		size_t skip = i->iov_offset;			\
 		if (unlikely(i->type & ITER_BVEC)) {		\
@@ -90,6 +127,9 @@
 			struct kvec v;				\
 			iterate_kvec(i, n, v, kvec, skip, (K))	\
 		} else if (unlikely(i->type & ITER_DISCARD)) {	\
+		} else if (unlikely(i->type & ITER_XARRAY)) {	\
+			struct bio_vec v;			\
+			iterate_xarray(i, n, v, skip, (X));	\
 		} else {					\
 			const struct iovec *iov;		\
 			struct iovec v;				\
@@ -98,7 +138,7 @@
 	}							\
 }
 
-#define iterate_and_advance(i, n, v, I, B, K) {			\
+#define iterate_and_advance(i, n, v, I, B, K, X) {		\
 	if (unlikely(i->count < n))				\
 		n = i->count;					\
 	if (i->count) {						\
@@ -123,6 +163,9 @@
 			i->kvec = kvec;				\
 		} else if (unlikely(i->type & ITER_DISCARD)) {	\
 			skip += n;				\
+		} else if (unlikely(i->type & ITER_XARRAY)) {	\
+			struct bio_vec v;			\
+			iterate_xarray(i, n, v, skip, (X))	\
 		} else {					\
 			const struct iovec *iov;		\
 			struct iovec v;				\
@@ -636,7 +679,9 @@ size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
 		copyout(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len),
 		memcpy_to_page(v.bv_page, v.bv_offset,
 			       (from += v.bv_len) - v.bv_len, v.bv_len),
-		memcpy(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len)
+		memcpy(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len),
+		memcpy_to_page(v.bv_page, v.bv_offset,
+			       (from += v.bv_len) - v.bv_len, v.bv_len)
 	)
 
 	return bytes;
@@ -752,6 +797,16 @@ size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
 			bytes = curr_addr - s_addr - rem;
 			return bytes;
 		}
+		}),
+		({
+		rem = copy_mc_to_page(v.bv_page, v.bv_offset,
+				      (from += v.bv_len) - v.bv_len, v.bv_len);
+		if (rem) {
+			curr_addr = (unsigned long) from;
+			bytes = curr_addr - s_addr - rem;
+			rcu_read_unlock();
+			return bytes;
+		}
 		})
 	)
 
@@ -773,7 +828,9 @@ size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
 		copyin((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
 		memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
 				 v.bv_offset, v.bv_len),
-		memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
+		memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
+		memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
+				 v.bv_offset, v.bv_len)
 	)
 
 	return bytes;
@@ -799,7 +856,9 @@ bool _copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i)
 		0;}),
 		memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
 				 v.bv_offset, v.bv_len),
-		memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
+		memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
+		memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
+				 v.bv_offset, v.bv_len)
 	)
 
 	iov_iter_advance(i, bytes);
@@ -819,7 +878,9 @@ size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
 					 v.iov_base, v.iov_len),
 		memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
 				 v.bv_offset, v.bv_len),
-		memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
+		memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
+		memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
+				 v.bv_offset, v.bv_len)
 	)
 
 	return bytes;
@@ -854,7 +915,9 @@ size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
 		memcpy_page_flushcache((to += v.bv_len) - v.bv_len, v.bv_page,
 				 v.bv_offset, v.bv_len),
 		memcpy_flushcache((to += v.iov_len) - v.iov_len, v.iov_base,
-			v.iov_len)
+			v.iov_len),
+		memcpy_page_flushcache((to += v.bv_len) - v.bv_len, v.bv_page,
+				 v.bv_offset, v.bv_len)
 	)
 
 	return bytes;
@@ -878,7 +941,9 @@ bool _copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i)
 		0;}),
 		memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
 				 v.bv_offset, v.bv_len),
-		memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
+		memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
+		memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
+				 v.bv_offset, v.bv_len)
 	)
 
 	iov_iter_advance(i, bytes);
@@ -915,7 +980,7 @@ size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
 {
 	if (unlikely(!page_copy_sane(page, offset, bytes)))
 		return 0;
-	if (i->type & (ITER_BVEC|ITER_KVEC)) {
+	if (i->type & (ITER_BVEC | ITER_KVEC | ITER_XARRAY)) {
 		void *kaddr = kmap_atomic(page);
 		size_t wanted = copy_to_iter(kaddr + offset, bytes, i);
 		kunmap_atomic(kaddr);
@@ -938,7 +1003,7 @@ size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
 		WARN_ON(1);
 		return 0;
 	}
-	if (i->type & (ITER_BVEC|ITER_KVEC)) {
+	if (i->type & (ITER_BVEC | ITER_KVEC | ITER_XARRAY)) {
 		void *kaddr = kmap_atomic(page);
 		size_t wanted = _copy_from_iter(kaddr + offset, bytes, i);
 		kunmap_atomic(kaddr);
@@ -982,7 +1047,8 @@ size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
 	iterate_and_advance(i, bytes, v,
 		clear_user(v.iov_base, v.iov_len),
 		memzero_page(v.bv_page, v.bv_offset, v.bv_len),
-		memset(v.iov_base, 0, v.iov_len)
+		memset(v.iov_base, 0, v.iov_len),
+		memzero_page(v.bv_page, v.bv_offset, v.bv_len)
 	)
 
 	return bytes;
@@ -1006,7 +1072,9 @@ size_t iov_iter_copy_from_user_atomic(struct page *page,
 		copyin((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
 		memcpy_from_page((p += v.bv_len) - v.bv_len, v.bv_page,
 				 v.bv_offset, v.bv_len),
-		memcpy((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
+		memcpy((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
+		memcpy_from_page((p += v.bv_len) - v.bv_len, v.bv_page,
+				 v.bv_offset, v.bv_len)
 	)
 	kunmap_atomic(kaddr);
 	return bytes;
@@ -1077,7 +1145,12 @@ void iov_iter_advance(struct iov_iter *i, size_t size)
 		i->count -= size;
 		return;
 	}
-	iterate_and_advance(i, size, v, 0, 0, 0)
+	if (unlikely(iov_iter_is_xarray(i))) {
+		i->iov_offset += size;
+		i->count -= size;
+		return;
+	}
+	iterate_and_advance(i, size, v, 0, 0, 0, 0)
 }
 EXPORT_SYMBOL(iov_iter_advance);
 
@@ -1121,7 +1194,12 @@ void iov_iter_revert(struct iov_iter *i, size_t unroll)
 		return;
 	}
 	unroll -= i->iov_offset;
-	if (iov_iter_is_bvec(i)) {
+	if (iov_iter_is_xarray(i)) {
+		BUG(); /* We should never go beyond the start of the specified
+			* range since we might then be straying into pages that
+			* aren't pinned.
+			*/
+	} else if (iov_iter_is_bvec(i)) {
 		const struct bio_vec *bvec = i->bvec;
 		while (1) {
 			size_t n = (--bvec)->bv_len;
@@ -1158,9 +1236,9 @@ size_t iov_iter_single_seg_count(const struct iov_iter *i)
 		return i->count;	// it is a silly place, anyway
 	if (i->nr_segs == 1)
 		return i->count;
-	if (unlikely(iov_iter_is_discard(i)))
+	if (unlikely(iov_iter_is_discard(i) || iov_iter_is_xarray(i)))
 		return i->count;
-	else if (iov_iter_is_bvec(i))
+	if (iov_iter_is_bvec(i))
 		return min(i->count, i->bvec->bv_len - i->iov_offset);
 	else
 		return min(i->count, i->iov->iov_len - i->iov_offset);
@@ -1208,6 +1286,31 @@ void iov_iter_pipe(struct iov_iter *i, unsigned int direction,
 }
 EXPORT_SYMBOL(iov_iter_pipe);
 
+/**
+ * iov_iter_xarray - Initialise an I/O iterator to use the pages in an xarray
+ * @i: The iterator to initialise.
+ * @direction: The direction of the transfer.
+ * @xarray: The xarray to access.
+ * @start: The start file position.
+ * @count: The size of the I/O buffer in bytes.
+ *
+ * Set up an I/O iterator to either draw data out of the pages attached to an
+ * inode or to inject data into those pages.  The pages *must* be prevented
+ * from evaporation, either by taking a ref on them or locking them by the
+ * caller.
+ */
+void iov_iter_xarray(struct iov_iter *i, unsigned int direction,
+		     struct xarray *xarray, loff_t start, size_t count)
+{
+	BUG_ON(direction & ~1);
+	i->type = ITER_XARRAY | (direction & (READ | WRITE));
+	i->xarray = xarray;
+	i->xarray_start = start;
+	i->count = count;
+	i->iov_offset = 0;
+}
+EXPORT_SYMBOL(iov_iter_xarray);
+
 /**
  * iov_iter_discard - Initialise an I/O iterator that discards data
  * @i: The iterator to initialise.
@@ -1241,7 +1344,8 @@ unsigned long iov_iter_alignment(const struct iov_iter *i)
 	iterate_all_kinds(i, size, v,
 		(res |= (unsigned long)v.iov_base | v.iov_len, 0),
 		res |= v.bv_offset | v.bv_len,
-		res |= (unsigned long)v.iov_base | v.iov_len
+		res |= (unsigned long)v.iov_base | v.iov_len,
+		res |= v.bv_offset | v.bv_len
 	)
 	return res;
 }
@@ -1263,7 +1367,9 @@ unsigned long iov_iter_gap_alignment(const struct iov_iter *i)
 		(res |= (!res ? 0 : (unsigned long)v.bv_offset) |
 			(size != v.bv_len ? size : 0)),
 		(res |= (!res ? 0 : (unsigned long)v.iov_base) |
-			(size != v.iov_len ? size : 0))
+			(size != v.iov_len ? size : 0)),
+		(res |= (!res ? 0 : (unsigned long)v.bv_offset) |
+			(size != v.bv_len ? size : 0))
 		);
 	return res;
 }
@@ -1313,6 +1419,75 @@ static ssize_t pipe_get_pages(struct iov_iter *i,
 	return __pipe_get_pages(i, min(maxsize, capacity), pages, iter_head, start);
 }
 
+static ssize_t iter_xarray_copy_pages(struct page **pages, struct xarray *xa,
+				       pgoff_t index, unsigned int nr_pages)
+{
+	XA_STATE(xas, xa, index);
+	struct page *page;
+	unsigned int ret = 0;
+
+	rcu_read_lock();
+	for (page = xas_load(&xas); page; page = xas_next(&xas)) {
+		if (xas_retry(&xas, page))
+			continue;
+
+		/* Has the page moved or been split? */
+		if (unlikely(page != xas_reload(&xas))) {
+			xas_reset(&xas);
+			continue;
+		}
+
+		pages[ret] = find_subpage(page, xas.xa_index);
+		get_page(pages[ret]);
+		if (++ret == nr_pages)
+			break;
+	}
+	rcu_read_unlock();
+	return ret;
+}
+
+static ssize_t iter_xarray_get_pages(struct iov_iter *i,
+				     struct page **pages, size_t maxsize,
+				     unsigned maxpages, size_t *_start_offset)
+{
+	unsigned nr, offset;
+	pgoff_t index, count;
+	size_t size = maxsize, actual;
+	loff_t pos;
+
+	if (!size || !maxpages)
+		return 0;
+
+	pos = i->xarray_start + i->iov_offset;
+	index = pos >> PAGE_SHIFT;
+	offset = pos & ~PAGE_MASK;
+	*_start_offset = offset;
+
+	count = 1;
+	if (size > PAGE_SIZE - offset) {
+		size -= PAGE_SIZE - offset;
+		count += size >> PAGE_SHIFT;
+		size &= ~PAGE_MASK;
+		if (size)
+			count++;
+	}
+
+	if (count > maxpages)
+		count = maxpages;
+
+	nr = iter_xarray_copy_pages(pages, i->xarray, index, count);
+	if (nr == 0)
+		return 0;
+
+	actual = PAGE_SIZE * nr;
+	actual -= offset;
+	if (nr == count && size > 0) {
+		unsigned last_offset = (nr > 1) ? 0 : offset;
+		actual -= PAGE_SIZE - (last_offset + size);
+	}
+	return actual;
+}
+
 ssize_t iov_iter_get_pages(struct iov_iter *i,
 		   struct page **pages, size_t maxsize, unsigned maxpages,
 		   size_t *start)
@@ -1322,6 +1497,8 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
 
 	if (unlikely(iov_iter_is_pipe(i)))
 		return pipe_get_pages(i, pages, maxsize, maxpages, start);
+	if (unlikely(iov_iter_is_xarray(i)))
+		return iter_xarray_get_pages(i, pages, maxsize, maxpages, start);
 	if (unlikely(iov_iter_is_discard(i)))
 		return -EFAULT;
 
@@ -1348,7 +1525,8 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
 		return v.bv_len;
 	}),({
 		return -EFAULT;
-	})
+	}),
+	0
 	)
 	return 0;
 }
@@ -1392,6 +1570,51 @@ static ssize_t pipe_get_pages_alloc(struct iov_iter *i,
 	return n;
 }
 
+static ssize_t iter_xarray_get_pages_alloc(struct iov_iter *i,
+					   struct page ***pages, size_t maxsize,
+					   size_t *_start_offset)
+{
+	struct page **p;
+	unsigned nr, offset;
+	pgoff_t index, count;
+	size_t size = maxsize, actual;
+	loff_t pos;
+
+	if (!size)
+		return 0;
+
+	pos = i->xarray_start + i->iov_offset;
+	index = pos >> PAGE_SHIFT;
+	offset = pos & ~PAGE_MASK;
+	*_start_offset = offset;
+
+	count = 1;
+	if (size > PAGE_SIZE - offset) {
+		size -= PAGE_SIZE - offset;
+		count += size >> PAGE_SHIFT;
+		size &= ~PAGE_MASK;
+		if (size)
+			count++;
+	}
+
+	p = get_pages_array(count);
+	if (!p)
+		return -ENOMEM;
+	*pages = p;
+
+	nr = iter_xarray_copy_pages(p, i->xarray, index, count);
+	if (nr == 0)
+		return 0;
+
+	actual = PAGE_SIZE * nr;
+	actual -= offset;
+	if (nr == count && size > 0) {
+		unsigned last_offset = (nr > 1) ? 0 : offset;
+		actual -= PAGE_SIZE - (last_offset + size);
+	}
+	return actual;
+}
+
 ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
 		   struct page ***pages, size_t maxsize,
 		   size_t *start)
@@ -1403,6 +1626,8 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
 
 	if (unlikely(iov_iter_is_pipe(i)))
 		return pipe_get_pages_alloc(i, pages, maxsize, start);
+	if (unlikely(iov_iter_is_xarray(i)))
+		return iter_xarray_get_pages_alloc(i, pages, maxsize, start);
 	if (unlikely(iov_iter_is_discard(i)))
 		return -EFAULT;
 
@@ -1435,7 +1660,7 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
 		return v.bv_len;
 	}),({
 		return -EFAULT;
-	})
+	}), 0
 	)
 	return 0;
 }
@@ -1473,6 +1698,13 @@ size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
 				      v.iov_base, v.iov_len,
 				      sum, off);
 		off += v.iov_len;
+	}), ({
+		char *p = kmap_atomic(v.bv_page);
+		sum = csum_and_memcpy((to += v.bv_len) - v.bv_len,
+				      p + v.bv_offset, v.bv_len,
+				      sum, off);
+		kunmap_atomic(p);
+		off += v.bv_len;
 	})
 	)
 	*csum = sum;
@@ -1514,6 +1746,13 @@ bool csum_and_copy_from_iter_full(void *addr, size_t bytes, __wsum *csum,
 				      v.iov_base, v.iov_len,
 				      sum, off);
 		off += v.iov_len;
+	}), ({
+		char *p = kmap_atomic(v.bv_page);
+		sum = csum_and_memcpy((to += v.bv_len) - v.bv_len,
+				      p + v.bv_offset, v.bv_len,
+				      sum, off);
+		kunmap_atomic(p);
+		off += v.bv_len;
 	})
 	)
 	*csum = sum;
@@ -1559,6 +1798,13 @@ size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *csump,
 				     (from += v.iov_len) - v.iov_len,
 				     v.iov_len, sum, off);
 		off += v.iov_len;
+	}), ({
+		char *p = kmap_atomic(v.bv_page);
+		sum = csum_and_memcpy(p + v.bv_offset,
+				      (from += v.bv_len) - v.bv_len,
+				      v.bv_len, sum, off);
+		kunmap_atomic(p);
+		off += v.bv_len;
 	})
 	)
 	*csum = sum;
@@ -1608,6 +1854,21 @@ int iov_iter_npages(const struct iov_iter *i, int maxpages)
 		npages = pipe_space_for_user(iter_head, pipe->tail, pipe);
 		if (npages >= maxpages)
 			return maxpages;
+	} else if (unlikely(iov_iter_is_xarray(i))) {
+		unsigned offset;
+
+		offset = (i->xarray_start + i->iov_offset) & ~PAGE_MASK;
+
+		npages = 1;
+		if (size > PAGE_SIZE - offset) {
+			size -= PAGE_SIZE - offset;
+			npages += size >> PAGE_SHIFT;
+			size &= ~PAGE_MASK;
+			if (size)
+				npages++;
+		}
+		if (npages >= maxpages)
+			return maxpages;
 	} else iterate_all_kinds(i, size, v, ({
 		unsigned long p = (unsigned long)v.iov_base;
 		npages += DIV_ROUND_UP(p + v.iov_len, PAGE_SIZE)
@@ -1624,7 +1885,8 @@ int iov_iter_npages(const struct iov_iter *i, int maxpages)
 			- p / PAGE_SIZE;
 		if (npages >= maxpages)
 			return maxpages;
-	})
+	}),
+	0
 	)
 	return npages;
 }
@@ -1637,7 +1899,7 @@ const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags)
 		WARN_ON(1);
 		return NULL;
 	}
-	if (unlikely(iov_iter_is_discard(new)))
+	if (unlikely(iov_iter_is_discard(new) || iov_iter_is_xarray(new)))
 		return NULL;
 	if (iov_iter_is_bvec(new))
 		return new->bvec = kmemdup(new->bvec,
@@ -1842,7 +2104,12 @@ int iov_iter_for_each_range(struct iov_iter *i, size_t bytes,
 		kunmap(v.bv_page);
 		err;}), ({
 		w = v;
-		err = f(&w, context);})
+		err = f(&w, context);}), ({
+		w.iov_base = kmap(v.bv_page) + v.bv_offset;
+		w.iov_len = v.bv_len;
+		err = f(&w, context);
+		kunmap(v.bv_page);
+		err;})
 	)
 	return err;
 }

[PATCH 02/33] mm: Add an unlock function for PG_private_2/PG_fscache

[David Howells]

Add a function, unlock_page_private_2(), to unlock PG_private_2 analogous
to that of PG_lock.  Add a kerneldoc banner to that indicating the example
usage case.

A wrapper will need to be placed in the netfs header in the patch that adds
that.

[This implements a suggestion by Linus to not mix the terminology of
 PG_private_2 and PG_fscache in the mm core function]

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Linus Torvalds <torvalds@linux-foundation.org>
cc: Matthew Wilcox (Oracle) <willy@infradead.org>
cc: Alexander Viro <viro@zeniv.linux.org.uk>
cc: Christoph Hellwig <hch@lst.de>
cc: linux-mm@kvack.org
cc: linux-cachefs@redhat.com
cc: linux-afs@lists.infradead.org
cc: linux-nfs@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: ceph-devel@vger.kernel.org
cc: v9fs-developer@lists.sourceforge.net
cc: linux-fsdevel@vger.kernel.org
Link: https://lore.kernel.org/linux-fsdevel/1330473.1612974547@warthog.procyon.org.uk/
Link: https://lore.kernel.org/linux-fsdevel/CAHk-=wjgA-74ddehziVk=XAEMTKswPu1Yw4uaro1R3ibs27ztw@mail.gmail.com/
---

 include/linux/pagemap.h |    1 +
 mm/filemap.c            |   20 ++++++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index d5570deff400..365a28ece763 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -591,6 +591,7 @@ extern int __lock_page_async(struct page *page, struct wait_page_queue *wait);
 extern int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
 				unsigned int flags);
 extern void unlock_page(struct page *page);
+extern void unlock_page_private_2(struct page *page);
 
 /*
  * Return true if the page was successfully locked
diff --git a/mm/filemap.c b/mm/filemap.c
index 5c9d564317a5..7d321152d579 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1466,6 +1466,26 @@ void unlock_page(struct page *page)
 }
 EXPORT_SYMBOL(unlock_page);
 
+/**
+ * unlock_page_private_2 - Unlock a page that's locked with PG_private_2
+ * @page: The page
+ *
+ * Unlocks a page that's locked with PG_private_2 and wakes up sleepers in
+ * wait_on_page_private_2().
+ *
+ * This is, for example, used when a netfs page is being written to a local
+ * disk cache, thereby allowing writes to the cache for the same page to be
+ * serialised.
+ */
+void unlock_page_private_2(struct page *page)
+{
+	page = compound_head(page);
+	VM_BUG_ON_PAGE(!PagePrivate2(page), page);
+	clear_bit_unlock(PG_private_2, &page->flags);
+	wake_up_page_bit(page, PG_private_2);
+}
+EXPORT_SYMBOL(unlock_page_private_2);
+
 /**
  * end_page_writeback - end writeback against a page
  * @page: the page

[PATCH 03/33] mm: Implement readahead_control pageset expansion

[David Howells]

Provide a function, readahead_expand(), that expands the set of pages
specified by a readahead_control object to encompass a revised area with a
proposed size and length.

The proposed area must include all of the old area and may be expanded yet
more by this function so that the edges align on (transparent huge) page
boundaries as allocated.

The expansion will be cut short if a page already exists in either of the
areas being expanded into.  Note that any expansion made in such a case is
not rolled back.

This will be used by fscache so that reads can be expanded to cache granule
boundaries, thereby allowing whole granules to be stored in the cache, but
there are other potential users also.

Suggested-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Matthew Wilcox (Oracle) <willy@infradead.org>
cc: Alexander Viro <viro@zeniv.linux.org.uk>
cc: Christoph Hellwig <hch@lst.de>
cc: linux-mm@kvack.org
cc: linux-cachefs@redhat.com
cc: linux-afs@lists.infradead.org
cc: linux-nfs@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: ceph-devel@vger.kernel.org
cc: v9fs-developer@lists.sourceforge.net
cc: linux-fsdevel@vger.kernel.org
---

 include/linux/pagemap.h |    2 +
 mm/readahead.c          |   70 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 72 insertions(+)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 365a28ece763..d2786607d297 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -761,6 +761,8 @@ extern void __delete_from_page_cache(struct page *page, void *shadow);
 int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask);
 void delete_from_page_cache_batch(struct address_space *mapping,
 				  struct pagevec *pvec);
+void readahead_expand(struct readahead_control *ractl,
+		      loff_t new_start, size_t new_len);
 
 /*
  * Like add_to_page_cache_locked, but used to add newly allocated pages:
diff --git a/mm/readahead.c b/mm/readahead.c
index c5b0457415be..4446dada0bc2 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -638,3 +638,73 @@ SYSCALL_DEFINE3(readahead, int, fd, loff_t, offset, size_t, count)
 {
 	return ksys_readahead(fd, offset, count);
 }
+
+/**
+ * readahead_expand - Expand a readahead request
+ * @ractl: The request to be expanded
+ * @new_start: The revised start
+ * @new_len: The revised size of the request
+ *
+ * Attempt to expand a readahead request outwards from the current size to the
+ * specified size by inserting locked pages before and after the current window
+ * to increase the size to the new window.  This may involve the insertion of
+ * THPs, in which case the window may get expanded even beyond what was
+ * requested.
+ *
+ * The algorithm will stop if it encounters a conflicting page already in the
+ * pagecache and leave a smaller expansion than requested.
+ *
+ * The caller must check for this by examining the revised @ractl object for a
+ * different expansion than was requested.
+ */
+void readahead_expand(struct readahead_control *ractl,
+		      loff_t new_start, size_t new_len)
+{
+	struct address_space *mapping = ractl->mapping;
+	pgoff_t new_index, new_nr_pages;
+	gfp_t gfp_mask = readahead_gfp_mask(mapping);
+
+	new_index = new_start / PAGE_SIZE;
+
+	/* Expand the leading edge downwards */
+	while (ractl->_index > new_index) {
+		unsigned long index = ractl->_index - 1;
+		struct page *page = xa_load(&mapping->i_pages, index);
+
+		if (page && !xa_is_value(page))
+			return; /* Page apparently present */
+
+		page = __page_cache_alloc(gfp_mask);
+		if (!page)
+			return;
+		if (add_to_page_cache_lru(page, mapping, index, gfp_mask) < 0) {
+			put_page(page);
+			return;
+		}
+
+		ractl->_nr_pages++;
+		ractl->_index = page->index;
+	}
+
+	new_len += new_start - readahead_pos(ractl);
+	new_nr_pages = DIV_ROUND_UP(new_len, PAGE_SIZE);
+
+	/* Expand the trailing edge upwards */
+	while (ractl->_nr_pages < new_nr_pages) {
+		unsigned long index = ractl->_index + ractl->_nr_pages;
+		struct page *page = xa_load(&mapping->i_pages, index);
+
+		if (page && !xa_is_value(page))
+			return; /* Page apparently present */
+
+		page = __page_cache_alloc(gfp_mask);
+		if (!page)
+			return;
+		if (add_to_page_cache_lru(page, mapping, index, gfp_mask) < 0) {
+			put_page(page);
+			return;
+		}
+		ractl->_nr_pages++;
+	}
+}
+EXPORT_SYMBOL(readahead_expand);

[PATCH 04/33] vfs: Export rw_verify_area() for use by cachefiles

[David Howells]

Export rw_verify_area() for so that cachefiles can use it before issuing
call_read_iter() and call_write_iter() to effect async DIO operations
against the cache.  This is analogous to aio_read() and aio_write().

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Alexander Viro <viro@zeniv.linux.org.uk>
cc: Christoph Hellwig <hch@lst.de>
cc: Matthew Wilcox <willy@infradead.org>
cc: linux-mm@kvack.org
cc: linux-cachefs@redhat.com
cc: linux-afs@lists.infradead.org
cc: linux-nfs@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: ceph-devel@vger.kernel.org
cc: v9fs-developer@lists.sourceforge.net
cc: linux-fsdevel@vger.kernel.org
---

 fs/internal.h      |    5 -----
 fs/read_write.c    |    1 +
 include/linux/fs.h |    1 +
 3 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/fs/internal.h b/fs/internal.h
index 77c50befbfbe..92e686249c40 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -164,11 +164,6 @@ extern char *simple_dname(struct dentry *, char *, int);
 extern void dput_to_list(struct dentry *, struct list_head *);
 extern void shrink_dentry_list(struct list_head *);
 
-/*
- * read_write.c
- */
-extern int rw_verify_area(int, struct file *, const loff_t *, size_t);
-
 /*
  * pipe.c
  */
diff --git a/fs/read_write.c b/fs/read_write.c
index 75f764b43418..fe84e11245bd 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -400,6 +400,7 @@ int rw_verify_area(int read_write, struct file *file, const loff_t *ppos, size_t
 	return security_file_permission(file,
 				read_write == READ ? MAY_READ : MAY_WRITE);
 }
+EXPORT_SYMBOL(rw_verify_area);
 
 static ssize_t new_sync_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
 {
diff --git a/include/linux/fs.h b/include/linux/fs.h
index fd47deea7c17..493804856ab3 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2760,6 +2760,7 @@ extern int notify_change(struct dentry *, struct iattr *, struct inode **);
 extern int inode_permission(struct inode *, int);
 extern int generic_permission(struct inode *, int);
 extern int __check_sticky(struct inode *dir, struct inode *inode);
+extern int rw_verify_area(int, struct file *, const loff_t *, size_t);
 
 static inline bool execute_ok(struct inode *inode)
 {

[PATCH 05/33] netfs: Make a netfs helper module

[David Howells]

Make a netfs helper module to manage read request segmentation, caching
support and transparent huge page support on behalf of a network
filesystem.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
cc: Matthew Wilcox <willy@infradead.org>
cc: linux-mm@kvack.org
cc: linux-cachefs@redhat.com
cc: linux-afs@lists.infradead.org
cc: linux-nfs@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: ceph-devel@vger.kernel.org
cc: v9fs-developer@lists.sourceforge.net
cc: linux-fsdevel@vger.kernel.org
---

 fs/netfs/Kconfig |    8 ++++++++
 1 file changed, 8 insertions(+)
 create mode 100644 fs/netfs/Kconfig

diff --git a/fs/netfs/Kconfig b/fs/netfs/Kconfig
new file mode 100644
index 000000000000..2ebf90e6ca95
--- /dev/null
+++ b/fs/netfs/Kconfig
@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+config NETFS_SUPPORT
+	tristate "Support for network filesystem high-level I/O"
+	help
+	  This option enables support for network filesystems, including
+	  helpers for high-level buffered I/O, abstracting out read
+	  segmentation, local caching and transparent huge page support.

[PATCH 06/33] netfs, mm: Move PG_fscache helper funcs to linux/netfs.h

[David Howells]

Move the PG_fscache related helper funcs (such as SetPageFsCache()) to
linux/netfs.h rather than linux/fscache.h as the intention is to move to a
model where they're used by the network filesystem and the helper library,
but not by fscache/cachefiles itself.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Matthew Wilcox <willy@infradead.org>
cc: linux-mm@kvack.org
cc: linux-cachefs@redhat.com
cc: linux-afs@lists.infradead.org
cc: linux-nfs@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: ceph-devel@vger.kernel.org
cc: v9fs-developer@lists.sourceforge.net
cc: linux-fsdevel@vger.kernel.org
---

 include/linux/fscache.h |   11 +----------
 include/linux/netfs.h   |   25 +++++++++++++++++++++++++
 2 files changed, 26 insertions(+), 10 deletions(-)
 create mode 100644 include/linux/netfs.h

diff --git a/include/linux/fscache.h b/include/linux/fscache.h
index a1c928fe98e7..1f8dc72369ee 100644
--- a/include/linux/fscache.h
+++ b/include/linux/fscache.h
@@ -19,6 +19,7 @@
 #include <linux/pagemap.h>
 #include <linux/pagevec.h>
 #include <linux/list_bl.h>
+#include <linux/netfs.h>
 
 #if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
 #define fscache_available() (1)
@@ -29,16 +30,6 @@
 #endif
 
 
-/*
- * overload PG_private_2 to give us PG_fscache - this is used to indicate that
- * a page is currently backed by a local disk cache
- */
-#define PageFsCache(page)		PagePrivate2((page))
-#define SetPageFsCache(page)		SetPagePrivate2((page))
-#define ClearPageFsCache(page)		ClearPagePrivate2((page))
-#define TestSetPageFsCache(page)	TestSetPagePrivate2((page))
-#define TestClearPageFsCache(page)	TestClearPagePrivate2((page))
-
 /* pattern used to fill dead space in an index entry */
 #define FSCACHE_INDEX_DEADFILL_PATTERN 0x79
 
diff --git a/include/linux/netfs.h b/include/linux/netfs.h
new file mode 100644
index 000000000000..b3d869ec7d2a
--- /dev/null
+++ b/include/linux/netfs.h
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Network filesystem support services.
+ *
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * for a description of the network filesystem interface declared here.
+ */
+
+#ifndef _LINUX_NETFS_H
+#define _LINUX_NETFS_H
+
+#include <linux/pagemap.h>
+
+/*
+ * Overload PG_private_2 to give us PG_fscache - this is used to indicate that
+ * a page is currently backed by a local disk cache
+ */
+#define PageFsCache(page)		PagePrivate2((page))
+#define SetPageFsCache(page)		SetPagePrivate2((page))
+#define ClearPageFsCache(page)		ClearPagePrivate2((page))
+#define TestSetPageFsCache(page)	TestSetPagePrivate2((page))
+#define TestClearPageFsCache(page)	TestClearPagePrivate2((page))
+
+#endif /* _LINUX_NETFS_H */

[PATCH 07/33] netfs, mm: Add unlock_page_fscache() and wait_on_page_fscache()

[David Howells]

Add unlock_page_fscache() as an alias of unlock_page_private_2().  This
allows a page 'locked' with PG_fscache to be unlocked.

Add wait_on_page_fscache() to wait for PG_fscache to be unlocked.

[Linus suggested putting the fscache-themed functions into the
 caching-specific headers rather than pagemap.h]

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Linus Torvalds <torvalds@linux-foundation.org>
cc: Matthew Wilcox <willy@infradead.org>
cc: linux-mm@kvack.org
cc: linux-cachefs@redhat.com
cc: linux-afs@lists.infradead.org
cc: linux-nfs@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: ceph-devel@vger.kernel.org
cc: v9fs-developer@lists.sourceforge.net
cc: linux-fsdevel@vger.kernel.org
Link: https://lore.kernel.org/linux-fsdevel/1330473.1612974547@warthog.procyon.org.uk/
Link: https://lore.kernel.org/linux-fsdevel/CAHk-=wjgA-74ddehziVk=XAEMTKswPu1Yw4uaro1R3ibs27ztw@mail.gmail.com/
---

 include/linux/netfs.h |   29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index b3d869ec7d2a..f69703543788 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -22,4 +22,33 @@
 #define TestSetPageFsCache(page)	TestSetPagePrivate2((page))
 #define TestClearPageFsCache(page)	TestClearPagePrivate2((page))
 
+/**
+ * unlock_page_fscache - Unlock a page that's locked with PG_fscache
+ * @page: The page
+ *
+ * Unlocks a page that's locked with PG_fscache and wakes up sleepers in
+ * wait_on_page_fscache().  This page bit is used by the netfs helpers when a
+ * netfs page is being written to a local disk cache, thereby allowing writes
+ * to the cache for the same page to be serialised.
+ */
+static inline void unlock_page_fscache(struct page *page)
+{
+	unlock_page_private_2(page);
+}
+
+/**
+ * wait_on_page_fscache - Wait for PG_fscache to be cleared on a page
+ * @page: The page
+ *
+ * Wait for the PG_fscache (PG_private_2) page bit to be removed from a page.
+ * This is, for example, used to handle a netfs page being written to a local
+ * disk cache, thereby allowing writes to the cache for the same page to be
+ * serialised.
+ */
+static inline void wait_on_page_fscache(struct page *page)
+{
+	if (PageFsCache(page))
+		wait_on_page_bit(compound_head(page), PG_fscache);
+}
+
 #endif /* _LINUX_NETFS_H */

[PATCH 08/33] netfs: Provide readahead and readpage netfs helpers

[David Howells]

Add a pair of helper functions:

 (*) netfs_readahead()
 (*) netfs_readpage()

to do the work of handling a readahead or a readpage, where the page(s)
that form part of the request may be split between the local cache, the
server or just require clearing, and may be single pages and transparent
huge pages.  This is all handled within the helper.

Note that while both will read from the cache if there is data present,
only netfs_readahead() will expand the request beyond what it was asked to
do, and only netfs_readahead() will write back to the cache.

netfs_readpage(), on the other hand, is synchronous and only fetches the
page (which might be a THP) it is asked for.

The netfs gives the helper parameters from the VM, the cache cookie it
wants to use (or NULL) and a table of operations (only one of which is
mandatory):

 (*) expand_readahead() [optional]

     Called to allow the netfs to request an expansion of a readahead
     request to meet its own alignment requirements.  This is done by
     changing rreq->start and rreq->len.

 (*) clamp_length() [optional]

     Called to allow the netfs to cut down a subrequest to meet its own
     boundary requirements.  If it does this, the helper will generate
     additional subrequests until the full request is satisfied.

 (*) is_still_valid() [optional]

     Called to find out if the data just read from the cache has been
     invalidated and must be reread from the server.

 (*) issue_op() [required]

     Called to ask the netfs to issue a read to the server.  The subrequest
     describes the read.  The read request holds information about the file
     being accessed.

     The netfs can cache information in rreq->netfs_priv.

     Upon completion, the netfs should set the error, transferred and can
     also set FSCACHE_SREQ_CLEAR_TAIL and then call
     fscache_subreq_terminated().

 (*) done() [optional]

     Called after the pages have been unlocked.  The read request is still
     pinning the file and mapping and may still be pinning pages with
     PG_fscache.  rreq->error indicates any error that has been
     accumulated.

 (*) cleanup() [optional]

     Called when the helper is disposing of a finished read request.  This
     allows the netfs to clear rreq->netfs_priv.

Netfs support is enabled with CONFIG_NETFS_SUPPORT=y.  It will be built
even if CONFIG_FSCACHE=n and in this case much of it should be optimised
away, allowing the filesystem to use it even when caching is disabled.

changes:
 - Folded in a kerneldoc comment fix
 - Folded in a fix for the error handling in the case that ENOMEM occurs.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
cc: Matthew Wilcox <willy@infradead.org>
cc: linux-mm@kvack.org
cc: linux-cachefs@redhat.com
cc: linux-afs@lists.infradead.org
cc: linux-nfs@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: ceph-devel@vger.kernel.org
cc: v9fs-developer@lists.sourceforge.net
cc: linux-fsdevel@vger.kernel.org
---

 fs/Kconfig             |    1 
 fs/Makefile            |    1 
 fs/netfs/Makefile      |    6 
 fs/netfs/internal.h    |   61 ++++
 fs/netfs/read_helper.c |  717 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/netfs.h  |   82 +++++
 6 files changed, 868 insertions(+)
 create mode 100644 fs/netfs/Makefile
 create mode 100644 fs/netfs/internal.h
 create mode 100644 fs/netfs/read_helper.c

diff --git a/fs/Kconfig b/fs/Kconfig
index aa4c12282301..a8ab2802c52e 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -125,6 +125,7 @@ source "fs/overlayfs/Kconfig"
 
 menu "Caches"
 
+source "fs/netfs/Kconfig"
 source "fs/fscache/Kconfig"
 source "fs/cachefiles/Kconfig"
 
diff --git a/fs/Makefile b/fs/Makefile
index 999d1a23f036..e922c3bc0a43 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -68,6 +68,7 @@ obj-$(CONFIG_PROFILING)		+= dcookies.o
 obj-$(CONFIG_DLM)		+= dlm/
  
 # Do not add any filesystems before this line
+obj-$(CONFIG_NETFS_SUPPORT)	+= netfs/
 obj-$(CONFIG_FSCACHE)		+= fscache/
 obj-$(CONFIG_REISERFS_FS)	+= reiserfs/
 obj-$(CONFIG_EXT4_FS)		+= ext4/
diff --git a/fs/netfs/Makefile b/fs/netfs/Makefile
new file mode 100644
index 000000000000..4b4eff2ba369
--- /dev/null
+++ b/fs/netfs/Makefile
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0
+
+netfs-y := \
+	read_helper.o
+
+obj-$(CONFIG_NETFS_SUPPORT) := netfs.o
diff --git a/fs/netfs/internal.h b/fs/netfs/internal.h
new file mode 100644
index 000000000000..ee665c0e7dc8
--- /dev/null
+++ b/fs/netfs/internal.h
@@ -0,0 +1,61 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Internal definitions for network filesystem support
+ *
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#ifdef pr_fmt
+#undef pr_fmt
+#endif
+
+#define pr_fmt(fmt) "netfs: " fmt
+
+/*
+ * read_helper.c
+ */
+extern unsigned int netfs_debug;
+
+#define netfs_stat(x) do {} while(0)
+#define netfs_stat_d(x) do {} while(0)
+
+/*****************************************************************************/
+/*
+ * debug tracing
+ */
+#define dbgprintk(FMT, ...) \
+	printk("[%-6.6s] "FMT"\n", current->comm, ##__VA_ARGS__)
+
+#define kenter(FMT, ...) dbgprintk("==> %s("FMT")", __func__, ##__VA_ARGS__)
+#define kleave(FMT, ...) dbgprintk("<== %s()"FMT"", __func__, ##__VA_ARGS__)
+#define kdebug(FMT, ...) dbgprintk(FMT, ##__VA_ARGS__)
+
+#ifdef __KDEBUG
+#define _enter(FMT, ...) kenter(FMT, ##__VA_ARGS__)
+#define _leave(FMT, ...) kleave(FMT, ##__VA_ARGS__)
+#define _debug(FMT, ...) kdebug(FMT, ##__VA_ARGS__)
+
+#elif defined(CONFIG_NETFS_DEBUG)
+#define _enter(FMT, ...)			\
+do {						\
+	if (netfs_debug)			\
+		kenter(FMT, ##__VA_ARGS__);	\
+} while (0)
+
+#define _leave(FMT, ...)			\
+do {						\
+	if (netfs_debug)			\
+		kleave(FMT, ##__VA_ARGS__);	\
+} while (0)
+
+#define _debug(FMT, ...)			\
+do {						\
+	if (netfs_debug)			\
+		kdebug(FMT, ##__VA_ARGS__);	\
+} while (0)
+
+#else
+#define _enter(FMT, ...) no_printk("==> %s("FMT")", __func__, ##__VA_ARGS__)
+#define _leave(FMT, ...) no_printk("<== %s()"FMT"", __func__, ##__VA_ARGS__)
+#define _debug(FMT, ...) no_printk(FMT, ##__VA_ARGS__)
+#endif
diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c
new file mode 100644
index 000000000000..a35bd29928fa
--- /dev/null
+++ b/fs/netfs/read_helper.c
@@ -0,0 +1,717 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Network filesystem high-level read support.
+ *
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/module.h>
+#include <linux/export.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/slab.h>
+#include <linux/uio.h>
+#include <linux/sched/mm.h>
+#include <linux/task_io_accounting_ops.h>
+#include <linux/netfs.h>
+#include "internal.h"
+
+MODULE_DESCRIPTION("Network fs support");
+MODULE_AUTHOR("Red Hat, Inc.");
+MODULE_LICENSE("GPL");
+
+unsigned netfs_debug;
+module_param_named(debug, netfs_debug, uint, S_IWUSR | S_IRUGO);
+MODULE_PARM_DESC(netfs_debug, "Netfs support debugging mask");
+
+static void netfs_rreq_work(struct work_struct *);
+static void __netfs_put_subrequest(struct netfs_read_subrequest *);
+
+static void netfs_put_subrequest(struct netfs_read_subrequest *subreq)
+{
+	if (refcount_dec_and_test(&subreq->usage))
+		__netfs_put_subrequest(subreq);
+}
+
+static struct netfs_read_request *netfs_alloc_read_request(
+	const struct netfs_read_request_ops *ops, void *netfs_priv,
+	struct file *file)
+{
+	struct netfs_read_request *rreq;
+
+	rreq = kzalloc(sizeof(struct netfs_read_request), GFP_KERNEL);
+	if (rreq) {
+		rreq->netfs_ops	= ops;
+		rreq->netfs_priv = netfs_priv;
+		rreq->inode	= file_inode(file);
+		rreq->i_size	= i_size_read(rreq->inode);
+		INIT_LIST_HEAD(&rreq->subrequests);
+		INIT_WORK(&rreq->work, netfs_rreq_work);
+		refcount_set(&rreq->usage, 1);
+		__set_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags);
+		ops->init_rreq(rreq, file);
+	}
+
+	return rreq;
+}
+
+static void netfs_get_read_request(struct netfs_read_request *rreq)
+{
+	refcount_inc(&rreq->usage);
+}
+
+static void netfs_rreq_clear_subreqs(struct netfs_read_request *rreq)
+{
+	struct netfs_read_subrequest *subreq;
+
+	while (!list_empty(&rreq->subrequests)) {
+		subreq = list_first_entry(&rreq->subrequests,
+					  struct netfs_read_subrequest, rreq_link);
+		list_del(&subreq->rreq_link);
+		netfs_put_subrequest(subreq);
+	}
+}
+
+static void netfs_free_read_request(struct work_struct *work)
+{
+	struct netfs_read_request *rreq =
+		container_of(work, struct netfs_read_request, work);
+	netfs_rreq_clear_subreqs(rreq);
+	if (rreq->netfs_priv)
+		rreq->netfs_ops->cleanup(rreq->mapping, rreq->netfs_priv);
+	kfree(rreq);
+}
+
+static void netfs_put_read_request(struct netfs_read_request *rreq)
+{
+	if (refcount_dec_and_test(&rreq->usage)) {
+		if (in_softirq()) {
+			rreq->work.func = netfs_free_read_request;
+			if (!queue_work(system_unbound_wq, &rreq->work))
+				BUG();
+		} else {
+			netfs_free_read_request(&rreq->work);
+		}
+	}
+}
+
+/*
+ * Allocate and partially initialise an I/O request structure.
+ */
+static struct netfs_read_subrequest *netfs_alloc_subrequest(
+	struct netfs_read_request *rreq)
+{
+	struct netfs_read_subrequest *subreq;
+
+	subreq = kzalloc(sizeof(struct netfs_read_subrequest), GFP_KERNEL);
+	if (subreq) {
+		INIT_LIST_HEAD(&subreq->rreq_link);
+		refcount_set(&subreq->usage, 2);
+		subreq->rreq = rreq;
+		netfs_get_read_request(rreq);
+	}
+
+	return subreq;
+}
+
+static void netfs_get_read_subrequest(struct netfs_read_subrequest *subreq)
+{
+	refcount_inc(&subreq->usage);
+}
+
+static void __netfs_put_subrequest(struct netfs_read_subrequest *subreq)
+{
+	netfs_put_read_request(subreq->rreq);
+	kfree(subreq);
+}
+
+/*
+ * Clear the unread part of an I/O request.
+ */
+static void netfs_clear_unread(struct netfs_read_subrequest *subreq)
+{
+	struct iov_iter iter;
+
+	iov_iter_xarray(&iter, WRITE, &subreq->rreq->mapping->i_pages,
+			subreq->start + subreq->transferred,
+			subreq->len   - subreq->transferred);
+	iov_iter_zero(iov_iter_count(&iter), &iter);
+}
+
+/*
+ * Fill a subrequest region with zeroes.
+ */
+static void netfs_fill_with_zeroes(struct netfs_read_request *rreq,
+				   struct netfs_read_subrequest *subreq)
+{
+	__set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
+	netfs_subreq_terminated(subreq, 0);
+}
+
+/*
+ * Ask the netfs to issue a read request to the server for us.
+ *
+ * The netfs is expected to read from subreq->pos + subreq->transferred to
+ * subreq->pos + subreq->len - 1.  It may not backtrack and write data into the
+ * buffer prior to the transferred point as it might clobber dirty data
+ * obtained from the cache.
+ *
+ * Alternatively, the netfs is allowed to indicate one of two things:
+ *
+ * - NETFS_SREQ_SHORT_READ: A short read - it will get called again to try and
+ *   make progress.
+ *
+ * - NETFS_SREQ_CLEAR_TAIL: A short read - the rest of the buffer will be
+ *   cleared.
+ */
+static void netfs_read_from_server(struct netfs_read_request *rreq,
+				   struct netfs_read_subrequest *subreq)
+{
+	rreq->netfs_ops->issue_op(subreq);
+}
+
+/*
+ * Release those waiting.
+ */
+static void netfs_rreq_completed(struct netfs_read_request *rreq)
+{
+	netfs_rreq_clear_subreqs(rreq);
+	netfs_put_read_request(rreq);
+}
+
+/*
+ * Unlock the pages in a read operation.  We need to set PG_fscache on any
+ * pages we're going to write back before we unlock them.
+ */
+static void netfs_rreq_unlock(struct netfs_read_request *rreq)
+{
+	struct netfs_read_subrequest *subreq;
+	struct page *page;
+	unsigned int iopos, account = 0;
+	pgoff_t start_page = rreq->start / PAGE_SIZE;
+	pgoff_t last_page = ((rreq->start + rreq->len) / PAGE_SIZE) - 1;
+	bool subreq_failed = false;
+	int i;
+
+	XA_STATE(xas, &rreq->mapping->i_pages, start_page);
+
+	if (test_bit(NETFS_RREQ_FAILED, &rreq->flags)) {
+		__clear_bit(NETFS_RREQ_WRITE_TO_CACHE, &rreq->flags);
+		list_for_each_entry(subreq, &rreq->subrequests, rreq_link) {
+			__clear_bit(NETFS_SREQ_WRITE_TO_CACHE, &subreq->flags);
+		}
+	}
+
+	/* Walk through the pagecache and the I/O request lists simultaneously.
+	 * We may have a mixture of cached and uncached sections and we only
+	 * really want to write out the uncached sections.  This is slightly
+	 * complicated by the possibility that we might have huge pages with a
+	 * mixture inside.
+	 */
+	subreq = list_first_entry(&rreq->subrequests,
+				  struct netfs_read_subrequest, rreq_link);
+	iopos = 0;
+	subreq_failed = (subreq->error < 0);
+
+	rcu_read_lock();
+	xas_for_each(&xas, page, last_page) {
+		unsigned int pgpos = (page->index - start_page) * PAGE_SIZE;
+		unsigned int pgend = pgpos + thp_size(page);
+		bool pg_failed = false;
+
+		for (;;) {
+			if (!subreq) {
+				pg_failed = true;
+				break;
+			}
+			if (test_bit(NETFS_SREQ_WRITE_TO_CACHE, &subreq->flags))
+				SetPageFsCache(page);
+			pg_failed |= subreq_failed;
+			if (pgend < iopos + subreq->len)
+				break;
+
+			account += subreq->transferred;
+			iopos += subreq->len;
+			if (!list_is_last(&subreq->rreq_link, &rreq->subrequests)) {
+				subreq = list_next_entry(subreq, rreq_link);
+				subreq_failed = (subreq->error < 0);
+			} else {
+				subreq = NULL;
+				subreq_failed = false;
+			}
+			if (pgend == iopos)
+				break;
+		}
+
+		if (!pg_failed) {
+			for (i = 0; i < thp_nr_pages(page); i++)
+				flush_dcache_page(page);
+			SetPageUptodate(page);
+		}
+
+		if (!test_bit(NETFS_RREQ_DONT_UNLOCK_PAGES, &rreq->flags)) {
+			if (page->index == rreq->no_unlock_page &&
+			    test_bit(NETFS_RREQ_NO_UNLOCK_PAGE, &rreq->flags))
+				_debug("no unlock");
+			else
+				unlock_page(page);
+		}
+	}
+	rcu_read_unlock();
+
+	task_io_account_read(account);
+	if (rreq->netfs_ops->done)
+		rreq->netfs_ops->done(rreq);
+}
+
+/*
+ * Handle a short read.
+ */
+static void netfs_rreq_short_read(struct netfs_read_request *rreq,
+				  struct netfs_read_subrequest *subreq)
+{
+	__clear_bit(NETFS_SREQ_SHORT_READ, &subreq->flags);
+	__set_bit(NETFS_SREQ_SEEK_DATA_READ, &subreq->flags);
+
+	netfs_get_read_subrequest(subreq);
+	atomic_inc(&rreq->nr_rd_ops);
+	netfs_read_from_server(rreq, subreq);
+}
+
+/*
+ * Resubmit any short or failed operations.  Returns true if we got the rreq
+ * ref back.
+ */
+static bool netfs_rreq_perform_resubmissions(struct netfs_read_request *rreq)
+{
+	struct netfs_read_subrequest *subreq;
+
+	WARN_ON(in_softirq());
+
+	/* We don't want terminating submissions trying to wake us up whilst
+	 * we're still going through the list.
+	 */
+	atomic_inc(&rreq->nr_rd_ops);
+
+	__clear_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags);
+	list_for_each_entry(subreq, &rreq->subrequests, rreq_link) {
+		if (subreq->error) {
+			if (subreq->source != NETFS_READ_FROM_CACHE)
+				break;
+			subreq->source = NETFS_DOWNLOAD_FROM_SERVER;
+			subreq->error = 0;
+			netfs_get_read_subrequest(subreq);
+			atomic_inc(&rreq->nr_rd_ops);
+			netfs_read_from_server(rreq, subreq);
+		} else if (test_bit(NETFS_SREQ_SHORT_READ, &subreq->flags)) {
+			netfs_rreq_short_read(rreq, subreq);
+		}
+	}
+
+	/* If we decrement nr_rd_ops to 0, the usage ref belongs to us. */
+	if (atomic_dec_and_test(&rreq->nr_rd_ops))
+		return true;
+
+	wake_up_var(&rreq->nr_rd_ops);
+	return false;
+}
+
+/*
+ * Assess the state of a read request and decide what to do next.
+ *
+ * Note that we could be in an ordinary kernel thread, on a workqueue or in
+ * softirq context at this point.  We inherit a ref from the caller.
+ */
+static void netfs_rreq_assess(struct netfs_read_request *rreq)
+{
+again:
+	if (!test_bit(NETFS_RREQ_FAILED, &rreq->flags) &&
+	    test_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags)) {
+		if (netfs_rreq_perform_resubmissions(rreq))
+			goto again;
+		return;
+	}
+
+	netfs_rreq_unlock(rreq);
+
+	clear_bit_unlock(NETFS_RREQ_IN_PROGRESS, &rreq->flags);
+	wake_up_bit(&rreq->flags, NETFS_RREQ_IN_PROGRESS);
+
+	netfs_rreq_completed(rreq);
+}
+
+static void netfs_rreq_work(struct work_struct *work)
+{
+	struct netfs_read_request *rreq =
+		container_of(work, struct netfs_read_request, work);
+	netfs_rreq_assess(rreq);
+}
+
+/*
+ * Handle the completion of all outstanding I/O operations on a read request.
+ * We inherit a ref from the caller.
+ */
+static void netfs_rreq_terminated(struct netfs_read_request *rreq)
+{
+	if (test_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags) &&
+	    in_softirq()) {
+		if (!queue_work(system_unbound_wq, &rreq->work))
+			BUG();
+	} else {
+		netfs_rreq_assess(rreq);
+	}
+}
+
+/**
+ * netfs_subreq_terminated - Note the termination of an I/O operation.
+ * @subreq: The I/O request that has terminated.
+ * @transferred_or_error: The amount of data transferred or an error code.
+ *
+ * This tells the read helper that a contributory I/O operation has terminated,
+ * one way or another, and that it should integrate the results.
+ *
+ * The caller indicates in @transferred_or_error the outcome of the operation,
+ * supplying a positive value to indicate the number of bytes transferred, 0 to
+ * indicate a failure to transfer anything that should be retried or a negative
+ * error code.  The helper will look after reissuing I/O operations as
+ * appropriate and writing downloaded data to the cache.
+ *
+ * This may be called from a softirq handler, so we want to avoid taking the
+ * spinlock if we can.
+ */
+void netfs_subreq_terminated(struct netfs_read_subrequest *subreq,
+			     ssize_t transferred_or_error)
+{
+	struct netfs_read_request *rreq = subreq->rreq;
+	int u;
+
+	_enter("[%u]{%llx,%lx},%zd",
+	       subreq->debug_index, subreq->start, subreq->flags,
+	       transferred_or_error);
+
+	if (IS_ERR_VALUE(transferred_or_error)) {
+		subreq->error = transferred_or_error;
+		goto failed;
+	}
+
+	if (WARN_ON(transferred_or_error > subreq->len - subreq->transferred))
+		transferred_or_error = subreq->len - subreq->transferred;
+
+	subreq->error = 0;
+	subreq->transferred += transferred_or_error;
+	if (subreq->transferred < subreq->len)
+		goto incomplete;
+
+complete:
+	__clear_bit(NETFS_SREQ_NO_PROGRESS, &subreq->flags);
+	if (test_bit(NETFS_SREQ_WRITE_TO_CACHE, &subreq->flags))
+		set_bit(NETFS_RREQ_WRITE_TO_CACHE, &rreq->flags);
+
+out:
+	/* If we decrement nr_rd_ops to 0, the ref belongs to us. */
+	u = atomic_dec_return(&rreq->nr_rd_ops);
+	if (u == 0)
+		netfs_rreq_terminated(rreq);
+	else if (u == 1)
+		wake_up_var(&rreq->nr_rd_ops);
+
+	netfs_put_subrequest(subreq);
+	return;
+
+incomplete:
+	if (test_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags)) {
+		netfs_clear_unread(subreq);
+		subreq->transferred = subreq->len;
+		goto complete;
+	}
+
+	if (transferred_or_error == 0) {
+		if (__test_and_set_bit(NETFS_SREQ_NO_PROGRESS, &subreq->flags)) {
+			subreq->error = -ENODATA;
+			goto failed;
+		}
+	} else {
+		__clear_bit(NETFS_SREQ_NO_PROGRESS, &subreq->flags);
+	}
+
+	__set_bit(NETFS_SREQ_SHORT_READ, &subreq->flags);
+	set_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags);
+	goto out;
+
+failed:
+	if (subreq->source == NETFS_READ_FROM_CACHE) {
+		set_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags);
+	} else {
+		set_bit(NETFS_RREQ_FAILED, &rreq->flags);
+		rreq->error = subreq->error;
+	}
+	goto out;
+}
+EXPORT_SYMBOL(netfs_subreq_terminated);
+
+static enum netfs_read_source netfs_cache_prepare_read(struct netfs_read_subrequest *subreq,
+						       loff_t i_size)
+{
+	struct netfs_read_request *rreq = subreq->rreq;
+
+	if (subreq->start >= rreq->i_size)
+		return NETFS_FILL_WITH_ZEROES;
+	return NETFS_DOWNLOAD_FROM_SERVER;
+}
+
+/*
+ * Work out what sort of subrequest the next one will be.
+ */
+static enum netfs_read_source
+netfs_rreq_prepare_read(struct netfs_read_request *rreq,
+			struct netfs_read_subrequest *subreq)
+{
+	enum netfs_read_source source;
+
+	_enter("%llx-%llx,%llx", subreq->start, subreq->start + subreq->len, rreq->i_size);
+
+	source = netfs_cache_prepare_read(subreq, rreq->i_size);
+	if (source == NETFS_INVALID_READ)
+		goto out;
+
+	if (source == NETFS_DOWNLOAD_FROM_SERVER) {
+		/* Call out to the netfs to let it shrink the request to fit
+		 * its own I/O sizes and boundaries.  If it shinks it here, it
+		 * will be called again to make simultaneous calls; if it wants
+		 * to make serial calls, it can indicate a short read and then
+		 * we will call it again.
+		 */
+		if (subreq->len > rreq->i_size - subreq->start)
+			subreq->len = rreq->i_size - subreq->start;
+
+		if (rreq->netfs_ops->clamp_length &&
+		    !rreq->netfs_ops->clamp_length(subreq)) {
+			source = NETFS_INVALID_READ;
+			goto out;
+		}
+	}
+
+	if (WARN_ON(subreq->len == 0))
+		source = NETFS_INVALID_READ;
+
+out:
+	subreq->source = source;
+	return source;
+}
+
+/*
+ * Slice off a piece of a read request and submit an I/O request for it.
+ */
+static bool netfs_rreq_submit_slice(struct netfs_read_request *rreq,
+				    unsigned int *_debug_index)
+{
+	struct netfs_read_subrequest *subreq;
+	enum netfs_read_source source;
+
+	subreq = netfs_alloc_subrequest(rreq);
+	if (!subreq)
+		return false;
+
+	subreq->debug_index	= (*_debug_index)++;
+	subreq->start		= rreq->start + rreq->submitted;
+	subreq->len		= rreq->len   - rreq->submitted;
+
+	_debug("slice %llx,%zx,%zx", subreq->start, subreq->len, rreq->submitted);
+	list_add_tail(&subreq->rreq_link, &rreq->subrequests);
+
+	/* Call out to the cache to find out what it can do with the remaining
+	 * subset.  It tells us in subreq->flags what it decided should be done
+	 * and adjusts subreq->len down if the subset crosses a cache boundary.
+	 *
+	 * Then when we hand the subset, it can choose to take a subset of that
+	 * (the starts must coincide), in which case, we go around the loop
+	 * again and ask it to download the next piece.
+	 */
+	source = netfs_rreq_prepare_read(rreq, subreq);
+	if (source == NETFS_INVALID_READ)
+		goto subreq_failed;
+
+	atomic_inc(&rreq->nr_rd_ops);
+
+	rreq->submitted += subreq->len;
+
+	switch (source) {
+	case NETFS_FILL_WITH_ZEROES:
+		netfs_fill_with_zeroes(rreq, subreq);
+		break;
+	case NETFS_DOWNLOAD_FROM_SERVER:
+		netfs_read_from_server(rreq, subreq);
+		break;
+	default:
+		BUG();
+	}
+
+	return true;
+
+subreq_failed:
+	rreq->error = subreq->error;
+	netfs_put_subrequest(subreq);
+	return false;
+}
+
+static void netfs_rreq_expand(struct netfs_read_request *rreq,
+			      struct readahead_control *ractl)
+{
+	/* Give the netfs a chance to change the request parameters.  The
+	 * resultant request must contain the original region.
+	 */
+	if (rreq->netfs_ops->expand_readahead)
+		rreq->netfs_ops->expand_readahead(rreq);
+
+	/* Expand the request if the cache wants it to start earlier.  Note
+	 * that the expansion may get further extended if the VM wishes to
+	 * insert THPs and the preferred start and/or end wind up in the middle
+	 * of THPs.
+	 *
+	 * If this is the case, however, the THP size should be an integer
+	 * multiple of the cache granule size, so we get a whole number of
+	 * granules to deal with.
+	 */
+	if (rreq->start  != readahead_pos(ractl) ||
+	    rreq->len != readahead_length(ractl)) {
+		readahead_expand(ractl, rreq->start, rreq->len);
+		rreq->start  = readahead_pos(ractl);
+		rreq->len = readahead_length(ractl);
+	}
+}
+
+/**
+ * netfs_readahead - Helper to manage a read request
+ * @ractl: The description of the readahead request
+ * @ops: The network filesystem's operations for the helper to use
+ * @netfs_priv: Private netfs data to be retained in the request
+ *
+ * Fulfil a readahead request by drawing data from the cache if possible, or
+ * the netfs if not.  Space beyond the EOF is zero-filled.  Multiple I/O
+ * requests from different sources will get munged together.  If necessary, the
+ * readahead window can be expanded in either direction to a more convenient
+ * alighment for RPC efficiency or to make storage in the cache feasible.
+ *
+ * The calling netfs must provide a table of operations, only one of which,
+ * issue_op, is mandatory.  It may also be passed a private token, which will
+ * be retained in rreq->netfs_priv and will be cleaned up by ops->cleanup().
+ *
+ * This is usable whether or not caching is enabled.
+ */
+void netfs_readahead(struct readahead_control *ractl,
+		     const struct netfs_read_request_ops *ops,
+		     void *netfs_priv)
+{
+	struct netfs_read_request *rreq;
+	struct page *page;
+	unsigned int debug_index = 0;
+
+	_enter("%lx,%x", readahead_index(ractl), readahead_count(ractl));
+
+	if (readahead_count(ractl) == 0)
+		goto cleanup;
+
+	rreq = netfs_alloc_read_request(ops, netfs_priv, ractl->file);
+	if (!rreq)
+		goto cleanup;
+	rreq->mapping	= ractl->mapping;
+	rreq->start	= readahead_pos(ractl);
+	rreq->len	= readahead_length(ractl);
+
+	netfs_rreq_expand(rreq, ractl);
+
+	atomic_set(&rreq->nr_rd_ops, 1);
+	do {
+		if (!netfs_rreq_submit_slice(rreq, &debug_index))
+			break;
+
+	} while (rreq->submitted < rreq->len);
+
+	if (rreq->submitted == 0) {
+		netfs_put_read_request(rreq);
+		return;
+	}
+
+	// TODO: If we didn't submit enough readage, we need to try punting to
+	// a work queue.
+
+	while ((page = readahead_page(ractl)))
+		put_page(page);
+
+	/* If we decrement nr_rd_ops to 0, the ref belongs to us. */
+	if (atomic_dec_and_test(&rreq->nr_rd_ops))
+		netfs_rreq_assess(rreq);
+	return;
+
+cleanup:
+	if (netfs_priv)
+		ops->cleanup(ractl->mapping, netfs_priv);
+	return;
+}
+EXPORT_SYMBOL(netfs_readahead);
+
+/**
+ * netfs_page - Helper to manage a readpage request
+ * @file: The file to read from
+ * @page: The page to read
+ * @ops: The network filesystem's operations for the helper to use
+ * @netfs_priv: Private netfs data to be retained in the request
+ *
+ * Fulfil a readpage request by drawing data from the cache if possible, or the
+ * netfs if not.  Space beyond the EOF is zero-filled.  Multiple I/O requests
+ * from different sources will get munged together.
+ *
+ * The calling netfs must provide a table of operations, only one of which,
+ * issue_op, is mandatory.  It may also be passed a private token, which will
+ * be retained in rreq->netfs_priv and will be cleaned up by ops->cleanup().
+ *
+ * This is usable whether or not caching is enabled.
+ */
+int netfs_readpage(struct file *file,
+		   struct page *page,
+		   const struct netfs_read_request_ops *ops,
+		   void *netfs_priv)
+{
+	struct netfs_read_request *rreq;
+	unsigned int debug_index = 0;
+	int ret;
+
+	_enter("%lx", page->index);
+
+	rreq = netfs_alloc_read_request(ops, netfs_priv, file);
+	if (!rreq) {
+		if (netfs_priv)
+			ops->cleanup(netfs_priv, page->mapping);
+		unlock_page(page);
+		return -ENOMEM;
+	}
+	rreq->mapping	= page->mapping;
+	rreq->start	= page->index * PAGE_SIZE;
+	rreq->len	= thp_size(page);
+
+	netfs_get_read_request(rreq);
+
+	atomic_set(&rreq->nr_rd_ops, 1);
+	do {
+		if (!netfs_rreq_submit_slice(rreq, &debug_index))
+			break;
+
+	} while (rreq->submitted < rreq->len);
+
+	/* Keep nr_rd_ops incremented so that the ref always belongs to us, and
+	 * the service code isn't punted off to a random thread pool to
+	 * process.
+	 */
+	do {
+		wait_var_event(&rreq->nr_rd_ops, atomic_read(&rreq->nr_rd_ops) == 1);
+		netfs_rreq_assess(rreq);
+	} while (test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags));
+
+	ret = rreq->error;
+	if (ret == 0 && rreq->submitted < rreq->len)
+		ret = -EIO;
+	netfs_put_read_request(rreq);
+	return ret;
+}
+EXPORT_SYMBOL(netfs_readpage);
diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index f69703543788..7f74d668a459 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -10,6 +10,8 @@
 #ifndef _LINUX_NETFS_H
 #define _LINUX_NETFS_H
 
+#include <linux/workqueue.h>
+#include <linux/fs.h>
 #include <linux/pagemap.h>
 
 /*
@@ -51,4 +53,84 @@ static inline void wait_on_page_fscache(struct page *page)
 		wait_on_page_bit(compound_head(page), PG_fscache);
 }
 
+enum netfs_read_source {
+	NETFS_FILL_WITH_ZEROES,
+	NETFS_DOWNLOAD_FROM_SERVER,
+	NETFS_READ_FROM_CACHE,
+	NETFS_INVALID_READ,
+} __mode(byte);
+
+/*
+ * Descriptor for a single component subrequest.
+ */
+struct netfs_read_subrequest {
+	struct netfs_read_request *rreq;	/* Supervising read request */
+	struct list_head	rreq_link;	/* Link in rreq->subrequests */
+	loff_t			start;		/* Where to start the I/O */
+	size_t			len;		/* Size of the I/O */
+	size_t			transferred;	/* Amount of data transferred */
+	refcount_t		usage;
+	short			error;		/* 0 or error that occurred */
+	unsigned short		debug_index;	/* Index in list (for debugging output) */
+	enum netfs_read_source	source;		/* Where to read from */
+	unsigned long		flags;
+#define NETFS_SREQ_WRITE_TO_CACHE	0	/* Set if should write to cache */
+#define NETFS_SREQ_CLEAR_TAIL		1	/* Set if the rest of the read should be cleared */
+#define NETFS_SREQ_SHORT_READ		2	/* Set if there was a short read from the cache */
+#define NETFS_SREQ_SEEK_DATA_READ	3	/* Set if ->read() should SEEK_DATA first */
+#define NETFS_SREQ_NO_PROGRESS		4	/* Set if we didn't manage to read any data */
+};
+
+/*
+ * Descriptor for a read helper request.  This is used to make multiple I/O
+ * requests on a variety of sources and then stitch the result together.
+ */
+struct netfs_read_request {
+	struct work_struct	work;
+	struct inode		*inode;		/* The file being accessed */
+	struct address_space	*mapping;	/* The mapping being accessed */
+	struct list_head	subrequests;	/* Requests to fetch I/O from disk or net */
+	void			*netfs_priv;	/* Private data for the netfs */
+	atomic_t		nr_rd_ops;	/* Number of read ops in progress */
+	size_t			submitted;	/* Amount submitted for I/O so far */
+	size_t			len;		/* Length of the request */
+	short			error;		/* 0 or error that occurred */
+	loff_t			i_size;		/* Size of the file */
+	loff_t			start;		/* Start position */
+	pgoff_t			no_unlock_page;	/* Don't unlock this page after read */
+	refcount_t		usage;
+	unsigned long		flags;
+#define NETFS_RREQ_INCOMPLETE_IO	0	/* Some ioreqs terminated short or with error */
+#define NETFS_RREQ_WRITE_TO_CACHE	1	/* Need to write to the cache */
+#define NETFS_RREQ_NO_UNLOCK_PAGE	2	/* Don't unlock no_unlock_page on completion */
+#define NETFS_RREQ_DONT_UNLOCK_PAGES	3	/* Don't unlock the pages on completion */
+#define NETFS_RREQ_FAILED		4	/* The request failed */
+#define NETFS_RREQ_IN_PROGRESS		5	/* Unlocked when the request completes */
+	const struct netfs_read_request_ops *netfs_ops;
+};
+
+/*
+ * Operations the network filesystem can/must provide to the helpers.
+ */
+struct netfs_read_request_ops {
+	void (*init_rreq)(struct netfs_read_request *rreq, struct file *file);
+	void (*expand_readahead)(struct netfs_read_request *rreq);
+	bool (*clamp_length)(struct netfs_read_subrequest *subreq);
+	void (*issue_op)(struct netfs_read_subrequest *subreq);
+	bool (*is_still_valid)(struct netfs_read_request *rreq);
+	void (*done)(struct netfs_read_request *rreq);
+	void (*cleanup)(struct address_space *mapping, void *netfs_priv);
+};
+
+struct readahead_control;
+extern void netfs_readahead(struct readahead_control *,
+			    const struct netfs_read_request_ops *,
+			    void *);
+extern int netfs_readpage(struct file *,
+			  struct page *,
+			  const struct netfs_read_request_ops *,
+			  void *);
+
+extern void netfs_subreq_terminated(struct netfs_read_subrequest *, ssize_t);
+
 #endif /* _LINUX_NETFS_H */

[PATCH 09/33] netfs: Add tracepoints

[David Howells]

Add three tracepoints to track the activity of the read helpers:

 (1) netfs/netfs_read

     This logs entry to the read helpers and also expansion of the range in
     a readahead request.

 (2) netfs/netfs_rreq

     This logs the progress of netfs_read_request objects which track
     read requests.  A read request may be a compound of multiple
     subrequests.

 (3) netfs/netfs_sreq

     This logs the progress of netfs_read_subrequest objects, which track
     the contributions from various sources to a read request.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
cc: Matthew Wilcox <willy@infradead.org>
cc: linux-mm@kvack.org
cc: linux-cachefs@redhat.com
cc: linux-afs@lists.infradead.org
cc: linux-nfs@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: ceph-devel@vger.kernel.org
cc: v9fs-developer@lists.sourceforge.net
cc: linux-fsdevel@vger.kernel.org
---

 fs/netfs/read_helper.c       |   28 ++++++
 include/linux/netfs.h        |    2 
 include/trace/events/netfs.h |  199 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 229 insertions(+)
 create mode 100644 include/trace/events/netfs.h

diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c
index a35bd29928fa..53b04b105179 100644
--- a/fs/netfs/read_helper.c
+++ b/fs/netfs/read_helper.c
@@ -16,6 +16,8 @@
 #include <linux/task_io_accounting_ops.h>
 #include <linux/netfs.h>
 #include "internal.h"
+#define CREATE_TRACE_POINTS
+#include <trace/events/netfs.h>
 
 MODULE_DESCRIPTION("Network fs support");
 MODULE_AUTHOR("Red Hat, Inc.");
@@ -38,6 +40,7 @@ static struct netfs_read_request *netfs_alloc_read_request(
 	const struct netfs_read_request_ops *ops, void *netfs_priv,
 	struct file *file)
 {
+	static atomic_t debug_ids;
 	struct netfs_read_request *rreq;
 
 	rreq = kzalloc(sizeof(struct netfs_read_request), GFP_KERNEL);
@@ -46,6 +49,7 @@ static struct netfs_read_request *netfs_alloc_read_request(
 		rreq->netfs_priv = netfs_priv;
 		rreq->inode	= file_inode(file);
 		rreq->i_size	= i_size_read(rreq->inode);
+		rreq->debug_id	= atomic_inc_return(&debug_ids);
 		INIT_LIST_HEAD(&rreq->subrequests);
 		INIT_WORK(&rreq->work, netfs_rreq_work);
 		refcount_set(&rreq->usage, 1);
@@ -80,6 +84,7 @@ static void netfs_free_read_request(struct work_struct *work)
 	netfs_rreq_clear_subreqs(rreq);
 	if (rreq->netfs_priv)
 		rreq->netfs_ops->cleanup(rreq->mapping, rreq->netfs_priv);
+	trace_netfs_rreq(rreq, netfs_rreq_trace_free);
 	kfree(rreq);
 }
 
@@ -122,6 +127,7 @@ static void netfs_get_read_subrequest(struct netfs_read_subrequest *subreq)
 
 static void __netfs_put_subrequest(struct netfs_read_subrequest *subreq)
 {
+	trace_netfs_sreq(subreq, netfs_sreq_trace_free);
 	netfs_put_read_request(subreq->rreq);
 	kfree(subreq);
 }
@@ -176,6 +182,7 @@ static void netfs_read_from_server(struct netfs_read_request *rreq,
  */
 static void netfs_rreq_completed(struct netfs_read_request *rreq)
 {
+	trace_netfs_rreq(rreq, netfs_rreq_trace_done);
 	netfs_rreq_clear_subreqs(rreq);
 	netfs_put_read_request(rreq);
 }
@@ -214,6 +221,8 @@ static void netfs_rreq_unlock(struct netfs_read_request *rreq)
 	iopos = 0;
 	subreq_failed = (subreq->error < 0);
 
+	trace_netfs_rreq(rreq, netfs_rreq_trace_unlock);
+
 	rcu_read_lock();
 	xas_for_each(&xas, page, last_page) {
 		unsigned int pgpos = (page->index - start_page) * PAGE_SIZE;
@@ -274,6 +283,8 @@ static void netfs_rreq_short_read(struct netfs_read_request *rreq,
 	__clear_bit(NETFS_SREQ_SHORT_READ, &subreq->flags);
 	__set_bit(NETFS_SREQ_SEEK_DATA_READ, &subreq->flags);
 
+	trace_netfs_sreq(subreq, netfs_sreq_trace_resubmit_short);
+
 	netfs_get_read_subrequest(subreq);
 	atomic_inc(&rreq->nr_rd_ops);
 	netfs_read_from_server(rreq, subreq);
@@ -289,6 +300,8 @@ static bool netfs_rreq_perform_resubmissions(struct netfs_read_request *rreq)
 
 	WARN_ON(in_softirq());
 
+	trace_netfs_rreq(rreq, netfs_rreq_trace_resubmit);
+
 	/* We don't want terminating submissions trying to wake us up whilst
 	 * we're still going through the list.
 	 */
@@ -301,6 +314,7 @@ static bool netfs_rreq_perform_resubmissions(struct netfs_read_request *rreq)
 				break;
 			subreq->source = NETFS_DOWNLOAD_FROM_SERVER;
 			subreq->error = 0;
+			trace_netfs_sreq(subreq, netfs_sreq_trace_download_instead);
 			netfs_get_read_subrequest(subreq);
 			atomic_inc(&rreq->nr_rd_ops);
 			netfs_read_from_server(rreq, subreq);
@@ -325,6 +339,8 @@ static bool netfs_rreq_perform_resubmissions(struct netfs_read_request *rreq)
  */
 static void netfs_rreq_assess(struct netfs_read_request *rreq)
 {
+	trace_netfs_rreq(rreq, netfs_rreq_trace_assess);
+
 again:
 	if (!test_bit(NETFS_RREQ_FAILED, &rreq->flags) &&
 	    test_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags)) {
@@ -409,6 +425,8 @@ void netfs_subreq_terminated(struct netfs_read_subrequest *subreq,
 		set_bit(NETFS_RREQ_WRITE_TO_CACHE, &rreq->flags);
 
 out:
+	trace_netfs_sreq(subreq, netfs_sreq_trace_terminated);
+
 	/* If we decrement nr_rd_ops to 0, the ref belongs to us. */
 	u = atomic_dec_return(&rreq->nr_rd_ops);
 	if (u == 0)
@@ -497,6 +515,7 @@ netfs_rreq_prepare_read(struct netfs_read_request *rreq,
 
 out:
 	subreq->source = source;
+	trace_netfs_sreq(subreq, netfs_sreq_trace_prepare);
 	return source;
 }
 
@@ -536,6 +555,7 @@ static bool netfs_rreq_submit_slice(struct netfs_read_request *rreq,
 
 	rreq->submitted += subreq->len;
 
+	trace_netfs_sreq(subreq, netfs_sreq_trace_submit);
 	switch (source) {
 	case NETFS_FILL_WITH_ZEROES:
 		netfs_fill_with_zeroes(rreq, subreq);
@@ -578,6 +598,9 @@ static void netfs_rreq_expand(struct netfs_read_request *rreq,
 		readahead_expand(ractl, rreq->start, rreq->len);
 		rreq->start  = readahead_pos(ractl);
 		rreq->len = readahead_length(ractl);
+
+		trace_netfs_read(rreq, readahead_pos(ractl), readahead_length(ractl),
+				 netfs_read_trace_expanded);
 	}
 }
 
@@ -619,6 +642,9 @@ void netfs_readahead(struct readahead_control *ractl,
 	rreq->start	= readahead_pos(ractl);
 	rreq->len	= readahead_length(ractl);
 
+	trace_netfs_read(rreq, readahead_pos(ractl), readahead_length(ractl),
+			 netfs_read_trace_readahead);
+
 	netfs_rreq_expand(rreq, ractl);
 
 	atomic_set(&rreq->nr_rd_ops, 1);
@@ -690,6 +716,8 @@ int netfs_readpage(struct file *file,
 	rreq->start	= page->index * PAGE_SIZE;
 	rreq->len	= thp_size(page);
 
+	trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_readpage);
+
 	netfs_get_read_request(rreq);
 
 	atomic_set(&rreq->nr_rd_ops, 1);
diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index 7f74d668a459..24083dc0adfa 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -91,6 +91,8 @@ struct netfs_read_request {
 	struct address_space	*mapping;	/* The mapping being accessed */
 	struct list_head	subrequests;	/* Requests to fetch I/O from disk or net */
 	void			*netfs_priv;	/* Private data for the netfs */
+	unsigned int		debug_id;
+	unsigned int		cookie_debug_id;
 	atomic_t		nr_rd_ops;	/* Number of read ops in progress */
 	size_t			submitted;	/* Amount submitted for I/O so far */
 	size_t			len;		/* Length of the request */
diff --git a/include/trace/events/netfs.h b/include/trace/events/netfs.h
new file mode 100644
index 000000000000..12ad382764c5
--- /dev/null
+++ b/include/trace/events/netfs.h
@@ -0,0 +1,199 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Network filesystem support module tracepoints
+ *
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM netfs
+
+#if !defined(_TRACE_NETFS_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_NETFS_H
+
+#include <linux/tracepoint.h>
+
+/*
+ * Define enums for tracing information.
+ */
+#ifndef __NETFS_DECLARE_TRACE_ENUMS_ONCE_ONLY
+#define __NETFS_DECLARE_TRACE_ENUMS_ONCE_ONLY
+
+enum netfs_read_trace {
+	netfs_read_trace_expanded,
+	netfs_read_trace_readahead,
+	netfs_read_trace_readpage,
+};
+
+enum netfs_rreq_trace {
+	netfs_rreq_trace_assess,
+	netfs_rreq_trace_done,
+	netfs_rreq_trace_free,
+	netfs_rreq_trace_resubmit,
+	netfs_rreq_trace_unlock,
+	netfs_rreq_trace_unmark,
+	netfs_rreq_trace_write,
+};
+
+enum netfs_sreq_trace {
+	netfs_sreq_trace_download_instead,
+	netfs_sreq_trace_free,
+	netfs_sreq_trace_prepare,
+	netfs_sreq_trace_resubmit_short,
+	netfs_sreq_trace_submit,
+	netfs_sreq_trace_terminated,
+	netfs_sreq_trace_write,
+	netfs_sreq_trace_write_term,
+};
+
+#endif
+
+#define netfs_read_traces					\
+	EM(netfs_read_trace_expanded,		"EXPANDED ")	\
+	EM(netfs_read_trace_readahead,		"READAHEAD")	\
+	E_(netfs_read_trace_readpage,		"READPAGE ")
+
+#define netfs_rreq_traces					\
+	EM(netfs_rreq_trace_assess,		"ASSESS")	\
+	EM(netfs_rreq_trace_done,		"DONE  ")	\
+	EM(netfs_rreq_trace_free,		"FREE  ")	\
+	EM(netfs_rreq_trace_resubmit,		"RESUBM")	\
+	EM(netfs_rreq_trace_unlock,		"UNLOCK")	\
+	EM(netfs_rreq_trace_unmark,		"UNMARK")	\
+	E_(netfs_rreq_trace_write,		"WRITE ")
+
+#define netfs_sreq_sources					\
+	EM(NETFS_FILL_WITH_ZEROES,		"ZERO")		\
+	EM(NETFS_DOWNLOAD_FROM_SERVER,		"DOWN")		\
+	EM(NETFS_READ_FROM_CACHE,		"READ")		\
+	E_(NETFS_INVALID_READ,			"INVL")		\
+
+#define netfs_sreq_traces					\
+	EM(netfs_sreq_trace_download_instead,	"RDOWN")	\
+	EM(netfs_sreq_trace_free,		"FREE ")	\
+	EM(netfs_sreq_trace_prepare,		"PREP ")	\
+	EM(netfs_sreq_trace_resubmit_short,	"SHORT")	\
+	EM(netfs_sreq_trace_submit,		"SUBMT")	\
+	EM(netfs_sreq_trace_terminated,		"TERM ")	\
+	EM(netfs_sreq_trace_write,		"WRITE")	\
+	E_(netfs_sreq_trace_write_term,		"WTERM")
+
+
+/*
+ * Export enum symbols via userspace.
+ */
+#undef EM
+#undef E_
+#define EM(a, b) TRACE_DEFINE_ENUM(a);
+#define E_(a, b) TRACE_DEFINE_ENUM(a);
+
+netfs_read_traces;
+netfs_rreq_traces;
+netfs_sreq_sources;
+netfs_sreq_traces;
+
+/*
+ * Now redefine the EM() and E_() macros to map the enums to the strings that
+ * will be printed in the output.
+ */
+#undef EM
+#undef E_
+#define EM(a, b)	{ a, b },
+#define E_(a, b)	{ a, b }
+
+TRACE_EVENT(netfs_read,
+	    TP_PROTO(struct netfs_read_request *rreq,
+		     loff_t start, size_t len,
+		     enum netfs_read_trace what),
+
+	    TP_ARGS(rreq, start, len, what),
+
+	    TP_STRUCT__entry(
+		    __field(unsigned int,		rreq		)
+		    __field(unsigned int,		cookie		)
+		    __field(loff_t,			start		)
+		    __field(size_t,			len		)
+		    __field(enum netfs_read_trace,	what		)
+			     ),
+
+	    TP_fast_assign(
+		    __entry->rreq	= rreq->debug_id;
+		    __entry->cookie	= rreq->cookie_debug_id;
+		    __entry->start	= start;
+		    __entry->len	= len;
+		    __entry->what	= what;
+			   ),
+
+	    TP_printk("R=%08x %s c=%08x s=%llx %zx",
+		      __entry->rreq,
+		      __print_symbolic(__entry->what, netfs_read_traces),
+		      __entry->cookie,
+		      __entry->start, __entry->len)
+	    );
+
+TRACE_EVENT(netfs_rreq,
+	    TP_PROTO(struct netfs_read_request *rreq,
+		     enum netfs_rreq_trace what),
+
+	    TP_ARGS(rreq, what),
+
+	    TP_STRUCT__entry(
+		    __field(unsigned int,		rreq		)
+		    __field(unsigned short,		flags		)
+		    __field(enum netfs_rreq_trace,	what		)
+			     ),
+
+	    TP_fast_assign(
+		    __entry->rreq	= rreq->debug_id;
+		    __entry->flags	= rreq->flags;
+		    __entry->what	= what;
+			   ),
+
+	    TP_printk("R=%08x %s f=%02x",
+		      __entry->rreq,
+		      __print_symbolic(__entry->what, netfs_rreq_traces),
+		      __entry->flags)
+	    );
+
+TRACE_EVENT(netfs_sreq,
+	    TP_PROTO(struct netfs_read_subrequest *sreq,
+		     enum netfs_sreq_trace what),
+
+	    TP_ARGS(sreq, what),
+
+	    TP_STRUCT__entry(
+		    __field(unsigned int,		rreq		)
+		    __field(unsigned short,		index		)
+		    __field(short,			error		)
+		    __field(unsigned short,		flags		)
+		    __field(enum netfs_read_source,	source		)
+		    __field(enum netfs_sreq_trace,	what		)
+		    __field(size_t,			len		)
+		    __field(size_t,			transferred	)
+		    __field(loff_t,			start		)
+			     ),
+
+	    TP_fast_assign(
+		    __entry->rreq	= sreq->rreq->debug_id;
+		    __entry->index	= sreq->debug_index;
+		    __entry->error	= sreq->error;
+		    __entry->flags	= sreq->flags;
+		    __entry->source	= sreq->source;
+		    __entry->what	= what;
+		    __entry->len	= sreq->len;
+		    __entry->transferred = sreq->transferred;
+		    __entry->start	= sreq->start;
+			   ),
+
+	    TP_printk("R=%08x[%u] %s %s f=%02x s=%llx %zx/%zx e=%d",
+		      __entry->rreq, __entry->index,
+		      __print_symbolic(__entry->what, netfs_sreq_traces),
+		      __print_symbolic(__entry->source, netfs_sreq_sources),
+		      __entry->flags,
+		      __entry->start, __entry->transferred, __entry->len,
+		      __entry->error)
+	    );
+
+#endif /* _TRACE_NETFS_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>

[PATCH 10/33] netfs: Gather stats

[David Howells]

Gather statistics from the netfs interface that can be exported through a
seqfile.  This is intended to be called by a later patch when viewing
/proc/fs/fscache/stats.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
cc: Matthew Wilcox <willy@infradead.org>
cc: linux-mm@kvack.org
cc: linux-cachefs@redhat.com
cc: linux-afs@lists.infradead.org
cc: linux-nfs@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: ceph-devel@vger.kernel.org
cc: v9fs-developer@lists.sourceforge.net
cc: linux-fsdevel@vger.kernel.org
---

 fs/netfs/Kconfig       |   15 +++++++++++++
 fs/netfs/Makefile      |    3 +--
 fs/netfs/internal.h    |   34 ++++++++++++++++++++++++++++++
 fs/netfs/read_helper.c |   23 ++++++++++++++++++++
 fs/netfs/stats.c       |   54 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/netfs.h  |    1 +
 6 files changed, 128 insertions(+), 2 deletions(-)
 create mode 100644 fs/netfs/stats.c

diff --git a/fs/netfs/Kconfig b/fs/netfs/Kconfig
index 2ebf90e6ca95..578112713703 100644
--- a/fs/netfs/Kconfig
+++ b/fs/netfs/Kconfig
@@ -6,3 +6,18 @@ config NETFS_SUPPORT
 	  This option enables support for network filesystems, including
 	  helpers for high-level buffered I/O, abstracting out read
 	  segmentation, local caching and transparent huge page support.
+
+config NETFS_STATS
+	bool "Gather statistical information on local caching"
+	depends on NETFS_SUPPORT && PROC_FS
+	help
+	  This option causes statistical information to be gathered on local
+	  caching and exported through file:
+
+		/proc/fs/fscache/stats
+
+	  The gathering of statistics adds a certain amount of overhead to
+	  execution as there are a quite a few stats gathered, and on a
+	  multi-CPU system these may be on cachelines that keep bouncing
+	  between CPUs.  On the other hand, the stats are very useful for
+	  debugging purposes.  Saying 'Y' here is recommended.
diff --git a/fs/netfs/Makefile b/fs/netfs/Makefile
index 4b4eff2ba369..c15bfc966d96 100644
--- a/fs/netfs/Makefile
+++ b/fs/netfs/Makefile
@@ -1,6 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
 
-netfs-y := \
-	read_helper.o
+netfs-y := read_helper.o stats.o
 
 obj-$(CONFIG_NETFS_SUPPORT) := netfs.o
diff --git a/fs/netfs/internal.h b/fs/netfs/internal.h
index ee665c0e7dc8..98b6f4516da1 100644
--- a/fs/netfs/internal.h
+++ b/fs/netfs/internal.h
@@ -16,8 +16,42 @@
  */
 extern unsigned int netfs_debug;
 
+/*
+ * stats.c
+ */
+#ifdef CONFIG_NETFS_STATS
+extern atomic_t netfs_n_rh_readahead;
+extern atomic_t netfs_n_rh_readpage;
+extern atomic_t netfs_n_rh_rreq;
+extern atomic_t netfs_n_rh_sreq;
+extern atomic_t netfs_n_rh_download;
+extern atomic_t netfs_n_rh_download_done;
+extern atomic_t netfs_n_rh_download_failed;
+extern atomic_t netfs_n_rh_download_instead;
+extern atomic_t netfs_n_rh_read;
+extern atomic_t netfs_n_rh_read_done;
+extern atomic_t netfs_n_rh_read_failed;
+extern atomic_t netfs_n_rh_zero;
+extern atomic_t netfs_n_rh_short_read;
+extern atomic_t netfs_n_rh_write;
+extern atomic_t netfs_n_rh_write_done;
+extern atomic_t netfs_n_rh_write_failed;
+
+
+static inline void netfs_stat(atomic_t *stat)
+{
+	atomic_inc(stat);
+}
+
+static inline void netfs_stat_d(atomic_t *stat)
+{
+	atomic_dec(stat);
+}
+
+#else
 #define netfs_stat(x) do {} while(0)
 #define netfs_stat_d(x) do {} while(0)
+#endif
 
 /*****************************************************************************/
 /*
diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c
index 53b04b105179..4f6f708f8f18 100644
--- a/fs/netfs/read_helper.c
+++ b/fs/netfs/read_helper.c
@@ -55,6 +55,7 @@ static struct netfs_read_request *netfs_alloc_read_request(
 		refcount_set(&rreq->usage, 1);
 		__set_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags);
 		ops->init_rreq(rreq, file);
+		netfs_stat(&netfs_n_rh_rreq);
 	}
 
 	return rreq;
@@ -86,6 +87,7 @@ static void netfs_free_read_request(struct work_struct *work)
 		rreq->netfs_ops->cleanup(rreq->mapping, rreq->netfs_priv);
 	trace_netfs_rreq(rreq, netfs_rreq_trace_free);
 	kfree(rreq);
+	netfs_stat_d(&netfs_n_rh_rreq);
 }
 
 static void netfs_put_read_request(struct netfs_read_request *rreq)
@@ -115,6 +117,7 @@ static struct netfs_read_subrequest *netfs_alloc_subrequest(
 		refcount_set(&subreq->usage, 2);
 		subreq->rreq = rreq;
 		netfs_get_read_request(rreq);
+		netfs_stat(&netfs_n_rh_sreq);
 	}
 
 	return subreq;
@@ -130,6 +133,7 @@ static void __netfs_put_subrequest(struct netfs_read_subrequest *subreq)
 	trace_netfs_sreq(subreq, netfs_sreq_trace_free);
 	netfs_put_read_request(subreq->rreq);
 	kfree(subreq);
+	netfs_stat_d(&netfs_n_rh_sreq);
 }
 
 /*
@@ -151,6 +155,7 @@ static void netfs_clear_unread(struct netfs_read_subrequest *subreq)
 static void netfs_fill_with_zeroes(struct netfs_read_request *rreq,
 				   struct netfs_read_subrequest *subreq)
 {
+	netfs_stat(&netfs_n_rh_zero);
 	__set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
 	netfs_subreq_terminated(subreq, 0);
 }
@@ -174,6 +179,7 @@ static void netfs_fill_with_zeroes(struct netfs_read_request *rreq,
 static void netfs_read_from_server(struct netfs_read_request *rreq,
 				   struct netfs_read_subrequest *subreq)
 {
+	netfs_stat(&netfs_n_rh_download);
 	rreq->netfs_ops->issue_op(subreq);
 }
 
@@ -283,6 +289,7 @@ static void netfs_rreq_short_read(struct netfs_read_request *rreq,
 	__clear_bit(NETFS_SREQ_SHORT_READ, &subreq->flags);
 	__set_bit(NETFS_SREQ_SEEK_DATA_READ, &subreq->flags);
 
+	netfs_stat(&netfs_n_rh_short_read);
 	trace_netfs_sreq(subreq, netfs_sreq_trace_resubmit_short);
 
 	netfs_get_read_subrequest(subreq);
@@ -314,6 +321,7 @@ static bool netfs_rreq_perform_resubmissions(struct netfs_read_request *rreq)
 				break;
 			subreq->source = NETFS_DOWNLOAD_FROM_SERVER;
 			subreq->error = 0;
+			netfs_stat(&netfs_n_rh_download_instead);
 			trace_netfs_sreq(subreq, netfs_sreq_trace_download_instead);
 			netfs_get_read_subrequest(subreq);
 			atomic_inc(&rreq->nr_rd_ops);
@@ -406,6 +414,17 @@ void netfs_subreq_terminated(struct netfs_read_subrequest *subreq,
 	       subreq->debug_index, subreq->start, subreq->flags,
 	       transferred_or_error);
 
+	switch (subreq->source) {
+	case NETFS_READ_FROM_CACHE:
+		netfs_stat(&netfs_n_rh_read_done);
+		break;
+	case NETFS_DOWNLOAD_FROM_SERVER:
+		netfs_stat(&netfs_n_rh_download_done);
+		break;
+	default:
+		break;
+	}
+
 	if (IS_ERR_VALUE(transferred_or_error)) {
 		subreq->error = transferred_or_error;
 		goto failed;
@@ -459,8 +478,10 @@ void netfs_subreq_terminated(struct netfs_read_subrequest *subreq,
 
 failed:
 	if (subreq->source == NETFS_READ_FROM_CACHE) {
+		netfs_stat(&netfs_n_rh_read_failed);
 		set_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags);
 	} else {
+		netfs_stat(&netfs_n_rh_download_failed);
 		set_bit(NETFS_RREQ_FAILED, &rreq->flags);
 		rreq->error = subreq->error;
 	}
@@ -642,6 +663,7 @@ void netfs_readahead(struct readahead_control *ractl,
 	rreq->start	= readahead_pos(ractl);
 	rreq->len	= readahead_length(ractl);
 
+	netfs_stat(&netfs_n_rh_readahead);
 	trace_netfs_read(rreq, readahead_pos(ractl), readahead_length(ractl),
 			 netfs_read_trace_readahead);
 
@@ -716,6 +738,7 @@ int netfs_readpage(struct file *file,
 	rreq->start	= page->index * PAGE_SIZE;
 	rreq->len	= thp_size(page);
 
+	netfs_stat(&netfs_n_rh_readpage);
 	trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_readpage);
 
 	netfs_get_read_request(rreq);
diff --git a/fs/netfs/stats.c b/fs/netfs/stats.c
new file mode 100644
index 000000000000..df6ff5718f25
--- /dev/null
+++ b/fs/netfs/stats.c
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Netfs support statistics
+ *
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/export.h>
+#include <linux/seq_file.h>
+#include <linux/netfs.h>
+#include "internal.h"
+
+atomic_t netfs_n_rh_readahead;
+atomic_t netfs_n_rh_readpage;
+atomic_t netfs_n_rh_rreq;
+atomic_t netfs_n_rh_sreq;
+atomic_t netfs_n_rh_download;
+atomic_t netfs_n_rh_download_done;
+atomic_t netfs_n_rh_download_failed;
+atomic_t netfs_n_rh_download_instead;
+atomic_t netfs_n_rh_read;
+atomic_t netfs_n_rh_read_done;
+atomic_t netfs_n_rh_read_failed;
+atomic_t netfs_n_rh_zero;
+atomic_t netfs_n_rh_short_read;
+atomic_t netfs_n_rh_write;
+atomic_t netfs_n_rh_write_done;
+atomic_t netfs_n_rh_write_failed;
+
+void netfs_stats_show(struct seq_file *m)
+{
+	seq_printf(m, "RdHelp : RA=%u RP=%u rr=%u sr=%u\n",
+		   atomic_read(&netfs_n_rh_readahead),
+		   atomic_read(&netfs_n_rh_readpage),
+		   atomic_read(&netfs_n_rh_rreq),
+		   atomic_read(&netfs_n_rh_sreq));
+	seq_printf(m, "RdHelp : ZR=%u sh=%u\n",
+		   atomic_read(&netfs_n_rh_zero),
+		   atomic_read(&netfs_n_rh_short_read));
+	seq_printf(m, "RdHelp : DL=%u ds=%u df=%u di=%u\n",
+		   atomic_read(&netfs_n_rh_download),
+		   atomic_read(&netfs_n_rh_download_done),
+		   atomic_read(&netfs_n_rh_download_failed),
+		   atomic_read(&netfs_n_rh_download_instead));
+	seq_printf(m, "RdHelp : RD=%u rs=%u rf=%u\n",
+		   atomic_read(&netfs_n_rh_read),
+		   atomic_read(&netfs_n_rh_read_done),
+		   atomic_read(&netfs_n_rh_read_failed));
+	seq_printf(m, "RdHelp : WR=%u ws=%u wf=%u\n",
+		   atomic_read(&netfs_n_rh_write),
+		   atomic_read(&netfs_n_rh_write_done),
+		   atomic_read(&netfs_n_rh_write_failed));
+}
+EXPORT_SYMBOL(netfs_stats_show);
diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index 24083dc0adfa..b8237b6f17cb 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -134,5 +134,6 @@ extern int netfs_readpage(struct file *,
 			  void *);
 
 extern void netfs_subreq_terminated(struct netfs_read_subrequest *, ssize_t);
+extern void netfs_stats_show(struct seq_file *);
 
 #endif /* _LINUX_NETFS_H */

[PATCH 11/33] netfs: Add write_begin helper

[David Howells]

Add a helper to do the pre-reading work for the netfs write_begin address
space op.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
cc: Matthew Wilcox <willy@infradead.org>
cc: linux-mm@kvack.org
cc: linux-cachefs@redhat.com
cc: linux-afs@lists.infradead.org
cc: linux-nfs@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: ceph-devel@vger.kernel.org
cc: v9fs-developer@lists.sourceforge.net
cc: linux-fsdevel@vger.kernel.org
---

 fs/netfs/internal.h          |    2 +
 fs/netfs/read_helper.c       |  165 ++++++++++++++++++++++++++++++++++++++++++
 fs/netfs/stats.c             |   10 ++-
 include/linux/netfs.h        |    8 ++
 include/trace/events/netfs.h |    4 +
 5 files changed, 185 insertions(+), 4 deletions(-)

diff --git a/fs/netfs/internal.h b/fs/netfs/internal.h
index 98b6f4516da1..b7f2c4459f33 100644
--- a/fs/netfs/internal.h
+++ b/fs/netfs/internal.h
@@ -34,8 +34,10 @@ extern atomic_t netfs_n_rh_read_failed;
 extern atomic_t netfs_n_rh_zero;
 extern atomic_t netfs_n_rh_short_read;
 extern atomic_t netfs_n_rh_write;
+extern atomic_t netfs_n_rh_write_begin;
 extern atomic_t netfs_n_rh_write_done;
 extern atomic_t netfs_n_rh_write_failed;
+extern atomic_t netfs_n_rh_write_zskip;
 
 
 static inline void netfs_stat(atomic_t *stat)
diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c
index 4f6f708f8f18..d179a37b92fd 100644
--- a/fs/netfs/read_helper.c
+++ b/fs/netfs/read_helper.c
@@ -766,3 +766,168 @@ int netfs_readpage(struct file *file,
 	return ret;
 }
 EXPORT_SYMBOL(netfs_readpage);
+
+static void netfs_clear_thp(struct page *page)
+{
+	unsigned int i;
+
+	for (i = 0; i < thp_nr_pages(page); i++)
+		clear_highpage(page + i);
+}
+
+/**
+ * netfs_write_begin - Helper to prepare for writing
+ * @file: The file to read from
+ * @mapping: The mapping to read from
+ * @pos: File position at which the write will begin
+ * @len: The length of the write in this page
+ * @flags: AOP_* flags
+ * @_page: Where to put the resultant page
+ * @_fsdata: Place for the netfs to store a cookie
+ * @ops: The network filesystem's operations for the helper to use
+ * @netfs_priv: Private netfs data to be retained in the request
+ *
+ * Pre-read data for a write-begin request by drawing data from the cache if
+ * possible, or the netfs if not.  Space beyond the EOF is zero-filled.
+ * Multiple I/O requests from different sources will get munged together.  If
+ * necessary, the readahead window can be expanded in either direction to a
+ * more convenient alighment for RPC efficiency or to make storage in the cache
+ * feasible.
+ *
+ * The calling netfs must provide a table of operations, only one of which,
+ * issue_op, is mandatory.
+ *
+ * The check_write_begin() operation can be provided to check for and flush
+ * conflicting writes once the page is grabbed and locked.  It is passed a
+ * pointer to the fsdata cookie that gets returned to the VM to be passed to
+ * write_end.  It is permitted to sleep.  It should return 0 if the request
+ * should go ahead; unlock the page and return -EAGAIN to cause the page to be
+ * regot; or return an error.
+ *
+ * This is usable whether or not caching is enabled.
+ */
+int netfs_write_begin(struct file *file, struct address_space *mapping,
+		      loff_t pos, unsigned int len, unsigned int flags,
+		      struct page **_page, void **_fsdata,
+		      const struct netfs_read_request_ops *ops,
+		      void *netfs_priv)
+{
+	struct netfs_read_request *rreq;
+	struct page *page, *xpage;
+	struct inode *inode = file_inode(file);
+	unsigned int debug_index = 0;
+	pgoff_t index = pos >> PAGE_SHIFT;
+	int pos_in_page = pos & ~PAGE_MASK;
+	loff_t size;
+	int ret;
+
+	struct readahead_control ractl = {
+		.file		= file,
+		.mapping	= mapping,
+		._index		= index,
+		._nr_pages	= 0,
+	};
+
+retry:
+	page = grab_cache_page_write_begin(mapping, index, 0);
+	if (!page)
+		return -ENOMEM;
+
+	if (ops->check_write_begin) {
+		/* Allow the netfs (eg. ceph) to flush conflicts. */
+		ret = ops->check_write_begin(file, pos, len, page, _fsdata);
+		if (ret < 0) {
+			if (ret == -EAGAIN)
+				goto retry;
+			goto error;
+		}
+	}
+
+	if (PageUptodate(page))
+		goto have_page;
+
+	/* If the page is beyond the EOF, we want to clear it - unless it's
+	 * within the cache granule containing the EOF, in which case we need
+	 * to preload the granule.
+	 */
+	size = i_size_read(inode);
+	if (!ops->is_cache_enabled(inode) &&
+	    ((pos_in_page == 0 && len == thp_size(page)) ||
+	     (pos >= size) ||
+	     (pos_in_page == 0 && (pos + len) >= size))) {
+		netfs_clear_thp(page);
+		SetPageUptodate(page);
+		netfs_stat(&netfs_n_rh_write_zskip);
+		goto have_page_no_wait;
+	}
+
+	ret = -ENOMEM;
+	rreq = netfs_alloc_read_request(ops, netfs_priv, file);
+	if (!rreq)
+		goto error;
+	rreq->mapping		= page->mapping;
+	rreq->start		= page->index * PAGE_SIZE;
+	rreq->len		= thp_size(page);
+	rreq->no_unlock_page	= page->index;
+	__set_bit(NETFS_RREQ_NO_UNLOCK_PAGE, &rreq->flags);
+	netfs_priv = NULL;
+
+	netfs_stat(&netfs_n_rh_write_begin);
+	trace_netfs_read(rreq, pos, len, netfs_read_trace_write_begin);
+
+	/* Expand the request to meet caching requirements and download
+	 * preferences.
+	 */
+	ractl._nr_pages = thp_nr_pages(page);
+	netfs_rreq_expand(rreq, &ractl);
+	netfs_get_read_request(rreq);
+
+	/* We hold the page locks, so we can drop the references */
+	while ((xpage = readahead_page(&ractl)))
+		if (xpage != page)
+			put_page(xpage);
+
+	atomic_set(&rreq->nr_rd_ops, 1);
+	do {
+		if (!netfs_rreq_submit_slice(rreq, &debug_index))
+			break;
+
+	} while (rreq->submitted < rreq->len);
+
+	/* Keep nr_rd_ops incremented so that the ref always belongs to us, and
+	 * the service code isn't punted off to a random thread pool to
+	 * process.
+	 */
+	for (;;) {
+		wait_var_event(&rreq->nr_rd_ops, atomic_read(&rreq->nr_rd_ops) == 1);
+		netfs_rreq_assess(rreq);
+		if (!test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags))
+			break;
+		cond_resched();
+	}
+
+	ret = rreq->error;
+	if (ret == 0 && rreq->submitted < rreq->len)
+		ret = -EIO;
+	netfs_put_read_request(rreq);
+	if (ret < 0)
+		goto error;
+
+have_page:
+	wait_on_page_fscache(page);
+have_page_no_wait:
+	if (netfs_priv)
+		ops->cleanup(netfs_priv, mapping);
+	*_page = page;
+	_leave(" = 0");
+	return 0;
+
+error:
+	unlock_page(page);
+	put_page(page);
+	if (netfs_priv)
+		ops->cleanup(netfs_priv, mapping);
+	_leave(" = %d", ret);
+	return ret;
+}
+EXPORT_SYMBOL(netfs_write_begin);
diff --git a/fs/netfs/stats.c b/fs/netfs/stats.c
index df6ff5718f25..dd7ad66ed07e 100644
--- a/fs/netfs/stats.c
+++ b/fs/netfs/stats.c
@@ -24,19 +24,23 @@ atomic_t netfs_n_rh_read_failed;
 atomic_t netfs_n_rh_zero;
 atomic_t netfs_n_rh_short_read;
 atomic_t netfs_n_rh_write;
+atomic_t netfs_n_rh_write_begin;
 atomic_t netfs_n_rh_write_done;
 atomic_t netfs_n_rh_write_failed;
+atomic_t netfs_n_rh_write_zskip;
 
 void netfs_stats_show(struct seq_file *m)
 {
-	seq_printf(m, "RdHelp : RA=%u RP=%u rr=%u sr=%u\n",
+	seq_printf(m, "RdHelp : RA=%u RP=%u WB=%u rr=%u sr=%u\n",
 		   atomic_read(&netfs_n_rh_readahead),
 		   atomic_read(&netfs_n_rh_readpage),
+		   atomic_read(&netfs_n_rh_write_begin),
 		   atomic_read(&netfs_n_rh_rreq),
 		   atomic_read(&netfs_n_rh_sreq));
-	seq_printf(m, "RdHelp : ZR=%u sh=%u\n",
+	seq_printf(m, "RdHelp : ZR=%u sh=%u sk=%u\n",
 		   atomic_read(&netfs_n_rh_zero),
-		   atomic_read(&netfs_n_rh_short_read));
+		   atomic_read(&netfs_n_rh_short_read),
+		   atomic_read(&netfs_n_rh_write_zskip));
 	seq_printf(m, "RdHelp : DL=%u ds=%u df=%u di=%u\n",
 		   atomic_read(&netfs_n_rh_download),
 		   atomic_read(&netfs_n_rh_download_done),
diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index b8237b6f17cb..ec9d1240ba49 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -115,11 +115,14 @@ struct netfs_read_request {
  * Operations the network filesystem can/must provide to the helpers.
  */
 struct netfs_read_request_ops {
+	bool (*is_cache_enabled)(struct inode *inode);
 	void (*init_rreq)(struct netfs_read_request *rreq, struct file *file);
 	void (*expand_readahead)(struct netfs_read_request *rreq);
 	bool (*clamp_length)(struct netfs_read_subrequest *subreq);
 	void (*issue_op)(struct netfs_read_subrequest *subreq);
 	bool (*is_still_valid)(struct netfs_read_request *rreq);
+	int (*check_write_begin)(struct file *file, loff_t pos, unsigned len,
+				 struct page *page, void **_fsdata);
 	void (*done)(struct netfs_read_request *rreq);
 	void (*cleanup)(struct address_space *mapping, void *netfs_priv);
 };
@@ -132,6 +135,11 @@ extern int netfs_readpage(struct file *,
 			  struct page *,
 			  const struct netfs_read_request_ops *,
 			  void *);
+extern int netfs_write_begin(struct file *, struct address_space *,
+			     loff_t, unsigned int, unsigned int, struct page **,
+			     void **,
+			     const struct netfs_read_request_ops *,
+			     void *);
 
 extern void netfs_subreq_terminated(struct netfs_read_subrequest *, ssize_t);
 extern void netfs_stats_show(struct seq_file *);
diff --git a/include/trace/events/netfs.h b/include/trace/events/netfs.h
index 12ad382764c5..a2bf6cd84bd4 100644
--- a/include/trace/events/netfs.h
+++ b/include/trace/events/netfs.h
@@ -22,6 +22,7 @@ enum netfs_read_trace {
 	netfs_read_trace_expanded,
 	netfs_read_trace_readahead,
 	netfs_read_trace_readpage,
+	netfs_read_trace_write_begin,
 };
 
 enum netfs_rreq_trace {
@@ -50,7 +51,8 @@ enum netfs_sreq_trace {
 #define netfs_read_traces					\
 	EM(netfs_read_trace_expanded,		"EXPANDED ")	\
 	EM(netfs_read_trace_readahead,		"READAHEAD")	\
-	E_(netfs_read_trace_readpage,		"READPAGE ")
+	EM(netfs_read_trace_readpage,		"READPAGE ")	\
+	E_(netfs_read_trace_write_begin,	"WRITEBEGN")
 
 #define netfs_rreq_traces					\
 	EM(netfs_rreq_trace_assess,		"ASSESS")	\

[PATCH 12/33] netfs: Define an interface to talk to a cache

[David Howells]

Add an interface to the netfs helper library for reading data from the
cache instead of downloading it from the server and support for writing
data just downloaded or cleared to the cache.

The API passes an iov_iter to the cache read/write routines to indicate the
data/buffer to be used.  This is done using the ITER_XARRAY type to provide
direct access to the netfs inode's pagecache.

When the netfs's ->begin_cache_operation() method is called, this must fill
in the cache_resources in the netfs_read_request struct, including the
netfs_cache_ops used by the helper lib to talk to the cache.  The helper
lib does not directly access the cache.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
cc: Matthew Wilcox <willy@infradead.org>
cc: linux-mm@kvack.org
cc: linux-cachefs@redhat.com
cc: linux-afs@lists.infradead.org
cc: linux-nfs@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: ceph-devel@vger.kernel.org
cc: v9fs-developer@lists.sourceforge.net
cc: linux-fsdevel@vger.kernel.org
---

 fs/netfs/read_helper.c        |  230 +++++++++++++++++++++++++++++++++++++++++
 fs/netfs/stats.c              |    3 -
 include/linux/fscache-cache.h |    4 +
 include/linux/fscache.h       |   17 +++
 include/linux/netfs.h         |   48 +++++++++
 5 files changed, 300 insertions(+), 2 deletions(-)

diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c
index d179a37b92fd..156941e0de61 100644
--- a/fs/netfs/read_helper.c
+++ b/fs/netfs/read_helper.c
@@ -86,6 +86,8 @@ static void netfs_free_read_request(struct work_struct *work)
 	if (rreq->netfs_priv)
 		rreq->netfs_ops->cleanup(rreq->mapping, rreq->netfs_priv);
 	trace_netfs_rreq(rreq, netfs_rreq_trace_free);
+	if (rreq->cache_resources.ops)
+		rreq->cache_resources.ops->end_operation(&rreq->cache_resources);
 	kfree(rreq);
 	netfs_stat_d(&netfs_n_rh_rreq);
 }
@@ -149,6 +151,32 @@ static void netfs_clear_unread(struct netfs_read_subrequest *subreq)
 	iov_iter_zero(iov_iter_count(&iter), &iter);
 }
 
+static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error)
+{
+	struct netfs_read_subrequest *subreq = priv;
+
+	netfs_subreq_terminated(subreq, transferred_or_error);
+}
+
+/*
+ * Issue a read against the cache.
+ * - Eats the caller's ref on subreq.
+ */
+static void netfs_read_from_cache(struct netfs_read_request *rreq,
+				  struct netfs_read_subrequest *subreq,
+				  bool seek_data)
+{
+	struct netfs_cache_resources *cres = &rreq->cache_resources;
+	struct iov_iter iter;
+
+	iov_iter_xarray(&iter, READ, &rreq->mapping->i_pages,
+			subreq->start + subreq->transferred,
+			subreq->len   - subreq->transferred);
+
+	cres->ops->read(cres, subreq->start, &iter, seek_data,
+			netfs_cache_read_terminated, subreq);
+}
+
 /*
  * Fill a subrequest region with zeroes.
  */
@@ -193,6 +221,141 @@ static void netfs_rreq_completed(struct netfs_read_request *rreq)
 	netfs_put_read_request(rreq);
 }
 
+/*
+ * Deal with the completion of writing the data to the cache.  We have to clear
+ * the PG_fscache bits on the pages involved and release the caller's ref.
+ *
+ * May be called in softirq mode and we inherit a ref from the caller.
+ */
+static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq)
+{
+	struct netfs_read_subrequest *subreq;
+	struct page *page;
+	pgoff_t unlocked = 0;
+	bool have_unlocked = false;
+
+	rcu_read_lock();
+
+	list_for_each_entry(subreq, &rreq->subrequests, rreq_link) {
+		XA_STATE(xas, &rreq->mapping->i_pages, subreq->start / PAGE_SIZE);
+
+		xas_for_each(&xas, page, (subreq->start + subreq->len - 1) / PAGE_SIZE) {
+			/* We might have multiple writes from the same huge
+			 * page, but we mustn't unlock a page more than once.
+			 */
+			if (have_unlocked && page->index <= unlocked)
+				continue;
+			unlocked = page->index;
+			unlock_page_fscache(page);
+			have_unlocked = true;
+		}
+	}
+
+	rcu_read_unlock();
+	netfs_rreq_completed(rreq);
+}
+
+static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error)
+{
+	struct netfs_read_subrequest *subreq = priv;
+	struct netfs_read_request *rreq = subreq->rreq;
+
+	if (IS_ERR_VALUE(transferred_or_error)) {
+		subreq->error = transferred_or_error;
+		netfs_stat(&netfs_n_rh_write_failed);
+	} else {
+		subreq->error = 0;
+		netfs_stat(&netfs_n_rh_write_done);
+	}
+
+	trace_netfs_sreq(subreq, netfs_sreq_trace_write_term);
+
+	/* If we decrement nr_wr_ops to 0, the ref belongs to us. */
+	if (atomic_dec_and_test(&rreq->nr_wr_ops))
+		netfs_rreq_unmark_after_write(rreq);
+
+	netfs_put_subrequest(subreq);
+}
+
+/*
+ * Perform any outstanding writes to the cache.  We inherit a ref from the
+ * caller.
+ */
+static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq)
+{
+	struct netfs_cache_resources *cres = &rreq->cache_resources;
+	struct netfs_read_subrequest *subreq, *next, *p;
+	struct iov_iter iter;
+	loff_t pos;
+
+	trace_netfs_rreq(rreq, netfs_rreq_trace_write);
+
+	/* We don't want terminating writes trying to wake us up whilst we're
+	 * still going through the list.
+	 */
+	atomic_inc(&rreq->nr_wr_ops);
+
+	list_for_each_entry_safe(subreq, p, &rreq->subrequests, rreq_link) {
+		if (!test_bit(NETFS_SREQ_WRITE_TO_CACHE, &subreq->flags)) {
+			list_del_init(&subreq->rreq_link);
+			netfs_put_subrequest(subreq);
+		}
+	}
+
+	list_for_each_entry(subreq, &rreq->subrequests, rreq_link) {
+		/* Amalgamate adjacent writes */
+		pos = round_down(subreq->start, PAGE_SIZE);
+		if (pos != subreq->start) {
+			subreq->len += subreq->start - pos;
+			subreq->start = pos;
+		}
+		subreq->len = round_up(subreq->len, PAGE_SIZE);
+
+		while (!list_is_last(&subreq->rreq_link, &rreq->subrequests)) {
+			next = list_next_entry(subreq, rreq_link);
+			if (next->start > subreq->start + subreq->len)
+				break;
+			subreq->len += next->len;
+			subreq->len = round_up(subreq->len, PAGE_SIZE);
+			list_del_init(&next->rreq_link);
+			netfs_put_subrequest(next);
+		}
+
+		iov_iter_xarray(&iter, WRITE, &rreq->mapping->i_pages,
+				subreq->start, subreq->len);
+
+		atomic_inc(&rreq->nr_wr_ops);
+		netfs_stat(&netfs_n_rh_write);
+		netfs_get_read_subrequest(subreq);
+		trace_netfs_sreq(subreq, netfs_sreq_trace_write);
+		cres->ops->write(cres, subreq->start, &iter,
+				 netfs_rreq_copy_terminated, subreq);
+	}
+
+	/* If we decrement nr_wr_ops to 0, the usage ref belongs to us. */
+	if (atomic_dec_and_test(&rreq->nr_wr_ops))
+		netfs_rreq_unmark_after_write(rreq);
+}
+
+static void netfs_rreq_write_to_cache_work(struct work_struct *work)
+{
+	struct netfs_read_request *rreq =
+		container_of(work, struct netfs_read_request, work);
+
+	netfs_rreq_do_write_to_cache(rreq);
+}
+
+static void netfs_rreq_write_to_cache(struct netfs_read_request *rreq)
+{
+	if (in_softirq()) {
+		rreq->work.func = netfs_rreq_write_to_cache_work;
+		if (!queue_work(system_unbound_wq, &rreq->work))
+			BUG();
+	} else {
+		netfs_rreq_do_write_to_cache(rreq);
+	}
+}
+
 /*
  * Unlock the pages in a read operation.  We need to set PG_fscache on any
  * pages we're going to write back before we unlock them.
@@ -294,7 +457,10 @@ static void netfs_rreq_short_read(struct netfs_read_request *rreq,
 
 	netfs_get_read_subrequest(subreq);
 	atomic_inc(&rreq->nr_rd_ops);
-	netfs_read_from_server(rreq, subreq);
+	if (subreq->source == NETFS_READ_FROM_CACHE)
+		netfs_read_from_cache(rreq, subreq, true);
+	else
+		netfs_read_from_server(rreq, subreq);
 }
 
 /*
@@ -339,6 +505,25 @@ static bool netfs_rreq_perform_resubmissions(struct netfs_read_request *rreq)
 	return false;
 }
 
+/*
+ * Check to see if the data read is still valid.
+ */
+static void netfs_rreq_is_still_valid(struct netfs_read_request *rreq)
+{
+	struct netfs_read_subrequest *subreq;
+
+	if (!rreq->netfs_ops->is_still_valid ||
+	    rreq->netfs_ops->is_still_valid(rreq))
+		return;
+
+	list_for_each_entry(subreq, &rreq->subrequests, rreq_link) {
+		if (subreq->source == NETFS_READ_FROM_CACHE) {
+			subreq->error = -ESTALE;
+			__set_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags);
+		}
+	}
+}
+
 /*
  * Assess the state of a read request and decide what to do next.
  *
@@ -350,6 +535,8 @@ static void netfs_rreq_assess(struct netfs_read_request *rreq)
 	trace_netfs_rreq(rreq, netfs_rreq_trace_assess);
 
 again:
+	netfs_rreq_is_still_valid(rreq);
+
 	if (!test_bit(NETFS_RREQ_FAILED, &rreq->flags) &&
 	    test_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags)) {
 		if (netfs_rreq_perform_resubmissions(rreq))
@@ -362,6 +549,9 @@ static void netfs_rreq_assess(struct netfs_read_request *rreq)
 	clear_bit_unlock(NETFS_RREQ_IN_PROGRESS, &rreq->flags);
 	wake_up_bit(&rreq->flags, NETFS_RREQ_IN_PROGRESS);
 
+	if (test_bit(NETFS_RREQ_WRITE_TO_CACHE, &rreq->flags))
+		return netfs_rreq_write_to_cache(rreq);
+
 	netfs_rreq_completed(rreq);
 }
 
@@ -493,7 +683,10 @@ static enum netfs_read_source netfs_cache_prepare_read(struct netfs_read_subrequ
 						       loff_t i_size)
 {
 	struct netfs_read_request *rreq = subreq->rreq;
+	struct netfs_cache_resources *cres = &rreq->cache_resources;
 
+	if (cres->ops)
+		return cres->ops->prepare_read(subreq, i_size);
 	if (subreq->start >= rreq->i_size)
 		return NETFS_FILL_WITH_ZEROES;
 	return NETFS_DOWNLOAD_FROM_SERVER;
@@ -584,6 +777,9 @@ static bool netfs_rreq_submit_slice(struct netfs_read_request *rreq,
 	case NETFS_DOWNLOAD_FROM_SERVER:
 		netfs_read_from_server(rreq, subreq);
 		break;
+	case NETFS_READ_FROM_CACHE:
+		netfs_read_from_cache(rreq, subreq, false);
+		break;
 	default:
 		BUG();
 	}
@@ -596,9 +792,23 @@ static bool netfs_rreq_submit_slice(struct netfs_read_request *rreq,
 	return false;
 }
 
+static void netfs_cache_expand_readahead(struct netfs_read_request *rreq,
+					 loff_t *_start, size_t *_len, loff_t i_size)
+{
+	struct netfs_cache_resources *cres = &rreq->cache_resources;
+
+	if (cres->ops && cres->ops->expand_readahead)
+		cres->ops->expand_readahead(cres, _start, _len, i_size);
+}
+
 static void netfs_rreq_expand(struct netfs_read_request *rreq,
 			      struct readahead_control *ractl)
 {
+	/* Give the cache a chance to change the request parameters.  The
+	 * resultant request must contain the original region.
+	 */
+	netfs_cache_expand_readahead(rreq, &rreq->start, &rreq->len, rreq->i_size);
+
 	/* Give the netfs a chance to change the request parameters.  The
 	 * resultant request must contain the original region.
 	 */
@@ -650,6 +860,7 @@ void netfs_readahead(struct readahead_control *ractl,
 	struct netfs_read_request *rreq;
 	struct page *page;
 	unsigned int debug_index = 0;
+	int ret;
 
 	_enter("%lx,%x", readahead_index(ractl), readahead_count(ractl));
 
@@ -667,6 +878,11 @@ void netfs_readahead(struct readahead_control *ractl,
 	trace_netfs_read(rreq, readahead_pos(ractl), readahead_length(ractl),
 			 netfs_read_trace_readahead);
 
+	if (ops->begin_cache_operation) {
+		ret = ops->begin_cache_operation(rreq);
+		if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
+			goto cleanup_free;
+	}
 	netfs_rreq_expand(rreq, ractl);
 
 	atomic_set(&rreq->nr_rd_ops, 1);
@@ -692,6 +908,9 @@ void netfs_readahead(struct readahead_control *ractl,
 		netfs_rreq_assess(rreq);
 	return;
 
+cleanup_free:
+	netfs_put_read_request(rreq);
+	return;
 cleanup:
 	if (netfs_priv)
 		ops->cleanup(ractl->mapping, netfs_priv);
@@ -741,6 +960,14 @@ int netfs_readpage(struct file *file,
 	netfs_stat(&netfs_n_rh_readpage);
 	trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_readpage);
 
+	if (ops->begin_cache_operation) {
+		ret = ops->begin_cache_operation(rreq);
+		if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS) {
+			unlock_page(page);
+			goto out;
+		}
+	}
+
 	netfs_get_read_request(rreq);
 
 	atomic_set(&rreq->nr_rd_ops, 1);
@@ -762,6 +989,7 @@ int netfs_readpage(struct file *file,
 	ret = rreq->error;
 	if (ret == 0 && rreq->submitted < rreq->len)
 		ret = -EIO;
+out:
 	netfs_put_read_request(rreq);
 	return ret;
 }
diff --git a/fs/netfs/stats.c b/fs/netfs/stats.c
index dd7ad66ed07e..9ae538c85378 100644
--- a/fs/netfs/stats.c
+++ b/fs/netfs/stats.c
@@ -31,10 +31,11 @@ atomic_t netfs_n_rh_write_zskip;
 
 void netfs_stats_show(struct seq_file *m)
 {
-	seq_printf(m, "RdHelp : RA=%u RP=%u WB=%u rr=%u sr=%u\n",
+	seq_printf(m, "RdHelp : RA=%u RP=%u WB=%u WBZ=%u rr=%u sr=%u\n",
 		   atomic_read(&netfs_n_rh_readahead),
 		   atomic_read(&netfs_n_rh_readpage),
 		   atomic_read(&netfs_n_rh_write_begin),
+		   atomic_read(&netfs_n_rh_write_zskip),
 		   atomic_read(&netfs_n_rh_rreq),
 		   atomic_read(&netfs_n_rh_sreq));
 	seq_printf(m, "RdHelp : ZR=%u sh=%u sk=%u\n",
diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h
index 3f0b19dcfae7..3235ddbdcc09 100644
--- a/include/linux/fscache-cache.h
+++ b/include/linux/fscache-cache.h
@@ -304,6 +304,10 @@ struct fscache_cache_ops {
 
 	/* dissociate a cache from all the pages it was backing */
 	void (*dissociate_pages)(struct fscache_cache *cache);
+
+	/* Begin a read operation for the netfs lib */
+	int (*begin_read_operation)(struct netfs_read_request *rreq,
+				    struct fscache_retrieval *op);
 };
 
 extern struct fscache_cookie fscache_fsdef_index;
diff --git a/include/linux/fscache.h b/include/linux/fscache.h
index 1f8dc72369ee..0e4161ce347c 100644
--- a/include/linux/fscache.h
+++ b/include/linux/fscache.h
@@ -37,6 +37,7 @@ struct pagevec;
 struct fscache_cache_tag;
 struct fscache_cookie;
 struct fscache_netfs;
+struct netfs_read_request;
 
 typedef void (*fscache_rw_complete_t)(struct page *page,
 				      void *context,
@@ -217,6 +218,7 @@ extern void __fscache_readpages_cancel(struct fscache_cookie *cookie,
 extern void __fscache_disable_cookie(struct fscache_cookie *, const void *, bool);
 extern void __fscache_enable_cookie(struct fscache_cookie *, const void *, loff_t,
 				    bool (*)(void *), void *);
+extern int __fscache_begin_read_operation(struct netfs_read_request *, struct fscache_cookie *);
 
 /**
  * fscache_register_netfs - Register a filesystem as desiring caching services
@@ -831,4 +833,19 @@ void fscache_enable_cookie(struct fscache_cookie *cookie,
 					can_enable, data);
 }
 
+/**
+ * fscache_begin_read_operation - Begin a read operation for the netfs lib
+ * @rreq: The read request being undertaken
+ * @cookie: The cookie representing the cache object
+ */
+static inline
+int fscache_begin_read_operation(struct netfs_read_request *rreq,
+				 struct fscache_cookie *cookie)
+{
+	if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
+		return __fscache_begin_read_operation(rreq, cookie);
+	else
+		return -ENOBUFS;
+}
+
 #endif /* _LINUX_FSCACHE_H */
diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index ec9d1240ba49..b2589b39feb8 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -60,6 +60,17 @@ enum netfs_read_source {
 	NETFS_INVALID_READ,
 } __mode(byte);
 
+typedef void (*netfs_io_terminated_t)(void *priv, ssize_t transferred_or_error);
+
+/*
+ * Resources required to do operations on a cache.
+ */
+struct netfs_cache_resources {
+	const struct netfs_cache_ops	*ops;
+	void				*cache_priv;
+	void				*cache_priv2;
+};
+
 /*
  * Descriptor for a single component subrequest.
  */
@@ -89,11 +100,13 @@ struct netfs_read_request {
 	struct work_struct	work;
 	struct inode		*inode;		/* The file being accessed */
 	struct address_space	*mapping;	/* The mapping being accessed */
+	struct netfs_cache_resources cache_resources;
 	struct list_head	subrequests;	/* Requests to fetch I/O from disk or net */
 	void			*netfs_priv;	/* Private data for the netfs */
 	unsigned int		debug_id;
 	unsigned int		cookie_debug_id;
 	atomic_t		nr_rd_ops;	/* Number of read ops in progress */
+	atomic_t		nr_wr_ops;	/* Number of write ops in progress */
 	size_t			submitted;	/* Amount submitted for I/O so far */
 	size_t			len;		/* Length of the request */
 	short			error;		/* 0 or error that occurred */
@@ -117,6 +130,7 @@ struct netfs_read_request {
 struct netfs_read_request_ops {
 	bool (*is_cache_enabled)(struct inode *inode);
 	void (*init_rreq)(struct netfs_read_request *rreq, struct file *file);
+	int (*begin_cache_operation)(struct netfs_read_request *rreq);
 	void (*expand_readahead)(struct netfs_read_request *rreq);
 	bool (*clamp_length)(struct netfs_read_subrequest *subreq);
 	void (*issue_op)(struct netfs_read_subrequest *subreq);
@@ -127,6 +141,40 @@ struct netfs_read_request_ops {
 	void (*cleanup)(struct address_space *mapping, void *netfs_priv);
 };
 
+/*
+ * Table of operations for access to a cache.  This is obtained by
+ * rreq->ops->begin_cache_operation().
+ */
+struct netfs_cache_ops {
+	/* End an operation */
+	void (*end_operation)(struct netfs_cache_resources *cres);
+
+	/* Read data from the cache */
+	int (*read)(struct netfs_cache_resources *cres,
+		    loff_t start_pos,
+		    struct iov_iter *iter,
+		    bool seek_data,
+		    netfs_io_terminated_t term_func,
+		    void *term_func_priv);
+
+	/* Write data to the cache */
+	int (*write)(struct netfs_cache_resources *cres,
+		     loff_t start_pos,
+		     struct iov_iter *iter,
+		     netfs_io_terminated_t term_func,
+		     void *term_func_priv);
+
+	/* Expand readahead request */
+	void (*expand_readahead)(struct netfs_cache_resources *cres,
+				 loff_t *_start, size_t *_len, loff_t i_size);
+
+	/* Prepare a read operation, shortening it to a cached/uncached
+	 * boundary as appropriate.
+	 */
+	enum netfs_read_source (*prepare_read)(struct netfs_read_subrequest *subreq,
+					       loff_t i_size);
+};
+
 struct readahead_control;
 extern void netfs_readahead(struct readahead_control *,
 			    const struct netfs_read_request_ops *,

[PATCH 13/33] netfs: Hold a ref on a page when PG_private_2 is set

[David Howells]

Take a reference on a page when PG_private_2 is set and drop it once the
bit is unlocked.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Matthew Wilcox <willy@infradead.org>
cc: Linus Torvalds <torvalds@linux-foundation.org>
cc: linux-mm@kvack.org
cc: linux-cachefs@redhat.com
cc: linux-afs@lists.infradead.org
cc: linux-nfs@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: ceph-devel@vger.kernel.org
cc: v9fs-developer@lists.sourceforge.net
cc: linux-fsdevel@vger.kernel.org
Link: https://lore.kernel.org/linux-fsdevel/1331025.1612974993@warthog.procyon.org.uk/
---

 fs/netfs/read_helper.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c
index 156941e0de61..9191a3617d91 100644
--- a/fs/netfs/read_helper.c
+++ b/fs/netfs/read_helper.c
@@ -10,6 +10,7 @@
 #include <linux/fs.h>
 #include <linux/mm.h>
 #include <linux/pagemap.h>
+#include <linux/pagevec.h>
 #include <linux/slab.h>
 #include <linux/uio.h>
 #include <linux/sched/mm.h>
@@ -230,10 +231,13 @@ static void netfs_rreq_completed(struct netfs_read_request *rreq)
 static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq)
 {
 	struct netfs_read_subrequest *subreq;
+	struct pagevec pvec;
 	struct page *page;
 	pgoff_t unlocked = 0;
 	bool have_unlocked = false;
 
+	pagevec_init(&pvec);
+
 	rcu_read_lock();
 
 	list_for_each_entry(subreq, &rreq->subrequests, rreq_link) {
@@ -247,6 +251,8 @@ static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq)
 				continue;
 			unlocked = page->index;
 			unlock_page_fscache(page);
+			if (pagevec_add(&pvec, page) == 0)
+				pagevec_release(&pvec);
 			have_unlocked = true;
 		}
 	}
@@ -403,8 +409,10 @@ static void netfs_rreq_unlock(struct netfs_read_request *rreq)
 				pg_failed = true;
 				break;
 			}
-			if (test_bit(NETFS_SREQ_WRITE_TO_CACHE, &subreq->flags))
+			if (test_bit(NETFS_SREQ_WRITE_TO_CACHE, &subreq->flags)) {
+				get_page(page);
 				SetPageFsCache(page);
+			}
 			pg_failed |= subreq_failed;
 			if (pgend < iopos + subreq->len)
 				break;

[PATCH 14/33] fscache, cachefiles: Add alternate API to use kiocb for read/write to cache

[David Howells]

Add an alternate API by which the cache can be accessed through a kiocb,
doing async DIO, rather than using the current API that tells the cache
where all the pages are.

The new API is intended to be used in conjunction with the netfs helper
library.  A filesystem must pick one or the other and not mix them.

Filesystems wanting to use the new API must #define FSCACHE_USE_NEW_IO_API
before #including the header

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
cc: Christoph Hellwig <hch@lst.de>
cc: linux-cachefs@redhat.com
cc: linux-afs@lists.infradead.org
cc: linux-nfs@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: ceph-devel@vger.kernel.org
cc: v9fs-developer@lists.sourceforge.net
cc: linux-fsdevel@vger.kernel.org
---

 fs/cachefiles/Makefile    |    1 
 fs/cachefiles/interface.c |    5 -
 fs/cachefiles/internal.h  |    9 +
 fs/cachefiles/rdwr2.c     |  412 +++++++++++++++++++++++++++++++++++++++++++++
 fs/fscache/Kconfig        |    1 
 fs/fscache/Makefile       |    3 
 fs/fscache/internal.h     |    3 
 fs/fscache/page.c         |    2 
 fs/fscache/page2.c        |  117 +++++++++++++
 fs/fscache/stats.c        |    1 
 include/linux/fscache.h   |   44 +++--
 11 files changed, 578 insertions(+), 20 deletions(-)
 create mode 100644 fs/cachefiles/rdwr2.c
 create mode 100644 fs/fscache/page2.c

diff --git a/fs/cachefiles/Makefile b/fs/cachefiles/Makefile
index 891dedda5905..ea17b169ea5e 100644
--- a/fs/cachefiles/Makefile
+++ b/fs/cachefiles/Makefile
@@ -11,6 +11,7 @@ cachefiles-y := \
 	main.o \
 	namei.o \
 	rdwr.o \
+	rdwr2.o \
 	security.o \
 	xattr.o
 
diff --git a/fs/cachefiles/interface.c b/fs/cachefiles/interface.c
index 4cea5fbf695e..eaede2585d07 100644
--- a/fs/cachefiles/interface.c
+++ b/fs/cachefiles/interface.c
@@ -319,8 +319,8 @@ static void cachefiles_drop_object(struct fscache_object *_object)
 /*
  * dispose of a reference to an object
  */
-static void cachefiles_put_object(struct fscache_object *_object,
-				  enum fscache_obj_ref_trace why)
+void cachefiles_put_object(struct fscache_object *_object,
+			   enum fscache_obj_ref_trace why)
 {
 	struct cachefiles_object *object;
 	struct fscache_cache *cache;
@@ -568,4 +568,5 @@ const struct fscache_cache_ops cachefiles_cache_ops = {
 	.uncache_page		= cachefiles_uncache_page,
 	.dissociate_pages	= cachefiles_dissociate_pages,
 	.check_consistency	= cachefiles_check_consistency,
+	.begin_read_operation	= cachefiles_begin_read_operation,
 };
diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index cf9bd6401c2d..896819b80bbc 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -150,6 +150,9 @@ extern int cachefiles_has_space(struct cachefiles_cache *cache,
  */
 extern const struct fscache_cache_ops cachefiles_cache_ops;
 
+extern void cachefiles_put_object(struct fscache_object *_object,
+				  enum fscache_obj_ref_trace why);
+
 /*
  * key.c
  */
@@ -217,6 +220,12 @@ extern int cachefiles_allocate_pages(struct fscache_retrieval *,
 extern int cachefiles_write_page(struct fscache_storage *, struct page *);
 extern void cachefiles_uncache_page(struct fscache_object *, struct page *);
 
+/*
+ * rdwr2.c
+ */
+extern int cachefiles_begin_read_operation(struct netfs_read_request *,
+					   struct fscache_retrieval *);
+
 /*
  * security.c
  */
diff --git a/fs/cachefiles/rdwr2.c b/fs/cachefiles/rdwr2.c
new file mode 100644
index 000000000000..4cea5a2a2d6e
--- /dev/null
+++ b/fs/cachefiles/rdwr2.c
@@ -0,0 +1,412 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* kiocb-using read/write
+ *
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/mount.h>
+#include <linux/slab.h>
+#include <linux/file.h>
+#include <linux/uio.h>
+#include <linux/sched/mm.h>
+#include <linux/netfs.h>
+#include "internal.h"
+
+struct cachefiles_kiocb {
+	struct kiocb		iocb;
+	refcount_t		ki_refcnt;
+	loff_t			start;
+	union {
+		size_t		skipped;
+		size_t		len;
+	};
+	netfs_io_terminated_t	term_func;
+	void			*term_func_priv;
+};
+
+static inline void cachefiles_put_kiocb(struct cachefiles_kiocb *ki)
+{
+	if (refcount_dec_and_test(&ki->ki_refcnt)) {
+		fput(ki->iocb.ki_filp);
+		kfree(ki);
+	}
+}
+
+/*
+ * Handle completion of a read from the cache.
+ */
+static void cachefiles_read_complete(struct kiocb *iocb, long ret, long ret2)
+{
+	struct cachefiles_kiocb *ki = container_of(iocb, struct cachefiles_kiocb, iocb);
+
+	_enter("%ld,%ld", ret, ret2);
+
+	if (ki->term_func) {
+		if (ret < 0)
+			ki->term_func(ki->term_func_priv, ret);
+		else
+			ki->term_func(ki->term_func_priv, ki->skipped + ret);
+	}
+
+	cachefiles_put_kiocb(ki);
+}
+
+/*
+ * Initiate a read from the cache.
+ */
+static int cachefiles_read(struct netfs_cache_resources *cres,
+			   loff_t start_pos,
+			   struct iov_iter *iter,
+			   bool seek_data,
+			   netfs_io_terminated_t term_func,
+			   void *term_func_priv)
+{
+	struct cachefiles_kiocb *ki;
+	struct file *file = cres->cache_priv2;
+	unsigned int old_nofs;
+	ssize_t ret = -ENOBUFS;
+	size_t len = iov_iter_count(iter), skipped = 0;
+
+	_enter("%pD,%li,%llx,%zx/%llx",
+	       file, file_inode(file)->i_ino, start_pos, len,
+	       i_size_read(file->f_inode));
+
+	/* If the caller asked us to seek for data before doing the read, then
+	 * we should do that now.  If we find a gap, we fill it with zeros.
+	 */
+	if (seek_data) {
+		loff_t off = start_pos, off2;
+
+		off2 = vfs_llseek(file, off, SEEK_DATA);
+		if (off2 < 0 && off2 >= (loff_t)-MAX_ERRNO && off2 != -ENXIO) {
+			skipped = 0;
+			ret = off2;
+			goto presubmission_error;
+		}
+
+		if (off2 == -ENXIO || off2 >= start_pos + len) {
+			/* The region is beyond the EOF or there's no more data
+			 * in the region, so clear the rest of the buffer and
+			 * return success.
+			 */
+			iov_iter_zero(len, iter);
+			skipped = len;
+			ret = 0;
+			goto presubmission_error;
+		}
+
+		skipped = off2 - off;
+		iov_iter_zero(skipped, iter);
+	}
+
+	ret = -ENOBUFS;
+	ki = kzalloc(sizeof(struct cachefiles_kiocb), GFP_KERNEL);
+	if (!ki)
+		goto presubmission_error;
+
+	refcount_set(&ki->ki_refcnt, 2);
+	ki->iocb.ki_filp	= file;
+	ki->iocb.ki_pos		= start_pos + skipped;
+	ki->iocb.ki_flags	= IOCB_DIRECT;
+	ki->iocb.ki_hint	= ki_hint_validate(file_write_hint(file));
+	ki->iocb.ki_ioprio	= get_current_ioprio();
+	ki->skipped		= skipped;
+	ki->term_func		= term_func;
+	ki->term_func_priv	= term_func_priv;
+
+	if (ki->term_func)
+		ki->iocb.ki_complete = cachefiles_read_complete;
+
+	ret = rw_verify_area(READ, file, &ki->iocb.ki_pos, len - skipped);
+	if (ret < 0)
+		goto presubmission_error_free;
+
+	get_file(ki->iocb.ki_filp);
+
+	old_nofs = memalloc_nofs_save();
+	ret = call_read_iter(file, &ki->iocb, iter);
+	memalloc_nofs_restore(old_nofs);
+	switch (ret) {
+	case -EIOCBQUEUED:
+		goto in_progress;
+
+	case -ERESTARTSYS:
+	case -ERESTARTNOINTR:
+	case -ERESTARTNOHAND:
+	case -ERESTART_RESTARTBLOCK:
+		/* There's no easy way to restart the syscall since other AIO's
+		 * may be already running. Just fail this IO with EINTR.
+		 */
+		ret = -EINTR;
+		fallthrough;
+	default:
+		cachefiles_read_complete(&ki->iocb, ret, 0);
+		if (ret > 0)
+			ret = 0;
+		break;
+	}
+
+in_progress:
+	cachefiles_put_kiocb(ki);
+	_leave(" = %zd", ret);
+	return ret;
+
+presubmission_error_free:
+	kfree(ki);
+presubmission_error:
+	if (term_func)
+		term_func(term_func_priv, ret < 0 ? ret : skipped);
+	return ret;
+}
+
+/*
+ * Handle completion of a write to the cache.
+ */
+static void cachefiles_write_complete(struct kiocb *iocb, long ret, long ret2)
+{
+	struct cachefiles_kiocb *ki = container_of(iocb, struct cachefiles_kiocb, iocb);
+	struct inode *inode = file_inode(ki->iocb.ki_filp);
+
+	_enter("%ld,%ld", ret, ret2);
+
+	/* Tell lockdep we inherited freeze protection from submission thread */
+	__sb_writers_acquired(inode->i_sb, SB_FREEZE_WRITE);
+	__sb_end_write(inode->i_sb, SB_FREEZE_WRITE);
+
+	if (ki->term_func)
+		ki->term_func(ki->term_func_priv, ret);
+
+	cachefiles_put_kiocb(ki);
+}
+
+/*
+ * Initiate a write to the cache.
+ */
+static int cachefiles_write(struct netfs_cache_resources *cres,
+			    loff_t start_pos,
+			    struct iov_iter *iter,
+			    netfs_io_terminated_t term_func,
+			    void *term_func_priv)
+{
+	struct cachefiles_kiocb *ki;
+	struct inode *inode;
+	struct file *file = cres->cache_priv2;
+	unsigned int old_nofs;
+	ssize_t ret = -ENOBUFS;
+	size_t len = iov_iter_count(iter);
+
+	_enter("%pD,%li,%llx,%zx/%llx",
+	       file, file_inode(file)->i_ino, start_pos, len,
+	       i_size_read(file->f_inode));
+
+	ki = kzalloc(sizeof(struct cachefiles_kiocb), GFP_KERNEL);
+	if (!ki)
+		goto presubmission_error;
+
+	refcount_set(&ki->ki_refcnt, 2);
+	ki->iocb.ki_filp	= file;
+	ki->iocb.ki_pos		= start_pos;
+	ki->iocb.ki_flags	= IOCB_DIRECT | IOCB_WRITE;
+	ki->iocb.ki_hint	= ki_hint_validate(file_write_hint(file));
+	ki->iocb.ki_ioprio	= get_current_ioprio();
+	ki->start		= start_pos;
+	ki->len			= len;
+	ki->term_func		= term_func;
+	ki->term_func_priv	= term_func_priv;
+
+	if (ki->term_func)
+		ki->iocb.ki_complete = cachefiles_write_complete;
+
+	ret = rw_verify_area(WRITE, file, &ki->iocb.ki_pos, iov_iter_count(iter));
+	if (ret < 0)
+		goto presubmission_error_free;
+
+	/* Open-code file_start_write here to grab freeze protection, which
+	 * will be released by another thread in aio_complete_rw().  Fool
+	 * lockdep by telling it the lock got released so that it doesn't
+	 * complain about the held lock when we return to userspace.
+	 */
+	inode = file_inode(file);
+	__sb_start_write(inode->i_sb, SB_FREEZE_WRITE);
+	__sb_writers_release(inode->i_sb, SB_FREEZE_WRITE);
+
+	get_file(ki->iocb.ki_filp);
+
+	old_nofs = memalloc_nofs_save();
+	ret = call_write_iter(file, &ki->iocb, iter);
+	memalloc_nofs_restore(old_nofs);
+	switch (ret) {
+	case -EIOCBQUEUED:
+		goto in_progress;
+
+	case -ERESTARTSYS:
+	case -ERESTARTNOINTR:
+	case -ERESTARTNOHAND:
+	case -ERESTART_RESTARTBLOCK:
+		/* There's no easy way to restart the syscall since other AIO's
+		 * may be already running. Just fail this IO with EINTR.
+		 */
+		ret = -EINTR;
+		/* Fall through */
+	default:
+		cachefiles_write_complete(&ki->iocb, ret, 0);
+		if (ret > 0)
+			ret = 0;
+		break;
+	}
+
+in_progress:
+	cachefiles_put_kiocb(ki);
+	_leave(" = %zd", ret);
+	return ret;
+
+presubmission_error_free:
+	kfree(ki);
+presubmission_error:
+	if (term_func)
+		term_func(term_func_priv, -ENOMEM);
+	return -ENOMEM;
+}
+
+/*
+ * Prepare a read operation, shortening it to a cached/uncached
+ * boundary as appropriate.
+ */
+static enum netfs_read_source cachefiles_prepare_read(struct netfs_read_subrequest *subreq,
+						      loff_t i_size)
+{
+	struct fscache_retrieval *op = subreq->rreq->cache_resources.cache_priv;
+	struct cachefiles_object *object;
+	struct cachefiles_cache *cache;
+	const struct cred *saved_cred;
+	struct file *file = subreq->rreq->cache_resources.cache_priv2;
+	loff_t off, to;
+
+	_enter("%zx @%llx/%llx", subreq->len, subreq->start, i_size);
+
+	object = container_of(op->op.object,
+			      struct cachefiles_object, fscache);
+	cache = container_of(object->fscache.cache,
+			     struct cachefiles_cache, cache);
+
+	if (!file)
+		goto cache_fail_nosec;
+
+	if (subreq->start >= i_size)
+		return NETFS_FILL_WITH_ZEROES;
+
+	cachefiles_begin_secure(cache, &saved_cred);
+
+	off = vfs_llseek(file, subreq->start, SEEK_DATA);
+	if (off < 0 && off >= (loff_t)-MAX_ERRNO) {
+		if (off == (loff_t)-ENXIO)
+			goto download_and_store;
+		goto cache_fail;
+	}
+
+	if (off >= subreq->start + subreq->len)
+		goto download_and_store;
+
+	if (off > subreq->start) {
+		off = round_up(off, cache->bsize);
+		subreq->len = off - subreq->start;
+		goto download_and_store;
+	}
+
+	to = vfs_llseek(file, subreq->start, SEEK_HOLE);
+	if (to < 0 && to >= (loff_t)-MAX_ERRNO)
+		goto cache_fail;
+
+	if (to < subreq->start + subreq->len) {
+		if (subreq->start + subreq->len >= i_size)
+			to = round_up(to, cache->bsize);
+		else
+			to = round_down(to, cache->bsize);
+		subreq->len = to - subreq->start;
+	}
+
+	cachefiles_end_secure(cache, saved_cred);
+	return NETFS_READ_FROM_CACHE;
+
+download_and_store:
+	if (cachefiles_has_space(cache, 0, (subreq->len + PAGE_SIZE - 1) / PAGE_SIZE) == 0)
+		__set_bit(NETFS_SREQ_WRITE_TO_CACHE, &subreq->flags);
+cache_fail:
+	cachefiles_end_secure(cache, saved_cred);
+cache_fail_nosec:
+	return NETFS_DOWNLOAD_FROM_SERVER;
+}
+
+/*
+ * Clean up an operation.
+ */
+static void cachefiles_end_operation(struct netfs_cache_resources *cres)
+{
+	struct fscache_retrieval *op = cres->cache_priv;
+	struct file *file = cres->cache_priv2;
+
+	_enter("");
+
+	if (file)
+		fput(file);
+	if (op) {
+		fscache_op_complete(&op->op, false);
+		fscache_put_retrieval(op);
+	}
+
+	_leave("");
+}
+
+static const struct netfs_cache_ops cachefiles_netfs_cache_ops = {
+	.end_operation		= cachefiles_end_operation,
+	.read			= cachefiles_read,
+	.write			= cachefiles_write,
+	.expand_readahead	= NULL,
+	.prepare_read		= cachefiles_prepare_read,
+};
+
+/*
+ * Open the cache file when beginning a cache operation.
+ */
+int cachefiles_begin_read_operation(struct netfs_read_request *rreq,
+				    struct fscache_retrieval *op)
+{
+	struct cachefiles_object *object;
+	struct cachefiles_cache *cache;
+	struct path path;
+	struct file *file;
+
+	_enter("");
+
+	object = container_of(op->op.object,
+			      struct cachefiles_object, fscache);
+	cache = container_of(object->fscache.cache,
+			     struct cachefiles_cache, cache);
+
+	path.mnt = cache->mnt;
+	path.dentry = object->backer;
+	file = open_with_fake_path(&path, O_RDWR | O_LARGEFILE | O_DIRECT,
+				   d_inode(object->backer), cache->cache_cred);
+	if (IS_ERR(file))
+		return PTR_ERR(file);
+	if (!S_ISREG(file_inode(file)->i_mode))
+		goto error_file;
+	if (unlikely(!file->f_op->read_iter) ||
+	    unlikely(!file->f_op->write_iter)) {
+		pr_notice("Cache does not support read_iter and write_iter\n");
+		goto error_file;
+	}
+
+	fscache_get_retrieval(op);
+	rreq->cache_resources.cache_priv = op;
+	rreq->cache_resources.cache_priv2 = file;
+	rreq->cache_resources.ops = &cachefiles_netfs_cache_ops;
+	rreq->cookie_debug_id = object->fscache.debug_id;
+	_leave("");
+	return 0;
+
+error_file:
+	fput(file);
+	return -EIO;
+}
diff --git a/fs/fscache/Kconfig b/fs/fscache/Kconfig
index 5e796e6c38e5..427efa73b9bd 100644
--- a/fs/fscache/Kconfig
+++ b/fs/fscache/Kconfig
@@ -2,6 +2,7 @@
 
 config FSCACHE
 	tristate "General filesystem local caching manager"
+	select NETFS_SUPPORT
 	help
 	  This option enables a generic filesystem caching manager that can be
 	  used by various network and other filesystems to cache data locally.
diff --git a/fs/fscache/Makefile b/fs/fscache/Makefile
index 79e08e05ef84..38f28fec2aa3 100644
--- a/fs/fscache/Makefile
+++ b/fs/fscache/Makefile
@@ -11,7 +11,8 @@ fscache-y := \
 	netfs.o \
 	object.o \
 	operation.o \
-	page.o
+	page.o \
+	page2.o
 
 fscache-$(CONFIG_PROC_FS) += proc.o
 fscache-$(CONFIG_FSCACHE_STATS) += stats.o
diff --git a/fs/fscache/internal.h b/fs/fscache/internal.h
index 08e91efbce53..c42672cadf2d 100644
--- a/fs/fscache/internal.h
+++ b/fs/fscache/internal.h
@@ -142,6 +142,9 @@ extern int fscache_wait_for_operation_activation(struct fscache_object *,
 						 atomic_t *,
 						 atomic_t *);
 extern void fscache_invalidate_writes(struct fscache_cookie *);
+extern struct fscache_retrieval *fscache_alloc_retrieval(struct fscache_cookie *,
+							 struct address_space *,
+							 fscache_rw_complete_t, void *);
 
 /*
  * proc.c
diff --git a/fs/fscache/page.c b/fs/fscache/page.c
index 26af6fdf1538..991b0a871744 100644
--- a/fs/fscache/page.c
+++ b/fs/fscache/page.c
@@ -299,7 +299,7 @@ static void fscache_release_retrieval_op(struct fscache_operation *_op)
 /*
  * allocate a retrieval op
  */
-static struct fscache_retrieval *fscache_alloc_retrieval(
+struct fscache_retrieval *fscache_alloc_retrieval(
 	struct fscache_cookie *cookie,
 	struct address_space *mapping,
 	fscache_rw_complete_t end_io_func,
diff --git a/fs/fscache/page2.c b/fs/fscache/page2.c
new file mode 100644
index 000000000000..0eb096502067
--- /dev/null
+++ b/fs/fscache/page2.c
@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Cache data I/O routines
+ *
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#define FSCACHE_DEBUG_LEVEL PAGE
+#include <linux/module.h>
+#define FSCACHE_USE_NEW_IO_API
+#include <linux/fscache-cache.h>
+#include <linux/slab.h>
+#include <linux/netfs.h>
+#include "internal.h"
+
+/*
+ * Start a cache read operation.
+ * - we return:
+ *   -ENOMEM	- out of memory, some pages may be being read
+ *   -ERESTARTSYS - interrupted, some pages may be being read
+ *   -ENOBUFS	- no backing object or space available in which to cache any
+ *                pages not being read
+ *   -ENODATA	- no data available in the backing object for some or all of
+ *                the pages
+ *   0		- dispatched a read on all pages
+ */
+int __fscache_begin_read_operation(struct netfs_read_request *rreq,
+				   struct fscache_cookie *cookie)
+{
+	struct fscache_retrieval *op;
+	struct fscache_object *object;
+	bool wake_cookie = false;
+	int ret;
+
+	_enter("rr=%08x", rreq->debug_id);
+
+	fscache_stat(&fscache_n_retrievals);
+
+	if (hlist_empty(&cookie->backing_objects))
+		goto nobufs;
+
+	if (test_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags)) {
+		_leave(" = -ENOBUFS [invalidating]");
+		return -ENOBUFS;
+	}
+
+	ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
+
+	if (fscache_wait_for_deferred_lookup(cookie) < 0)
+		return -ERESTARTSYS;
+
+	op = fscache_alloc_retrieval(cookie, NULL, NULL, NULL);
+	if (!op)
+		return -ENOMEM;
+	//atomic_set(&op->n_pages, 1);
+	trace_fscache_page_op(cookie, NULL, &op->op, fscache_page_op_retr_multi);
+
+	spin_lock(&cookie->lock);
+
+	if (!fscache_cookie_enabled(cookie) ||
+	    hlist_empty(&cookie->backing_objects))
+		goto nobufs_unlock;
+	object = hlist_entry(cookie->backing_objects.first,
+			     struct fscache_object, cookie_link);
+
+	__fscache_use_cookie(cookie);
+	atomic_inc(&object->n_reads);
+	__set_bit(FSCACHE_OP_DEC_READ_CNT, &op->op.flags);
+
+	if (fscache_submit_op(object, &op->op) < 0)
+		goto nobufs_unlock_dec;
+	spin_unlock(&cookie->lock);
+
+	fscache_stat(&fscache_n_retrieval_ops);
+
+	/* we wait for the operation to become active, and then process it
+	 * *here*, in this thread, and not in the thread pool */
+	ret = fscache_wait_for_operation_activation(
+		object, &op->op,
+		__fscache_stat(&fscache_n_retrieval_op_waits),
+		__fscache_stat(&fscache_n_retrievals_object_dead));
+	if (ret < 0)
+		goto error;
+
+	/* ask the cache to honour the operation */
+	ret = object->cache->ops->begin_read_operation(rreq, op);
+
+error:
+	if (ret == -ENOMEM)
+		fscache_stat(&fscache_n_retrievals_nomem);
+	else if (ret == -ERESTARTSYS)
+		fscache_stat(&fscache_n_retrievals_intr);
+	else if (ret == -ENODATA)
+		fscache_stat(&fscache_n_retrievals_nodata);
+	else if (ret < 0)
+		fscache_stat(&fscache_n_retrievals_nobufs);
+	else
+		fscache_stat(&fscache_n_retrievals_ok);
+
+	fscache_put_retrieval(op);
+	_leave(" = %d", ret);
+	return ret;
+
+nobufs_unlock_dec:
+	atomic_dec(&object->n_reads);
+	wake_cookie = __fscache_unuse_cookie(cookie);
+nobufs_unlock:
+	spin_unlock(&cookie->lock);
+	fscache_put_retrieval(op);
+	if (wake_cookie)
+		__fscache_wake_unused_cookie(cookie);
+nobufs:
+	fscache_stat(&fscache_n_retrievals_nobufs);
+	_leave(" = -ENOBUFS");
+	return -ENOBUFS;
+}
+EXPORT_SYMBOL(__fscache_begin_read_operation);
diff --git a/fs/fscache/stats.c b/fs/fscache/stats.c
index a5aa93ece8c5..a7c3ed89a3e0 100644
--- a/fs/fscache/stats.c
+++ b/fs/fscache/stats.c
@@ -278,5 +278,6 @@ int fscache_stats_show(struct seq_file *m, void *v)
 		   atomic_read(&fscache_n_cache_stale_objects),
 		   atomic_read(&fscache_n_cache_retired_objects),
 		   atomic_read(&fscache_n_cache_culled_objects));
+	netfs_stats_show(m);
 	return 0;
 }
diff --git a/include/linux/fscache.h b/include/linux/fscache.h
index 0e4161ce347c..3f177faa0ac2 100644
--- a/include/linux/fscache.h
+++ b/include/linux/fscache.h
@@ -192,6 +192,10 @@ extern void __fscache_update_cookie(struct fscache_cookie *, const void *);
 extern int __fscache_attr_changed(struct fscache_cookie *);
 extern void __fscache_invalidate(struct fscache_cookie *);
 extern void __fscache_wait_on_invalidate(struct fscache_cookie *);
+
+#ifdef FSCACHE_USE_NEW_IO_API
+extern int __fscache_begin_read_operation(struct netfs_read_request *, struct fscache_cookie *);
+#else
 extern int __fscache_read_or_alloc_page(struct fscache_cookie *,
 					struct page *,
 					fscache_rw_complete_t,
@@ -215,10 +219,11 @@ extern void __fscache_uncache_all_inode_pages(struct fscache_cookie *,
 					      struct inode *);
 extern void __fscache_readpages_cancel(struct fscache_cookie *cookie,
 				       struct list_head *pages);
+#endif /* FSCACHE_USE_NEW_IO_API */
+
 extern void __fscache_disable_cookie(struct fscache_cookie *, const void *, bool);
 extern void __fscache_enable_cookie(struct fscache_cookie *, const void *, loff_t,
 				    bool (*)(void *), void *);
-extern int __fscache_begin_read_operation(struct netfs_read_request *, struct fscache_cookie *);
 
 /**
  * fscache_register_netfs - Register a filesystem as desiring caching services
@@ -500,6 +505,26 @@ int fscache_reserve_space(struct fscache_cookie *cookie, loff_t size)
 	return -ENOBUFS;
 }
 
+#ifdef FSCACHE_USE_NEW_IO_API
+
+
+/**
+ * fscache_begin_read_operation - Begin a read operation for the netfs lib
+ * @rreq: The read request being undertaken
+ * @cookie: The cookie representing the cache object
+ */
+static inline
+int fscache_begin_read_operation(struct netfs_read_request *rreq,
+				 struct fscache_cookie *cookie)
+{
+	if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
+		return __fscache_begin_read_operation(rreq, cookie);
+	else
+		return -ENOBUFS;
+}
+
+#else /* FSCACHE_USE_NEW_IO_API */
+
 /**
  * fscache_read_or_alloc_page - Read a page from the cache or allocate a block
  * in which to store it
@@ -779,6 +804,8 @@ void fscache_uncache_all_inode_pages(struct fscache_cookie *cookie,
 		__fscache_uncache_all_inode_pages(cookie, inode);
 }
 
+#endif /* FSCACHE_USE_NEW_IO_API */
+
 /**
  * fscache_disable_cookie - Disable a cookie
  * @cookie: The cookie representing the cache object
@@ -833,19 +860,4 @@ void fscache_enable_cookie(struct fscache_cookie *cookie,
 					can_enable, data);
 }
 
-/**
- * fscache_begin_read_operation - Begin a read operation for the netfs lib
- * @rreq: The read request being undertaken
- * @cookie: The cookie representing the cache object
- */
-static inline
-int fscache_begin_read_operation(struct netfs_read_request *rreq,
-				 struct fscache_cookie *cookie)
-{
-	if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
-		return __fscache_begin_read_operation(rreq, cookie);
-	else
-		return -ENOBUFS;
-}
-
 #endif /* _LINUX_FSCACHE_H */

[PATCH 15/33] afs: Disable use of the fscache I/O routines

[David Howells]

Disable use of the fscache I/O routined by the AFS filesystem.  It's about
to transition to passing iov_iters down and fscache is about to have its
I/O path to use iov_iter, so all that needs to change.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-afs@lists.infradead.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
---

 fs/afs/file.c  |  199 ++++++++++----------------------------------------------
 fs/afs/inode.c |    2 -
 fs/afs/write.c |   10 ---
 3 files changed, 36 insertions(+), 175 deletions(-)

diff --git a/fs/afs/file.c b/fs/afs/file.c
index 85f5adf21aa0..6d43713fde01 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -203,24 +203,6 @@ void afs_put_read(struct afs_read *req)
 	}
 }
 
-#ifdef CONFIG_AFS_FSCACHE
-/*
- * deal with notification that a page was read from the cache
- */
-static void afs_file_readpage_read_complete(struct page *page,
-					    void *data,
-					    int error)
-{
-	_enter("%p,%p,%d", page, data, error);
-
-	/* if the read completes with an error, we just unlock the page and let
-	 * the VM reissue the readpage */
-	if (!error)
-		SetPageUptodate(page);
-	unlock_page(page);
-}
-#endif
-
 static void afs_fetch_data_success(struct afs_operation *op)
 {
 	struct afs_vnode *vnode = op->file[0].vnode;
@@ -288,89 +270,46 @@ int afs_page_filler(void *data, struct page *page)
 	if (test_bit(AFS_VNODE_DELETED, &vnode->flags))
 		goto error;
 
-	/* is it cached? */
-#ifdef CONFIG_AFS_FSCACHE
-	ret = fscache_read_or_alloc_page(vnode->cache,
-					 page,
-					 afs_file_readpage_read_complete,
-					 NULL,
-					 GFP_KERNEL);
-#else
-	ret = -ENOBUFS;
-#endif
-	switch (ret) {
-		/* read BIO submitted (page in cache) */
-	case 0:
-		break;
-
-		/* page not yet cached */
-	case -ENODATA:
-		_debug("cache said ENODATA");
-		goto go_on;
-
-		/* page will not be cached */
-	case -ENOBUFS:
-		_debug("cache said ENOBUFS");
-
-		fallthrough;
-	default:
-	go_on:
-		req = kzalloc(struct_size(req, array, 1), GFP_KERNEL);
-		if (!req)
-			goto enomem;
-
-		/* We request a full page.  If the page is a partial one at the
-		 * end of the file, the server will return a short read and the
-		 * unmarshalling code will clear the unfilled space.
-		 */
-		refcount_set(&req->usage, 1);
-		req->pos = (loff_t)page->index << PAGE_SHIFT;
-		req->len = PAGE_SIZE;
-		req->nr_pages = 1;
-		req->pages = req->array;
-		req->pages[0] = page;
-		get_page(page);
-
-		/* read the contents of the file from the server into the
-		 * page */
-		ret = afs_fetch_data(vnode, key, req);
-		afs_put_read(req);
-
-		if (ret < 0) {
-			if (ret == -ENOENT) {
-				_debug("got NOENT from server"
-				       " - marking file deleted and stale");
-				set_bit(AFS_VNODE_DELETED, &vnode->flags);
-				ret = -ESTALE;
-			}
-
-#ifdef CONFIG_AFS_FSCACHE
-			fscache_uncache_page(vnode->cache, page);
-#endif
-			BUG_ON(PageFsCache(page));
-
-			if (ret == -EINTR ||
-			    ret == -ENOMEM ||
-			    ret == -ERESTARTSYS ||
-			    ret == -EAGAIN)
-				goto error;
-			goto io_error;
-		}
+	req = kzalloc(struct_size(req, array, 1), GFP_KERNEL);
+	if (!req)
+		goto enomem;
 
-		SetPageUptodate(page);
+	/* We request a full page.  If the page is a partial one at the
+	 * end of the file, the server will return a short read and the
+	 * unmarshalling code will clear the unfilled space.
+	 */
+	refcount_set(&req->usage, 1);
+	req->pos = (loff_t)page->index << PAGE_SHIFT;
+	req->len = PAGE_SIZE;
+	req->nr_pages = 1;
+	req->pages = req->array;
+	req->pages[0] = page;
+	get_page(page);
+
+	/* read the contents of the file from the server into the
+	 * page */
+	ret = afs_fetch_data(vnode, key, req);
+	afs_put_read(req);
 
-		/* send the page to the cache */
-#ifdef CONFIG_AFS_FSCACHE
-		if (PageFsCache(page) &&
-		    fscache_write_page(vnode->cache, page, vnode->status.size,
-				       GFP_KERNEL) != 0) {
-			fscache_uncache_page(vnode->cache, page);
-			BUG_ON(PageFsCache(page));
+	if (ret < 0) {
+		if (ret == -ENOENT) {
+			_debug("got NOENT from server"
+			       " - marking file deleted and stale");
+			set_bit(AFS_VNODE_DELETED, &vnode->flags);
+			ret = -ESTALE;
 		}
-#endif
-		unlock_page(page);
+
+		if (ret == -EINTR ||
+		    ret == -ENOMEM ||
+		    ret == -ERESTARTSYS ||
+		    ret == -EAGAIN)
+			goto error;
+		goto io_error;
 	}
 
+	SetPageUptodate(page);
+	unlock_page(page);
+
 	_leave(" = 0");
 	return 0;
 
@@ -416,23 +355,10 @@ static int afs_readpage(struct file *file, struct page *page)
  */
 static void afs_readpages_page_done(struct afs_read *req)
 {
-#ifdef CONFIG_AFS_FSCACHE
-	struct afs_vnode *vnode = req->vnode;
-#endif
 	struct page *page = req->pages[req->index];
 
 	req->pages[req->index] = NULL;
 	SetPageUptodate(page);
-
-	/* send the page to the cache */
-#ifdef CONFIG_AFS_FSCACHE
-	if (PageFsCache(page) &&
-	    fscache_write_page(vnode->cache, page, vnode->status.size,
-			       GFP_KERNEL) != 0) {
-		fscache_uncache_page(vnode->cache, page);
-		BUG_ON(PageFsCache(page));
-	}
-#endif
 	unlock_page(page);
 	put_page(page);
 }
@@ -491,9 +417,6 @@ static int afs_readpages_one(struct file *file, struct address_space *mapping,
 		index = page->index;
 		if (add_to_page_cache_lru(page, mapping, index,
 					  readahead_gfp_mask(mapping))) {
-#ifdef CONFIG_AFS_FSCACHE
-			fscache_uncache_page(vnode->cache, page);
-#endif
 			put_page(page);
 			break;
 		}
@@ -526,9 +449,6 @@ static int afs_readpages_one(struct file *file, struct address_space *mapping,
 	for (i = 0; i < req->nr_pages; i++) {
 		page = req->pages[i];
 		if (page) {
-#ifdef CONFIG_AFS_FSCACHE
-			fscache_uncache_page(vnode->cache, page);
-#endif
 			SetPageError(page);
 			unlock_page(page);
 		}
@@ -560,37 +480,6 @@ static int afs_readpages(struct file *file, struct address_space *mapping,
 	}
 
 	/* attempt to read as many of the pages as possible */
-#ifdef CONFIG_AFS_FSCACHE
-	ret = fscache_read_or_alloc_pages(vnode->cache,
-					  mapping,
-					  pages,
-					  &nr_pages,
-					  afs_file_readpage_read_complete,
-					  NULL,
-					  mapping_gfp_mask(mapping));
-#else
-	ret = -ENOBUFS;
-#endif
-
-	switch (ret) {
-		/* all pages are being read from the cache */
-	case 0:
-		BUG_ON(!list_empty(pages));
-		BUG_ON(nr_pages != 0);
-		_leave(" = 0 [reading all]");
-		return 0;
-
-		/* there were pages that couldn't be read from the cache */
-	case -ENODATA:
-	case -ENOBUFS:
-		break;
-
-		/* other error */
-	default:
-		_leave(" = %d", ret);
-		return ret;
-	}
-
 	while (!list_empty(pages)) {
 		ret = afs_readpages_one(file, mapping, pages);
 		if (ret < 0)
@@ -670,17 +559,6 @@ static void afs_invalidatepage(struct page *page, unsigned int offset,
 
 	BUG_ON(!PageLocked(page));
 
-#ifdef CONFIG_AFS_FSCACHE
-	/* we clean up only if the entire page is being invalidated */
-	if (offset == 0 && length == PAGE_SIZE) {
-		if (PageFsCache(page)) {
-			struct afs_vnode *vnode = AFS_FS_I(page->mapping->host);
-			fscache_wait_on_page_write(vnode->cache, page);
-			fscache_uncache_page(vnode->cache, page);
-		}
-	}
-#endif
-
 	if (PagePrivate(page))
 		afs_invalidate_dirty(page, offset, length);
 
@@ -702,13 +580,6 @@ static int afs_releasepage(struct page *page, gfp_t gfp_flags)
 
 	/* deny if page is being written to the cache and the caller hasn't
 	 * elected to wait */
-#ifdef CONFIG_AFS_FSCACHE
-	if (!fscache_maybe_release_page(vnode->cache, page, gfp_flags)) {
-		_leave(" = F [cache busy]");
-		return 0;
-	}
-#endif
-
 	if (PagePrivate(page)) {
 		priv = (unsigned long)detach_page_private(page);
 		trace_afs_page_dirty(vnode, tracepoint_string("rel"),
diff --git a/fs/afs/inode.c b/fs/afs/inode.c
index b0d7b892090d..48edd8d724d2 100644
--- a/fs/afs/inode.c
+++ b/fs/afs/inode.c
@@ -428,7 +428,7 @@ static void afs_get_inode_cache(struct afs_vnode *vnode)
 	} __packed key;
 	struct afs_vnode_cache_aux aux;
 
-	if (vnode->status.type == AFS_FTYPE_DIR) {
+	if (vnode->status.type != AFS_FTYPE_FILE) {
 		vnode->cache = NULL;
 		return;
 	}
diff --git a/fs/afs/write.c b/fs/afs/write.c
index c9195fc67fd8..92eaa88000d7 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -847,9 +847,6 @@ vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
 	/* Wait for the page to be written to the cache before we allow it to
 	 * be modified.  We then assume the entire page will need writing back.
 	 */
-#ifdef CONFIG_AFS_FSCACHE
-	fscache_wait_on_page_write(vnode->cache, vmf->page);
-#endif
 
 	if (PageWriteback(vmf->page) &&
 	    wait_on_page_bit_killable(vmf->page, PG_writeback) < 0)
@@ -936,12 +933,5 @@ int afs_launder_page(struct page *page)
 	priv = (unsigned long)detach_page_private(page);
 	trace_afs_page_dirty(vnode, tracepoint_string("laundered"),
 			     page->index, priv);
-
-#ifdef CONFIG_AFS_FSCACHE
-	if (PageFsCache(page)) {
-		fscache_wait_on_page_write(vnode->cache, page);
-		fscache_uncache_page(vnode->cache, page);
-	}
-#endif
 	return ret;
 }

[PATCH 16/33] afs: Pass page into dirty region helpers to provide THP size

[David Howells]

Pass a pointer to the page being accessed into the dirty region helpers so
that the size of the page can be determined in case it's a transparent huge
page.

This also required the page to be passed into the afs_page_dirty trace
point - so there's no need to specifically pass in the index or private
data as these can be retrieved directly from the page struct.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-afs@lists.infradead.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
---

 fs/afs/file.c              |   20 +++++++--------
 fs/afs/internal.h          |   16 ++++++------
 fs/afs/write.c             |   60 ++++++++++++++++++--------------------------
 include/trace/events/afs.h |   23 ++++++++++-------
 4 files changed, 55 insertions(+), 64 deletions(-)

diff --git a/fs/afs/file.c b/fs/afs/file.c
index 6d43713fde01..21868bfc3a44 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -515,8 +515,8 @@ static void afs_invalidate_dirty(struct page *page, unsigned int offset,
 		return;
 
 	/* We may need to shorten the dirty region */
-	f = afs_page_dirty_from(priv);
-	t = afs_page_dirty_to(priv);
+	f = afs_page_dirty_from(page, priv);
+	t = afs_page_dirty_to(page, priv);
 
 	if (t <= offset || f >= end)
 		return; /* Doesn't overlap */
@@ -534,17 +534,17 @@ static void afs_invalidate_dirty(struct page *page, unsigned int offset,
 	if (f == t)
 		goto undirty;
 
-	priv = afs_page_dirty(f, t);
+	priv = afs_page_dirty(page, f, t);
 	set_page_private(page, priv);
-	trace_afs_page_dirty(vnode, tracepoint_string("trunc"), page->index, priv);
+	trace_afs_page_dirty(vnode, tracepoint_string("trunc"), page);
 	return;
 
 undirty:
-	trace_afs_page_dirty(vnode, tracepoint_string("undirty"), page->index, priv);
+	trace_afs_page_dirty(vnode, tracepoint_string("undirty"), page);
 	clear_page_dirty_for_io(page);
 full_invalidate:
-	priv = (unsigned long)detach_page_private(page);
-	trace_afs_page_dirty(vnode, tracepoint_string("inval"), page->index, priv);
+	detach_page_private(page);
+	trace_afs_page_dirty(vnode, tracepoint_string("inval"), page);
 }
 
 /*
@@ -572,7 +572,6 @@ static void afs_invalidatepage(struct page *page, unsigned int offset,
 static int afs_releasepage(struct page *page, gfp_t gfp_flags)
 {
 	struct afs_vnode *vnode = AFS_FS_I(page->mapping->host);
-	unsigned long priv;
 
 	_enter("{{%llx:%llu}[%lu],%lx},%x",
 	       vnode->fid.vid, vnode->fid.vnode, page->index, page->flags,
@@ -581,9 +580,8 @@ static int afs_releasepage(struct page *page, gfp_t gfp_flags)
 	/* deny if page is being written to the cache and the caller hasn't
 	 * elected to wait */
 	if (PagePrivate(page)) {
-		priv = (unsigned long)detach_page_private(page);
-		trace_afs_page_dirty(vnode, tracepoint_string("rel"),
-				     page->index, priv);
+		detach_page_private(page);
+		trace_afs_page_dirty(vnode, tracepoint_string("rel"), page);
 	}
 
 	/* indicate that the page can be released */
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 0d150a29e39e..cd545e7dbfb8 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -875,31 +875,31 @@ struct afs_vnode_cache_aux {
 #define __AFS_PAGE_PRIV_MMAPPED	0x8000UL
 #endif
 
-static inline unsigned int afs_page_dirty_resolution(void)
+static inline unsigned int afs_page_dirty_resolution(struct page *page)
 {
-	int shift = PAGE_SHIFT - (__AFS_PAGE_PRIV_SHIFT - 1);
+	int shift = thp_order(page) + PAGE_SHIFT - (__AFS_PAGE_PRIV_SHIFT - 1);
 	return (shift > 0) ? shift : 0;
 }
 
-static inline size_t afs_page_dirty_from(unsigned long priv)
+static inline size_t afs_page_dirty_from(struct page *page, unsigned long priv)
 {
 	unsigned long x = priv & __AFS_PAGE_PRIV_MASK;
 
 	/* The lower bound is inclusive */
-	return x << afs_page_dirty_resolution();
+	return x << afs_page_dirty_resolution(page);
 }
 
-static inline size_t afs_page_dirty_to(unsigned long priv)
+static inline size_t afs_page_dirty_to(struct page *page, unsigned long priv)
 {
 	unsigned long x = (priv >> __AFS_PAGE_PRIV_SHIFT) & __AFS_PAGE_PRIV_MASK;
 
 	/* The upper bound is immediately beyond the region */
-	return (x + 1) << afs_page_dirty_resolution();
+	return (x + 1) << afs_page_dirty_resolution(page);
 }
 
-static inline unsigned long afs_page_dirty(size_t from, size_t to)
+static inline unsigned long afs_page_dirty(struct page *page, size_t from, size_t to)
 {
-	unsigned int res = afs_page_dirty_resolution();
+	unsigned int res = afs_page_dirty_resolution(page);
 	from >>= res;
 	to = (to - 1) >> res;
 	return (to << __AFS_PAGE_PRIV_SHIFT) | from;
diff --git a/fs/afs/write.c b/fs/afs/write.c
index 92eaa88000d7..9d0cef35ecba 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -112,15 +112,14 @@ int afs_write_begin(struct file *file, struct address_space *mapping,
 	t = f = 0;
 	if (PagePrivate(page)) {
 		priv = page_private(page);
-		f = afs_page_dirty_from(priv);
-		t = afs_page_dirty_to(priv);
+		f = afs_page_dirty_from(page, priv);
+		t = afs_page_dirty_to(page, priv);
 		ASSERTCMP(f, <=, t);
 	}
 
 	if (f != t) {
 		if (PageWriteback(page)) {
-			trace_afs_page_dirty(vnode, tracepoint_string("alrdy"),
-					     page->index, priv);
+			trace_afs_page_dirty(vnode, tracepoint_string("alrdy"), page);
 			goto flush_conflicting_write;
 		}
 		/* If the file is being filled locally, allow inter-write
@@ -204,21 +203,19 @@ int afs_write_end(struct file *file, struct address_space *mapping,
 
 	if (PagePrivate(page)) {
 		priv = page_private(page);
-		f = afs_page_dirty_from(priv);
-		t = afs_page_dirty_to(priv);
+		f = afs_page_dirty_from(page, priv);
+		t = afs_page_dirty_to(page, priv);
 		if (from < f)
 			f = from;
 		if (to > t)
 			t = to;
-		priv = afs_page_dirty(f, t);
+		priv = afs_page_dirty(page, f, t);
 		set_page_private(page, priv);
-		trace_afs_page_dirty(vnode, tracepoint_string("dirty+"),
-				     page->index, priv);
+		trace_afs_page_dirty(vnode, tracepoint_string("dirty+"), page);
 	} else {
-		priv = afs_page_dirty(from, to);
+		priv = afs_page_dirty(page, from, to);
 		attach_page_private(page, (void *)priv);
-		trace_afs_page_dirty(vnode, tracepoint_string("dirty"),
-				     page->index, priv);
+		trace_afs_page_dirty(vnode, tracepoint_string("dirty"), page);
 	}
 
 	set_page_dirty(page);
@@ -321,7 +318,6 @@ static void afs_pages_written_back(struct afs_vnode *vnode,
 				   pgoff_t first, pgoff_t last)
 {
 	struct pagevec pv;
-	unsigned long priv;
 	unsigned count, loop;
 
 	_enter("{%llx:%llu},{%lx-%lx}",
@@ -340,9 +336,9 @@ static void afs_pages_written_back(struct afs_vnode *vnode,
 		ASSERTCMP(pv.nr, ==, count);
 
 		for (loop = 0; loop < count; loop++) {
-			priv = (unsigned long)detach_page_private(pv.pages[loop]);
+			detach_page_private(pv.pages[loop]);
 			trace_afs_page_dirty(vnode, tracepoint_string("clear"),
-					     pv.pages[loop]->index, priv);
+					     pv.pages[loop]);
 			end_page_writeback(pv.pages[loop]);
 		}
 		first += count;
@@ -516,15 +512,13 @@ static int afs_write_back_from_locked_page(struct address_space *mapping,
 	 */
 	start = primary_page->index;
 	priv = page_private(primary_page);
-	offset = afs_page_dirty_from(priv);
-	to = afs_page_dirty_to(priv);
-	trace_afs_page_dirty(vnode, tracepoint_string("store"),
-			     primary_page->index, priv);
+	offset = afs_page_dirty_from(primary_page, priv);
+	to = afs_page_dirty_to(primary_page, priv);
+	trace_afs_page_dirty(vnode, tracepoint_string("store"), primary_page);
 
 	WARN_ON(offset == to);
 	if (offset == to)
-		trace_afs_page_dirty(vnode, tracepoint_string("WARN"),
-				     primary_page->index, priv);
+		trace_afs_page_dirty(vnode, tracepoint_string("WARN"), primary_page);
 
 	if (start >= final_page ||
 	    (to < PAGE_SIZE && !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags)))
@@ -562,8 +556,8 @@ static int afs_write_back_from_locked_page(struct address_space *mapping,
 			}
 
 			priv = page_private(page);
-			f = afs_page_dirty_from(priv);
-			t = afs_page_dirty_to(priv);
+			f = afs_page_dirty_from(page, priv);
+			t = afs_page_dirty_to(page, priv);
 			if (f != 0 &&
 			    !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags)) {
 				unlock_page(page);
@@ -571,8 +565,7 @@ static int afs_write_back_from_locked_page(struct address_space *mapping,
 			}
 			to = t;
 
-			trace_afs_page_dirty(vnode, tracepoint_string("store+"),
-					     page->index, priv);
+			trace_afs_page_dirty(vnode, tracepoint_string("store+"), page);
 
 			if (!clear_page_dirty_for_io(page))
 				BUG();
@@ -861,14 +854,13 @@ vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
 	 */
 	wait_on_page_writeback(vmf->page);
 
-	priv = afs_page_dirty(0, PAGE_SIZE);
+	priv = afs_page_dirty(vmf->page, 0, PAGE_SIZE);
 	priv = afs_page_dirty_mmapped(priv);
-	trace_afs_page_dirty(vnode, tracepoint_string("mkwrite"),
-			     vmf->page->index, priv);
 	if (PagePrivate(vmf->page))
 		set_page_private(vmf->page, priv);
 	else
 		attach_page_private(vmf->page, (void *)priv);
+	trace_afs_page_dirty(vnode, tracepoint_string("mkwrite"), vmf->page);
 	file_update_time(file);
 
 	sb_end_pagefault(inode->i_sb);
@@ -921,17 +913,15 @@ int afs_launder_page(struct page *page)
 		f = 0;
 		t = PAGE_SIZE;
 		if (PagePrivate(page)) {
-			f = afs_page_dirty_from(priv);
-			t = afs_page_dirty_to(priv);
+			f = afs_page_dirty_from(page, priv);
+			t = afs_page_dirty_to(page, priv);
 		}
 
-		trace_afs_page_dirty(vnode, tracepoint_string("launder"),
-				     page->index, priv);
+		trace_afs_page_dirty(vnode, tracepoint_string("launder"), page);
 		ret = afs_store_data(mapping, page->index, page->index, t, f, true);
 	}
 
-	priv = (unsigned long)detach_page_private(page);
-	trace_afs_page_dirty(vnode, tracepoint_string("laundered"),
-			     page->index, priv);
+	detach_page_private(page);
+	trace_afs_page_dirty(vnode, tracepoint_string("laundered"), page);
 	return ret;
 }
diff --git a/include/trace/events/afs.h b/include/trace/events/afs.h
index 4a5cc8c64be3..9203cf6a8c53 100644
--- a/include/trace/events/afs.h
+++ b/include/trace/events/afs.h
@@ -969,30 +969,33 @@ TRACE_EVENT(afs_dir_check_failed,
 	    );
 
 TRACE_EVENT(afs_page_dirty,
-	    TP_PROTO(struct afs_vnode *vnode, const char *where,
-		     pgoff_t page, unsigned long priv),
+	    TP_PROTO(struct afs_vnode *vnode, const char *where, struct page *page),
 
-	    TP_ARGS(vnode, where, page, priv),
+	    TP_ARGS(vnode, where, page),
 
 	    TP_STRUCT__entry(
 		    __field(struct afs_vnode *,		vnode		)
 		    __field(const char *,		where		)
 		    __field(pgoff_t,			page		)
-		    __field(unsigned long,		priv		)
+		    __field(unsigned long,		from		)
+		    __field(unsigned long,		to		)
 			     ),
 
 	    TP_fast_assign(
 		    __entry->vnode = vnode;
 		    __entry->where = where;
-		    __entry->page = page;
-		    __entry->priv = priv;
+		    __entry->page = page->index;
+		    __entry->from = afs_page_dirty_from(page, page->private);
+		    __entry->to = afs_page_dirty_to(page, page->private);
+		    __entry->to |= (afs_is_page_dirty_mmapped(page->private) ?
+				    (1UL << (BITS_PER_LONG - 1)) : 0);
 			   ),
 
-	    TP_printk("vn=%p %lx %s %zx-%zx%s",
+	    TP_printk("vn=%p %lx %s %lx-%lx%s",
 		      __entry->vnode, __entry->page, __entry->where,
-		      afs_page_dirty_from(__entry->priv),
-		      afs_page_dirty_to(__entry->priv),
-		      afs_is_page_dirty_mmapped(__entry->priv) ? " M" : "")
+		      __entry->from,
+		      __entry->to & ~(1UL << (BITS_PER_LONG - 1)),
+		      __entry->to & (1UL << (BITS_PER_LONG - 1)) ? " M" : "")
 	    );
 
 TRACE_EVENT(afs_call_state,

[PATCH 17/33] afs: Print the operation debug_id when logging an unexpected data version

[David Howells]

Print the afs_operation debug_id when logging an unexpected change in the
data version.  This allows the logged message to be matched against
tracelines.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-afs@lists.infradead.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
---

 fs/afs/inode.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/afs/inode.c b/fs/afs/inode.c
index 48edd8d724d2..0bc7273100b8 100644
--- a/fs/afs/inode.c
+++ b/fs/afs/inode.c
@@ -215,11 +215,12 @@ static void afs_apply_status(struct afs_operation *op,
 
 	if (vp->dv_before + vp->dv_delta != status->data_version) {
 		if (test_bit(AFS_VNODE_CB_PROMISED, &vnode->flags))
-			pr_warn("kAFS: vnode modified {%llx:%llu} %llx->%llx %s\n",
+			pr_warn("kAFS: vnode modified {%llx:%llu} %llx->%llx %s (op=%x)\n",
 				vnode->fid.vid, vnode->fid.vnode,
 				(unsigned long long)vp->dv_before + vp->dv_delta,
 				(unsigned long long)status->data_version,
-				op->type ? op->type->name : "???");
+				op->type ? op->type->name : "???",
+				op->debug_id);
 
 		vnode->invalid_before = status->data_version;
 		if (vnode->status.type == AFS_FTYPE_DIR) {

[PATCH 18/33] afs: Move key to afs_read struct

[David Howells]

Stash the key used to authenticate read operations in the afs_read struct.
This will be necessary to reissue the operation against the server if a
read from the cache fails in upcoming cache changes.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-afs@lists.infradead.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
---

 fs/afs/dir.c      |    3 ++-
 fs/afs/file.c     |   16 +++++++++-------
 fs/afs/internal.h |    3 ++-
 fs/afs/write.c    |   12 ++++++------
 4 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/fs/afs/dir.c b/fs/afs/dir.c
index 7bd659ad959e..96e9e2e60d97 100644
--- a/fs/afs/dir.c
+++ b/fs/afs/dir.c
@@ -241,6 +241,7 @@ static struct afs_read *afs_read_dir(struct afs_vnode *dvnode, struct key *key)
 		return ERR_PTR(-ENOMEM);
 
 	refcount_set(&req->usage, 1);
+	req->key = key_get(key);
 	req->nr_pages = nr_pages;
 	req->actual_len = i_size; /* May change */
 	req->len = nr_pages * PAGE_SIZE; /* We can ask for more than there is */
@@ -305,7 +306,7 @@ static struct afs_read *afs_read_dir(struct afs_vnode *dvnode, struct key *key)
 
 	if (!test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags)) {
 		trace_afs_reload_dir(dvnode);
-		ret = afs_fetch_data(dvnode, key, req);
+		ret = afs_fetch_data(dvnode, req);
 		if (ret < 0)
 			goto error_unlock;
 
diff --git a/fs/afs/file.c b/fs/afs/file.c
index 21868bfc3a44..d23192b3b933 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -199,6 +199,7 @@ void afs_put_read(struct afs_read *req)
 			if (req->pages != req->array)
 				kfree(req->pages);
 		}
+		key_put(req->key);
 		kfree(req);
 	}
 }
@@ -229,7 +230,7 @@ static const struct afs_operation_ops afs_fetch_data_operation = {
 /*
  * Fetch file data from the volume.
  */
-int afs_fetch_data(struct afs_vnode *vnode, struct key *key, struct afs_read *req)
+int afs_fetch_data(struct afs_vnode *vnode, struct afs_read *req)
 {
 	struct afs_operation *op;
 
@@ -238,9 +239,9 @@ int afs_fetch_data(struct afs_vnode *vnode, struct key *key, struct afs_read *re
 	       vnode->fid.vid,
 	       vnode->fid.vnode,
 	       vnode->fid.unique,
-	       key_serial(key));
+	       key_serial(req->key));
 
-	op = afs_alloc_operation(key, vnode->volume);
+	op = afs_alloc_operation(req->key, vnode->volume);
 	if (IS_ERR(op))
 		return PTR_ERR(op);
 
@@ -279,6 +280,7 @@ int afs_page_filler(void *data, struct page *page)
 	 * unmarshalling code will clear the unfilled space.
 	 */
 	refcount_set(&req->usage, 1);
+	req->key = key_get(key);
 	req->pos = (loff_t)page->index << PAGE_SHIFT;
 	req->len = PAGE_SIZE;
 	req->nr_pages = 1;
@@ -288,7 +290,7 @@ int afs_page_filler(void *data, struct page *page)
 
 	/* read the contents of the file from the server into the
 	 * page */
-	ret = afs_fetch_data(vnode, key, req);
+	ret = afs_fetch_data(vnode, req);
 	afs_put_read(req);
 
 	if (ret < 0) {
@@ -373,7 +375,6 @@ static int afs_readpages_one(struct file *file, struct address_space *mapping,
 	struct afs_read *req;
 	struct list_head *p;
 	struct page *first, *page;
-	struct key *key = afs_file_key(file);
 	pgoff_t index;
 	int ret, n, i;
 
@@ -397,6 +398,7 @@ static int afs_readpages_one(struct file *file, struct address_space *mapping,
 
 	refcount_set(&req->usage, 1);
 	req->vnode = vnode;
+	req->key = key_get(afs_file_key(file));
 	req->page_done = afs_readpages_page_done;
 	req->pos = first->index;
 	req->pos <<= PAGE_SHIFT;
@@ -426,11 +428,11 @@ static int afs_readpages_one(struct file *file, struct address_space *mapping,
 	} while (req->nr_pages < n);
 
 	if (req->nr_pages == 0) {
-		kfree(req);
+		afs_put_read(req);
 		return 0;
 	}
 
-	ret = afs_fetch_data(vnode, key, req);
+	ret = afs_fetch_data(vnode, req);
 	if (ret < 0)
 		goto error;
 
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index cd545e7dbfb8..4b255d10f726 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -204,6 +204,7 @@ struct afs_read {
 	loff_t			actual_len;	/* How much we're actually getting */
 	loff_t			remain;		/* Amount remaining */
 	loff_t			file_size;	/* File size returned by server */
+	struct key		*key;		/* The key to use to reissue the read */
 	afs_dataversion_t	data_version;	/* Version number returned by server */
 	refcount_t		usage;
 	unsigned int		index;		/* Which page we're reading into */
@@ -1045,7 +1046,7 @@ extern int afs_cache_wb_key(struct afs_vnode *, struct afs_file *);
 extern void afs_put_wb_key(struct afs_wb_key *);
 extern int afs_open(struct inode *, struct file *);
 extern int afs_release(struct inode *, struct file *);
-extern int afs_fetch_data(struct afs_vnode *, struct key *, struct afs_read *);
+extern int afs_fetch_data(struct afs_vnode *, struct afs_read *);
 extern int afs_page_filler(void *, struct page *);
 extern void afs_put_read(struct afs_read *);
 
diff --git a/fs/afs/write.c b/fs/afs/write.c
index 9d0cef35ecba..7eba0d3201ba 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -25,9 +25,10 @@ int afs_set_page_dirty(struct page *page)
 /*
  * partly or wholly fill a page that's under preparation for writing
  */
-static int afs_fill_page(struct afs_vnode *vnode, struct key *key,
+static int afs_fill_page(struct file *file,
 			 loff_t pos, unsigned int len, struct page *page)
 {
+	struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
 	struct afs_read *req;
 	size_t p;
 	void *data;
@@ -49,6 +50,7 @@ static int afs_fill_page(struct afs_vnode *vnode, struct key *key,
 		return -ENOMEM;
 
 	refcount_set(&req->usage, 1);
+	req->key = key_get(afs_file_key(file));
 	req->pos = pos;
 	req->len = len;
 	req->nr_pages = 1;
@@ -56,7 +58,7 @@ static int afs_fill_page(struct afs_vnode *vnode, struct key *key,
 	req->pages[0] = page;
 	get_page(page);
 
-	ret = afs_fetch_data(vnode, key, req);
+	ret = afs_fetch_data(vnode, req);
 	afs_put_read(req);
 	if (ret < 0) {
 		if (ret == -ENOENT) {
@@ -80,7 +82,6 @@ int afs_write_begin(struct file *file, struct address_space *mapping,
 {
 	struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
 	struct page *page;
-	struct key *key = afs_file_key(file);
 	unsigned long priv;
 	unsigned f, from = pos & (PAGE_SIZE - 1);
 	unsigned t, to = from + len;
@@ -95,7 +96,7 @@ int afs_write_begin(struct file *file, struct address_space *mapping,
 		return -ENOMEM;
 
 	if (!PageUptodate(page) && len != PAGE_SIZE) {
-		ret = afs_fill_page(vnode, key, pos & PAGE_MASK, PAGE_SIZE, page);
+		ret = afs_fill_page(file, pos & PAGE_MASK, PAGE_SIZE, page);
 		if (ret < 0) {
 			unlock_page(page);
 			put_page(page);
@@ -163,7 +164,6 @@ int afs_write_end(struct file *file, struct address_space *mapping,
 		  struct page *page, void *fsdata)
 {
 	struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
-	struct key *key = afs_file_key(file);
 	unsigned long priv;
 	unsigned int f, from = pos & (PAGE_SIZE - 1);
 	unsigned int t, to = from + copied;
@@ -193,7 +193,7 @@ int afs_write_end(struct file *file, struct address_space *mapping,
 			 * unmarshalling routine will take care of clearing any
 			 * bits that are beyond the EOF.
 			 */
-			ret = afs_fill_page(vnode, key, pos + copied,
+			ret = afs_fill_page(file, pos + copied,
 					    len - copied, page);
 			if (ret < 0)
 				goto out;

[PATCH 19/33] afs: Don't truncate iter during data fetch

[David Howells]

Don't truncate the iterator to correspond to the actual data size when
fetching the data from the server - rather, pass the length we want to read
to rxrpc.

This will allow the clear-after-read code in future to simply clear the
remaining iterator capacity rather than having to reinitialise the
iterator.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-afs@lists.infradead.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
---

 fs/afs/fsclient.c      |    6 ++++--
 fs/afs/internal.h      |    6 ++++++
 fs/afs/rxrpc.c         |   13 +++++++++----
 fs/afs/yfsclient.c     |    6 ++++--
 include/net/af_rxrpc.h |    2 +-
 net/rxrpc/recvmsg.c    |    9 +++++----
 6 files changed, 29 insertions(+), 13 deletions(-)

diff --git a/fs/afs/fsclient.c b/fs/afs/fsclient.c
index 1d95ed9dd86e..4a57c6c6f12b 100644
--- a/fs/afs/fsclient.c
+++ b/fs/afs/fsclient.c
@@ -305,8 +305,9 @@ static int afs_deliver_fs_fetch_data(struct afs_call *call)
 	unsigned int size;
 	int ret;
 
-	_enter("{%u,%zu/%llu}",
-	       call->unmarshall, iov_iter_count(call->iter), req->actual_len);
+	_enter("{%u,%zu,%zu/%llu}",
+	       call->unmarshall, call->iov_len, iov_iter_count(call->iter),
+	       req->actual_len);
 
 	switch (call->unmarshall) {
 	case 0:
@@ -343,6 +344,7 @@ static int afs_deliver_fs_fetch_data(struct afs_call *call)
 			size = PAGE_SIZE - req->offset;
 		else
 			size = req->remain;
+		call->iov_len = size;
 		call->bvec[0].bv_len = size;
 		call->bvec[0].bv_offset = req->offset;
 		call->bvec[0].bv_page = req->pages[req->index];
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 4b255d10f726..1badc7ed0487 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -104,6 +104,7 @@ struct afs_call {
 	struct afs_server	*server;	/* The fileserver record if fs op (pins ref) */
 	struct afs_vlserver	*vlserver;	/* The vlserver record if vl op */
 	void			*request;	/* request data (first part) */
+	size_t			iov_len;	/* Size of *iter to be used */
 	struct iov_iter		def_iter;	/* Default buffer/data iterator */
 	struct iov_iter		*iter;		/* Iterator currently in use */
 	union {	/* Convenience for ->def_iter */
@@ -1270,6 +1271,7 @@ static inline void afs_make_op_call(struct afs_operation *op, struct afs_call *c
 
 static inline void afs_extract_begin(struct afs_call *call, void *buf, size_t size)
 {
+	call->iov_len = size;
 	call->kvec[0].iov_base = buf;
 	call->kvec[0].iov_len = size;
 	iov_iter_kvec(&call->def_iter, READ, call->kvec, 1, size);
@@ -1277,21 +1279,25 @@ static inline void afs_extract_begin(struct afs_call *call, void *buf, size_t si
 
 static inline void afs_extract_to_tmp(struct afs_call *call)
 {
+	call->iov_len = sizeof(call->tmp);
 	afs_extract_begin(call, &call->tmp, sizeof(call->tmp));
 }
 
 static inline void afs_extract_to_tmp64(struct afs_call *call)
 {
+	call->iov_len = sizeof(call->tmp64);
 	afs_extract_begin(call, &call->tmp64, sizeof(call->tmp64));
 }
 
 static inline void afs_extract_discard(struct afs_call *call, size_t size)
 {
+	call->iov_len = size;
 	iov_iter_discard(&call->def_iter, READ, size);
 }
 
 static inline void afs_extract_to_buf(struct afs_call *call, size_t size)
 {
+	call->iov_len = size;
 	afs_extract_begin(call, call->buffer, size);
 }
 
diff --git a/fs/afs/rxrpc.c b/fs/afs/rxrpc.c
index 8be709cb8542..0ec38b758f29 100644
--- a/fs/afs/rxrpc.c
+++ b/fs/afs/rxrpc.c
@@ -363,6 +363,7 @@ void afs_make_call(struct afs_addr_cursor *ac, struct afs_call *call, gfp_t gfp)
 	struct rxrpc_call *rxcall;
 	struct msghdr msg;
 	struct kvec iov[1];
+	size_t len;
 	s64 tx_total_len;
 	int ret;
 
@@ -466,9 +467,10 @@ void afs_make_call(struct afs_addr_cursor *ac, struct afs_call *call, gfp_t gfp)
 		rxrpc_kernel_abort_call(call->net->socket, rxcall,
 					RX_USER_ABORT, ret, "KSD");
 	} else {
+		len = 0;
 		iov_iter_kvec(&msg.msg_iter, READ, NULL, 0, 0);
 		rxrpc_kernel_recv_data(call->net->socket, rxcall,
-				       &msg.msg_iter, false,
+				       &msg.msg_iter, &len, false,
 				       &call->abort_code, &call->service_id);
 		ac->abort_code = call->abort_code;
 		ac->responded = true;
@@ -504,6 +506,7 @@ void afs_make_call(struct afs_addr_cursor *ac, struct afs_call *call, gfp_t gfp)
 static void afs_deliver_to_call(struct afs_call *call)
 {
 	enum afs_call_state state;
+	size_t len;
 	u32 abort_code, remote_abort = 0;
 	int ret;
 
@@ -516,10 +519,11 @@ static void afs_deliver_to_call(struct afs_call *call)
 	       state == AFS_CALL_SV_AWAIT_ACK
 	       ) {
 		if (state == AFS_CALL_SV_AWAIT_ACK) {
+			len = 0;
 			iov_iter_kvec(&call->def_iter, READ, NULL, 0, 0);
 			ret = rxrpc_kernel_recv_data(call->net->socket,
 						     call->rxcall, &call->def_iter,
-						     false, &remote_abort,
+						     &len, false, &remote_abort,
 						     &call->service_id);
 			trace_afs_receive_data(call, &call->def_iter, false, ret);
 
@@ -929,10 +933,11 @@ int afs_extract_data(struct afs_call *call, bool want_more)
 	u32 remote_abort = 0;
 	int ret;
 
-	_enter("{%s,%zu},%d", call->type->name, iov_iter_count(iter), want_more);
+	_enter("{%s,%zu,%zu},%d",
+	       call->type->name, call->iov_len, iov_iter_count(iter), want_more);
 
 	ret = rxrpc_kernel_recv_data(net->socket, call->rxcall, iter,
-				     want_more, &remote_abort,
+				     &call->iov_len, want_more, &remote_abort,
 				     &call->service_id);
 	if (ret == 0 || ret == -EAGAIN)
 		return ret;
diff --git a/fs/afs/yfsclient.c b/fs/afs/yfsclient.c
index bd787e71a657..6c45d32da13c 100644
--- a/fs/afs/yfsclient.c
+++ b/fs/afs/yfsclient.c
@@ -363,8 +363,9 @@ static int yfs_deliver_fs_fetch_data64(struct afs_call *call)
 	unsigned int size;
 	int ret;
 
-	_enter("{%u,%zu/%llu}",
-	       call->unmarshall, iov_iter_count(call->iter), req->actual_len);
+	_enter("{%u,%zu, %zu/%llu}",
+	       call->unmarshall, call->iov_len, iov_iter_count(call->iter),
+	       req->actual_len);
 
 	switch (call->unmarshall) {
 	case 0:
@@ -396,6 +397,7 @@ static int yfs_deliver_fs_fetch_data64(struct afs_call *call)
 			size = PAGE_SIZE - req->offset;
 		else
 			size = req->remain;
+		call->iov_len = size;
 		call->bvec[0].bv_len = size;
 		call->bvec[0].bv_offset = req->offset;
 		call->bvec[0].bv_page = req->pages[req->index];
diff --git a/include/net/af_rxrpc.h b/include/net/af_rxrpc.h
index f6abcc0bbd6e..cee5f83c0f11 100644
--- a/include/net/af_rxrpc.h
+++ b/include/net/af_rxrpc.h
@@ -53,7 +53,7 @@ int rxrpc_kernel_send_data(struct socket *, struct rxrpc_call *,
 			   struct msghdr *, size_t,
 			   rxrpc_notify_end_tx_t);
 int rxrpc_kernel_recv_data(struct socket *, struct rxrpc_call *,
-			   struct iov_iter *, bool, u32 *, u16 *);
+			   struct iov_iter *, size_t *, bool, u32 *, u16 *);
 bool rxrpc_kernel_abort_call(struct socket *, struct rxrpc_call *,
 			     u32, int, const char *);
 void rxrpc_kernel_end_call(struct socket *, struct rxrpc_call *);
diff --git a/net/rxrpc/recvmsg.c b/net/rxrpc/recvmsg.c
index fef3573fdc8b..eca6dda26c77 100644
--- a/net/rxrpc/recvmsg.c
+++ b/net/rxrpc/recvmsg.c
@@ -669,6 +669,7 @@ int rxrpc_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
  * @sock: The socket that the call exists on
  * @call: The call to send data through
  * @iter: The buffer to receive into
+ * @_len: The amount of data we want to receive (decreased on return)
  * @want_more: True if more data is expected to be read
  * @_abort: Where the abort code is stored if -ECONNABORTED is returned
  * @_service: Where to store the actual service ID (may be upgraded)
@@ -684,7 +685,7 @@ int rxrpc_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
  * *_abort should also be initialised to 0.
  */
 int rxrpc_kernel_recv_data(struct socket *sock, struct rxrpc_call *call,
-			   struct iov_iter *iter,
+			   struct iov_iter *iter, size_t *_len,
 			   bool want_more, u32 *_abort, u16 *_service)
 {
 	size_t offset = 0;
@@ -692,7 +693,7 @@ int rxrpc_kernel_recv_data(struct socket *sock, struct rxrpc_call *call,
 
 	_enter("{%d,%s},%zu,%d",
 	       call->debug_id, rxrpc_call_states[call->state],
-	       iov_iter_count(iter), want_more);
+	       *_len, want_more);
 
 	ASSERTCMP(call->state, !=, RXRPC_CALL_SERVER_SECURING);
 
@@ -703,8 +704,8 @@ int rxrpc_kernel_recv_data(struct socket *sock, struct rxrpc_call *call,
 	case RXRPC_CALL_SERVER_RECV_REQUEST:
 	case RXRPC_CALL_SERVER_ACK_REQUEST:
 		ret = rxrpc_recvmsg_data(sock, call, NULL, iter,
-					 iov_iter_count(iter), 0,
-					 &offset);
+					 *_len, 0, &offset);
+		*_len -= offset;
 		if (ret < 0)
 			goto out;
 

[PATCH 20/33] afs: Log remote unmarshalling errors

[David Howells]

Log unmarshalling errors reported by the peer (ie. it can't parse what we
sent it).  Limit the maximum number of messages to 3.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-afs@lists.infradead.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
---

 fs/afs/rxrpc.c |   34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/fs/afs/rxrpc.c b/fs/afs/rxrpc.c
index 0ec38b758f29..ae68576f822f 100644
--- a/fs/afs/rxrpc.c
+++ b/fs/afs/rxrpc.c
@@ -500,6 +500,39 @@ void afs_make_call(struct afs_addr_cursor *ac, struct afs_call *call, gfp_t gfp)
 	_leave(" = %d", ret);
 }
 
+/*
+ * Log remote abort codes that indicate that we have a protocol disagreement
+ * with the server.
+ */
+static void afs_log_error(struct afs_call *call, s32 remote_abort)
+{
+	static int max = 0;
+	const char *msg;
+	int m;
+
+	switch (remote_abort) {
+	case RX_EOF:		 msg = "unexpected EOF";	break;
+	case RXGEN_CC_MARSHAL:	 msg = "client marshalling";	break;
+	case RXGEN_CC_UNMARSHAL: msg = "client unmarshalling";	break;
+	case RXGEN_SS_MARSHAL:	 msg = "server marshalling";	break;
+	case RXGEN_SS_UNMARSHAL: msg = "server unmarshalling";	break;
+	case RXGEN_DECODE:	 msg = "opcode decode";		break;
+	case RXGEN_SS_XDRFREE:	 msg = "server XDR cleanup";	break;
+	case RXGEN_CC_XDRFREE:	 msg = "client XDR cleanup";	break;
+	case -32:		 msg = "insufficient data";	break;
+	default:
+		return;
+	}
+
+	m = max;
+	if (m < 3) {
+		max = m + 1;
+		pr_notice("kAFS: Peer reported %s failure on %s [%pISp]\n",
+			  msg, call->type->name,
+			  &call->alist->addrs[call->addr_ix].transport);
+	}
+}
+
 /*
  * deliver messages to a call
  */
@@ -563,6 +596,7 @@ static void afs_deliver_to_call(struct afs_call *call)
 			goto out;
 		case -ECONNABORTED:
 			ASSERTCMP(state, ==, AFS_CALL_COMPLETE);
+			afs_log_error(call, call->abort_code);
 			goto done;
 		case -ENOTSUPP:
 			abort_code = RXGEN_OPCODE;

[PATCH 21/33] afs: Set up the iov_iter before calling afs_extract_data()

[David Howells]

afs_extract_data() sets up a temporary iov_iter and passes it to AF_RXRPC
each time it is called to describe the remaining buffer to be filled.

Instead:

 (1) Put an iterator in the afs_call struct.

 (2) Set the iterator for each marshalling stage to load data into the
     appropriate places.  A number of convenience functions are provided to
     this end (eg. afs_extract_to_buf()).

     This iterator is then passed to afs_extract_data().

 (3) Use the new ITER_MAPPING iterator when reading data to load directly
     into the inode's pages without needing to create a list of them.

This will allow O_DIRECT calls to be supported in future patches.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-afs@lists.infradead.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
---

 fs/afs/dir.c       |  222 +++++++++++++++++++++++++++++++++++-----------------
 fs/afs/file.c      |  190 ++++++++++++++++++++++++++-------------------
 fs/afs/fsclient.c  |   54 +++----------
 fs/afs/internal.h  |   16 ++--
 fs/afs/write.c     |   27 ++++--
 fs/afs/yfsclient.c |   54 +++----------
 6 files changed, 314 insertions(+), 249 deletions(-)

diff --git a/fs/afs/dir.c b/fs/afs/dir.c
index 96e9e2e60d97..526a49889dff 100644
--- a/fs/afs/dir.c
+++ b/fs/afs/dir.c
@@ -102,6 +102,35 @@ struct afs_lookup_cookie {
 	struct afs_fid		fids[50];
 };
 
+/*
+ * Drop the refs that we're holding on the pages we were reading into.  We've
+ * got refs on the first nr_pages pages.
+ */
+static void afs_dir_read_cleanup(struct afs_read *req)
+{
+	struct address_space *mapping = req->vnode->vfs_inode.i_mapping;
+	struct page *page;
+	pgoff_t last = req->nr_pages - 1;
+
+	XA_STATE(xas, &mapping->i_pages, 0);
+
+	if (unlikely(!req->nr_pages))
+		return;
+
+	rcu_read_lock();
+	xas_for_each(&xas, page, last) {
+		if (xas_retry(&xas, page))
+			continue;
+		BUG_ON(xa_is_value(page));
+		BUG_ON(PageCompound(page));
+		ASSERTCMP(page->mapping, ==, mapping);
+
+		put_page(page);
+	}
+
+	rcu_read_unlock();
+}
+
 /*
  * check that a directory page is valid
  */
@@ -127,7 +156,7 @@ static bool afs_dir_check_page(struct afs_vnode *dvnode, struct page *page,
 	qty /= sizeof(union afs_xdr_dir_block);
 
 	/* check them */
-	dbuf = kmap(page);
+	dbuf = kmap_atomic(page);
 	for (tmp = 0; tmp < qty; tmp++) {
 		if (dbuf->blocks[tmp].hdr.magic != AFS_DIR_MAGIC) {
 			printk("kAFS: %s(%lx): bad magic %d/%d is %04hx\n",
@@ -146,7 +175,7 @@ static bool afs_dir_check_page(struct afs_vnode *dvnode, struct page *page,
 		((u8 *)&dbuf->blocks[tmp])[AFS_DIR_BLOCK_SIZE - 1] = 0;
 	}
 
-	kunmap(page);
+	kunmap_atomic(dbuf);
 
 checked:
 	afs_stat_v(dvnode, n_read_dir);
@@ -157,35 +186,74 @@ static bool afs_dir_check_page(struct afs_vnode *dvnode, struct page *page,
 }
 
 /*
- * Check the contents of a directory that we've just read.
+ * Dump the contents of a directory.
  */
-static bool afs_dir_check_pages(struct afs_vnode *dvnode, struct afs_read *req)
+static void afs_dir_dump(struct afs_vnode *dvnode, struct afs_read *req)
 {
 	struct afs_xdr_dir_page *dbuf;
-	unsigned int i, j, qty = PAGE_SIZE / sizeof(union afs_xdr_dir_block);
+	struct address_space *mapping = dvnode->vfs_inode.i_mapping;
+	struct page *page;
+	unsigned int i, qty = PAGE_SIZE / sizeof(union afs_xdr_dir_block);
+	pgoff_t last = req->nr_pages - 1;
 
-	for (i = 0; i < req->nr_pages; i++)
-		if (!afs_dir_check_page(dvnode, req->pages[i], req->actual_len))
-			goto bad;
-	return true;
+	XA_STATE(xas, &mapping->i_pages, 0);
 
-bad:
-	pr_warn("DIR %llx:%llx f=%llx l=%llx al=%llx r=%llx\n",
+	pr_warn("DIR %llx:%llx f=%llx l=%llx al=%llx\n",
 		dvnode->fid.vid, dvnode->fid.vnode,
-		req->file_size, req->len, req->actual_len, req->remain);
-	pr_warn("DIR %llx %x %x %x\n",
-		req->pos, req->index, req->nr_pages, req->offset);
+		req->file_size, req->len, req->actual_len);
+	pr_warn("DIR %llx %x %zx %zx\n",
+		req->pos, req->nr_pages,
+		req->iter->iov_offset,  iov_iter_count(req->iter));
 
-	for (i = 0; i < req->nr_pages; i++) {
-		dbuf = kmap(req->pages[i]);
-		for (j = 0; j < qty; j++) {
-			union afs_xdr_dir_block *block = &dbuf->blocks[j];
+	xas_for_each(&xas, page, last) {
+		if (xas_retry(&xas, page))
+			continue;
+
+		BUG_ON(PageCompound(page));
+		BUG_ON(page->mapping != mapping);
+
+		dbuf = kmap_atomic(page);
+		for (i = 0; i < qty; i++) {
+			union afs_xdr_dir_block *block = &dbuf->blocks[i];
 
-			pr_warn("[%02x] %32phN\n", i * qty + j, block);
+			pr_warn("[%02lx] %32phN\n", page->index * qty + i, block);
 		}
-		kunmap(req->pages[i]);
+		kunmap_atomic(dbuf);
 	}
-	return false;
+}
+
+/*
+ * Check all the pages in a directory.  All the pages are held pinned.
+ */
+static int afs_dir_check(struct afs_vnode *dvnode, struct afs_read *req)
+{
+	struct address_space *mapping = dvnode->vfs_inode.i_mapping;
+	struct page *page;
+	pgoff_t last = req->nr_pages - 1;
+	int ret = 0;
+
+	XA_STATE(xas, &mapping->i_pages, 0);
+
+	if (unlikely(!req->nr_pages))
+		return 0;
+
+	rcu_read_lock();
+	xas_for_each(&xas, page, last) {
+		if (xas_retry(&xas, page))
+			continue;
+
+		BUG_ON(PageCompound(page));
+		BUG_ON(page->mapping != mapping);
+
+		if (!afs_dir_check_page(dvnode, page, req->file_size)) {
+			afs_dir_dump(dvnode, req);
+			ret = -EIO;
+			break;
+		}
+	}
+
+	rcu_read_unlock();
+	return ret;
 }
 
 /*
@@ -214,58 +282,57 @@ static struct afs_read *afs_read_dir(struct afs_vnode *dvnode, struct key *key)
 {
 	struct afs_read *req;
 	loff_t i_size;
-	int nr_pages, nr_inline, i, n;
-	int ret = -ENOMEM;
+	int nr_pages, i, n;
+	int ret;
+
+	_enter("");
 
-retry:
+	req = kzalloc(sizeof(*req), GFP_KERNEL);
+	if (!req)
+		return ERR_PTR(-ENOMEM);
+
+	refcount_set(&req->usage, 1);
+	req->vnode = dvnode;
+	req->key = key_get(key);
+	req->cleanup = afs_dir_read_cleanup;
+
+expand:
 	i_size = i_size_read(&dvnode->vfs_inode);
-	if (i_size < 2048)
-		return ERR_PTR(afs_bad(dvnode, afs_file_error_dir_small));
+	if (i_size < 2048) {
+		ret = afs_bad(dvnode, afs_file_error_dir_small);
+		goto error;
+	}
 	if (i_size > 2048 * 1024) {
 		trace_afs_file_error(dvnode, -EFBIG, afs_file_error_dir_big);
-		return ERR_PTR(-EFBIG);
+		ret = -EFBIG;
+		goto error;
 	}
 
 	_enter("%llu", i_size);
 
-	/* Get a request record to hold the page list.  We want to hold it
-	 * inline if we can, but we don't want to make an order 1 allocation.
-	 */
 	nr_pages = (i_size + PAGE_SIZE - 1) / PAGE_SIZE;
-	nr_inline = nr_pages;
-	if (nr_inline > (PAGE_SIZE - sizeof(*req)) / sizeof(struct page *))
-		nr_inline = 0;
 
-	req = kzalloc(struct_size(req, array, nr_inline), GFP_KERNEL);
-	if (!req)
-		return ERR_PTR(-ENOMEM);
-
-	refcount_set(&req->usage, 1);
-	req->key = key_get(key);
-	req->nr_pages = nr_pages;
 	req->actual_len = i_size; /* May change */
 	req->len = nr_pages * PAGE_SIZE; /* We can ask for more than there is */
 	req->data_version = dvnode->status.data_version; /* May change */
-	if (nr_inline > 0) {
-		req->pages = req->array;
-	} else {
-		req->pages = kcalloc(nr_pages, sizeof(struct page *),
-				     GFP_KERNEL);
-		if (!req->pages)
-			goto error;
-	}
+	iov_iter_xarray(&req->def_iter, READ, &dvnode->vfs_inode.i_mapping->i_pages,
+			0, i_size);
+	req->iter = &req->def_iter;
 
-	/* Get a list of all the pages that hold or will hold the directory
-	 * content.  We need to fill in any gaps that we might find where the
-	 * memory reclaimer has been at work.  If there are any gaps, we will
+	/* Fill in any gaps that we might find where the memory reclaimer has
+	 * been at work and pin all the pages.  If there are any gaps, we will
 	 * need to reread the entire directory contents.
 	 */
-	i = 0;
-	do {
+	i = req->nr_pages;
+	while (i < nr_pages) {
+		struct page *pages[8], *page;
+
 		n = find_get_pages_contig(dvnode->vfs_inode.i_mapping, i,
-					  req->nr_pages - i,
-					  req->pages + i);
-		_debug("find %u at %u/%u", n, i, req->nr_pages);
+					  min_t(unsigned int, nr_pages - i,
+						ARRAY_SIZE(pages)),
+					  pages);
+		_debug("find %u at %u/%u", n, i, nr_pages);
+
 		if (n == 0) {
 			gfp_t gfp = dvnode->vfs_inode.i_mapping->gfp_mask;
 
@@ -273,22 +340,24 @@ static struct afs_read *afs_read_dir(struct afs_vnode *dvnode, struct key *key)
 				afs_stat_v(dvnode, n_inval);
 
 			ret = -ENOMEM;
-			req->pages[i] = __page_cache_alloc(gfp);
-			if (!req->pages[i])
+			page = __page_cache_alloc(gfp);
+			if (!page)
 				goto error;
-			ret = add_to_page_cache_lru(req->pages[i],
+			ret = add_to_page_cache_lru(page,
 						    dvnode->vfs_inode.i_mapping,
 						    i, gfp);
 			if (ret < 0)
 				goto error;
 
-			attach_page_private(req->pages[i], (void *)1);
-			unlock_page(req->pages[i]);
+			attach_page_private(page, (void *)1);
+			unlock_page(page);
+			req->nr_pages++;
 			i++;
 		} else {
+			req->nr_pages += n;
 			i += n;
 		}
-	} while (i < req->nr_pages);
+	}
 
 	/* If we're going to reload, we need to lock all the pages to prevent
 	 * races.
@@ -312,12 +381,17 @@ static struct afs_read *afs_read_dir(struct afs_vnode *dvnode, struct key *key)
 
 		task_io_account_read(PAGE_SIZE * req->nr_pages);
 
-		if (req->len < req->file_size)
-			goto content_has_grown;
+		if (req->len < req->file_size) {
+			/* The content has grown, so we need to expand the
+			 * buffer.
+			 */
+			up_write(&dvnode->validate_lock);
+			goto expand;
+		}
 
 		/* Validate the data we just read. */
-		ret = -EIO;
-		if (!afs_dir_check_pages(dvnode, req))
+		ret = afs_dir_check(dvnode, req);
+		if (ret < 0)
 			goto error_unlock;
 
 		// TODO: Trim excess pages
@@ -335,11 +409,6 @@ static struct afs_read *afs_read_dir(struct afs_vnode *dvnode, struct key *key)
 	afs_put_read(req);
 	_leave(" = %d", ret);
 	return ERR_PTR(ret);
-
-content_has_grown:
-	up_write(&dvnode->validate_lock);
-	afs_put_read(req);
-	goto retry;
 }
 
 /*
@@ -449,6 +518,7 @@ static int afs_dir_iterate(struct inode *dir, struct dir_context *ctx,
 	struct afs_read *req;
 	struct page *page;
 	unsigned blkoff, limit;
+	void __rcu **slot;
 	int ret;
 
 	_enter("{%lu},%u,,", dir->i_ino, (unsigned)ctx->pos);
@@ -473,9 +543,15 @@ static int afs_dir_iterate(struct inode *dir, struct dir_context *ctx,
 		blkoff = ctx->pos & ~(sizeof(union afs_xdr_dir_block) - 1);
 
 		/* Fetch the appropriate page from the directory and re-add it
-		 * to the LRU.
+		 * to the LRU.  We have all the pages pinned with an extra ref.
 		 */
-		page = req->pages[blkoff / PAGE_SIZE];
+		rcu_read_lock();
+		page = NULL;
+		slot = radix_tree_lookup_slot(&dvnode->vfs_inode.i_mapping->i_pages,
+					      blkoff / PAGE_SIZE);
+		if (slot)
+			page = radix_tree_deref_slot(slot);
+		rcu_read_unlock();
 		if (!page) {
 			ret = afs_bad(dvnode, afs_file_error_dir_missing_page);
 			break;
diff --git a/fs/afs/file.c b/fs/afs/file.c
index d23192b3b933..f1bab69e99d4 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -184,21 +184,72 @@ int afs_release(struct inode *inode, struct file *file)
 	return ret;
 }
 
+/*
+ * Handle completion of a read operation.
+ */
+static void afs_file_read_done(struct afs_read *req)
+{
+	struct afs_vnode *vnode = req->vnode;
+	struct page *page;
+	pgoff_t index = req->pos >> PAGE_SHIFT;
+	pgoff_t last = index + req->nr_pages - 1;
+
+	XA_STATE(xas, &vnode->vfs_inode.i_mapping->i_pages, index);
+
+	if (iov_iter_count(req->iter) > 0) {
+		/* The read was short - clear the excess buffer. */
+		_debug("afterclear %zx %zx %llx/%llx",
+		       req->iter->iov_offset,
+		       iov_iter_count(req->iter),
+		       req->actual_len, req->len);
+		iov_iter_zero(iov_iter_count(req->iter), req->iter);
+	}
+
+	rcu_read_lock();
+	xas_for_each(&xas, page, last) {
+		page_endio(page, false, 0);
+		put_page(page);
+	}
+	rcu_read_unlock();
+
+	task_io_account_read(req->len);
+	req->cleanup = NULL;
+}
+
+/*
+ * Dispose of our locks and refs on the pages if the read failed.
+ */
+static void afs_file_read_cleanup(struct afs_read *req)
+{
+	struct page *page;
+	pgoff_t index = req->pos >> PAGE_SHIFT;
+	pgoff_t last = index + req->nr_pages - 1;
+
+	if (req->iter) {
+		XA_STATE(xas, &req->vnode->vfs_inode.i_mapping->i_pages, index);
+
+		_enter("%lu,%u,%zu", index, req->nr_pages, iov_iter_count(req->iter));
+
+		rcu_read_lock();
+		xas_for_each(&xas, page, last) {
+			BUG_ON(xa_is_value(page));
+			BUG_ON(PageCompound(page));
+
+			page_endio(page, false, req->error);
+			put_page(page);
+		}
+		rcu_read_unlock();
+	}
+}
+
 /*
  * Dispose of a ref to a read record.
  */
 void afs_put_read(struct afs_read *req)
 {
-	int i;
-
 	if (refcount_dec_and_test(&req->usage)) {
-		if (req->pages) {
-			for (i = 0; i < req->nr_pages; i++)
-				if (req->pages[i])
-					put_page(req->pages[i]);
-			if (req->pages != req->array)
-				kfree(req->pages);
-		}
+		if (req->cleanup)
+			req->cleanup(req);
 		key_put(req->key);
 		kfree(req);
 	}
@@ -216,6 +267,7 @@ static void afs_fetch_data_success(struct afs_operation *op)
 
 static void afs_fetch_data_put(struct afs_operation *op)
 {
+	op->fetch.req->error = op->error;
 	afs_put_read(op->fetch.req);
 }
 
@@ -255,12 +307,11 @@ int afs_fetch_data(struct afs_vnode *vnode, struct afs_read *req)
 /*
  * read page from file, directory or symlink, given a key to use
  */
-int afs_page_filler(void *data, struct page *page)
+static int afs_page_filler(struct key *key, struct page *page)
 {
 	struct inode *inode = page->mapping->host;
 	struct afs_vnode *vnode = AFS_FS_I(inode);
 	struct afs_read *req;
-	struct key *key = data;
 	int ret;
 
 	_enter("{%x},{%lu},{%lu}", key_serial(key), inode->i_ino, page->index);
@@ -271,53 +322,52 @@ int afs_page_filler(void *data, struct page *page)
 	if (test_bit(AFS_VNODE_DELETED, &vnode->flags))
 		goto error;
 
-	req = kzalloc(struct_size(req, array, 1), GFP_KERNEL);
+	req = kzalloc(sizeof(struct afs_read), GFP_KERNEL);
 	if (!req)
 		goto enomem;
 
-	/* We request a full page.  If the page is a partial one at the
-	 * end of the file, the server will return a short read and the
-	 * unmarshalling code will clear the unfilled space.
-	 */
 	refcount_set(&req->usage, 1);
-	req->key = key_get(key);
-	req->pos = (loff_t)page->index << PAGE_SHIFT;
-	req->len = PAGE_SIZE;
-	req->nr_pages = 1;
-	req->pages = req->array;
-	req->pages[0] = page;
+	req->vnode		= vnode;
+	req->key		= key_get(key);
+	req->pos		= (loff_t)page->index << PAGE_SHIFT;
+	req->len		= PAGE_SIZE;
+	req->nr_pages		= 1;
+	req->done		= afs_file_read_done;
+	req->cleanup		= afs_file_read_cleanup;
+
 	get_page(page);
+	iov_iter_xarray(&req->def_iter, READ, &page->mapping->i_pages,
+			req->pos, req->len);
+	req->iter = &req->def_iter;
 
-	/* read the contents of the file from the server into the
-	 * page */
 	ret = afs_fetch_data(vnode, req);
-	afs_put_read(req);
-
-	if (ret < 0) {
-		if (ret == -ENOENT) {
-			_debug("got NOENT from server"
-			       " - marking file deleted and stale");
-			set_bit(AFS_VNODE_DELETED, &vnode->flags);
-			ret = -ESTALE;
-		}
-
-		if (ret == -EINTR ||
-		    ret == -ENOMEM ||
-		    ret == -ERESTARTSYS ||
-		    ret == -EAGAIN)
-			goto error;
-		goto io_error;
-	}
-
-	SetPageUptodate(page);
-	unlock_page(page);
+	if (ret < 0)
+		goto fetch_error;
 
+	afs_put_read(req);
 	_leave(" = 0");
 	return 0;
 
-io_error:
-	SetPageError(page);
-	goto error;
+fetch_error:
+	switch (ret) {
+	case -EINTR:
+	case -ENOMEM:
+	case -ERESTARTSYS:
+	case -EAGAIN:
+		afs_put_read(req);
+		goto error;
+	case -ENOENT:
+		_debug("got NOENT from server - marking file deleted and stale");
+		set_bit(AFS_VNODE_DELETED, &vnode->flags);
+		ret = -ESTALE;
+		/* Fall through */
+	default:
+		page_endio(page, false, ret);
+		afs_put_read(req);
+		_leave(" = %d", ret);
+		return ret;
+	}
+
 enomem:
 	ret = -ENOMEM;
 error:
@@ -352,19 +402,6 @@ static int afs_readpage(struct file *file, struct page *page)
 	return ret;
 }
 
-/*
- * Make pages available as they're filled.
- */
-static void afs_readpages_page_done(struct afs_read *req)
-{
-	struct page *page = req->pages[req->index];
-
-	req->pages[req->index] = NULL;
-	SetPageUptodate(page);
-	unlock_page(page);
-	put_page(page);
-}
-
 /*
  * Read a contiguous set of pages.
  */
@@ -376,7 +413,7 @@ static int afs_readpages_one(struct file *file, struct address_space *mapping,
 	struct list_head *p;
 	struct page *first, *page;
 	pgoff_t index;
-	int ret, n, i;
+	int ret, n;
 
 	/* Count the number of contiguous pages at the front of the list.  Note
 	 * that the list goes prev-wards rather than next-wards.
@@ -392,21 +429,20 @@ static int afs_readpages_one(struct file *file, struct address_space *mapping,
 		n++;
 	}
 
-	req = kzalloc(struct_size(req, array, n), GFP_NOFS);
+	req = kzalloc(sizeof(struct afs_read), GFP_NOFS);
 	if (!req)
 		return -ENOMEM;
 
 	refcount_set(&req->usage, 1);
 	req->vnode = vnode;
 	req->key = key_get(afs_file_key(file));
-	req->page_done = afs_readpages_page_done;
+	req->done = afs_file_read_done;
+	req->cleanup = afs_file_read_cleanup;
 	req->pos = first->index;
 	req->pos <<= PAGE_SHIFT;
-	req->pages = req->array;
 
-	/* Transfer the pages to the request.  We add them in until one fails
-	 * to add to the LRU and then we stop (as that'll make a hole in the
-	 * contiguous run.
+	/* Add pages to the LRU until it fails.  We keep the pages ref'd and
+	 * locked until the read is complete.
 	 *
 	 * Note that it's possible for the file size to change whilst we're
 	 * doing this, but we rely on the server returning less than we asked
@@ -423,8 +459,7 @@ static int afs_readpages_one(struct file *file, struct address_space *mapping,
 			break;
 		}
 
-		req->pages[req->nr_pages++] = page;
-		req->len += PAGE_SIZE;
+		req->nr_pages++;
 	} while (req->nr_pages < n);
 
 	if (req->nr_pages == 0) {
@@ -432,30 +467,25 @@ static int afs_readpages_one(struct file *file, struct address_space *mapping,
 		return 0;
 	}
 
+	req->len = req->nr_pages * PAGE_SIZE;
+	iov_iter_xarray(&req->def_iter, READ, &file->f_mapping->i_pages,
+			req->pos, req->len);
+	req->iter = &req->def_iter;
+
 	ret = afs_fetch_data(vnode, req);
 	if (ret < 0)
 		goto error;
 
-	task_io_account_read(PAGE_SIZE * req->nr_pages);
 	afs_put_read(req);
 	return 0;
 
 error:
 	if (ret == -ENOENT) {
-		_debug("got NOENT from server"
-		       " - marking file deleted and stale");
+		_debug("got NOENT from server - marking file deleted and stale");
 		set_bit(AFS_VNODE_DELETED, &vnode->flags);
 		ret = -ESTALE;
 	}
 
-	for (i = 0; i < req->nr_pages; i++) {
-		page = req->pages[i];
-		if (page) {
-			SetPageError(page);
-			unlock_page(page);
-		}
-	}
-
 	afs_put_read(req);
 	return ret;
 }
diff --git a/fs/afs/fsclient.c b/fs/afs/fsclient.c
index 4a57c6c6f12b..897b37301851 100644
--- a/fs/afs/fsclient.c
+++ b/fs/afs/fsclient.c
@@ -302,7 +302,6 @@ static int afs_deliver_fs_fetch_data(struct afs_call *call)
 	struct afs_vnode_param *vp = &op->file[0];
 	struct afs_read *req = op->fetch.req;
 	const __be32 *bp;
-	unsigned int size;
 	int ret;
 
 	_enter("{%u,%zu,%zu/%llu}",
@@ -312,8 +311,6 @@ static int afs_deliver_fs_fetch_data(struct afs_call *call)
 	switch (call->unmarshall) {
 	case 0:
 		req->actual_len = 0;
-		req->index = 0;
-		req->offset = req->pos & (PAGE_SIZE - 1);
 		call->unmarshall++;
 		if (call->operation_ID == FSFETCHDATA64) {
 			afs_extract_to_tmp64(call);
@@ -323,7 +320,10 @@ static int afs_deliver_fs_fetch_data(struct afs_call *call)
 		}
 		fallthrough;
 
-		/* extract the returned data length */
+		/* Extract the returned data length into
+		 * ->actual_len.  This may indicate more or less data than was
+		 * requested will be returned.
+		 */
 	case 1:
 		_debug("extract data length");
 		ret = afs_extract_data(call, true);
@@ -332,45 +332,25 @@ static int afs_deliver_fs_fetch_data(struct afs_call *call)
 
 		req->actual_len = be64_to_cpu(call->tmp64);
 		_debug("DATA length: %llu", req->actual_len);
-		req->remain = min(req->len, req->actual_len);
-		if (req->remain == 0)
+
+		if (req->actual_len == 0)
 			goto no_more_data;
 
+		call->iter = req->iter;
+		call->iov_len = min(req->actual_len, req->len);
 		call->unmarshall++;
-
-	begin_page:
-		ASSERTCMP(req->index, <, req->nr_pages);
-		if (req->remain > PAGE_SIZE - req->offset)
-			size = PAGE_SIZE - req->offset;
-		else
-			size = req->remain;
-		call->iov_len = size;
-		call->bvec[0].bv_len = size;
-		call->bvec[0].bv_offset = req->offset;
-		call->bvec[0].bv_page = req->pages[req->index];
-		iov_iter_bvec(&call->def_iter, READ, call->bvec, 1, size);
-		ASSERTCMP(size, <=, PAGE_SIZE);
 		fallthrough;
 
 		/* extract the returned data */
 	case 2:
 		_debug("extract data %zu/%llu",
-		       iov_iter_count(call->iter), req->remain);
+		       iov_iter_count(call->iter), req->actual_len);
 
 		ret = afs_extract_data(call, true);
 		if (ret < 0)
 			return ret;
-		req->remain -= call->bvec[0].bv_len;
-		req->offset += call->bvec[0].bv_len;
-		ASSERTCMP(req->offset, <=, PAGE_SIZE);
-		if (req->offset == PAGE_SIZE) {
-			req->offset = 0;
-			req->index++;
-			if (req->remain > 0)
-				goto begin_page;
-		}
 
-		ASSERTCMP(req->remain, ==, 0);
+		call->iter = &call->def_iter;
 		if (req->actual_len <= req->len)
 			goto no_more_data;
 
@@ -412,16 +392,8 @@ static int afs_deliver_fs_fetch_data(struct afs_call *call)
 		break;
 	}
 
-	for (; req->index < req->nr_pages; req->index++) {
-		if (req->offset < PAGE_SIZE)
-			zero_user_segment(req->pages[req->index],
-					  req->offset, PAGE_SIZE);
-		req->offset = 0;
-	}
-
-	if (req->page_done)
-		for (req->index = 0; req->index < req->nr_pages; req->index++)
-			req->page_done(req);
+	if (req->done)
+		req->done(req);
 
 	_leave(" = 0 [done]");
 	return 0;
@@ -496,6 +468,8 @@ void afs_fs_fetch_data(struct afs_operation *op)
 	if (!call)
 		return afs_op_nomem(op);
 
+	req->call_debug_id = call->debug_id;
+
 	/* marshall the parameters */
 	bp = call->request;
 	bp[0] = htonl(FSFETCHDATA);
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 1badc7ed0487..6f1e6badf391 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -31,6 +31,7 @@
 
 struct pagevec;
 struct afs_call;
+struct afs_vnode;
 
 /*
  * Partial file-locking emulation mode.  (The problem being that AFS3 only
@@ -203,18 +204,18 @@ struct afs_read {
 	loff_t			pos;		/* Where to start reading */
 	loff_t			len;		/* How much we're asking for */
 	loff_t			actual_len;	/* How much we're actually getting */
-	loff_t			remain;		/* Amount remaining */
 	loff_t			file_size;	/* File size returned by server */
 	struct key		*key;		/* The key to use to reissue the read */
+	struct afs_vnode	*vnode;		/* The file being read into. */
 	afs_dataversion_t	data_version;	/* Version number returned by server */
 	refcount_t		usage;
-	unsigned int		index;		/* Which page we're reading into */
+	unsigned int		call_debug_id;
 	unsigned int		nr_pages;
-	unsigned int		offset;		/* offset into current page */
-	struct afs_vnode	*vnode;
-	void (*page_done)(struct afs_read *);
-	struct page		**pages;
-	struct page		*array[];
+	int			error;
+	void (*done)(struct afs_read *);
+	void (*cleanup)(struct afs_read *);
+	struct iov_iter		*iter;		/* Iterator representing the buffer */
+	struct iov_iter		def_iter;	/* Default iterator */
 };
 
 /*
@@ -1048,7 +1049,6 @@ extern void afs_put_wb_key(struct afs_wb_key *);
 extern int afs_open(struct inode *, struct file *);
 extern int afs_release(struct inode *, struct file *);
 extern int afs_fetch_data(struct afs_vnode *, struct afs_read *);
-extern int afs_page_filler(void *, struct page *);
 extern void afs_put_read(struct afs_read *);
 
 static inline struct afs_read *afs_get_read(struct afs_read *req)
diff --git a/fs/afs/write.c b/fs/afs/write.c
index 7eba0d3201ba..e78a9bc3b02d 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -22,6 +22,16 @@ int afs_set_page_dirty(struct page *page)
 	return __set_page_dirty_nobuffers(page);
 }
 
+/*
+ * Handle completion of a read operation to fill a page.
+ */
+static void afs_fill_hole(struct afs_read *req)
+{
+	if (iov_iter_count(req->iter) > 0)
+		/* The read was short - clear the excess buffer. */
+		iov_iter_zero(iov_iter_count(req->iter), req->iter);
+}
+
 /*
  * partly or wholly fill a page that's under preparation for writing
  */
@@ -45,18 +55,19 @@ static int afs_fill_page(struct file *file,
 		return 0;
 	}
 
-	req = kzalloc(struct_size(req, array, 1), GFP_KERNEL);
+	req = kzalloc(sizeof(struct afs_read), GFP_KERNEL);
 	if (!req)
 		return -ENOMEM;
 
 	refcount_set(&req->usage, 1);
-	req->key = key_get(afs_file_key(file));
-	req->pos = pos;
-	req->len = len;
-	req->nr_pages = 1;
-	req->pages = req->array;
-	req->pages[0] = page;
-	get_page(page);
+	req->vnode	= vnode;
+	req->done	= afs_fill_hole;
+	req->key	= key_get(afs_file_key(file));
+	req->pos	= pos;
+	req->len	= len;
+	req->nr_pages	= 1;
+	req->iter	= &req->def_iter;
+	iov_iter_xarray(&req->def_iter, READ, &file->f_mapping->i_pages, pos, len);
 
 	ret = afs_fetch_data(vnode, req);
 	afs_put_read(req);
diff --git a/fs/afs/yfsclient.c b/fs/afs/yfsclient.c
index 6c45d32da13c..abcec145db4b 100644
--- a/fs/afs/yfsclient.c
+++ b/fs/afs/yfsclient.c
@@ -360,7 +360,6 @@ static int yfs_deliver_fs_fetch_data64(struct afs_call *call)
 	struct afs_vnode_param *vp = &op->file[0];
 	struct afs_read *req = op->fetch.req;
 	const __be32 *bp;
-	unsigned int size;
 	int ret;
 
 	_enter("{%u,%zu, %zu/%llu}",
@@ -370,13 +369,14 @@ static int yfs_deliver_fs_fetch_data64(struct afs_call *call)
 	switch (call->unmarshall) {
 	case 0:
 		req->actual_len = 0;
-		req->index = 0;
-		req->offset = req->pos & (PAGE_SIZE - 1);
 		afs_extract_to_tmp64(call);
 		call->unmarshall++;
 		fallthrough;
 
-		/* extract the returned data length */
+		/* Extract the returned data length into ->actual_len.  This
+		 * may indicate more or less data than was requested will be
+		 * returned.
+		 */
 	case 1:
 		_debug("extract data length");
 		ret = afs_extract_data(call, true);
@@ -385,45 +385,25 @@ static int yfs_deliver_fs_fetch_data64(struct afs_call *call)
 
 		req->actual_len = be64_to_cpu(call->tmp64);
 		_debug("DATA length: %llu", req->actual_len);
-		req->remain = min(req->len, req->actual_len);
-		if (req->remain == 0)
+
+		if (req->actual_len == 0)
 			goto no_more_data;
 
+		call->iter = req->iter;
+		call->iov_len = min(req->actual_len, req->len);
 		call->unmarshall++;
-
-	begin_page:
-		ASSERTCMP(req->index, <, req->nr_pages);
-		if (req->remain > PAGE_SIZE - req->offset)
-			size = PAGE_SIZE - req->offset;
-		else
-			size = req->remain;
-		call->iov_len = size;
-		call->bvec[0].bv_len = size;
-		call->bvec[0].bv_offset = req->offset;
-		call->bvec[0].bv_page = req->pages[req->index];
-		iov_iter_bvec(&call->def_iter, READ, call->bvec, 1, size);
-		ASSERTCMP(size, <=, PAGE_SIZE);
 		fallthrough;
 
 		/* extract the returned data */
 	case 2:
 		_debug("extract data %zu/%llu",
-		       iov_iter_count(call->iter), req->remain);
+		       iov_iter_count(call->iter), req->actual_len);
 
 		ret = afs_extract_data(call, true);
 		if (ret < 0)
 			return ret;
-		req->remain -= call->bvec[0].bv_len;
-		req->offset += call->bvec[0].bv_len;
-		ASSERTCMP(req->offset, <=, PAGE_SIZE);
-		if (req->offset == PAGE_SIZE) {
-			req->offset = 0;
-			req->index++;
-			if (req->remain > 0)
-				goto begin_page;
-		}
 
-		ASSERTCMP(req->remain, ==, 0);
+		call->iter = &call->def_iter;
 		if (req->actual_len <= req->len)
 			goto no_more_data;
 
@@ -469,16 +449,8 @@ static int yfs_deliver_fs_fetch_data64(struct afs_call *call)
 		break;
 	}
 
-	for (; req->index < req->nr_pages; req->index++) {
-		if (req->offset < PAGE_SIZE)
-			zero_user_segment(req->pages[req->index],
-					  req->offset, PAGE_SIZE);
-		req->offset = 0;
-	}
-
-	if (req->page_done)
-		for (req->index = 0; req->index < req->nr_pages; req->index++)
-			req->page_done(req);
+	if (req->done)
+		req->done(req);
 
 	_leave(" = 0 [done]");
 	return 0;
@@ -518,6 +490,8 @@ void yfs_fs_fetch_data(struct afs_operation *op)
 	if (!call)
 		return afs_op_nomem(op);
 
+	req->call_debug_id = call->debug_id;
+
 	/* marshall the parameters */
 	bp = call->request;
 	bp = xdr_encode_u32(bp, YFSFETCHDATA64);

[PATCH 22/33] afs: Use ITER_XARRAY for writing

[David Howells]

Use a single ITER_XARRAY iterator to describe the portion of a file to be
transmitted to the server rather than generating a series of small
ITER_BVEC iterators on the fly.  This will make it easier to implement AIO
in afs.

In theory we could maybe use one giant ITER_BVEC, but that means
potentially allocating a huge array of bio_vec structs (max 256 per page)
when in fact the pagecache already has a structure listing all the relevant
pages (radix_tree/xarray) that can be walked over.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-afs@lists.infradead.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
---

 fs/afs/fsclient.c          |   50 +++++++++------------
 fs/afs/internal.h          |   15 +++---
 fs/afs/rxrpc.c             |  103 ++++++--------------------------------------
 fs/afs/write.c             |  100 ++++++++++++++++++++++++-------------------
 fs/afs/yfsclient.c         |   25 +++--------
 include/trace/events/afs.h |   51 ++++++++--------------
 6 files changed, 126 insertions(+), 218 deletions(-)

diff --git a/fs/afs/fsclient.c b/fs/afs/fsclient.c
index 897b37301851..31e6b3635541 100644
--- a/fs/afs/fsclient.c
+++ b/fs/afs/fsclient.c
@@ -1055,8 +1055,7 @@ static const struct afs_call_type afs_RXFSStoreData64 = {
 /*
  * store a set of pages to a very large file
  */
-static void afs_fs_store_data64(struct afs_operation *op,
-				loff_t pos, loff_t size, loff_t i_size)
+static void afs_fs_store_data64(struct afs_operation *op)
 {
 	struct afs_vnode_param *vp = &op->file[0];
 	struct afs_call *call;
@@ -1071,7 +1070,7 @@ static void afs_fs_store_data64(struct afs_operation *op,
 	if (!call)
 		return afs_op_nomem(op);
 
-	call->send_pages = true;
+	call->write_iter = op->store.write_iter;
 
 	/* marshall the parameters */
 	bp = call->request;
@@ -1087,47 +1086,38 @@ static void afs_fs_store_data64(struct afs_operation *op,
 	*bp++ = 0; /* unix mode */
 	*bp++ = 0; /* segment size */
 
-	*bp++ = htonl(upper_32_bits(pos));
-	*bp++ = htonl(lower_32_bits(pos));
-	*bp++ = htonl(upper_32_bits(size));
-	*bp++ = htonl(lower_32_bits(size));
-	*bp++ = htonl(upper_32_bits(i_size));
-	*bp++ = htonl(lower_32_bits(i_size));
+	*bp++ = htonl(upper_32_bits(op->store.pos));
+	*bp++ = htonl(lower_32_bits(op->store.pos));
+	*bp++ = htonl(upper_32_bits(op->store.size));
+	*bp++ = htonl(lower_32_bits(op->store.size));
+	*bp++ = htonl(upper_32_bits(op->store.i_size));
+	*bp++ = htonl(lower_32_bits(op->store.i_size));
 
 	trace_afs_make_fs_call(call, &vp->fid);
 	afs_make_op_call(op, call, GFP_NOFS);
 }
 
 /*
- * store a set of pages
+ * Write data to a file on the server.
  */
 void afs_fs_store_data(struct afs_operation *op)
 {
 	struct afs_vnode_param *vp = &op->file[0];
 	struct afs_call *call;
-	loff_t size, pos, i_size;
 	__be32 *bp;
 
 	_enter(",%x,{%llx:%llu},,",
 	       key_serial(op->key), vp->fid.vid, vp->fid.vnode);
 
-	size = (loff_t)op->store.last_to - (loff_t)op->store.first_offset;
-	if (op->store.first != op->store.last)
-		size += (loff_t)(op->store.last - op->store.first) << PAGE_SHIFT;
-	pos = (loff_t)op->store.first << PAGE_SHIFT;
-	pos += op->store.first_offset;
-
-	i_size = i_size_read(&vp->vnode->vfs_inode);
-	if (pos + size > i_size)
-		i_size = size + pos;
-
 	_debug("size %llx, at %llx, i_size %llx",
-	       (unsigned long long) size, (unsigned long long) pos,
-	       (unsigned long long) i_size);
+	       (unsigned long long)op->store.size,
+	       (unsigned long long)op->store.pos,
+	       (unsigned long long)op->store.i_size);
 
-	if (upper_32_bits(pos) || upper_32_bits(i_size) || upper_32_bits(size) ||
-	    upper_32_bits(pos + size))
-		return afs_fs_store_data64(op, pos, size, i_size);
+	if (upper_32_bits(op->store.pos) ||
+	    upper_32_bits(op->store.size) ||
+	    upper_32_bits(op->store.i_size))
+		return afs_fs_store_data64(op);
 
 	call = afs_alloc_flat_call(op->net, &afs_RXFSStoreData,
 				   (4 + 6 + 3) * 4,
@@ -1135,7 +1125,7 @@ void afs_fs_store_data(struct afs_operation *op)
 	if (!call)
 		return afs_op_nomem(op);
 
-	call->send_pages = true;
+	call->write_iter = op->store.write_iter;
 
 	/* marshall the parameters */
 	bp = call->request;
@@ -1151,9 +1141,9 @@ void afs_fs_store_data(struct afs_operation *op)
 	*bp++ = 0; /* unix mode */
 	*bp++ = 0; /* segment size */
 
-	*bp++ = htonl(lower_32_bits(pos));
-	*bp++ = htonl(lower_32_bits(size));
-	*bp++ = htonl(lower_32_bits(i_size));
+	*bp++ = htonl(lower_32_bits(op->store.pos));
+	*bp++ = htonl(lower_32_bits(op->store.size));
+	*bp++ = htonl(lower_32_bits(op->store.i_size));
 
 	trace_afs_make_fs_call(call, &vp->fid);
 	afs_make_op_call(op, call, GFP_NOFS);
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 6f1e6badf391..d4163f9babfd 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -107,6 +107,7 @@ struct afs_call {
 	void			*request;	/* request data (first part) */
 	size_t			iov_len;	/* Size of *iter to be used */
 	struct iov_iter		def_iter;	/* Default buffer/data iterator */
+	struct iov_iter		*write_iter;	/* Iterator defining write to be made */
 	struct iov_iter		*iter;		/* Iterator currently in use */
 	union {	/* Convenience for ->def_iter */
 		struct kvec	kvec[1];
@@ -133,7 +134,6 @@ struct afs_call {
 	unsigned char		unmarshall;	/* unmarshalling phase */
 	unsigned char		addr_ix;	/* Address in ->alist */
 	bool			drop_ref;	/* T if need to drop ref for incoming call */
-	bool			send_pages;	/* T if data from mapping should be sent */
 	bool			need_attention;	/* T if RxRPC poked us */
 	bool			async;		/* T if asynchronous */
 	bool			upgrade;	/* T to request service upgrade */
@@ -811,12 +811,13 @@ struct afs_operation {
 			afs_lock_type_t type;
 		} lock;
 		struct {
-			struct address_space *mapping;	/* Pages being written from */
-			pgoff_t		first;		/* first page in mapping to deal with */
-			pgoff_t		last;		/* last page in mapping to deal with */
-			unsigned	first_offset;	/* offset into mapping[first] */
-			unsigned	last_to;	/* amount of mapping[last] */
-			bool		laundering;	/* Laundering page, PG_writeback not set */
+			struct iov_iter	*write_iter;
+			loff_t	pos;
+			loff_t	size;
+			loff_t	i_size;
+			pgoff_t	first;		/* first page in mapping to deal with */
+			pgoff_t	last;		/* last page in mapping to deal with */
+			bool	laundering;	/* Laundering page, PG_writeback not set */
 		} store;
 		struct {
 			struct iattr	*attr;
diff --git a/fs/afs/rxrpc.c b/fs/afs/rxrpc.c
index ae68576f822f..23a1a92d64bb 100644
--- a/fs/afs/rxrpc.c
+++ b/fs/afs/rxrpc.c
@@ -271,40 +271,6 @@ void afs_flat_call_destructor(struct afs_call *call)
 	call->buffer = NULL;
 }
 
-#define AFS_BVEC_MAX 8
-
-/*
- * Load the given bvec with the next few pages.
- */
-static void afs_load_bvec(struct afs_call *call, struct msghdr *msg,
-			  struct bio_vec *bv, pgoff_t first, pgoff_t last,
-			  unsigned offset)
-{
-	struct afs_operation *op = call->op;
-	struct page *pages[AFS_BVEC_MAX];
-	unsigned int nr, n, i, to, bytes = 0;
-
-	nr = min_t(pgoff_t, last - first + 1, AFS_BVEC_MAX);
-	n = find_get_pages_contig(op->store.mapping, first, nr, pages);
-	ASSERTCMP(n, ==, nr);
-
-	msg->msg_flags |= MSG_MORE;
-	for (i = 0; i < nr; i++) {
-		to = PAGE_SIZE;
-		if (first + i >= last) {
-			to = op->store.last_to;
-			msg->msg_flags &= ~MSG_MORE;
-		}
-		bv[i].bv_page = pages[i];
-		bv[i].bv_len = to - offset;
-		bv[i].bv_offset = offset;
-		bytes += to - offset;
-		offset = 0;
-	}
-
-	iov_iter_bvec(&msg->msg_iter, WRITE, bv, nr, bytes);
-}
-
 /*
  * Advance the AFS call state when the RxRPC call ends the transmit phase.
  */
@@ -317,42 +283,6 @@ static void afs_notify_end_request_tx(struct sock *sock,
 	afs_set_call_state(call, AFS_CALL_CL_REQUESTING, AFS_CALL_CL_AWAIT_REPLY);
 }
 
-/*
- * attach the data from a bunch of pages on an inode to a call
- */
-static int afs_send_pages(struct afs_call *call, struct msghdr *msg)
-{
-	struct afs_operation *op = call->op;
-	struct bio_vec bv[AFS_BVEC_MAX];
-	unsigned int bytes, nr, loop, offset;
-	pgoff_t first = op->store.first, last = op->store.last;
-	int ret;
-
-	offset = op->store.first_offset;
-	op->store.first_offset = 0;
-
-	do {
-		afs_load_bvec(call, msg, bv, first, last, offset);
-		trace_afs_send_pages(call, msg, first, last, offset);
-
-		offset = 0;
-		bytes = msg->msg_iter.count;
-		nr = msg->msg_iter.nr_segs;
-
-		ret = rxrpc_kernel_send_data(op->net->socket, call->rxcall, msg,
-					     bytes, afs_notify_end_request_tx);
-		for (loop = 0; loop < nr; loop++)
-			put_page(bv[loop].bv_page);
-		if (ret < 0)
-			break;
-
-		first += nr;
-	} while (first <= last);
-
-	trace_afs_sent_pages(call, op->store.first, last, first, ret);
-	return ret;
-}
-
 /*
  * Initiate a call and synchronously queue up the parameters for dispatch.  Any
  * error is stored into the call struct, which the caller must check for.
@@ -384,21 +314,8 @@ void afs_make_call(struct afs_addr_cursor *ac, struct afs_call *call, gfp_t gfp)
 	 * after the initial fixed part.
 	 */
 	tx_total_len = call->request_size;
-	if (call->send_pages) {
-		struct afs_operation *op = call->op;
-
-		if (op->store.last == op->store.first) {
-			tx_total_len += op->store.last_to - op->store.first_offset;
-		} else {
-			/* It looks mathematically like you should be able to
-			 * combine the following lines with the ones above, but
-			 * unsigned arithmetic is fun when it wraps...
-			 */
-			tx_total_len += PAGE_SIZE - op->store.first_offset;
-			tx_total_len += op->store.last_to;
-			tx_total_len += (op->store.last - op->store.first - 1) * PAGE_SIZE;
-		}
-	}
+	if (call->write_iter)
+		tx_total_len += iov_iter_count(call->write_iter);
 
 	/* If the call is going to be asynchronous, we need an extra ref for
 	 * the call to hold itself so the caller need not hang on to its ref.
@@ -440,7 +357,7 @@ void afs_make_call(struct afs_addr_cursor *ac, struct afs_call *call, gfp_t gfp)
 	iov_iter_kvec(&msg.msg_iter, WRITE, iov, 1, call->request_size);
 	msg.msg_control		= NULL;
 	msg.msg_controllen	= 0;
-	msg.msg_flags		= MSG_WAITALL | (call->send_pages ? MSG_MORE : 0);
+	msg.msg_flags		= MSG_WAITALL | (call->write_iter ? MSG_MORE : 0);
 
 	ret = rxrpc_kernel_send_data(call->net->socket, rxcall,
 				     &msg, call->request_size,
@@ -448,8 +365,18 @@ void afs_make_call(struct afs_addr_cursor *ac, struct afs_call *call, gfp_t gfp)
 	if (ret < 0)
 		goto error_do_abort;
 
-	if (call->send_pages) {
-		ret = afs_send_pages(call, &msg);
+	if (call->write_iter) {
+		msg.msg_iter = *call->write_iter;
+		msg.msg_flags &= ~MSG_MORE;
+		trace_afs_send_data(call, &msg);
+
+		ret = rxrpc_kernel_send_data(call->net->socket,
+					     call->rxcall, &msg,
+					     iov_iter_count(&msg.msg_iter),
+					     afs_notify_end_request_tx);
+		*call->write_iter = msg.msg_iter;
+
+		trace_afs_sent_data(call, &msg, ret);
 		if (ret < 0)
 			goto error_do_abort;
 	}
diff --git a/fs/afs/write.c b/fs/afs/write.c
index e78a9bc3b02d..dd4dc1c868b5 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -325,36 +325,27 @@ static void afs_redirty_pages(struct writeback_control *wbc,
 /*
  * completion of write to server
  */
-static void afs_pages_written_back(struct afs_vnode *vnode,
-				   pgoff_t first, pgoff_t last)
+static void afs_pages_written_back(struct afs_vnode *vnode, pgoff_t start, pgoff_t last)
 {
-	struct pagevec pv;
-	unsigned count, loop;
+	struct address_space *mapping = vnode->vfs_inode.i_mapping;
+	struct page *page;
+
+	XA_STATE(xas, &mapping->i_pages, start);
 
 	_enter("{%llx:%llu},{%lx-%lx}",
-	       vnode->fid.vid, vnode->fid.vnode, first, last);
+	       vnode->fid.vid, vnode->fid.vnode, start, last);
 
-	pagevec_init(&pv);
+	rcu_read_lock();
 
-	do {
-		_debug("done %lx-%lx", first, last);
+	xas_for_each(&xas, page, last) {
+		ASSERT(PageWriteback(page));
 
-		count = last - first + 1;
-		if (count > PAGEVEC_SIZE)
-			count = PAGEVEC_SIZE;
-		pv.nr = find_get_pages_contig(vnode->vfs_inode.i_mapping,
-					      first, count, pv.pages);
-		ASSERTCMP(pv.nr, ==, count);
+		detach_page_private(page);
+		trace_afs_page_dirty(vnode, tracepoint_string("clear"), page);
+		page_endio(page, true, 0);
+	}
 
-		for (loop = 0; loop < count; loop++) {
-			detach_page_private(pv.pages[loop]);
-			trace_afs_page_dirty(vnode, tracepoint_string("clear"),
-					     pv.pages[loop]);
-			end_page_writeback(pv.pages[loop]);
-		}
-		first += count;
-		__pagevec_release(&pv);
-	} while (first <= last);
+	rcu_read_unlock();
 
 	afs_prune_wb_keys(vnode);
 	_leave("");
@@ -411,9 +402,7 @@ static void afs_store_data_success(struct afs_operation *op)
 		if (!op->store.laundering)
 			afs_pages_written_back(vnode, op->store.first, op->store.last);
 		afs_stat_v(vnode, n_stores);
-		atomic_long_add((op->store.last * PAGE_SIZE + op->store.last_to) -
-				(op->store.first * PAGE_SIZE + op->store.first_offset),
-				&afs_v2net(vnode)->n_store_bytes);
+		atomic_long_add(op->store.size, &afs_v2net(vnode)->n_store_bytes);
 	}
 }
 
@@ -426,21 +415,21 @@ static const struct afs_operation_ops afs_store_data_operation = {
 /*
  * write to a file
  */
-static int afs_store_data(struct address_space *mapping,
-			  pgoff_t first, pgoff_t last,
-			  unsigned offset, unsigned to, bool laundering)
+static int afs_store_data(struct afs_vnode *vnode, struct iov_iter *iter,
+			  loff_t pos, pgoff_t first, pgoff_t last,
+			  bool laundering)
 {
-	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 	struct afs_operation *op;
 	struct afs_wb_key *wbk = NULL;
-	int ret;
+	loff_t size = iov_iter_count(iter), i_size;
+	int ret = -ENOKEY;
 
-	_enter("%s{%llx:%llu.%u},%lx,%lx,%x,%x",
+	_enter("%s{%llx:%llu.%u},%llx,%llx",
 	       vnode->volume->name,
 	       vnode->fid.vid,
 	       vnode->fid.vnode,
 	       vnode->fid.unique,
-	       first, last, offset, to);
+	       size, pos);
 
 	ret = afs_get_writeback_key(vnode, &wbk);
 	if (ret) {
@@ -454,13 +443,16 @@ static int afs_store_data(struct address_space *mapping,
 		return -ENOMEM;
 	}
 
+	i_size = i_size_read(&vnode->vfs_inode);
+
 	afs_op_set_vnode(op, 0, vnode);
 	op->file[0].dv_delta = 1;
-	op->store.mapping = mapping;
+	op->store.write_iter = iter;
+	op->store.pos = pos;
 	op->store.first = first;
 	op->store.last = last;
-	op->store.first_offset = offset;
-	op->store.last_to = to;
+	op->store.size = size;
+	op->store.i_size = max(pos + size, i_size);
 	op->store.laundering = laundering;
 	op->mtime = vnode->vfs_inode.i_mtime;
 	op->flags |= AFS_OPERATION_UNINTR;
@@ -503,11 +495,12 @@ static int afs_write_back_from_locked_page(struct address_space *mapping,
 					   pgoff_t final_page)
 {
 	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
+	struct iov_iter iter;
 	struct page *pages[8], *page;
 	unsigned long count, priv;
 	unsigned n, offset, to, f, t;
 	pgoff_t start, first, last;
-	loff_t i_size, end;
+	loff_t i_size, pos, end;
 	int loop, ret;
 
 	_enter(",%lx", primary_page->index);
@@ -604,15 +597,28 @@ static int afs_write_back_from_locked_page(struct address_space *mapping,
 
 	first = primary_page->index;
 	last = first + count - 1;
+	_debug("write back %lx[%u..] to %lx[..%u]", first, offset, last, to);
 
-	end = (loff_t)last * PAGE_SIZE + to;
-	i_size = i_size_read(&vnode->vfs_inode);
+	pos = first;
+	pos <<= PAGE_SHIFT;
+	pos += offset;
+	end = last;
+	end <<= PAGE_SHIFT;
+	end += to;
 
-	_debug("write back %lx[%u..] to %lx[..%u]", first, offset, last, to);
+	/* Trim the actual write down to the EOF */
+	i_size = i_size_read(&vnode->vfs_inode);
 	if (end > i_size)
-		to = i_size & ~PAGE_MASK;
+		end = i_size;
+
+	if (pos < i_size) {
+		iov_iter_xarray(&iter, WRITE, &mapping->i_pages, pos, end - pos);
+		ret = afs_store_data(vnode, &iter, pos, first, last, false);
+	} else {
+		/* The dirty region was entirely beyond the EOF. */
+		ret = 0;
+	}
 
-	ret = afs_store_data(mapping, first, last, offset, to, false);
 	switch (ret) {
 	case 0:
 		ret = count;
@@ -913,6 +919,8 @@ int afs_launder_page(struct page *page)
 {
 	struct address_space *mapping = page->mapping;
 	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
+	struct iov_iter iter;
+	struct bio_vec bv[1];
 	unsigned long priv;
 	unsigned int f, t;
 	int ret = 0;
@@ -928,8 +936,14 @@ int afs_launder_page(struct page *page)
 			t = afs_page_dirty_to(page, priv);
 		}
 
+		bv[0].bv_page = page;
+		bv[0].bv_offset = f;
+		bv[0].bv_len = t - f;
+		iov_iter_bvec(&iter, WRITE, bv, 1, bv[0].bv_len);
+
 		trace_afs_page_dirty(vnode, tracepoint_string("launder"), page);
-		ret = afs_store_data(mapping, page->index, page->index, t, f, true);
+		ret = afs_store_data(vnode, &iter, (loff_t)page->index << PAGE_SHIFT,
+				     page->index, page->index, true);
 	}
 
 	detach_page_private(page);
diff --git a/fs/afs/yfsclient.c b/fs/afs/yfsclient.c
index abcec145db4b..363d6dd276c0 100644
--- a/fs/afs/yfsclient.c
+++ b/fs/afs/yfsclient.c
@@ -1078,25 +1078,15 @@ void yfs_fs_store_data(struct afs_operation *op)
 {
 	struct afs_vnode_param *vp = &op->file[0];
 	struct afs_call *call;
-	loff_t size, pos, i_size;
 	__be32 *bp;
 
 	_enter(",%x,{%llx:%llu},,",
 	       key_serial(op->key), vp->fid.vid, vp->fid.vnode);
 
-	size = (loff_t)op->store.last_to - (loff_t)op->store.first_offset;
-	if (op->store.first != op->store.last)
-		size += (loff_t)(op->store.last - op->store.first) << PAGE_SHIFT;
-	pos = (loff_t)op->store.first << PAGE_SHIFT;
-	pos += op->store.first_offset;
-
-	i_size = i_size_read(&vp->vnode->vfs_inode);
-	if (pos + size > i_size)
-		i_size = size + pos;
-
 	_debug("size %llx, at %llx, i_size %llx",
-	       (unsigned long long)size, (unsigned long long)pos,
-	       (unsigned long long)i_size);
+	       (unsigned long long)op->store.size,
+	       (unsigned long long)op->store.pos,
+	       (unsigned long long)op->store.i_size);
 
 	call = afs_alloc_flat_call(op->net, &yfs_RXYFSStoreData64,
 				   sizeof(__be32) +
@@ -1109,8 +1099,7 @@ void yfs_fs_store_data(struct afs_operation *op)
 	if (!call)
 		return afs_op_nomem(op);
 
-	call->key = op->key;
-	call->send_pages = true;
+	call->write_iter = op->store.write_iter;
 
 	/* marshall the parameters */
 	bp = call->request;
@@ -1118,9 +1107,9 @@ void yfs_fs_store_data(struct afs_operation *op)
 	bp = xdr_encode_u32(bp, 0); /* RPC flags */
 	bp = xdr_encode_YFSFid(bp, &vp->fid);
 	bp = xdr_encode_YFSStoreStatus_mtime(bp, &op->mtime);
-	bp = xdr_encode_u64(bp, pos);
-	bp = xdr_encode_u64(bp, size);
-	bp = xdr_encode_u64(bp, i_size);
+	bp = xdr_encode_u64(bp, op->store.pos);
+	bp = xdr_encode_u64(bp, op->store.size);
+	bp = xdr_encode_u64(bp, op->store.i_size);
 	yfs_check_req(call, bp);
 
 	trace_afs_make_fs_call(call, &vp->fid);
diff --git a/include/trace/events/afs.h b/include/trace/events/afs.h
index 9203cf6a8c53..3ccf591b2374 100644
--- a/include/trace/events/afs.h
+++ b/include/trace/events/afs.h
@@ -886,65 +886,52 @@ TRACE_EVENT(afs_call_done,
 		      __entry->rx_call)
 	    );
 
-TRACE_EVENT(afs_send_pages,
-	    TP_PROTO(struct afs_call *call, struct msghdr *msg,
-		     pgoff_t first, pgoff_t last, unsigned int offset),
+TRACE_EVENT(afs_send_data,
+	    TP_PROTO(struct afs_call *call, struct msghdr *msg),
 
-	    TP_ARGS(call, msg, first, last, offset),
+	    TP_ARGS(call, msg),
 
 	    TP_STRUCT__entry(
 		    __field(unsigned int,		call		)
-		    __field(pgoff_t,			first		)
-		    __field(pgoff_t,			last		)
-		    __field(unsigned int,		nr		)
-		    __field(unsigned int,		bytes		)
-		    __field(unsigned int,		offset		)
 		    __field(unsigned int,		flags		)
+		    __field(loff_t,			offset		)
+		    __field(loff_t,			count		)
 			     ),
 
 	    TP_fast_assign(
 		    __entry->call = call->debug_id;
-		    __entry->first = first;
-		    __entry->last = last;
-		    __entry->nr = msg->msg_iter.nr_segs;
-		    __entry->bytes = msg->msg_iter.count;
-		    __entry->offset = offset;
 		    __entry->flags = msg->msg_flags;
+		    __entry->offset = msg->msg_iter.xarray_start + msg->msg_iter.iov_offset;
+		    __entry->count = iov_iter_count(&msg->msg_iter);
 			   ),
 
-	    TP_printk(" c=%08x %lx-%lx-%lx b=%x o=%x f=%x",
-		      __entry->call,
-		      __entry->first, __entry->first + __entry->nr - 1, __entry->last,
-		      __entry->bytes, __entry->offset,
+	    TP_printk(" c=%08x o=%llx n=%llx f=%x",
+		      __entry->call, __entry->offset, __entry->count,
 		      __entry->flags)
 	    );
 
-TRACE_EVENT(afs_sent_pages,
-	    TP_PROTO(struct afs_call *call, pgoff_t first, pgoff_t last,
-		     pgoff_t cursor, int ret),
+TRACE_EVENT(afs_sent_data,
+	    TP_PROTO(struct afs_call *call, struct msghdr *msg, int ret),
 
-	    TP_ARGS(call, first, last, cursor, ret),
+	    TP_ARGS(call, msg, ret),
 
 	    TP_STRUCT__entry(
 		    __field(unsigned int,		call		)
-		    __field(pgoff_t,			first		)
-		    __field(pgoff_t,			last		)
-		    __field(pgoff_t,			cursor		)
 		    __field(int,			ret		)
+		    __field(loff_t,			offset		)
+		    __field(loff_t,			count		)
 			     ),
 
 	    TP_fast_assign(
 		    __entry->call = call->debug_id;
-		    __entry->first = first;
-		    __entry->last = last;
-		    __entry->cursor = cursor;
 		    __entry->ret = ret;
+		    __entry->offset = msg->msg_iter.xarray_start + msg->msg_iter.iov_offset;
+		    __entry->count = iov_iter_count(&msg->msg_iter);
 			   ),
 
-	    TP_printk(" c=%08x %lx-%lx c=%lx r=%d",
-		      __entry->call,
-		      __entry->first, __entry->last,
-		      __entry->cursor, __entry->ret)
+	    TP_printk(" c=%08x o=%llx n=%llx r=%x",
+		      __entry->call, __entry->offset, __entry->count,
+		      __entry->ret)
 	    );
 
 TRACE_EVENT(afs_dir_check_failed,

[PATCH 23/33] afs: Wait on PG_fscache before modifying/releasing a page

[David Howells]

PG_fscache is going to be used to indicate that a page is being written to
the cache, and that the page should not be modified or released until it's
finished.

Make afs_invalidatepage() and afs_releasepage() wait for it.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-afs@lists.infradead.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
---

 fs/afs/file.c  |    9 +++++++++
 fs/afs/write.c |   10 ++++++++++
 2 files changed, 19 insertions(+)

diff --git a/fs/afs/file.c b/fs/afs/file.c
index f1bab69e99d4..acbc21a8c80e 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -594,6 +594,7 @@ static void afs_invalidatepage(struct page *page, unsigned int offset,
 	if (PagePrivate(page))
 		afs_invalidate_dirty(page, offset, length);
 
+	wait_on_page_fscache(page);
 	_leave("");
 }
 
@@ -611,6 +612,14 @@ static int afs_releasepage(struct page *page, gfp_t gfp_flags)
 
 	/* deny if page is being written to the cache and the caller hasn't
 	 * elected to wait */
+#ifdef CONFIG_AFS_FSCACHE
+	if (PageFsCache(page)) {
+		if (!(gfp_flags & __GFP_DIRECT_RECLAIM) || !(gfp_flags & __GFP_FS))
+			return false;
+		wait_on_page_fscache(page);
+	}
+#endif
+
 	if (PagePrivate(page)) {
 		detach_page_private(page);
 		trace_afs_page_dirty(vnode, tracepoint_string("rel"), page);
diff --git a/fs/afs/write.c b/fs/afs/write.c
index dd4dc1c868b5..e1791de90478 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -117,6 +117,10 @@ int afs_write_begin(struct file *file, struct address_space *mapping,
 		SetPageUptodate(page);
 	}
 
+#ifdef CONFIG_AFS_FSCACHE
+	wait_on_page_fscache(page);
+#endif
+
 try_again:
 	/* See if this page is already partially written in a way that we can
 	 * merge the new write with.
@@ -857,6 +861,11 @@ vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
 	/* Wait for the page to be written to the cache before we allow it to
 	 * be modified.  We then assume the entire page will need writing back.
 	 */
+#ifdef CONFIG_AFS_FSCACHE
+	if (PageFsCache(vmf->page) &&
+	    wait_on_page_bit_killable(vmf->page, PG_fscache) < 0)
+		return VM_FAULT_RETRY;
+#endif
 
 	if (PageWriteback(vmf->page) &&
 	    wait_on_page_bit_killable(vmf->page, PG_writeback) < 0)
@@ -948,5 +957,6 @@ int afs_launder_page(struct page *page)
 
 	detach_page_private(page);
 	trace_afs_page_dirty(vnode, tracepoint_string("laundered"), page);
+	wait_on_page_fscache(page);
 	return ret;
 }

[PATCH 24/33] afs: Extract writeback extension into its own function

[David Howells]

Extract writeback extension into its own function to break up the writeback
function a bit.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-afs@lists.infradead.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
---

 fs/afs/write.c |  109 ++++++++++++++++++++++++++++++++++----------------------
 1 file changed, 67 insertions(+), 42 deletions(-)

diff --git a/fs/afs/write.c b/fs/afs/write.c
index e1791de90478..89c804bfe253 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -490,47 +490,25 @@ static int afs_store_data(struct afs_vnode *vnode, struct iov_iter *iter,
 }
 
 /*
- * Synchronously write back the locked page and any subsequent non-locked dirty
- * pages.
+ * Extend the region to be written back to include subsequent contiguously
+ * dirty pages if possible, but don't sleep while doing so.
+ *
+ * If this page holds new content, then we can include filler zeros in the
+ * writeback.
  */
-static int afs_write_back_from_locked_page(struct address_space *mapping,
-					   struct writeback_control *wbc,
-					   struct page *primary_page,
-					   pgoff_t final_page)
+static void afs_extend_writeback(struct address_space *mapping,
+				 struct afs_vnode *vnode,
+				 long *_count,
+				 pgoff_t start,
+				 pgoff_t final_page,
+				 unsigned *_offset,
+				 unsigned *_to,
+				 bool new_content)
 {
-	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
-	struct iov_iter iter;
 	struct page *pages[8], *page;
-	unsigned long count, priv;
-	unsigned n, offset, to, f, t;
-	pgoff_t start, first, last;
-	loff_t i_size, pos, end;
-	int loop, ret;
-
-	_enter(",%lx", primary_page->index);
-
-	count = 1;
-	if (test_set_page_writeback(primary_page))
-		BUG();
-
-	/* Find all consecutive lockable dirty pages that have contiguous
-	 * written regions, stopping when we find a page that is not
-	 * immediately lockable, is not dirty or is missing, or we reach the
-	 * end of the range.
-	 */
-	start = primary_page->index;
-	priv = page_private(primary_page);
-	offset = afs_page_dirty_from(primary_page, priv);
-	to = afs_page_dirty_to(primary_page, priv);
-	trace_afs_page_dirty(vnode, tracepoint_string("store"), primary_page);
-
-	WARN_ON(offset == to);
-	if (offset == to)
-		trace_afs_page_dirty(vnode, tracepoint_string("WARN"), primary_page);
-
-	if (start >= final_page ||
-	    (to < PAGE_SIZE && !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags)))
-		goto no_more;
+	unsigned long count = *_count, priv;
+	unsigned offset = *_offset, to = *_to, n, f, t;
+	int loop;
 
 	start++;
 	do {
@@ -551,8 +529,7 @@ static int afs_write_back_from_locked_page(struct address_space *mapping,
 
 		for (loop = 0; loop < n; loop++) {
 			page = pages[loop];
-			if (to != PAGE_SIZE &&
-			    !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags))
+			if (to != PAGE_SIZE && !new_content)
 				break;
 			if (page->index > final_page)
 				break;
@@ -566,8 +543,7 @@ static int afs_write_back_from_locked_page(struct address_space *mapping,
 			priv = page_private(page);
 			f = afs_page_dirty_from(page, priv);
 			t = afs_page_dirty_to(page, priv);
-			if (f != 0 &&
-			    !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags)) {
+			if (f != 0 && !new_content) {
 				unlock_page(page);
 				break;
 			}
@@ -593,6 +569,55 @@ static int afs_write_back_from_locked_page(struct address_space *mapping,
 	} while (start <= final_page && count < 65536);
 
 no_more:
+	*_count = count;
+	*_offset = offset;
+	*_to = to;
+}
+
+/*
+ * Synchronously write back the locked page and any subsequent non-locked dirty
+ * pages.
+ */
+static int afs_write_back_from_locked_page(struct address_space *mapping,
+					   struct writeback_control *wbc,
+					   struct page *primary_page,
+					   pgoff_t final_page)
+{
+	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
+	struct iov_iter iter;
+	unsigned long count, priv;
+	unsigned offset, to;
+	pgoff_t start, first, last;
+	loff_t i_size, pos, end;
+	bool new_content = test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags);
+	int ret;
+
+	_enter(",%lx", primary_page->index);
+
+	count = 1;
+	if (test_set_page_writeback(primary_page))
+		BUG();
+
+	/* Find all consecutive lockable dirty pages that have contiguous
+	 * written regions, stopping when we find a page that is not
+	 * immediately lockable, is not dirty or is missing, or we reach the
+	 * end of the range.
+	 */
+	start = primary_page->index;
+	priv = page_private(primary_page);
+	offset = afs_page_dirty_from(primary_page, priv);
+	to = afs_page_dirty_to(primary_page, priv);
+	trace_afs_page_dirty(vnode, tracepoint_string("store"), primary_page);
+
+	WARN_ON(offset == to);
+	if (offset == to)
+		trace_afs_page_dirty(vnode, tracepoint_string("WARN"), primary_page);
+
+	if (start < final_page &&
+	    (to == PAGE_SIZE || new_content))
+		afs_extend_writeback(mapping, vnode, &count, start, final_page,
+				     &offset, &to, new_content);
+
 	/* We now have a contiguous set of dirty pages, each with writeback
 	 * set; the first page is still locked at this point, but all the rest
 	 * have been unlocked.

[PATCH 25/33] afs: Prepare for use of THPs

[David Howells]

As a prelude to supporting transparent huge pages, use thp_size() and
similar rather than PAGE_SIZE/SHIFT.

Further, try and frame everything in terms of file positions and lengths
rather than page indices and numbers of pages.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-afs@lists.infradead.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
---

 fs/afs/dir.c      |    2 
 fs/afs/file.c     |    8 -
 fs/afs/internal.h |    2 
 fs/afs/write.c    |  436 +++++++++++++++++++++++++++++------------------------
 4 files changed, 245 insertions(+), 203 deletions(-)

diff --git a/fs/afs/dir.c b/fs/afs/dir.c
index 526a49889dff..d547891af63d 100644
--- a/fs/afs/dir.c
+++ b/fs/afs/dir.c
@@ -2082,6 +2082,6 @@ static void afs_dir_invalidatepage(struct page *page, unsigned int offset,
 		afs_stat_v(dvnode, n_inval);
 
 	/* we clean up only if the entire page is being invalidated */
-	if (offset == 0 && length == PAGE_SIZE)
+	if (offset == 0 && length == thp_size(page))
 		detach_page_private(page);
 }
diff --git a/fs/afs/file.c b/fs/afs/file.c
index acbc21a8c80e..f6282ac0d222 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -330,8 +330,8 @@ static int afs_page_filler(struct key *key, struct page *page)
 	req->vnode		= vnode;
 	req->key		= key_get(key);
 	req->pos		= (loff_t)page->index << PAGE_SHIFT;
-	req->len		= PAGE_SIZE;
-	req->nr_pages		= 1;
+	req->len		= thp_size(page);
+	req->nr_pages		= thp_nr_pages(page);
 	req->done		= afs_file_read_done;
 	req->cleanup		= afs_file_read_cleanup;
 
@@ -575,8 +575,8 @@ static void afs_invalidate_dirty(struct page *page, unsigned int offset,
 	trace_afs_page_dirty(vnode, tracepoint_string("undirty"), page);
 	clear_page_dirty_for_io(page);
 full_invalidate:
-	detach_page_private(page);
 	trace_afs_page_dirty(vnode, tracepoint_string("inval"), page);
+	detach_page_private(page);
 }
 
 /*
@@ -621,8 +621,8 @@ static int afs_releasepage(struct page *page, gfp_t gfp_flags)
 #endif
 
 	if (PagePrivate(page)) {
-		detach_page_private(page);
 		trace_afs_page_dirty(vnode, tracepoint_string("rel"), page);
+		detach_page_private(page);
 	}
 
 	/* indicate that the page can be released */
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index d4163f9babfd..daf5339ae316 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -815,8 +815,6 @@ struct afs_operation {
 			loff_t	pos;
 			loff_t	size;
 			loff_t	i_size;
-			pgoff_t	first;		/* first page in mapping to deal with */
-			pgoff_t	last;		/* last page in mapping to deal with */
 			bool	laundering;	/* Laundering page, PG_writeback not set */
 		} store;
 		struct {
diff --git a/fs/afs/write.c b/fs/afs/write.c
index 89c804bfe253..e672833c99bc 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -94,15 +94,15 @@ int afs_write_begin(struct file *file, struct address_space *mapping,
 	struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
 	struct page *page;
 	unsigned long priv;
-	unsigned f, from = pos & (PAGE_SIZE - 1);
-	unsigned t, to = from + len;
-	pgoff_t index = pos >> PAGE_SHIFT;
+	unsigned f, from;
+	unsigned t, to;
+	pgoff_t index;
 	int ret;
 
-	_enter("{%llx:%llu},{%lx},%u,%u",
-	       vnode->fid.vid, vnode->fid.vnode, index, from, to);
+	_enter("{%llx:%llu},%llx,%x",
+	       vnode->fid.vid, vnode->fid.vnode, pos, len);
 
-	page = grab_cache_page_write_begin(mapping, index, flags);
+	page = grab_cache_page_write_begin(mapping, pos / PAGE_SIZE, flags);
 	if (!page)
 		return -ENOMEM;
 
@@ -121,19 +121,20 @@ int afs_write_begin(struct file *file, struct address_space *mapping,
 	wait_on_page_fscache(page);
 #endif
 
+	index = page->index;
+	from = pos - index * PAGE_SIZE;
+	to = from + len;
+
 try_again:
 	/* See if this page is already partially written in a way that we can
 	 * merge the new write with.
 	 */
-	t = f = 0;
 	if (PagePrivate(page)) {
 		priv = page_private(page);
 		f = afs_page_dirty_from(page, priv);
 		t = afs_page_dirty_to(page, priv);
 		ASSERTCMP(f, <=, t);
-	}
 
-	if (f != t) {
 		if (PageWriteback(page)) {
 			trace_afs_page_dirty(vnode, tracepoint_string("alrdy"), page);
 			goto flush_conflicting_write;
@@ -180,7 +181,7 @@ int afs_write_end(struct file *file, struct address_space *mapping,
 {
 	struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
 	unsigned long priv;
-	unsigned int f, from = pos & (PAGE_SIZE - 1);
+	unsigned int f, from = pos & (thp_size(page) - 1);
 	unsigned int t, to = from + copied;
 	loff_t i_size, maybe_i_size;
 	int ret = 0;
@@ -233,9 +234,8 @@ int afs_write_end(struct file *file, struct address_space *mapping,
 		trace_afs_page_dirty(vnode, tracepoint_string("dirty"), page);
 	}
 
-	set_page_dirty(page);
-	if (PageDirty(page))
-		_debug("dirtied");
+	if (set_page_dirty(page))
+		_debug("dirtied %lx", page->index);
 	ret = copied;
 
 out:
@@ -248,40 +248,43 @@ int afs_write_end(struct file *file, struct address_space *mapping,
  * kill all the pages in the given range
  */
 static void afs_kill_pages(struct address_space *mapping,
-			   pgoff_t first, pgoff_t last)
+			   loff_t start, loff_t len)
 {
 	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 	struct pagevec pv;
-	unsigned count, loop;
+	unsigned int loop, psize;
 
-	_enter("{%llx:%llu},%lx-%lx",
-	       vnode->fid.vid, vnode->fid.vnode, first, last);
+	_enter("{%llx:%llu},%llx @%llx",
+	       vnode->fid.vid, vnode->fid.vnode, len, start);
 
 	pagevec_init(&pv);
 
 	do {
-		_debug("kill %lx-%lx", first, last);
+		_debug("kill %llx @%llx", len, start);
 
-		count = last - first + 1;
-		if (count > PAGEVEC_SIZE)
-			count = PAGEVEC_SIZE;
-		pv.nr = find_get_pages_contig(mapping, first, count, pv.pages);
-		ASSERTCMP(pv.nr, ==, count);
+		pv.nr = find_get_pages_contig(mapping, start / PAGE_SIZE,
+					      PAGEVEC_SIZE, pv.pages);
+		if (pv.nr == 0)
+			break;
 
-		for (loop = 0; loop < count; loop++) {
+		for (loop = 0; loop < pv.nr; loop++) {
 			struct page *page = pv.pages[loop];
+
+			if (page->index * PAGE_SIZE >= start + len)
+				break;
+
+			psize = thp_size(page);
+			start += psize;
+			len -= psize;
 			ClearPageUptodate(page);
-			SetPageError(page);
 			end_page_writeback(page);
-			if (page->index >= first)
-				first = page->index + 1;
 			lock_page(page);
 			generic_error_remove_page(mapping, page);
 			unlock_page(page);
 		}
 
 		__pagevec_release(&pv);
-	} while (first <= last);
+	} while (len > 0);
 
 	_leave("");
 }
@@ -291,37 +294,40 @@ static void afs_kill_pages(struct address_space *mapping,
  */
 static void afs_redirty_pages(struct writeback_control *wbc,
 			      struct address_space *mapping,
-			      pgoff_t first, pgoff_t last)
+			      loff_t start, loff_t len)
 {
 	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 	struct pagevec pv;
-	unsigned count, loop;
+	unsigned int loop, psize;
 
-	_enter("{%llx:%llu},%lx-%lx",
-	       vnode->fid.vid, vnode->fid.vnode, first, last);
+	_enter("{%llx:%llu},%llx @%llx",
+	       vnode->fid.vid, vnode->fid.vnode, len, start);
 
 	pagevec_init(&pv);
 
 	do {
-		_debug("redirty %lx-%lx", first, last);
+		_debug("redirty %llx @%llx", len, start);
 
-		count = last - first + 1;
-		if (count > PAGEVEC_SIZE)
-			count = PAGEVEC_SIZE;
-		pv.nr = find_get_pages_contig(mapping, first, count, pv.pages);
-		ASSERTCMP(pv.nr, ==, count);
+		pv.nr = find_get_pages_contig(mapping, start / PAGE_SIZE,
+					      PAGEVEC_SIZE, pv.pages);
+		if (pv.nr == 0)
+			break;
 
-		for (loop = 0; loop < count; loop++) {
+		for (loop = 0; loop < pv.nr; loop++) {
 			struct page *page = pv.pages[loop];
 
+			if (page->index * PAGE_SIZE >= start + len)
+				break;
+
+			psize = thp_size(page);
+			start += psize;
+			len -= psize;
 			redirty_page_for_writepage(wbc, page);
 			end_page_writeback(page);
-			if (page->index >= first)
-				first = page->index + 1;
 		}
 
 		__pagevec_release(&pv);
-	} while (first <= last);
+	} while (len > 0);
 
 	_leave("");
 }
@@ -329,23 +335,28 @@ static void afs_redirty_pages(struct writeback_control *wbc,
 /*
  * completion of write to server
  */
-static void afs_pages_written_back(struct afs_vnode *vnode, pgoff_t start, pgoff_t last)
+static void afs_pages_written_back(struct afs_vnode *vnode, loff_t start, unsigned int len)
 {
 	struct address_space *mapping = vnode->vfs_inode.i_mapping;
 	struct page *page;
+	pgoff_t end;
 
-	XA_STATE(xas, &mapping->i_pages, start);
+	XA_STATE(xas, &mapping->i_pages, start / PAGE_SIZE);
 
-	_enter("{%llx:%llu},{%lx-%lx}",
-	       vnode->fid.vid, vnode->fid.vnode, start, last);
+	_enter("{%llx:%llu},{%x @%llx}",
+	       vnode->fid.vid, vnode->fid.vnode, len, start);
 
 	rcu_read_lock();
 
-	xas_for_each(&xas, page, last) {
-		ASSERT(PageWriteback(page));
+	end = (start + len - 1) / PAGE_SIZE;
+	xas_for_each(&xas, page, end) {
+		if (!PageWriteback(page)) {
+			kdebug("bad %x @%llx page %lx %lx", len, start, page->index, end);
+			ASSERT(PageWriteback(page));
+		}
 
-		detach_page_private(page);
 		trace_afs_page_dirty(vnode, tracepoint_string("clear"), page);
+		detach_page_private(page);
 		page_endio(page, true, 0);
 	}
 
@@ -404,7 +415,7 @@ static void afs_store_data_success(struct afs_operation *op)
 	afs_vnode_commit_status(op, &op->file[0]);
 	if (op->error == 0) {
 		if (!op->store.laundering)
-			afs_pages_written_back(vnode, op->store.first, op->store.last);
+			afs_pages_written_back(vnode, op->store.pos, op->store.size);
 		afs_stat_v(vnode, n_stores);
 		atomic_long_add(op->store.size, &afs_v2net(vnode)->n_store_bytes);
 	}
@@ -419,8 +430,7 @@ static const struct afs_operation_ops afs_store_data_operation = {
 /*
  * write to a file
  */
-static int afs_store_data(struct afs_vnode *vnode, struct iov_iter *iter,
-			  loff_t pos, pgoff_t first, pgoff_t last,
+static int afs_store_data(struct afs_vnode *vnode, struct iov_iter *iter, loff_t pos,
 			  bool laundering)
 {
 	struct afs_operation *op;
@@ -453,8 +463,6 @@ static int afs_store_data(struct afs_vnode *vnode, struct iov_iter *iter,
 	op->file[0].dv_delta = 1;
 	op->store.write_iter = iter;
 	op->store.pos = pos;
-	op->store.first = first;
-	op->store.last = last;
 	op->store.size = size;
 	op->store.i_size = max(pos + size, i_size);
 	op->store.laundering = laundering;
@@ -499,40 +507,49 @@ static int afs_store_data(struct afs_vnode *vnode, struct iov_iter *iter,
 static void afs_extend_writeback(struct address_space *mapping,
 				 struct afs_vnode *vnode,
 				 long *_count,
-				 pgoff_t start,
-				 pgoff_t final_page,
-				 unsigned *_offset,
-				 unsigned *_to,
-				 bool new_content)
+				 loff_t start,
+				 loff_t max_len,
+				 bool new_content,
+				 unsigned int *_len)
 {
-	struct page *pages[8], *page;
-	unsigned long count = *_count, priv;
-	unsigned offset = *_offset, to = *_to, n, f, t;
-	int loop;
+	struct pagevec pvec;
+	struct page *page;
+	unsigned long priv;
+	unsigned int psize, filler = 0;
+	unsigned int f, t;
+	loff_t len = *_len;
+	pgoff_t index = (start + len) / PAGE_SIZE;
+	bool stop = true;
+	unsigned int i;
+
+	XA_STATE(xas, &mapping->i_pages, index);
+	pagevec_init(&pvec);
 
-	start++;
 	do {
-		_debug("more %lx [%lx]", start, count);
-		n = final_page - start + 1;
-		if (n > ARRAY_SIZE(pages))
-			n = ARRAY_SIZE(pages);
-		n = find_get_pages_contig(mapping, start, ARRAY_SIZE(pages), pages);
-		_debug("fgpc %u", n);
-		if (n == 0)
-			goto no_more;
-		if (pages[0]->index != start) {
-			do {
-				put_page(pages[--n]);
-			} while (n > 0);
-			goto no_more;
-		}
+		/* Firstly, we gather up a batch of contiguous dirty pages
+		 * under the RCU read lock - but we can't clear the dirty flags
+		 * there if any of those pages are mapped.
+		 */
+		rcu_read_lock();
 
-		for (loop = 0; loop < n; loop++) {
-			page = pages[loop];
-			if (to != PAGE_SIZE && !new_content)
+		xas_for_each(&xas, page, ULONG_MAX) {
+			stop = true;
+			if (xas_retry(&xas, page))
+				continue;
+			if (xa_is_value(page))
+				break;
+			if (page->index != index)
 				break;
-			if (page->index > final_page)
+
+			if (!page_cache_get_speculative(page)) {
+				xas_reset(&xas);
+				continue;
+			}
+
+			/* Has the page moved or been split? */
+			if (unlikely(page != xas_reload(&xas)))
 				break;
+
 			if (!trylock_page(page))
 				break;
 			if (!PageDirty(page) || PageWriteback(page)) {
@@ -540,6 +557,7 @@ static void afs_extend_writeback(struct address_space *mapping,
 				break;
 			}
 
+			psize = thp_size(page);
 			priv = page_private(page);
 			f = afs_page_dirty_from(page, priv);
 			t = afs_page_dirty_to(page, priv);
@@ -547,110 +565,126 @@ static void afs_extend_writeback(struct address_space *mapping,
 				unlock_page(page);
 				break;
 			}
-			to = t;
 
+			len += filler + t;
+			filler = psize - t;
+			if (len >= max_len || *_count <= 0)
+				stop = true;
+			else if (t == psize || new_content)
+				stop = false;
+
+			index += thp_nr_pages(page);
+			if (!pagevec_add(&pvec, page))
+				break;
+			if (stop)
+				break;
+		}
+
+		if (!stop)
+			xas_pause(&xas);
+		rcu_read_unlock();
+
+		/* Now, if we obtained any pages, we can shift them to being
+		 * writable and mark them for caching.
+		 */
+		if (!pagevec_count(&pvec))
+			break;
+
+		for (i = 0; i < pagevec_count(&pvec); i++) {
+			page = pvec.pages[i];
 			trace_afs_page_dirty(vnode, tracepoint_string("store+"), page);
 
 			if (!clear_page_dirty_for_io(page))
 				BUG();
 			if (test_set_page_writeback(page))
 				BUG();
+
+			*_count -= thp_nr_pages(page);
 			unlock_page(page);
-			put_page(page);
-		}
-		count += loop;
-		if (loop < n) {
-			for (; loop < n; loop++)
-				put_page(pages[loop]);
-			goto no_more;
 		}
 
-		start += loop;
-	} while (start <= final_page && count < 65536);
+		pagevec_release(&pvec);
+		cond_resched();
+	} while (!stop);
 
-no_more:
-	*_count = count;
-	*_offset = offset;
-	*_to = to;
+	*_len = len;
 }
 
 /*
  * Synchronously write back the locked page and any subsequent non-locked dirty
  * pages.
  */
-static int afs_write_back_from_locked_page(struct address_space *mapping,
-					   struct writeback_control *wbc,
-					   struct page *primary_page,
-					   pgoff_t final_page)
+static ssize_t afs_write_back_from_locked_page(struct address_space *mapping,
+					       struct writeback_control *wbc,
+					       struct page *page,
+					       loff_t start, loff_t end)
 {
 	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 	struct iov_iter iter;
-	unsigned long count, priv;
-	unsigned offset, to;
-	pgoff_t start, first, last;
-	loff_t i_size, pos, end;
+	unsigned long priv;
+	unsigned int offset, to, len, max_len;
+	loff_t i_size = i_size_read(&vnode->vfs_inode);
 	bool new_content = test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags);
+	long count = wbc->nr_to_write;
 	int ret;
 
-	_enter(",%lx", primary_page->index);
+	_enter(",%lx,%llx-%llx", page->index, start, end);
 
-	count = 1;
-	if (test_set_page_writeback(primary_page))
+	if (test_set_page_writeback(page))
 		BUG();
 
+	count -= thp_nr_pages(page);
+
 	/* Find all consecutive lockable dirty pages that have contiguous
 	 * written regions, stopping when we find a page that is not
 	 * immediately lockable, is not dirty or is missing, or we reach the
 	 * end of the range.
 	 */
-	start = primary_page->index;
-	priv = page_private(primary_page);
-	offset = afs_page_dirty_from(primary_page, priv);
-	to = afs_page_dirty_to(primary_page, priv);
-	trace_afs_page_dirty(vnode, tracepoint_string("store"), primary_page);
-
-	WARN_ON(offset == to);
-	if (offset == to)
-		trace_afs_page_dirty(vnode, tracepoint_string("WARN"), primary_page);
-
-	if (start < final_page &&
-	    (to == PAGE_SIZE || new_content))
-		afs_extend_writeback(mapping, vnode, &count, start, final_page,
-				     &offset, &to, new_content);
+	priv = page_private(page);
+	offset = afs_page_dirty_from(page, priv);
+	to = afs_page_dirty_to(page, priv);
+	trace_afs_page_dirty(vnode, tracepoint_string("store"), page);
+
+	len = to - offset;
+	start += offset;
+	if (start < i_size) {
+		/* Trim the write to the EOF; the extra data is ignored.  Also
+		 * put an upper limit on the size of a single storedata op.
+		 */
+		max_len = 65536 * 4096;
+		max_len = min_t(unsigned long long, max_len, end - start + 1);
+		max_len = min_t(unsigned long long, max_len, i_size - start);
+
+		if (len < max_len &&
+		    (to == thp_size(page) || new_content))
+			afs_extend_writeback(mapping, vnode, &count,
+					     start, max_len, new_content, &len);
+		len = min_t(loff_t, len, max_len);
+	}
 
 	/* We now have a contiguous set of dirty pages, each with writeback
 	 * set; the first page is still locked at this point, but all the rest
 	 * have been unlocked.
 	 */
-	unlock_page(primary_page);
-
-	first = primary_page->index;
-	last = first + count - 1;
-	_debug("write back %lx[%u..] to %lx[..%u]", first, offset, last, to);
-
-	pos = first;
-	pos <<= PAGE_SHIFT;
-	pos += offset;
-	end = last;
-	end <<= PAGE_SHIFT;
-	end += to;
+	unlock_page(page);
 
-	/* Trim the actual write down to the EOF */
-	i_size = i_size_read(&vnode->vfs_inode);
-	if (end > i_size)
-		end = i_size;
+	if (start < i_size) {
+		_debug("write back %x @%llx [%llx]", len, start, i_size);
 
-	if (pos < i_size) {
-		iov_iter_xarray(&iter, WRITE, &mapping->i_pages, pos, end - pos);
-		ret = afs_store_data(vnode, &iter, pos, first, last, false);
+		iov_iter_xarray(&iter, WRITE, &mapping->i_pages, start, len);
+		ret = afs_store_data(vnode, &iter, start, false);
 	} else {
+		_debug("write discard %x @%llx [%llx]", len, start, i_size);
+
 		/* The dirty region was entirely beyond the EOF. */
+		afs_pages_written_back(vnode, start, len);
 		ret = 0;
 	}
 
 	switch (ret) {
 	case 0:
-		ret = count;
+		wbc->nr_to_write = count;
+		ret = len;
 		break;
 
 	default:
@@ -662,13 +696,13 @@ static int afs_write_back_from_locked_page(struct address_space *mapping,
 	case -EKEYEXPIRED:
 	case -EKEYREJECTED:
 	case -EKEYREVOKED:
-		afs_redirty_pages(wbc, mapping, first, last);
+		afs_redirty_pages(wbc, mapping, start, len);
 		mapping_set_error(mapping, ret);
 		break;
 
 	case -EDQUOT:
 	case -ENOSPC:
-		afs_redirty_pages(wbc, mapping, first, last);
+		afs_redirty_pages(wbc, mapping, start, len);
 		mapping_set_error(mapping, -ENOSPC);
 		break;
 
@@ -680,7 +714,7 @@ static int afs_write_back_from_locked_page(struct address_space *mapping,
 	case -ENOMEDIUM:
 	case -ENXIO:
 		trace_afs_file_error(vnode, ret, afs_file_error_writeback_fail);
-		afs_kill_pages(mapping, first, last);
+		afs_kill_pages(mapping, start, len);
 		mapping_set_error(mapping, ret);
 		break;
 	}
@@ -695,19 +729,19 @@ static int afs_write_back_from_locked_page(struct address_space *mapping,
  */
 int afs_writepage(struct page *page, struct writeback_control *wbc)
 {
-	int ret;
+	ssize_t ret;
+	loff_t start;
 
 	_enter("{%lx},", page->index);
 
+	start = page->index * PAGE_SIZE;
 	ret = afs_write_back_from_locked_page(page->mapping, wbc, page,
-					      wbc->range_end >> PAGE_SHIFT);
+					      start, LLONG_MAX - start);
 	if (ret < 0) {
-		_leave(" = %d", ret);
-		return 0;
+		_leave(" = %zd", ret);
+		return ret;
 	}
 
-	wbc->nr_to_write -= ret;
-
 	_leave(" = 0");
 	return 0;
 }
@@ -717,35 +751,46 @@ int afs_writepage(struct page *page, struct writeback_control *wbc)
  */
 static int afs_writepages_region(struct address_space *mapping,
 				 struct writeback_control *wbc,
-				 pgoff_t index, pgoff_t end, pgoff_t *_next)
+				 loff_t start, loff_t end, loff_t *_next)
 {
 	struct page *page;
-	int ret, n;
+	ssize_t ret;
+	int n;
 
-	_enter(",,%lx,%lx,", index, end);
+	_enter("%llx,%llx,", start, end);
 
 	do {
-		n = find_get_pages_range_tag(mapping, &index, end,
-					PAGECACHE_TAG_DIRTY, 1, &page);
+		pgoff_t index = start / PAGE_SIZE;
+
+		n = find_get_pages_range_tag(mapping, &index, end / PAGE_SIZE,
+					     PAGECACHE_TAG_DIRTY, 1, &page);
 		if (!n)
 			break;
 
+		start = (loff_t)page->index * PAGE_SIZE; /* May regress with THPs */
+
 		_debug("wback %lx", page->index);
 
-		/*
-		 * at this point we hold neither the i_pages lock nor the
+		/* At this point we hold neither the i_pages lock nor the
 		 * page lock: the page may be truncated or invalidated
 		 * (changing page->mapping to NULL), or even swizzled
 		 * back from swapper_space to tmpfs file mapping
 		 */
-		ret = lock_page_killable(page);
-		if (ret < 0) {
-			put_page(page);
-			_leave(" = %d", ret);
-			return ret;
+		if (wbc->sync_mode != WB_SYNC_NONE) {
+			ret = lock_page_killable(page);
+			if (ret < 0) {
+				put_page(page);
+				return ret;
+			}
+		} else {
+			if (!trylock_page(page)) {
+				put_page(page);
+				return 0;
+			}
 		}
 
 		if (page->mapping != mapping || !PageDirty(page)) {
+			start += thp_size(page);
 			unlock_page(page);
 			put_page(page);
 			continue;
@@ -761,20 +806,20 @@ static int afs_writepages_region(struct address_space *mapping,
 
 		if (!clear_page_dirty_for_io(page))
 			BUG();
-		ret = afs_write_back_from_locked_page(mapping, wbc, page, end);
+		ret = afs_write_back_from_locked_page(mapping, wbc, page, start, end);
 		put_page(page);
 		if (ret < 0) {
-			_leave(" = %d", ret);
+			_leave(" = %zd", ret);
 			return ret;
 		}
 
-		wbc->nr_to_write -= ret;
+		start += ret * PAGE_SIZE;
 
 		cond_resched();
-	} while (index < end && wbc->nr_to_write > 0);
+	} while (wbc->nr_to_write > 0);
 
-	*_next = index;
-	_leave(" = 0 [%lx]", *_next);
+	*_next = start;
+	_leave(" = 0 [%llx]", *_next);
 	return 0;
 }
 
@@ -785,7 +830,7 @@ int afs_writepages(struct address_space *mapping,
 		   struct writeback_control *wbc)
 {
 	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
-	pgoff_t start, end, next;
+	loff_t start, next;
 	int ret;
 
 	_enter("");
@@ -800,22 +845,19 @@ int afs_writepages(struct address_space *mapping,
 		return 0;
 
 	if (wbc->range_cyclic) {
-		start = mapping->writeback_index;
-		end = -1;
-		ret = afs_writepages_region(mapping, wbc, start, end, &next);
+		start = mapping->writeback_index * PAGE_SIZE;
+		ret = afs_writepages_region(mapping, wbc, start, LLONG_MAX, &next);
 		if (start > 0 && wbc->nr_to_write > 0 && ret == 0)
 			ret = afs_writepages_region(mapping, wbc, 0, start,
 						    &next);
-		mapping->writeback_index = next;
+		mapping->writeback_index = next / PAGE_SIZE;
 	} else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
-		end = (pgoff_t)(LLONG_MAX >> PAGE_SHIFT);
-		ret = afs_writepages_region(mapping, wbc, 0, end, &next);
+		ret = afs_writepages_region(mapping, wbc, 0, LLONG_MAX, &next);
 		if (wbc->nr_to_write > 0)
 			mapping->writeback_index = next;
 	} else {
-		start = wbc->range_start >> PAGE_SHIFT;
-		end = wbc->range_end >> PAGE_SHIFT;
-		ret = afs_writepages_region(mapping, wbc, start, end, &next);
+		ret = afs_writepages_region(mapping, wbc,
+					    wbc->range_start, wbc->range_end, &next);
 	}
 
 	up_read(&vnode->validate_lock);
@@ -873,13 +915,13 @@ int afs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
  */
 vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
 {
+	struct page *page = thp_head(vmf->page);
 	struct file *file = vmf->vma->vm_file;
 	struct inode *inode = file_inode(file);
 	struct afs_vnode *vnode = AFS_FS_I(inode);
 	unsigned long priv;
 
-	_enter("{{%llx:%llu}},{%lx}",
-	       vnode->fid.vid, vnode->fid.vnode, vmf->page->index);
+	_enter("{{%llx:%llu}},{%lx}", vnode->fid.vid, vnode->fid.vnode, page->index);
 
 	sb_start_pagefault(inode->i_sb);
 
@@ -887,31 +929,33 @@ vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
 	 * be modified.  We then assume the entire page will need writing back.
 	 */
 #ifdef CONFIG_AFS_FSCACHE
-	if (PageFsCache(vmf->page) &&
-	    wait_on_page_bit_killable(vmf->page, PG_fscache) < 0)
+	if (PageFsCache(page) &&
+	    wait_on_page_bit_killable(page, PG_fscache) < 0)
 		return VM_FAULT_RETRY;
 #endif
 
-	if (PageWriteback(vmf->page) &&
-	    wait_on_page_bit_killable(vmf->page, PG_writeback) < 0)
+	if (PageWriteback(page) &&
+	    wait_on_page_bit_killable(page, PG_writeback) < 0)
 		return VM_FAULT_RETRY;
 
-	if (lock_page_killable(vmf->page) < 0)
+	if (lock_page_killable(page) < 0)
 		return VM_FAULT_RETRY;
 
 	/* We mustn't change page->private until writeback is complete as that
 	 * details the portion of the page we need to write back and we might
 	 * need to redirty the page if there's a problem.
 	 */
-	wait_on_page_writeback(vmf->page);
+	wait_on_page_writeback(page);
 
-	priv = afs_page_dirty(vmf->page, 0, PAGE_SIZE);
+	priv = afs_page_dirty(page, 0, thp_size(page));
 	priv = afs_page_dirty_mmapped(priv);
-	if (PagePrivate(vmf->page))
-		set_page_private(vmf->page, priv);
-	else
-		attach_page_private(vmf->page, (void *)priv);
-	trace_afs_page_dirty(vnode, tracepoint_string("mkwrite"), vmf->page);
+	if (PagePrivate(page)) {
+		set_page_private(page, priv);
+		trace_afs_page_dirty(vnode, tracepoint_string("mkwrite+"), page);
+	} else {
+		attach_page_private(page, (void *)priv);
+		trace_afs_page_dirty(vnode, tracepoint_string("mkwrite"), page);
+	}
 	file_update_time(file);
 
 	sb_end_pagefault(inode->i_sb);
@@ -964,7 +1008,7 @@ int afs_launder_page(struct page *page)
 	priv = page_private(page);
 	if (clear_page_dirty_for_io(page)) {
 		f = 0;
-		t = PAGE_SIZE;
+		t = thp_size(page);
 		if (PagePrivate(page)) {
 			f = afs_page_dirty_from(page, priv);
 			t = afs_page_dirty_to(page, priv);
@@ -976,12 +1020,12 @@ int afs_launder_page(struct page *page)
 		iov_iter_bvec(&iter, WRITE, bv, 1, bv[0].bv_len);
 
 		trace_afs_page_dirty(vnode, tracepoint_string("launder"), page);
-		ret = afs_store_data(vnode, &iter, (loff_t)page->index << PAGE_SHIFT,
-				     page->index, page->index, true);
+		ret = afs_store_data(vnode, &iter, (loff_t)page->index * PAGE_SIZE,
+				     true);
 	}
 
-	detach_page_private(page);
 	trace_afs_page_dirty(vnode, tracepoint_string("laundered"), page);
+	detach_page_private(page);
 	wait_on_page_fscache(page);
 	return ret;
 }

[PATCH 26/33] afs: Use the fs operation ops to handle FetchData completion

[David Howells]

Use the 'success' and 'aborted' afs_operations_ops methods and add a
'failed' method to handle the completion of an AFS.FetchData,
AFS.FetchData64 or YFS.FetchData64 RPC operation rather than directly
calling the done func pointed to by the afs_read struct from the call
delivery handler.

This means the done function will be called back on error also, not just on
successful completion.

This allows motion towards asynchronous data reception on data fetch calls
and allows any error to be handed off to the fscache read helper in the
same place as a successful completion.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-afs@lists.infradead.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
---

 fs/afs/file.c         |   15 +++++++++++++++
 fs/afs/fs_operation.c |    4 +++-
 fs/afs/fsclient.c     |    3 ---
 fs/afs/internal.h     |    1 +
 fs/afs/yfsclient.c    |    3 ---
 5 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/fs/afs/file.c b/fs/afs/file.c
index f6282ac0d222..231e9fd7882b 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -255,6 +255,19 @@ void afs_put_read(struct afs_read *req)
 	}
 }
 
+static void afs_fetch_data_notify(struct afs_operation *op)
+{
+	struct afs_read *req = op->fetch.req;
+	int error = op->error;
+
+	if (error == -ECONNABORTED)
+		error = afs_abort_to_error(op->ac.abort_code);
+	req->error = error;
+
+	if (req->done)
+		req->done(req);
+}
+
 static void afs_fetch_data_success(struct afs_operation *op)
 {
 	struct afs_vnode *vnode = op->file[0].vnode;
@@ -263,6 +276,7 @@ static void afs_fetch_data_success(struct afs_operation *op)
 	afs_vnode_commit_status(op, &op->file[0]);
 	afs_stat_v(vnode, n_fetches);
 	atomic_long_add(op->fetch.req->actual_len, &op->net->n_fetch_bytes);
+	afs_fetch_data_notify(op);
 }
 
 static void afs_fetch_data_put(struct afs_operation *op)
@@ -276,6 +290,7 @@ static const struct afs_operation_ops afs_fetch_data_operation = {
 	.issue_yfs_rpc	= yfs_fs_fetch_data,
 	.success	= afs_fetch_data_success,
 	.aborted	= afs_check_for_remote_deletion,
+	.failed		= afs_fetch_data_notify,
 	.put		= afs_fetch_data_put,
 };
 
diff --git a/fs/afs/fs_operation.c b/fs/afs/fs_operation.c
index 97cab12b0a6c..938e28a00101 100644
--- a/fs/afs/fs_operation.c
+++ b/fs/afs/fs_operation.c
@@ -195,8 +195,10 @@ void afs_wait_for_operation(struct afs_operation *op)
 	case -ECONNABORTED:
 		if (op->ops->aborted)
 			op->ops->aborted(op);
-		break;
+		fallthrough;
 	default:
+		if (op->ops->failed)
+			op->ops->failed(op);
 		break;
 	}
 
diff --git a/fs/afs/fsclient.c b/fs/afs/fsclient.c
index 31e6b3635541..5e34f4dbd385 100644
--- a/fs/afs/fsclient.c
+++ b/fs/afs/fsclient.c
@@ -392,9 +392,6 @@ static int afs_deliver_fs_fetch_data(struct afs_call *call)
 		break;
 	}
 
-	if (req->done)
-		req->done(req);
-
 	_leave(" = 0 [done]");
 	return 0;
 }
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index daf5339ae316..d46389406021 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -742,6 +742,7 @@ struct afs_operation_ops {
 	void (*issue_yfs_rpc)(struct afs_operation *op);
 	void (*success)(struct afs_operation *op);
 	void (*aborted)(struct afs_operation *op);
+	void (*failed)(struct afs_operation *op);
 	void (*edit_dir)(struct afs_operation *op);
 	void (*put)(struct afs_operation *op);
 };
diff --git a/fs/afs/yfsclient.c b/fs/afs/yfsclient.c
index 363d6dd276c0..2b35cba8ad62 100644
--- a/fs/afs/yfsclient.c
+++ b/fs/afs/yfsclient.c
@@ -449,9 +449,6 @@ static int yfs_deliver_fs_fetch_data64(struct afs_call *call)
 		break;
 	}
 
-	if (req->done)
-		req->done(req);
-
 	_leave(" = 0 [done]");
 	return 0;
 }

[PATCH 27/33] afs: Use new fscache read helper API

[David Howells]

Make AFS use the new fscache read helpers to implement the VM read
operations:

 - afs_readpage() now hands off responsibility to fscache_readpage().

 - afs_readpages() is gone and replaced with afs_readahead().

 - afs_readahead() just hands off responsibility to fscache_readahead().

These make use of the cache if a cookie is supplied, otherwise just call
the ->issue_op() method a sufficient number of times to complete the entire
request.

Changes:
 - Folded in error handling fixes to afs_req_issue_op().

Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-afs@lists.infradead.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
---

 fs/afs/Kconfig    |    1 
 fs/afs/file.c     |  321 ++++++++++++-----------------------------------------
 fs/afs/fsclient.c |    1 
 fs/afs/internal.h |    3 
 4 files changed, 80 insertions(+), 246 deletions(-)

diff --git a/fs/afs/Kconfig b/fs/afs/Kconfig
index 1ad211d72b3b..fc8ba9142f2f 100644
--- a/fs/afs/Kconfig
+++ b/fs/afs/Kconfig
@@ -4,6 +4,7 @@ config AFS_FS
 	depends on INET
 	select AF_RXRPC
 	select DNS_RESOLVER
+	select NETFS_SUPPORT
 	help
 	  If you say Y here, you will get an experimental Andrew File System
 	  driver. It currently only supports unsecured read-only AFS access.
diff --git a/fs/afs/file.c b/fs/afs/file.c
index 231e9fd7882b..8f28d4f4cfd7 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -14,6 +14,7 @@
 #include <linux/gfp.h>
 #include <linux/task_io_accounting_ops.h>
 #include <linux/mm.h>
+#include <linux/netfs.h>
 #include "internal.h"
 
 static int afs_file_mmap(struct file *file, struct vm_area_struct *vma);
@@ -22,8 +23,7 @@ static void afs_invalidatepage(struct page *page, unsigned int offset,
 			       unsigned int length);
 static int afs_releasepage(struct page *page, gfp_t gfp_flags);
 
-static int afs_readpages(struct file *filp, struct address_space *mapping,
-			 struct list_head *pages, unsigned nr_pages);
+static void afs_readahead(struct readahead_control *ractl);
 
 const struct file_operations afs_file_operations = {
 	.open		= afs_open,
@@ -48,7 +48,7 @@ const struct inode_operations afs_file_inode_operations = {
 
 const struct address_space_operations afs_fs_aops = {
 	.readpage	= afs_readpage,
-	.readpages	= afs_readpages,
+	.readahead	= afs_readahead,
 	.set_page_dirty	= afs_set_page_dirty,
 	.launder_page	= afs_launder_page,
 	.releasepage	= afs_releasepage,
@@ -185,61 +185,17 @@ int afs_release(struct inode *inode, struct file *file)
 }
 
 /*
- * Handle completion of a read operation.
+ * Allocate a new read record.
  */
-static void afs_file_read_done(struct afs_read *req)
+struct afs_read *afs_alloc_read(gfp_t gfp)
 {
-	struct afs_vnode *vnode = req->vnode;
-	struct page *page;
-	pgoff_t index = req->pos >> PAGE_SHIFT;
-	pgoff_t last = index + req->nr_pages - 1;
-
-	XA_STATE(xas, &vnode->vfs_inode.i_mapping->i_pages, index);
-
-	if (iov_iter_count(req->iter) > 0) {
-		/* The read was short - clear the excess buffer. */
-		_debug("afterclear %zx %zx %llx/%llx",
-		       req->iter->iov_offset,
-		       iov_iter_count(req->iter),
-		       req->actual_len, req->len);
-		iov_iter_zero(iov_iter_count(req->iter), req->iter);
-	}
-
-	rcu_read_lock();
-	xas_for_each(&xas, page, last) {
-		page_endio(page, false, 0);
-		put_page(page);
-	}
-	rcu_read_unlock();
-
-	task_io_account_read(req->len);
-	req->cleanup = NULL;
-}
-
-/*
- * Dispose of our locks and refs on the pages if the read failed.
- */
-static void afs_file_read_cleanup(struct afs_read *req)
-{
-	struct page *page;
-	pgoff_t index = req->pos >> PAGE_SHIFT;
-	pgoff_t last = index + req->nr_pages - 1;
-
-	if (req->iter) {
-		XA_STATE(xas, &req->vnode->vfs_inode.i_mapping->i_pages, index);
-
-		_enter("%lu,%u,%zu", index, req->nr_pages, iov_iter_count(req->iter));
+	struct afs_read *req;
 
-		rcu_read_lock();
-		xas_for_each(&xas, page, last) {
-			BUG_ON(xa_is_value(page));
-			BUG_ON(PageCompound(page));
+	req = kzalloc(sizeof(struct afs_read), gfp);
+	if (req)
+		refcount_set(&req->usage, 1);
 
-			page_endio(page, false, req->error);
-			put_page(page);
-		}
-		rcu_read_unlock();
-	}
+	return req;
 }
 
 /*
@@ -258,14 +214,20 @@ void afs_put_read(struct afs_read *req)
 static void afs_fetch_data_notify(struct afs_operation *op)
 {
 	struct afs_read *req = op->fetch.req;
+	struct netfs_read_subrequest *subreq = req->subreq;
 	int error = op->error;
 
 	if (error == -ECONNABORTED)
 		error = afs_abort_to_error(op->ac.abort_code);
 	req->error = error;
 
-	if (req->done)
+	if (subreq) {
+		__set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
+		netfs_subreq_terminated(subreq, error ?: req->actual_len);
+		req->subreq = NULL;
+	} else if (req->done) {
 		req->done(req);
+	}
 }
 
 static void afs_fetch_data_success(struct afs_operation *op)
@@ -319,222 +281,89 @@ int afs_fetch_data(struct afs_vnode *vnode, struct afs_read *req)
 	return afs_do_sync_operation(op);
 }
 
-/*
- * read page from file, directory or symlink, given a key to use
- */
-static int afs_page_filler(struct key *key, struct page *page)
+static void afs_req_issue_op(struct netfs_read_subrequest *subreq)
 {
-	struct inode *inode = page->mapping->host;
-	struct afs_vnode *vnode = AFS_FS_I(inode);
-	struct afs_read *req;
+	struct afs_vnode *vnode = AFS_FS_I(subreq->rreq->inode);
+	struct afs_read *fsreq;
 	int ret;
 
-	_enter("{%x},{%lu},{%lu}", key_serial(key), inode->i_ino, page->index);
+	fsreq = afs_alloc_read(GFP_NOFS);
+	if (!fsreq)
+		return netfs_subreq_terminated(subreq, -ENOMEM);
 
-	BUG_ON(!PageLocked(page));
+	fsreq->subreq	= subreq;
+	fsreq->pos	= subreq->start + subreq->transferred;
+	fsreq->len	= subreq->len   - subreq->transferred;
+	fsreq->key	= subreq->rreq->netfs_priv;
+	fsreq->vnode	= vnode;
+	fsreq->iter	= &fsreq->def_iter;
 
-	ret = -ESTALE;
-	if (test_bit(AFS_VNODE_DELETED, &vnode->flags))
-		goto error;
+	iov_iter_xarray(&fsreq->def_iter, READ,
+			&fsreq->vnode->vfs_inode.i_mapping->i_pages,
+			fsreq->pos, fsreq->len);
 
-	req = kzalloc(sizeof(struct afs_read), GFP_KERNEL);
-	if (!req)
-		goto enomem;
-
-	refcount_set(&req->usage, 1);
-	req->vnode		= vnode;
-	req->key		= key_get(key);
-	req->pos		= (loff_t)page->index << PAGE_SHIFT;
-	req->len		= thp_size(page);
-	req->nr_pages		= thp_nr_pages(page);
-	req->done		= afs_file_read_done;
-	req->cleanup		= afs_file_read_cleanup;
-
-	get_page(page);
-	iov_iter_xarray(&req->def_iter, READ, &page->mapping->i_pages,
-			req->pos, req->len);
-	req->iter = &req->def_iter;
-
-	ret = afs_fetch_data(vnode, req);
+	ret = afs_fetch_data(fsreq->vnode, fsreq);
 	if (ret < 0)
-		goto fetch_error;
-
-	afs_put_read(req);
-	_leave(" = 0");
-	return 0;
-
-fetch_error:
-	switch (ret) {
-	case -EINTR:
-	case -ENOMEM:
-	case -ERESTARTSYS:
-	case -EAGAIN:
-		afs_put_read(req);
-		goto error;
-	case -ENOENT:
-		_debug("got NOENT from server - marking file deleted and stale");
-		set_bit(AFS_VNODE_DELETED, &vnode->flags);
-		ret = -ESTALE;
-		/* Fall through */
-	default:
-		page_endio(page, false, ret);
-		afs_put_read(req);
-		_leave(" = %d", ret);
-		return ret;
-	}
-
-enomem:
-	ret = -ENOMEM;
-error:
-	unlock_page(page);
-	_leave(" = %d", ret);
-	return ret;
+		return netfs_subreq_terminated(subreq, ret);
 }
 
-/*
- * read page from file, directory or symlink, given a file to nominate the key
- * to be used
- */
-static int afs_readpage(struct file *file, struct page *page)
+static int afs_symlink_readpage(struct page *page)
 {
-	struct key *key;
+	struct afs_vnode *vnode = AFS_FS_I(page->mapping->host);
+	struct afs_read *fsreq;
 	int ret;
 
-	if (file) {
-		key = afs_file_key(file);
-		ASSERT(key != NULL);
-		ret = afs_page_filler(key, page);
-	} else {
-		struct inode *inode = page->mapping->host;
-		key = afs_request_key(AFS_FS_S(inode->i_sb)->cell);
-		if (IS_ERR(key)) {
-			ret = PTR_ERR(key);
-		} else {
-			ret = afs_page_filler(key, page);
-			key_put(key);
-		}
-	}
-	return ret;
-}
-
-/*
- * Read a contiguous set of pages.
- */
-static int afs_readpages_one(struct file *file, struct address_space *mapping,
-			     struct list_head *pages)
-{
-	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
-	struct afs_read *req;
-	struct list_head *p;
-	struct page *first, *page;
-	pgoff_t index;
-	int ret, n;
-
-	/* Count the number of contiguous pages at the front of the list.  Note
-	 * that the list goes prev-wards rather than next-wards.
-	 */
-	first = lru_to_page(pages);
-	index = first->index + 1;
-	n = 1;
-	for (p = first->lru.prev; p != pages; p = p->prev) {
-		page = list_entry(p, struct page, lru);
-		if (page->index != index)
-			break;
-		index++;
-		n++;
-	}
-
-	req = kzalloc(sizeof(struct afs_read), GFP_NOFS);
-	if (!req)
+	fsreq = afs_alloc_read(GFP_NOFS);
+	if (!fsreq)
 		return -ENOMEM;
 
-	refcount_set(&req->usage, 1);
-	req->vnode = vnode;
-	req->key = key_get(afs_file_key(file));
-	req->done = afs_file_read_done;
-	req->cleanup = afs_file_read_cleanup;
-	req->pos = first->index;
-	req->pos <<= PAGE_SHIFT;
-
-	/* Add pages to the LRU until it fails.  We keep the pages ref'd and
-	 * locked until the read is complete.
-	 *
-	 * Note that it's possible for the file size to change whilst we're
-	 * doing this, but we rely on the server returning less than we asked
-	 * for if the file shrank.  We also rely on this to deal with a partial
-	 * page at the end of the file.
-	 */
-	do {
-		page = lru_to_page(pages);
-		list_del(&page->lru);
-		index = page->index;
-		if (add_to_page_cache_lru(page, mapping, index,
-					  readahead_gfp_mask(mapping))) {
-			put_page(page);
-			break;
-		}
-
-		req->nr_pages++;
-	} while (req->nr_pages < n);
-
-	if (req->nr_pages == 0) {
-		afs_put_read(req);
-		return 0;
-	}
-
-	req->len = req->nr_pages * PAGE_SIZE;
-	iov_iter_xarray(&req->def_iter, READ, &file->f_mapping->i_pages,
-			req->pos, req->len);
-	req->iter = &req->def_iter;
+	fsreq->pos	= page->index * PAGE_SIZE;
+	fsreq->len	= PAGE_SIZE;
+	fsreq->vnode	= vnode;
+	fsreq->iter	= &fsreq->def_iter;
+	iov_iter_xarray(&fsreq->def_iter, READ, &page->mapping->i_pages,
+			fsreq->pos, fsreq->len);
 
-	ret = afs_fetch_data(vnode, req);
-	if (ret < 0)
-		goto error;
+	ret = afs_fetch_data(fsreq->vnode, fsreq);
+	page_endio(page, false, ret);
+	return ret;
+}
 
-	afs_put_read(req);
-	return 0;
+static void afs_init_rreq(struct netfs_read_request *rreq, struct file *file)
+{
+	rreq->netfs_priv = key_get(afs_file_key(file));
+}
 
-error:
-	if (ret == -ENOENT) {
-		_debug("got NOENT from server - marking file deleted and stale");
-		set_bit(AFS_VNODE_DELETED, &vnode->flags);
-		ret = -ESTALE;
-	}
+static int afs_begin_cache_operation(struct netfs_read_request *rreq)
+{
+	struct afs_vnode *vnode = AFS_FS_I(rreq->inode);
 
-	afs_put_read(req);
-	return ret;
+	return fscache_begin_read_operation(rreq, afs_vnode_cache(vnode));
 }
 
-/*
- * read a set of pages
- */
-static int afs_readpages(struct file *file, struct address_space *mapping,
-			 struct list_head *pages, unsigned nr_pages)
+static void afs_priv_cleanup(struct address_space *mapping, void *netfs_priv)
 {
-	struct key *key = afs_file_key(file);
-	struct afs_vnode *vnode;
-	int ret = 0;
-
-	_enter("{%d},{%lu},,%d",
-	       key_serial(key), mapping->host->i_ino, nr_pages);
+	key_put(netfs_priv);
+}
 
-	ASSERT(key != NULL);
+static const struct netfs_read_request_ops afs_req_ops = {
+	.init_rreq		= afs_init_rreq,
+	.begin_cache_operation	= afs_begin_cache_operation,
+	.issue_op		= afs_req_issue_op,
+	.cleanup		= afs_priv_cleanup,
+};
 
-	vnode = AFS_FS_I(mapping->host);
-	if (test_bit(AFS_VNODE_DELETED, &vnode->flags)) {
-		_leave(" = -ESTALE");
-		return -ESTALE;
-	}
+static int afs_readpage(struct file *file, struct page *page)
+{
+	if (!file)
+		return afs_symlink_readpage(page);
 
-	/* attempt to read as many of the pages as possible */
-	while (!list_empty(pages)) {
-		ret = afs_readpages_one(file, mapping, pages);
-		if (ret < 0)
-			break;
-	}
+	return netfs_readpage(file, page, &afs_req_ops, NULL);
+}
 
-	_leave(" = %d [netting]", ret);
-	return ret;
+static void afs_readahead(struct readahead_control *ractl)
+{
+	netfs_readahead(ractl, &afs_req_ops, NULL);
 }
 
 /*
diff --git a/fs/afs/fsclient.c b/fs/afs/fsclient.c
index 5e34f4dbd385..2f695a260442 100644
--- a/fs/afs/fsclient.c
+++ b/fs/afs/fsclient.c
@@ -10,6 +10,7 @@
 #include <linux/sched.h>
 #include <linux/circ_buf.h>
 #include <linux/iversion.h>
+#include <linux/netfs.h>
 #include "internal.h"
 #include "afs_fs.h"
 #include "xdr_fs.h"
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index d46389406021..8a0c14557e59 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -14,6 +14,7 @@
 #include <linux/key.h>
 #include <linux/workqueue.h>
 #include <linux/sched.h>
+#define FSCACHE_USE_NEW_IO_API
 #include <linux/fscache.h>
 #include <linux/backing-dev.h>
 #include <linux/uuid.h>
@@ -207,6 +208,7 @@ struct afs_read {
 	loff_t			file_size;	/* File size returned by server */
 	struct key		*key;		/* The key to use to reissue the read */
 	struct afs_vnode	*vnode;		/* The file being read into. */
+	struct netfs_read_subrequest *subreq;	/* Fscache helper read request this belongs to */
 	afs_dataversion_t	data_version;	/* Version number returned by server */
 	refcount_t		usage;
 	unsigned int		call_debug_id;
@@ -1049,6 +1051,7 @@ extern void afs_put_wb_key(struct afs_wb_key *);
 extern int afs_open(struct inode *, struct file *);
 extern int afs_release(struct inode *, struct file *);
 extern int afs_fetch_data(struct afs_vnode *, struct afs_read *);
+extern struct afs_read *afs_alloc_read(gfp_t);
 extern void afs_put_read(struct afs_read *);
 
 static inline struct afs_read *afs_get_read(struct afs_read *req)

[PATCH 28/33] ceph: disable old fscache readpage handling

[David Howells]

From: Jeff Layton <jlayton@kernel.org>

With the new netfs read helper functions, we won't need a lot of this
infrastructure as it handles the pagecache pages itself. Rip out the
read handling for now, and much of the old infrastructure that deals in
individual pages.

The cookie handling is mostly unchanged, however.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: ceph-devel@vger.kernel.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
---

 fs/ceph/addr.c  |   31 +-------------
 fs/ceph/cache.c |  125 -------------------------------------------------------
 fs/ceph/cache.h |   91 ----------------------------------------
 fs/ceph/caps.c  |    9 ----
 4 files changed, 3 insertions(+), 253 deletions(-)

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 950552944436..2b17bb36e548 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -155,8 +155,6 @@ static void ceph_invalidatepage(struct page *page, unsigned int offset,
 		return;
 	}
 
-	ceph_invalidate_fscache_page(inode, page);
-
 	WARN_ON(!PageLocked(page));
 	if (!PagePrivate(page))
 		return;
@@ -175,10 +173,6 @@ static int ceph_releasepage(struct page *page, gfp_t g)
 	dout("%p releasepage %p idx %lu (%sdirty)\n", page->mapping->host,
 	     page, page->index, PageDirty(page) ? "" : "not ");
 
-	/* Can we release the page from the cache? */
-	if (!ceph_release_fscache_page(page, g))
-		return 0;
-
 	return !PagePrivate(page);
 }
 
@@ -213,10 +207,6 @@ static int ceph_do_readpage(struct file *filp, struct page *page)
 		return 0;
 	}
 
-	err = ceph_readpage_from_fscache(inode, page);
-	if (err == 0)
-		return -EINPROGRESS;
-
 	dout("readpage ino %llx.%llx file %p off %llu len %llu page %p index %lu\n",
 	     vino.ino, vino.snap, filp, off, len, page, page->index);
 	req = ceph_osdc_new_request(osdc, &ci->i_layout, vino, off, &len, 0, 1,
@@ -241,7 +231,6 @@ static int ceph_do_readpage(struct file *filp, struct page *page)
 	if (err == -ENOENT)
 		err = 0;
 	if (err < 0) {
-		ceph_fscache_readpage_cancel(inode, page);
 		if (err == -EBLOCKLISTED)
 			fsc->blocklisted = true;
 		goto out;
@@ -253,8 +242,6 @@ static int ceph_do_readpage(struct file *filp, struct page *page)
 		flush_dcache_page(page);
 
 	SetPageUptodate(page);
-	ceph_readpage_to_fscache(inode, page);
-
 out:
 	return err < 0 ? err : 0;
 }
@@ -294,10 +281,8 @@ static void finish_read(struct ceph_osd_request *req)
 	for (i = 0; i < num_pages; i++) {
 		struct page *page = osd_data->pages[i];
 
-		if (rc < 0 && rc != -ENOENT) {
-			ceph_fscache_readpage_cancel(inode, page);
+		if (rc < 0 && rc != -ENOENT)
 			goto unlock;
-		}
 		if (bytes < (int)PAGE_SIZE) {
 			/* zero (remainder of) page */
 			int s = bytes < 0 ? 0 : bytes;
@@ -307,7 +292,6 @@ static void finish_read(struct ceph_osd_request *req)
 		     page->index);
 		flush_dcache_page(page);
 		SetPageUptodate(page);
-		ceph_readpage_to_fscache(inode, page);
 unlock:
 		unlock_page(page);
 		put_page(page);
@@ -408,7 +392,6 @@ static int start_read(struct inode *inode, struct ceph_rw_context *rw_ctx,
 		     page->index);
 		if (add_to_page_cache_lru(page, &inode->i_data, page->index,
 					  GFP_KERNEL)) {
-			ceph_fscache_uncache_page(inode, page);
 			put_page(page);
 			dout("start_read %p add_to_page_cache failed %p\n",
 			     inode, page);
@@ -440,10 +423,8 @@ static int start_read(struct inode *inode, struct ceph_rw_context *rw_ctx,
 	return nr_pages;
 
 out_pages:
-	for (i = 0; i < nr_pages; ++i) {
-		ceph_fscache_readpage_cancel(inode, pages[i]);
+	for (i = 0; i < nr_pages; ++i)
 		unlock_page(pages[i]);
-	}
 	ceph_put_page_vector(pages, nr_pages, false);
 out_put:
 	ceph_osdc_put_request(req);
@@ -471,12 +452,6 @@ static int ceph_readpages(struct file *file, struct address_space *mapping,
 	if (ceph_inode(inode)->i_inline_version != CEPH_INLINE_NONE)
 		return -EINVAL;
 
-	rc = ceph_readpages_from_fscache(mapping->host, mapping, page_list,
-					 &nr_pages);
-
-	if (rc == 0)
-		goto out;
-
 	rw_ctx = ceph_find_rw_context(fi);
 	max = fsc->mount_options->rsize >> PAGE_SHIFT;
 	dout("readpages %p file %p ctx %p nr_pages %d max %d\n",
@@ -487,8 +462,6 @@ static int ceph_readpages(struct file *file, struct address_space *mapping,
 			goto out;
 	}
 out:
-	ceph_fscache_readpages_cancel(inode, page_list);
-
 	dout("readpages %p file %p ret %d\n", inode, file, rc);
 	return rc;
 }
diff --git a/fs/ceph/cache.c b/fs/ceph/cache.c
index 2f5cb6bc78e1..9cfadbb86568 100644
--- a/fs/ceph/cache.c
+++ b/fs/ceph/cache.c
@@ -173,7 +173,6 @@ void ceph_fscache_unregister_inode_cookie(struct ceph_inode_info* ci)
 
 	ci->fscache = NULL;
 
-	fscache_uncache_all_inode_pages(cookie, &ci->vfs_inode);
 	fscache_relinquish_cookie(cookie, &ci->i_vino, false);
 }
 
@@ -194,7 +193,6 @@ void ceph_fscache_file_set_cookie(struct inode *inode, struct file *filp)
 		dout("fscache_file_set_cookie %p %p disabling cache\n",
 		     inode, filp);
 		fscache_disable_cookie(ci->fscache, &ci->i_vino, false);
-		fscache_uncache_all_inode_pages(ci->fscache, inode);
 	} else {
 		fscache_enable_cookie(ci->fscache, &ci->i_vino, i_size_read(inode),
 				      ceph_fscache_can_enable, inode);
@@ -205,108 +203,6 @@ void ceph_fscache_file_set_cookie(struct inode *inode, struct file *filp)
 	}
 }
 
-static void ceph_readpage_from_fscache_complete(struct page *page, void *data, int error)
-{
-	if (!error)
-		SetPageUptodate(page);
-
-	unlock_page(page);
-}
-
-static inline bool cache_valid(struct ceph_inode_info *ci)
-{
-	return ci->i_fscache_gen == ci->i_rdcache_gen;
-}
-
-
-/* Atempt to read from the fscache,
- *
- * This function is called from the readpage_nounlock context. DO NOT attempt to
- * unlock the page here (or in the callback).
- */
-int ceph_readpage_from_fscache(struct inode *inode, struct page *page)
-{
-	struct ceph_inode_info *ci = ceph_inode(inode);
-	int ret;
-
-	if (!cache_valid(ci))
-		return -ENOBUFS;
-
-	ret = fscache_read_or_alloc_page(ci->fscache, page,
-					 ceph_readpage_from_fscache_complete, NULL,
-					 GFP_KERNEL);
-
-	switch (ret) {
-		case 0: /* Page found */
-			dout("page read submitted\n");
-			return 0;
-		case -ENOBUFS: /* Pages were not found, and can't be */
-		case -ENODATA: /* Pages were not found */
-			dout("page/inode not in cache\n");
-			return ret;
-		default:
-			dout("%s: unknown error ret = %i\n", __func__, ret);
-			return ret;
-	}
-}
-
-int ceph_readpages_from_fscache(struct inode *inode,
-				  struct address_space *mapping,
-				  struct list_head *pages,
-				  unsigned *nr_pages)
-{
-	struct ceph_inode_info *ci = ceph_inode(inode);
-	int ret;
-
-	if (!cache_valid(ci))
-		return -ENOBUFS;
-
-	ret = fscache_read_or_alloc_pages(ci->fscache, mapping, pages, nr_pages,
-					  ceph_readpage_from_fscache_complete,
-					  NULL, mapping_gfp_mask(mapping));
-
-	switch (ret) {
-		case 0: /* All pages found */
-			dout("all-page read submitted\n");
-			return 0;
-		case -ENOBUFS: /* Some pages were not found, and can't be */
-		case -ENODATA: /* some pages were not found */
-			dout("page/inode not in cache\n");
-			return ret;
-		default:
-			dout("%s: unknown error ret = %i\n", __func__, ret);
-			return ret;
-	}
-}
-
-void ceph_readpage_to_fscache(struct inode *inode, struct page *page)
-{
-	struct ceph_inode_info *ci = ceph_inode(inode);
-	int ret;
-
-	if (!PageFsCache(page))
-		return;
-
-	if (!cache_valid(ci))
-		return;
-
-	ret = fscache_write_page(ci->fscache, page, i_size_read(inode),
-				 GFP_KERNEL);
-	if (ret)
-		 fscache_uncache_page(ci->fscache, page);
-}
-
-void ceph_invalidate_fscache_page(struct inode* inode, struct page *page)
-{
-	struct ceph_inode_info *ci = ceph_inode(inode);
-
-	if (!PageFsCache(page))
-		return;
-
-	fscache_wait_on_page_write(ci->fscache, page);
-	fscache_uncache_page(ci->fscache, page);
-}
-
 void ceph_fscache_unregister_fs(struct ceph_fs_client* fsc)
 {
 	if (fscache_cookie_valid(fsc->fscache)) {
@@ -329,24 +225,3 @@ void ceph_fscache_unregister_fs(struct ceph_fs_client* fsc)
 	}
 	fsc->fscache = NULL;
 }
-
-/*
- * caller should hold CEPH_CAP_FILE_{RD,CACHE}
- */
-void ceph_fscache_revalidate_cookie(struct ceph_inode_info *ci)
-{
-	if (cache_valid(ci))
-		return;
-
-	/* resue i_truncate_mutex. There should be no pending
-	 * truncate while the caller holds CEPH_CAP_FILE_RD */
-	mutex_lock(&ci->i_truncate_mutex);
-	if (!cache_valid(ci)) {
-		if (fscache_check_consistency(ci->fscache, &ci->i_vino))
-			fscache_invalidate(ci->fscache);
-		spin_lock(&ci->i_ceph_lock);
-		ci->i_fscache_gen = ci->i_rdcache_gen;
-		spin_unlock(&ci->i_ceph_lock);
-	}
-	mutex_unlock(&ci->i_truncate_mutex);
-}
diff --git a/fs/ceph/cache.h b/fs/ceph/cache.h
index 89dbdd1eb14a..10c21317b62f 100644
--- a/fs/ceph/cache.h
+++ b/fs/ceph/cache.h
@@ -29,13 +29,10 @@ int ceph_readpages_from_fscache(struct inode *inode,
 				struct address_space *mapping,
 				struct list_head *pages,
 				unsigned *nr_pages);
-void ceph_readpage_to_fscache(struct inode *inode, struct page *page);
-void ceph_invalidate_fscache_page(struct inode* inode, struct page *page);
 
 static inline void ceph_fscache_inode_init(struct ceph_inode_info *ci)
 {
 	ci->fscache = NULL;
-	ci->i_fscache_gen = 0;
 }
 
 static inline void ceph_fscache_invalidate(struct inode *inode)
@@ -43,40 +40,6 @@ static inline void ceph_fscache_invalidate(struct inode *inode)
 	fscache_invalidate(ceph_inode(inode)->fscache);
 }
 
-static inline void ceph_fscache_uncache_page(struct inode *inode,
-					     struct page *page)
-{
-	struct ceph_inode_info *ci = ceph_inode(inode);
-	return fscache_uncache_page(ci->fscache, page);
-}
-
-static inline int ceph_release_fscache_page(struct page *page, gfp_t gfp)
-{
-	struct inode* inode = page->mapping->host;
-	struct ceph_inode_info *ci = ceph_inode(inode);
-	return fscache_maybe_release_page(ci->fscache, page, gfp);
-}
-
-static inline void ceph_fscache_readpage_cancel(struct inode *inode,
-						struct page *page)
-{
-	struct ceph_inode_info *ci = ceph_inode(inode);
-	if (fscache_cookie_valid(ci->fscache) && PageFsCache(page))
-		__fscache_uncache_page(ci->fscache, page);
-}
-
-static inline void ceph_fscache_readpages_cancel(struct inode *inode,
-						 struct list_head *pages)
-{
-	struct ceph_inode_info *ci = ceph_inode(inode);
-	return fscache_readpages_cancel(ci->fscache, pages);
-}
-
-static inline void ceph_disable_fscache_readpage(struct ceph_inode_info *ci)
-{
-	ci->i_fscache_gen = ci->i_rdcache_gen - 1;
-}
-
 #else
 
 static inline int ceph_fscache_register(void)
@@ -115,62 +78,10 @@ static inline void ceph_fscache_file_set_cookie(struct inode *inode,
 {
 }
 
-static inline void ceph_fscache_revalidate_cookie(struct ceph_inode_info *ci)
-{
-}
-
-static inline void ceph_fscache_uncache_page(struct inode *inode,
-					     struct page *pages)
-{
-}
-
-static inline int ceph_readpage_from_fscache(struct inode* inode,
-					     struct page *page)
-{
-	return -ENOBUFS;
-}
-
-static inline int ceph_readpages_from_fscache(struct inode *inode,
-					      struct address_space *mapping,
-					      struct list_head *pages,
-					      unsigned *nr_pages)
-{
-	return -ENOBUFS;
-}
-
-static inline void ceph_readpage_to_fscache(struct inode *inode,
-					    struct page *page)
-{
-}
-
 static inline void ceph_fscache_invalidate(struct inode *inode)
 {
 }
 
-static inline void ceph_invalidate_fscache_page(struct inode *inode,
-						struct page *page)
-{
-}
-
-static inline int ceph_release_fscache_page(struct page *page, gfp_t gfp)
-{
-	return 1;
-}
-
-static inline void ceph_fscache_readpage_cancel(struct inode *inode,
-						struct page *page)
-{
-}
-
-static inline void ceph_fscache_readpages_cancel(struct inode *inode,
-						 struct list_head *pages)
-{
-}
-
-static inline void ceph_disable_fscache_readpage(struct ceph_inode_info *ci)
-{
-}
-
 #endif
 
-#endif
+#endif /* _CEPH_CACHE_H */
diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 255a512f1277..ca07dfc60652 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -2730,10 +2730,6 @@ static int try_get_cap_refs(struct inode *inode, int need, int want,
 				*got = need | want;
 			else
 				*got = need;
-			if (S_ISREG(inode->i_mode) &&
-			    (need & CEPH_CAP_FILE_RD) &&
-			    !(*got & CEPH_CAP_FILE_CACHE))
-				ceph_disable_fscache_readpage(ci);
 			ceph_take_cap_refs(ci, *got, true);
 			ret = 1;
 		}
@@ -2983,11 +2979,6 @@ int ceph_get_caps(struct file *filp, int need, int want,
 		}
 		break;
 	}
-
-	if (S_ISREG(ci->vfs_inode.i_mode) &&
-	    (_got & CEPH_CAP_FILE_RD) && (_got & CEPH_CAP_FILE_CACHE))
-		ceph_fscache_revalidate_cookie(ci);
-
 	*got = _got;
 	return 0;
 }

[PATCH 29/33] ceph: rework PageFsCache handling

[David Howells]

From: Jeff Layton <jlayton@kernel.org>

With the new fscache API, the PageFsCache bit now indicates that the
page is being written to the cache and shouldn't be modified or released
until it's finished.

Change releasepage and invalidatepage to wait on that bit before
returning.

Also define FSCACHE_USE_NEW_IO_API so that we opt into the new fscache
API.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: ceph-devel@vger.kernel.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
---

 fs/ceph/addr.c  |    9 ++++++++-
 fs/ceph/super.h |    1 +
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 2b17bb36e548..fbfa49db06fd 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -146,6 +146,8 @@ static void ceph_invalidatepage(struct page *page, unsigned int offset,
 	struct ceph_inode_info *ci;
 	struct ceph_snap_context *snapc = page_snap_context(page);
 
+	wait_on_page_fscache(page);
+
 	inode = page->mapping->host;
 	ci = ceph_inode(inode);
 
@@ -168,11 +170,16 @@ static void ceph_invalidatepage(struct page *page, unsigned int offset,
 	ClearPagePrivate(page);
 }
 
-static int ceph_releasepage(struct page *page, gfp_t g)
+static int ceph_releasepage(struct page *page, gfp_t gfp_flags)
 {
 	dout("%p releasepage %p idx %lu (%sdirty)\n", page->mapping->host,
 	     page, page->index, PageDirty(page) ? "" : "not ");
 
+	if (PageFsCache(page)) {
+		if (!(gfp_flags & __GFP_DIRECT_RECLAIM) || !(gfp_flags & __GFP_FS))
+			return 0;
+		wait_on_page_fscache(page);
+	}
 	return !PagePrivate(page);
 }
 
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index b62d8fee3b86..96bd3487d788 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -21,6 +21,7 @@
 #include <linux/ceph/libceph.h>
 
 #ifdef CONFIG_CEPH_FSCACHE
+#define FSCACHE_USE_NEW_IO_API
 #include <linux/fscache.h>
 #endif
 

[PATCH 30/33] ceph: fix fscache invalidation

[David Howells]

From: Jeff Layton <jlayton@kernel.org>

Ensure that we invalidate the fscache whenever we invalidate the
pagecache.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: ceph-devel@vger.kernel.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
---

 fs/ceph/caps.c  |    1 +
 fs/ceph/inode.c |    1 +
 2 files changed, 2 insertions(+)

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index ca07dfc60652..c40f713d6d21 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -1867,6 +1867,7 @@ static int try_nonblocking_invalidate(struct inode *inode)
 	u32 invalidating_gen = ci->i_rdcache_gen;
 
 	spin_unlock(&ci->i_ceph_lock);
+	ceph_fscache_invalidate(inode);
 	invalidate_mapping_pages(&inode->i_data, 0, -1);
 	spin_lock(&ci->i_ceph_lock);
 
diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index adc8fc3c5d85..2caa6df0bcdf 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -1906,6 +1906,7 @@ static void ceph_do_invalidate_pages(struct inode *inode)
 	orig_gen = ci->i_rdcache_gen;
 	spin_unlock(&ci->i_ceph_lock);
 
+	ceph_fscache_invalidate(inode);
 	if (invalidate_inode_pages2(inode->i_mapping) < 0) {
 		pr_err("invalidate_pages %p fails\n", inode);
 	}

[PATCH 31/33] ceph: convert readpage to fscache read helper

[David Howells]

From: Jeff Layton <jlayton@kernel.org>

Have the ceph KConfig select NETFS_SUPPORT. Add a new netfs ops
structure and the operations for it. Convert ceph_readpage to use
the new netfs_readpage helper.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: ceph-devel@vger.kernel.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
---

 fs/ceph/Kconfig |    1 
 fs/ceph/addr.c  |  149 +++++++++++++++++++++++++++++++++++++++++++++++++++----
 fs/ceph/cache.h |   36 +++++++++++++
 3 files changed, 176 insertions(+), 10 deletions(-)

diff --git a/fs/ceph/Kconfig b/fs/ceph/Kconfig
index 471e40156065..94df854147d3 100644
--- a/fs/ceph/Kconfig
+++ b/fs/ceph/Kconfig
@@ -6,6 +6,7 @@ config CEPH_FS
 	select LIBCRC32C
 	select CRYPTO_AES
 	select CRYPTO
+	select NETFS_SUPPORT
 	default n
 	help
 	  Choose Y or M here to include support for mounting the
diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index fbfa49db06fd..95f39ff9bb24 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -12,6 +12,7 @@
 #include <linux/signal.h>
 #include <linux/iversion.h>
 #include <linux/ktime.h>
+#include <linux/netfs.h>
 
 #include "super.h"
 #include "mds_client.h"
@@ -183,6 +184,144 @@ static int ceph_releasepage(struct page *page, gfp_t gfp_flags)
 	return !PagePrivate(page);
 }
 
+static bool ceph_netfs_clamp_length(struct netfs_read_subrequest *subreq)
+{
+	struct inode *inode = subreq->rreq->mapping->host;
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	u64 objno, objoff;
+	u32 xlen;
+
+	/* Truncate the extent at the end of the current object */
+	ceph_calc_file_object_mapping(&ci->i_layout, subreq->start, subreq->len,
+				      &objno, &objoff, &xlen);
+	subreq->len = xlen;
+	return true;
+}
+
+static void finish_netfs_read(struct ceph_osd_request *req)
+{
+	struct ceph_fs_client *fsc = ceph_inode_to_client(req->r_inode);
+	struct ceph_osd_data *osd_data = osd_req_op_extent_osd_data(req, 0);
+	struct netfs_read_subrequest *subreq = req->r_priv;
+	int num_pages;
+	int err = req->r_result;
+
+	ceph_update_read_latency(&fsc->mdsc->metric, req->r_start_latency,
+				 req->r_end_latency, err);
+
+	dout("%s: result %d subreq->len=%zu i_size=%lld\n", __func__, req->r_result,
+	     subreq->len, i_size_read(req->r_inode));
+
+	/* no object means success but no data */
+	if (err == -ENOENT)
+		err = 0;
+	else if (err == -EBLOCKLISTED)
+		fsc->blocklisted = true;
+
+	if (err >= 0 && err < subreq->len)
+		__set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
+
+	netfs_subreq_terminated(subreq, err);
+
+	num_pages = calc_pages_for(osd_data->alignment, osd_data->length);
+	ceph_put_page_vector(osd_data->pages, num_pages, false);
+	iput(req->r_inode);
+}
+
+static void ceph_netfs_issue_op(struct netfs_read_subrequest *subreq)
+{
+	struct netfs_read_request *rreq = subreq->rreq;
+	struct inode *inode = rreq->mapping->host;
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
+	struct ceph_osd_request *req;
+	struct ceph_vino vino = ceph_vino(inode);
+	struct iov_iter iter;
+	struct page **pages;
+	size_t page_off;
+	int err = 0;
+	u64 len = subreq->len;
+
+	req = ceph_osdc_new_request(&fsc->client->osdc, &ci->i_layout, vino, subreq->start, &len,
+			0, 1, CEPH_OSD_OP_READ,
+			CEPH_OSD_FLAG_READ | fsc->client->osdc.client->options->read_from_replica,
+			NULL, ci->i_truncate_seq, ci->i_truncate_size, false);
+	if (IS_ERR(req)) {
+		err = PTR_ERR(req);
+		req = NULL;
+		goto out;
+	}
+
+	dout("%s: pos=%llu orig_len=%zu len=%llu\n", __func__, subreq->start, subreq->len, len);
+	iov_iter_xarray(&iter, READ, &rreq->mapping->i_pages, subreq->start, len);
+	err = iov_iter_get_pages_alloc(&iter, &pages, len, &page_off);
+	if (err < 0) {
+		dout("%s: iov_ter_get_pages_alloc returned %d\n", __func__, err);
+		goto out;
+	}
+
+	/* should always give us a page-aligned read */
+	WARN_ON_ONCE(page_off);
+	len = err;
+
+	osd_req_op_extent_osd_data_pages(req, 0, pages, len, 0, false, false);
+	req->r_callback = finish_netfs_read;
+	req->r_priv = subreq;
+	req->r_inode = inode;
+	ihold(inode);
+
+	err = ceph_osdc_start_request(req->r_osdc, req, false);
+	if (err)
+		iput(inode);
+out:
+	ceph_osdc_put_request(req);
+	if (err)
+		netfs_subreq_terminated(subreq, err);
+	dout("%s: result %d\n", __func__, err);
+}
+
+static void ceph_init_rreq(struct netfs_read_request *rreq, struct file *file)
+{
+}
+
+const struct netfs_read_request_ops ceph_readpage_netfs_ops = {
+	.init_rreq		= ceph_init_rreq,
+	.is_cache_enabled	= ceph_is_cache_enabled,
+	.begin_cache_operation	= ceph_begin_cache_operation,
+	.issue_op		= ceph_netfs_issue_op,
+	.clamp_length		= ceph_netfs_clamp_length,
+};
+
+/* read a single page, without unlocking it. */
+static int ceph_readpage(struct file *file, struct page *page)
+{
+	struct inode *inode = file_inode(file);
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	struct ceph_vino vino = ceph_vino(inode);
+	u64 off = page_offset(page);
+	u64 len = PAGE_SIZE;
+
+	if (ci->i_inline_version != CEPH_INLINE_NONE) {
+		/*
+		 * Uptodate inline data should have been added
+		 * into page cache while getting Fcr caps.
+		 */
+		if (off == 0) {
+			unlock_page(page);
+			return -EINVAL;
+		}
+		zero_user_segment(page, 0, PAGE_SIZE);
+		SetPageUptodate(page);
+		unlock_page(page);
+		return 0;
+	}
+
+	dout("readpage ino %llx.%llx file %p off %llu len %llu page %p index %lu\n",
+	     vino.ino, vino.snap, file, off, len, page, page->index);
+
+	return netfs_readpage(file, page, &ceph_readpage_netfs_ops, NULL);
+}
+
 /* read a single page, without unlocking it. */
 static int ceph_do_readpage(struct file *filp, struct page *page)
 {
@@ -253,16 +392,6 @@ static int ceph_do_readpage(struct file *filp, struct page *page)
 	return err < 0 ? err : 0;
 }
 
-static int ceph_readpage(struct file *filp, struct page *page)
-{
-	int r = ceph_do_readpage(filp, page);
-	if (r != -EINPROGRESS)
-		unlock_page(page);
-	else
-		r = 0;
-	return r;
-}
-
 /*
  * Finish an async read(ahead) op.
  */
diff --git a/fs/ceph/cache.h b/fs/ceph/cache.h
index 10c21317b62f..1409d6149281 100644
--- a/fs/ceph/cache.h
+++ b/fs/ceph/cache.h
@@ -9,6 +9,8 @@
 #ifndef _CEPH_CACHE_H
 #define _CEPH_CACHE_H
 
+#include <linux/netfs.h>
+
 #ifdef CONFIG_CEPH_FSCACHE
 
 extern struct fscache_netfs ceph_cache_netfs;
@@ -35,11 +37,31 @@ static inline void ceph_fscache_inode_init(struct ceph_inode_info *ci)
 	ci->fscache = NULL;
 }
 
+static inline struct fscache_cookie *ceph_fscache_cookie(struct ceph_inode_info *ci)
+{
+	return ci->fscache;
+}
+
 static inline void ceph_fscache_invalidate(struct inode *inode)
 {
 	fscache_invalidate(ceph_inode(inode)->fscache);
 }
 
+static inline bool ceph_is_cache_enabled(struct inode *inode)
+{
+	struct fscache_cookie *cookie = ceph_fscache_cookie(ceph_inode(inode));
+
+	if (!cookie)
+		return false;
+	return fscache_cookie_enabled(cookie);
+}
+
+static inline int ceph_begin_cache_operation(struct netfs_read_request *rreq)
+{
+	struct fscache_cookie *cookie = ceph_fscache_cookie(ceph_inode(rreq->inode));
+
+	return fscache_begin_read_operation(rreq, cookie);
+}
 #else
 
 static inline int ceph_fscache_register(void)
@@ -65,6 +87,11 @@ static inline void ceph_fscache_inode_init(struct ceph_inode_info *ci)
 {
 }
 
+static inline struct fscache_cookie *ceph_fscache_cookie(struct ceph_inode_info *ci)
+{
+	return NULL;
+}
+
 static inline void ceph_fscache_register_inode_cookie(struct inode *inode)
 {
 }
@@ -82,6 +109,15 @@ static inline void ceph_fscache_invalidate(struct inode *inode)
 {
 }
 
+static inline bool ceph_is_cache_enabled(struct inode *inode)
+{
+	return false;
+}
+
+static inline int ceph_begin_cache_operation(struct netfs_read_request *rreq)
+{
+	return -ENOBUFS;
+}
 #endif
 
 #endif /* _CEPH_CACHE_H */

[PATCH 32/33] ceph: plug write_begin into read helper

[David Howells]

From: Jeff Layton <jlayton@kernel.org>

Convert ceph_write_begin to use the netfs_write_begin helper. Most of
the ops we need for it are already in place from the readpage conversion
but we do add a new check_write_begin op since ceph needs to be able to
vet whether there is an incompatible writeback already in flight before
reading in the page.

With this, we can also remove the old ceph_do_readpage helper.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: ceph-devel@vger.kernel.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
---

 fs/ceph/addr.c |  187 ++++++++++++++++++--------------------------------------
 1 file changed, 61 insertions(+), 126 deletions(-)

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 95f39ff9bb24..18f660611ba1 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -322,76 +322,6 @@ static int ceph_readpage(struct file *file, struct page *page)
 	return netfs_readpage(file, page, &ceph_readpage_netfs_ops, NULL);
 }
 
-/* read a single page, without unlocking it. */
-static int ceph_do_readpage(struct file *filp, struct page *page)
-{
-	struct inode *inode = file_inode(filp);
-	struct ceph_inode_info *ci = ceph_inode(inode);
-	struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
-	struct ceph_osd_client *osdc = &fsc->client->osdc;
-	struct ceph_osd_request *req;
-	struct ceph_vino vino = ceph_vino(inode);
-	int err = 0;
-	u64 off = page_offset(page);
-	u64 len = PAGE_SIZE;
-
-	if (off >= i_size_read(inode)) {
-		zero_user_segment(page, 0, PAGE_SIZE);
-		SetPageUptodate(page);
-		return 0;
-	}
-
-	if (ci->i_inline_version != CEPH_INLINE_NONE) {
-		/*
-		 * Uptodate inline data should have been added
-		 * into page cache while getting Fcr caps.
-		 */
-		if (off == 0)
-			return -EINVAL;
-		zero_user_segment(page, 0, PAGE_SIZE);
-		SetPageUptodate(page);
-		return 0;
-	}
-
-	dout("readpage ino %llx.%llx file %p off %llu len %llu page %p index %lu\n",
-	     vino.ino, vino.snap, filp, off, len, page, page->index);
-	req = ceph_osdc_new_request(osdc, &ci->i_layout, vino, off, &len, 0, 1,
-				    CEPH_OSD_OP_READ, CEPH_OSD_FLAG_READ, NULL,
-				    ci->i_truncate_seq, ci->i_truncate_size,
-				    false);
-	if (IS_ERR(req))
-		return PTR_ERR(req);
-
-	osd_req_op_extent_osd_data_pages(req, 0, &page, len, 0, false, false);
-
-	err = ceph_osdc_start_request(osdc, req, false);
-	if (!err)
-		err = ceph_osdc_wait_request(osdc, req);
-
-	ceph_update_read_latency(&fsc->mdsc->metric, req->r_start_latency,
-				 req->r_end_latency, err);
-
-	ceph_osdc_put_request(req);
-	dout("readpage result %d\n", err);
-
-	if (err == -ENOENT)
-		err = 0;
-	if (err < 0) {
-		if (err == -EBLOCKLISTED)
-			fsc->blocklisted = true;
-		goto out;
-	}
-	if (err < PAGE_SIZE)
-		/* zero fill remainder of page */
-		zero_user_segment(page, err, PAGE_SIZE);
-	else
-		flush_dcache_page(page);
-
-	SetPageUptodate(page);
-out:
-	return err < 0 ? err : 0;
-}
-
 /*
  * Finish an async read(ahead) op.
  */
@@ -1411,6 +1341,40 @@ ceph_find_incompatible(struct page *page)
 	return NULL;
 }
 
+static int ceph_netfs_check_write_begin(struct file *file, loff_t pos, unsigned int len,
+					struct page *page, void **_fsdata)
+{
+	struct inode *inode = file_inode(file);
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	struct ceph_snap_context *snapc;
+
+	snapc = ceph_find_incompatible(page);
+	if (snapc) {
+		int r;
+
+		unlock_page(page);
+		put_page(page);
+		if (IS_ERR(snapc))
+			return PTR_ERR(snapc);
+
+		ceph_queue_writeback(inode);
+		r = wait_event_killable(ci->i_cap_wq,
+					context_is_writeable_or_written(inode, snapc));
+		ceph_put_snap_context(snapc);
+		return r == 0 ? -EAGAIN : r;
+	}
+	return 0;
+}
+
+const struct netfs_read_request_ops ceph_netfs_write_begin_ops = {
+	.init_rreq		= ceph_init_rreq,
+	.is_cache_enabled	= ceph_is_cache_enabled,
+	.begin_cache_operation	= ceph_begin_cache_operation,
+	.issue_op		= ceph_netfs_issue_op,
+	.clamp_length		= ceph_netfs_clamp_length,
+	.check_write_begin	= ceph_netfs_check_write_begin,
+};
+
 /*
  * We are only allowed to write into/dirty the page if the page is
  * clean, or already dirty within the same snap context.
@@ -1421,75 +1385,46 @@ static int ceph_write_begin(struct file *file, struct address_space *mapping,
 {
 	struct inode *inode = file_inode(file);
 	struct ceph_inode_info *ci = ceph_inode(inode);
-	struct ceph_snap_context *snapc;
 	struct page *page = NULL;
 	pgoff_t index = pos >> PAGE_SHIFT;
-	int pos_in_page = pos & ~PAGE_MASK;
-	int r = 0;
-
-	dout("write_begin file %p inode %p page %p %d~%d\n", file, inode, page, (int)pos, (int)len);
-
-	for (;;) {
-		page = grab_cache_page_write_begin(mapping, index, flags);
-		if (!page) {
-			r = -ENOMEM;
-			break;
-		}
-
-		snapc = ceph_find_incompatible(page);
-		if (snapc) {
-			if (IS_ERR(snapc)) {
-				r = PTR_ERR(snapc);
-				break;
-			}
-			unlock_page(page);
-			put_page(page);
-			page = NULL;
-			ceph_queue_writeback(inode);
-			r = wait_event_killable(ci->i_cap_wq,
-						context_is_writeable_or_written(inode, snapc));
-			ceph_put_snap_context(snapc);
-			if (r != 0)
-				break;
-			continue;
-		}
-
-		if (PageUptodate(page)) {
-			dout(" page %p already uptodate\n", page);
-			break;
-		}
+	int r;
 
+	if (ci->i_inline_version != CEPH_INLINE_NONE) {
 		/*
-		 * In some cases we don't need to read at all:
-		 * - full page write
-		 * - write that lies completely beyond EOF
-		 * - write that covers the the page from start to EOF or beyond it
+		 * In principle, we should never get here, as the inode should have been uninlined
+		 * before we're allowed to write to the page (in write_iter or page_mkwrite).
 		 */
-		if ((pos_in_page == 0 && len == PAGE_SIZE) ||
-		    (pos >= i_size_read(inode)) ||
-		    (pos_in_page == 0 && (pos + len) >= i_size_read(inode))) {
-			zero_user_segments(page, 0, pos_in_page,
-					   pos_in_page + len, PAGE_SIZE);
-			break;
-		}
+		WARN_ONCE(1, "ceph: write_begin called on still-inlined inode!\n");
 
 		/*
-		 * We need to read it. If we get back -EINPROGRESS, then the page was
-		 * handed off to fscache and it will be unlocked when the read completes.
-		 * Refind the page in that case so we can reacquire the page lock. Otherwise
-		 * we got a hard error or the read was completed synchronously.
+		 * Uptodate inline data should have been added
+		 * into page cache while getting Fcr caps.
 		 */
-		r = ceph_do_readpage(file, page);
-		if (r != -EINPROGRESS)
-			break;
+		if (index == 0) {
+			r = -EINVAL;
+			goto out;
+		}
+
+		page = grab_cache_page_write_begin(mapping, index, flags);
+		if (!page)
+			return -ENOMEM;
+
+		zero_user_segment(page, 0, PAGE_SIZE);
+		SetPageUptodate(page);
+		r = 0;
+		goto out;
 	}
 
+	r = netfs_write_begin(file, inode->i_mapping, pos, len, 0, &page, NULL,
+			      &ceph_netfs_write_begin_ops, NULL);
+out:
+	if (r == 0)
+		wait_on_page_fscache(page);
 	if (r < 0) {
-		if (page) {
-			unlock_page(page);
+		if (page)
 			put_page(page);
-		}
 	} else {
+		WARN_ON_ONCE(!PageLocked(page));
 		*pagep = page;
 	}
 	return r;

[PATCH 33/33] ceph: convert ceph_readpages to ceph_readahead

[David Howells]

From: Jeff Layton <jlayton@kernel.org>

Convert ceph_readpages to ceph_readahead and make it use
netfs_readahead. With this we can rip out a lot of the old
readpage/readpages infrastructure.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: ceph-devel@vger.kernel.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
---

 fs/ceph/addr.c |  229 ++++++++------------------------------------------------
 1 file changed, 34 insertions(+), 195 deletions(-)

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 18f660611ba1..0dd64d31eff6 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -322,214 +322,53 @@ static int ceph_readpage(struct file *file, struct page *page)
 	return netfs_readpage(file, page, &ceph_readpage_netfs_ops, NULL);
 }
 
-/*
- * Finish an async read(ahead) op.
- */
-static void finish_read(struct ceph_osd_request *req)
+static void ceph_readahead_cleanup(struct address_space *mapping, void *priv)
 {
-	struct inode *inode = req->r_inode;
-	struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
-	struct ceph_osd_data *osd_data;
-	int rc = req->r_result <= 0 ? req->r_result : 0;
-	int bytes = req->r_result >= 0 ? req->r_result : 0;
-	int num_pages;
-	int i;
-
-	dout("finish_read %p req %p rc %d bytes %d\n", inode, req, rc, bytes);
-	if (rc == -EBLOCKLISTED)
-		ceph_inode_to_client(inode)->blocklisted = true;
-
-	/* unlock all pages, zeroing any data we didn't read */
-	osd_data = osd_req_op_extent_osd_data(req, 0);
-	BUG_ON(osd_data->type != CEPH_OSD_DATA_TYPE_PAGES);
-	num_pages = calc_pages_for((u64)osd_data->alignment,
-					(u64)osd_data->length);
-	for (i = 0; i < num_pages; i++) {
-		struct page *page = osd_data->pages[i];
-
-		if (rc < 0 && rc != -ENOENT)
-			goto unlock;
-		if (bytes < (int)PAGE_SIZE) {
-			/* zero (remainder of) page */
-			int s = bytes < 0 ? 0 : bytes;
-			zero_user_segment(page, s, PAGE_SIZE);
-		}
- 		dout("finish_read %p uptodate %p idx %lu\n", inode, page,
-		     page->index);
-		flush_dcache_page(page);
-		SetPageUptodate(page);
-unlock:
-		unlock_page(page);
-		put_page(page);
-		bytes -= PAGE_SIZE;
-	}
-
-	ceph_update_read_latency(&fsc->mdsc->metric, req->r_start_latency,
-				 req->r_end_latency, rc);
-
-	kfree(osd_data->pages);
-}
-
-/*
- * start an async read(ahead) operation.  return nr_pages we submitted
- * a read for on success, or negative error code.
- */
-static int start_read(struct inode *inode, struct ceph_rw_context *rw_ctx,
-		      struct list_head *page_list, int max)
-{
-	struct ceph_osd_client *osdc =
-		&ceph_inode_to_client(inode)->client->osdc;
+	struct inode *inode = mapping->host;
 	struct ceph_inode_info *ci = ceph_inode(inode);
-	struct page *page = lru_to_page(page_list);
-	struct ceph_vino vino;
-	struct ceph_osd_request *req;
-	u64 off;
-	u64 len;
-	int i;
-	struct page **pages;
-	pgoff_t next_index;
-	int nr_pages = 0;
-	int got = 0;
-	int ret = 0;
-
-	if (!rw_ctx) {
-		/* caller of readpages does not hold buffer and read caps
-		 * (fadvise, madvise and readahead cases) */
-		int want = CEPH_CAP_FILE_CACHE;
-		ret = ceph_try_get_caps(inode, CEPH_CAP_FILE_RD, want,
-					true, &got);
-		if (ret < 0) {
-			dout("start_read %p, error getting cap\n", inode);
-		} else if (!(got & want)) {
-			dout("start_read %p, no cache cap\n", inode);
-			ret = 0;
-		}
-		if (ret <= 0) {
-			if (got)
-				ceph_put_cap_refs(ci, got);
-			while (!list_empty(page_list)) {
-				page = lru_to_page(page_list);
-				list_del(&page->lru);
-				put_page(page);
-			}
-			return ret;
-		}
-	}
-
-	off = (u64) page_offset(page);
-
-	/* count pages */
-	next_index = page->index;
-	list_for_each_entry_reverse(page, page_list, lru) {
-		if (page->index != next_index)
-			break;
-		nr_pages++;
-		next_index++;
-		if (max && nr_pages == max)
-			break;
-	}
-	len = nr_pages << PAGE_SHIFT;
-	dout("start_read %p nr_pages %d is %lld~%lld\n", inode, nr_pages,
-	     off, len);
-	vino = ceph_vino(inode);
-	req = ceph_osdc_new_request(osdc, &ci->i_layout, vino, off, &len,
-				    0, 1, CEPH_OSD_OP_READ,
-				    CEPH_OSD_FLAG_READ, NULL,
-				    ci->i_truncate_seq, ci->i_truncate_size,
-				    false);
-	if (IS_ERR(req)) {
-		ret = PTR_ERR(req);
-		goto out;
-	}
-
-	/* build page vector */
-	nr_pages = calc_pages_for(0, len);
-	pages = kmalloc_array(nr_pages, sizeof(*pages), GFP_KERNEL);
-	if (!pages) {
-		ret = -ENOMEM;
-		goto out_put;
-	}
-	for (i = 0; i < nr_pages; ++i) {
-		page = list_entry(page_list->prev, struct page, lru);
-		BUG_ON(PageLocked(page));
-		list_del(&page->lru);
-
- 		dout("start_read %p adding %p idx %lu\n", inode, page,
-		     page->index);
-		if (add_to_page_cache_lru(page, &inode->i_data, page->index,
-					  GFP_KERNEL)) {
-			put_page(page);
-			dout("start_read %p add_to_page_cache failed %p\n",
-			     inode, page);
-			nr_pages = i;
-			if (nr_pages > 0) {
-				len = nr_pages << PAGE_SHIFT;
-				osd_req_op_extent_update(req, 0, len);
-				break;
-			}
-			goto out_pages;
-		}
-		pages[i] = page;
-	}
-	osd_req_op_extent_osd_data_pages(req, 0, pages, len, 0, false, false);
-	req->r_callback = finish_read;
-	req->r_inode = inode;
-
-	dout("start_read %p starting %p %lld~%lld\n", inode, req, off, len);
-	ret = ceph_osdc_start_request(osdc, req, false);
-	if (ret < 0)
-		goto out_pages;
-	ceph_osdc_put_request(req);
+	int got = (int)(uintptr_t)priv;
 
-	/* After adding locked pages to page cache, the inode holds cache cap.
-	 * So we can drop our cap refs. */
 	if (got)
 		ceph_put_cap_refs(ci, got);
-
-	return nr_pages;
-
-out_pages:
-	for (i = 0; i < nr_pages; ++i)
-		unlock_page(pages[i]);
-	ceph_put_page_vector(pages, nr_pages, false);
-out_put:
-	ceph_osdc_put_request(req);
-out:
-	if (got)
-		ceph_put_cap_refs(ci, got);
-	return ret;
 }
+const struct netfs_read_request_ops ceph_readahead_netfs_ops = {
+	.init_rreq		= ceph_init_rreq,
+	.is_cache_enabled	= ceph_is_cache_enabled,
+	.begin_cache_operation	= ceph_begin_cache_operation,
+	.issue_op		= ceph_netfs_issue_op,
+	.clamp_length		= ceph_netfs_clamp_length,
+	.cleanup		= ceph_readahead_cleanup,
+};
 
-
-/*
- * Read multiple pages.  Leave pages we don't read + unlock in page_list;
- * the caller (VM) cleans them up.
- */
-static int ceph_readpages(struct file *file, struct address_space *mapping,
-			  struct list_head *page_list, unsigned nr_pages)
+static void ceph_readahead(struct readahead_control *ractl)
 {
-	struct inode *inode = file_inode(file);
-	struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
-	struct ceph_file_info *fi = file->private_data;
+	struct inode *inode = file_inode(ractl->file);
+	struct ceph_file_info *fi = ractl->file->private_data;
 	struct ceph_rw_context *rw_ctx;
-	int rc = 0;
-	int max = 0;
+	int got = 0;
+	int ret = 0;
 
 	if (ceph_inode(inode)->i_inline_version != CEPH_INLINE_NONE)
-		return -EINVAL;
+		return;
 
 	rw_ctx = ceph_find_rw_context(fi);
-	max = fsc->mount_options->rsize >> PAGE_SHIFT;
-	dout("readpages %p file %p ctx %p nr_pages %d max %d\n",
-	     inode, file, rw_ctx, nr_pages, max);
-	while (!list_empty(page_list)) {
-		rc = start_read(inode, rw_ctx, page_list, max);
-		if (rc < 0)
-			goto out;
+	if (!rw_ctx) {
+		/*
+		 * readahead callers do not necessarily hold Fcb caps
+		 * (e.g. fadvise, madvise).
+		 */
+		int want = CEPH_CAP_FILE_CACHE;
+
+		ret = ceph_try_get_caps(inode, CEPH_CAP_FILE_RD, want, true, &got);
+		if (ret < 0)
+			dout("start_read %p, error getting cap\n", inode);
+		else if (!(got & want))
+			dout("start_read %p, no cache cap\n", inode);
+
+		if (ret <= 0)
+			return;
 	}
-out:
-	dout("readpages %p file %p ret %d\n", inode, file, rc);
-	return rc;
+	netfs_readahead(ractl, &ceph_readahead_netfs_ops, (void *)(uintptr_t)got);
 }
 
 struct ceph_writeback_ctl
@@ -1482,7 +1321,7 @@ static ssize_t ceph_direct_io(struct kiocb *iocb, struct iov_iter *iter)
 
 const struct address_space_operations ceph_aops = {
 	.readpage = ceph_readpage,
-	.readpages = ceph_readpages,
+	.readahead = ceph_readahead,
 	.writepage = ceph_writepage,
 	.writepages = ceph_writepages_start,
 	.write_begin = ceph_write_begin,

Re: [PATCH 00/33] Network fs helper library & fscache kiocb API [ver #3]

[Jeff Layton]

On Mon, 2021-02-15 at 15:44 +0000, David Howells wrote:
> Here's a set of patches to do two things:
> 
>  (1) Add a helper library to handle the new VM readahead interface.  This
>      is intended to be used unconditionally by the filesystem (whether or
>      not caching is enabled) and provides a common framework for doing
>      caching, transparent huge pages and, in the future, possibly fscrypt
>      and read bandwidth maximisation.  It also allows the netfs and the
>      cache to align, expand and slice up a read request from the VM in
>      various ways; the netfs need only provide a function to read a stretch
>      of data to the pagecache and the helper takes care of the rest.
> 
>  (2) Add an alternative fscache/cachfiles I/O API that uses the kiocb
>      facility to do async DIO to transfer data to/from the netfs's pages,
>      rather than using readpage with wait queue snooping on one side and
>      vfs_write() on the other.  It also uses less memory, since it doesn't
>      do buffered I/O on the backing file.
> 
>      Note that this uses SEEK_HOLE/SEEK_DATA to locate the data available
>      to be read from the cache.  Whilst this is an improvement from the
>      bmap interface, it still has a problem with regard to a modern
>      extent-based filesystem inserting or removing bridging blocks of
>      zeros.  Fixing that requires a much greater overhaul.
> 
> This is a step towards overhauling the fscache API.  The change is opt-in
> on the part of the network filesystem.  A netfs should not try to mix the
> old and the new API because of conflicting ways of handling pages and the
> PG_fscache page flag and because it would be mixing DIO with buffered I/O.
> Further, the helper library can't be used with the old API.
> 
> This does not change any of the fscache cookie handling APIs or the way
> invalidation is done.
> 
> In the near term, I intend to deprecate and remove the old I/O API
> (fscache_allocate_page{,s}(), fscache_read_or_alloc_page{,s}(),
> fscache_write_page() and fscache_uncache_page()) and eventually replace
> most of fscache/cachefiles with something simpler and easier to follow.
> 
> The patchset contains five parts:
> 
>  (1) Some helper patches, including provision of an ITER_XARRAY iov
>      iterator and a function to do readahead expansion.
> 
>  (2) Patches to add the netfs helper library.
> 
>  (3) A patch to add the fscache/cachefiles kiocb API.
> 
>  (4) Patches to add support in AFS for this.
> 
>  (5) Patches from Jeff Layton to add support in Ceph for this.
> 
> Dave Wysochanski also has patches for NFS for this, though they're not
> included on this branch as there's an issue with PNFS.
> 
> With this, AFS without a cache passes all expected xfstests; with a cache,
> there's an extra failure, but that's also there before these patches.
> Fixing that probably requires a greater overhaul.  Ceph and NFS also pass
> the expected tests.
> 
> These patches can be found also on:
> 
> 	https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=fscache-netfs-lib
> 
> For diffing reference, the tag for the 9th Feb pull request is
> fscache-ioapi-20210203 and can be found in the same repository.
> 
> 
> 
> Changes
> =======
> 
>  (v3) Rolled in the bug fixes.
> 
>       Adjusted the functions that unlock and wait for PG_fscache according
>       to Linus's suggestion.
> 
>       Hold a ref on a page when PG_fscache is set as per Linus's
>       suggestion.
> 
>       Dropped NFS support and added Ceph support.
> 
>  (v2) Fixed some bugs and added NFS support.
> 
> 
> References
> ==========
> 
> These patches have been published for review before, firstly as part of a
> larger set:
> 
> Link: https://lore.kernel.org/linux-fsdevel/158861203563.340223.7585359869938129395.stgit@warthog.procyon.org.uk/
> 
> Link: https://lore.kernel.org/linux-fsdevel/159465766378.1376105.11619976251039287525.stgit@warthog.procyon.org.uk/
> Link: https://lore.kernel.org/linux-fsdevel/159465784033.1376674.18106463693989811037.stgit@warthog.procyon.org.uk/
> Link: https://lore.kernel.org/linux-fsdevel/159465821598.1377938.2046362270225008168.stgit@warthog.procyon.org.uk/
> 
> Link: https://lore.kernel.org/linux-fsdevel/160588455242.3465195.3214733858273019178.stgit@warthog.procyon.org.uk/
> 
> Then as a cut-down set:
> 
> Link: https://lore.kernel.org/linux-fsdevel/161118128472.1232039.11746799833066425131.stgit@warthog.procyon.org.uk/
> 
> Link: https://lore.kernel.org/linux-fsdevel/161161025063.2537118.2009249444682241405.stgit@warthog.procyon.org.uk/
> 
> 
> Proposals/information about the design has been published here:
> 
> Link: https://lore.kernel.org/lkml/24942.1573667720@warthog.procyon.org.uk/
> Link: https://lore.kernel.org/linux-fsdevel/2758811.1610621106@warthog.procyon.org.uk/
> Link: https://lore.kernel.org/linux-fsdevel/1441311.1598547738@warthog.procyon.org.uk/
> Link: https://lore.kernel.org/linux-fsdevel/160655.1611012999@warthog.procyon.org.uk/
> 
> And requests for information:
> 
> Link: https://lore.kernel.org/linux-fsdevel/3326.1579019665@warthog.procyon.org.uk/
> Link: https://lore.kernel.org/linux-fsdevel/4467.1579020509@warthog.procyon.org.uk/
> Link: https://lore.kernel.org/linux-fsdevel/3577430.1579705075@warthog.procyon.org.uk/
> 
> The NFS parts, though not included here, have been tested by someone who's
> using fscache in production:
> 
> Link: https://listman.redhat.com/archives/linux-cachefs/2020-December/msg00000.html
> 
> I've posted partial patches to try and help 9p and cifs along:
> 
> Link: https://lore.kernel.org/linux-fsdevel/1514086.1605697347@warthog.procyon.org.uk/
> Link: https://lore.kernel.org/linux-cifs/1794123.1605713481@warthog.procyon.org.uk/
> Link: https://lore.kernel.org/linux-fsdevel/241017.1612263863@warthog.procyon.org.uk/
> Link: https://lore.kernel.org/linux-cifs/270998.1612265397@warthog.procyon.org.uk/
> 
> David
> ---
> David Howells (27):
>       iov_iter: Add ITER_XARRAY
>       mm: Add an unlock function for PG_private_2/PG_fscache
>       mm: Implement readahead_control pageset expansion
>       vfs: Export rw_verify_area() for use by cachefiles
>       netfs: Make a netfs helper module
>       netfs, mm: Move PG_fscache helper funcs to linux/netfs.h
>       netfs, mm: Add unlock_page_fscache() and wait_on_page_fscache()
>       netfs: Provide readahead and readpage netfs helpers
>       netfs: Add tracepoints
>       netfs: Gather stats
>       netfs: Add write_begin helper
>       netfs: Define an interface to talk to a cache
>       netfs: Hold a ref on a page when PG_private_2 is set
>       fscache, cachefiles: Add alternate API to use kiocb for read/write to cache
>       afs: Disable use of the fscache I/O routines
>       afs: Pass page into dirty region helpers to provide THP size
>       afs: Print the operation debug_id when logging an unexpected data version
>       afs: Move key to afs_read struct
>       afs: Don't truncate iter during data fetch
>       afs: Log remote unmarshalling errors
>       afs: Set up the iov_iter before calling afs_extract_data()
>       afs: Use ITER_XARRAY for writing
>       afs: Wait on PG_fscache before modifying/releasing a page
>       afs: Extract writeback extension into its own function
>       afs: Prepare for use of THPs
>       afs: Use the fs operation ops to handle FetchData completion
>       afs: Use new fscache read helper API
> 
> Jeff Layton (6):
>       ceph: disable old fscache readpage handling
>       ceph: rework PageFsCache handling
>       ceph: fix fscache invalidation
>       ceph: convert readpage to fscache read helper
>       ceph: plug write_begin into read helper
>       ceph: convert ceph_readpages to ceph_readahead
> 
> 
>  fs/Kconfig                    |    1 +
>  fs/Makefile                   |    1 +
>  fs/afs/Kconfig                |    1 +
>  fs/afs/dir.c                  |  225 ++++---
>  fs/afs/file.c                 |  470 ++++---------
>  fs/afs/fs_operation.c         |    4 +-
>  fs/afs/fsclient.c             |  108 +--
>  fs/afs/inode.c                |    7 +-
>  fs/afs/internal.h             |   58 +-
>  fs/afs/rxrpc.c                |  150 ++---
>  fs/afs/write.c                |  610 +++++++++--------
>  fs/afs/yfsclient.c            |   82 +--
>  fs/cachefiles/Makefile        |    1 +
>  fs/cachefiles/interface.c     |    5 +-
>  fs/cachefiles/internal.h      |    9 +
>  fs/cachefiles/rdwr2.c         |  412 ++++++++++++
>  fs/ceph/Kconfig               |    1 +
>  fs/ceph/addr.c                |  535 ++++++---------
>  fs/ceph/cache.c               |  125 ----
>  fs/ceph/cache.h               |  101 +--
>  fs/ceph/caps.c                |   10 +-
>  fs/ceph/inode.c               |    1 +
>  fs/ceph/super.h               |    1 +
>  fs/fscache/Kconfig            |    1 +
>  fs/fscache/Makefile           |    3 +-
>  fs/fscache/internal.h         |    3 +
>  fs/fscache/page.c             |    2 +-
>  fs/fscache/page2.c            |  117 ++++
>  fs/fscache/stats.c            |    1 +
>  fs/internal.h                 |    5 -
>  fs/netfs/Kconfig              |   23 +
>  fs/netfs/Makefile             |    5 +
>  fs/netfs/internal.h           |   97 +++
>  fs/netfs/read_helper.c        | 1169 +++++++++++++++++++++++++++++++++
>  fs/netfs/stats.c              |   59 ++
>  fs/read_write.c               |    1 +
>  include/linux/fs.h            |    1 +
>  include/linux/fscache-cache.h |    4 +
>  include/linux/fscache.h       |   40 +-
>  include/linux/netfs.h         |  195 ++++++
>  include/linux/pagemap.h       |    3 +
>  include/net/af_rxrpc.h        |    2 +-
>  include/trace/events/afs.h    |   74 +--
>  include/trace/events/netfs.h  |  201 ++++++
>  mm/filemap.c                  |   20 +
>  mm/readahead.c                |   70 ++
>  net/rxrpc/recvmsg.c           |    9 +-
>  47 files changed, 3473 insertions(+), 1550 deletions(-)
>  create mode 100644 fs/cachefiles/rdwr2.c
>  create mode 100644 fs/fscache/page2.c
>  create mode 100644 fs/netfs/Kconfig
>  create mode 100644 fs/netfs/Makefile
>  create mode 100644 fs/netfs/internal.h
>  create mode 100644 fs/netfs/read_helper.c
>  create mode 100644 fs/netfs/stats.c
>  create mode 100644 include/linux/netfs.h
>  create mode 100644 include/trace/events/netfs.h
> 
> 

Thanks David,

I did an xfstests run on ceph with a kernel based on this and it seemed
to do fine. I'll plan to pull this into the ceph-client/testing branch
and run it through the ceph kclient test harness. There are only a few
differences from the last run we did, so I'm not expecting big changes,
but I'll keep you posted.

-- 
Jeff Layton <jlayton@redhat.com>

Re: [PATCH 00/33] Network fs helper library & fscache kiocb API [ver #3]

[Jeff Layton]

On Mon, 2021-02-15 at 15:44 +0000, David Howells wrote:
> Here's a set of patches to do two things:
> 
>  (1) Add a helper library to handle the new VM readahead interface.  This
>      is intended to be used unconditionally by the filesystem (whether or
>      not caching is enabled) and provides a common framework for doing
>      caching, transparent huge pages and, in the future, possibly fscrypt
>      and read bandwidth maximisation.  It also allows the netfs and the
>      cache to align, expand and slice up a read request from the VM in
>      various ways; the netfs need only provide a function to read a stretch
>      of data to the pagecache and the helper takes care of the rest.
> 
>  (2) Add an alternative fscache/cachfiles I/O API that uses the kiocb
>      facility to do async DIO to transfer data to/from the netfs's pages,
>      rather than using readpage with wait queue snooping on one side and
>      vfs_write() on the other.  It also uses less memory, since it doesn't
>      do buffered I/O on the backing file.
> 
>      Note that this uses SEEK_HOLE/SEEK_DATA to locate the data available
>      to be read from the cache.  Whilst this is an improvement from the
>      bmap interface, it still has a problem with regard to a modern
>      extent-based filesystem inserting or removing bridging blocks of
>      zeros.  Fixing that requires a much greater overhaul.
> 
> This is a step towards overhauling the fscache API.  The change is opt-in
> on the part of the network filesystem.  A netfs should not try to mix the
> old and the new API because of conflicting ways of handling pages and the
> PG_fscache page flag and because it would be mixing DIO with buffered I/O.
> Further, the helper library can't be used with the old API.
> 
> This does not change any of the fscache cookie handling APIs or the way
> invalidation is done.
> 
> In the near term, I intend to deprecate and remove the old I/O API
> (fscache_allocate_page{,s}(), fscache_read_or_alloc_page{,s}(),
> fscache_write_page() and fscache_uncache_page()) and eventually replace
> most of fscache/cachefiles with something simpler and easier to follow.
> 
> The patchset contains five parts:
> 
>  (1) Some helper patches, including provision of an ITER_XARRAY iov
>      iterator and a function to do readahead expansion.
> 
>  (2) Patches to add the netfs helper library.
> 
>  (3) A patch to add the fscache/cachefiles kiocb API.
> 
>  (4) Patches to add support in AFS for this.
> 
>  (5) Patches from Jeff Layton to add support in Ceph for this.
> 
> Dave Wysochanski also has patches for NFS for this, though they're not
> included on this branch as there's an issue with PNFS.
> 
> With this, AFS without a cache passes all expected xfstests; with a cache,
> there's an extra failure, but that's also there before these patches.
> Fixing that probably requires a greater overhaul.  Ceph and NFS also pass
> the expected tests.
> 
> These patches can be found also on:
> 
> 	https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=fscache-netfs-lib
> 
> For diffing reference, the tag for the 9th Feb pull request is
> fscache-ioapi-20210203 and can be found in the same repository.
> 
> 
> 
> Changes
> =======
> 
>  (v3) Rolled in the bug fixes.
> 
>       Adjusted the functions that unlock and wait for PG_fscache according
>       to Linus's suggestion.
> 
>       Hold a ref on a page when PG_fscache is set as per Linus's
>       suggestion.
> 
>       Dropped NFS support and added Ceph support.
> 
>  (v2) Fixed some bugs and added NFS support.
> 
> 
> References
> ==========
> 
> These patches have been published for review before, firstly as part of a
> larger set:
> 
> Link: https://lore.kernel.org/linux-fsdevel/158861203563.340223.7585359869938129395.stgit@warthog.procyon.org.uk/
> 
> Link: https://lore.kernel.org/linux-fsdevel/159465766378.1376105.11619976251039287525.stgit@warthog.procyon.org.uk/
> Link: https://lore.kernel.org/linux-fsdevel/159465784033.1376674.18106463693989811037.stgit@warthog.procyon.org.uk/
> Link: https://lore.kernel.org/linux-fsdevel/159465821598.1377938.2046362270225008168.stgit@warthog.procyon.org.uk/
> 
> Link: https://lore.kernel.org/linux-fsdevel/160588455242.3465195.3214733858273019178.stgit@warthog.procyon.org.uk/
> 
> Then as a cut-down set:
> 
> Link: https://lore.kernel.org/linux-fsdevel/161118128472.1232039.11746799833066425131.stgit@warthog.procyon.org.uk/
> 
> Link: https://lore.kernel.org/linux-fsdevel/161161025063.2537118.2009249444682241405.stgit@warthog.procyon.org.uk/
> 
> 
> Proposals/information about the design has been published here:
> 
> Link: https://lore.kernel.org/lkml/24942.1573667720@warthog.procyon.org.uk/
> Link: https://lore.kernel.org/linux-fsdevel/2758811.1610621106@warthog.procyon.org.uk/
> Link: https://lore.kernel.org/linux-fsdevel/1441311.1598547738@warthog.procyon.org.uk/
> Link: https://lore.kernel.org/linux-fsdevel/160655.1611012999@warthog.procyon.org.uk/
> 
> And requests for information:
> 
> Link: https://lore.kernel.org/linux-fsdevel/3326.1579019665@warthog.procyon.org.uk/
> Link: https://lore.kernel.org/linux-fsdevel/4467.1579020509@warthog.procyon.org.uk/
> Link: https://lore.kernel.org/linux-fsdevel/3577430.1579705075@warthog.procyon.org.uk/
> 
> The NFS parts, though not included here, have been tested by someone who's
> using fscache in production:
> 
> Link: https://listman.redhat.com/archives/linux-cachefs/2020-December/msg00000.html
> 
> I've posted partial patches to try and help 9p and cifs along:
> 
> Link: https://lore.kernel.org/linux-fsdevel/1514086.1605697347@warthog.procyon.org.uk/
> Link: https://lore.kernel.org/linux-cifs/1794123.1605713481@warthog.procyon.org.uk/
> Link: https://lore.kernel.org/linux-fsdevel/241017.1612263863@warthog.procyon.org.uk/
> Link: https://lore.kernel.org/linux-cifs/270998.1612265397@warthog.procyon.org.uk/
> 
> David
> ---
> David Howells (27):
>       iov_iter: Add ITER_XARRAY
>       mm: Add an unlock function for PG_private_2/PG_fscache
>       mm: Implement readahead_control pageset expansion
>       vfs: Export rw_verify_area() for use by cachefiles
>       netfs: Make a netfs helper module
>       netfs, mm: Move PG_fscache helper funcs to linux/netfs.h
>       netfs, mm: Add unlock_page_fscache() and wait_on_page_fscache()
>       netfs: Provide readahead and readpage netfs helpers
>       netfs: Add tracepoints
>       netfs: Gather stats
>       netfs: Add write_begin helper
>       netfs: Define an interface to talk to a cache
>       netfs: Hold a ref on a page when PG_private_2 is set
>       fscache, cachefiles: Add alternate API to use kiocb for read/write to cache
>       afs: Disable use of the fscache I/O routines
>       afs: Pass page into dirty region helpers to provide THP size
>       afs: Print the operation debug_id when logging an unexpected data version
>       afs: Move key to afs_read struct
>       afs: Don't truncate iter during data fetch
>       afs: Log remote unmarshalling errors
>       afs: Set up the iov_iter before calling afs_extract_data()
>       afs: Use ITER_XARRAY for writing
>       afs: Wait on PG_fscache before modifying/releasing a page
>       afs: Extract writeback extension into its own function
>       afs: Prepare for use of THPs
>       afs: Use the fs operation ops to handle FetchData completion
>       afs: Use new fscache read helper API
> 
> Jeff Layton (6):
>       ceph: disable old fscache readpage handling
>       ceph: rework PageFsCache handling
>       ceph: fix fscache invalidation
>       ceph: convert readpage to fscache read helper
>       ceph: plug write_begin into read helper
>       ceph: convert ceph_readpages to ceph_readahead
> 
> 
>  fs/Kconfig                    |    1 +
>  fs/Makefile                   |    1 +
>  fs/afs/Kconfig                |    1 +
>  fs/afs/dir.c                  |  225 ++++---
>  fs/afs/file.c                 |  470 ++++---------
>  fs/afs/fs_operation.c         |    4 +-
>  fs/afs/fsclient.c             |  108 +--
>  fs/afs/inode.c                |    7 +-
>  fs/afs/internal.h             |   58 +-
>  fs/afs/rxrpc.c                |  150 ++---
>  fs/afs/write.c                |  610 +++++++++--------
>  fs/afs/yfsclient.c            |   82 +--
>  fs/cachefiles/Makefile        |    1 +
>  fs/cachefiles/interface.c     |    5 +-
>  fs/cachefiles/internal.h      |    9 +
>  fs/cachefiles/rdwr2.c         |  412 ++++++++++++
>  fs/ceph/Kconfig               |    1 +
>  fs/ceph/addr.c                |  535 ++++++---------
>  fs/ceph/cache.c               |  125 ----
>  fs/ceph/cache.h               |  101 +--
>  fs/ceph/caps.c                |   10 +-
>  fs/ceph/inode.c               |    1 +
>  fs/ceph/super.h               |    1 +
>  fs/fscache/Kconfig            |    1 +
>  fs/fscache/Makefile           |    3 +-
>  fs/fscache/internal.h         |    3 +
>  fs/fscache/page.c             |    2 +-
>  fs/fscache/page2.c            |  117 ++++
>  fs/fscache/stats.c            |    1 +
>  fs/internal.h                 |    5 -
>  fs/netfs/Kconfig              |   23 +
>  fs/netfs/Makefile             |    5 +
>  fs/netfs/internal.h           |   97 +++
>  fs/netfs/read_helper.c        | 1169 +++++++++++++++++++++++++++++++++
>  fs/netfs/stats.c              |   59 ++
>  fs/read_write.c               |    1 +
>  include/linux/fs.h            |    1 +
>  include/linux/fscache-cache.h |    4 +
>  include/linux/fscache.h       |   40 +-
>  include/linux/netfs.h         |  195 ++++++
>  include/linux/pagemap.h       |    3 +
>  include/net/af_rxrpc.h        |    2 +-
>  include/trace/events/afs.h    |   74 +--
>  include/trace/events/netfs.h  |  201 ++++++
>  mm/filemap.c                  |   20 +
>  mm/readahead.c                |   70 ++
>  net/rxrpc/recvmsg.c           |    9 +-
>  47 files changed, 3473 insertions(+), 1550 deletions(-)
>  create mode 100644 fs/cachefiles/rdwr2.c
>  create mode 100644 fs/fscache/page2.c
>  create mode 100644 fs/netfs/Kconfig
>  create mode 100644 fs/netfs/Makefile
>  create mode 100644 fs/netfs/internal.h
>  create mode 100644 fs/netfs/read_helper.c
>  create mode 100644 fs/netfs/stats.c
>  create mode 100644 include/linux/netfs.h
>  create mode 100644 include/trace/events/netfs.h
> 
> 

Thanks David,

I did an xfstests run on ceph with a kernel based on this and it seemed
to do fine. I'll plan to pull this into the ceph-client/testing branch
and run it through the ceph kclient test harness. There are only a few
differences from the last run we did, so I'm not expecting big changes,
but I'll keep you posted.

-- 
Jeff Layton <jlayton@redhat.com>

[PATCH 34/33] netfs: Use in_interrupt() not in_softirq()

[David Howells]

The in_softirq() in netfs_rreq_terminated() works fine for the cache being
on a normal disk, as the completion handlers may get called in softirq
context, but for an NVMe drive, the completion handler may get called in
IRQ context.

Fix to use in_interrupt() instead of in_softirq() throughout the read
helpers, particularly when deciding whether to punt code that might sleep
off to a worker thread.

The symptom involves warnings like the following appearing and the kernel
hanging:

 WARNING: CPU: 0 PID: 0 at kernel/softirq.c:175 __local_bh_enable_ip+0x35/0x50
 ...
 RIP: 0010:__local_bh_enable_ip+0x35/0x50
 ...
 Call Trace:
  <IRQ>
  rxrpc_kernel_begin_call+0x7d/0x1b0 [rxrpc]
  ? afs_rx_new_call+0x40/0x40 [kafs]
  ? afs_alloc_call+0x28/0x120 [kafs]
  afs_make_call+0x120/0x510 [kafs]
  ? afs_rx_new_call+0x40/0x40 [kafs]
  ? afs_alloc_flat_call+0xba/0x100 [kafs]
  ? __kmalloc+0x167/0x2f0
  ? afs_alloc_flat_call+0x9b/0x100 [kafs]
  afs_wait_for_operation+0x2d/0x200 [kafs]
  afs_do_sync_operation+0x16/0x20 [kafs]
  afs_req_issue_op+0x8c/0xb0 [kafs]
  netfs_rreq_assess+0x125/0x7d0 [netfs]
  ? cachefiles_end_operation+0x40/0x40 [cachefiles]
  netfs_subreq_terminated+0x117/0x220 [netfs]
  cachefiles_read_complete+0x21/0x60 [cachefiles]
  iomap_dio_bio_end_io+0xdd/0x110
  blk_update_request+0x20a/0x380
  blk_mq_end_request+0x1c/0x120
  nvme_process_cq+0x159/0x1f0 [nvme]
  nvme_irq+0x10/0x20 [nvme]
  __handle_irq_event_percpu+0x37/0x150
  handle_irq_event+0x49/0xb0
  handle_edge_irq+0x7c/0x200
  asm_call_irq_on_stack+0xf/0x20
  </IRQ>
  common_interrupt+0xad/0x120
  asm_common_interrupt+0x1e/0x40
 ...

Reported-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Matthew Wilcox <willy@infradead.org>
cc: linux-mm@kvack.org
cc: linux-cachefs@redhat.com
cc: linux-afs@lists.infradead.org
cc: linux-nfs@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: ceph-devel@vger.kernel.org
cc: v9fs-developer@lists.sourceforge.net
cc: linux-fsdevel@vger.kernel.org
---
 read_helper.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c
index 9191a3617d91..db582008b4bd 100644
--- a/fs/netfs/read_helper.c
+++ b/fs/netfs/read_helper.c
@@ -96,7 +96,7 @@ static void netfs_free_read_request(struct work_struct *work)
 static void netfs_put_read_request(struct netfs_read_request *rreq)
 {
 	if (refcount_dec_and_test(&rreq->usage)) {
-		if (in_softirq()) {
+		if (in_interrupt()) {
 			rreq->work.func = netfs_free_read_request;
 			if (!queue_work(system_unbound_wq, &rreq->work))
 				BUG();
@@ -353,7 +353,7 @@ static void netfs_rreq_write_to_cache_work(struct work_struct *work)
 
 static void netfs_rreq_write_to_cache(struct netfs_read_request *rreq)
 {
-	if (in_softirq()) {
+	if (in_interrupt()) {
 		rreq->work.func = netfs_rreq_write_to_cache_work;
 		if (!queue_work(system_unbound_wq, &rreq->work))
 			BUG();
@@ -479,7 +479,7 @@ static bool netfs_rreq_perform_resubmissions(struct netfs_read_request *rreq)
 {
 	struct netfs_read_subrequest *subreq;
 
-	WARN_ON(in_softirq());
+	WARN_ON(in_interrupt());
 
 	trace_netfs_rreq(rreq, netfs_rreq_trace_resubmit);
 
@@ -577,7 +577,7 @@ static void netfs_rreq_work(struct work_struct *work)
 static void netfs_rreq_terminated(struct netfs_read_request *rreq)
 {
 	if (test_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags) &&
-	    in_softirq()) {
+	    in_interrupt()) {
 		if (!queue_work(system_unbound_wq, &rreq->work))
 			BUG();
 	} else {

Re: [PATCH 00/33] Network fs helper library & fscache kiocb API [ver #3]

[Steve French]

Jeff,
What are the performance differences you are seeing (positive or
negative) with ceph and netfs, especially with simple examples like
file copy or grep of large files?

It could be good if netfs simplifies the problem experienced by
network filesystems on Linux with readahead on large sequential reads
- where we don't get as much parallelism due to only having one
readahead request at a time (thus in many cases there is 'dead time'
on either the network or the file server while waiting for the next
readpages request to be issued).   This can be a significant
performance problem for current readpages when network latency is long
(or e.g. in cases when network encryption is enabled, and hardware
offload not available so time consuming on the server or client to
encrypt the packet).

Do you see netfs much faster than currentreadpages for ceph?

Have you been able to get much benefit from throttling readahead with
ceph from the current netfs approach for clamping i/o?

On Mon, Feb 15, 2021 at 12:08 PM Jeff Layton <jlayton@redhat.com> wrote:
>
> On Mon, 2021-02-15 at 15:44 +0000, David Howells wrote:
> > Here's a set of patches to do two things:
> >
> >  (1) Add a helper library to handle the new VM readahead interface.  This
> >      is intended to be used unconditionally by the filesystem (whether or
> >      not caching is enabled) and provides a common framework for doing
> >      caching, transparent huge pages and, in the future, possibly fscrypt
> >      and read bandwidth maximisation.  It also allows the netfs and the
> >      cache to align, expand and slice up a read request from the VM in
> >      various ways; the netfs need only provide a function to read a stretch
> >      of data to the pagecache and the helper takes care of the rest.
> >
> >  (2) Add an alternative fscache/cachfiles I/O API that uses the kiocb
> >      facility to do async DIO to transfer data to/from the netfs's pages,
> >      rather than using readpage with wait queue snooping on one side and
> >      vfs_write() on the other.  It also uses less memory, since it doesn't
> >      do buffered I/O on the backing file.
> >
> >      Note that this uses SEEK_HOLE/SEEK_DATA to locate the data available
> >      to be read from the cache.  Whilst this is an improvement from the
> >      bmap interface, it still has a problem with regard to a modern
> >      extent-based filesystem inserting or removing bridging blocks of
> >      zeros.  Fixing that requires a much greater overhaul.
> >
> > This is a step towards overhauling the fscache API.  The change is opt-in
> > on the part of the network filesystem.  A netfs should not try to mix the
> > old and the new API because of conflicting ways of handling pages and the
> > PG_fscache page flag and because it would be mixing DIO with buffered I/O.
> > Further, the helper library can't be used with the old API.
> >
> > This does not change any of the fscache cookie handling APIs or the way
> > invalidation is done.
> >
> > In the near term, I intend to deprecate and remove the old I/O API
> > (fscache_allocate_page{,s}(), fscache_read_or_alloc_page{,s}(),
> > fscache_write_page() and fscache_uncache_page()) and eventually replace
> > most of fscache/cachefiles with something simpler and easier to follow.
> >
> > The patchset contains five parts:
> >
> >  (1) Some helper patches, including provision of an ITER_XARRAY iov
> >      iterator and a function to do readahead expansion.
> >
> >  (2) Patches to add the netfs helper library.
> >
> >  (3) A patch to add the fscache/cachefiles kiocb API.
> >
> >  (4) Patches to add support in AFS for this.
> >
> >  (5) Patches from Jeff Layton to add support in Ceph for this.
> >
> > Dave Wysochanski also has patches for NFS for this, though they're not
> > included on this branch as there's an issue with PNFS.
> >
> > With this, AFS without a cache passes all expected xfstests; with a cache,
> > there's an extra failure, but that's also there before these patches.
> > Fixing that probably requires a greater overhaul.  Ceph and NFS also pass
> > the expected tests.
> >
> > These patches can be found also on:
> >
> >       https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=fscache-netfs-lib
> >
> > For diffing reference, the tag for the 9th Feb pull request is
> > fscache-ioapi-20210203 and can be found in the same repository.
> >
> >
> >
> > Changes
> > =======
> >
> >  (v3) Rolled in the bug fixes.
> >
> >       Adjusted the functions that unlock and wait for PG_fscache according
> >       to Linus's suggestion.
> >
> >       Hold a ref on a page when PG_fscache is set as per Linus's
> >       suggestion.
> >
> >       Dropped NFS support and added Ceph support.
> >
> >  (v2) Fixed some bugs and added NFS support.
> >
> >
> > References
> > ==========
> >
> > These patches have been published for review before, firstly as part of a
> > larger set:
> >
> > Link: https://lore.kernel.org/linux-fsdevel/158861203563.340223.7585359869938129395.stgit@warthog.procyon.org.uk/
> >
> > Link: https://lore.kernel.org/linux-fsdevel/159465766378.1376105.11619976251039287525.stgit@warthog.procyon.org.uk/
> > Link: https://lore.kernel.org/linux-fsdevel/159465784033.1376674.18106463693989811037.stgit@warthog.procyon.org.uk/
> > Link: https://lore.kernel.org/linux-fsdevel/159465821598.1377938.2046362270225008168.stgit@warthog.procyon.org.uk/
> >
> > Link: https://lore.kernel.org/linux-fsdevel/160588455242.3465195.3214733858273019178.stgit@warthog.procyon.org.uk/
> >
> > Then as a cut-down set:
> >
> > Link: https://lore.kernel.org/linux-fsdevel/161118128472.1232039.11746799833066425131.stgit@warthog.procyon.org.uk/
> >
> > Link: https://lore.kernel.org/linux-fsdevel/161161025063.2537118.2009249444682241405.stgit@warthog.procyon.org.uk/
> >
> >
> > Proposals/information about the design has been published here:
> >
> > Link: https://lore.kernel.org/lkml/24942.1573667720@warthog.procyon.org.uk/
> > Link: https://lore.kernel.org/linux-fsdevel/2758811.1610621106@warthog.procyon.org.uk/
> > Link: https://lore.kernel.org/linux-fsdevel/1441311.1598547738@warthog.procyon.org.uk/
> > Link: https://lore.kernel.org/linux-fsdevel/160655.1611012999@warthog.procyon.org.uk/
> >
> > And requests for information:
> >
> > Link: https://lore.kernel.org/linux-fsdevel/3326.1579019665@warthog.procyon.org.uk/
> > Link: https://lore.kernel.org/linux-fsdevel/4467.1579020509@warthog.procyon.org.uk/
> > Link: https://lore.kernel.org/linux-fsdevel/3577430.1579705075@warthog.procyon.org.uk/
> >
> > The NFS parts, though not included here, have been tested by someone who's
> > using fscache in production:
> >
> > Link: https://listman.redhat.com/archives/linux-cachefs/2020-December/msg00000.html
> >
> > I've posted partial patches to try and help 9p and cifs along:
> >
> > Link: https://lore.kernel.org/linux-fsdevel/1514086.1605697347@warthog.procyon.org.uk/
> > Link: https://lore.kernel.org/linux-cifs/1794123.1605713481@warthog.procyon.org.uk/
> > Link: https://lore.kernel.org/linux-fsdevel/241017.1612263863@warthog.procyon.org.uk/
> > Link: https://lore.kernel.org/linux-cifs/270998.1612265397@warthog.procyon.org.uk/
> >
> > David
> > ---
> > David Howells (27):
> >       iov_iter: Add ITER_XARRAY
> >       mm: Add an unlock function for PG_private_2/PG_fscache
> >       mm: Implement readahead_control pageset expansion
> >       vfs: Export rw_verify_area() for use by cachefiles
> >       netfs: Make a netfs helper module
> >       netfs, mm: Move PG_fscache helper funcs to linux/netfs.h
> >       netfs, mm: Add unlock_page_fscache() and wait_on_page_fscache()
> >       netfs: Provide readahead and readpage netfs helpers
> >       netfs: Add tracepoints
> >       netfs: Gather stats
> >       netfs: Add write_begin helper
> >       netfs: Define an interface to talk to a cache
> >       netfs: Hold a ref on a page when PG_private_2 is set
> >       fscache, cachefiles: Add alternate API to use kiocb for read/write to cache
> >       afs: Disable use of the fscache I/O routines
> >       afs: Pass page into dirty region helpers to provide THP size
> >       afs: Print the operation debug_id when logging an unexpected data version
> >       afs: Move key to afs_read struct
> >       afs: Don't truncate iter during data fetch
> >       afs: Log remote unmarshalling errors
> >       afs: Set up the iov_iter before calling afs_extract_data()
> >       afs: Use ITER_XARRAY for writing
> >       afs: Wait on PG_fscache before modifying/releasing a page
> >       afs: Extract writeback extension into its own function
> >       afs: Prepare for use of THPs
> >       afs: Use the fs operation ops to handle FetchData completion
> >       afs: Use new fscache read helper API
> >
> > Jeff Layton (6):
> >       ceph: disable old fscache readpage handling
> >       ceph: rework PageFsCache handling
> >       ceph: fix fscache invalidation
> >       ceph: convert readpage to fscache read helper
> >       ceph: plug write_begin into read helper
> >       ceph: convert ceph_readpages to ceph_readahead
> >
> >
> >  fs/Kconfig                    |    1 +
> >  fs/Makefile                   |    1 +
> >  fs/afs/Kconfig                |    1 +
> >  fs/afs/dir.c                  |  225 ++++---
> >  fs/afs/file.c                 |  470 ++++---------
> >  fs/afs/fs_operation.c         |    4 +-
> >  fs/afs/fsclient.c             |  108 +--
> >  fs/afs/inode.c                |    7 +-
> >  fs/afs/internal.h             |   58 +-
> >  fs/afs/rxrpc.c                |  150 ++---
> >  fs/afs/write.c                |  610 +++++++++--------
> >  fs/afs/yfsclient.c            |   82 +--
> >  fs/cachefiles/Makefile        |    1 +
> >  fs/cachefiles/interface.c     |    5 +-
> >  fs/cachefiles/internal.h      |    9 +
> >  fs/cachefiles/rdwr2.c         |  412 ++++++++++++
> >  fs/ceph/Kconfig               |    1 +
> >  fs/ceph/addr.c                |  535 ++++++---------
> >  fs/ceph/cache.c               |  125 ----
> >  fs/ceph/cache.h               |  101 +--
> >  fs/ceph/caps.c                |   10 +-
> >  fs/ceph/inode.c               |    1 +
> >  fs/ceph/super.h               |    1 +
> >  fs/fscache/Kconfig            |    1 +
> >  fs/fscache/Makefile           |    3 +-
> >  fs/fscache/internal.h         |    3 +
> >  fs/fscache/page.c             |    2 +-
> >  fs/fscache/page2.c            |  117 ++++
> >  fs/fscache/stats.c            |    1 +
> >  fs/internal.h                 |    5 -
> >  fs/netfs/Kconfig              |   23 +
> >  fs/netfs/Makefile             |    5 +
> >  fs/netfs/internal.h           |   97 +++
> >  fs/netfs/read_helper.c        | 1169 +++++++++++++++++++++++++++++++++
> >  fs/netfs/stats.c              |   59 ++
> >  fs/read_write.c               |    1 +
> >  include/linux/fs.h            |    1 +
> >  include/linux/fscache-cache.h |    4 +
> >  include/linux/fscache.h       |   40 +-
> >  include/linux/netfs.h         |  195 ++++++
> >  include/linux/pagemap.h       |    3 +
> >  include/net/af_rxrpc.h        |    2 +-
> >  include/trace/events/afs.h    |   74 +--
> >  include/trace/events/netfs.h  |  201 ++++++
> >  mm/filemap.c                  |   20 +
> >  mm/readahead.c                |   70 ++
> >  net/rxrpc/recvmsg.c           |    9 +-
> >  47 files changed, 3473 insertions(+), 1550 deletions(-)
> >  create mode 100644 fs/cachefiles/rdwr2.c
> >  create mode 100644 fs/fscache/page2.c
> >  create mode 100644 fs/netfs/Kconfig
> >  create mode 100644 fs/netfs/Makefile
> >  create mode 100644 fs/netfs/internal.h
> >  create mode 100644 fs/netfs/read_helper.c
> >  create mode 100644 fs/netfs/stats.c
> >  create mode 100644 include/linux/netfs.h
> >  create mode 100644 include/trace/events/netfs.h
> >
> >
>
> Thanks David,
>
> I did an xfstests run on ceph with a kernel based on this and it seemed
> to do fine. I'll plan to pull this into the ceph-client/testing branch
> and run it through the ceph kclient test harness. There are only a few
> differences from the last run we did, so I'm not expecting big changes,
> but I'll keep you posted.
>
> --
> Jeff Layton <jlayton@redhat.com>
>


-- 
Thanks,

Steve

Re: [PATCH 00/33] Network fs helper library & fscache kiocb API [ver #3]

[Steve French]

Jeff,
What are the performance differences you are seeing (positive or
negative) with ceph and netfs, especially with simple examples like
file copy or grep of large files?

It could be good if netfs simplifies the problem experienced by
network filesystems on Linux with readahead on large sequential reads
- where we don't get as much parallelism due to only having one
readahead request at a time (thus in many cases there is 'dead time'
on either the network or the file server while waiting for the next
readpages request to be issued).   This can be a significant
performance problem for current readpages when network latency is long
(or e.g. in cases when network encryption is enabled, and hardware
offload not available so time consuming on the server or client to
encrypt the packet).

Do you see netfs much faster than currentreadpages for ceph?

Have you been able to get much benefit from throttling readahead with
ceph from the current netfs approach for clamping i/o?

On Mon, Feb 15, 2021 at 12:08 PM Jeff Layton <jlayton@redhat.com> wrote:
>
> On Mon, 2021-02-15 at 15:44 +0000, David Howells wrote:
> > Here's a set of patches to do two things:
> >
> >  (1) Add a helper library to handle the new VM readahead interface.  This
> >      is intended to be used unconditionally by the filesystem (whether or
> >      not caching is enabled) and provides a common framework for doing
> >      caching, transparent huge pages and, in the future, possibly fscrypt
> >      and read bandwidth maximisation.  It also allows the netfs and the
> >      cache to align, expand and slice up a read request from the VM in
> >      various ways; the netfs need only provide a function to read a stretch
> >      of data to the pagecache and the helper takes care of the rest.
> >
> >  (2) Add an alternative fscache/cachfiles I/O API that uses the kiocb
> >      facility to do async DIO to transfer data to/from the netfs's pages,
> >      rather than using readpage with wait queue snooping on one side and
> >      vfs_write() on the other.  It also uses less memory, since it doesn't
> >      do buffered I/O on the backing file.
> >
> >      Note that this uses SEEK_HOLE/SEEK_DATA to locate the data available
> >      to be read from the cache.  Whilst this is an improvement from the
> >      bmap interface, it still has a problem with regard to a modern
> >      extent-based filesystem inserting or removing bridging blocks of
> >      zeros.  Fixing that requires a much greater overhaul.
> >
> > This is a step towards overhauling the fscache API.  The change is opt-in
> > on the part of the network filesystem.  A netfs should not try to mix the
> > old and the new API because of conflicting ways of handling pages and the
> > PG_fscache page flag and because it would be mixing DIO with buffered I/O.
> > Further, the helper library can't be used with the old API.
> >
> > This does not change any of the fscache cookie handling APIs or the way
> > invalidation is done.
> >
> > In the near term, I intend to deprecate and remove the old I/O API
> > (fscache_allocate_page{,s}(), fscache_read_or_alloc_page{,s}(),
> > fscache_write_page() and fscache_uncache_page()) and eventually replace
> > most of fscache/cachefiles with something simpler and easier to follow.
> >
> > The patchset contains five parts:
> >
> >  (1) Some helper patches, including provision of an ITER_XARRAY iov
> >      iterator and a function to do readahead expansion.
> >
> >  (2) Patches to add the netfs helper library.
> >
> >  (3) A patch to add the fscache/cachefiles kiocb API.
> >
> >  (4) Patches to add support in AFS for this.
> >
> >  (5) Patches from Jeff Layton to add support in Ceph for this.
> >
> > Dave Wysochanski also has patches for NFS for this, though they're not
> > included on this branch as there's an issue with PNFS.
> >
> > With this, AFS without a cache passes all expected xfstests; with a cache,
> > there's an extra failure, but that's also there before these patches.
> > Fixing that probably requires a greater overhaul.  Ceph and NFS also pass
> > the expected tests.
> >
> > These patches can be found also on:
> >
> >       https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=fscache-netfs-lib
> >
> > For diffing reference, the tag for the 9th Feb pull request is
> > fscache-ioapi-20210203 and can be found in the same repository.
> >
> >
> >
> > Changes
> > =======
> >
> >  (v3) Rolled in the bug fixes.
> >
> >       Adjusted the functions that unlock and wait for PG_fscache according
> >       to Linus's suggestion.
> >
> >       Hold a ref on a page when PG_fscache is set as per Linus's
> >       suggestion.
> >
> >       Dropped NFS support and added Ceph support.
> >
> >  (v2) Fixed some bugs and added NFS support.
> >
> >
> > References
> > ==========
> >
> > These patches have been published for review before, firstly as part of a
> > larger set:
> >
> > Link: https://lore.kernel.org/linux-fsdevel/158861203563.340223.7585359869938129395.stgit@warthog.procyon.org.uk/
> >
> > Link: https://lore.kernel.org/linux-fsdevel/159465766378.1376105.11619976251039287525.stgit@warthog.procyon.org.uk/
> > Link: https://lore.kernel.org/linux-fsdevel/159465784033.1376674.18106463693989811037.stgit@warthog.procyon.org.uk/
> > Link: https://lore.kernel.org/linux-fsdevel/159465821598.1377938.2046362270225008168.stgit@warthog.procyon.org.uk/
> >
> > Link: https://lore.kernel.org/linux-fsdevel/160588455242.3465195.3214733858273019178.stgit@warthog.procyon.org.uk/
> >
> > Then as a cut-down set:
> >
> > Link: https://lore.kernel.org/linux-fsdevel/161118128472.1232039.11746799833066425131.stgit@warthog.procyon.org.uk/
> >
> > Link: https://lore.kernel.org/linux-fsdevel/161161025063.2537118.2009249444682241405.stgit@warthog.procyon.org.uk/
> >
> >
> > Proposals/information about the design has been published here:
> >
> > Link: https://lore.kernel.org/lkml/24942.1573667720@warthog.procyon.org.uk/
> > Link: https://lore.kernel.org/linux-fsdevel/2758811.1610621106@warthog.procyon.org.uk/
> > Link: https://lore.kernel.org/linux-fsdevel/1441311.1598547738@warthog.procyon.org.uk/
> > Link: https://lore.kernel.org/linux-fsdevel/160655.1611012999@warthog.procyon.org.uk/
> >
> > And requests for information:
> >
> > Link: https://lore.kernel.org/linux-fsdevel/3326.1579019665@warthog.procyon.org.uk/
> > Link: https://lore.kernel.org/linux-fsdevel/4467.1579020509@warthog.procyon.org.uk/
> > Link: https://lore.kernel.org/linux-fsdevel/3577430.1579705075@warthog.procyon.org.uk/
> >
> > The NFS parts, though not included here, have been tested by someone who's
> > using fscache in production:
> >
> > Link: https://listman.redhat.com/archives/linux-cachefs/2020-December/msg00000.html
> >
> > I've posted partial patches to try and help 9p and cifs along:
> >
> > Link: https://lore.kernel.org/linux-fsdevel/1514086.1605697347@warthog.procyon.org.uk/
> > Link: https://lore.kernel.org/linux-cifs/1794123.1605713481@warthog.procyon.org.uk/
> > Link: https://lore.kernel.org/linux-fsdevel/241017.1612263863@warthog.procyon.org.uk/
> > Link: https://lore.kernel.org/linux-cifs/270998.1612265397@warthog.procyon.org.uk/
> >
> > David
> > ---
> > David Howells (27):
> >       iov_iter: Add ITER_XARRAY
> >       mm: Add an unlock function for PG_private_2/PG_fscache
> >       mm: Implement readahead_control pageset expansion
> >       vfs: Export rw_verify_area() for use by cachefiles
> >       netfs: Make a netfs helper module
> >       netfs, mm: Move PG_fscache helper funcs to linux/netfs.h
> >       netfs, mm: Add unlock_page_fscache() and wait_on_page_fscache()
> >       netfs: Provide readahead and readpage netfs helpers
> >       netfs: Add tracepoints
> >       netfs: Gather stats
> >       netfs: Add write_begin helper
> >       netfs: Define an interface to talk to a cache
> >       netfs: Hold a ref on a page when PG_private_2 is set
> >       fscache, cachefiles: Add alternate API to use kiocb for read/write to cache
> >       afs: Disable use of the fscache I/O routines
> >       afs: Pass page into dirty region helpers to provide THP size
> >       afs: Print the operation debug_id when logging an unexpected data version
> >       afs: Move key to afs_read struct
> >       afs: Don't truncate iter during data fetch
> >       afs: Log remote unmarshalling errors
> >       afs: Set up the iov_iter before calling afs_extract_data()
> >       afs: Use ITER_XARRAY for writing
> >       afs: Wait on PG_fscache before modifying/releasing a page
> >       afs: Extract writeback extension into its own function
> >       afs: Prepare for use of THPs
> >       afs: Use the fs operation ops to handle FetchData completion
> >       afs: Use new fscache read helper API
> >
> > Jeff Layton (6):
> >       ceph: disable old fscache readpage handling
> >       ceph: rework PageFsCache handling
> >       ceph: fix fscache invalidation
> >       ceph: convert readpage to fscache read helper
> >       ceph: plug write_begin into read helper
> >       ceph: convert ceph_readpages to ceph_readahead
> >
> >
> >  fs/Kconfig                    |    1 +
> >  fs/Makefile                   |    1 +
> >  fs/afs/Kconfig                |    1 +
> >  fs/afs/dir.c                  |  225 ++++---
> >  fs/afs/file.c                 |  470 ++++---------
> >  fs/afs/fs_operation.c         |    4 +-
> >  fs/afs/fsclient.c             |  108 +--
> >  fs/afs/inode.c                |    7 +-
> >  fs/afs/internal.h             |   58 +-
> >  fs/afs/rxrpc.c                |  150 ++---
> >  fs/afs/write.c                |  610 +++++++++--------
> >  fs/afs/yfsclient.c            |   82 +--
> >  fs/cachefiles/Makefile        |    1 +
> >  fs/cachefiles/interface.c     |    5 +-
> >  fs/cachefiles/internal.h      |    9 +
> >  fs/cachefiles/rdwr2.c         |  412 ++++++++++++
> >  fs/ceph/Kconfig               |    1 +
> >  fs/ceph/addr.c                |  535 ++++++---------
> >  fs/ceph/cache.c               |  125 ----
> >  fs/ceph/cache.h               |  101 +--
> >  fs/ceph/caps.c                |   10 +-
> >  fs/ceph/inode.c               |    1 +
> >  fs/ceph/super.h               |    1 +
> >  fs/fscache/Kconfig            |    1 +
> >  fs/fscache/Makefile           |    3 +-
> >  fs/fscache/internal.h         |    3 +
> >  fs/fscache/page.c             |    2 +-
> >  fs/fscache/page2.c            |  117 ++++
> >  fs/fscache/stats.c            |    1 +
> >  fs/internal.h                 |    5 -
> >  fs/netfs/Kconfig              |   23 +
> >  fs/netfs/Makefile             |    5 +
> >  fs/netfs/internal.h           |   97 +++
> >  fs/netfs/read_helper.c        | 1169 +++++++++++++++++++++++++++++++++
> >  fs/netfs/stats.c              |   59 ++
> >  fs/read_write.c               |    1 +
> >  include/linux/fs.h            |    1 +
> >  include/linux/fscache-cache.h |    4 +
> >  include/linux/fscache.h       |   40 +-
> >  include/linux/netfs.h         |  195 ++++++
> >  include/linux/pagemap.h       |    3 +
> >  include/net/af_rxrpc.h        |    2 +-
> >  include/trace/events/afs.h    |   74 +--
> >  include/trace/events/netfs.h  |  201 ++++++
> >  mm/filemap.c                  |   20 +
> >  mm/readahead.c                |   70 ++
> >  net/rxrpc/recvmsg.c           |    9 +-
> >  47 files changed, 3473 insertions(+), 1550 deletions(-)
> >  create mode 100644 fs/cachefiles/rdwr2.c
> >  create mode 100644 fs/fscache/page2.c
> >  create mode 100644 fs/netfs/Kconfig
> >  create mode 100644 fs/netfs/Makefile
> >  create mode 100644 fs/netfs/internal.h
> >  create mode 100644 fs/netfs/read_helper.c
> >  create mode 100644 fs/netfs/stats.c
> >  create mode 100644 include/linux/netfs.h
> >  create mode 100644 include/trace/events/netfs.h
> >
> >
>
> Thanks David,
>
> I did an xfstests run on ceph with a kernel based on this and it seemed
> to do fine. I'll plan to pull this into the ceph-client/testing branch
> and run it through the ceph kclient test harness. There are only a few
> differences from the last run we did, so I'm not expecting big changes,
> but I'll keep you posted.
>
> --
> Jeff Layton <jlayton@redhat.com>
>


-- 
Thanks,

Steve

Re: [PATCH 00/33] Network fs helper library & fscache kiocb API [ver #3]

[Matthew Wilcox]

On Mon, Feb 15, 2021 at 06:40:27PM -0600, Steve French wrote:
> It could be good if netfs simplifies the problem experienced by
> network filesystems on Linux with readahead on large sequential reads
> - where we don't get as much parallelism due to only having one
> readahead request at a time (thus in many cases there is 'dead time'
> on either the network or the file server while waiting for the next
> readpages request to be issued).   This can be a significant
> performance problem for current readpages when network latency is long
> (or e.g. in cases when network encryption is enabled, and hardware
> offload not available so time consuming on the server or client to
> encrypt the packet).
> 
> Do you see netfs much faster than currentreadpages for ceph?
> 
> Have you been able to get much benefit from throttling readahead with
> ceph from the current netfs approach for clamping i/o?

The switch from readpages to readahead does help in a couple of corner
cases.  For example, if you have two processes reading the same file at
the same time, one will now block on the other (due to the page lock)
rather than submitting a mess of overlapping and partial reads.

We're not there yet on having multiple outstanding reads.  Bill and I
had a chat recently about how to make the readahead code detect that
it is in a "long fat pipe" situation (as opposed to just dealing with
a slow device), and submit extra readahead requests to make best use of
the bandwidth and minimise blocking of the application.

That's not something for the netfs code to do though; we can get into
that situation with highly parallel SSDs.

Re: [PATCH 00/33] Network fs helper library & fscache kiocb API [ver #3]

[Steve French]

On Mon, Feb 15, 2021 at 8:10 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Mon, Feb 15, 2021 at 06:40:27PM -0600, Steve French wrote:
> > It could be good if netfs simplifies the problem experienced by
> > network filesystems on Linux with readahead on large sequential reads
> > - where we don't get as much parallelism due to only having one
> > readahead request at a time (thus in many cases there is 'dead time'
> > on either the network or the file server while waiting for the next
> > readpages request to be issued).   This can be a significant
> > performance problem for current readpages when network latency is long
> > (or e.g. in cases when network encryption is enabled, and hardware
> > offload not available so time consuming on the server or client to
> > encrypt the packet).
> >
> > Do you see netfs much faster than currentreadpages for ceph?
> >
> > Have you been able to get much benefit from throttling readahead with
> > ceph from the current netfs approach for clamping i/o?
>
> The switch from readpages to readahead does help in a couple of corner
> cases.  For example, if you have two processes reading the same file at
> the same time, one will now block on the other (due to the page lock)
> rather than submitting a mess of overlapping and partial reads.
>
> We're not there yet on having multiple outstanding reads.  Bill and I
> had a chat recently about how to make the readahead code detect that
> it is in a "long fat pipe" situation (as opposed to just dealing with
> a slow device), and submit extra readahead requests to make best use of
> the bandwidth and minimise blocking of the application.
>
> That's not something for the netfs code to do though; we can get into
> that situation with highly parallel SSDs.

This (readahead behavior improvements in Linux, on single large file sequential
read workloads like cp or grep) gets particularly interesting
with SMB3 as multichannel becomes more common.  With one channel having
one readahead request pending on the network is suboptimal - but not as bad as
when multichannel is negotiated. Interestingly in most cases two
network connections
to the same server (different TCP sockets,but the same mount, even in
cases where
only network adapter) can achieve better performance - but still significantly
lags Windows (and probably other clients) as in Linux we don't keep
multiple I/Os
in flight at one time (unless different files are being read at the same time
by different threads).   As network adapters are added and removed from the
server (other client typically poll to detect interface changes, and SMB3
also leverages the "witness protocol" to get notification of adapter additions
or removals) - it would be helpful to change the maximum number of
readahead requests in flight.  In addition, as the server throttles back
(reducing the number of 'credits' granted to the client) it will be important
to give hints to the readahead logic about reducing the number of
read ahead requests in flight.   Keeping multiple readahead requests
is easier to imagine when multiple processes are copying or reading
files, but there are many scenarios where we could do better with parallelizing
a single process doing copy by ensuring that there is no 'dead time' on
the network.


-- 
Thanks,

Steve

Re: [PATCH 00/33] Network fs helper library & fscache kiocb API [ver #3]

[Steve French]

On Mon, Feb 15, 2021 at 8:10 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Mon, Feb 15, 2021 at 06:40:27PM -0600, Steve French wrote:
> > It could be good if netfs simplifies the problem experienced by
> > network filesystems on Linux with readahead on large sequential reads
> > - where we don't get as much parallelism due to only having one
> > readahead request at a time (thus in many cases there is 'dead time'
> > on either the network or the file server while waiting for the next
> > readpages request to be issued).   This can be a significant
> > performance problem for current readpages when network latency is long
> > (or e.g. in cases when network encryption is enabled, and hardware
> > offload not available so time consuming on the server or client to
> > encrypt the packet).
> >
> > Do you see netfs much faster than currentreadpages for ceph?
> >
> > Have you been able to get much benefit from throttling readahead with
> > ceph from the current netfs approach for clamping i/o?
>
> The switch from readpages to readahead does help in a couple of corner
> cases.  For example, if you have two processes reading the same file at
> the same time, one will now block on the other (due to the page lock)
> rather than submitting a mess of overlapping and partial reads.
>
> We're not there yet on having multiple outstanding reads.  Bill and I
> had a chat recently about how to make the readahead code detect that
> it is in a "long fat pipe" situation (as opposed to just dealing with
> a slow device), and submit extra readahead requests to make best use of
> the bandwidth and minimise blocking of the application.
>
> That's not something for the netfs code to do though; we can get into
> that situation with highly parallel SSDs.

This (readahead behavior improvements in Linux, on single large file sequential
read workloads like cp or grep) gets particularly interesting
with SMB3 as multichannel becomes more common.  With one channel having
one readahead request pending on the network is suboptimal - but not as bad as
when multichannel is negotiated. Interestingly in most cases two
network connections
to the same server (different TCP sockets,but the same mount, even in
cases where
only network adapter) can achieve better performance - but still significantly
lags Windows (and probably other clients) as in Linux we don't keep
multiple I/Os
in flight at one time (unless different files are being read at the same time
by different threads).   As network adapters are added and removed from the
server (other client typically poll to detect interface changes, and SMB3
also leverages the "witness protocol" to get notification of adapter additions
or removals) - it would be helpful to change the maximum number of
readahead requests in flight.  In addition, as the server throttles back
(reducing the number of 'credits' granted to the client) it will be important
to give hints to the readahead logic about reducing the number of
read ahead requests in flight.   Keeping multiple readahead requests
is easier to imagine when multiple processes are copying or reading
files, but there are many scenarios where we could do better with parallelizing
a single process doing copy by ensuring that there is no 'dead time' on
the network.


-- 
Thanks,

Steve

Re: [PATCH 00/33] Network fs helper library & fscache kiocb API [ver #3]

[Steve French]

On Mon, Feb 15, 2021 at 8:10 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Mon, Feb 15, 2021 at 06:40:27PM -0600, Steve French wrote:
> > It could be good if netfs simplifies the problem experienced by
> > network filesystems on Linux with readahead on large sequential reads
> > - where we don't get as much parallelism due to only having one
> > readahead request at a time (thus in many cases there is 'dead time'
> > on either the network or the file server while waiting for the next
> > readpages request to be issued).   This can be a significant
> > performance problem for current readpages when network latency is long
> > (or e.g. in cases when network encryption is enabled, and hardware
> > offload not available so time consuming on the server or client to
> > encrypt the packet).
> >
> > Do you see netfs much faster than currentreadpages for ceph?
> >
> > Have you been able to get much benefit from throttling readahead with
> > ceph from the current netfs approach for clamping i/o?
>
> The switch from readpages to readahead does help in a couple of corner
> cases.  For example, if you have two processes reading the same file at
> the same time, one will now block on the other (due to the page lock)
> rather than submitting a mess of overlapping and partial reads.

Do you have a simple repro example of this we could try (fio, dbench, iozone
etc) to get some objective perf data?

My biggest worry is making sure that the switch to netfs doesn't degrade
performance (which might be a low bar now since current network file copy
perf seems to signifcantly lag at least Windows), and in some easy to understand
scenarios want to make sure it actually helps perf.

-- 
Thanks,

Steve

Re: [PATCH 00/33] Network fs helper library & fscache kiocb API [ver #3]

[Steve French]

On Mon, Feb 15, 2021 at 8:10 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Mon, Feb 15, 2021 at 06:40:27PM -0600, Steve French wrote:
> > It could be good if netfs simplifies the problem experienced by
> > network filesystems on Linux with readahead on large sequential reads
> > - where we don't get as much parallelism due to only having one
> > readahead request at a time (thus in many cases there is 'dead time'
> > on either the network or the file server while waiting for the next
> > readpages request to be issued).   This can be a significant
> > performance problem for current readpages when network latency is long
> > (or e.g. in cases when network encryption is enabled, and hardware
> > offload not available so time consuming on the server or client to
> > encrypt the packet).
> >
> > Do you see netfs much faster than currentreadpages for ceph?
> >
> > Have you been able to get much benefit from throttling readahead with
> > ceph from the current netfs approach for clamping i/o?
>
> The switch from readpages to readahead does help in a couple of corner
> cases.  For example, if you have two processes reading the same file at
> the same time, one will now block on the other (due to the page lock)
> rather than submitting a mess of overlapping and partial reads.

Do you have a simple repro example of this we could try (fio, dbench, iozone
etc) to get some objective perf data?

My biggest worry is making sure that the switch to netfs doesn't degrade
performance (which might be a low bar now since current network file copy
perf seems to signifcantly lag at least Windows), and in some easy to understand
scenarios want to make sure it actually helps perf.

-- 
Thanks,

Steve

Re: [PATCH 34/33] netfs: Use in_interrupt() not in_softirq()

[Christoph Hellwig]

On Mon, Feb 15, 2021 at 10:46:23PM +0000, David Howells wrote:
> The in_softirq() in netfs_rreq_terminated() works fine for the cache being
> on a normal disk, as the completion handlers may get called in softirq
> context, but for an NVMe drive, the completion handler may get called in
> IRQ context.
> 
> Fix to use in_interrupt() instead of in_softirq() throughout the read
> helpers, particularly when deciding whether to punt code that might sleep
> off to a worker thread.

We must not use either check, as they all are unreliable especially
for PREEMPT-RT.

Re: [PATCH 34/33] netfs: Use in_interrupt() not in_softirq()

[Sebastian Andrzej Siewior]

On 2021-02-16 09:42:30 [+0100], Christoph Hellwig wrote:
> On Mon, Feb 15, 2021 at 10:46:23PM +0000, David Howells wrote:
> > The in_softirq() in netfs_rreq_terminated() works fine for the cache being
> > on a normal disk, as the completion handlers may get called in softirq
> > context, but for an NVMe drive, the completion handler may get called in
> > IRQ context.
> > 
> > Fix to use in_interrupt() instead of in_softirq() throughout the read
> > helpers, particularly when deciding whether to punt code that might sleep
> > off to a worker thread.
> 
> We must not use either check, as they all are unreliable especially
> for PREEMPT-RT.

Yes, please. I try to cleanup the users one by one
    https://lore.kernel.org/r/20200914204209.256266093@linutronix.de/
    https://lore.kernel.org/amd-gfx/20210209124439.408140-1-bigeasy@linutronix.de/

Sebastian

Re: [PATCH 34/33] netfs: Use in_interrupt() not in_softirq()

[David Howells]

Christoph Hellwig <hch@lst.de> wrote:

> On Mon, Feb 15, 2021 at 10:46:23PM +0000, David Howells wrote:
> > The in_softirq() in netfs_rreq_terminated() works fine for the cache being
> > on a normal disk, as the completion handlers may get called in softirq
> > context, but for an NVMe drive, the completion handler may get called in
> > IRQ context.
> > 
> > Fix to use in_interrupt() instead of in_softirq() throughout the read
> > helpers, particularly when deciding whether to punt code that might sleep
> > off to a worker thread.
> 
> We must not use either check, as they all are unreliable especially
> for PREEMPT-RT.

Is there a better way to do it?  The intent is to process the assessment phase
in the calling thread's context if possible rather than bumping over to a
worker thread.  For synchronous I/O, for example, that's done in the caller's
thread.  Maybe that's the answer - if it's known to be asynchronous, I have to
punt, but otherwise don't have to.

David

Re: [PATCH 34/33] netfs: Use in_interrupt() not in_softirq()

[Christoph Hellwig]

On Tue, Feb 16, 2021 at 09:29:31AM +0000, David Howells wrote:
> Is there a better way to do it?  The intent is to process the assessment phase
> in the calling thread's context if possible rather than bumping over to a
> worker thread.  For synchronous I/O, for example, that's done in the caller's
> thread.  Maybe that's the answer - if it's known to be asynchronous, I have to
> punt, but otherwise don't have to.

Yes, i think you want an explicit flag instead.

Re: [PATCH 04/33] vfs: Export rw_verify_area() for use by cachefiles

[Christoph Hellwig]

On Mon, Feb 15, 2021 at 03:45:01PM +0000, David Howells wrote:
> Export rw_verify_area() for so that cachefiles can use it before issuing
> call_read_iter() and call_write_iter() to effect async DIO operations
> against the cache.  This is analogous to aio_read() and aio_write().

I don't think this is the right thing to do.  Instead of calling
into ->read_iter / ->write_iter directly this should be using helpers.

What prevents you from using vfs_iocb_iter_read and
vfs_iocb_iter_write which seem the right level of abstraction for this?

Re: [PATCH 02/33] mm: Add an unlock function for PG_private_2/PG_fscache

[Christoph Hellwig]

> +extern void unlock_page_private_2(struct page *page);

No need for the extern.

Otherwise this looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH 03/33] mm: Implement readahead_control pageset expansion

[Christoph Hellwig]

On Mon, Feb 15, 2021 at 03:44:52PM +0000, David Howells wrote:
> Provide a function, readahead_expand(), that expands the set of pages
> specified by a readahead_control object to encompass a revised area with a
> proposed size and length.
> 
> The proposed area must include all of the old area and may be expanded yet
> more by this function so that the edges align on (transparent huge) page
> boundaries as allocated.
> 
> The expansion will be cut short if a page already exists in either of the
> areas being expanded into.  Note that any expansion made in such a case is
> not rolled back.
> 
> This will be used by fscache so that reads can be expanded to cache granule
> boundaries, thereby allowing whole granules to be stored in the cache, but
> there are other potential users also.

So looking at linux-next this seems to have a user, but that user is
dead wood given that nothing implements ->expand_readahead.

Looking at the code structure I think netfs_readahead and
netfs_rreq_expand is a complete mess and needs to be turned upside
down, that is instead of calling back from netfs_readahead to the
calling file system, split it into a few helpers called by the
caller.

But even after this can't we just expose the cache granule boundary
to the VM so that the read-ahead request gets setup correctly from
the very beginning?

Re: [PATCH 14/33] fscache, cachefiles: Add alternate API to use kiocb for read/write to cache

[Christoph Hellwig]

On Mon, Feb 15, 2021 at 03:47:00PM +0000, David Howells wrote:
> Add an alternate API by which the cache can be accessed through a kiocb,
> doing async DIO, rather than using the current API that tells the cache
> where all the pages are.
> 
> The new API is intended to be used in conjunction with the netfs helper
> library.  A filesystem must pick one or the other and not mix them.
> 
> Filesystems wanting to use the new API must #define FSCACHE_USE_NEW_IO_API
> before #including the header

What exactly does this ifdef buys us?  It seems like the old and new
APIs don't even conflict.  And if we really need an ifdef I'd rather
use that for the old code to make grepping for that easier.

> +extern void cachefiles_put_object(struct fscache_object *_object,
> +				  enum fscache_obj_ref_trace why);

No need for the extern here on all the other function prototypes.

> +	if (ki->term_func) {
> +		if (ret < 0)
> +			ki->term_func(ki->term_func_priv, ret);
> +		else
> +			ki->term_func(ki->term_func_priv, ki->skipped + ret);

Why not simplify:

		if (ret > 0)
			ret += ki->skipped;
		ki->term_func(ki->term_func_priv, ret);

> +	/* If the caller asked us to seek for data before doing the read, then
> +	 * we should do that now.  If we find a gap, we fill it with zeros.
> +	 */

FYI, this is not the normal kernel comment style..

> +	ret = rw_verify_area(READ, file, &ki->iocb.ki_pos, len - skipped);
> +	if (ret < 0)
> +		goto presubmission_error_free;
> +
> +	get_file(ki->iocb.ki_filp);
> +
> +	old_nofs = memalloc_nofs_save();
> +	ret = call_read_iter(file, &ki->iocb, iter);
> +	memalloc_nofs_restore(old_nofs);

As mentioned before I think all this magic belongs in to a helper
in the VFS.

> +static const struct netfs_cache_ops cachefiles_netfs_cache_ops = {
> +	.end_operation		= cachefiles_end_operation,
> +	.read			= cachefiles_read,
> +	.write			= cachefiles_write,
> +	.expand_readahead	= NULL,
> +	.prepare_read		= cachefiles_prepare_read,
> +};

No need to set any member in a static allocated structure to zero.

Also at least in linux-next ->read and ->write seem to never actually
be called.

> +{
> +	struct cachefiles_object *object;
> +	struct cachefiles_cache *cache;
> +	struct path path;
> +	struct file *file;
> +
> +	_enter("");
> +
> +	object = container_of(op->op.object,
> +			      struct cachefiles_object, fscache);
> +	cache = container_of(object->fscache.cache,
> +			     struct cachefiles_cache, cache);
> +
> +	path.mnt = cache->mnt;
> +	path.dentry = object->backer;
> +	file = open_with_fake_path(&path, O_RDWR | O_LARGEFILE | O_DIRECT,
> +				   d_inode(object->backer), cache->cache_cred);

I think this should be plain old dentry_open?

> +extern struct fscache_retrieval *fscache_alloc_retrieval(struct fscache_cookie *,
> +							 struct address_space *,
> +							 fscache_rw_complete_t, void *);

No need for the extern.  And no need to indent the parameters totally out
sight, a single tab should be enough.  And it's always nice to spell out
the parameter names.

> +	op = fscache_alloc_retrieval(cookie, NULL, NULL, NULL);
> +	if (!op)
> +		return -ENOMEM;
> +	//atomic_set(&op->n_pages, 1);

???

> +static inline
> +int fscache_begin_read_operation(struct netfs_read_request *rreq,

Normal kernel style is to have the static and the inline on the
same line as the return type.

> +				 struct fscache_cookie *cookie)
> +{
> +	if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
> +		return __fscache_begin_read_operation(rreq, cookie);
> +	else
> +		return -ENOBUFS;
> +}

No need for an else after a return.  I personally also prefer to always
handle the error case first, ala:

        if (!fscache_cookie_valid(cookie) || !fscache_cookie_enabled(cookie))
	                return -ENOBUFS;
	return __fscache_begin_read_operation(rreq, cookie);

Also do we really need this inline fast path to start with?

Re: [PATCH 00/33] Network fs helper library & fscache kiocb API [ver #3]

[Jeff Layton]

On Mon, 2021-02-15 at 18:40 -0600, Steve French wrote:
> Jeff,
> What are the performance differences you are seeing (positive or
> negative) with ceph and netfs, especially with simple examples like
> file copy or grep of large files?
> 
> It could be good if netfs simplifies the problem experienced by
> network filesystems on Linux with readahead on large sequential reads
> - where we don't get as much parallelism due to only having one
> readahead request at a time (thus in many cases there is 'dead time'
> on either the network or the file server while waiting for the next
> readpages request to be issued).   This can be a significant
> performance problem for current readpages when network latency is long
> (or e.g. in cases when network encryption is enabled, and hardware
> offload not available so time consuming on the server or client to
> encrypt the packet).
> 
> Do you see netfs much faster than currentreadpages for ceph?
> 
> Have you been able to get much benefit from throttling readahead with
> ceph from the current netfs approach for clamping i/o?
> 

I haven't seen big performance differences at all with this set. It's
pretty much a wash, and it doesn't seem to change how the I/Os are
ultimately driven on the wire. For instance, the clamp_length op
basically just mirrors what ceph does today -- it ensures that the
length of the I/O can't go past the end of the current object.

The main benefits are that we get a large swath of readpage, readpages
amd write_begin code out of ceph altogether. All of the netfs's need to
gather and vet pages for I/O, etc. Most of that doesn't have anything to
do with the filesystem itself. By offloading that into the netfs lib,
most of that is taken care of for us and we don't need to bother with
doing that ourselves.

-- 
Jeff Layton <jlayton@redhat.com>

Re: [PATCH 00/33] Network fs helper library & fscache kiocb API [ver #3]

[Jeff Layton]

On Mon, 2021-02-15 at 18:40 -0600, Steve French wrote:
> Jeff,
> What are the performance differences you are seeing (positive or
> negative) with ceph and netfs, especially with simple examples like
> file copy or grep of large files?
> 
> It could be good if netfs simplifies the problem experienced by
> network filesystems on Linux with readahead on large sequential reads
> - where we don't get as much parallelism due to only having one
> readahead request at a time (thus in many cases there is 'dead time'
> on either the network or the file server while waiting for the next
> readpages request to be issued).   This can be a significant
> performance problem for current readpages when network latency is long
> (or e.g. in cases when network encryption is enabled, and hardware
> offload not available so time consuming on the server or client to
> encrypt the packet).
> 
> Do you see netfs much faster than currentreadpages for ceph?
> 
> Have you been able to get much benefit from throttling readahead with
> ceph from the current netfs approach for clamping i/o?
> 

I haven't seen big performance differences at all with this set. It's
pretty much a wash, and it doesn't seem to change how the I/Os are
ultimately driven on the wire. For instance, the clamp_length op
basically just mirrors what ceph does today -- it ensures that the
length of the I/O can't go past the end of the current object.

The main benefits are that we get a large swath of readpage, readpages
amd write_begin code out of ceph altogether. All of the netfs's need to
gather and vet pages for I/O, etc. Most of that doesn't have anything to
do with the filesystem itself. By offloading that into the netfs lib,
most of that is taken care of for us and we don't need to bother with
doing that ourselves.

-- 
Jeff Layton <jlayton@redhat.com>

Re: [PATCH 03/33] mm: Implement readahead_control pageset expansion

[David Howells]

Christoph Hellwig <hch@lst.de> wrote:

> On Mon, Feb 15, 2021 at 03:44:52PM +0000, David Howells wrote:
> > Provide a function, readahead_expand(), that expands the set of pages
> > specified by a readahead_control object to encompass a revised area with a
> > proposed size and length.
> ...
> So looking at linux-next this seems to have a user, but that user is
> dead wood given that nothing implements ->expand_readahead.

Interesting question.  Code on my fscache-iter branch does implement this, but
I was asked to split the patchset up, so that's not in this subset.

> Looking at the code structure I think netfs_readahead and
> netfs_rreq_expand is a complete mess and needs to be turned upside
> down, that is instead of calling back from netfs_readahead to the
> calling file system, split it into a few helpers called by the
> caller.
> 
> But even after this can't we just expose the cache granule boundary
> to the VM so that the read-ahead request gets setup correctly from
> the very beginning?

You need to argue this one with Willy.  In my opinion, the VM should ask the
filesystem and the expansion be done before ->readahead() is called.  Willy
disagrees, however.

David

Re: [PATCH 04/33] vfs: Export rw_verify_area() for use by cachefiles

[David Howells]

Christoph Hellwig <hch@lst.de> wrote:

> > Export rw_verify_area() for so that cachefiles can use it before issuing
> > call_read_iter() and call_write_iter() to effect async DIO operations
> > against the cache.  This is analogous to aio_read() and aio_write().
> 
> I don't think this is the right thing to do.  Instead of calling
> into ->read_iter / ->write_iter directly this should be using helpers.
> 
> What prevents you from using vfs_iocb_iter_read and
> vfs_iocb_iter_write which seem the right level of abstraction for this?

I don't think they existed when I wrote this code.  Should aio use that too,
btw?  I modelled my code on aio_read() and aio_write().

But I can certainly switch to using vfs_iocb_iter_read/write, though the
trivial checks are redundant.  The fsnotify call, I guess I'm missing though
(and is that missing in aio_read/write() also?).

David

Re: [PATCH 03/33] mm: Implement readahead_control pageset expansion

[Matthew Wilcox]

On Tue, Feb 16, 2021 at 11:32:15AM +0100, Christoph Hellwig wrote:
> On Mon, Feb 15, 2021 at 03:44:52PM +0000, David Howells wrote:
> > Provide a function, readahead_expand(), that expands the set of pages
> > specified by a readahead_control object to encompass a revised area with a
> > proposed size and length.
> > 
> > The proposed area must include all of the old area and may be expanded yet
> > more by this function so that the edges align on (transparent huge) page
> > boundaries as allocated.
> > 
> > The expansion will be cut short if a page already exists in either of the
> > areas being expanded into.  Note that any expansion made in such a case is
> > not rolled back.
> > 
> > This will be used by fscache so that reads can be expanded to cache granule
> > boundaries, thereby allowing whole granules to be stored in the cache, but
> > there are other potential users also.
> 
> So looking at linux-next this seems to have a user, but that user is
> dead wood given that nothing implements ->expand_readahead.
> 
> Looking at the code structure I think netfs_readahead and
> netfs_rreq_expand is a complete mess and needs to be turned upside
> down, that is instead of calling back from netfs_readahead to the
> calling file system, split it into a few helpers called by the
> caller.

That's funny, we modelled it after iomap.

> But even after this can't we just expose the cache granule boundary
> to the VM so that the read-ahead request gets setup correctly from
> the very beginning?

The intent is that this be usable by filesystems which want to (for
example) compress variable sized blocks.  So they won't know which pages
they want to readahead until they're in their iomap actor routine,
see that the extent they're in is compressed, and find out how large
the extent is.

Re: [PATCH 14/33] fscache, cachefiles: Add alternate API to use kiocb for read/write to cache

[David Howells]

Christoph Hellwig <hch@lst.de> wrote:

> > Filesystems wanting to use the new API must #define FSCACHE_USE_NEW_IO_API
> > before #including the header
> 
> What exactly does this ifdef buys us?  It seems like the old and new
> APIs don't even conflict.

I was asked to add this.  The APIs look like they don't conflict, but you
can't mix them for a given file because of the differing behaviour of the
PG_fscache flag.  It also makes it much easier to make sure you don't miss
something.  That has happened and it led to some strange effects before we
worked out what was going on.

> And if we really need an ifdef I'd rather use that for the old code to make
> grepping for that easier.

I can do it that way - but this doesn't require changing filesystems that
aren't being changed.  The intent would be to eliminate the #ifdef in a cycle
or two anyway.

Besides, there are 5 filesystems that use this, and two of them are converted
here.  grep would only return three hits: one each in fs/9p/cache.h,
fs/cifs/fscache.h and fs/nfs/fscache.h.

OTOH, I suppose it might dissuade people from adding new usages of the old
API.

> > +	if (ki->term_func) {
> > +		if (ret < 0)
> > +			ki->term_func(ki->term_func_priv, ret);
> > +		else
> > +			ki->term_func(ki->term_func_priv, ki->skipped + ret);
> 
> Why not simplify:
> 
> 		if (ret > 0)
> 			ret += ki->skipped;
> 		ki->term_func(ki->term_func_priv, ret);

Could do that I suppose.  The optimiser will make them the same anyway.

I still wonder if I should do something with ret2 as obtained from the kiocb
completion function:

  static void cachefiles_read_complete(struct kiocb *iocb, long ret, long ret2)

Can we consolidate to one return value?

> > +	/* If the caller asked us to seek for data before doing the read, then
> > +	 * we should do that now.  If we find a gap, we fill it with zeros.
> > +	 */
> 
> FYI, this is not the normal kernel comment style..

I've been following the network style.

> > +	ret = rw_verify_area(READ, file, &ki->iocb.ki_pos, len - skipped);
> > +	if (ret < 0)
> > +		goto presubmission_error_free;
> > +
> > +	get_file(ki->iocb.ki_filp);
> > +
> > +	old_nofs = memalloc_nofs_save();
> > +	ret = call_read_iter(file, &ki->iocb, iter);
> > +	memalloc_nofs_restore(old_nofs);
> 
> As mentioned before I think all this magic belongs in to a helper
> in the VFS.

You suggested vfs_iocb_iter_read() in your reply to another patch, but it
occurs to me that that doesn't have memalloc_nofs_*() in it.  I could hoist
the memalloc_nofs stuff out and use those helpers.

> > +static const struct netfs_cache_ops cachefiles_netfs_cache_ops = {
> > +	.end_operation		= cachefiles_end_operation,
> > +	.read			= cachefiles_read,
> > +	.write			= cachefiles_write,
> > +	.expand_readahead	= NULL,
> > +	.prepare_read		= cachefiles_prepare_read,
> > +};
> ...
> Also at least in linux-next ->read and ->write seem to never actually
> be called.

See netfs_read_from_cache() and netfs_rreq_do_write_to_cache() in
fs/netfs/read_helper.c.  Look for "cres->ops->".

> > +{
> > +	struct cachefiles_object *object;
> > +	struct cachefiles_cache *cache;
> > +	struct path path;
> > +	struct file *file;
> > +
> > +	_enter("");
> > +
> > +	object = container_of(op->op.object,
> > +			      struct cachefiles_object, fscache);
> > +	cache = container_of(object->fscache.cache,
> > +			     struct cachefiles_cache, cache);
> > +
> > +	path.mnt = cache->mnt;
> > +	path.dentry = object->backer;
> > +	file = open_with_fake_path(&path, O_RDWR | O_LARGEFILE | O_DIRECT,
> > +				   d_inode(object->backer), cache->cache_cred);
> 
> I think this should be plain old dentry_open?

open_with_fake_path() sets FMODE_NOACCOUNT.  In the fscache-iter branch, the
file is held open a lot longer and then ENFILE/EMFILE starts being a serious
problem.

That said, I'm considering changing things so that all the data in the cache
is held in one or a few files with an index to locate things - at which point
this issue goes away.

> > +	op = fscache_alloc_retrieval(cookie, NULL, NULL, NULL);
> > +	if (!op)
> > +		return -ENOMEM;
> > +	//atomic_set(&op->n_pages, 1);
> 
> ???

I should remove that - it kind of got left behind.  That was necessary for the
old API, but a whole load of this code, including the fscache_retrieval struct
will be going away when the cookie and operation handling get rewritten.

> > +{
> > +	if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
> > +		return __fscache_begin_read_operation(rreq, cookie);
> > +	else
> > +		return -ENOBUFS;
> > +}
> 
> No need for an else after a return.  I personally also prefer to always
> handle the error case first, ala:

It's not precisely an error case, more a "fallback required" case.

>         if (!fscache_cookie_valid(cookie) || !fscache_cookie_enabled(cookie))
> 	                return -ENOBUFS;
> 	return __fscache_begin_read_operation(rreq, cookie);
> 
> Also do we really need this inline fast path to start with?

Yes.  fscache might be compiled out, in which case we'll never go down the
slow path.  And the common case is that cookie == NULL, so let's not jump out
of line if we don't have to.

David

Re: [PATCH 03/33] mm: Implement readahead_control pageset expansion

[Mike Marshall]

I plan to try and use readahead_expand in Orangefs...

-Mike

On Tue, Feb 16, 2021 at 8:28 AM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Tue, Feb 16, 2021 at 11:32:15AM +0100, Christoph Hellwig wrote:
> > On Mon, Feb 15, 2021 at 03:44:52PM +0000, David Howells wrote:
> > > Provide a function, readahead_expand(), that expands the set of pages
> > > specified by a readahead_control object to encompass a revised area with a
> > > proposed size and length.
> > >
> > > The proposed area must include all of the old area and may be expanded yet
> > > more by this function so that the edges align on (transparent huge) page
> > > boundaries as allocated.
> > >
> > > The expansion will be cut short if a page already exists in either of the
> > > areas being expanded into.  Note that any expansion made in such a case is
> > > not rolled back.
> > >
> > > This will be used by fscache so that reads can be expanded to cache granule
> > > boundaries, thereby allowing whole granules to be stored in the cache, but
> > > there are other potential users also.
> >
> > So looking at linux-next this seems to have a user, but that user is
> > dead wood given that nothing implements ->expand_readahead.
> >
> > Looking at the code structure I think netfs_readahead and
> > netfs_rreq_expand is a complete mess and needs to be turned upside
> > down, that is instead of calling back from netfs_readahead to the
> > calling file system, split it into a few helpers called by the
> > caller.
>
> That's funny, we modelled it after iomap.
>
> > But even after this can't we just expose the cache granule boundary
> > to the VM so that the read-ahead request gets setup correctly from
> > the very beginning?
>
> The intent is that this be usable by filesystems which want to (for
> example) compress variable sized blocks.  So they won't know which pages
> they want to readahead until they're in their iomap actor routine,
> see that the extent they're in is compressed, and find out how large
> the extent is.

Re: [PATCH 03/33] mm: Implement readahead_control pageset expansion

[Mike Marshall]

I plan to try and use readahead_expand in Orangefs...

-Mike

On Tue, Feb 16, 2021 at 8:28 AM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Tue, Feb 16, 2021 at 11:32:15AM +0100, Christoph Hellwig wrote:
> > On Mon, Feb 15, 2021 at 03:44:52PM +0000, David Howells wrote:
> > > Provide a function, readahead_expand(), that expands the set of pages
> > > specified by a readahead_control object to encompass a revised area with a
> > > proposed size and length.
> > >
> > > The proposed area must include all of the old area and may be expanded yet
> > > more by this function so that the edges align on (transparent huge) page
> > > boundaries as allocated.
> > >
> > > The expansion will be cut short if a page already exists in either of the
> > > areas being expanded into.  Note that any expansion made in such a case is
> > > not rolled back.
> > >
> > > This will be used by fscache so that reads can be expanded to cache granule
> > > boundaries, thereby allowing whole granules to be stored in the cache, but
> > > there are other potential users also.
> >
> > So looking at linux-next this seems to have a user, but that user is
> > dead wood given that nothing implements ->expand_readahead.
> >
> > Looking at the code structure I think netfs_readahead and
> > netfs_rreq_expand is a complete mess and needs to be turned upside
> > down, that is instead of calling back from netfs_readahead to the
> > calling file system, split it into a few helpers called by the
> > caller.
>
> That's funny, we modelled it after iomap.
>
> > But even after this can't we just expose the cache granule boundary
> > to the VM so that the read-ahead request gets setup correctly from
> > the very beginning?
>
> The intent is that this be usable by filesystems which want to (for
> example) compress variable sized blocks.  So they won't know which pages
> they want to readahead until they're in their iomap actor routine,
> see that the extent they're in is compressed, and find out how large
> the extent is.

Re: [PATCH 03/33] mm: Implement readahead_control pageset expansion

[David Howells]

Mike Marshall <hubcap@omnibond.com> wrote:

> I plan to try and use readahead_expand in Orangefs...

Would it help if I shuffled the readahead_expand patch to the bottom of the
pack?

David

Re: [PATCH 03/33] mm: Implement readahead_control pageset expansion

[Matthew Wilcox]

On Mon, Feb 15, 2021 at 03:44:52PM +0000, David Howells wrote:
> +++ b/include/linux/pagemap.h
> @@ -761,6 +761,8 @@ extern void __delete_from_page_cache(struct page *page, void *shadow);
>  int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask);
>  void delete_from_page_cache_batch(struct address_space *mapping,
>  				  struct pagevec *pvec);
> +void readahead_expand(struct readahead_control *ractl,
> +		      loff_t new_start, size_t new_len);

If we're revising this patchset, I'd rather this lived with the other
readahead declarations, ie after the definition of readahead_control.

> +	/* Expand the trailing edge upwards */
> +	while (ractl->_nr_pages < new_nr_pages) {
> +		unsigned long index = ractl->_index + ractl->_nr_pages;
> +		struct page *page = xa_load(&mapping->i_pages, index);
> +
> +		if (page && !xa_is_value(page))
> +			return; /* Page apparently present */
> +
> +		page = __page_cache_alloc(gfp_mask);
> +		if (!page)
> +			return;
> +		if (add_to_page_cache_lru(page, mapping, index, gfp_mask) < 0) {
> +			put_page(page);
> +			return;
> +		}
> +		ractl->_nr_pages++;
> +	}

We're defeating the ondemand_readahead() algorithm here.  Let's suppose
userspace is doing 64kB reads, the filesystem is OrangeFS which only
wants to do 4MB reads, the page cache is initially empty and there's
only one thread doing a sequential read.  ondemand_readahead() calls
get_init_ra_size() which tells it to allocate 128kB and set the async
marker at 64kB.  Then orangefs calls readahead_expand() to allocate the
remainder of the 4MB.  After the app has read the first 64kB, it comes
back to read the next 64kB, sees the readahead marker and tries to trigger
the next batch of readahead, but it's already present, so it does nothing
(see page_cache_ra_unbounded() for what happens with pages present).

Then it keeps going through the 4MB that's been read, not seeing any more
readahead markers, gets to 4MB and asks for ... 256kB?  Not quite sure.
Anyway, it then has to wait for the next 4MB because the readahead didn't
overlap with the application processing.

So readahead_expand() needs to adjust the file's f_ra so that when the
application gets to 64kB, it kicks off the readahead of 4MB-8MB chunk (and
then when we get to 4MB+256kB, it kicks off the readahead of 8MB-12MB,
and so on).

Unless someone sees a better way to do this?  I don't
want to inadvertently break POSIX_FADV_WILLNEED which calls
force_page_cache_readahead() and should not perturb the kernel's
ondemand algorithm.  Perhaps we need to add an 'ra' pointer to the
ractl to indicate whether the file_ra_state should be updated by
readahead_expand()?

Re: [PATCH 03/33] mm: Implement readahead_control pageset expansion

[Mike Marshall]

Matthew has looked at how I'm fumbling about
trying to deal with Orangefs's need for much larger
than page-sized IO...

I think I need to implement orangefs_readahead
and from there fire off an asynchronous read
and while that's going I'll call readahead_page
with a rac that I've cranked up with readahead_expand
and when the read gets done I'll have plenty of pages
for the large IO I did.

Even if what I think I need to do is somewhere
near right, the async code in the Orangefs
kernel module didn't make it into the upstream
version, so I have to refurbish that. All that to
say: I don't need readahead_expand
"tomorrow", but it fits into my plan to
get Orangefs the extra pages it needs
without me having open-coded page cache
code in orangefs_readpage.

-Mike

On Wed, Feb 17, 2021 at 10:42 AM David Howells <dhowells@redhat.com> wrote:
>
> Mike Marshall <hubcap@omnibond.com> wrote:
>
> > I plan to try and use readahead_expand in Orangefs...
>
> Would it help if I shuffled the readahead_expand patch to the bottom of the
> pack?
>
> David
>

Re: [PATCH 03/33] mm: Implement readahead_control pageset expansion

[Mike Marshall]

Matthew has looked at how I'm fumbling about
trying to deal with Orangefs's need for much larger
than page-sized IO...

I think I need to implement orangefs_readahead
and from there fire off an asynchronous read
and while that's going I'll call readahead_page
with a rac that I've cranked up with readahead_expand
and when the read gets done I'll have plenty of pages
for the large IO I did.

Even if what I think I need to do is somewhere
near right, the async code in the Orangefs
kernel module didn't make it into the upstream
version, so I have to refurbish that. All that to
say: I don't need readahead_expand
"tomorrow", but it fits into my plan to
get Orangefs the extra pages it needs
without me having open-coded page cache
code in orangefs_readpage.

-Mike

On Wed, Feb 17, 2021 at 10:42 AM David Howells <dhowells@redhat.com> wrote:
>
> Mike Marshall <hubcap@omnibond.com> wrote:
>
> > I plan to try and use readahead_expand in Orangefs...
>
> Would it help if I shuffled the readahead_expand patch to the bottom of the
> pack?
>
> David
>

Re: [PATCH 03/33] mm: Implement readahead_control pageset expansion

[David Howells]

Mike Marshall <hubcap@omnibond.com> wrote:

> Matthew has looked at how I'm fumbling about
> trying to deal with Orangefs's need for much larger
> than page-sized IO...
> 
> I think I need to implement orangefs_readahead
> and from there fire off an asynchronous read
> and while that's going I'll call readahead_page
> with a rac that I've cranked up with readahead_expand
> and when the read gets done I'll have plenty of pages
> for the large IO I did.

Would the netfs helper lib in patches 5-13 here be of use to orangefs?  Most
of the information about it is on patch 8.

David

Re: [PATCH 03/33] mm: Implement readahead_control pageset expansion

[David Howells]

Matthew Wilcox <willy@infradead.org> wrote:

> We're defeating the ondemand_readahead() algorithm here.  Let's suppose
> userspace is doing 64kB reads, the filesystem is OrangeFS which only
> wants to do 4MB reads, the page cache is initially empty and there's
> only one thread doing a sequential read.  ondemand_readahead() calls
> get_init_ra_size() which tells it to allocate 128kB and set the async
> marker at 64kB.  Then orangefs calls readahead_expand() to allocate the
> remainder of the 4MB.  After the app has read the first 64kB, it comes
> back to read the next 64kB, sees the readahead marker and tries to trigger
> the next batch of readahead, but it's already present, so it does nothing
> (see page_cache_ra_unbounded() for what happens with pages present).

It sounds like Christoph is right on the right track and the vm needs to ask
the filesystem (and by extension, the cache) before doing the allocation and
before setting the trigger flag.  Then we don't need to call back into the vm
to expand the readahead.

Also, there's Steve's request to try and keep at least two requests in flight
for CIFS/SMB at the same time to consider.

David

Re: [PATCH 03/33] mm: Implement readahead_control pageset expansion

[Matthew Wilcox]

On Wed, Feb 17, 2021 at 10:34:39PM +0000, David Howells wrote:
> Matthew Wilcox <willy@infradead.org> wrote:
> 
> > We're defeating the ondemand_readahead() algorithm here.  Let's suppose
> > userspace is doing 64kB reads, the filesystem is OrangeFS which only
> > wants to do 4MB reads, the page cache is initially empty and there's
> > only one thread doing a sequential read.  ondemand_readahead() calls
> > get_init_ra_size() which tells it to allocate 128kB and set the async
> > marker at 64kB.  Then orangefs calls readahead_expand() to allocate the
> > remainder of the 4MB.  After the app has read the first 64kB, it comes
> > back to read the next 64kB, sees the readahead marker and tries to trigger
> > the next batch of readahead, but it's already present, so it does nothing
> > (see page_cache_ra_unbounded() for what happens with pages present).
> 
> It sounds like Christoph is right on the right track and the vm needs to ask
> the filesystem (and by extension, the cache) before doing the allocation and
> before setting the trigger flag.  Then we don't need to call back into the vm
> to expand the readahead.

Doesn't work.  You could read my reply to Christoph, or try to figure out
how to get rid of
https://evilpiepirate.org/git/bcachefs.git/tree/fs/bcachefs/fs-io.c#n742
for yourself.

> Also, there's Steve's request to try and keep at least two requests in flight
> for CIFS/SMB at the same time to consider.

That's not relevant to this problem.

[PATCH 34/33] netfs: Pass flag rather than use in_softirq()

[David Howells]

Christoph Hellwig <hch@lst.de> wrote:

> On Tue, Feb 16, 2021 at 09:29:31AM +0000, David Howells wrote:
> > Is there a better way to do it?  The intent is to process the assessment
> > phase in the calling thread's context if possible rather than bumping over
> > to a worker thread.  For synchronous I/O, for example, that's done in the
> > caller's thread.  Maybe that's the answer - if it's known to be
> > asynchronous, I have to punt, but otherwise don't have to.
> 
> Yes, i think you want an explicit flag instead.

How about the attached instead?

David
---
commit 29b3e9eed616db01f15c7998c062b4e501ea6582
Author: David Howells <dhowells@redhat.com>
Date:   Mon Feb 15 21:56:43 2021 +0000

    netfs: Pass flag rather than use in_softirq()
    
    The in_softirq() in netfs_rreq_terminated() works fine for the cache being
    on a normal disk, as the completion handlers may get called in softirq
    context, but for an NVMe drive, the completion handler may get called in
    IRQ context.
    
    Fix to pass a flag to netfs_subreq_terminated() to indicate whether we
    think the function isn't being called from a context in which we can do
    allocations, waits and I/O submissions (such as softirq or interrupt
    context).  If this flag is set, netfs lib has to punt to a worker thread to
    handle anything like that.
    
    The symptom involves warnings like the following appearing and the kernel
    hanging:
    
     WARNING: CPU: 0 PID: 0 at kernel/softirq.c:175 __local_bh_enable_ip+0x35/0x50
     ...
     RIP: 0010:__local_bh_enable_ip+0x35/0x50
     ...
     Call Trace:
      <IRQ>
      rxrpc_kernel_begin_call+0x7d/0x1b0 [rxrpc]
      ? afs_rx_new_call+0x40/0x40 [kafs]
      ? afs_alloc_call+0x28/0x120 [kafs]
      afs_make_call+0x120/0x510 [kafs]
      ? afs_rx_new_call+0x40/0x40 [kafs]
      ? afs_alloc_flat_call+0xba/0x100 [kafs]
      ? __kmalloc+0x167/0x2f0
      ? afs_alloc_flat_call+0x9b/0x100 [kafs]
      afs_wait_for_operation+0x2d/0x200 [kafs]
      afs_do_sync_operation+0x16/0x20 [kafs]
      afs_req_issue_op+0x8c/0xb0 [kafs]
      netfs_rreq_assess+0x125/0x7d0 [netfs]
      ? cachefiles_end_operation+0x40/0x40 [cachefiles]
      netfs_subreq_terminated+0x117/0x220 [netfs]
      cachefiles_read_complete+0x21/0x60 [cachefiles]
      iomap_dio_bio_end_io+0xdd/0x110
      blk_update_request+0x20a/0x380
      blk_mq_end_request+0x1c/0x120
      nvme_process_cq+0x159/0x1f0 [nvme]
      nvme_irq+0x10/0x20 [nvme]
      __handle_irq_event_percpu+0x37/0x150
      handle_irq_event+0x49/0xb0
      handle_edge_irq+0x7c/0x200
      asm_call_irq_on_stack+0xf/0x20
      </IRQ>
      common_interrupt+0xad/0x120
      asm_common_interrupt+0x1e/0x40
     ...
    
    Reported-by: Marc Dionne <marc.dionne@auristor.com>
    Signed-off-by: David Howells <dhowells@redhat.com>
    cc: Matthew Wilcox <willy@infradead.org>
    cc: linux-mm@kvack.org
    cc: linux-cachefs@redhat.com
    cc: linux-afs@lists.infradead.org
    cc: linux-nfs@vger.kernel.org
    cc: linux-cifs@vger.kernel.org
    cc: ceph-devel@vger.kernel.org
    cc: v9fs-developer@lists.sourceforge.net
    cc: linux-fsdevel@vger.kernel.org

diff --git a/fs/afs/file.c b/fs/afs/file.c
index 8f28d4f4cfd7..6dcdbbfb48e2 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -223,7 +223,7 @@ static void afs_fetch_data_notify(struct afs_operation *op)
 
 	if (subreq) {
 		__set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
-		netfs_subreq_terminated(subreq, error ?: req->actual_len);
+		netfs_subreq_terminated(subreq, error ?: req->actual_len, false);
 		req->subreq = NULL;
 	} else if (req->done) {
 		req->done(req);
@@ -289,7 +289,7 @@ static void afs_req_issue_op(struct netfs_read_subrequest *subreq)
 
 	fsreq = afs_alloc_read(GFP_NOFS);
 	if (!fsreq)
-		return netfs_subreq_terminated(subreq, -ENOMEM);
+		return netfs_subreq_terminated(subreq, -ENOMEM, false);
 
 	fsreq->subreq	= subreq;
 	fsreq->pos	= subreq->start + subreq->transferred;
@@ -304,7 +304,7 @@ static void afs_req_issue_op(struct netfs_read_subrequest *subreq)
 
 	ret = afs_fetch_data(fsreq->vnode, fsreq);
 	if (ret < 0)
-		return netfs_subreq_terminated(subreq, ret);
+		return netfs_subreq_terminated(subreq, ret, false);
 }
 
 static int afs_symlink_readpage(struct page *page)
diff --git a/fs/cachefiles/rdwr2.c b/fs/cachefiles/rdwr2.c
index 4cea5a2a2d6e..40668bfe6688 100644
--- a/fs/cachefiles/rdwr2.c
+++ b/fs/cachefiles/rdwr2.c
@@ -23,6 +23,7 @@ struct cachefiles_kiocb {
 	};
 	netfs_io_terminated_t	term_func;
 	void			*term_func_priv;
+	bool			was_async;
 };
 
 static inline void cachefiles_put_kiocb(struct cachefiles_kiocb *ki)
@@ -43,10 +44,9 @@ static void cachefiles_read_complete(struct kiocb *iocb, long ret, long ret2)
 	_enter("%ld,%ld", ret, ret2);
 
 	if (ki->term_func) {
-		if (ret < 0)
-			ki->term_func(ki->term_func_priv, ret);
-		else
-			ki->term_func(ki->term_func_priv, ki->skipped + ret);
+		if (ret >= 0)
+			ret += ki->skipped;
+		ki->term_func(ki->term_func_priv, ret, ki->was_async);
 	}
 
 	cachefiles_put_kiocb(ki);
@@ -114,6 +114,7 @@ static int cachefiles_read(struct netfs_cache_resources *cres,
 	ki->skipped		= skipped;
 	ki->term_func		= term_func;
 	ki->term_func_priv	= term_func_priv;
+	ki->was_async		= true;
 
 	if (ki->term_func)
 		ki->iocb.ki_complete = cachefiles_read_complete;
@@ -141,6 +142,7 @@ static int cachefiles_read(struct netfs_cache_resources *cres,
 		ret = -EINTR;
 		fallthrough;
 	default:
+		ki->was_async = false;
 		cachefiles_read_complete(&ki->iocb, ret, 0);
 		if (ret > 0)
 			ret = 0;
@@ -156,7 +158,7 @@ static int cachefiles_read(struct netfs_cache_resources *cres,
 	kfree(ki);
 presubmission_error:
 	if (term_func)
-		term_func(term_func_priv, ret < 0 ? ret : skipped);
+		term_func(term_func_priv, ret < 0 ? ret : skipped, false);
 	return ret;
 }
 
@@ -175,7 +177,7 @@ static void cachefiles_write_complete(struct kiocb *iocb, long ret, long ret2)
 	__sb_end_write(inode->i_sb, SB_FREEZE_WRITE);
 
 	if (ki->term_func)
-		ki->term_func(ki->term_func_priv, ret);
+		ki->term_func(ki->term_func_priv, ret, ki->was_async);
 
 	cachefiles_put_kiocb(ki);
 }
@@ -214,6 +216,7 @@ static int cachefiles_write(struct netfs_cache_resources *cres,
 	ki->len			= len;
 	ki->term_func		= term_func;
 	ki->term_func_priv	= term_func_priv;
+	ki->was_async		= true;
 
 	if (ki->term_func)
 		ki->iocb.ki_complete = cachefiles_write_complete;
@@ -250,6 +253,7 @@ static int cachefiles_write(struct netfs_cache_resources *cres,
 		ret = -EINTR;
 		/* Fall through */
 	default:
+		ki->was_async = false;
 		cachefiles_write_complete(&ki->iocb, ret, 0);
 		if (ret > 0)
 			ret = 0;
@@ -265,7 +269,7 @@ static int cachefiles_write(struct netfs_cache_resources *cres,
 	kfree(ki);
 presubmission_error:
 	if (term_func)
-		term_func(term_func_priv, -ENOMEM);
+		term_func(term_func_priv, -ENOMEM, false);
 	return -ENOMEM;
 }
 
diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 0dd64d31eff6..dcfd805d168e 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -221,7 +221,7 @@ static void finish_netfs_read(struct ceph_osd_request *req)
 	if (err >= 0 && err < subreq->len)
 		__set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
 
-	netfs_subreq_terminated(subreq, err);
+	netfs_subreq_terminated(subreq, err, true);
 
 	num_pages = calc_pages_for(osd_data->alignment, osd_data->length);
 	ceph_put_page_vector(osd_data->pages, num_pages, false);
@@ -276,7 +276,7 @@ static void ceph_netfs_issue_op(struct netfs_read_subrequest *subreq)
 out:
 	ceph_osdc_put_request(req);
 	if (err)
-		netfs_subreq_terminated(subreq, err);
+		netfs_subreq_terminated(subreq, err, false);
 	dout("%s: result %d\n", __func__, err);
 }
 
diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c
index 9191a3617d91..5f5de8278499 100644
--- a/fs/netfs/read_helper.c
+++ b/fs/netfs/read_helper.c
@@ -29,12 +29,13 @@ module_param_named(debug, netfs_debug, uint, S_IWUSR | S_IRUGO);
 MODULE_PARM_DESC(netfs_debug, "Netfs support debugging mask");
 
 static void netfs_rreq_work(struct work_struct *);
-static void __netfs_put_subrequest(struct netfs_read_subrequest *);
+static void __netfs_put_subrequest(struct netfs_read_subrequest *, bool);
 
-static void netfs_put_subrequest(struct netfs_read_subrequest *subreq)
+static void netfs_put_subrequest(struct netfs_read_subrequest *subreq,
+				 bool was_async)
 {
 	if (refcount_dec_and_test(&subreq->usage))
-		__netfs_put_subrequest(subreq);
+		__netfs_put_subrequest(subreq, was_async);
 }
 
 static struct netfs_read_request *netfs_alloc_read_request(
@@ -67,7 +68,8 @@ static void netfs_get_read_request(struct netfs_read_request *rreq)
 	refcount_inc(&rreq->usage);
 }
 
-static void netfs_rreq_clear_subreqs(struct netfs_read_request *rreq)
+static void netfs_rreq_clear_subreqs(struct netfs_read_request *rreq,
+				     bool was_async)
 {
 	struct netfs_read_subrequest *subreq;
 
@@ -75,7 +77,7 @@ static void netfs_rreq_clear_subreqs(struct netfs_read_request *rreq)
 		subreq = list_first_entry(&rreq->subrequests,
 					  struct netfs_read_subrequest, rreq_link);
 		list_del(&subreq->rreq_link);
-		netfs_put_subrequest(subreq);
+		netfs_put_subrequest(subreq, was_async);
 	}
 }
 
@@ -83,7 +85,7 @@ static void netfs_free_read_request(struct work_struct *work)
 {
 	struct netfs_read_request *rreq =
 		container_of(work, struct netfs_read_request, work);
-	netfs_rreq_clear_subreqs(rreq);
+	netfs_rreq_clear_subreqs(rreq, false);
 	if (rreq->netfs_priv)
 		rreq->netfs_ops->cleanup(rreq->mapping, rreq->netfs_priv);
 	trace_netfs_rreq(rreq, netfs_rreq_trace_free);
@@ -93,10 +95,10 @@ static void netfs_free_read_request(struct work_struct *work)
 	netfs_stat_d(&netfs_n_rh_rreq);
 }
 
-static void netfs_put_read_request(struct netfs_read_request *rreq)
+static void netfs_put_read_request(struct netfs_read_request *rreq, bool was_async)
 {
 	if (refcount_dec_and_test(&rreq->usage)) {
-		if (in_softirq()) {
+		if (was_async) {
 			rreq->work.func = netfs_free_read_request;
 			if (!queue_work(system_unbound_wq, &rreq->work))
 				BUG();
@@ -131,12 +133,15 @@ static void netfs_get_read_subrequest(struct netfs_read_subrequest *subreq)
 	refcount_inc(&subreq->usage);
 }
 
-static void __netfs_put_subrequest(struct netfs_read_subrequest *subreq)
+static void __netfs_put_subrequest(struct netfs_read_subrequest *subreq,
+				   bool was_async)
 {
+	struct netfs_read_request *rreq = subreq->rreq;
+
 	trace_netfs_sreq(subreq, netfs_sreq_trace_free);
-	netfs_put_read_request(subreq->rreq);
 	kfree(subreq);
 	netfs_stat_d(&netfs_n_rh_sreq);
+	netfs_put_read_request(rreq, was_async);
 }
 
 /*
@@ -152,11 +157,12 @@ static void netfs_clear_unread(struct netfs_read_subrequest *subreq)
 	iov_iter_zero(iov_iter_count(&iter), &iter);
 }
 
-static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error)
+static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error,
+					bool was_async)
 {
 	struct netfs_read_subrequest *subreq = priv;
 
-	netfs_subreq_terminated(subreq, transferred_or_error);
+	netfs_subreq_terminated(subreq, transferred_or_error, was_async);
 }
 
 /*
@@ -186,7 +192,7 @@ static void netfs_fill_with_zeroes(struct netfs_read_request *rreq,
 {
 	netfs_stat(&netfs_n_rh_zero);
 	__set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
-	netfs_subreq_terminated(subreq, 0);
+	netfs_subreq_terminated(subreq, 0, false);
 }
 
 /*
@@ -215,11 +221,11 @@ static void netfs_read_from_server(struct netfs_read_request *rreq,
 /*
  * Release those waiting.
  */
-static void netfs_rreq_completed(struct netfs_read_request *rreq)
+static void netfs_rreq_completed(struct netfs_read_request *rreq, bool was_async)
 {
 	trace_netfs_rreq(rreq, netfs_rreq_trace_done);
-	netfs_rreq_clear_subreqs(rreq);
-	netfs_put_read_request(rreq);
+	netfs_rreq_clear_subreqs(rreq, was_async);
+	netfs_put_read_request(rreq, was_async);
 }
 
 /*
@@ -228,7 +234,8 @@ static void netfs_rreq_completed(struct netfs_read_request *rreq)
  *
  * May be called in softirq mode and we inherit a ref from the caller.
  */
-static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq)
+static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq,
+					  bool was_async)
 {
 	struct netfs_read_subrequest *subreq;
 	struct pagevec pvec;
@@ -258,10 +265,11 @@ static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq)
 	}
 
 	rcu_read_unlock();
-	netfs_rreq_completed(rreq);
+	netfs_rreq_completed(rreq, was_async);
 }
 
-static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error)
+static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error,
+				       bool was_async)
 {
 	struct netfs_read_subrequest *subreq = priv;
 	struct netfs_read_request *rreq = subreq->rreq;
@@ -278,9 +286,9 @@ static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error)
 
 	/* If we decrement nr_wr_ops to 0, the ref belongs to us. */
 	if (atomic_dec_and_test(&rreq->nr_wr_ops))
-		netfs_rreq_unmark_after_write(rreq);
+		netfs_rreq_unmark_after_write(rreq, was_async);
 
-	netfs_put_subrequest(subreq);
+	netfs_put_subrequest(subreq, was_async);
 }
 
 /*
@@ -304,7 +312,7 @@ static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq)
 	list_for_each_entry_safe(subreq, p, &rreq->subrequests, rreq_link) {
 		if (!test_bit(NETFS_SREQ_WRITE_TO_CACHE, &subreq->flags)) {
 			list_del_init(&subreq->rreq_link);
-			netfs_put_subrequest(subreq);
+			netfs_put_subrequest(subreq, false);
 		}
 	}
 
@@ -324,7 +332,7 @@ static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq)
 			subreq->len += next->len;
 			subreq->len = round_up(subreq->len, PAGE_SIZE);
 			list_del_init(&next->rreq_link);
-			netfs_put_subrequest(next);
+			netfs_put_subrequest(next, false);
 		}
 
 		iov_iter_xarray(&iter, WRITE, &rreq->mapping->i_pages,
@@ -340,7 +348,7 @@ static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq)
 
 	/* If we decrement nr_wr_ops to 0, the usage ref belongs to us. */
 	if (atomic_dec_and_test(&rreq->nr_wr_ops))
-		netfs_rreq_unmark_after_write(rreq);
+		netfs_rreq_unmark_after_write(rreq, false);
 }
 
 static void netfs_rreq_write_to_cache_work(struct work_struct *work)
@@ -351,9 +359,10 @@ static void netfs_rreq_write_to_cache_work(struct work_struct *work)
 	netfs_rreq_do_write_to_cache(rreq);
 }
 
-static void netfs_rreq_write_to_cache(struct netfs_read_request *rreq)
+static void netfs_rreq_write_to_cache(struct netfs_read_request *rreq,
+				      bool was_async)
 {
-	if (in_softirq()) {
+	if (was_async) {
 		rreq->work.func = netfs_rreq_write_to_cache_work;
 		if (!queue_work(system_unbound_wq, &rreq->work))
 			BUG();
@@ -479,7 +488,7 @@ static bool netfs_rreq_perform_resubmissions(struct netfs_read_request *rreq)
 {
 	struct netfs_read_subrequest *subreq;
 
-	WARN_ON(in_softirq());
+	WARN_ON(in_interrupt());
 
 	trace_netfs_rreq(rreq, netfs_rreq_trace_resubmit);
 
@@ -538,7 +547,7 @@ static void netfs_rreq_is_still_valid(struct netfs_read_request *rreq)
  * Note that we could be in an ordinary kernel thread, on a workqueue or in
  * softirq context at this point.  We inherit a ref from the caller.
  */
-static void netfs_rreq_assess(struct netfs_read_request *rreq)
+static void netfs_rreq_assess(struct netfs_read_request *rreq, bool was_async)
 {
 	trace_netfs_rreq(rreq, netfs_rreq_trace_assess);
 
@@ -558,30 +567,31 @@ static void netfs_rreq_assess(struct netfs_read_request *rreq)
 	wake_up_bit(&rreq->flags, NETFS_RREQ_IN_PROGRESS);
 
 	if (test_bit(NETFS_RREQ_WRITE_TO_CACHE, &rreq->flags))
-		return netfs_rreq_write_to_cache(rreq);
+		return netfs_rreq_write_to_cache(rreq, was_async);
 
-	netfs_rreq_completed(rreq);
+	netfs_rreq_completed(rreq, was_async);
 }
 
 static void netfs_rreq_work(struct work_struct *work)
 {
 	struct netfs_read_request *rreq =
 		container_of(work, struct netfs_read_request, work);
-	netfs_rreq_assess(rreq);
+	netfs_rreq_assess(rreq, false);
 }
 
 /*
  * Handle the completion of all outstanding I/O operations on a read request.
  * We inherit a ref from the caller.
  */
-static void netfs_rreq_terminated(struct netfs_read_request *rreq)
+static void netfs_rreq_terminated(struct netfs_read_request *rreq,
+				  bool was_async)
 {
 	if (test_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags) &&
-	    in_softirq()) {
+	    was_async) {
 		if (!queue_work(system_unbound_wq, &rreq->work))
 			BUG();
 	} else {
-		netfs_rreq_assess(rreq);
+		netfs_rreq_assess(rreq, was_async);
 	}
 }
 
@@ -589,6 +599,7 @@ static void netfs_rreq_terminated(struct netfs_read_request *rreq)
  * netfs_subreq_terminated - Note the termination of an I/O operation.
  * @subreq: The I/O request that has terminated.
  * @transferred_or_error: The amount of data transferred or an error code.
+ * @was_async: The termination was asynchronous
  *
  * This tells the read helper that a contributory I/O operation has terminated,
  * one way or another, and that it should integrate the results.
@@ -599,11 +610,12 @@ static void netfs_rreq_terminated(struct netfs_read_request *rreq)
  * error code.  The helper will look after reissuing I/O operations as
  * appropriate and writing downloaded data to the cache.
  *
- * This may be called from a softirq handler, so we want to avoid taking the
- * spinlock if we can.
+ * If @was_async is true, the caller might be running in softirq or interrupt
+ * context and we can't sleep.
  */
 void netfs_subreq_terminated(struct netfs_read_subrequest *subreq,
-			     ssize_t transferred_or_error)
+			     ssize_t transferred_or_error,
+			     bool was_async)
 {
 	struct netfs_read_request *rreq = subreq->rreq;
 	int u;
@@ -647,11 +659,11 @@ void netfs_subreq_terminated(struct netfs_read_subrequest *subreq,
 	/* If we decrement nr_rd_ops to 0, the ref belongs to us. */
 	u = atomic_dec_return(&rreq->nr_rd_ops);
 	if (u == 0)
-		netfs_rreq_terminated(rreq);
+		netfs_rreq_terminated(rreq, was_async);
 	else if (u == 1)
 		wake_up_var(&rreq->nr_rd_ops);
 
-	netfs_put_subrequest(subreq);
+	netfs_put_subrequest(subreq, was_async);
 	return;
 
 incomplete:
@@ -796,7 +808,7 @@ static bool netfs_rreq_submit_slice(struct netfs_read_request *rreq,
 
 subreq_failed:
 	rreq->error = subreq->error;
-	netfs_put_subrequest(subreq);
+	netfs_put_subrequest(subreq, false);
 	return false;
 }
 
@@ -901,7 +913,7 @@ void netfs_readahead(struct readahead_control *ractl,
 	} while (rreq->submitted < rreq->len);
 
 	if (rreq->submitted == 0) {
-		netfs_put_read_request(rreq);
+		netfs_put_read_request(rreq, false);
 		return;
 	}
 
@@ -913,11 +925,11 @@ void netfs_readahead(struct readahead_control *ractl,
 
 	/* If we decrement nr_rd_ops to 0, the ref belongs to us. */
 	if (atomic_dec_and_test(&rreq->nr_rd_ops))
-		netfs_rreq_assess(rreq);
+		netfs_rreq_assess(rreq, false);
 	return;
 
 cleanup_free:
-	netfs_put_read_request(rreq);
+	netfs_put_read_request(rreq, false);
 	return;
 cleanup:
 	if (netfs_priv)
@@ -991,14 +1003,14 @@ int netfs_readpage(struct file *file,
 	 */
 	do {
 		wait_var_event(&rreq->nr_rd_ops, atomic_read(&rreq->nr_rd_ops) == 1);
-		netfs_rreq_assess(rreq);
+		netfs_rreq_assess(rreq, false);
 	} while (test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags));
 
 	ret = rreq->error;
 	if (ret == 0 && rreq->submitted < rreq->len)
 		ret = -EIO;
 out:
-	netfs_put_read_request(rreq);
+	netfs_put_read_request(rreq, false);
 	return ret;
 }
 EXPORT_SYMBOL(netfs_readpage);
@@ -1136,7 +1148,7 @@ int netfs_write_begin(struct file *file, struct address_space *mapping,
 	 */
 	for (;;) {
 		wait_var_event(&rreq->nr_rd_ops, atomic_read(&rreq->nr_rd_ops) == 1);
-		netfs_rreq_assess(rreq);
+		netfs_rreq_assess(rreq, false);
 		if (!test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags))
 			break;
 		cond_resched();
@@ -1145,7 +1157,7 @@ int netfs_write_begin(struct file *file, struct address_space *mapping,
 	ret = rreq->error;
 	if (ret == 0 && rreq->submitted < rreq->len)
 		ret = -EIO;
-	netfs_put_read_request(rreq);
+	netfs_put_read_request(rreq, false);
 	if (ret < 0)
 		goto error;
 
diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index b2589b39feb8..c22b64db237d 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -60,7 +60,8 @@ enum netfs_read_source {
 	NETFS_INVALID_READ,
 } __mode(byte);
 
-typedef void (*netfs_io_terminated_t)(void *priv, ssize_t transferred_or_error);
+typedef void (*netfs_io_terminated_t)(void *priv, ssize_t transferred_or_error,
+				      bool was_async);
 
 /*
  * Resources required to do operations on a cache.
@@ -189,7 +190,7 @@ extern int netfs_write_begin(struct file *, struct address_space *,
 			     const struct netfs_read_request_ops *,
 			     void *);
 
-extern void netfs_subreq_terminated(struct netfs_read_subrequest *, ssize_t);
+extern void netfs_subreq_terminated(struct netfs_read_subrequest *, ssize_t, bool);
 extern void netfs_stats_show(struct seq_file *);
 
 #endif /* _LINUX_NETFS_H */

Re: [PATCH 34/33] netfs: Pass flag rather than use in_softirq()

[Marc Dionne]

On Thu, Feb 18, 2021 at 10:03 AM David Howells <dhowells@redhat.com> wrote:
>
> Christoph Hellwig <hch@lst.de> wrote:
>
> > On Tue, Feb 16, 2021 at 09:29:31AM +0000, David Howells wrote:
> > > Is there a better way to do it?  The intent is to process the assessment
> > > phase in the calling thread's context if possible rather than bumping over
> > > to a worker thread.  For synchronous I/O, for example, that's done in the
> > > caller's thread.  Maybe that's the answer - if it's known to be
> > > asynchronous, I have to punt, but otherwise don't have to.
> >
> > Yes, i think you want an explicit flag instead.
>
> How about the attached instead?
>
> David
> ---
> commit 29b3e9eed616db01f15c7998c062b4e501ea6582
> Author: David Howells <dhowells@redhat.com>
> Date:   Mon Feb 15 21:56:43 2021 +0000
>
>     netfs: Pass flag rather than use in_softirq()
>
>     The in_softirq() in netfs_rreq_terminated() works fine for the cache being
>     on a normal disk, as the completion handlers may get called in softirq
>     context, but for an NVMe drive, the completion handler may get called in
>     IRQ context.
>
>     Fix to pass a flag to netfs_subreq_terminated() to indicate whether we
>     think the function isn't being called from a context in which we can do
>     allocations, waits and I/O submissions (such as softirq or interrupt
>     context).  If this flag is set, netfs lib has to punt to a worker thread to
>     handle anything like that.
>
>     The symptom involves warnings like the following appearing and the kernel
>     hanging:
>
>      WARNING: CPU: 0 PID: 0 at kernel/softirq.c:175 __local_bh_enable_ip+0x35/0x50
>      ...
>      RIP: 0010:__local_bh_enable_ip+0x35/0x50
>      ...
>      Call Trace:
>       <IRQ>
>       rxrpc_kernel_begin_call+0x7d/0x1b0 [rxrpc]
>       ? afs_rx_new_call+0x40/0x40 [kafs]
>       ? afs_alloc_call+0x28/0x120 [kafs]
>       afs_make_call+0x120/0x510 [kafs]
>       ? afs_rx_new_call+0x40/0x40 [kafs]
>       ? afs_alloc_flat_call+0xba/0x100 [kafs]
>       ? __kmalloc+0x167/0x2f0
>       ? afs_alloc_flat_call+0x9b/0x100 [kafs]
>       afs_wait_for_operation+0x2d/0x200 [kafs]
>       afs_do_sync_operation+0x16/0x20 [kafs]
>       afs_req_issue_op+0x8c/0xb0 [kafs]
>       netfs_rreq_assess+0x125/0x7d0 [netfs]
>       ? cachefiles_end_operation+0x40/0x40 [cachefiles]
>       netfs_subreq_terminated+0x117/0x220 [netfs]
>       cachefiles_read_complete+0x21/0x60 [cachefiles]
>       iomap_dio_bio_end_io+0xdd/0x110
>       blk_update_request+0x20a/0x380
>       blk_mq_end_request+0x1c/0x120
>       nvme_process_cq+0x159/0x1f0 [nvme]
>       nvme_irq+0x10/0x20 [nvme]
>       __handle_irq_event_percpu+0x37/0x150
>       handle_irq_event+0x49/0xb0
>       handle_edge_irq+0x7c/0x200
>       asm_call_irq_on_stack+0xf/0x20
>       </IRQ>
>       common_interrupt+0xad/0x120
>       asm_common_interrupt+0x1e/0x40
>      ...
>
>     Reported-by: Marc Dionne <marc.dionne@auristor.com>
>     Signed-off-by: David Howells <dhowells@redhat.com>
>     cc: Matthew Wilcox <willy@infradead.org>
>     cc: linux-mm@kvack.org
>     cc: linux-cachefs@redhat.com
>     cc: linux-afs@lists.infradead.org
>     cc: linux-nfs@vger.kernel.org
>     cc: linux-cifs@vger.kernel.org
>     cc: ceph-devel@vger.kernel.org
>     cc: v9fs-developer@lists.sourceforge.net
>     cc: linux-fsdevel@vger.kernel.org
>
> diff --git a/fs/afs/file.c b/fs/afs/file.c
> index 8f28d4f4cfd7..6dcdbbfb48e2 100644
> --- a/fs/afs/file.c
> +++ b/fs/afs/file.c
> @@ -223,7 +223,7 @@ static void afs_fetch_data_notify(struct afs_operation *op)
>
>         if (subreq) {
>                 __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
> -               netfs_subreq_terminated(subreq, error ?: req->actual_len);
> +               netfs_subreq_terminated(subreq, error ?: req->actual_len, false);
>                 req->subreq = NULL;
>         } else if (req->done) {
>                 req->done(req);
> @@ -289,7 +289,7 @@ static void afs_req_issue_op(struct netfs_read_subrequest *subreq)
>
>         fsreq = afs_alloc_read(GFP_NOFS);
>         if (!fsreq)
> -               return netfs_subreq_terminated(subreq, -ENOMEM);
> +               return netfs_subreq_terminated(subreq, -ENOMEM, false);
>
>         fsreq->subreq   = subreq;
>         fsreq->pos      = subreq->start + subreq->transferred;
> @@ -304,7 +304,7 @@ static void afs_req_issue_op(struct netfs_read_subrequest *subreq)
>
>         ret = afs_fetch_data(fsreq->vnode, fsreq);
>         if (ret < 0)
> -               return netfs_subreq_terminated(subreq, ret);
> +               return netfs_subreq_terminated(subreq, ret, false);
>  }
>
>  static int afs_symlink_readpage(struct page *page)
> diff --git a/fs/cachefiles/rdwr2.c b/fs/cachefiles/rdwr2.c
> index 4cea5a2a2d6e..40668bfe6688 100644
> --- a/fs/cachefiles/rdwr2.c
> +++ b/fs/cachefiles/rdwr2.c
> @@ -23,6 +23,7 @@ struct cachefiles_kiocb {
>         };
>         netfs_io_terminated_t   term_func;
>         void                    *term_func_priv;
> +       bool                    was_async;
>  };
>
>  static inline void cachefiles_put_kiocb(struct cachefiles_kiocb *ki)
> @@ -43,10 +44,9 @@ static void cachefiles_read_complete(struct kiocb *iocb, long ret, long ret2)
>         _enter("%ld,%ld", ret, ret2);
>
>         if (ki->term_func) {
> -               if (ret < 0)
> -                       ki->term_func(ki->term_func_priv, ret);
> -               else
> -                       ki->term_func(ki->term_func_priv, ki->skipped + ret);
> +               if (ret >= 0)
> +                       ret += ki->skipped;
> +               ki->term_func(ki->term_func_priv, ret, ki->was_async);
>         }
>
>         cachefiles_put_kiocb(ki);
> @@ -114,6 +114,7 @@ static int cachefiles_read(struct netfs_cache_resources *cres,
>         ki->skipped             = skipped;
>         ki->term_func           = term_func;
>         ki->term_func_priv      = term_func_priv;
> +       ki->was_async           = true;
>
>         if (ki->term_func)
>                 ki->iocb.ki_complete = cachefiles_read_complete;
> @@ -141,6 +142,7 @@ static int cachefiles_read(struct netfs_cache_resources *cres,
>                 ret = -EINTR;
>                 fallthrough;
>         default:
> +               ki->was_async = false;
>                 cachefiles_read_complete(&ki->iocb, ret, 0);
>                 if (ret > 0)
>                         ret = 0;
> @@ -156,7 +158,7 @@ static int cachefiles_read(struct netfs_cache_resources *cres,
>         kfree(ki);
>  presubmission_error:
>         if (term_func)
> -               term_func(term_func_priv, ret < 0 ? ret : skipped);
> +               term_func(term_func_priv, ret < 0 ? ret : skipped, false);
>         return ret;
>  }
>
> @@ -175,7 +177,7 @@ static void cachefiles_write_complete(struct kiocb *iocb, long ret, long ret2)
>         __sb_end_write(inode->i_sb, SB_FREEZE_WRITE);
>
>         if (ki->term_func)
> -               ki->term_func(ki->term_func_priv, ret);
> +               ki->term_func(ki->term_func_priv, ret, ki->was_async);
>
>         cachefiles_put_kiocb(ki);
>  }
> @@ -214,6 +216,7 @@ static int cachefiles_write(struct netfs_cache_resources *cres,
>         ki->len                 = len;
>         ki->term_func           = term_func;
>         ki->term_func_priv      = term_func_priv;
> +       ki->was_async           = true;
>
>         if (ki->term_func)
>                 ki->iocb.ki_complete = cachefiles_write_complete;
> @@ -250,6 +253,7 @@ static int cachefiles_write(struct netfs_cache_resources *cres,
>                 ret = -EINTR;
>                 /* Fall through */
>         default:
> +               ki->was_async = false;
>                 cachefiles_write_complete(&ki->iocb, ret, 0);
>                 if (ret > 0)
>                         ret = 0;
> @@ -265,7 +269,7 @@ static int cachefiles_write(struct netfs_cache_resources *cres,
>         kfree(ki);
>  presubmission_error:
>         if (term_func)
> -               term_func(term_func_priv, -ENOMEM);
> +               term_func(term_func_priv, -ENOMEM, false);
>         return -ENOMEM;
>  }
>
> diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
> index 0dd64d31eff6..dcfd805d168e 100644
> --- a/fs/ceph/addr.c
> +++ b/fs/ceph/addr.c
> @@ -221,7 +221,7 @@ static void finish_netfs_read(struct ceph_osd_request *req)
>         if (err >= 0 && err < subreq->len)
>                 __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
>
> -       netfs_subreq_terminated(subreq, err);
> +       netfs_subreq_terminated(subreq, err, true);
>
>         num_pages = calc_pages_for(osd_data->alignment, osd_data->length);
>         ceph_put_page_vector(osd_data->pages, num_pages, false);
> @@ -276,7 +276,7 @@ static void ceph_netfs_issue_op(struct netfs_read_subrequest *subreq)
>  out:
>         ceph_osdc_put_request(req);
>         if (err)
> -               netfs_subreq_terminated(subreq, err);
> +               netfs_subreq_terminated(subreq, err, false);
>         dout("%s: result %d\n", __func__, err);
>  }
>
> diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c
> index 9191a3617d91..5f5de8278499 100644
> --- a/fs/netfs/read_helper.c
> +++ b/fs/netfs/read_helper.c
> @@ -29,12 +29,13 @@ module_param_named(debug, netfs_debug, uint, S_IWUSR | S_IRUGO);
>  MODULE_PARM_DESC(netfs_debug, "Netfs support debugging mask");
>
>  static void netfs_rreq_work(struct work_struct *);
> -static void __netfs_put_subrequest(struct netfs_read_subrequest *);
> +static void __netfs_put_subrequest(struct netfs_read_subrequest *, bool);
>
> -static void netfs_put_subrequest(struct netfs_read_subrequest *subreq)
> +static void netfs_put_subrequest(struct netfs_read_subrequest *subreq,
> +                                bool was_async)
>  {
>         if (refcount_dec_and_test(&subreq->usage))
> -               __netfs_put_subrequest(subreq);
> +               __netfs_put_subrequest(subreq, was_async);
>  }
>
>  static struct netfs_read_request *netfs_alloc_read_request(
> @@ -67,7 +68,8 @@ static void netfs_get_read_request(struct netfs_read_request *rreq)
>         refcount_inc(&rreq->usage);
>  }
>
> -static void netfs_rreq_clear_subreqs(struct netfs_read_request *rreq)
> +static void netfs_rreq_clear_subreqs(struct netfs_read_request *rreq,
> +                                    bool was_async)
>  {
>         struct netfs_read_subrequest *subreq;
>
> @@ -75,7 +77,7 @@ static void netfs_rreq_clear_subreqs(struct netfs_read_request *rreq)
>                 subreq = list_first_entry(&rreq->subrequests,
>                                           struct netfs_read_subrequest, rreq_link);
>                 list_del(&subreq->rreq_link);
> -               netfs_put_subrequest(subreq);
> +               netfs_put_subrequest(subreq, was_async);
>         }
>  }
>
> @@ -83,7 +85,7 @@ static void netfs_free_read_request(struct work_struct *work)
>  {
>         struct netfs_read_request *rreq =
>                 container_of(work, struct netfs_read_request, work);
> -       netfs_rreq_clear_subreqs(rreq);
> +       netfs_rreq_clear_subreqs(rreq, false);
>         if (rreq->netfs_priv)
>                 rreq->netfs_ops->cleanup(rreq->mapping, rreq->netfs_priv);
>         trace_netfs_rreq(rreq, netfs_rreq_trace_free);
> @@ -93,10 +95,10 @@ static void netfs_free_read_request(struct work_struct *work)
>         netfs_stat_d(&netfs_n_rh_rreq);
>  }
>
> -static void netfs_put_read_request(struct netfs_read_request *rreq)
> +static void netfs_put_read_request(struct netfs_read_request *rreq, bool was_async)
>  {
>         if (refcount_dec_and_test(&rreq->usage)) {
> -               if (in_softirq()) {
> +               if (was_async) {
>                         rreq->work.func = netfs_free_read_request;
>                         if (!queue_work(system_unbound_wq, &rreq->work))
>                                 BUG();
> @@ -131,12 +133,15 @@ static void netfs_get_read_subrequest(struct netfs_read_subrequest *subreq)
>         refcount_inc(&subreq->usage);
>  }
>
> -static void __netfs_put_subrequest(struct netfs_read_subrequest *subreq)
> +static void __netfs_put_subrequest(struct netfs_read_subrequest *subreq,
> +                                  bool was_async)
>  {
> +       struct netfs_read_request *rreq = subreq->rreq;
> +
>         trace_netfs_sreq(subreq, netfs_sreq_trace_free);
> -       netfs_put_read_request(subreq->rreq);
>         kfree(subreq);
>         netfs_stat_d(&netfs_n_rh_sreq);
> +       netfs_put_read_request(rreq, was_async);
>  }
>
>  /*
> @@ -152,11 +157,12 @@ static void netfs_clear_unread(struct netfs_read_subrequest *subreq)
>         iov_iter_zero(iov_iter_count(&iter), &iter);
>  }
>
> -static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error)
> +static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error,
> +                                       bool was_async)
>  {
>         struct netfs_read_subrequest *subreq = priv;
>
> -       netfs_subreq_terminated(subreq, transferred_or_error);
> +       netfs_subreq_terminated(subreq, transferred_or_error, was_async);
>  }
>
>  /*
> @@ -186,7 +192,7 @@ static void netfs_fill_with_zeroes(struct netfs_read_request *rreq,
>  {
>         netfs_stat(&netfs_n_rh_zero);
>         __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
> -       netfs_subreq_terminated(subreq, 0);
> +       netfs_subreq_terminated(subreq, 0, false);
>  }
>
>  /*
> @@ -215,11 +221,11 @@ static void netfs_read_from_server(struct netfs_read_request *rreq,
>  /*
>   * Release those waiting.
>   */
> -static void netfs_rreq_completed(struct netfs_read_request *rreq)
> +static void netfs_rreq_completed(struct netfs_read_request *rreq, bool was_async)
>  {
>         trace_netfs_rreq(rreq, netfs_rreq_trace_done);
> -       netfs_rreq_clear_subreqs(rreq);
> -       netfs_put_read_request(rreq);
> +       netfs_rreq_clear_subreqs(rreq, was_async);
> +       netfs_put_read_request(rreq, was_async);
>  }
>
>  /*
> @@ -228,7 +234,8 @@ static void netfs_rreq_completed(struct netfs_read_request *rreq)
>   *
>   * May be called in softirq mode and we inherit a ref from the caller.
>   */
> -static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq)
> +static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq,
> +                                         bool was_async)
>  {
>         struct netfs_read_subrequest *subreq;
>         struct pagevec pvec;
> @@ -258,10 +265,11 @@ static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq)
>         }
>
>         rcu_read_unlock();
> -       netfs_rreq_completed(rreq);
> +       netfs_rreq_completed(rreq, was_async);
>  }
>
> -static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error)
> +static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error,
> +                                      bool was_async)
>  {
>         struct netfs_read_subrequest *subreq = priv;
>         struct netfs_read_request *rreq = subreq->rreq;
> @@ -278,9 +286,9 @@ static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error)
>
>         /* If we decrement nr_wr_ops to 0, the ref belongs to us. */
>         if (atomic_dec_and_test(&rreq->nr_wr_ops))
> -               netfs_rreq_unmark_after_write(rreq);
> +               netfs_rreq_unmark_after_write(rreq, was_async);
>
> -       netfs_put_subrequest(subreq);
> +       netfs_put_subrequest(subreq, was_async);
>  }
>
>  /*
> @@ -304,7 +312,7 @@ static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq)
>         list_for_each_entry_safe(subreq, p, &rreq->subrequests, rreq_link) {
>                 if (!test_bit(NETFS_SREQ_WRITE_TO_CACHE, &subreq->flags)) {
>                         list_del_init(&subreq->rreq_link);
> -                       netfs_put_subrequest(subreq);
> +                       netfs_put_subrequest(subreq, false);
>                 }
>         }
>
> @@ -324,7 +332,7 @@ static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq)
>                         subreq->len += next->len;
>                         subreq->len = round_up(subreq->len, PAGE_SIZE);
>                         list_del_init(&next->rreq_link);
> -                       netfs_put_subrequest(next);
> +                       netfs_put_subrequest(next, false);
>                 }
>
>                 iov_iter_xarray(&iter, WRITE, &rreq->mapping->i_pages,
> @@ -340,7 +348,7 @@ static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq)
>
>         /* If we decrement nr_wr_ops to 0, the usage ref belongs to us. */
>         if (atomic_dec_and_test(&rreq->nr_wr_ops))
> -               netfs_rreq_unmark_after_write(rreq);
> +               netfs_rreq_unmark_after_write(rreq, false);
>  }
>
>  static void netfs_rreq_write_to_cache_work(struct work_struct *work)
> @@ -351,9 +359,10 @@ static void netfs_rreq_write_to_cache_work(struct work_struct *work)
>         netfs_rreq_do_write_to_cache(rreq);
>  }
>
> -static void netfs_rreq_write_to_cache(struct netfs_read_request *rreq)
> +static void netfs_rreq_write_to_cache(struct netfs_read_request *rreq,
> +                                     bool was_async)
>  {
> -       if (in_softirq()) {
> +       if (was_async) {
>                 rreq->work.func = netfs_rreq_write_to_cache_work;
>                 if (!queue_work(system_unbound_wq, &rreq->work))
>                         BUG();
> @@ -479,7 +488,7 @@ static bool netfs_rreq_perform_resubmissions(struct netfs_read_request *rreq)
>  {
>         struct netfs_read_subrequest *subreq;
>
> -       WARN_ON(in_softirq());
> +       WARN_ON(in_interrupt());
>
>         trace_netfs_rreq(rreq, netfs_rreq_trace_resubmit);
>
> @@ -538,7 +547,7 @@ static void netfs_rreq_is_still_valid(struct netfs_read_request *rreq)
>   * Note that we could be in an ordinary kernel thread, on a workqueue or in
>   * softirq context at this point.  We inherit a ref from the caller.
>   */
> -static void netfs_rreq_assess(struct netfs_read_request *rreq)
> +static void netfs_rreq_assess(struct netfs_read_request *rreq, bool was_async)
>  {
>         trace_netfs_rreq(rreq, netfs_rreq_trace_assess);
>
> @@ -558,30 +567,31 @@ static void netfs_rreq_assess(struct netfs_read_request *rreq)
>         wake_up_bit(&rreq->flags, NETFS_RREQ_IN_PROGRESS);
>
>         if (test_bit(NETFS_RREQ_WRITE_TO_CACHE, &rreq->flags))
> -               return netfs_rreq_write_to_cache(rreq);
> +               return netfs_rreq_write_to_cache(rreq, was_async);
>
> -       netfs_rreq_completed(rreq);
> +       netfs_rreq_completed(rreq, was_async);
>  }
>
>  static void netfs_rreq_work(struct work_struct *work)
>  {
>         struct netfs_read_request *rreq =
>                 container_of(work, struct netfs_read_request, work);
> -       netfs_rreq_assess(rreq);
> +       netfs_rreq_assess(rreq, false);
>  }
>
>  /*
>   * Handle the completion of all outstanding I/O operations on a read request.
>   * We inherit a ref from the caller.
>   */
> -static void netfs_rreq_terminated(struct netfs_read_request *rreq)
> +static void netfs_rreq_terminated(struct netfs_read_request *rreq,
> +                                 bool was_async)
>  {
>         if (test_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags) &&
> -           in_softirq()) {
> +           was_async) {
>                 if (!queue_work(system_unbound_wq, &rreq->work))
>                         BUG();
>         } else {
> -               netfs_rreq_assess(rreq);
> +               netfs_rreq_assess(rreq, was_async);
>         }
>  }
>
> @@ -589,6 +599,7 @@ static void netfs_rreq_terminated(struct netfs_read_request *rreq)
>   * netfs_subreq_terminated - Note the termination of an I/O operation.
>   * @subreq: The I/O request that has terminated.
>   * @transferred_or_error: The amount of data transferred or an error code.
> + * @was_async: The termination was asynchronous
>   *
>   * This tells the read helper that a contributory I/O operation has terminated,
>   * one way or another, and that it should integrate the results.
> @@ -599,11 +610,12 @@ static void netfs_rreq_terminated(struct netfs_read_request *rreq)
>   * error code.  The helper will look after reissuing I/O operations as
>   * appropriate and writing downloaded data to the cache.
>   *
> - * This may be called from a softirq handler, so we want to avoid taking the
> - * spinlock if we can.
> + * If @was_async is true, the caller might be running in softirq or interrupt
> + * context and we can't sleep.
>   */
>  void netfs_subreq_terminated(struct netfs_read_subrequest *subreq,
> -                            ssize_t transferred_or_error)
> +                            ssize_t transferred_or_error,
> +                            bool was_async)
>  {
>         struct netfs_read_request *rreq = subreq->rreq;
>         int u;
> @@ -647,11 +659,11 @@ void netfs_subreq_terminated(struct netfs_read_subrequest *subreq,
>         /* If we decrement nr_rd_ops to 0, the ref belongs to us. */
>         u = atomic_dec_return(&rreq->nr_rd_ops);
>         if (u == 0)
> -               netfs_rreq_terminated(rreq);
> +               netfs_rreq_terminated(rreq, was_async);
>         else if (u == 1)
>                 wake_up_var(&rreq->nr_rd_ops);
>
> -       netfs_put_subrequest(subreq);
> +       netfs_put_subrequest(subreq, was_async);
>         return;
>
>  incomplete:
> @@ -796,7 +808,7 @@ static bool netfs_rreq_submit_slice(struct netfs_read_request *rreq,
>
>  subreq_failed:
>         rreq->error = subreq->error;
> -       netfs_put_subrequest(subreq);
> +       netfs_put_subrequest(subreq, false);
>         return false;
>  }
>
> @@ -901,7 +913,7 @@ void netfs_readahead(struct readahead_control *ractl,
>         } while (rreq->submitted < rreq->len);
>
>         if (rreq->submitted == 0) {
> -               netfs_put_read_request(rreq);
> +               netfs_put_read_request(rreq, false);
>                 return;
>         }
>
> @@ -913,11 +925,11 @@ void netfs_readahead(struct readahead_control *ractl,
>
>         /* If we decrement nr_rd_ops to 0, the ref belongs to us. */
>         if (atomic_dec_and_test(&rreq->nr_rd_ops))
> -               netfs_rreq_assess(rreq);
> +               netfs_rreq_assess(rreq, false);
>         return;
>
>  cleanup_free:
> -       netfs_put_read_request(rreq);
> +       netfs_put_read_request(rreq, false);
>         return;
>  cleanup:
>         if (netfs_priv)
> @@ -991,14 +1003,14 @@ int netfs_readpage(struct file *file,
>          */
>         do {
>                 wait_var_event(&rreq->nr_rd_ops, atomic_read(&rreq->nr_rd_ops) == 1);
> -               netfs_rreq_assess(rreq);
> +               netfs_rreq_assess(rreq, false);
>         } while (test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags));
>
>         ret = rreq->error;
>         if (ret == 0 && rreq->submitted < rreq->len)
>                 ret = -EIO;
>  out:
> -       netfs_put_read_request(rreq);
> +       netfs_put_read_request(rreq, false);
>         return ret;
>  }
>  EXPORT_SYMBOL(netfs_readpage);
> @@ -1136,7 +1148,7 @@ int netfs_write_begin(struct file *file, struct address_space *mapping,
>          */
>         for (;;) {
>                 wait_var_event(&rreq->nr_rd_ops, atomic_read(&rreq->nr_rd_ops) == 1);
> -               netfs_rreq_assess(rreq);
> +               netfs_rreq_assess(rreq, false);
>                 if (!test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags))
>                         break;
>                 cond_resched();
> @@ -1145,7 +1157,7 @@ int netfs_write_begin(struct file *file, struct address_space *mapping,
>         ret = rreq->error;
>         if (ret == 0 && rreq->submitted < rreq->len)
>                 ret = -EIO;
> -       netfs_put_read_request(rreq);
> +       netfs_put_read_request(rreq, false);
>         if (ret < 0)
>                 goto error;
>
> diff --git a/include/linux/netfs.h b/include/linux/netfs.h
> index b2589b39feb8..c22b64db237d 100644
> --- a/include/linux/netfs.h
> +++ b/include/linux/netfs.h
> @@ -60,7 +60,8 @@ enum netfs_read_source {
>         NETFS_INVALID_READ,
>  } __mode(byte);
>
> -typedef void (*netfs_io_terminated_t)(void *priv, ssize_t transferred_or_error);
> +typedef void (*netfs_io_terminated_t)(void *priv, ssize_t transferred_or_error,
> +                                     bool was_async);
>
>  /*
>   * Resources required to do operations on a cache.
> @@ -189,7 +190,7 @@ extern int netfs_write_begin(struct file *, struct address_space *,
>                              const struct netfs_read_request_ops *,
>                              void *);
>
> -extern void netfs_subreq_terminated(struct netfs_read_subrequest *, ssize_t);
> +extern void netfs_subreq_terminated(struct netfs_read_subrequest *, ssize_t, bool);
>  extern void netfs_stats_show(struct seq_file *);
>
>  #endif /* _LINUX_NETFS_H */
>
>

Looks good in testing.

Tested-by: Marc Dionne <marc.dionne@auristor.com>

Re: [PATCH 34/33] netfs: Pass flag rather than use in_softirq()

[Marc Dionne]

On Thu, Feb 18, 2021 at 10:03 AM David Howells <dhowells@redhat.com> wrote:
>
> Christoph Hellwig <hch@lst.de> wrote:
>
> > On Tue, Feb 16, 2021 at 09:29:31AM +0000, David Howells wrote:
> > > Is there a better way to do it?  The intent is to process the assessment
> > > phase in the calling thread's context if possible rather than bumping over
> > > to a worker thread.  For synchronous I/O, for example, that's done in the
> > > caller's thread.  Maybe that's the answer - if it's known to be
> > > asynchronous, I have to punt, but otherwise don't have to.
> >
> > Yes, i think you want an explicit flag instead.
>
> How about the attached instead?
>
> David
> ---
> commit 29b3e9eed616db01f15c7998c062b4e501ea6582
> Author: David Howells <dhowells@redhat.com>
> Date:   Mon Feb 15 21:56:43 2021 +0000
>
>     netfs: Pass flag rather than use in_softirq()
>
>     The in_softirq() in netfs_rreq_terminated() works fine for the cache being
>     on a normal disk, as the completion handlers may get called in softirq
>     context, but for an NVMe drive, the completion handler may get called in
>     IRQ context.
>
>     Fix to pass a flag to netfs_subreq_terminated() to indicate whether we
>     think the function isn't being called from a context in which we can do
>     allocations, waits and I/O submissions (such as softirq or interrupt
>     context).  If this flag is set, netfs lib has to punt to a worker thread to
>     handle anything like that.
>
>     The symptom involves warnings like the following appearing and the kernel
>     hanging:
>
>      WARNING: CPU: 0 PID: 0 at kernel/softirq.c:175 __local_bh_enable_ip+0x35/0x50
>      ...
>      RIP: 0010:__local_bh_enable_ip+0x35/0x50
>      ...
>      Call Trace:
>       <IRQ>
>       rxrpc_kernel_begin_call+0x7d/0x1b0 [rxrpc]
>       ? afs_rx_new_call+0x40/0x40 [kafs]
>       ? afs_alloc_call+0x28/0x120 [kafs]
>       afs_make_call+0x120/0x510 [kafs]
>       ? afs_rx_new_call+0x40/0x40 [kafs]
>       ? afs_alloc_flat_call+0xba/0x100 [kafs]
>       ? __kmalloc+0x167/0x2f0
>       ? afs_alloc_flat_call+0x9b/0x100 [kafs]
>       afs_wait_for_operation+0x2d/0x200 [kafs]
>       afs_do_sync_operation+0x16/0x20 [kafs]
>       afs_req_issue_op+0x8c/0xb0 [kafs]
>       netfs_rreq_assess+0x125/0x7d0 [netfs]
>       ? cachefiles_end_operation+0x40/0x40 [cachefiles]
>       netfs_subreq_terminated+0x117/0x220 [netfs]
>       cachefiles_read_complete+0x21/0x60 [cachefiles]
>       iomap_dio_bio_end_io+0xdd/0x110
>       blk_update_request+0x20a/0x380
>       blk_mq_end_request+0x1c/0x120
>       nvme_process_cq+0x159/0x1f0 [nvme]
>       nvme_irq+0x10/0x20 [nvme]
>       __handle_irq_event_percpu+0x37/0x150
>       handle_irq_event+0x49/0xb0
>       handle_edge_irq+0x7c/0x200
>       asm_call_irq_on_stack+0xf/0x20
>       </IRQ>
>       common_interrupt+0xad/0x120
>       asm_common_interrupt+0x1e/0x40
>      ...
>
>     Reported-by: Marc Dionne <marc.dionne@auristor.com>
>     Signed-off-by: David Howells <dhowells@redhat.com>
>     cc: Matthew Wilcox <willy@infradead.org>
>     cc: linux-mm@kvack.org
>     cc: linux-cachefs@redhat.com
>     cc: linux-afs@lists.infradead.org
>     cc: linux-nfs@vger.kernel.org
>     cc: linux-cifs@vger.kernel.org
>     cc: ceph-devel@vger.kernel.org
>     cc: v9fs-developer@lists.sourceforge.net
>     cc: linux-fsdevel@vger.kernel.org
>
> diff --git a/fs/afs/file.c b/fs/afs/file.c
> index 8f28d4f4cfd7..6dcdbbfb48e2 100644
> --- a/fs/afs/file.c
> +++ b/fs/afs/file.c
> @@ -223,7 +223,7 @@ static void afs_fetch_data_notify(struct afs_operation *op)
>
>         if (subreq) {
>                 __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
> -               netfs_subreq_terminated(subreq, error ?: req->actual_len);
> +               netfs_subreq_terminated(subreq, error ?: req->actual_len, false);
>                 req->subreq = NULL;
>         } else if (req->done) {
>                 req->done(req);
> @@ -289,7 +289,7 @@ static void afs_req_issue_op(struct netfs_read_subrequest *subreq)
>
>         fsreq = afs_alloc_read(GFP_NOFS);
>         if (!fsreq)
> -               return netfs_subreq_terminated(subreq, -ENOMEM);
> +               return netfs_subreq_terminated(subreq, -ENOMEM, false);
>
>         fsreq->subreq   = subreq;
>         fsreq->pos      = subreq->start + subreq->transferred;
> @@ -304,7 +304,7 @@ static void afs_req_issue_op(struct netfs_read_subrequest *subreq)
>
>         ret = afs_fetch_data(fsreq->vnode, fsreq);
>         if (ret < 0)
> -               return netfs_subreq_terminated(subreq, ret);
> +               return netfs_subreq_terminated(subreq, ret, false);
>  }
>
>  static int afs_symlink_readpage(struct page *page)
> diff --git a/fs/cachefiles/rdwr2.c b/fs/cachefiles/rdwr2.c
> index 4cea5a2a2d6e..40668bfe6688 100644
> --- a/fs/cachefiles/rdwr2.c
> +++ b/fs/cachefiles/rdwr2.c
> @@ -23,6 +23,7 @@ struct cachefiles_kiocb {
>         };
>         netfs_io_terminated_t   term_func;
>         void                    *term_func_priv;
> +       bool                    was_async;
>  };
>
>  static inline void cachefiles_put_kiocb(struct cachefiles_kiocb *ki)
> @@ -43,10 +44,9 @@ static void cachefiles_read_complete(struct kiocb *iocb, long ret, long ret2)
>         _enter("%ld,%ld", ret, ret2);
>
>         if (ki->term_func) {
> -               if (ret < 0)
> -                       ki->term_func(ki->term_func_priv, ret);
> -               else
> -                       ki->term_func(ki->term_func_priv, ki->skipped + ret);
> +               if (ret >= 0)
> +                       ret += ki->skipped;
> +               ki->term_func(ki->term_func_priv, ret, ki->was_async);
>         }
>
>         cachefiles_put_kiocb(ki);
> @@ -114,6 +114,7 @@ static int cachefiles_read(struct netfs_cache_resources *cres,
>         ki->skipped             = skipped;
>         ki->term_func           = term_func;
>         ki->term_func_priv      = term_func_priv;
> +       ki->was_async           = true;
>
>         if (ki->term_func)
>                 ki->iocb.ki_complete = cachefiles_read_complete;
> @@ -141,6 +142,7 @@ static int cachefiles_read(struct netfs_cache_resources *cres,
>                 ret = -EINTR;
>                 fallthrough;
>         default:
> +               ki->was_async = false;
>                 cachefiles_read_complete(&ki->iocb, ret, 0);
>                 if (ret > 0)
>                         ret = 0;
> @@ -156,7 +158,7 @@ static int cachefiles_read(struct netfs_cache_resources *cres,
>         kfree(ki);
>  presubmission_error:
>         if (term_func)
> -               term_func(term_func_priv, ret < 0 ? ret : skipped);
> +               term_func(term_func_priv, ret < 0 ? ret : skipped, false);
>         return ret;
>  }
>
> @@ -175,7 +177,7 @@ static void cachefiles_write_complete(struct kiocb *iocb, long ret, long ret2)
>         __sb_end_write(inode->i_sb, SB_FREEZE_WRITE);
>
>         if (ki->term_func)
> -               ki->term_func(ki->term_func_priv, ret);
> +               ki->term_func(ki->term_func_priv, ret, ki->was_async);
>
>         cachefiles_put_kiocb(ki);
>  }
> @@ -214,6 +216,7 @@ static int cachefiles_write(struct netfs_cache_resources *cres,
>         ki->len                 = len;
>         ki->term_func           = term_func;
>         ki->term_func_priv      = term_func_priv;
> +       ki->was_async           = true;
>
>         if (ki->term_func)
>                 ki->iocb.ki_complete = cachefiles_write_complete;
> @@ -250,6 +253,7 @@ static int cachefiles_write(struct netfs_cache_resources *cres,
>                 ret = -EINTR;
>                 /* Fall through */
>         default:
> +               ki->was_async = false;
>                 cachefiles_write_complete(&ki->iocb, ret, 0);
>                 if (ret > 0)
>                         ret = 0;
> @@ -265,7 +269,7 @@ static int cachefiles_write(struct netfs_cache_resources *cres,
>         kfree(ki);
>  presubmission_error:
>         if (term_func)
> -               term_func(term_func_priv, -ENOMEM);
> +               term_func(term_func_priv, -ENOMEM, false);
>         return -ENOMEM;
>  }
>
> diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
> index 0dd64d31eff6..dcfd805d168e 100644
> --- a/fs/ceph/addr.c
> +++ b/fs/ceph/addr.c
> @@ -221,7 +221,7 @@ static void finish_netfs_read(struct ceph_osd_request *req)
>         if (err >= 0 && err < subreq->len)
>                 __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
>
> -       netfs_subreq_terminated(subreq, err);
> +       netfs_subreq_terminated(subreq, err, true);
>
>         num_pages = calc_pages_for(osd_data->alignment, osd_data->length);
>         ceph_put_page_vector(osd_data->pages, num_pages, false);
> @@ -276,7 +276,7 @@ static void ceph_netfs_issue_op(struct netfs_read_subrequest *subreq)
>  out:
>         ceph_osdc_put_request(req);
>         if (err)
> -               netfs_subreq_terminated(subreq, err);
> +               netfs_subreq_terminated(subreq, err, false);
>         dout("%s: result %d\n", __func__, err);
>  }
>
> diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c
> index 9191a3617d91..5f5de8278499 100644
> --- a/fs/netfs/read_helper.c
> +++ b/fs/netfs/read_helper.c
> @@ -29,12 +29,13 @@ module_param_named(debug, netfs_debug, uint, S_IWUSR | S_IRUGO);
>  MODULE_PARM_DESC(netfs_debug, "Netfs support debugging mask");
>
>  static void netfs_rreq_work(struct work_struct *);
> -static void __netfs_put_subrequest(struct netfs_read_subrequest *);
> +static void __netfs_put_subrequest(struct netfs_read_subrequest *, bool);
>
> -static void netfs_put_subrequest(struct netfs_read_subrequest *subreq)
> +static void netfs_put_subrequest(struct netfs_read_subrequest *subreq,
> +                                bool was_async)
>  {
>         if (refcount_dec_and_test(&subreq->usage))
> -               __netfs_put_subrequest(subreq);
> +               __netfs_put_subrequest(subreq, was_async);
>  }
>
>  static struct netfs_read_request *netfs_alloc_read_request(
> @@ -67,7 +68,8 @@ static void netfs_get_read_request(struct netfs_read_request *rreq)
>         refcount_inc(&rreq->usage);
>  }
>
> -static void netfs_rreq_clear_subreqs(struct netfs_read_request *rreq)
> +static void netfs_rreq_clear_subreqs(struct netfs_read_request *rreq,
> +                                    bool was_async)
>  {
>         struct netfs_read_subrequest *subreq;
>
> @@ -75,7 +77,7 @@ static void netfs_rreq_clear_subreqs(struct netfs_read_request *rreq)
>                 subreq = list_first_entry(&rreq->subrequests,
>                                           struct netfs_read_subrequest, rreq_link);
>                 list_del(&subreq->rreq_link);
> -               netfs_put_subrequest(subreq);
> +               netfs_put_subrequest(subreq, was_async);
>         }
>  }
>
> @@ -83,7 +85,7 @@ static void netfs_free_read_request(struct work_struct *work)
>  {
>         struct netfs_read_request *rreq =
>                 container_of(work, struct netfs_read_request, work);
> -       netfs_rreq_clear_subreqs(rreq);
> +       netfs_rreq_clear_subreqs(rreq, false);
>         if (rreq->netfs_priv)
>                 rreq->netfs_ops->cleanup(rreq->mapping, rreq->netfs_priv);
>         trace_netfs_rreq(rreq, netfs_rreq_trace_free);
> @@ -93,10 +95,10 @@ static void netfs_free_read_request(struct work_struct *work)
>         netfs_stat_d(&netfs_n_rh_rreq);
>  }
>
> -static void netfs_put_read_request(struct netfs_read_request *rreq)
> +static void netfs_put_read_request(struct netfs_read_request *rreq, bool was_async)
>  {
>         if (refcount_dec_and_test(&rreq->usage)) {
> -               if (in_softirq()) {
> +               if (was_async) {
>                         rreq->work.func = netfs_free_read_request;
>                         if (!queue_work(system_unbound_wq, &rreq->work))
>                                 BUG();
> @@ -131,12 +133,15 @@ static void netfs_get_read_subrequest(struct netfs_read_subrequest *subreq)
>         refcount_inc(&subreq->usage);
>  }
>
> -static void __netfs_put_subrequest(struct netfs_read_subrequest *subreq)
> +static void __netfs_put_subrequest(struct netfs_read_subrequest *subreq,
> +                                  bool was_async)
>  {
> +       struct netfs_read_request *rreq = subreq->rreq;
> +
>         trace_netfs_sreq(subreq, netfs_sreq_trace_free);
> -       netfs_put_read_request(subreq->rreq);
>         kfree(subreq);
>         netfs_stat_d(&netfs_n_rh_sreq);
> +       netfs_put_read_request(rreq, was_async);
>  }
>
>  /*
> @@ -152,11 +157,12 @@ static void netfs_clear_unread(struct netfs_read_subrequest *subreq)
>         iov_iter_zero(iov_iter_count(&iter), &iter);
>  }
>
> -static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error)
> +static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error,
> +                                       bool was_async)
>  {
>         struct netfs_read_subrequest *subreq = priv;
>
> -       netfs_subreq_terminated(subreq, transferred_or_error);
> +       netfs_subreq_terminated(subreq, transferred_or_error, was_async);
>  }
>
>  /*
> @@ -186,7 +192,7 @@ static void netfs_fill_with_zeroes(struct netfs_read_request *rreq,
>  {
>         netfs_stat(&netfs_n_rh_zero);
>         __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
> -       netfs_subreq_terminated(subreq, 0);
> +       netfs_subreq_terminated(subreq, 0, false);
>  }
>
>  /*
> @@ -215,11 +221,11 @@ static void netfs_read_from_server(struct netfs_read_request *rreq,
>  /*
>   * Release those waiting.
>   */
> -static void netfs_rreq_completed(struct netfs_read_request *rreq)
> +static void netfs_rreq_completed(struct netfs_read_request *rreq, bool was_async)
>  {
>         trace_netfs_rreq(rreq, netfs_rreq_trace_done);
> -       netfs_rreq_clear_subreqs(rreq);
> -       netfs_put_read_request(rreq);
> +       netfs_rreq_clear_subreqs(rreq, was_async);
> +       netfs_put_read_request(rreq, was_async);
>  }
>
>  /*
> @@ -228,7 +234,8 @@ static void netfs_rreq_completed(struct netfs_read_request *rreq)
>   *
>   * May be called in softirq mode and we inherit a ref from the caller.
>   */
> -static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq)
> +static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq,
> +                                         bool was_async)
>  {
>         struct netfs_read_subrequest *subreq;
>         struct pagevec pvec;
> @@ -258,10 +265,11 @@ static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq)
>         }
>
>         rcu_read_unlock();
> -       netfs_rreq_completed(rreq);
> +       netfs_rreq_completed(rreq, was_async);
>  }
>
> -static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error)
> +static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error,
> +                                      bool was_async)
>  {
>         struct netfs_read_subrequest *subreq = priv;
>         struct netfs_read_request *rreq = subreq->rreq;
> @@ -278,9 +286,9 @@ static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error)
>
>         /* If we decrement nr_wr_ops to 0, the ref belongs to us. */
>         if (atomic_dec_and_test(&rreq->nr_wr_ops))
> -               netfs_rreq_unmark_after_write(rreq);
> +               netfs_rreq_unmark_after_write(rreq, was_async);
>
> -       netfs_put_subrequest(subreq);
> +       netfs_put_subrequest(subreq, was_async);
>  }
>
>  /*
> @@ -304,7 +312,7 @@ static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq)
>         list_for_each_entry_safe(subreq, p, &rreq->subrequests, rreq_link) {
>                 if (!test_bit(NETFS_SREQ_WRITE_TO_CACHE, &subreq->flags)) {
>                         list_del_init(&subreq->rreq_link);
> -                       netfs_put_subrequest(subreq);
> +                       netfs_put_subrequest(subreq, false);
>                 }
>         }
>
> @@ -324,7 +332,7 @@ static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq)
>                         subreq->len += next->len;
>                         subreq->len = round_up(subreq->len, PAGE_SIZE);
>                         list_del_init(&next->rreq_link);
> -                       netfs_put_subrequest(next);
> +                       netfs_put_subrequest(next, false);
>                 }
>
>                 iov_iter_xarray(&iter, WRITE, &rreq->mapping->i_pages,
> @@ -340,7 +348,7 @@ static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq)
>
>         /* If we decrement nr_wr_ops to 0, the usage ref belongs to us. */
>         if (atomic_dec_and_test(&rreq->nr_wr_ops))
> -               netfs_rreq_unmark_after_write(rreq);
> +               netfs_rreq_unmark_after_write(rreq, false);
>  }
>
>  static void netfs_rreq_write_to_cache_work(struct work_struct *work)
> @@ -351,9 +359,10 @@ static void netfs_rreq_write_to_cache_work(struct work_struct *work)
>         netfs_rreq_do_write_to_cache(rreq);
>  }
>
> -static void netfs_rreq_write_to_cache(struct netfs_read_request *rreq)
> +static void netfs_rreq_write_to_cache(struct netfs_read_request *rreq,
> +                                     bool was_async)
>  {
> -       if (in_softirq()) {
> +       if (was_async) {
>                 rreq->work.func = netfs_rreq_write_to_cache_work;
>                 if (!queue_work(system_unbound_wq, &rreq->work))
>                         BUG();
> @@ -479,7 +488,7 @@ static bool netfs_rreq_perform_resubmissions(struct netfs_read_request *rreq)
>  {
>         struct netfs_read_subrequest *subreq;
>
> -       WARN_ON(in_softirq());
> +       WARN_ON(in_interrupt());
>
>         trace_netfs_rreq(rreq, netfs_rreq_trace_resubmit);
>
> @@ -538,7 +547,7 @@ static void netfs_rreq_is_still_valid(struct netfs_read_request *rreq)
>   * Note that we could be in an ordinary kernel thread, on a workqueue or in
>   * softirq context at this point.  We inherit a ref from the caller.
>   */
> -static void netfs_rreq_assess(struct netfs_read_request *rreq)
> +static void netfs_rreq_assess(struct netfs_read_request *rreq, bool was_async)
>  {
>         trace_netfs_rreq(rreq, netfs_rreq_trace_assess);
>
> @@ -558,30 +567,31 @@ static void netfs_rreq_assess(struct netfs_read_request *rreq)
>         wake_up_bit(&rreq->flags, NETFS_RREQ_IN_PROGRESS);
>
>         if (test_bit(NETFS_RREQ_WRITE_TO_CACHE, &rreq->flags))
> -               return netfs_rreq_write_to_cache(rreq);
> +               return netfs_rreq_write_to_cache(rreq, was_async);
>
> -       netfs_rreq_completed(rreq);
> +       netfs_rreq_completed(rreq, was_async);
>  }
>
>  static void netfs_rreq_work(struct work_struct *work)
>  {
>         struct netfs_read_request *rreq =
>                 container_of(work, struct netfs_read_request, work);
> -       netfs_rreq_assess(rreq);
> +       netfs_rreq_assess(rreq, false);
>  }
>
>  /*
>   * Handle the completion of all outstanding I/O operations on a read request.
>   * We inherit a ref from the caller.
>   */
> -static void netfs_rreq_terminated(struct netfs_read_request *rreq)
> +static void netfs_rreq_terminated(struct netfs_read_request *rreq,
> +                                 bool was_async)
>  {
>         if (test_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags) &&
> -           in_softirq()) {
> +           was_async) {
>                 if (!queue_work(system_unbound_wq, &rreq->work))
>                         BUG();
>         } else {
> -               netfs_rreq_assess(rreq);
> +               netfs_rreq_assess(rreq, was_async);
>         }
>  }
>
> @@ -589,6 +599,7 @@ static void netfs_rreq_terminated(struct netfs_read_request *rreq)
>   * netfs_subreq_terminated - Note the termination of an I/O operation.
>   * @subreq: The I/O request that has terminated.
>   * @transferred_or_error: The amount of data transferred or an error code.
> + * @was_async: The termination was asynchronous
>   *
>   * This tells the read helper that a contributory I/O operation has terminated,
>   * one way or another, and that it should integrate the results.
> @@ -599,11 +610,12 @@ static void netfs_rreq_terminated(struct netfs_read_request *rreq)
>   * error code.  The helper will look after reissuing I/O operations as
>   * appropriate and writing downloaded data to the cache.
>   *
> - * This may be called from a softirq handler, so we want to avoid taking the
> - * spinlock if we can.
> + * If @was_async is true, the caller might be running in softirq or interrupt
> + * context and we can't sleep.
>   */
>  void netfs_subreq_terminated(struct netfs_read_subrequest *subreq,
> -                            ssize_t transferred_or_error)
> +                            ssize_t transferred_or_error,
> +                            bool was_async)
>  {
>         struct netfs_read_request *rreq = subreq->rreq;
>         int u;
> @@ -647,11 +659,11 @@ void netfs_subreq_terminated(struct netfs_read_subrequest *subreq,
>         /* If we decrement nr_rd_ops to 0, the ref belongs to us. */
>         u = atomic_dec_return(&rreq->nr_rd_ops);
>         if (u == 0)
> -               netfs_rreq_terminated(rreq);
> +               netfs_rreq_terminated(rreq, was_async);
>         else if (u == 1)
>                 wake_up_var(&rreq->nr_rd_ops);
>
> -       netfs_put_subrequest(subreq);
> +       netfs_put_subrequest(subreq, was_async);
>         return;
>
>  incomplete:
> @@ -796,7 +808,7 @@ static bool netfs_rreq_submit_slice(struct netfs_read_request *rreq,
>
>  subreq_failed:
>         rreq->error = subreq->error;
> -       netfs_put_subrequest(subreq);
> +       netfs_put_subrequest(subreq, false);
>         return false;
>  }
>
> @@ -901,7 +913,7 @@ void netfs_readahead(struct readahead_control *ractl,
>         } while (rreq->submitted < rreq->len);
>
>         if (rreq->submitted == 0) {
> -               netfs_put_read_request(rreq);
> +               netfs_put_read_request(rreq, false);
>                 return;
>         }
>
> @@ -913,11 +925,11 @@ void netfs_readahead(struct readahead_control *ractl,
>
>         /* If we decrement nr_rd_ops to 0, the ref belongs to us. */
>         if (atomic_dec_and_test(&rreq->nr_rd_ops))
> -               netfs_rreq_assess(rreq);
> +               netfs_rreq_assess(rreq, false);
>         return;
>
>  cleanup_free:
> -       netfs_put_read_request(rreq);
> +       netfs_put_read_request(rreq, false);
>         return;
>  cleanup:
>         if (netfs_priv)
> @@ -991,14 +1003,14 @@ int netfs_readpage(struct file *file,
>          */
>         do {
>                 wait_var_event(&rreq->nr_rd_ops, atomic_read(&rreq->nr_rd_ops) == 1);
> -               netfs_rreq_assess(rreq);
> +               netfs_rreq_assess(rreq, false);
>         } while (test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags));
>
>         ret = rreq->error;
>         if (ret == 0 && rreq->submitted < rreq->len)
>                 ret = -EIO;
>  out:
> -       netfs_put_read_request(rreq);
> +       netfs_put_read_request(rreq, false);
>         return ret;
>  }
>  EXPORT_SYMBOL(netfs_readpage);
> @@ -1136,7 +1148,7 @@ int netfs_write_begin(struct file *file, struct address_space *mapping,
>          */
>         for (;;) {
>                 wait_var_event(&rreq->nr_rd_ops, atomic_read(&rreq->nr_rd_ops) == 1);
> -               netfs_rreq_assess(rreq);
> +               netfs_rreq_assess(rreq, false);
>                 if (!test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags))
>                         break;
>                 cond_resched();
> @@ -1145,7 +1157,7 @@ int netfs_write_begin(struct file *file, struct address_space *mapping,
>         ret = rreq->error;
>         if (ret == 0 && rreq->submitted < rreq->len)
>                 ret = -EIO;
> -       netfs_put_read_request(rreq);
> +       netfs_put_read_request(rreq, false);
>         if (ret < 0)
>                 goto error;
>
> diff --git a/include/linux/netfs.h b/include/linux/netfs.h
> index b2589b39feb8..c22b64db237d 100644
> --- a/include/linux/netfs.h
> +++ b/include/linux/netfs.h
> @@ -60,7 +60,8 @@ enum netfs_read_source {
>         NETFS_INVALID_READ,
>  } __mode(byte);
>
> -typedef void (*netfs_io_terminated_t)(void *priv, ssize_t transferred_or_error);
> +typedef void (*netfs_io_terminated_t)(void *priv, ssize_t transferred_or_error,
> +                                     bool was_async);
>
>  /*
>   * Resources required to do operations on a cache.
> @@ -189,7 +190,7 @@ extern int netfs_write_begin(struct file *, struct address_space *,
>                              const struct netfs_read_request_ops *,
>                              void *);
>
> -extern void netfs_subreq_terminated(struct netfs_read_subrequest *, ssize_t);
> +extern void netfs_subreq_terminated(struct netfs_read_subrequest *, ssize_t, bool);
>  extern void netfs_stats_show(struct seq_file *);
>
>  #endif /* _LINUX_NETFS_H */
>
>

Looks good in testing.

Tested-by: Marc Dionne <marc.dionne@auristor.com>

Re: [PATCH 34/33] netfs: Pass flag rather than use in_softirq()

[Marc Dionne]

On Thu, Feb 18, 2021 at 10:03 AM David Howells <dhowells@redhat.com> wrote:
>
> Christoph Hellwig <hch@lst.de> wrote:
>
> > On Tue, Feb 16, 2021 at 09:29:31AM +0000, David Howells wrote:
> > > Is there a better way to do it?  The intent is to process the assessment
> > > phase in the calling thread's context if possible rather than bumping over
> > > to a worker thread.  For synchronous I/O, for example, that's done in the
> > > caller's thread.  Maybe that's the answer - if it's known to be
> > > asynchronous, I have to punt, but otherwise don't have to.
> >
> > Yes, i think you want an explicit flag instead.
>
> How about the attached instead?
>
> David
> ---
> commit 29b3e9eed616db01f15c7998c062b4e501ea6582
> Author: David Howells <dhowells@redhat.com>
> Date:   Mon Feb 15 21:56:43 2021 +0000
>
>     netfs: Pass flag rather than use in_softirq()
>
>     The in_softirq() in netfs_rreq_terminated() works fine for the cache being
>     on a normal disk, as the completion handlers may get called in softirq
>     context, but for an NVMe drive, the completion handler may get called in
>     IRQ context.
>
>     Fix to pass a flag to netfs_subreq_terminated() to indicate whether we
>     think the function isn't being called from a context in which we can do
>     allocations, waits and I/O submissions (such as softirq or interrupt
>     context).  If this flag is set, netfs lib has to punt to a worker thread to
>     handle anything like that.
>
>     The symptom involves warnings like the following appearing and the kernel
>     hanging:
>
>      WARNING: CPU: 0 PID: 0 at kernel/softirq.c:175 __local_bh_enable_ip+0x35/0x50
>      ...
>      RIP: 0010:__local_bh_enable_ip+0x35/0x50
>      ...
>      Call Trace:
>       <IRQ>
>       rxrpc_kernel_begin_call+0x7d/0x1b0 [rxrpc]
>       ? afs_rx_new_call+0x40/0x40 [kafs]
>       ? afs_alloc_call+0x28/0x120 [kafs]
>       afs_make_call+0x120/0x510 [kafs]
>       ? afs_rx_new_call+0x40/0x40 [kafs]
>       ? afs_alloc_flat_call+0xba/0x100 [kafs]
>       ? __kmalloc+0x167/0x2f0
>       ? afs_alloc_flat_call+0x9b/0x100 [kafs]
>       afs_wait_for_operation+0x2d/0x200 [kafs]
>       afs_do_sync_operation+0x16/0x20 [kafs]
>       afs_req_issue_op+0x8c/0xb0 [kafs]
>       netfs_rreq_assess+0x125/0x7d0 [netfs]
>       ? cachefiles_end_operation+0x40/0x40 [cachefiles]
>       netfs_subreq_terminated+0x117/0x220 [netfs]
>       cachefiles_read_complete+0x21/0x60 [cachefiles]
>       iomap_dio_bio_end_io+0xdd/0x110
>       blk_update_request+0x20a/0x380
>       blk_mq_end_request+0x1c/0x120
>       nvme_process_cq+0x159/0x1f0 [nvme]
>       nvme_irq+0x10/0x20 [nvme]
>       __handle_irq_event_percpu+0x37/0x150
>       handle_irq_event+0x49/0xb0
>       handle_edge_irq+0x7c/0x200
>       asm_call_irq_on_stack+0xf/0x20
>       </IRQ>
>       common_interrupt+0xad/0x120
>       asm_common_interrupt+0x1e/0x40
>      ...
>
>     Reported-by: Marc Dionne <marc.dionne@auristor.com>
>     Signed-off-by: David Howells <dhowells@redhat.com>
>     cc: Matthew Wilcox <willy@infradead.org>
>     cc: linux-mm@kvack.org
>     cc: linux-cachefs@redhat.com
>     cc: linux-afs@lists.infradead.org
>     cc: linux-nfs@vger.kernel.org
>     cc: linux-cifs@vger.kernel.org
>     cc: ceph-devel@vger.kernel.org
>     cc: v9fs-developer@lists.sourceforge.net
>     cc: linux-fsdevel@vger.kernel.org
>
> diff --git a/fs/afs/file.c b/fs/afs/file.c
> index 8f28d4f4cfd7..6dcdbbfb48e2 100644
> --- a/fs/afs/file.c
> +++ b/fs/afs/file.c
> @@ -223,7 +223,7 @@ static void afs_fetch_data_notify(struct afs_operation *op)
>
>         if (subreq) {
>                 __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
> -               netfs_subreq_terminated(subreq, error ?: req->actual_len);
> +               netfs_subreq_terminated(subreq, error ?: req->actual_len, false);
>                 req->subreq = NULL;
>         } else if (req->done) {
>                 req->done(req);
> @@ -289,7 +289,7 @@ static void afs_req_issue_op(struct netfs_read_subrequest *subreq)
>
>         fsreq = afs_alloc_read(GFP_NOFS);
>         if (!fsreq)
> -               return netfs_subreq_terminated(subreq, -ENOMEM);
> +               return netfs_subreq_terminated(subreq, -ENOMEM, false);
>
>         fsreq->subreq   = subreq;
>         fsreq->pos      = subreq->start + subreq->transferred;
> @@ -304,7 +304,7 @@ static void afs_req_issue_op(struct netfs_read_subrequest *subreq)
>
>         ret = afs_fetch_data(fsreq->vnode, fsreq);
>         if (ret < 0)
> -               return netfs_subreq_terminated(subreq, ret);
> +               return netfs_subreq_terminated(subreq, ret, false);
>  }
>
>  static int afs_symlink_readpage(struct page *page)
> diff --git a/fs/cachefiles/rdwr2.c b/fs/cachefiles/rdwr2.c
> index 4cea5a2a2d6e..40668bfe6688 100644
> --- a/fs/cachefiles/rdwr2.c
> +++ b/fs/cachefiles/rdwr2.c
> @@ -23,6 +23,7 @@ struct cachefiles_kiocb {
>         };
>         netfs_io_terminated_t   term_func;
>         void                    *term_func_priv;
> +       bool                    was_async;
>  };
>
>  static inline void cachefiles_put_kiocb(struct cachefiles_kiocb *ki)
> @@ -43,10 +44,9 @@ static void cachefiles_read_complete(struct kiocb *iocb, long ret, long ret2)
>         _enter("%ld,%ld", ret, ret2);
>
>         if (ki->term_func) {
> -               if (ret < 0)
> -                       ki->term_func(ki->term_func_priv, ret);
> -               else
> -                       ki->term_func(ki->term_func_priv, ki->skipped + ret);
> +               if (ret >= 0)
> +                       ret += ki->skipped;
> +               ki->term_func(ki->term_func_priv, ret, ki->was_async);
>         }
>
>         cachefiles_put_kiocb(ki);
> @@ -114,6 +114,7 @@ static int cachefiles_read(struct netfs_cache_resources *cres,
>         ki->skipped             = skipped;
>         ki->term_func           = term_func;
>         ki->term_func_priv      = term_func_priv;
> +       ki->was_async           = true;
>
>         if (ki->term_func)
>                 ki->iocb.ki_complete = cachefiles_read_complete;
> @@ -141,6 +142,7 @@ static int cachefiles_read(struct netfs_cache_resources *cres,
>                 ret = -EINTR;
>                 fallthrough;
>         default:
> +               ki->was_async = false;
>                 cachefiles_read_complete(&ki->iocb, ret, 0);
>                 if (ret > 0)
>                         ret = 0;
> @@ -156,7 +158,7 @@ static int cachefiles_read(struct netfs_cache_resources *cres,
>         kfree(ki);
>  presubmission_error:
>         if (term_func)
> -               term_func(term_func_priv, ret < 0 ? ret : skipped);
> +               term_func(term_func_priv, ret < 0 ? ret : skipped, false);
>         return ret;
>  }
>
> @@ -175,7 +177,7 @@ static void cachefiles_write_complete(struct kiocb *iocb, long ret, long ret2)
>         __sb_end_write(inode->i_sb, SB_FREEZE_WRITE);
>
>         if (ki->term_func)
> -               ki->term_func(ki->term_func_priv, ret);
> +               ki->term_func(ki->term_func_priv, ret, ki->was_async);
>
>         cachefiles_put_kiocb(ki);
>  }
> @@ -214,6 +216,7 @@ static int cachefiles_write(struct netfs_cache_resources *cres,
>         ki->len                 = len;
>         ki->term_func           = term_func;
>         ki->term_func_priv      = term_func_priv;
> +       ki->was_async           = true;
>
>         if (ki->term_func)
>                 ki->iocb.ki_complete = cachefiles_write_complete;
> @@ -250,6 +253,7 @@ static int cachefiles_write(struct netfs_cache_resources *cres,
>                 ret = -EINTR;
>                 /* Fall through */
>         default:
> +               ki->was_async = false;
>                 cachefiles_write_complete(&ki->iocb, ret, 0);
>                 if (ret > 0)
>                         ret = 0;
> @@ -265,7 +269,7 @@ static int cachefiles_write(struct netfs_cache_resources *cres,
>         kfree(ki);
>  presubmission_error:
>         if (term_func)
> -               term_func(term_func_priv, -ENOMEM);
> +               term_func(term_func_priv, -ENOMEM, false);
>         return -ENOMEM;
>  }
>
> diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
> index 0dd64d31eff6..dcfd805d168e 100644
> --- a/fs/ceph/addr.c
> +++ b/fs/ceph/addr.c
> @@ -221,7 +221,7 @@ static void finish_netfs_read(struct ceph_osd_request *req)
>         if (err >= 0 && err < subreq->len)
>                 __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
>
> -       netfs_subreq_terminated(subreq, err);
> +       netfs_subreq_terminated(subreq, err, true);
>
>         num_pages = calc_pages_for(osd_data->alignment, osd_data->length);
>         ceph_put_page_vector(osd_data->pages, num_pages, false);
> @@ -276,7 +276,7 @@ static void ceph_netfs_issue_op(struct netfs_read_subrequest *subreq)
>  out:
>         ceph_osdc_put_request(req);
>         if (err)
> -               netfs_subreq_terminated(subreq, err);
> +               netfs_subreq_terminated(subreq, err, false);
>         dout("%s: result %d\n", __func__, err);
>  }
>
> diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c
> index 9191a3617d91..5f5de8278499 100644
> --- a/fs/netfs/read_helper.c
> +++ b/fs/netfs/read_helper.c
> @@ -29,12 +29,13 @@ module_param_named(debug, netfs_debug, uint, S_IWUSR | S_IRUGO);
>  MODULE_PARM_DESC(netfs_debug, "Netfs support debugging mask");
>
>  static void netfs_rreq_work(struct work_struct *);
> -static void __netfs_put_subrequest(struct netfs_read_subrequest *);
> +static void __netfs_put_subrequest(struct netfs_read_subrequest *, bool);
>
> -static void netfs_put_subrequest(struct netfs_read_subrequest *subreq)
> +static void netfs_put_subrequest(struct netfs_read_subrequest *subreq,
> +                                bool was_async)
>  {
>         if (refcount_dec_and_test(&subreq->usage))
> -               __netfs_put_subrequest(subreq);
> +               __netfs_put_subrequest(subreq, was_async);
>  }
>
>  static struct netfs_read_request *netfs_alloc_read_request(
> @@ -67,7 +68,8 @@ static void netfs_get_read_request(struct netfs_read_request *rreq)
>         refcount_inc(&rreq->usage);
>  }
>
> -static void netfs_rreq_clear_subreqs(struct netfs_read_request *rreq)
> +static void netfs_rreq_clear_subreqs(struct netfs_read_request *rreq,
> +                                    bool was_async)
>  {
>         struct netfs_read_subrequest *subreq;
>
> @@ -75,7 +77,7 @@ static void netfs_rreq_clear_subreqs(struct netfs_read_request *rreq)
>                 subreq = list_first_entry(&rreq->subrequests,
>                                           struct netfs_read_subrequest, rreq_link);
>                 list_del(&subreq->rreq_link);
> -               netfs_put_subrequest(subreq);
> +               netfs_put_subrequest(subreq, was_async);
>         }
>  }
>
> @@ -83,7 +85,7 @@ static void netfs_free_read_request(struct work_struct *work)
>  {
>         struct netfs_read_request *rreq =
>                 container_of(work, struct netfs_read_request, work);
> -       netfs_rreq_clear_subreqs(rreq);
> +       netfs_rreq_clear_subreqs(rreq, false);
>         if (rreq->netfs_priv)
>                 rreq->netfs_ops->cleanup(rreq->mapping, rreq->netfs_priv);
>         trace_netfs_rreq(rreq, netfs_rreq_trace_free);
> @@ -93,10 +95,10 @@ static void netfs_free_read_request(struct work_struct *work)
>         netfs_stat_d(&netfs_n_rh_rreq);
>  }
>
> -static void netfs_put_read_request(struct netfs_read_request *rreq)
> +static void netfs_put_read_request(struct netfs_read_request *rreq, bool was_async)
>  {
>         if (refcount_dec_and_test(&rreq->usage)) {
> -               if (in_softirq()) {
> +               if (was_async) {
>                         rreq->work.func = netfs_free_read_request;
>                         if (!queue_work(system_unbound_wq, &rreq->work))
>                                 BUG();
> @@ -131,12 +133,15 @@ static void netfs_get_read_subrequest(struct netfs_read_subrequest *subreq)
>         refcount_inc(&subreq->usage);
>  }
>
> -static void __netfs_put_subrequest(struct netfs_read_subrequest *subreq)
> +static void __netfs_put_subrequest(struct netfs_read_subrequest *subreq,
> +                                  bool was_async)
>  {
> +       struct netfs_read_request *rreq = subreq->rreq;
> +
>         trace_netfs_sreq(subreq, netfs_sreq_trace_free);
> -       netfs_put_read_request(subreq->rreq);
>         kfree(subreq);
>         netfs_stat_d(&netfs_n_rh_sreq);
> +       netfs_put_read_request(rreq, was_async);
>  }
>
>  /*
> @@ -152,11 +157,12 @@ static void netfs_clear_unread(struct netfs_read_subrequest *subreq)
>         iov_iter_zero(iov_iter_count(&iter), &iter);
>  }
>
> -static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error)
> +static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error,
> +                                       bool was_async)
>  {
>         struct netfs_read_subrequest *subreq = priv;
>
> -       netfs_subreq_terminated(subreq, transferred_or_error);
> +       netfs_subreq_terminated(subreq, transferred_or_error, was_async);
>  }
>
>  /*
> @@ -186,7 +192,7 @@ static void netfs_fill_with_zeroes(struct netfs_read_request *rreq,
>  {
>         netfs_stat(&netfs_n_rh_zero);
>         __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
> -       netfs_subreq_terminated(subreq, 0);
> +       netfs_subreq_terminated(subreq, 0, false);
>  }
>
>  /*
> @@ -215,11 +221,11 @@ static void netfs_read_from_server(struct netfs_read_request *rreq,
>  /*
>   * Release those waiting.
>   */
> -static void netfs_rreq_completed(struct netfs_read_request *rreq)
> +static void netfs_rreq_completed(struct netfs_read_request *rreq, bool was_async)
>  {
>         trace_netfs_rreq(rreq, netfs_rreq_trace_done);
> -       netfs_rreq_clear_subreqs(rreq);
> -       netfs_put_read_request(rreq);
> +       netfs_rreq_clear_subreqs(rreq, was_async);
> +       netfs_put_read_request(rreq, was_async);
>  }
>
>  /*
> @@ -228,7 +234,8 @@ static void netfs_rreq_completed(struct netfs_read_request *rreq)
>   *
>   * May be called in softirq mode and we inherit a ref from the caller.
>   */
> -static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq)
> +static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq,
> +                                         bool was_async)
>  {
>         struct netfs_read_subrequest *subreq;
>         struct pagevec pvec;
> @@ -258,10 +265,11 @@ static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq)
>         }
>
>         rcu_read_unlock();
> -       netfs_rreq_completed(rreq);
> +       netfs_rreq_completed(rreq, was_async);
>  }
>
> -static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error)
> +static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error,
> +                                      bool was_async)
>  {
>         struct netfs_read_subrequest *subreq = priv;
>         struct netfs_read_request *rreq = subreq->rreq;
> @@ -278,9 +286,9 @@ static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error)
>
>         /* If we decrement nr_wr_ops to 0, the ref belongs to us. */
>         if (atomic_dec_and_test(&rreq->nr_wr_ops))
> -               netfs_rreq_unmark_after_write(rreq);
> +               netfs_rreq_unmark_after_write(rreq, was_async);
>
> -       netfs_put_subrequest(subreq);
> +       netfs_put_subrequest(subreq, was_async);
>  }
>
>  /*
> @@ -304,7 +312,7 @@ static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq)
>         list_for_each_entry_safe(subreq, p, &rreq->subrequests, rreq_link) {
>                 if (!test_bit(NETFS_SREQ_WRITE_TO_CACHE, &subreq->flags)) {
>                         list_del_init(&subreq->rreq_link);
> -                       netfs_put_subrequest(subreq);
> +                       netfs_put_subrequest(subreq, false);
>                 }
>         }
>
> @@ -324,7 +332,7 @@ static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq)
>                         subreq->len += next->len;
>                         subreq->len = round_up(subreq->len, PAGE_SIZE);
>                         list_del_init(&next->rreq_link);
> -                       netfs_put_subrequest(next);
> +                       netfs_put_subrequest(next, false);
>                 }
>
>                 iov_iter_xarray(&iter, WRITE, &rreq->mapping->i_pages,
> @@ -340,7 +348,7 @@ static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq)
>
>         /* If we decrement nr_wr_ops to 0, the usage ref belongs to us. */
>         if (atomic_dec_and_test(&rreq->nr_wr_ops))
> -               netfs_rreq_unmark_after_write(rreq);
> +               netfs_rreq_unmark_after_write(rreq, false);
>  }
>
>  static void netfs_rreq_write_to_cache_work(struct work_struct *work)
> @@ -351,9 +359,10 @@ static void netfs_rreq_write_to_cache_work(struct work_struct *work)
>         netfs_rreq_do_write_to_cache(rreq);
>  }
>
> -static void netfs_rreq_write_to_cache(struct netfs_read_request *rreq)
> +static void netfs_rreq_write_to_cache(struct netfs_read_request *rreq,
> +                                     bool was_async)
>  {
> -       if (in_softirq()) {
> +       if (was_async) {
>                 rreq->work.func = netfs_rreq_write_to_cache_work;
>                 if (!queue_work(system_unbound_wq, &rreq->work))
>                         BUG();
> @@ -479,7 +488,7 @@ static bool netfs_rreq_perform_resubmissions(struct netfs_read_request *rreq)
>  {
>         struct netfs_read_subrequest *subreq;
>
> -       WARN_ON(in_softirq());
> +       WARN_ON(in_interrupt());
>
>         trace_netfs_rreq(rreq, netfs_rreq_trace_resubmit);
>
> @@ -538,7 +547,7 @@ static void netfs_rreq_is_still_valid(struct netfs_read_request *rreq)
>   * Note that we could be in an ordinary kernel thread, on a workqueue or in
>   * softirq context at this point.  We inherit a ref from the caller.
>   */
> -static void netfs_rreq_assess(struct netfs_read_request *rreq)
> +static void netfs_rreq_assess(struct netfs_read_request *rreq, bool was_async)
>  {
>         trace_netfs_rreq(rreq, netfs_rreq_trace_assess);
>
> @@ -558,30 +567,31 @@ static void netfs_rreq_assess(struct netfs_read_request *rreq)
>         wake_up_bit(&rreq->flags, NETFS_RREQ_IN_PROGRESS);
>
>         if (test_bit(NETFS_RREQ_WRITE_TO_CACHE, &rreq->flags))
> -               return netfs_rreq_write_to_cache(rreq);
> +               return netfs_rreq_write_to_cache(rreq, was_async);
>
> -       netfs_rreq_completed(rreq);
> +       netfs_rreq_completed(rreq, was_async);
>  }
>
>  static void netfs_rreq_work(struct work_struct *work)
>  {
>         struct netfs_read_request *rreq =
>                 container_of(work, struct netfs_read_request, work);
> -       netfs_rreq_assess(rreq);
> +       netfs_rreq_assess(rreq, false);
>  }
>
>  /*
>   * Handle the completion of all outstanding I/O operations on a read request.
>   * We inherit a ref from the caller.
>   */
> -static void netfs_rreq_terminated(struct netfs_read_request *rreq)
> +static void netfs_rreq_terminated(struct netfs_read_request *rreq,
> +                                 bool was_async)
>  {
>         if (test_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags) &&
> -           in_softirq()) {
> +           was_async) {
>                 if (!queue_work(system_unbound_wq, &rreq->work))
>                         BUG();
>         } else {
> -               netfs_rreq_assess(rreq);
> +               netfs_rreq_assess(rreq, was_async);
>         }
>  }
>
> @@ -589,6 +599,7 @@ static void netfs_rreq_terminated(struct netfs_read_request *rreq)
>   * netfs_subreq_terminated - Note the termination of an I/O operation.
>   * @subreq: The I/O request that has terminated.
>   * @transferred_or_error: The amount of data transferred or an error code.
> + * @was_async: The termination was asynchronous
>   *
>   * This tells the read helper that a contributory I/O operation has terminated,
>   * one way or another, and that it should integrate the results.
> @@ -599,11 +610,12 @@ static void netfs_rreq_terminated(struct netfs_read_request *rreq)
>   * error code.  The helper will look after reissuing I/O operations as
>   * appropriate and writing downloaded data to the cache.
>   *
> - * This may be called from a softirq handler, so we want to avoid taking the
> - * spinlock if we can.
> + * If @was_async is true, the caller might be running in softirq or interrupt
> + * context and we can't sleep.
>   */
>  void netfs_subreq_terminated(struct netfs_read_subrequest *subreq,
> -                            ssize_t transferred_or_error)
> +                            ssize_t transferred_or_error,
> +                            bool was_async)
>  {
>         struct netfs_read_request *rreq = subreq->rreq;
>         int u;
> @@ -647,11 +659,11 @@ void netfs_subreq_terminated(struct netfs_read_subrequest *subreq,
>         /* If we decrement nr_rd_ops to 0, the ref belongs to us. */
>         u = atomic_dec_return(&rreq->nr_rd_ops);
>         if (u == 0)
> -               netfs_rreq_terminated(rreq);
> +               netfs_rreq_terminated(rreq, was_async);
>         else if (u == 1)
>                 wake_up_var(&rreq->nr_rd_ops);
>
> -       netfs_put_subrequest(subreq);
> +       netfs_put_subrequest(subreq, was_async);
>         return;
>
>  incomplete:
> @@ -796,7 +808,7 @@ static bool netfs_rreq_submit_slice(struct netfs_read_request *rreq,
>
>  subreq_failed:
>         rreq->error = subreq->error;
> -       netfs_put_subrequest(subreq);
> +       netfs_put_subrequest(subreq, false);
>         return false;
>  }
>
> @@ -901,7 +913,7 @@ void netfs_readahead(struct readahead_control *ractl,
>         } while (rreq->submitted < rreq->len);
>
>         if (rreq->submitted == 0) {
> -               netfs_put_read_request(rreq);
> +               netfs_put_read_request(rreq, false);
>                 return;
>         }
>
> @@ -913,11 +925,11 @@ void netfs_readahead(struct readahead_control *ractl,
>
>         /* If we decrement nr_rd_ops to 0, the ref belongs to us. */
>         if (atomic_dec_and_test(&rreq->nr_rd_ops))
> -               netfs_rreq_assess(rreq);
> +               netfs_rreq_assess(rreq, false);
>         return;
>
>  cleanup_free:
> -       netfs_put_read_request(rreq);
> +       netfs_put_read_request(rreq, false);
>         return;
>  cleanup:
>         if (netfs_priv)
> @@ -991,14 +1003,14 @@ int netfs_readpage(struct file *file,
>          */
>         do {
>                 wait_var_event(&rreq->nr_rd_ops, atomic_read(&rreq->nr_rd_ops) == 1);
> -               netfs_rreq_assess(rreq);
> +               netfs_rreq_assess(rreq, false);
>         } while (test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags));
>
>         ret = rreq->error;
>         if (ret == 0 && rreq->submitted < rreq->len)
>                 ret = -EIO;
>  out:
> -       netfs_put_read_request(rreq);
> +       netfs_put_read_request(rreq, false);
>         return ret;
>  }
>  EXPORT_SYMBOL(netfs_readpage);
> @@ -1136,7 +1148,7 @@ int netfs_write_begin(struct file *file, struct address_space *mapping,
>          */
>         for (;;) {
>                 wait_var_event(&rreq->nr_rd_ops, atomic_read(&rreq->nr_rd_ops) == 1);
> -               netfs_rreq_assess(rreq);
> +               netfs_rreq_assess(rreq, false);
>                 if (!test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags))
>                         break;
>                 cond_resched();
> @@ -1145,7 +1157,7 @@ int netfs_write_begin(struct file *file, struct address_space *mapping,
>         ret = rreq->error;
>         if (ret == 0 && rreq->submitted < rreq->len)
>                 ret = -EIO;
> -       netfs_put_read_request(rreq);
> +       netfs_put_read_request(rreq, false);
>         if (ret < 0)
>                 goto error;
>
> diff --git a/include/linux/netfs.h b/include/linux/netfs.h
> index b2589b39feb8..c22b64db237d 100644
> --- a/include/linux/netfs.h
> +++ b/include/linux/netfs.h
> @@ -60,7 +60,8 @@ enum netfs_read_source {
>         NETFS_INVALID_READ,
>  } __mode(byte);
>
> -typedef void (*netfs_io_terminated_t)(void *priv, ssize_t transferred_or_error);
> +typedef void (*netfs_io_terminated_t)(void *priv, ssize_t transferred_or_error,
> +                                     bool was_async);
>
>  /*
>   * Resources required to do operations on a cache.
> @@ -189,7 +190,7 @@ extern int netfs_write_begin(struct file *, struct address_space *,
>                              const struct netfs_read_request_ops *,
>                              void *);
>
> -extern void netfs_subreq_terminated(struct netfs_read_subrequest *, ssize_t);
> +extern void netfs_subreq_terminated(struct netfs_read_subrequest *, ssize_t, bool);
>  extern void netfs_stats_show(struct seq_file *);
>
>  #endif /* _LINUX_NETFS_H */
>
>

Looks good in testing.

Tested-by: Marc Dionne <marc.dionne@auristor.com>

Re: [PATCH 34/33] netfs: Pass flag rather than use in_softirq()

[Marc Dionne]

On Thu, Feb 18, 2021 at 10:03 AM David Howells <dhowells@redhat.com> wrote:
>
> Christoph Hellwig <hch@lst.de> wrote:
>
> > On Tue, Feb 16, 2021 at 09:29:31AM +0000, David Howells wrote:
> > > Is there a better way to do it?  The intent is to process the assessment
> > > phase in the calling thread's context if possible rather than bumping over
> > > to a worker thread.  For synchronous I/O, for example, that's done in the
> > > caller's thread.  Maybe that's the answer - if it's known to be
> > > asynchronous, I have to punt, but otherwise don't have to.
> >
> > Yes, i think you want an explicit flag instead.
>
> How about the attached instead?
>
> David
> ---
> commit 29b3e9eed616db01f15c7998c062b4e501ea6582
> Author: David Howells <dhowells@redhat.com>
> Date:   Mon Feb 15 21:56:43 2021 +0000
>
>     netfs: Pass flag rather than use in_softirq()
>
>     The in_softirq() in netfs_rreq_terminated() works fine for the cache being
>     on a normal disk, as the completion handlers may get called in softirq
>     context, but for an NVMe drive, the completion handler may get called in
>     IRQ context.
>
>     Fix to pass a flag to netfs_subreq_terminated() to indicate whether we
>     think the function isn't being called from a context in which we can do
>     allocations, waits and I/O submissions (such as softirq or interrupt
>     context).  If this flag is set, netfs lib has to punt to a worker thread to
>     handle anything like that.
>
>     The symptom involves warnings like the following appearing and the kernel
>     hanging:
>
>      WARNING: CPU: 0 PID: 0 at kernel/softirq.c:175 __local_bh_enable_ip+0x35/0x50
>      ...
>      RIP: 0010:__local_bh_enable_ip+0x35/0x50
>      ...
>      Call Trace:
>       <IRQ>
>       rxrpc_kernel_begin_call+0x7d/0x1b0 [rxrpc]
>       ? afs_rx_new_call+0x40/0x40 [kafs]
>       ? afs_alloc_call+0x28/0x120 [kafs]
>       afs_make_call+0x120/0x510 [kafs]
>       ? afs_rx_new_call+0x40/0x40 [kafs]
>       ? afs_alloc_flat_call+0xba/0x100 [kafs]
>       ? __kmalloc+0x167/0x2f0
>       ? afs_alloc_flat_call+0x9b/0x100 [kafs]
>       afs_wait_for_operation+0x2d/0x200 [kafs]
>       afs_do_sync_operation+0x16/0x20 [kafs]
>       afs_req_issue_op+0x8c/0xb0 [kafs]
>       netfs_rreq_assess+0x125/0x7d0 [netfs]
>       ? cachefiles_end_operation+0x40/0x40 [cachefiles]
>       netfs_subreq_terminated+0x117/0x220 [netfs]
>       cachefiles_read_complete+0x21/0x60 [cachefiles]
>       iomap_dio_bio_end_io+0xdd/0x110
>       blk_update_request+0x20a/0x380
>       blk_mq_end_request+0x1c/0x120
>       nvme_process_cq+0x159/0x1f0 [nvme]
>       nvme_irq+0x10/0x20 [nvme]
>       __handle_irq_event_percpu+0x37/0x150
>       handle_irq_event+0x49/0xb0
>       handle_edge_irq+0x7c/0x200
>       asm_call_irq_on_stack+0xf/0x20
>       </IRQ>
>       common_interrupt+0xad/0x120
>       asm_common_interrupt+0x1e/0x40
>      ...
>
>     Reported-by: Marc Dionne <marc.dionne@auristor.com>
>     Signed-off-by: David Howells <dhowells@redhat.com>
>     cc: Matthew Wilcox <willy@infradead.org>
>     cc: linux-mm@kvack.org
>     cc: linux-cachefs@redhat.com
>     cc: linux-afs@lists.infradead.org
>     cc: linux-nfs@vger.kernel.org
>     cc: linux-cifs@vger.kernel.org
>     cc: ceph-devel@vger.kernel.org
>     cc: v9fs-developer@lists.sourceforge.net
>     cc: linux-fsdevel@vger.kernel.org
>
> diff --git a/fs/afs/file.c b/fs/afs/file.c
> index 8f28d4f4cfd7..6dcdbbfb48e2 100644
> --- a/fs/afs/file.c
> +++ b/fs/afs/file.c
> @@ -223,7 +223,7 @@ static void afs_fetch_data_notify(struct afs_operation *op)
>
>         if (subreq) {
>                 __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
> -               netfs_subreq_terminated(subreq, error ?: req->actual_len);
> +               netfs_subreq_terminated(subreq, error ?: req->actual_len, false);
>                 req->subreq = NULL;
>         } else if (req->done) {
>                 req->done(req);
> @@ -289,7 +289,7 @@ static void afs_req_issue_op(struct netfs_read_subrequest *subreq)
>
>         fsreq = afs_alloc_read(GFP_NOFS);
>         if (!fsreq)
> -               return netfs_subreq_terminated(subreq, -ENOMEM);
> +               return netfs_subreq_terminated(subreq, -ENOMEM, false);
>
>         fsreq->subreq   = subreq;
>         fsreq->pos      = subreq->start + subreq->transferred;
> @@ -304,7 +304,7 @@ static void afs_req_issue_op(struct netfs_read_subrequest *subreq)
>
>         ret = afs_fetch_data(fsreq->vnode, fsreq);
>         if (ret < 0)
> -               return netfs_subreq_terminated(subreq, ret);
> +               return netfs_subreq_terminated(subreq, ret, false);
>  }
>
>  static int afs_symlink_readpage(struct page *page)
> diff --git a/fs/cachefiles/rdwr2.c b/fs/cachefiles/rdwr2.c
> index 4cea5a2a2d6e..40668bfe6688 100644
> --- a/fs/cachefiles/rdwr2.c
> +++ b/fs/cachefiles/rdwr2.c
> @@ -23,6 +23,7 @@ struct cachefiles_kiocb {
>         };
>         netfs_io_terminated_t   term_func;
>         void                    *term_func_priv;
> +       bool                    was_async;
>  };
>
>  static inline void cachefiles_put_kiocb(struct cachefiles_kiocb *ki)
> @@ -43,10 +44,9 @@ static void cachefiles_read_complete(struct kiocb *iocb, long ret, long ret2)
>         _enter("%ld,%ld", ret, ret2);
>
>         if (ki->term_func) {
> -               if (ret < 0)
> -                       ki->term_func(ki->term_func_priv, ret);
> -               else
> -                       ki->term_func(ki->term_func_priv, ki->skipped + ret);
> +               if (ret >= 0)
> +                       ret += ki->skipped;
> +               ki->term_func(ki->term_func_priv, ret, ki->was_async);
>         }
>
>         cachefiles_put_kiocb(ki);
> @@ -114,6 +114,7 @@ static int cachefiles_read(struct netfs_cache_resources *cres,
>         ki->skipped             = skipped;
>         ki->term_func           = term_func;
>         ki->term_func_priv      = term_func_priv;
> +       ki->was_async           = true;
>
>         if (ki->term_func)
>                 ki->iocb.ki_complete = cachefiles_read_complete;
> @@ -141,6 +142,7 @@ static int cachefiles_read(struct netfs_cache_resources *cres,
>                 ret = -EINTR;
>                 fallthrough;
>         default:
> +               ki->was_async = false;
>                 cachefiles_read_complete(&ki->iocb, ret, 0);
>                 if (ret > 0)
>                         ret = 0;
> @@ -156,7 +158,7 @@ static int cachefiles_read(struct netfs_cache_resources *cres,
>         kfree(ki);
>  presubmission_error:
>         if (term_func)
> -               term_func(term_func_priv, ret < 0 ? ret : skipped);
> +               term_func(term_func_priv, ret < 0 ? ret : skipped, false);
>         return ret;
>  }
>
> @@ -175,7 +177,7 @@ static void cachefiles_write_complete(struct kiocb *iocb, long ret, long ret2)
>         __sb_end_write(inode->i_sb, SB_FREEZE_WRITE);
>
>         if (ki->term_func)
> -               ki->term_func(ki->term_func_priv, ret);
> +               ki->term_func(ki->term_func_priv, ret, ki->was_async);
>
>         cachefiles_put_kiocb(ki);
>  }
> @@ -214,6 +216,7 @@ static int cachefiles_write(struct netfs_cache_resources *cres,
>         ki->len                 = len;
>         ki->term_func           = term_func;
>         ki->term_func_priv      = term_func_priv;
> +       ki->was_async           = true;
>
>         if (ki->term_func)
>                 ki->iocb.ki_complete = cachefiles_write_complete;
> @@ -250,6 +253,7 @@ static int cachefiles_write(struct netfs_cache_resources *cres,
>                 ret = -EINTR;
>                 /* Fall through */
>         default:
> +               ki->was_async = false;
>                 cachefiles_write_complete(&ki->iocb, ret, 0);
>                 if (ret > 0)
>                         ret = 0;
> @@ -265,7 +269,7 @@ static int cachefiles_write(struct netfs_cache_resources *cres,
>         kfree(ki);
>  presubmission_error:
>         if (term_func)
> -               term_func(term_func_priv, -ENOMEM);
> +               term_func(term_func_priv, -ENOMEM, false);
>         return -ENOMEM;
>  }
>
> diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
> index 0dd64d31eff6..dcfd805d168e 100644
> --- a/fs/ceph/addr.c
> +++ b/fs/ceph/addr.c
> @@ -221,7 +221,7 @@ static void finish_netfs_read(struct ceph_osd_request *req)
>         if (err >= 0 && err < subreq->len)
>                 __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
>
> -       netfs_subreq_terminated(subreq, err);
> +       netfs_subreq_terminated(subreq, err, true);
>
>         num_pages = calc_pages_for(osd_data->alignment, osd_data->length);
>         ceph_put_page_vector(osd_data->pages, num_pages, false);
> @@ -276,7 +276,7 @@ static void ceph_netfs_issue_op(struct netfs_read_subrequest *subreq)
>  out:
>         ceph_osdc_put_request(req);
>         if (err)
> -               netfs_subreq_terminated(subreq, err);
> +               netfs_subreq_terminated(subreq, err, false);
>         dout("%s: result %d\n", __func__, err);
>  }
>
> diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c
> index 9191a3617d91..5f5de8278499 100644
> --- a/fs/netfs/read_helper.c
> +++ b/fs/netfs/read_helper.c
> @@ -29,12 +29,13 @@ module_param_named(debug, netfs_debug, uint, S_IWUSR | S_IRUGO);
>  MODULE_PARM_DESC(netfs_debug, "Netfs support debugging mask");
>
>  static void netfs_rreq_work(struct work_struct *);
> -static void __netfs_put_subrequest(struct netfs_read_subrequest *);
> +static void __netfs_put_subrequest(struct netfs_read_subrequest *, bool);
>
> -static void netfs_put_subrequest(struct netfs_read_subrequest *subreq)
> +static void netfs_put_subrequest(struct netfs_read_subrequest *subreq,
> +                                bool was_async)
>  {
>         if (refcount_dec_and_test(&subreq->usage))
> -               __netfs_put_subrequest(subreq);
> +               __netfs_put_subrequest(subreq, was_async);
>  }
>
>  static struct netfs_read_request *netfs_alloc_read_request(
> @@ -67,7 +68,8 @@ static void netfs_get_read_request(struct netfs_read_request *rreq)
>         refcount_inc(&rreq->usage);
>  }
>
> -static void netfs_rreq_clear_subreqs(struct netfs_read_request *rreq)
> +static void netfs_rreq_clear_subreqs(struct netfs_read_request *rreq,
> +                                    bool was_async)
>  {
>         struct netfs_read_subrequest *subreq;
>
> @@ -75,7 +77,7 @@ static void netfs_rreq_clear_subreqs(struct netfs_read_request *rreq)
>                 subreq = list_first_entry(&rreq->subrequests,
>                                           struct netfs_read_subrequest, rreq_link);
>                 list_del(&subreq->rreq_link);
> -               netfs_put_subrequest(subreq);
> +               netfs_put_subrequest(subreq, was_async);
>         }
>  }
>
> @@ -83,7 +85,7 @@ static void netfs_free_read_request(struct work_struct *work)
>  {
>         struct netfs_read_request *rreq =
>                 container_of(work, struct netfs_read_request, work);
> -       netfs_rreq_clear_subreqs(rreq);
> +       netfs_rreq_clear_subreqs(rreq, false);
>         if (rreq->netfs_priv)
>                 rreq->netfs_ops->cleanup(rreq->mapping, rreq->netfs_priv);
>         trace_netfs_rreq(rreq, netfs_rreq_trace_free);
> @@ -93,10 +95,10 @@ static void netfs_free_read_request(struct work_struct *work)
>         netfs_stat_d(&netfs_n_rh_rreq);
>  }
>
> -static void netfs_put_read_request(struct netfs_read_request *rreq)
> +static void netfs_put_read_request(struct netfs_read_request *rreq, bool was_async)
>  {
>         if (refcount_dec_and_test(&rreq->usage)) {
> -               if (in_softirq()) {
> +               if (was_async) {
>                         rreq->work.func = netfs_free_read_request;
>                         if (!queue_work(system_unbound_wq, &rreq->work))
>                                 BUG();
> @@ -131,12 +133,15 @@ static void netfs_get_read_subrequest(struct netfs_read_subrequest *subreq)
>         refcount_inc(&subreq->usage);
>  }
>
> -static void __netfs_put_subrequest(struct netfs_read_subrequest *subreq)
> +static void __netfs_put_subrequest(struct netfs_read_subrequest *subreq,
> +                                  bool was_async)
>  {
> +       struct netfs_read_request *rreq = subreq->rreq;
> +
>         trace_netfs_sreq(subreq, netfs_sreq_trace_free);
> -       netfs_put_read_request(subreq->rreq);
>         kfree(subreq);
>         netfs_stat_d(&netfs_n_rh_sreq);
> +       netfs_put_read_request(rreq, was_async);
>  }
>
>  /*
> @@ -152,11 +157,12 @@ static void netfs_clear_unread(struct netfs_read_subrequest *subreq)
>         iov_iter_zero(iov_iter_count(&iter), &iter);
>  }
>
> -static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error)
> +static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error,
> +                                       bool was_async)
>  {
>         struct netfs_read_subrequest *subreq = priv;
>
> -       netfs_subreq_terminated(subreq, transferred_or_error);
> +       netfs_subreq_terminated(subreq, transferred_or_error, was_async);
>  }
>
>  /*
> @@ -186,7 +192,7 @@ static void netfs_fill_with_zeroes(struct netfs_read_request *rreq,
>  {
>         netfs_stat(&netfs_n_rh_zero);
>         __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
> -       netfs_subreq_terminated(subreq, 0);
> +       netfs_subreq_terminated(subreq, 0, false);
>  }
>
>  /*
> @@ -215,11 +221,11 @@ static void netfs_read_from_server(struct netfs_read_request *rreq,
>  /*
>   * Release those waiting.
>   */
> -static void netfs_rreq_completed(struct netfs_read_request *rreq)
> +static void netfs_rreq_completed(struct netfs_read_request *rreq, bool was_async)
>  {
>         trace_netfs_rreq(rreq, netfs_rreq_trace_done);
> -       netfs_rreq_clear_subreqs(rreq);
> -       netfs_put_read_request(rreq);
> +       netfs_rreq_clear_subreqs(rreq, was_async);
> +       netfs_put_read_request(rreq, was_async);
>  }
>
>  /*
> @@ -228,7 +234,8 @@ static void netfs_rreq_completed(struct netfs_read_request *rreq)
>   *
>   * May be called in softirq mode and we inherit a ref from the caller.
>   */
> -static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq)
> +static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq,
> +                                         bool was_async)
>  {
>         struct netfs_read_subrequest *subreq;
>         struct pagevec pvec;
> @@ -258,10 +265,11 @@ static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq)
>         }
>
>         rcu_read_unlock();
> -       netfs_rreq_completed(rreq);
> +       netfs_rreq_completed(rreq, was_async);
>  }
>
> -static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error)
> +static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error,
> +                                      bool was_async)
>  {
>         struct netfs_read_subrequest *subreq = priv;
>         struct netfs_read_request *rreq = subreq->rreq;
> @@ -278,9 +286,9 @@ static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error)
>
>         /* If we decrement nr_wr_ops to 0, the ref belongs to us. */
>         if (atomic_dec_and_test(&rreq->nr_wr_ops))
> -               netfs_rreq_unmark_after_write(rreq);
> +               netfs_rreq_unmark_after_write(rreq, was_async);
>
> -       netfs_put_subrequest(subreq);
> +       netfs_put_subrequest(subreq, was_async);
>  }
>
>  /*
> @@ -304,7 +312,7 @@ static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq)
>         list_for_each_entry_safe(subreq, p, &rreq->subrequests, rreq_link) {
>                 if (!test_bit(NETFS_SREQ_WRITE_TO_CACHE, &subreq->flags)) {
>                         list_del_init(&subreq->rreq_link);
> -                       netfs_put_subrequest(subreq);
> +                       netfs_put_subrequest(subreq, false);
>                 }
>         }
>
> @@ -324,7 +332,7 @@ static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq)
>                         subreq->len += next->len;
>                         subreq->len = round_up(subreq->len, PAGE_SIZE);
>                         list_del_init(&next->rreq_link);
> -                       netfs_put_subrequest(next);
> +                       netfs_put_subrequest(next, false);
>                 }
>
>                 iov_iter_xarray(&iter, WRITE, &rreq->mapping->i_pages,
> @@ -340,7 +348,7 @@ static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq)
>
>         /* If we decrement nr_wr_ops to 0, the usage ref belongs to us. */
>         if (atomic_dec_and_test(&rreq->nr_wr_ops))
> -               netfs_rreq_unmark_after_write(rreq);
> +               netfs_rreq_unmark_after_write(rreq, false);
>  }
>
>  static void netfs_rreq_write_to_cache_work(struct work_struct *work)
> @@ -351,9 +359,10 @@ static void netfs_rreq_write_to_cache_work(struct work_struct *work)
>         netfs_rreq_do_write_to_cache(rreq);
>  }
>
> -static void netfs_rreq_write_to_cache(struct netfs_read_request *rreq)
> +static void netfs_rreq_write_to_cache(struct netfs_read_request *rreq,
> +                                     bool was_async)
>  {
> -       if (in_softirq()) {
> +       if (was_async) {
>                 rreq->work.func = netfs_rreq_write_to_cache_work;
>                 if (!queue_work(system_unbound_wq, &rreq->work))
>                         BUG();
> @@ -479,7 +488,7 @@ static bool netfs_rreq_perform_resubmissions(struct netfs_read_request *rreq)
>  {
>         struct netfs_read_subrequest *subreq;
>
> -       WARN_ON(in_softirq());
> +       WARN_ON(in_interrupt());
>
>         trace_netfs_rreq(rreq, netfs_rreq_trace_resubmit);
>
> @@ -538,7 +547,7 @@ static void netfs_rreq_is_still_valid(struct netfs_read_request *rreq)
>   * Note that we could be in an ordinary kernel thread, on a workqueue or in
>   * softirq context at this point.  We inherit a ref from the caller.
>   */
> -static void netfs_rreq_assess(struct netfs_read_request *rreq)
> +static void netfs_rreq_assess(struct netfs_read_request *rreq, bool was_async)
>  {
>         trace_netfs_rreq(rreq, netfs_rreq_trace_assess);
>
> @@ -558,30 +567,31 @@ static void netfs_rreq_assess(struct netfs_read_request *rreq)
>         wake_up_bit(&rreq->flags, NETFS_RREQ_IN_PROGRESS);
>
>         if (test_bit(NETFS_RREQ_WRITE_TO_CACHE, &rreq->flags))
> -               return netfs_rreq_write_to_cache(rreq);
> +               return netfs_rreq_write_to_cache(rreq, was_async);
>
> -       netfs_rreq_completed(rreq);
> +       netfs_rreq_completed(rreq, was_async);
>  }
>
>  static void netfs_rreq_work(struct work_struct *work)
>  {
>         struct netfs_read_request *rreq =
>                 container_of(work, struct netfs_read_request, work);
> -       netfs_rreq_assess(rreq);
> +       netfs_rreq_assess(rreq, false);
>  }
>
>  /*
>   * Handle the completion of all outstanding I/O operations on a read request.
>   * We inherit a ref from the caller.
>   */
> -static void netfs_rreq_terminated(struct netfs_read_request *rreq)
> +static void netfs_rreq_terminated(struct netfs_read_request *rreq,
> +                                 bool was_async)
>  {
>         if (test_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags) &&
> -           in_softirq()) {
> +           was_async) {
>                 if (!queue_work(system_unbound_wq, &rreq->work))
>                         BUG();
>         } else {
> -               netfs_rreq_assess(rreq);
> +               netfs_rreq_assess(rreq, was_async);
>         }
>  }
>
> @@ -589,6 +599,7 @@ static void netfs_rreq_terminated(struct netfs_read_request *rreq)
>   * netfs_subreq_terminated - Note the termination of an I/O operation.
>   * @subreq: The I/O request that has terminated.
>   * @transferred_or_error: The amount of data transferred or an error code.
> + * @was_async: The termination was asynchronous
>   *
>   * This tells the read helper that a contributory I/O operation has terminated,
>   * one way or another, and that it should integrate the results.
> @@ -599,11 +610,12 @@ static void netfs_rreq_terminated(struct netfs_read_request *rreq)
>   * error code.  The helper will look after reissuing I/O operations as
>   * appropriate and writing downloaded data to the cache.
>   *
> - * This may be called from a softirq handler, so we want to avoid taking the
> - * spinlock if we can.
> + * If @was_async is true, the caller might be running in softirq or interrupt
> + * context and we can't sleep.
>   */
>  void netfs_subreq_terminated(struct netfs_read_subrequest *subreq,
> -                            ssize_t transferred_or_error)
> +                            ssize_t transferred_or_error,
> +                            bool was_async)
>  {
>         struct netfs_read_request *rreq = subreq->rreq;
>         int u;
> @@ -647,11 +659,11 @@ void netfs_subreq_terminated(struct netfs_read_subrequest *subreq,
>         /* If we decrement nr_rd_ops to 0, the ref belongs to us. */
>         u = atomic_dec_return(&rreq->nr_rd_ops);
>         if (u == 0)
> -               netfs_rreq_terminated(rreq);
> +               netfs_rreq_terminated(rreq, was_async);
>         else if (u == 1)
>                 wake_up_var(&rreq->nr_rd_ops);
>
> -       netfs_put_subrequest(subreq);
> +       netfs_put_subrequest(subreq, was_async);
>         return;
>
>  incomplete:
> @@ -796,7 +808,7 @@ static bool netfs_rreq_submit_slice(struct netfs_read_request *rreq,
>
>  subreq_failed:
>         rreq->error = subreq->error;
> -       netfs_put_subrequest(subreq);
> +       netfs_put_subrequest(subreq, false);
>         return false;
>  }
>
> @@ -901,7 +913,7 @@ void netfs_readahead(struct readahead_control *ractl,
>         } while (rreq->submitted < rreq->len);
>
>         if (rreq->submitted == 0) {
> -               netfs_put_read_request(rreq);
> +               netfs_put_read_request(rreq, false);
>                 return;
>         }
>
> @@ -913,11 +925,11 @@ void netfs_readahead(struct readahead_control *ractl,
>
>         /* If we decrement nr_rd_ops to 0, the ref belongs to us. */
>         if (atomic_dec_and_test(&rreq->nr_rd_ops))
> -               netfs_rreq_assess(rreq);
> +               netfs_rreq_assess(rreq, false);
>         return;
>
>  cleanup_free:
> -       netfs_put_read_request(rreq);
> +       netfs_put_read_request(rreq, false);
>         return;
>  cleanup:
>         if (netfs_priv)
> @@ -991,14 +1003,14 @@ int netfs_readpage(struct file *file,
>          */
>         do {
>                 wait_var_event(&rreq->nr_rd_ops, atomic_read(&rreq->nr_rd_ops) == 1);
> -               netfs_rreq_assess(rreq);
> +               netfs_rreq_assess(rreq, false);
>         } while (test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags));
>
>         ret = rreq->error;
>         if (ret == 0 && rreq->submitted < rreq->len)
>                 ret = -EIO;
>  out:
> -       netfs_put_read_request(rreq);
> +       netfs_put_read_request(rreq, false);
>         return ret;
>  }
>  EXPORT_SYMBOL(netfs_readpage);
> @@ -1136,7 +1148,7 @@ int netfs_write_begin(struct file *file, struct address_space *mapping,
>          */
>         for (;;) {
>                 wait_var_event(&rreq->nr_rd_ops, atomic_read(&rreq->nr_rd_ops) == 1);
> -               netfs_rreq_assess(rreq);
> +               netfs_rreq_assess(rreq, false);
>                 if (!test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags))
>                         break;
>                 cond_resched();
> @@ -1145,7 +1157,7 @@ int netfs_write_begin(struct file *file, struct address_space *mapping,
>         ret = rreq->error;
>         if (ret == 0 && rreq->submitted < rreq->len)
>                 ret = -EIO;
> -       netfs_put_read_request(rreq);
> +       netfs_put_read_request(rreq, false);
>         if (ret < 0)
>                 goto error;
>
> diff --git a/include/linux/netfs.h b/include/linux/netfs.h
> index b2589b39feb8..c22b64db237d 100644
> --- a/include/linux/netfs.h
> +++ b/include/linux/netfs.h
> @@ -60,7 +60,8 @@ enum netfs_read_source {
>         NETFS_INVALID_READ,
>  } __mode(byte);
>
> -typedef void (*netfs_io_terminated_t)(void *priv, ssize_t transferred_or_error);
> +typedef void (*netfs_io_terminated_t)(void *priv, ssize_t transferred_or_error,
> +                                     bool was_async);
>
>  /*
>   * Resources required to do operations on a cache.
> @@ -189,7 +190,7 @@ extern int netfs_write_begin(struct file *, struct address_space *,
>                              const struct netfs_read_request_ops *,
>                              void *);
>
> -extern void netfs_subreq_terminated(struct netfs_read_subrequest *, ssize_t);
> +extern void netfs_subreq_terminated(struct netfs_read_subrequest *, ssize_t, bool);
>  extern void netfs_stats_show(struct seq_file *);
>
>  #endif /* _LINUX_NETFS_H */
>
>

Looks good in testing.

Tested-by: Marc Dionne <marc.dionne@auristor.com>

Re: [PATCH 03/33] mm: Implement readahead_control pageset expansion

[David Howells]

Matthew Wilcox <willy@infradead.org> wrote:

> So readahead_expand() needs to adjust the file's f_ra so that when the
> application gets to 64kB, it kicks off the readahead of 4MB-8MB chunk (and
> then when we get to 4MB+256kB, it kicks off the readahead of 8MB-12MB,
> and so on).

Ummm...  Two questions:

Firstly, how do I do that?  Set ->async_size?  And to what?  The expansion
could be 2MB from a ceph stripe, 256k from the cache.  Just to add to the fun,
the leading edge of the window might also be rounded downwards and the RA
trigger could be before where the app is going to start reading.

Secondly, what happens if, say, a 4MB read is covered by a single 4MB THP?

David

Re: [PATCH 34/33] netfs: Pass flag rather than use in_softirq()

[Sebastian Andrzej Siewior]

On 2021-02-18 14:02:36 [+0000], David Howells wrote:
> How about the attached instead?

Thank you for that flag.

> David

Sebastian

Re: [PATCH 00/33] Network fs helper library & fscache kiocb API [ver #3]

[Matthew Wilcox]

On Mon, Feb 15, 2021 at 11:22:20PM -0600, Steve French wrote:
> On Mon, Feb 15, 2021 at 8:10 PM Matthew Wilcox <willy@infradead.org> wrote:
> > The switch from readpages to readahead does help in a couple of corner
> > cases.  For example, if you have two processes reading the same file at
> > the same time, one will now block on the other (due to the page lock)
> > rather than submitting a mess of overlapping and partial reads.
> 
> Do you have a simple repro example of this we could try (fio, dbench, iozone
> etc) to get some objective perf data?

I don't.  The problem was noted by the f2fs people, so maybe they have a
reproducer.

> My biggest worry is making sure that the switch to netfs doesn't degrade
> performance (which might be a low bar now since current network file copy
> perf seems to signifcantly lag at least Windows), and in some easy to understand
> scenarios want to make sure it actually helps perf.

I had a question about that ... you've mentioned having 4x4MB reads
outstanding as being the way to get optimum performance.  Is there a
significant performance difference between 4x4MB, 16x1MB and 64x256kB?
I'm concerned about having "too large" an I/O on the wire at a given time.
For example, with a 1Gbps link, you get 250MB/s.  That's a minimum
latency of 16us for a 4kB page, but 16ms for a 4MB page.

"For very simple tasks, people can perceive latencies down to 2 ms or less"
(https://danluu.com/input-lag/)
so going all the way to 4MB I/Os takes us into the perceptible latency
range, whereas a 256kB I/O is only 1ms.

So could you do some experiments with fio doing direct I/O to see if
it takes significantly longer to do, say, 1TB of I/O in 4MB chunks vs
256kB chunks?  Obviously use threads to keep lots of I/Os outstanding.

Re: [f2fs-dev] [PATCH 00/33] Network fs helper library & fscache kiocb API [ver #3]

[Matthew Wilcox]

On Mon, Feb 15, 2021 at 11:22:20PM -0600, Steve French wrote:
> On Mon, Feb 15, 2021 at 8:10 PM Matthew Wilcox <willy@infradead.org> wrote:
> > The switch from readpages to readahead does help in a couple of corner
> > cases.  For example, if you have two processes reading the same file at
> > the same time, one will now block on the other (due to the page lock)
> > rather than submitting a mess of overlapping and partial reads.
> 
> Do you have a simple repro example of this we could try (fio, dbench, iozone
> etc) to get some objective perf data?

I don't.  The problem was noted by the f2fs people, so maybe they have a
reproducer.

> My biggest worry is making sure that the switch to netfs doesn't degrade
> performance (which might be a low bar now since current network file copy
> perf seems to signifcantly lag at least Windows), and in some easy to understand
> scenarios want to make sure it actually helps perf.

I had a question about that ... you've mentioned having 4x4MB reads
outstanding as being the way to get optimum performance.  Is there a
significant performance difference between 4x4MB, 16x1MB and 64x256kB?
I'm concerned about having "too large" an I/O on the wire at a given time.
For example, with a 1Gbps link, you get 250MB/s.  That's a minimum
latency of 16us for a 4kB page, but 16ms for a 4MB page.

"For very simple tasks, people can perceive latencies down to 2 ms or less"
(https://danluu.com/input-lag/)
so going all the way to 4MB I/Os takes us into the perceptible latency
range, whereas a 256kB I/O is only 1ms.

So could you do some experiments with fio doing direct I/O to see if
it takes significantly longer to do, say, 1TB of I/O in 4MB chunks vs
256kB chunks?  Obviously use threads to keep lots of I/Os outstanding.


_______________________________________________
Linux-f2fs-devel mailing list
Linux-f2fs-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel

Re: [PATCH 00/33] Network fs helper library & fscache kiocb API [ver #3]

[Steve French]

On Tue, Feb 23, 2021 at 2:28 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Mon, Feb 15, 2021 at 11:22:20PM -0600, Steve French wrote:
> > On Mon, Feb 15, 2021 at 8:10 PM Matthew Wilcox <willy@infradead.org> wrote:
> > > The switch from readpages to readahead does help in a couple of corner
> > > cases.  For example, if you have two processes reading the same file at
> > > the same time, one will now block on the other (due to the page lock)
> > > rather than submitting a mess of overlapping and partial reads.
> >
> > Do you have a simple repro example of this we could try (fio, dbench, iozone
> > etc) to get some objective perf data?
>
> I don't.  The problem was noted by the f2fs people, so maybe they have a
> reproducer.
>
> > My biggest worry is making sure that the switch to netfs doesn't degrade
> > performance (which might be a low bar now since current network file copy
> > perf seems to signifcantly lag at least Windows), and in some easy to understand
> > scenarios want to make sure it actually helps perf.
>
> I had a question about that ... you've mentioned having 4x4MB reads
> outstanding as being the way to get optimum performance.  Is there a
> significant performance difference between 4x4MB, 16x1MB and 64x256kB?
> I'm concerned about having "too large" an I/O on the wire at a given time.
> For example, with a 1Gbps link, you get 250MB/s.  That's a minimum
> latency of 16us for a 4kB page, but 16ms for a 4MB page.
>
> "For very simple tasks, people can perceive latencies down to 2 ms or less"
> (https://danluu.com/input-lag/)
> so going all the way to 4MB I/Os takes us into the perceptible latency
> range, whereas a 256kB I/O is only 1ms.
>
> So could you do some experiments with fio doing direct I/O to see if
> it takes significantly longer to do, say, 1TB of I/O in 4MB chunks vs
> 256kB chunks?  Obviously use threads to keep lots of I/Os outstanding.

That is a good question and it has been months since I have done experiments
with something similar.   Obviously this will vary depending on RDMA or not and
multichannel or not - but assuming the 'normal' low end network configuration -
ie a 1Gbps link and no RDMA or multichannel I could do some more recent
experiments.

In the past what I had noticed was that server performance for simple
workloads like cp or grep increased with network I/O size to a point:
smaller than 256K packet size was bad. Performance improved
significantly from 256K to 512K to 1MB, but only very
slightly from 1MB to 2MB to 4MB and sometimes degraded at 8MB
(IIRC 8MB is the max commonly supported by SMB3 servers),
but this is with only one adapter (no multichannel) and 1Gb adapters.

But in those examples there wasn't a lot of concurrency on the wire.

I did some experiments with increasing the read ahead size
(which causes more than one async read to be issued by cifs.ko
but presumably does still result in some 'dead time')
which seemed to help perf of some sequential read examples
(e.g. grep or cp) to some servers but I didn't try enough variety
of server targets to feel confident about that change especially
if netfs is coming

e.g. a change I experimented with was:
         sb->s_bdi->ra_pages = cifs_sb->ctx->rsize / PAGE_SIZE
to
         sb->s_bdi->ra_pages = 2 * cifs_sb->ctx->rsize / PAGE_SIZE

and it did seem to help a little.

I would expect that 8x1MB (ie trying to keep eight 1MB reads in process should
keep the network mostly busy and not lead to too much dead time on
server, client
or network) and is 'good enough' in many read ahead use cases (at
least for non-RDMA, and non-multichannel on a slower network) to keep the pipe
file, and I would expect the performance to be similar to the equivalent using
2MB read (e.g. 4x2MB) and perhaps better than 2x4MB.  Below 1MB i/o size
on the wire I would expect to see degradation due to packet processing
and task switching
overhead.  Would definitely be worth doing more experimentation here.
-- 
Thanks,

Steve

Re: [PATCH 00/33] Network fs helper library & fscache kiocb API [ver #3]

[Steve French]

On Tue, Feb 23, 2021 at 2:28 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Mon, Feb 15, 2021 at 11:22:20PM -0600, Steve French wrote:
> > On Mon, Feb 15, 2021 at 8:10 PM Matthew Wilcox <willy@infradead.org> wrote:
> > > The switch from readpages to readahead does help in a couple of corner
> > > cases.  For example, if you have two processes reading the same file at
> > > the same time, one will now block on the other (due to the page lock)
> > > rather than submitting a mess of overlapping and partial reads.
> >
> > Do you have a simple repro example of this we could try (fio, dbench, iozone
> > etc) to get some objective perf data?
>
> I don't.  The problem was noted by the f2fs people, so maybe they have a
> reproducer.
>
> > My biggest worry is making sure that the switch to netfs doesn't degrade
> > performance (which might be a low bar now since current network file copy
> > perf seems to signifcantly lag at least Windows), and in some easy to understand
> > scenarios want to make sure it actually helps perf.
>
> I had a question about that ... you've mentioned having 4x4MB reads
> outstanding as being the way to get optimum performance.  Is there a
> significant performance difference between 4x4MB, 16x1MB and 64x256kB?
> I'm concerned about having "too large" an I/O on the wire at a given time.
> For example, with a 1Gbps link, you get 250MB/s.  That's a minimum
> latency of 16us for a 4kB page, but 16ms for a 4MB page.
>
> "For very simple tasks, people can perceive latencies down to 2 ms or less"
> (https://danluu.com/input-lag/)
> so going all the way to 4MB I/Os takes us into the perceptible latency
> range, whereas a 256kB I/O is only 1ms.
>
> So could you do some experiments with fio doing direct I/O to see if
> it takes significantly longer to do, say, 1TB of I/O in 4MB chunks vs
> 256kB chunks?  Obviously use threads to keep lots of I/Os outstanding.

That is a good question and it has been months since I have done experiments
with something similar.   Obviously this will vary depending on RDMA or not and
multichannel or not - but assuming the 'normal' low end network configuration -
ie a 1Gbps link and no RDMA or multichannel I could do some more recent
experiments.

In the past what I had noticed was that server performance for simple
workloads like cp or grep increased with network I/O size to a point:
smaller than 256K packet size was bad. Performance improved
significantly from 256K to 512K to 1MB, but only very
slightly from 1MB to 2MB to 4MB and sometimes degraded at 8MB
(IIRC 8MB is the max commonly supported by SMB3 servers),
but this is with only one adapter (no multichannel) and 1Gb adapters.

But in those examples there wasn't a lot of concurrency on the wire.

I did some experiments with increasing the read ahead size
(which causes more than one async read to be issued by cifs.ko
but presumably does still result in some 'dead time')
which seemed to help perf of some sequential read examples
(e.g. grep or cp) to some servers but I didn't try enough variety
of server targets to feel confident about that change especially
if netfs is coming

e.g. a change I experimented with was:
         sb->s_bdi->ra_pages = cifs_sb->ctx->rsize / PAGE_SIZE
to
         sb->s_bdi->ra_pages = 2 * cifs_sb->ctx->rsize / PAGE_SIZE

and it did seem to help a little.

I would expect that 8x1MB (ie trying to keep eight 1MB reads in process should
keep the network mostly busy and not lead to too much dead time on
server, client
or network) and is 'good enough' in many read ahead use cases (at
least for non-RDMA, and non-multichannel on a slower network) to keep the pipe
file, and I would expect the performance to be similar to the equivalent using
2MB read (e.g. 4x2MB) and perhaps better than 2x4MB.  Below 1MB i/o size
on the wire I would expect to see degradation due to packet processing
and task switching
overhead.  Would definitely be worth doing more experimentation here.
-- 
Thanks,

Steve

Re: [f2fs-dev] [PATCH 00/33] Network fs helper library & fscache kiocb API [ver #3]

[Steve French]

On Tue, Feb 23, 2021 at 2:28 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Mon, Feb 15, 2021 at 11:22:20PM -0600, Steve French wrote:
> > On Mon, Feb 15, 2021 at 8:10 PM Matthew Wilcox <willy@infradead.org> wrote:
> > > The switch from readpages to readahead does help in a couple of corner
> > > cases.  For example, if you have two processes reading the same file at
> > > the same time, one will now block on the other (due to the page lock)
> > > rather than submitting a mess of overlapping and partial reads.
> >
> > Do you have a simple repro example of this we could try (fio, dbench, iozone
> > etc) to get some objective perf data?
>
> I don't.  The problem was noted by the f2fs people, so maybe they have a
> reproducer.
>
> > My biggest worry is making sure that the switch to netfs doesn't degrade
> > performance (which might be a low bar now since current network file copy
> > perf seems to signifcantly lag at least Windows), and in some easy to understand
> > scenarios want to make sure it actually helps perf.
>
> I had a question about that ... you've mentioned having 4x4MB reads
> outstanding as being the way to get optimum performance.  Is there a
> significant performance difference between 4x4MB, 16x1MB and 64x256kB?
> I'm concerned about having "too large" an I/O on the wire at a given time.
> For example, with a 1Gbps link, you get 250MB/s.  That's a minimum
> latency of 16us for a 4kB page, but 16ms for a 4MB page.
>
> "For very simple tasks, people can perceive latencies down to 2 ms or less"
> (https://danluu.com/input-lag/)
> so going all the way to 4MB I/Os takes us into the perceptible latency
> range, whereas a 256kB I/O is only 1ms.
>
> So could you do some experiments with fio doing direct I/O to see if
> it takes significantly longer to do, say, 1TB of I/O in 4MB chunks vs
> 256kB chunks?  Obviously use threads to keep lots of I/Os outstanding.

That is a good question and it has been months since I have done experiments
with something similar.   Obviously this will vary depending on RDMA or not and
multichannel or not - but assuming the 'normal' low end network configuration -
ie a 1Gbps link and no RDMA or multichannel I could do some more recent
experiments.

In the past what I had noticed was that server performance for simple
workloads like cp or grep increased with network I/O size to a point:
smaller than 256K packet size was bad. Performance improved
significantly from 256K to 512K to 1MB, but only very
slightly from 1MB to 2MB to 4MB and sometimes degraded at 8MB
(IIRC 8MB is the max commonly supported by SMB3 servers),
but this is with only one adapter (no multichannel) and 1Gb adapters.

But in those examples there wasn't a lot of concurrency on the wire.

I did some experiments with increasing the read ahead size
(which causes more than one async read to be issued by cifs.ko
but presumably does still result in some 'dead time')
which seemed to help perf of some sequential read examples
(e.g. grep or cp) to some servers but I didn't try enough variety
of server targets to feel confident about that change especially
if netfs is coming

e.g. a change I experimented with was:
         sb->s_bdi->ra_pages = cifs_sb->ctx->rsize / PAGE_SIZE
to
         sb->s_bdi->ra_pages = 2 * cifs_sb->ctx->rsize / PAGE_SIZE

and it did seem to help a little.

I would expect that 8x1MB (ie trying to keep eight 1MB reads in process should
keep the network mostly busy and not lead to too much dead time on
server, client
or network) and is 'good enough' in many read ahead use cases (at
least for non-RDMA, and non-multichannel on a slower network) to keep the pipe
file, and I would expect the performance to be similar to the equivalent using
2MB read (e.g. 4x2MB) and perhaps better than 2x4MB.  Below 1MB i/o size
on the wire I would expect to see degradation due to packet processing
and task switching
overhead.  Would definitely be worth doing more experimentation here.
-- 
Thanks,

Steve


_______________________________________________
Linux-f2fs-devel mailing list
Linux-f2fs-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel

Re: [PATCH 00/33] Network fs helper library & fscache kiocb API [ver #3]

[David Howells]

Steve French <smfrench@gmail.com> wrote:

> This (readahead behavior improvements in Linux, on single large file
> sequential read workloads like cp or grep) gets particularly interesting
> with SMB3 as multichannel becomes more common.  With one channel having one
> readahead request pending on the network is suboptimal - but not as bad as
> when multichannel is negotiated. Interestingly in most cases two network
> connections to the same server (different TCP sockets,but the same mount,
> even in cases where only network adapter) can achieve better performance -
> but still significantly lags Windows (and probably other clients) as in
> Linux we don't keep multiple I/Os in flight at one time (unless different
> files are being read at the same time by different threads).

I think it should be relatively straightforward to make the netfs_readahead()
function generate multiple read requests.  If I wasn't handed sufficient pages
by the VM upfront to do two or more read requests, I would need to do extra
expansion.  There are a couple of ways this could be done:

 (1) I could expand the readahead_control after fully starting a read request
     and then create another independent read request, and another for how
     ever many we want.

 (2) I could expand the readahead_control first to cover however many requests
     I'm going to generate, then chop it up into individual read requests.

However, generating larger requests means we're more likely to run into a
problem for the cache: if we can't allocate enough pages to fill out a cache
block, we don't have enough data to write to the cache.  Further, if the pages
are just unlocked and abandoned, readpage will be called to read them
individually - which means they likely won't get cached unless the cache
granularity is PAGE_SIZE.  But that's probably okay if ENOMEM occurred.

There are some other considerations too:

 (*) I would need to query the filesystem to find out if I should create
     another request.  The fs would have to keep track of how many I/O reqs
     are in flight and what the limit is.

 (*) How and where should the readahead triggers be emplaced?  I'm guessing
     that each block would need a trigger and that this should cause more
     requests to be generated until we hit the limit.

 (*) I would probably need to shuffle the request generation for the second
     and subsequent blocks in a single netfs_readahead() call to a worker
     thread because it'll probably be in a userspace kernel-side context and
     blocking an application from proceeding and consuming the pages already
     committed.

David

Re: [PATCH 00/33] Network fs helper library & fscache kiocb API [ver #3]

[Matthew Wilcox]

On Wed, Feb 24, 2021 at 01:32:02PM +0000, David Howells wrote:
> Steve French <smfrench@gmail.com> wrote:
> 
> > This (readahead behavior improvements in Linux, on single large file
> > sequential read workloads like cp or grep) gets particularly interesting
> > with SMB3 as multichannel becomes more common.  With one channel having one
> > readahead request pending on the network is suboptimal - but not as bad as
> > when multichannel is negotiated. Interestingly in most cases two network
> > connections to the same server (different TCP sockets,but the same mount,
> > even in cases where only network adapter) can achieve better performance -
> > but still significantly lags Windows (and probably other clients) as in
> > Linux we don't keep multiple I/Os in flight at one time (unless different
> > files are being read at the same time by different threads).
> 
> I think it should be relatively straightforward to make the netfs_readahead()
> function generate multiple read requests.  If I wasn't handed sufficient pages
> by the VM upfront to do two or more read requests, I would need to do extra
> expansion.  There are a couple of ways this could be done:

I don't think this is a job for netfs_readahead().  We can get into a
similar situation with SSDs or RAID arrays where ideally we would have
several outstanding readahead requests.

If your drive is connected through a 1Gbps link (eg PCIe gen 1 x1) and
has a latency of 10ms seek time, with one outstanding read, each read
needs to be 12.5MB in size in order to saturate the bus.  If the device
supports 128 outstanding commands, each read need only be 100kB.

We need the core readahead code to handle this situation.  My suggestion
for doing this is to send off an extra readahead request every time we
hit a !Uptodate page.  It looks something like this (assuming the app
is processing the data fast and always hits the !Uptodate case) ...

1. hit 0,
	set readahead size to 64kB,
	mark 32kB as Readahead, send read for 0-64kB
	wait for 0-64kB to complete
2. hit 32kB (Readahead), no reads outstanding
	inc readahead size to 128kB,
	mark 128kB as Readahead, send read for 64k-192kB
3. hit 64kB (!Uptodate), one read outstanding
	mark 256kB as Readahead, send read for 192-320kB
	mark 384kB as Readahead, send read for 320-448kB
	wait for 64-192kB to complete
4. hit 128kB (Readahead), two reads outstanding
	inc readahead size to 256kB,
	mark 576kB as Readahead, send read for 448-704kB
5. hit 192kB (!Uptodate), three reads outstanding
	mark 832kB as Readahead, send read for 704-960kB
	mark 1088kB as Readahead, send read for 960-1216kB
	wait for 192-320kB to complete
6. hit 256kB (Readahead), four reads outstanding
	mark 1344kB as Readahead, send read for 1216-1472kB
7. hit 320kB (!Uptodate), five reads outstanding
	mark 1600kB as Readahead, send read for 1472-1728kB
	mark 1856kB as Readahead, send read for 1728-1984kB
	wait for 320-448kB to complete
8. hit 384kB (Readahead), five reads outstanding
	mark 2112kB as Readahead, send read for 1984-2240kB
9. hit 448kB (!Uptodate), six reads outstanding
	mark 2368kB as Readahead, send read for 2240-2496kB
	mark 2624kB as Readahead, send read for 2496-2752kB
	wait for 448-704kB to complete
10. hit 576kB (Readahead), seven reads outstanding
	mark 2880kB as Readahead, send read for 2752-3008kB

...

Once we stop hitting !Uptodate pages, we'll maintain the number of pages
marked as Readahead, and thus keep the number of readahead requests
at the level it determined was necessary to keep the link saturated.
I think we may need to put a parallelism cap in the bdi so that a device
which is just slow instead of at the end of a long fat pipe doesn't get
overwhelmed with requests.