[PATCH 00/11] netfs: Further miscellaneous fixes

[PATCH 00/11] netfs: Further miscellaneous fixes

[David Howells]

Hi Christian,

Here are some more miscellaneous fixes for netfslib, found by Sashiko.dev's
AI review[1] in response to the previous miscellaneous fix posting[2], plus
a repeat of another patch you haven't picked up yet:

 (1) Fix an early put of the sink page used in netfs_read_gaps(), before
     the request has completed.

 (2) Fix request leak in netfs_write_begin() error handling.

 (3) Fix a potential UAF in netfs_unlock_abandoned_read_pages() due to
     trying to check index of each folio we're abandoning to see if that
     folio is actually owned by the caller (in which case, we're not
     actually allowed to dereference it).

 (4) Fix a potentially uninitialised error value in
     netfs_extract_user_iter().

 (5) Fix incorrect adjustment of dirty region when partially invalidating a
     streaming write folio.

 (6) Fix the trace displayed by the total overwrite of a streaming-write
     folio.

 (7) Fix the handling of folio->private in netfs_perform_write() and the
     attached netfs_folio and/or group when a streaming write folio is
     modified.

 (8) Fix the handling of a group attached to the netfs_folio attached to
     folio->private when netfs_read_gaps() fills out the folio.

 (9) Fix the potential for 64-bit tearing on a 32-bit machine when reading
     netfs_inode->remote_i_size and ->zero_point by using much the same
     mechanism as is used for ->i_size.

(10) Fix a comment about avoiding streaming write on O_RDWR files as that
     bit of code is removed in vfs.fixes.  This could be folded down, but
     makes no change of behaviour.

(11) Fix netfs_read_folio() to wait on writeback first (it holds the folio
     lock) otherwise we aren't allowed to look at the netfs_folio struct as
     that could be modified at any time by the writeback collector.

These are applied on top of your vfs.fixes branch.  Patch 6 fixes a commit
in vfs.fixes, but would need moving before that patch rather than simply
folding down - and as it just changes the trace output, it's probably not
worth moving.  Patch 8 fixes a bug in one of the commits in vfs.fixes.
Patch 10 just tidies up a comment in one of the vfs.fixes commits.

The patches can also be found here:

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

Thanks,
David

[1] https://sashiko.dev/#/patchset/20260414082004.3756080-1-dhowells%40redhat.com

[2] https://lore.kernel.org/r/20260414082004.3756080-1-dhowells@redhat.com/

David Howells (11):
  netfs: Fix early put of sink folio in netfs_read_gaps()
  netfs: Fix leak of request in netfs_write_begin() error handling
  netfs: Fix potential UAF in netfs_unlock_abandoned_read_pages()
  netfs: Fix potential uninitialised var in netfs_extract_user_iter()
  netfs: Fix partial invalidation of streaming-write folio
  netfs: Fix the trace displayed for the total overwrite of a streamed
    write
  netfs: Fix folio->private handling in netfs_perform_write()
  netfs: Fix group handling in netfs_read_gaps()
  netfs: Fix potential for tearing in ->remote_i_size and ->zero_point
  netfs: Fix comment about write-streaming avoidance
  netfs: Fix netfs_read_folio() to wait on writeback

 fs/9p/vfs_inode.c            |   2 +-
 fs/9p/vfs_inode_dotl.c       |   4 +-
 fs/afs/inode.c               |   8 +-
 fs/afs/write.c               |   2 +-
 fs/netfs/buffered_read.c     |  25 +--
 fs/netfs/buffered_write.c    | 100 +++++++-----
 fs/netfs/direct_write.c      |   4 +-
 fs/netfs/iterator.c          |   2 +-
 fs/netfs/misc.c              |  15 +-
 fs/netfs/read_collect.c      |   2 +-
 fs/netfs/read_retry.c        |   2 +-
 fs/netfs/write_collect.c     |   3 +-
 fs/smb/client/cifsfs.c       |  24 +--
 fs/smb/client/cifssmb.c      |   2 +-
 fs/smb/client/file.c         |   9 +-
 fs/smb/client/inode.c        |   9 +-
 fs/smb/client/readdir.c      |   3 +-
 fs/smb/client/smb2ops.c      |  16 +-
 fs/smb/client/smb2pdu.c      |   2 +-
 include/linux/netfs.h        | 301 +++++++++++++++++++++++++++++++++--
 include/trace/events/netfs.h |   3 +
 21 files changed, 426 insertions(+), 112 deletions(-)

[PATCH 01/11] netfs: Fix early put of sink folio in netfs_read_gaps()

[David Howells]

Fix netfs_read_gaps() to release the sink page it uses after waiting for
the request to complete.  The way the sink page is used is that an
ITER_BVEC-class iterator is created that has the gaps from the target folio
at either end, but has the sink page tiled over the middle so that a single
read op can fill in both gaps.

The bug was found by KASAN detecting a UAF on the generic/075 xfstest in
the cifsd kernel thread that handles reception of data from the TCP socket:

 BUG: KASAN: use-after-free in _copy_to_iter+0x48a/0xa20
 Write of size 885 at addr ffff888107f92000 by task cifsd/1285
 CPU: 2 UID: 0 PID: 1285 Comm: cifsd Not tainted 7.0.0 #6 PREEMPT(lazy)
 Call Trace:
  dump_stack_lvl+0x5d/0x80
  print_report+0x17f/0x4f1
  kasan_report+0x100/0x1e0
  kasan_check_range+0x10f/0x1e0
  __asan_memcpy+0x3c/0x60
  _copy_to_iter+0x48a/0xa20
  __skb_datagram_iter+0x2c9/0x430
  skb_copy_datagram_iter+0x6e/0x160
  tcp_recvmsg_locked+0xce0/0x1130
  tcp_recvmsg+0xeb/0x300
  inet_recvmsg+0xcf/0x3a0
  sock_recvmsg+0xea/0x100
  cifs_readv_from_socket+0x3a6/0x4d0 [cifs]
  cifs_read_iter_from_socket+0xdd/0x130 [cifs]
  cifs_readv_receive+0xaad/0xb10 [cifs]
  cifs_demultiplex_thread+0x1148/0x1740 [cifs]
  kthread+0x1cf/0x210

Fixes: ee4cdf7ba857 ("netfs: Speed up buffered reading")
Reported-by: Steve French <sfrench@samba.org>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Paulo Alcantara <pc@manguebit.org>
cc: Matthew Wilcox <willy@infradead.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
---
 fs/netfs/buffered_read.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c
index c23173a061e8..dc50690fdd44 100644
--- a/fs/netfs/buffered_read.c
+++ b/fs/netfs/buffered_read.c
@@ -459,9 +459,6 @@ static int netfs_read_gaps(struct file *file, struct folio *folio)
 
 	netfs_read_to_pagecache(rreq, NULL);
 
-	if (sink)
-		folio_put(sink);
-
 	ret = netfs_wait_for_read(rreq);
 	if (ret >= 0) {
 		folio_detach_private(folio);
@@ -471,6 +468,9 @@ static int netfs_read_gaps(struct file *file, struct folio *folio)
 		flush_dcache_folio(folio);
 		folio_mark_uptodate(folio);
 	}
+
+	if (sink)
+		folio_put(sink);
 	folio_unlock(folio);
 	netfs_put_request(rreq, netfs_rreq_trace_put_return);
 	return ret < 0 ? ret : 0;

[PATCH 02/11] netfs: Fix leak of request in netfs_write_begin() error handling

[David Howells]

Fix netfs_write_begin() to not leak our ref on the request in the event
that we get an error from netfs_wait_for_read().

Fixes: 4090b31422a6 ("netfs: Add a function to consolidate beginning a read")
Closes: https://sashiko.dev/#/patchset/20260414082004.3756080-1-dhowells%40redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Paulo Alcantara <pc@manguebit.org>
cc: Matthew Wilcox <willy@infradead.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
---
 fs/netfs/buffered_read.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c
index dc50690fdd44..51caad535438 100644
--- a/fs/netfs/buffered_read.c
+++ b/fs/netfs/buffered_read.c
@@ -688,7 +688,7 @@ int netfs_write_begin(struct netfs_inode *ctx,
 	netfs_read_to_pagecache(rreq, NULL);
 	ret = netfs_wait_for_read(rreq);
 	if (ret < 0)
-		goto error;
+		goto error_put;
 	netfs_put_request(rreq, netfs_rreq_trace_put_return);
 
 have_folio:

[PATCH 03/11] netfs: Fix potential UAF in netfs_unlock_abandoned_read_pages()

[David Howells]

netfs_unlock_abandoned_read_pages(rreq) accesses the index of the folios it
is wanting to unlock and compares that to rreq->no_unlock_folio so that it
doesn't unlock a folio being read for netfs_perform_write() or
netfs_write_begin().

However, given that netfs_unlock_abandoned_read_pages() is called _after_
NETFS_RREQ_IN_PROGRESS is cleared, the one folio that it's not allowed to
dereference is the one specified by ->no_unlock_folio as ownership
immediately reverts to the caller.

Fix this by storing the folio pointer instead and using that rather than
the index.  Also fix netfs_unlock_read_folio() where the same applies.

Fixes: ee4cdf7ba857 ("netfs: Speed up buffered reading")
Closes: https://sashiko.dev/#/patchset/20260414082004.3756080-1-dhowells%40redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Paulo Alcantara <pc@manguebit.org>
cc: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
cc: Matthew Wilcox <willy@infradead.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
---
 fs/netfs/buffered_read.c | 4 ++--
 fs/netfs/read_collect.c  | 2 +-
 fs/netfs/read_retry.c    | 2 +-
 include/linux/netfs.h    | 2 +-
 4 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c
index 51caad535438..b4d271538f75 100644
--- a/fs/netfs/buffered_read.c
+++ b/fs/netfs/buffered_read.c
@@ -670,7 +670,7 @@ int netfs_write_begin(struct netfs_inode *ctx,
 		ret = PTR_ERR(rreq);
 		goto error;
 	}
-	rreq->no_unlock_folio	= folio->index;
+	rreq->no_unlock_folio	= folio;
 	__set_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags);
 
 	ret = netfs_begin_cache_read(rreq, ctx);
@@ -736,7 +736,7 @@ int netfs_prefetch_for_write(struct file *file, struct folio *folio,
 		goto error;
 	}
 
-	rreq->no_unlock_folio = folio->index;
+	rreq->no_unlock_folio = folio;
 	__set_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags);
 	ret = netfs_begin_cache_read(rreq, ctx);
 	if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
diff --git a/fs/netfs/read_collect.c b/fs/netfs/read_collect.c
index e5f6665b3341..eae067e3eaa5 100644
--- a/fs/netfs/read_collect.c
+++ b/fs/netfs/read_collect.c
@@ -83,7 +83,7 @@ static void netfs_unlock_read_folio(struct netfs_io_request *rreq,
 	}
 
 just_unlock:
-	if (folio->index == rreq->no_unlock_folio &&
+	if (folio == rreq->no_unlock_folio &&
 	    test_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags)) {
 		_debug("no unlock");
 	} else {
diff --git a/fs/netfs/read_retry.c b/fs/netfs/read_retry.c
index 68fc869513ef..999177426141 100644
--- a/fs/netfs/read_retry.c
+++ b/fs/netfs/read_retry.c
@@ -288,7 +288,7 @@ void netfs_unlock_abandoned_read_pages(struct netfs_io_request *rreq)
 			struct folio *folio = folioq_folio(p, slot);
 
 			if (folio && !folioq_is_marked2(p, slot)) {
-				if (folio->index == rreq->no_unlock_folio &&
+				if (folio == rreq->no_unlock_folio &&
 				    test_bit(NETFS_RREQ_NO_UNLOCK_FOLIO,
 					     &rreq->flags)) {
 					_debug("no unlock");
diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index ba17ac5bf356..62a528f90666 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -252,7 +252,7 @@ struct netfs_io_request {
 	unsigned long long	collected_to;	/* Point we've collected to */
 	unsigned long long	cleaned_to;	/* Position we've cleaned folios to */
 	unsigned long long	abandon_to;	/* Position to abandon folios to */
-	pgoff_t			no_unlock_folio; /* Don't unlock this folio after read */
+	const struct folio	*no_unlock_folio; /* Don't unlock this folio after read */
 	unsigned int		direct_bv_count; /* Number of elements in direct_bv[] */
 	unsigned int		debug_id;
 	unsigned int		rsize;		/* Maximum read size (0 for none) */

[PATCH 04/11] netfs: Fix potential uninitialised var in netfs_extract_user_iter()

[David Howells]

In netfs_extract_user_iter(), if it's given a zero-length iterator, it will
fall through the loop without setting ret, and so the error handling
behaviour will be undefined, depending on whether ret happens to be
negative.  The value of ret then propagates back up the callstack.

Fix this by presetting ret to 0.

Fixes: 85dd2c8ff368 ("netfs: Add a function to extract a UBUF or IOVEC into a BVEC iterator")
Closes: https://sashiko.dev/#/patchset/20260414082004.3756080-1-dhowells%40redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Paulo Alcantara <pc@manguebit.org>
cc: Matthew Wilcox <willy@infradead.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
---
 fs/netfs/iterator.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/netfs/iterator.c b/fs/netfs/iterator.c
index adca78747f23..429e4396e1b0 100644
--- a/fs/netfs/iterator.c
+++ b/fs/netfs/iterator.c
@@ -43,7 +43,7 @@ ssize_t netfs_extract_user_iter(struct iov_iter *orig, size_t orig_len,
 	unsigned int max_pages;
 	unsigned int npages = 0;
 	unsigned int i;
-	ssize_t ret;
+	ssize_t ret = 0;
 	size_t count = orig_len, offset, len;
 	size_t bv_size, pg_size;
 

[PATCH 05/11] netfs: Fix partial invalidation of streaming-write folio

[David Howells]

In netfs_invalidate_folio(), if the region of a partial invalidation
overlaps the front (but not all) of a dirty write cached in a streaming
write page (dirty, but not uptodate, with the dirty region tracked by a
netfs_folio struct), the function modifies the dirty region - but
incorrectly as it moves the region forward by setting the start to the
start, not the end, of the invalidation region.

Fix this by setting finfo->dirty_offset to the end of the invalidation
region (iend).

Fixes: cce6bfa6ca0e ("netfs: Fix trimming of streaming-write folios in netfs_inval_folio()")
Closes: https://sashiko.dev/#/patchset/20260414082004.3756080-1-dhowells%40redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Paulo Alcantara <pc@manguebit.org>
cc: Matthew Wilcox <willy@infradead.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
---
 fs/netfs/misc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/netfs/misc.c b/fs/netfs/misc.c
index e386cf31eb1e..8b457124b0e3 100644
--- a/fs/netfs/misc.c
+++ b/fs/netfs/misc.c
@@ -255,7 +255,7 @@ void netfs_invalidate_folio(struct folio *folio, size_t offset, size_t length)
 				goto erase_completely;
 			/* Move the start of the data. */
 			finfo->dirty_len = fend - iend;
-			finfo->dirty_offset = offset;
+			finfo->dirty_offset = iend;
 			trace_netfs_folio(folio, netfs_folio_trace_invalidate_front);
 			return;
 		}

[PATCH 06/11] netfs: Fix the trace displayed for the total overwrite of a streamed write

[David Howells]

Change netfs_perform_write() to carry the trace value in a variable and
emit it later to make it easier to select the value displayed.

Fix the display of netfs_streaming_write_cont in the "folio_now_filled:"
section.  It should only be set to that if we come from the section that
filled in a gap in an already streamed write (and would otherwise display
netfs_streaming_write_cont).  If it came from the bit that just overwrites
the entire folio (which would ordinarily display netfs_whole_folio_modify),
make it display netfs_whole_folio_modify_filled instead.

Fixes: 1bfeb53e990b ("netfs: Fix streaming write being overwritten")
Closes: https://sashiko.dev/#/patchset/20260414082004.3756080-1-dhowells%40redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Paulo Alcantara <pc@manguebit.org>
cc: Matthew Wilcox <willy@infradead.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
---
 fs/netfs/buffered_write.c    | 27 ++++++++++++++++-----------
 include/trace/events/netfs.h |  1 +
 2 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/fs/netfs/buffered_write.c b/fs/netfs/buffered_write.c
index 6399141b4f0a..de82eb6ed473 100644
--- a/fs/netfs/buffered_write.c
+++ b/fs/netfs/buffered_write.c
@@ -150,6 +150,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 	}
 
 	do {
+		enum netfs_folio_trace trace;
 		struct netfs_folio *finfo;
 		struct netfs_group *group;
 		unsigned long long fpos;
@@ -223,7 +224,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 			if (unlikely(copied == 0))
 				goto copy_failed;
 			netfs_set_group(folio, netfs_group);
-			trace_netfs_folio(folio, netfs_folio_is_uptodate);
+			trace = netfs_folio_is_uptodate;
 			goto copied;
 		}
 
@@ -239,7 +240,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 			folio_zero_segment(folio, offset + copied, flen);
 			__netfs_set_group(folio, netfs_group);
 			folio_mark_uptodate(folio);
-			trace_netfs_folio(folio, netfs_modify_and_clear);
+			trace = netfs_modify_and_clear;
 			goto copied;
 		}
 
@@ -247,11 +248,13 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 		if (!maybe_trouble && offset == 0 && part >= flen) {
 			copied = copy_folio_from_iter_atomic(folio, offset, part, iter);
 			if (likely(copied == part)) {
-				if (finfo)
+				if (finfo) {
+					trace = netfs_whole_folio_modify_filled;
 					goto folio_now_filled;
+				}
 				__netfs_set_group(folio, netfs_group);
 				folio_mark_uptodate(folio);
-				trace_netfs_folio(folio, netfs_whole_folio_modify);
+				trace = netfs_whole_folio_modify;
 				goto copied;
 			}
 			if (copied == 0)
@@ -273,7 +276,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 			if (copied > finfo->dirty_len)
 				finfo->dirty_len = copied;
 			finfo->dirty_offset = 0;
-			trace_netfs_folio(folio, netfs_whole_folio_modify_efault);
+			trace = netfs_whole_folio_modify_efault;
 			goto copied;
 		}
 
@@ -299,7 +302,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 			if (unlikely(copied == 0))
 				goto copy_failed;
 			netfs_set_group(folio, netfs_group);
-			trace_netfs_folio(folio, netfs_just_prefetch);
+			trace = netfs_just_prefetch;
 			goto copied;
 		}
 
@@ -313,7 +316,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 			if (offset == 0 && copied == flen) {
 				__netfs_set_group(folio, netfs_group);
 				folio_mark_uptodate(folio);
-				trace_netfs_folio(folio, netfs_streaming_filled_page);
+				trace = netfs_streaming_filled_page;
 				goto copied;
 			}
 
@@ -328,7 +331,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 			finfo->dirty_len = copied;
 			folio_attach_private(folio, (void *)((unsigned long)finfo |
 							     NETFS_FOLIO_INFO));
-			trace_netfs_folio(folio, netfs_streaming_write);
+			trace = netfs_streaming_write;
 			goto copied;
 		}
 
@@ -341,9 +344,11 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 			if (unlikely(copied == 0))
 				goto copy_failed;
 			finfo->dirty_len += copied;
-			if (finfo->dirty_offset == 0 && finfo->dirty_len == flen)
+			if (finfo->dirty_offset == 0 && finfo->dirty_len == flen) {
+				trace = netfs_streaming_cont_filled_page;
 				goto folio_now_filled;
-			trace_netfs_folio(folio, netfs_streaming_write_cont);
+			}
+			trace = netfs_streaming_write_cont;
 			goto copied;
 		}
 
@@ -364,8 +369,8 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 			folio_detach_private(folio);
 		folio_mark_uptodate(folio);
 		kfree(finfo);
-		trace_netfs_folio(folio, netfs_streaming_cont_filled_page);
 	copied:
+		trace_netfs_folio(folio, trace);
 		flush_dcache_folio(folio);
 
 		/* Update the inode size if we moved the EOF marker */
diff --git a/include/trace/events/netfs.h b/include/trace/events/netfs.h
index ee7fea84f055..67f6d56c94ce 100644
--- a/include/trace/events/netfs.h
+++ b/include/trace/events/netfs.h
@@ -178,6 +178,7 @@
 	EM(netfs_just_prefetch,			"mod-prefetch")	\
 	EM(netfs_whole_folio_modify,		"mod-whole-f")	\
 	EM(netfs_whole_folio_modify_efault,	"mod-whole-f!")	\
+	EM(netfs_whole_folio_modify_filled,	"mod-whole-f+")	\
 	EM(netfs_modify_and_clear,		"mod-n-clear")	\
 	EM(netfs_streaming_write,		"mod-streamw")	\
 	EM(netfs_streaming_write_cont,		"mod-streamw+")	\

[PATCH 07/11] netfs: Fix folio->private handling in netfs_perform_write()

[David Howells]

Under some circumstances, netfs_perform_write() doesn't correctly
manipulate folio->private between NULL, NETFS_FOLIO_COPY_TO_CACHE, pointing
to a group and pointing to a netfs_folio struct, leading to potential
multiple attachments of private data with associated folio ref leaks and
also leaks of netfs_folio structs or netfs_group refs.

Fix this by consolidating the place at which a folio is marked uptodate in
one place and having that look at what's attached to folio->private and
decide how to clean it up and then set the new group.  Also, the content
shouldn't be flushed if group is NULL, even if a group is specified in the
netfs_group parameter, as that would be the case for a new folio.  A
filesystem should always specify netfs_group or never specify netfs_group.

The Sashiko auto-review tool noted that it was theoretically possible that
the fpos >= ctx->zero_point section might leak if it modified a streaming
write folio.  This is unlikely, but with a network filesystem, third party
changes can happen.  It also pointed out that __netfs_set_group() would
leak if called multiple times on the same folio from the "whole folio
modify section".

Fixes: 8f52de0077ba ("netfs: Reduce number of conditional branches in netfs_perform_write()")
Closes: https://sashiko.dev/#/patchset/20260414082004.3756080-1-dhowells%40redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Paulo Alcantara <pc@manguebit.org>
cc: Matthew Wilcox <willy@infradead.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
---
 fs/netfs/buffered_write.c    | 77 +++++++++++++++++++++---------------
 include/trace/events/netfs.h |  2 +
 2 files changed, 48 insertions(+), 31 deletions(-)

diff --git a/fs/netfs/buffered_write.c b/fs/netfs/buffered_write.c
index de82eb6ed473..0ca8e922790d 100644
--- a/fs/netfs/buffered_write.c
+++ b/fs/netfs/buffered_write.c
@@ -13,12 +13,6 @@
 #include <linux/pagevec.h>
 #include "internal.h"
 
-static void __netfs_set_group(struct folio *folio, struct netfs_group *netfs_group)
-{
-	if (netfs_group)
-		folio_attach_private(folio, netfs_get_group(netfs_group));
-}
-
 static void netfs_set_group(struct folio *folio, struct netfs_group *netfs_group)
 {
 	void *priv = folio_get_private(folio);
@@ -158,6 +152,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 		size_t offset;	/* Offset into pagecache folio */
 		size_t part;	/* Bytes to write to folio */
 		size_t copied;	/* Bytes copied from user */
+		void *priv;
 
 		offset = pos & (max_chunk - 1);
 		part = min(max_chunk - offset, iov_iter_count(iter));
@@ -213,8 +208,9 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 		finfo = netfs_folio_info(folio);
 		group = netfs_folio_group(folio);
 
-		if (unlikely(group != netfs_group) &&
-		    group != NETFS_FOLIO_COPY_TO_CACHE)
+		if (unlikely(group) &&
+		    group != NETFS_FOLIO_COPY_TO_CACHE &&
+		    group != netfs_group)
 			goto flush_content;
 
 		if (folio_test_uptodate(folio)) {
@@ -238,24 +234,22 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 			if (unlikely(copied == 0))
 				goto copy_failed;
 			folio_zero_segment(folio, offset + copied, flen);
-			__netfs_set_group(folio, netfs_group);
-			folio_mark_uptodate(folio);
-			trace = netfs_modify_and_clear;
-			goto copied;
+			if (finfo)
+				trace = netfs_modify_and_clear_rm_finfo;
+			else
+				trace = netfs_modify_and_clear;
+			goto mark_uptodate;
 		}
 
 		/* See if we can write a whole folio in one go. */
 		if (!maybe_trouble && offset == 0 && part >= flen) {
 			copied = copy_folio_from_iter_atomic(folio, offset, part, iter);
 			if (likely(copied == part)) {
-				if (finfo) {
+				if (finfo)
 					trace = netfs_whole_folio_modify_filled;
-					goto folio_now_filled;
-				}
-				__netfs_set_group(folio, netfs_group);
-				folio_mark_uptodate(folio);
-				trace = netfs_whole_folio_modify;
-				goto copied;
+				else
+					trace = netfs_whole_folio_modify;
+				goto mark_uptodate;
 			}
 			if (copied == 0)
 				goto copy_failed;
@@ -271,8 +265,10 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 			 * accept the partial write.
 			 */
 			finfo->dirty_len += finfo->dirty_offset;
-			if (finfo->dirty_len == flen)
-				goto folio_now_filled;
+			if (finfo->dirty_len == flen) {
+				trace = netfs_whole_folio_modify_filled_efault;
+				goto mark_uptodate;
+			}
 			if (copied > finfo->dirty_len)
 				finfo->dirty_len = copied;
 			finfo->dirty_offset = 0;
@@ -306,6 +302,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 			goto copied;
 		}
 
+		/* Do a streaming write on a folio that has nothing in it yet. */
 		if (!finfo) {
 			ret = -EIO;
 			if (WARN_ON(folio_get_private(folio)))
@@ -314,10 +311,8 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 			if (unlikely(copied == 0))
 				goto copy_failed;
 			if (offset == 0 && copied == flen) {
-				__netfs_set_group(folio, netfs_group);
-				folio_mark_uptodate(folio);
 				trace = netfs_streaming_filled_page;
-				goto copied;
+				goto mark_uptodate;
 			}
 
 			finfo = kzalloc_obj(*finfo);
@@ -346,7 +341,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 			finfo->dirty_len += copied;
 			if (finfo->dirty_offset == 0 && finfo->dirty_len == flen) {
 				trace = netfs_streaming_cont_filled_page;
-				goto folio_now_filled;
+				goto mark_uptodate;
 			}
 			trace = netfs_streaming_write_cont;
 			goto copied;
@@ -362,13 +357,33 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 			goto out;
 		continue;
 
-	folio_now_filled:
-		if (finfo->netfs_group)
-			folio_change_private(folio, finfo->netfs_group);
-		else
-			folio_detach_private(folio);
+		/* Mark a folio as being up to data when we've filled it
+		 * completely.  If the folio has a group attached, then it must
+		 * be the same group, otherwise we should have flushed it out
+		 * above.  We have to get rid of the netfs_folio struct if
+		 * there was one.
+		 */
+	mark_uptodate:
+		priv = folio_get_private(folio);
+		if (likely(priv == netfs_group)) {
+			/* Already set correctly; no change required. */
+		} else if (priv == NETFS_FOLIO_COPY_TO_CACHE) {
+			if (!netfs_group)
+				folio_detach_private(folio);
+			else
+				folio_change_private(folio, netfs_get_group(netfs_group));
+		} else if (!priv) {
+			folio_attach_private(folio, netfs_get_group(netfs_group));
+		} else {
+			WARN_ON_ONCE(!finfo);
+			if (netfs_group)
+				/* finfo->netfs_group has a ref */
+				folio_change_private(folio, netfs_group);
+			else
+				folio_detach_private(folio);
+			kfree(finfo);
+		}
 		folio_mark_uptodate(folio);
-		kfree(finfo);
 	copied:
 		trace_netfs_folio(folio, trace);
 		flush_dcache_folio(folio);
diff --git a/include/trace/events/netfs.h b/include/trace/events/netfs.h
index 67f6d56c94ce..1f5e3a5af08a 100644
--- a/include/trace/events/netfs.h
+++ b/include/trace/events/netfs.h
@@ -179,7 +179,9 @@
 	EM(netfs_whole_folio_modify,		"mod-whole-f")	\
 	EM(netfs_whole_folio_modify_efault,	"mod-whole-f!")	\
 	EM(netfs_whole_folio_modify_filled,	"mod-whole-f+")	\
+	EM(netfs_whole_folio_modify_filled_efault, "mod-whole-f+!")	\
 	EM(netfs_modify_and_clear,		"mod-n-clear")	\
+	EM(netfs_modify_and_clear_rm_finfo,	"mod-n-clear+")	\
 	EM(netfs_streaming_write,		"mod-streamw")	\
 	EM(netfs_streaming_write_cont,		"mod-streamw+")	\
 	EM(netfs_flush_content,			"flush")	\

[PATCH 08/11] netfs: Fix group handling in netfs_read_gaps()

[David Howells]

Fix netfs_read_gaps() to not discard the group information from the
netfs_folio struct after successfully reading the gaps.  This is still
needed to write back the dirty data.

Fixes: d259cfb7dd32 ("netfs: Fix read-gaps to remove netfs_folio from filled folio")
Closes: https://sashiko.dev/#/patchset/20260414082004.3756080-1-dhowells%40redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Paulo Alcantara <pc@manguebit.org>
cc: Matthew Wilcox <willy@infradead.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
---
 fs/netfs/buffered_read.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c
index b4d271538f75..98bfec0af0e1 100644
--- a/fs/netfs/buffered_read.c
+++ b/fs/netfs/buffered_read.c
@@ -461,8 +461,10 @@ static int netfs_read_gaps(struct file *file, struct folio *folio)
 
 	ret = netfs_wait_for_read(rreq);
 	if (ret >= 0) {
-		folio_detach_private(folio);
-		netfs_put_group(group);
+		if (group)
+			folio_change_private(folio, group);
+		else
+			folio_detach_private(folio);
 		kfree(finfo);
 		trace_netfs_folio(folio, netfs_folio_trace_filled_gaps);
 		flush_dcache_folio(folio);

[PATCH 09/11] netfs: Fix potential for tearing in ->remote_i_size and ->zero_point

[David Howells]

Fix potential tearing in using ->remote_i_size and ->zero_point by copying
i_size_read() and i_size_write() and using the same seqcount as for i_size.

Fixes: 4058f742105e ("netfs: Keep track of the actual remote file size")
Fixes: 100ccd18bb41 ("netfs: Optimise away reads above the point at which there can be no data")
Closes: https://sashiko.dev/#/patchset/20260414082004.3756080-1-dhowells%40redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Paulo Alcantara <pc@manguebit.org>
cc: Matthew Wilcox <willy@infradead.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
---
 fs/9p/vfs_inode.c         |   2 +-
 fs/9p/vfs_inode_dotl.c    |   4 +-
 fs/afs/inode.c            |   8 +-
 fs/afs/write.c            |   2 +-
 fs/netfs/buffered_read.c  |   5 +-
 fs/netfs/buffered_write.c |   2 +-
 fs/netfs/direct_write.c   |   4 +-
 fs/netfs/misc.c           |  13 +-
 fs/netfs/write_collect.c  |   3 +-
 fs/smb/client/cifsfs.c    |  24 +--
 fs/smb/client/cifssmb.c   |   2 +-
 fs/smb/client/file.c      |   9 +-
 fs/smb/client/inode.c     |   9 +-
 fs/smb/client/readdir.c   |   3 +-
 fs/smb/client/smb2ops.c   |  16 +-
 fs/smb/client/smb2pdu.c   |   2 +-
 include/linux/netfs.h     | 299 ++++++++++++++++++++++++++++++++++++--
 17 files changed, 348 insertions(+), 59 deletions(-)

diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index d1508b1fe109..b13156ac2f1f 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -1141,7 +1141,7 @@ v9fs_stat2inode(struct p9_wstat *stat, struct inode *inode,
 	mode |= inode->i_mode & ~S_IALLUGO;
 	inode->i_mode = mode;
 
-	v9inode->netfs.remote_i_size = stat->length;
+	netfs_write_remote_i_size(&v9inode->netfs, stat->length);
 	if (!(flags & V9FS_STAT2INODE_KEEP_ISIZE))
 		v9fs_i_size_write(inode, stat->length);
 	/* not real number of blocks, but 512 byte ones ... */
diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c
index 71796a89bcf4..81d6150a8ae4 100644
--- a/fs/9p/vfs_inode_dotl.c
+++ b/fs/9p/vfs_inode_dotl.c
@@ -634,7 +634,7 @@ v9fs_stat2inode_dotl(struct p9_stat_dotl *stat, struct inode *inode,
 		mode |= inode->i_mode & ~S_IALLUGO;
 		inode->i_mode = mode;
 
-		v9inode->netfs.remote_i_size = stat->st_size;
+		netfs_write_remote_i_size(&v9inode->netfs, stat->st_size);
 		if (!(flags & V9FS_STAT2INODE_KEEP_ISIZE))
 			v9fs_i_size_write(inode, stat->st_size);
 		inode->i_blocks = stat->st_blocks;
@@ -664,7 +664,7 @@ v9fs_stat2inode_dotl(struct p9_stat_dotl *stat, struct inode *inode,
 		}
 		if (!(flags & V9FS_STAT2INODE_KEEP_ISIZE) &&
 		    stat->st_result_mask & P9_STATS_SIZE) {
-			v9inode->netfs.remote_i_size = stat->st_size;
+			netfs_write_remote_i_size(&v9inode->netfs, stat->st_size);
 			v9fs_i_size_write(inode, stat->st_size);
 		}
 		if (stat->st_result_mask & P9_STATS_BLOCKS)
diff --git a/fs/afs/inode.c b/fs/afs/inode.c
index a5173434f786..06e25e1b12df 100644
--- a/fs/afs/inode.c
+++ b/fs/afs/inode.c
@@ -343,11 +343,11 @@ static void afs_apply_status(struct afs_operation *op,
 		 * idea of what the size should be that's not the same as
 		 * what's on the server.
 		 */
-		vnode->netfs.remote_i_size = status->size;
+		netfs_write_remote_i_size(&vnode->netfs, status->size);
 		if (change_size || status->size > i_size_read(inode)) {
 			afs_set_i_size(vnode, status->size);
 			if (unexpected_jump)
-				vnode->netfs.zero_point = status->size;
+				netfs_write_zero_point(&vnode->netfs, status->size);
 			inode_set_ctime_to_ts(inode, t);
 			inode_set_atime_to_ts(inode, t);
 		}
@@ -709,7 +709,7 @@ int afs_getattr(struct mnt_idmap *idmap, const struct path *path,
 		 * it, but we need to give userspace the server's size.
 		 */
 		if (S_ISDIR(inode->i_mode))
-			stat->size = vnode->netfs.remote_i_size;
+			stat->size = netfs_read_remote_i_size(&vnode->netfs);
 	} while (read_seqretry(&vnode->cb_lock, seq));
 
 	return 0;
@@ -889,7 +889,7 @@ int afs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 		 */
 		if (!(attr->ia_valid & (supported & ~ATTR_SIZE & ~ATTR_MTIME)) &&
 		    attr->ia_size < i_size &&
-		    attr->ia_size > vnode->netfs.remote_i_size) {
+		    attr->ia_size > netfs_read_remote_i_size(&vnode->netfs)) {
 			truncate_setsize(inode, attr->ia_size);
 			netfs_resize_file(&vnode->netfs, size, false);
 			fscache_resize_cookie(afs_vnode_cache(vnode),
diff --git a/fs/afs/write.c b/fs/afs/write.c
index 93ad86ff3345..a82ad996dc22 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -143,7 +143,7 @@ static void afs_issue_write_worker(struct work_struct *work)
 	afs_begin_vnode_operation(op);
 
 	op->store.write_iter	= &subreq->io_iter;
-	op->store.i_size	= umax(pos + len, vnode->netfs.remote_i_size);
+	op->store.i_size	= umax(pos + len, netfs_read_remote_i_size(&vnode->netfs));
 	op->mtime		= inode_get_mtime(&vnode->netfs.inode);
 
 	afs_wait_for_operation(op);
diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c
index 98bfec0af0e1..4d6dfcffba78 100644
--- a/fs/netfs/buffered_read.c
+++ b/fs/netfs/buffered_read.c
@@ -236,7 +236,8 @@ static void netfs_read_to_pagecache(struct netfs_io_request *rreq,
 		source = netfs_cache_prepare_read(rreq, subreq, rreq->i_size);
 		subreq->source = source;
 		if (source == NETFS_DOWNLOAD_FROM_SERVER) {
-			unsigned long long zp = umin(ictx->zero_point, rreq->i_size);
+			unsigned long long zero_point = netfs_read_zero_point(ictx);
+			unsigned long long zp = umin(zero_point, rreq->i_size);
 			size_t len = subreq->len;
 
 			if (unlikely(rreq->origin == NETFS_READ_SINGLE))
@@ -252,7 +253,7 @@ static void netfs_read_to_pagecache(struct netfs_io_request *rreq,
 				pr_err("ZERO-LEN READ: R=%08x[%x] l=%zx/%zx s=%llx z=%llx i=%llx",
 				       rreq->debug_id, subreq->debug_index,
 				       subreq->len, size,
-				       subreq->start, ictx->zero_point, rreq->i_size);
+				       subreq->start, zero_point, rreq->i_size);
 				break;
 			}
 			subreq->len = len;
diff --git a/fs/netfs/buffered_write.c b/fs/netfs/buffered_write.c
index 0ca8e922790d..c840f5448178 100644
--- a/fs/netfs/buffered_write.c
+++ b/fs/netfs/buffered_write.c
@@ -228,7 +228,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 		 * server would just return a block of zeros or a short read if
 		 * we try to read it.
 		 */
-		if (fpos >= ctx->zero_point) {
+		if (fpos >= netfs_read_zero_point(ctx)) {
 			folio_zero_segment(folio, 0, offset);
 			copied = copy_folio_from_iter_atomic(folio, offset, part, iter);
 			if (unlikely(copied == 0))
diff --git a/fs/netfs/direct_write.c b/fs/netfs/direct_write.c
index f9ab69de3e29..96c1dad04168 100644
--- a/fs/netfs/direct_write.c
+++ b/fs/netfs/direct_write.c
@@ -376,8 +376,8 @@ ssize_t netfs_unbuffered_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	if (ret < 0)
 		goto out;
 	end = iocb->ki_pos + iov_iter_count(from);
-	if (end > ictx->zero_point)
-		ictx->zero_point = end;
+	if (end > netfs_read_zero_point(ictx))
+		netfs_write_zero_point(ictx, end);
 
 	fscache_invalidate(netfs_i_cookie(ictx), NULL, i_size_read(inode),
 			   FSCACHE_INVAL_DIO_WRITE);
diff --git a/fs/netfs/misc.c b/fs/netfs/misc.c
index 8b457124b0e3..1f09733e50a8 100644
--- a/fs/netfs/misc.c
+++ b/fs/netfs/misc.c
@@ -221,8 +221,8 @@ void netfs_invalidate_folio(struct folio *folio, size_t offset, size_t length)
 		unsigned long long fpos = folio_pos(folio), end;
 
 		end = umin(fpos + flen, i_size);
-		if (fpos < i_size && end > ctx->zero_point)
-			ctx->zero_point = end;
+		if (fpos < i_size && end > netfs_read_zero_point(ctx))
+			netfs_write_zero_point(ctx, end);
 	}
 
 	folio_wait_private_2(folio); /* [DEPRECATED] */
@@ -297,14 +297,15 @@ EXPORT_SYMBOL(netfs_invalidate_folio);
 bool netfs_release_folio(struct folio *folio, gfp_t gfp)
 {
 	struct netfs_inode *ctx = netfs_inode(folio_inode(folio));
-	unsigned long long end;
+	unsigned long long remote_i_size, zero_point, end;
 
 	if (folio_test_dirty(folio))
 		return false;
 
-	end = umin(folio_next_pos(folio), ctx->remote_i_size);
-	if (end > ctx->zero_point)
-		ctx->zero_point = end;
+	netfs_read_sizes(ctx, &remote_i_size, &zero_point);
+	end = umin(folio_next_pos(folio), remote_i_size);
+	if (end > zero_point)
+		netfs_write_zero_point(ctx, end);
 
 	if (folio_test_private(folio))
 		return false;
diff --git a/fs/netfs/write_collect.c b/fs/netfs/write_collect.c
index b194447f4b11..4718e5174d65 100644
--- a/fs/netfs/write_collect.c
+++ b/fs/netfs/write_collect.c
@@ -69,8 +69,7 @@ int netfs_folio_written_back(struct folio *folio)
 		unsigned long long fend;
 
 		fend = folio_pos(folio) + finfo->dirty_offset + finfo->dirty_len;
-		if (fend > ictx->zero_point)
-			ictx->zero_point = fend;
+		netfs_push_back_zero_point(ictx, fend);
 
 		folio_detach_private(folio);
 		group = finfo->netfs_group;
diff --git a/fs/smb/client/cifsfs.c b/fs/smb/client/cifsfs.c
index 2025739f070a..382dccbc3507 100644
--- a/fs/smb/client/cifsfs.c
+++ b/fs/smb/client/cifsfs.c
@@ -471,7 +471,8 @@ cifs_alloc_inode(struct super_block *sb)
 	spin_lock_init(&cifs_inode->writers_lock);
 	cifs_inode->writers = 0;
 	cifs_inode->netfs.inode.i_blkbits = 14;  /* 2**14 = CIFS_MAX_MSGSIZE */
-	cifs_inode->netfs.remote_i_size = 0;
+	cifs_inode->netfs._remote_i_size = 0;
+	cifs_inode->netfs._zero_point = 0;
 	cifs_inode->uniqueid = 0;
 	cifs_inode->createtime = 0;
 	cifs_inode->epoch = 0;
@@ -1340,7 +1341,7 @@ static loff_t cifs_remap_file_range(struct file *src_file, loff_t off,
 	struct cifsFileInfo *smb_file_src = src_file->private_data;
 	struct cifsFileInfo *smb_file_target = dst_file->private_data;
 	struct cifs_tcon *target_tcon, *src_tcon;
-	unsigned long long destend, fstart, fend, old_size, new_size;
+	unsigned long long destend, fstart, fend, old_size, new_size, zero_point;
 	unsigned int xid;
 	int rc;
 
@@ -1384,7 +1385,7 @@ static loff_t cifs_remap_file_range(struct file *src_file, loff_t off,
 	 * Advance the EOF marker after the flush above to the end of the range
 	 * if it's short of that.
 	 */
-	if (src_cifsi->netfs.remote_i_size < off + len) {
+	if (netfs_read_remote_i_size(&src_cifsi->netfs) < off + len) {
 		rc = cifs_precopy_set_eof(src_inode, src_cifsi, src_tcon, xid, off + len);
 		if (rc < 0)
 			goto unlock;
@@ -1405,9 +1406,10 @@ static loff_t cifs_remap_file_range(struct file *src_file, loff_t off,
 	rc = cifs_flush_folio(target_inode, destend, &fstart, &fend, false);
 	if (rc)
 		goto unlock;
-	if (fend > target_cifsi->netfs.zero_point)
-		target_cifsi->netfs.zero_point = fend + 1;
-	old_size = target_cifsi->netfs.remote_i_size;
+
+	netfs_read_sizes(&target_cifsi->netfs, &old_size, &zero_point);
+	if (fend > zero_point)
+		netfs_write_zero_point(&target_cifsi->netfs, fend + 1);
 
 	/* Discard all the folios that overlap the destination region. */
 	cifs_dbg(FYI, "about to discard pages %llx-%llx\n", fstart, fend);
@@ -1439,8 +1441,8 @@ static loff_t cifs_remap_file_range(struct file *src_file, loff_t off,
 					rc = -EINVAL;
 			}
 		}
-		if (rc == 0 && new_size > target_cifsi->netfs.zero_point)
-			target_cifsi->netfs.zero_point = new_size;
+		if (rc == 0)
+			netfs_push_back_zero_point(&target_cifsi->netfs, new_size);
 	}
 
 	/* force revalidate of size and timestamps of target file now
@@ -1511,7 +1513,7 @@ ssize_t cifs_file_copychunk_range(unsigned int xid,
 	 * Advance the EOF marker after the flush above to the end of the range
 	 * if it's short of that.
 	 */
-	if (src_cifsi->netfs.remote_i_size < off + len) {
+	if (netfs_read_remote_i_size(&src_cifsi->netfs) < off + len) {
 		rc = cifs_precopy_set_eof(src_inode, src_cifsi, src_tcon, xid, off + len);
 		if (rc < 0)
 			goto unlock;
@@ -1539,8 +1541,8 @@ ssize_t cifs_file_copychunk_range(unsigned int xid,
 			fscache_resize_cookie(cifs_inode_cookie(target_inode),
 					      i_size_read(target_inode));
 		}
-		if (rc > 0 && destoff + rc > target_cifsi->netfs.zero_point)
-			target_cifsi->netfs.zero_point = destoff + rc;
+		if (rc > 0)
+			netfs_push_back_zero_point(&target_cifsi->netfs, destoff + rc);
 	}
 
 	file_accessed(src_file);
diff --git a/fs/smb/client/cifssmb.c b/fs/smb/client/cifssmb.c
index 3990a9012264..102dd9dde760 100644
--- a/fs/smb/client/cifssmb.c
+++ b/fs/smb/client/cifssmb.c
@@ -1538,7 +1538,7 @@ cifs_readv_callback(struct TCP_Server_Info *server, struct mid_q_entry *mid)
 	} else {
 		size_t trans = rdata->subreq.transferred + rdata->got_bytes;
 		if (trans < rdata->subreq.len &&
-		    rdata->subreq.start + trans >= ictx->remote_i_size) {
+		    rdata->subreq.start + trans >= netfs_read_remote_i_size(ictx)) {
 			rdata->result = 0;
 			__set_bit(NETFS_SREQ_HIT_EOF, &rdata->subreq.flags);
 		} else if (rdata->got_bytes > 0) {
diff --git a/fs/smb/client/file.c b/fs/smb/client/file.c
index 5d5b49468aff..ec1b1198642c 100644
--- a/fs/smb/client/file.c
+++ b/fs/smb/client/file.c
@@ -2502,16 +2502,19 @@ void cifs_write_subrequest_terminated(struct cifs_io_subrequest *wdata, ssize_t
 {
 	struct netfs_io_request *wreq = wdata->rreq;
 	struct netfs_inode *ictx = netfs_inode(wreq->inode);
+	unsigned long long remote_i_size, zero_point;
 	loff_t wrend;
 
 	if (result > 0) {
+		netfs_read_sizes(ictx, &remote_i_size, &zero_point);
+
 		wrend = wdata->subreq.start + wdata->subreq.transferred + result;
 
-		if (wrend > ictx->zero_point &&
+		if (wrend > zero_point &&
 		    (wdata->rreq->origin == NETFS_UNBUFFERED_WRITE ||
 		     wdata->rreq->origin == NETFS_DIO_WRITE))
-			ictx->zero_point = wrend;
-		if (wrend > ictx->remote_i_size)
+			netfs_write_zero_point(ictx, wrend);
+		if (wrend > remote_i_size)
 			netfs_resize_file(ictx, wrend, true);
 	}
 
diff --git a/fs/smb/client/inode.c b/fs/smb/client/inode.c
index 24040909d184..4189741d63fe 100644
--- a/fs/smb/client/inode.c
+++ b/fs/smb/client/inode.c
@@ -119,7 +119,7 @@ cifs_revalidate_cache(struct inode *inode, struct cifs_fattr *fattr)
 	fattr->cf_mtime = timestamp_truncate(fattr->cf_mtime, inode);
 	mtime = inode_get_mtime(inode);
 	if (timespec64_equal(&mtime, &fattr->cf_mtime) &&
-	    cifs_i->netfs.remote_i_size == fattr->cf_eof) {
+	    netfs_read_remote_i_size(&cifs_i->netfs) == fattr->cf_eof) {
 		cifs_dbg(FYI, "%s: inode %llu is unchanged\n",
 			 __func__, cifs_i->uniqueid);
 		return;
@@ -174,7 +174,7 @@ cifs_fattr_to_inode(struct inode *inode, struct cifs_fattr *fattr,
 		return -ESTALE;
 	}
 	if (inode_state_read_once(inode) & I_NEW)
-		CIFS_I(inode)->netfs.zero_point = fattr->cf_eof;
+		netfs_write_zero_point(&CIFS_I(inode)->netfs, fattr->cf_eof);
 
 	cifs_revalidate_cache(inode, fattr);
 
@@ -212,7 +212,7 @@ cifs_fattr_to_inode(struct inode *inode, struct cifs_fattr *fattr,
 	else
 		clear_bit(CIFS_INO_DELETE_PENDING, &cifs_i->flags);
 
-	cifs_i->netfs.remote_i_size = fattr->cf_eof;
+	netfs_write_remote_i_size(&cifs_i->netfs, fattr->cf_eof);
 	/*
 	 * Can't safely change the file size here if the client is writing to
 	 * it due to potential races.
@@ -2772,7 +2772,8 @@ cifs_revalidate_mapping(struct inode *inode)
 		if (cifs_sb_flags(cifs_sb) & CIFS_MOUNT_RW_CACHE)
 			goto skip_invalidate;
 
-		cifs_inode->netfs.zero_point = cifs_inode->netfs.remote_i_size;
+		netfs_write_zero_point(&cifs_inode->netfs,
+				       netfs_read_remote_i_size(&cifs_inode->netfs));
 		rc = filemap_invalidate_inode(inode, true, 0, LLONG_MAX);
 		if (rc) {
 			cifs_dbg(VFS, "%s: invalidate inode %p failed with rc %d\n",
diff --git a/fs/smb/client/readdir.c b/fs/smb/client/readdir.c
index be22bbc4a65a..d88682e89ec0 100644
--- a/fs/smb/client/readdir.c
+++ b/fs/smb/client/readdir.c
@@ -143,7 +143,8 @@ cifs_prime_dcache(struct dentry *parent, struct qstr *name,
 						fattr->cf_rdev = inode->i_rdev;
 						fattr->cf_uid = inode->i_uid;
 						fattr->cf_gid = inode->i_gid;
-						fattr->cf_eof = CIFS_I(inode)->netfs.remote_i_size;
+						fattr->cf_eof =
+							netfs_read_remote_i_size(&CIFS_I(inode)->netfs);
 						fattr->cf_symlink_target = NULL;
 					} else {
 						CIFS_I(inode)->time = 0;
diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index 509fcea28a42..5550d9c55ab2 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -3398,7 +3398,7 @@ static long smb3_zero_range(struct file *file, struct cifs_tcon *tcon,
 	filemap_invalidate_lock(inode->i_mapping);
 
 	i_size = i_size_read(inode);
-	remote_size = ictx->remote_i_size;
+	remote_size = netfs_read_remote_i_size(ictx);
 	if (offset + len >= remote_size && offset < i_size) {
 		unsigned long long top = umin(offset + len, i_size);
 
@@ -3433,8 +3433,8 @@ static long smb3_zero_range(struct file *file, struct cifs_tcon *tcon,
 		if (rc >= 0) {
 			truncate_setsize(inode, new_size);
 			netfs_resize_file(&cifsi->netfs, new_size, true);
-			if (offset < cifsi->netfs.zero_point)
-				cifsi->netfs.zero_point = offset;
+			if (offset < netfs_read_zero_point(&cifsi->netfs))
+				netfs_write_zero_point(&cifsi->netfs, offset);
 			fscache_resize_cookie(cifs_inode_cookie(inode), new_size);
 		}
 	}
@@ -3500,13 +3500,13 @@ static long smb3_punch_hole(struct file *file, struct cifs_tcon *tcon,
 	 * EOF update will end up in the wrong place.
 	 */
 	i_size = i_size_read(inode);
-	remote_i_size = netfs_inode(inode)->remote_i_size;
+	remote_i_size = netfs_read_remote_i_size(netfs_inode(inode));
 	if (end > remote_i_size && i_size > remote_i_size) {
 		unsigned long long extend_to = umin(end, i_size);
 		rc = SMB2_set_eof(xid, tcon, cfile->fid.persistent_fid,
 				  cfile->fid.volatile_fid, cfile->pid, extend_to);
 		if (rc >= 0)
-			netfs_inode(inode)->remote_i_size = extend_to;
+			netfs_write_remote_i_size(netfs_inode(inode), extend_to);
 	}
 
 unlock:
@@ -3788,7 +3788,7 @@ static long smb3_collapse_range(struct file *file, struct cifs_tcon *tcon,
 		goto out_2;
 
 	truncate_pagecache_range(inode, off, old_eof);
-	ictx->zero_point = old_eof;
+	netfs_write_zero_point(ictx, old_eof);
 	netfs_wait_for_outstanding_io(inode);
 
 	rc = smb2_copychunk_range(xid, cfile, cfile, off + len,
@@ -3806,7 +3806,7 @@ static long smb3_collapse_range(struct file *file, struct cifs_tcon *tcon,
 
 	truncate_setsize(inode, new_eof);
 	netfs_resize_file(&cifsi->netfs, new_eof, true);
-	ictx->zero_point = new_eof;
+	netfs_write_zero_point(ictx, new_eof);
 	fscache_resize_cookie(cifs_inode_cookie(inode), new_eof);
 out_2:
 	filemap_invalidate_unlock(inode->i_mapping);
@@ -3855,7 +3855,7 @@ static long smb3_insert_range(struct file *file, struct cifs_tcon *tcon,
 	rc = smb2_copychunk_range(xid, cfile, cfile, off, count, off + len);
 	if (rc < 0)
 		goto out_2;
-	cifsi->netfs.zero_point = new_eof;
+	netfs_write_zero_point(&cifsi->netfs, new_eof);
 
 	rc = smb3_zero_data(file, tcon, off, len, xid);
 	if (rc < 0)
diff --git a/fs/smb/client/smb2pdu.c b/fs/smb/client/smb2pdu.c
index 5188218c25be..8892fdd39474 100644
--- a/fs/smb/client/smb2pdu.c
+++ b/fs/smb/client/smb2pdu.c
@@ -4709,7 +4709,7 @@ smb2_readv_callback(struct TCP_Server_Info *server, struct mid_q_entry *mid)
 	} else {
 		size_t trans = rdata->subreq.transferred + rdata->got_bytes;
 		if (trans < rdata->subreq.len &&
-		    rdata->subreq.start + trans >= ictx->remote_i_size) {
+		    rdata->subreq.start + trans >= netfs_read_remote_i_size(ictx)) {
 			__set_bit(NETFS_SREQ_HIT_EOF, &rdata->subreq.flags);
 			rdata->result = 0;
 		}
diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index 62a528f90666..d72bc2f11734 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -62,8 +62,8 @@ struct netfs_inode {
 	struct fscache_cookie	*cache;
 #endif
 	struct mutex		wb_lock;	/* Writeback serialisation */
-	loff_t			remote_i_size;	/* Size of the remote file */
-	loff_t			zero_point;	/* Size after which we assume there's no data
+	loff_t			_remote_i_size;	/* Size of the remote file */
+	loff_t			_zero_point;	/* Size after which we assume there's no data
 						 * on the server */
 	atomic_t		io_count;	/* Number of outstanding reqs */
 	unsigned long		flags;
@@ -474,6 +474,260 @@ static inline struct netfs_inode *netfs_inode(struct inode *inode)
 	return container_of(inode, struct netfs_inode, inode);
 }
 
+/**
+ * netfs_read_remote_i_size - Read remote_i_size safely
+ * @ictx: The inode context to access
+ *
+ * Read remote_i_size safely without the potential for tearing on 32-bit
+ * arches.
+ *
+ * NOTE: in a 32bit arch with a preemptable kernel and an UP compile the
+ * i_size_read/write must be atomic with respect to the local cpu (unlike with
+ * preempt disabled), but they don't need to be atomic with respect to other
+ * cpus like in true SMP (so they need either to either locally disable irq
+ * around the read or for example on x86 they can be still implemented as a
+ * cmpxchg8b without the need of the lock prefix).  For SMP compiles and 64bit
+ * archs it makes no difference if preempt is enabled or not.
+ */
+static inline unsigned long long netfs_read_remote_i_size(const struct netfs_inode *ictx)
+{
+	unsigned long long remote_i_size;
+
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+	const struct inode *inode = &ictx->inode;
+	unsigned int seq;
+
+	do {
+		seq = read_seqcount_begin(&inode->i_size_seqcount);
+		remote_i_size = ictx->_remote_i_size;
+	} while (read_seqcount_retry(&inode->i_size_seqcount, seq));
+#elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPTION)
+	preempt_disable();
+	remote_i_size = ictx->_remote_i_size;
+	preempt_enable();
+#else
+	/* Pairs with smp_store_release() in netfs_write_remote_i_size() */
+	remote_i_size = smp_load_acquire(&ictx->_remote_i_size);
+#endif
+	return remote_i_size;
+}
+
+/*
+ * netfs_write_remote_i_size - Set remote_i_size safely
+ * @ictx: The inode context to access
+ * @remote_i_size: The new value for the size of the file on the server
+ *
+ * Set remote_i_size safely without the potential for tearing on 32-bit arches.
+ *
+ * NOTE: unlike netfs_read_remote_i_size(), netfs_write_remote_i_size() does
+ * need locking around it (normally i_rwsem), otherwise on 32bit/SMP an update
+ * of i_size_seqcount can be lost, resulting in subsequent i_size_read() calls
+ * spinning forever.
+ */
+static inline void netfs_write_remote_i_size(struct netfs_inode *ictx,
+					     unsigned long long remote_i_size)
+{
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+	struct inode *inode = &ictx->inode;
+
+	preempt_disable();
+	write_seqcount_begin(&inode->i_size_seqcount);
+	ictx->_remote_i_size = remote_i_size;
+	write_seqcount_end(&inode->i_size_seqcount);
+	preempt_enable();
+#elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPTION)
+	preempt_disable();
+	ictx->_remote_i_size = remote_i_size;
+	preempt_enable();
+#else
+	/*
+	 * Pairs with smp_load_acquire() in netfs_read_remote_i_size() to
+	 * ensure changes related to inode size (such as page contents) are
+	 * visible before we see the changed inode size.
+	 */
+	smp_store_release(&ictx->_remote_i_size, remote_i_size);
+#endif
+}
+
+/**
+ * netfs_read_zero_point - Read zero_point safely
+ * @ictx: The inode context to access
+ *
+ * Read zero_point safely without the potential for tearing on 32-bit
+ * arches.
+ *
+ * NOTE: in a 32bit arch with a preemptable kernel and an UP compile the
+ * i_size_read/write must be atomic with respect to the local cpu (unlike with
+ * preempt disabled), but they don't need to be atomic with respect to other
+ * cpus like in true SMP (so they need either to either locally disable irq
+ * around the read or for example on x86 they can be still implemented as a
+ * cmpxchg8b without the need of the lock prefix).  For SMP compiles and 64bit
+ * archs it makes no difference if preempt is enabled or not.
+ */
+static inline unsigned long long netfs_read_zero_point(const struct netfs_inode *ictx)
+{
+	unsigned long long zero_point;
+
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+	const struct inode *inode = &ictx->inode;
+	unsigned int seq;
+
+	do {
+		seq = read_seqcount_begin(&inode->i_size_seqcount);
+		zero_point = ictx->_zero_point;
+	} while (read_seqcount_retry(&inode->i_size_seqcount, seq));
+#elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPTION)
+	preempt_disable();
+	zero_point = ictx->_zero_point;
+	preempt_enable();
+#else
+	/* Pairs with smp_store_release() in netfs_write_zero_point() */
+	zero_point = smp_load_acquire(&ictx->_zero_point);
+#endif
+	return zero_point;
+}
+
+/*
+ * netfs_write_zero_point - Set zero_point safely
+ * @ictx: The inode context to access
+ * @zero_point: The new value for the point beyond which the server has no data
+ *
+ * Set zero_point safely without the potential for tearing on 32-bit arches.
+ *
+ * NOTE: unlike netfs_read_zero_point(), netfs_write_zero_point() does need
+ * locking around it (normally i_rwsem), otherwise on 32bit/SMP an update of
+ * i_size_seqcount can be lost, resulting in subsequent read calls spinning
+ * forever.
+ */
+static inline void netfs_write_zero_point(struct netfs_inode *ictx,
+					  unsigned long long zero_point)
+{
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+	struct inode *inode = &ictx->inode;
+
+	preempt_disable();
+	write_seqcount_begin(&inode->i_size_seqcount);
+	ictx->_zero_point = zero_point;
+	write_seqcount_end(&inode->i_size_seqcount);
+	preempt_enable();
+#elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPTION)
+	preempt_disable();
+	ictx->_zero_point = zero_point;
+	preempt_enable();
+#else
+	/*
+	 * Pairs with smp_load_acquire() in netfs_read_zero_point() to
+	 * ensure changes related to inode size (such as page contents) are
+	 * visible before we see the changed inode size.
+	 */
+	smp_store_release(&ictx->_zero_point, zero_point);
+#endif
+}
+
+/**
+ * netfs_push_back_zero_point - Push back the zero point if unknown data now beyond it
+ * ictx: The inode context to access
+ * to: The end of a new region of unknown data
+ *
+ * Move back the zero_point if we cause a region of unknown data to appear
+ * beyond it (such as doing a copy_file_range).
+ */
+static inline void netfs_push_back_zero_point(struct netfs_inode *ictx,
+					      unsigned long long to)
+{
+	if (to > netfs_read_zero_point(ictx))
+		netfs_write_zero_point(ictx, to);
+}
+
+/**
+ * netfs_read_sizes - Read remote_i_size and zero_point safely
+ * @ictx: The inode context to access
+ * @remote_i_size: Where to return the size of the file on the server
+ * @zero_point: Where to return the the point beyond which the server has no data
+ *
+ * Read remote_i_size and zero_point safely without the potential for tearing
+ * on 32-bit arches.
+ *
+ * NOTE: in a 32bit arch with a preemptable kernel and an UP compile the
+ * i_size_read/write must be atomic with respect to the local cpu (unlike with
+ * preempt disabled), but they don't need to be atomic with respect to other
+ * cpus like in true SMP (so they need either to either locally disable irq
+ * around the read or for example on x86 they can be still implemented as a
+ * cmpxchg8b without the need of the lock prefix).  For SMP compiles and 64bit
+ * archs it makes no difference if preempt is enabled or not.
+ */
+static inline void netfs_read_sizes(const struct netfs_inode *ictx,
+				    unsigned long long *remote_i_size,
+				    unsigned long long *zero_point)
+{
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+	const struct inode *inode = &ictx->inode;
+	unsigned int seq;
+
+	do {
+		seq = read_seqcount_begin(&inode->i_size_seqcount);
+		*remote_i_size = ictx->_remote_i_size;
+		*zero_point = ictx->_zero_point;
+	} while (read_seqcount_retry(&inode->i_size_seqcount, seq));
+	return zero_point;
+#elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPTION)
+	unsigned long long zero_point;
+
+	preempt_disable();
+	*remote_i_size = ictx->_remote_i_size;
+	*zero_point = ictx->_zero_point;
+	preempt_enable();
+#else
+	/* Pairs with smp_store_release() in netfs_write_zero_point() */
+	*remote_i_size = smp_load_acquire(&ictx->_remote_i_size);
+	*zero_point = smp_load_acquire(&ictx->_zero_point);
+#endif
+}
+
+/*
+ * netfs_write_sizes - Set remote_i_size and zero_point safely
+ * @ictx: The inode context to access
+ * @remote_i_size: The new value for the size of the file on the server
+ * @zero_point: The new value for the point beyond which the server has no data
+ *
+ * Set both remote_i_size and zero_point safely without the potential for
+ * tearing on 32-bit arches.
+ *
+ * NOTE: unlike netfs_read_zero_point(), netfs_write_zero_point() does need
+ * locking around it (normally i_rwsem), otherwise on 32bit/SMP an update of
+ * i_size_seqcount can be lost, resulting in subsequent read calls spinning
+ * forever.
+ */
+static inline void netfs_write_sizes(struct netfs_inode *ictx,
+				     unsigned long long remote_i_size,
+				     unsigned long long zero_point)
+{
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+	struct inode *inode = &ictx->inode;
+
+	preempt_disable();
+	write_seqcount_begin(&inode->i_size_seqcount);
+	ictx->_remote_i_size = remote_i_size;
+	ictx->_zero_point = zero_point;
+	write_seqcount_end(&inode->i_size_seqcount);
+	preempt_enable();
+#elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPTION)
+	preempt_disable();
+	ictx->_remote_i_size = remote_i_size;
+	ictx->_zero_point = zero_point;
+	preempt_enable();
+#else
+	/*
+	 * Pairs with smp_load_acquire() in netfs_read_remote_i_size and
+	 * netfs_read_zero_point() to ensure changes related to inode size
+	 * (such as page contents) are visible before we see the changed inode
+	 * size.
+	 */
+	smp_store_release(&ictx->_remote_i_size, remote_i_size);
+	smp_store_release(&ictx->_zero_point, zero_point);
+#endif
+}
+
 /**
  * netfs_inode_init - Initialise a netfslib inode context
  * @ctx: The netfs inode to initialise
@@ -488,8 +742,8 @@ static inline void netfs_inode_init(struct netfs_inode *ctx,
 				    bool use_zero_point)
 {
 	ctx->ops = ops;
-	ctx->remote_i_size = i_size_read(&ctx->inode);
-	ctx->zero_point = LLONG_MAX;
+	ctx->_remote_i_size = i_size_read(&ctx->inode);
+	ctx->_zero_point = LLONG_MAX;
 	ctx->flags = 0;
 	atomic_set(&ctx->io_count, 0);
 #if IS_ENABLED(CONFIG_FSCACHE)
@@ -498,7 +752,7 @@ static inline void netfs_inode_init(struct netfs_inode *ctx,
 	mutex_init(&ctx->wb_lock);
 	/* ->releasepage() drives zero_point */
 	if (use_zero_point) {
-		ctx->zero_point = ctx->remote_i_size;
+		ctx->_zero_point = ctx->_remote_i_size;
 		mapping_set_release_always(ctx->inode.i_mapping);
 	}
 }
@@ -511,13 +765,40 @@ static inline void netfs_inode_init(struct netfs_inode *ctx,
  *
  * Inform the netfs lib that a file got resized so that it can adjust its state.
  */
-static inline void netfs_resize_file(struct netfs_inode *ctx, loff_t new_i_size,
+static inline void netfs_resize_file(struct netfs_inode *ictx,
+				     unsigned long long new_i_size,
 				     bool changed_on_server)
 {
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+	struct inode *inode = &ictx->inode;
+
+	preempt_disable();
+	write_seqcount_begin(&inode->i_size_seqcount);
+	if (changed_on_server)
+		ictx->_remote_i_size = new_i_size;
+	if (new_i_size < ictx->_zero_point)
+		ictx->_zero_point = new_i_size;
+	write_seqcount_end(&inode->i_size_seqcount);
+	preempt_enable();
+#elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPTION)
+	preempt_disable();
 	if (changed_on_server)
-		ctx->remote_i_size = new_i_size;
-	if (new_i_size < ctx->zero_point)
-		ctx->zero_point = new_i_size;
+		ictx->_remote_i_size = new_i_size;
+	if (new_i_size < ictx->_zero_point)
+		ictx->_zero_point = new_i_size;
+	preempt_enable();
+#else
+	/*
+	 * Pairs with smp_load_acquire() in netfs_read_remote_i_size and
+	 * netfs_read_zero_point() to ensure changes related to inode size
+	 * (such as page contents) are visible before we see the changed inode
+	 * size.
+	 */
+	if (changed_on_server)
+		smp_store_release(&ictx->_remote_i_size, new_i_size);
+	if (new_i_size < ictx->_zero_point)
+		smp_store_release(&ictx->_zero_point, new_i_size);
+#endif
 }
 
 /**

[PATCH 10/11] netfs: Fix comment about write-streaming avoidance

[David Howells]

In netfs_perform_write(), there used to be a section in which
write-streaming was avoided if either the fd is open O_RDWR or fscaching is
enabled, but the former was removed as netfs_read_folio() can now fill in
the gaps rather then flushing, but the comment was not updated.

Fix the comment to match.

Fixes: eac38f8a2b85 ("netfs: Fix write streaming disablement if fd open O_RDWR")
Closes: https://sashiko.dev/#/patchset/20260414082004.3756080-1-dhowells%40redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Paulo Alcantara <pc@manguebit.org>
cc: Matthew Wilcox <willy@infradead.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
---
 fs/netfs/buffered_write.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/fs/netfs/buffered_write.c b/fs/netfs/buffered_write.c
index c840f5448178..2abf451c38f6 100644
--- a/fs/netfs/buffered_write.c
+++ b/fs/netfs/buffered_write.c
@@ -278,9 +278,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 
 		/* We don't want to do a streaming write on a file that loses
 		 * caching service temporarily because the backing store got
-		 * culled and we don't really want to get a streaming write on
-		 * a file that's open for reading as ->read_folio() then has to
-		 * be able to flush it.
+		 * culled.
 		 */
 		if (netfs_is_cache_enabled(ctx)) {
 			if (finfo) {

[PATCH 11/11] netfs: Fix netfs_read_folio() to wait on writeback

[David Howells]

Fix netfs_read_folio() to wait for an ongoing writeback to complete so that
it can trust the dirty flag and whatever is attached to folio->private
(folio->private may get cleaned up by the collector before it clears the
writeback flag).

Fixes: ee4cdf7ba857 ("netfs: Speed up buffered reading")
Closes: https://sashiko.dev/#/patchset/20260414082004.3756080-1-dhowells%40redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Paulo Alcantara <pc@manguebit.org>
cc: Matthew Wilcox <willy@infradead.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
---
 fs/netfs/buffered_read.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c
index 4d6dfcffba78..dcfe51eec266 100644
--- a/fs/netfs/buffered_read.c
+++ b/fs/netfs/buffered_read.c
@@ -506,6 +506,8 @@ int netfs_read_folio(struct file *file, struct folio *folio)
 	struct netfs_inode *ctx = netfs_inode(mapping->host);
 	int ret;
 
+	folio_wait_writeback(folio);
+
 	if (folio_test_dirty(folio))
 		return netfs_read_gaps(file, folio);