linux-stable.git/fs/nfs/write.c, branch linux-rolling-lts

NFS: Charge unstable writes by request size, not folio size

2026-07-24T14:17:06+00:00

commit 27934d02cbeb8a957dd11c985a579e58d30c5270 upstream.

nfs_folio_mark_unstable() and nfs_folio_clear_commit() charge and
uncharge NR_WRITEBACK/WB_WRITEBACK by folio_nr_pages(folio) once per
*request* added to or removed from a commit list. This is correct only
when a folio has a single associated request. When pg_test splits a
folio into N sub-folio requests (e.g. pNFS flexfiles striping with a
stripe unit smaller than the folio size, or plain wsize-limited
splitting), each of the N requests independently charges the whole
folio's page count, inflating the accounting by a factor of N per
folio. With large folios and small stripe units this reaches multiple
orders of magnitude: a 2 MiB folio split into 512 4 KiB requests can
charge up to 512x its real size, pushing global dirty+writeback
accounting past the system's dirty threshold and forcing every
buffered writer on the host into the hard-throttle path, including
unrelated in-kernel NFS server threads sharing the box.

Charge each request only for the pages it actually covers.

Fixes: 0c493b5cf16e ("NFS: Convert buffered writes to use folios")
Cc: stable@vger.kernel.org
Signed-off-by: Benjamin Coddington 
Assisted-By: Claude Sonnet 5 
Signed-off-by: Anna Schumaker 
Signed-off-by: Greg Kroah-Hartman

NFS: Fix a deadlock involving nfs_release_folio()

2026-01-23T10:21:13+00:00

[ Upstream commit cce0be6eb4971456b703aaeafd571650d314bcca ]

Wang Zhaolong reports a deadlock involving NFSv4.1 state recovery
waiting on kthreadd, which is attempting to reclaim memory by calling
nfs_release_folio(). The latter cannot make progress due to state
recovery being needed.

It seems that the only safe thing to do here is to kick off a writeback
of the folio, without waiting for completion, or else kicking off an
asynchronous commit.

Reported-by: Wang Zhaolong 
Fixes: 96780ca55e3c ("NFS: fix up nfs_release_folio() to try to release the page")
Signed-off-by: Trond Myklebust 
Signed-off-by: Sasha Levin

NFS: check if suid/sgid was cleared after a write as needed

2025-10-13T18:33:00+00:00

I noticed xfstests generic/193 and generic/355 started failing against
knfsd after commit e7a8ebc305f2 ("NFSD: Offer write delegation for OPEN
with OPEN4_SHARE_ACCESS_WRITE").

I ran those same tests against ONTAP (which has had write delegation
support for a lot longer than knfsd) and they fail there too... so
while it's a new failure against knfsd, it isn't an entirely new
failure.

Add the NFS_INO_REVAL_FORCED flag so that the presence of a delegation
doesn't keep the inode from being revalidated to fetch the updated mode.

Signed-off-by: Scott Mayhew 
Signed-off-by: Anna Schumaker

NFSv4/flexfiles: Use ds_commit_idx when marking a write commit

2025-09-26T19:30:20+00:00

Correct this path to use ds_commit_idx. Another noop preparation
change. In current code commit_idx == mirror_idx but when striping is
enabled that will not be true.

Signed-off-by: Jonathan Curley 
Signed-off-by: Anna Schumaker

NFS: Enable use of the RWF_DONTCACHE flag on the NFS client

2025-09-23T17:29:50+00:00

The NFS client needs to defer dropbehind until after any writes to the
folio have been persisted on the server. Since this may be a 2 step
process, use folio_end_writeback_no_dropbehind() to allow release of the
writeback flag, and then call folio_end_dropbehind() once the COMMIT is
done.

Signed-off-by: Trond Myklebust 
Signed-off-by: Anna Schumaker

sunrpc: remove dfprintk_cont() and dfprintk_rcu_cont()

2025-09-23T17:28:19+00:00

KERN_CONT hails from a simpler time, when SMP wasn't the norm. These
days, it doesn't quite work right since another printk() can always race
in between the first one and the one being "continued".

Nothing calls dprintk_rcu_cont(), so just remove it. The only caller of
dprintk_cont() is in nfs_commit_release_pages(). Just use a normal
dprintk() there instead, since this is not SMP-safe anyway.

Signed-off-by: Jeff Layton 
Reviewed-by: Chuck Lever 
Reviewed-by: Simon Horman 
Signed-off-by: Anna Schumaker

nfs: add tracepoints to nfs_writepages()

2025-09-23T17:28:19+00:00

Show the inode info and requested range.

Signed-off-by: Jeff Layton 
Reviewed-by: Benjamin Coddington 
Signed-off-by: Anna Schumaker

nfs: more in-depth tracing of writepage events

2025-09-23T17:28:19+00:00

Add tracepoints to nfs_writepage_setup() and nfs_do_writepage().

Signed-off-by: Jeff Layton 
Reviewed-by: Benjamin Coddington 
Signed-off-by: Anna Schumaker

nfs: new tracepoints around write handling

2025-09-23T17:28:19+00:00

New start and done tracepoints for:

nfs_update_folio()
nfs_write_begin()
nfs_write_end()
nfs_try_to_update_request()

Signed-off-by: Jeff Layton 
Reviewed-by: Benjamin Coddington 
Signed-off-by: Anna Schumaker

NFS: Fix the marking of the folio as up to date

2025-09-06T20:51:26+00:00

Since all callers of nfs_page_group_covers_page() have already ensured
that there is only one group member, all that is required is to check
that the entire folio contains dirty data.

Signed-off-by: Trond Myklebust