FAILED: patch "[PATCH] nfsd: reset write verifier on deferred writeback errors" failed to apply to 6.6-stable tree

FAILED: patch "[PATCH] nfsd: reset write verifier on deferred writeback errors" failed to apply to 6.6-stable tree

[gregkh]

The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 2090b05803faab8a9fa62fbff871007862cac1b7
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026070203-tipping-straw-267a@gregkh' --subject-prefix 'PATCH 6.6.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2090b05803faab8a9fa62fbff871007862cac1b7 Mon Sep 17 00:00:00 2001
From: Jeff Layton <jlayton@kernel.org>
Date: Fri, 22 May 2026 12:44:19 -0400
Subject: [PATCH] nfsd: reset write verifier on deferred writeback errors
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

nfsd_vfs_write() and nfsd_commit() both call filemap_check_wb_err() to
detect deferred writeback errors, but neither rotates the server's write
verifier (nn->writeverf) when this check fails. Every other
durable-storage-failure path in these functions calls
commit_reset_write_verifier() before returning an error.

The missing rotation means clients holding UNSTABLE write data under the
current verifier will COMMIT, receive the unchanged verifier back, and
conclude their data is durable — silently dropping data that failed
writeback. This violates the UNSTABLE+COMMIT durability contract
(RFC 1813 §3.3.7, RFC 8881 §18.32).

Add commit_reset_write_verifier() calls at both filemap_check_wb_err()
error sites, matching the pattern used by adjacent error paths in the
same functions. The helper already filters -EAGAIN and -ESTALE
internally, so the calls are unconditionally safe.

Reported-by: Chris Mason <clm@meta.com>
Fixes: 555dbf1a9aac ("nfsd: Replace use of rwsem with errseq_t")
Cc: stable@vger.kernel.org
Assisted-by: kres:claude-opus-4-6
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index cba473969429..7e6468bdc723 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1513,8 +1513,10 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	nfsd_stats_io_write_add(nn, exp, *cnt);
 	fsnotify_modify(file);
 	host_err = filemap_check_wb_err(file->f_mapping, since);
-	if (host_err < 0)
+	if (host_err < 0) {
+		commit_reset_write_verifier(nn, rqstp, host_err);
 		goto out_nfserr;
+	}
 
 	if (stable && fhp->fh_use_wgather) {
 		host_err = wait_for_concurrent_writes(file);
@@ -1694,6 +1696,8 @@ nfsd_commit(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfsd_file *nf,
 			nfsd_copy_write_verifier(verf, nn);
 			err2 = filemap_check_wb_err(nf->nf_file->f_mapping,
 						    since);
+			if (err2 < 0)
+				commit_reset_write_verifier(nn, rqstp, err2);
 			err = nfserrno(err2);
 			break;
 		case -EINVAL:

[PATCH 6.6.y 1/2] nfsd: Don't reset the write verifier on a commit EAGAIN

[Sasha Levin]

From: Trond Myklebust <trond.myklebust@hammerspace.com>

[ Upstream commit 1b2021bdeeca12364ad0fa7aac9ddba5cae964f3 ]

If fsync() is returning EAGAIN, then we can assume that the filesystem
being exported is something like NFS with the 'softerr' mount option
enabled, and that it is just asking us to replay the fsync() operation
at a later date.

If we see an ESTALE, then ditto: the file is gone, so there is no danger
of losing the error.

For those cases, do not reset the write verifier. A write verifier
change has a global effect, causing retransmission by all clients of
all uncommitted unstable writes for all files, so it is worth
mitigating where possible.

Link: https://lore.kernel.org/linux-nfs/20230911184357.11739-1-trond.myklebust@hammerspace.com/
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Stable-dep-of: 2090b05803fa ("nfsd: reset write verifier on deferred writeback errors")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/nfsd/vfs.c | 33 +++++++++++++++++++++++----------
 1 file changed, 23 insertions(+), 10 deletions(-)

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index ae1f43eb515a81..f83b312fe3b4d4 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -338,6 +338,24 @@ nfsd_lookup(struct svc_rqst *rqstp, struct svc_fh *fhp, const char *name,
 	return err;
 }
 
+static void
+commit_reset_write_verifier(struct nfsd_net *nn, struct svc_rqst *rqstp,
+			    int err)
+{
+	switch (err) {
+	case -EAGAIN:
+	case -ESTALE:
+		/*
+		 * Neither of these are the result of a problem with
+		 * durable storage, so avoid a write verifier reset.
+		 */
+		break;
+	default:
+		nfsd_reset_write_verifier(nn);
+		trace_nfsd_writeverf_reset(nn, rqstp, err);
+	}
+}
+
 /*
  * Commit metadata changes to stable storage.
  */
@@ -659,8 +677,7 @@ __be32 nfsd4_clone_file_range(struct svc_rqst *rqstp,
 					&nfsd4_get_cstate(rqstp)->current_fh,
 					dst_pos,
 					count, status);
-			nfsd_reset_write_verifier(nn);
-			trace_nfsd_writeverf_reset(nn, rqstp, status);
+			commit_reset_write_verifier(nn, rqstp, status);
 			ret = nfserrno(status);
 		}
 	}
@@ -1177,8 +1194,7 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfsd_file *nf,
 	host_err = vfs_iter_write(file, &iter, &pos, flags);
 	file_end_write(file);
 	if (host_err < 0) {
-		nfsd_reset_write_verifier(nn);
-		trace_nfsd_writeverf_reset(nn, rqstp, host_err);
+		commit_reset_write_verifier(nn, rqstp, host_err);
 		goto out_nfserr;
 	}
 	*cnt = host_err;
@@ -1190,10 +1206,8 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfsd_file *nf,
 
 	if (stable && use_wgather) {
 		host_err = wait_for_concurrent_writes(file);
-		if (host_err < 0) {
-			nfsd_reset_write_verifier(nn);
-			trace_nfsd_writeverf_reset(nn, rqstp, host_err);
-		}
+		if (host_err < 0)
+			commit_reset_write_verifier(nn, rqstp, host_err);
 	}
 
 out_nfserr:
@@ -1336,8 +1350,7 @@ nfsd_commit(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfsd_file *nf,
 			err = nfserr_notsupp;
 			break;
 		default:
-			nfsd_reset_write_verifier(nn);
-			trace_nfsd_writeverf_reset(nn, rqstp, err2);
+			commit_reset_write_verifier(nn, rqstp, err2);
 			err = nfserrno(err2);
 		}
 	} else
-- 
2.53.0

[PATCH 6.6.y 2/2] nfsd: reset write verifier on deferred writeback errors

[Sasha Levin]

From: Jeff Layton <jlayton@kernel.org>

[ Upstream commit 2090b05803faab8a9fa62fbff871007862cac1b7 ]

nfsd_vfs_write() and nfsd_commit() both call filemap_check_wb_err() to
detect deferred writeback errors, but neither rotates the server's write
verifier (nn->writeverf) when this check fails. Every other
durable-storage-failure path in these functions calls
commit_reset_write_verifier() before returning an error.

The missing rotation means clients holding UNSTABLE write data under the
current verifier will COMMIT, receive the unchanged verifier back, and
conclude their data is durable — silently dropping data that failed
writeback. This violates the UNSTABLE+COMMIT durability contract
(RFC 1813 §3.3.7, RFC 8881 §18.32).

Add commit_reset_write_verifier() calls at both filemap_check_wb_err()
error sites, matching the pattern used by adjacent error paths in the
same functions. The helper already filters -EAGAIN and -ESTALE
internally, so the calls are unconditionally safe.

Reported-by: Chris Mason <clm@meta.com>
Fixes: 555dbf1a9aac ("nfsd: Replace use of rwsem with errseq_t")
Cc: stable@vger.kernel.org
Assisted-by: kres:claude-opus-4-6
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/nfsd/vfs.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index f83b312fe3b4d4..a37137d722c9e7 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1201,8 +1201,10 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfsd_file *nf,
 	nfsd_stats_io_write_add(nn, exp, *cnt);
 	fsnotify_modify(file);
 	host_err = filemap_check_wb_err(file->f_mapping, since);
-	if (host_err < 0)
+	if (host_err < 0) {
+		commit_reset_write_verifier(nn, rqstp, host_err);
 		goto out_nfserr;
+	}
 
 	if (stable && use_wgather) {
 		host_err = wait_for_concurrent_writes(file);
@@ -1344,6 +1346,8 @@ nfsd_commit(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfsd_file *nf,
 			nfsd_copy_write_verifier(verf, nn);
 			err2 = filemap_check_wb_err(nf->nf_file->f_mapping,
 						    since);
+			if (err2 < 0)
+				commit_reset_write_verifier(nn, rqstp, err2);
 			err = nfserrno(err2);
 			break;
 		case -EINVAL:
-- 
2.53.0