From: Thorsten Leemhuis <regressions@leemhuis.info>
To: Trond Myklebust <trondmy@kernel.org>, Anna Schumaker <anna@kernel.org>
Cc: NeilBrown <neil@brown.name>, "Jan Čípa" <jan.cipa@gooddata.com>,
linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org, "Igor Raits" <igor.raits@gmail.com>,
"Linux kernel regressions list" <regressions@lists.linux.dev>
Subject: Re: [PATCH] NFSv4: clear exception state on successful mkdir retry
Date: Wed, 13 May 2026 09:18:45 +0200 [thread overview]
Message-ID: <971ecb6c-2687-429f-af86-fc980c2d04f9@leemhuis.info> (raw)
In-Reply-To: <20260429104938.1776671-1-igor.raits@gmail.com>
[top-posting to facilitate processing]
@NFSv4 maintainers, just wondering, did this patch maybe fall through
the cracks? It fixes a regression, that's why it's on my radar. Or was
there some progress and I missed it?
Ciao, Thorsten
On 4/29/26 12:49, Igor Raits wrote:
> After a server returns NFS4ERR_DELAY for an NFSv4 CREATE issued by
> mkdir(2), the client correctly waits and retries. When the retry
> succeeds, however, mkdir(2) can still surface -EEXIST to userspace
> even though the directory was just created on the server.
>
> Reproducer (random 16-hex names so collisions are not the cause)
> against an in-kernel Linux nfsd; reproduces under both NFSv4.0 and
> NFSv4.2:
>
> N=2000000; base=/var/gdc/export
> for ((i=1; i<=N; i++)); do
> d=$base/$(openssl rand -hex 8)
> mkdir "$d" 2>/dev/null || echo "$(date +%T) failed loop=$i $d"
> rmdir "$d" 2>/dev/null
> done
>
> Failures cluster at the cadence at which the server-side auth/export
> cache refresh path causes nfsd to return NFS4ERR_DELAY for CREATE.
>
> A wire trace of one failure (the three CREATE RPCs all come from a
> single mkdir(2), generated by the do-while in nfs4_proc_mkdir()):
>
> client -> server CREATE name=... -> NFS4ERR_DELAY
> ~100 ms later
> client -> server CREATE name=... -> NFS4_OK (dir created)
> ~80 us later
> client -> server CREATE name=... -> NFS4ERR_EXIST (correct)
>
> Since commit dd862da61e91 ("nfs: fix incorrect handling of large-number
> NFS errors in nfs4_do_mkdir()"), nfs4_handle_exception() is called only
> when _nfs4_proc_mkdir() returned an error. That gate breaks retry-state
> hygiene: nfs4_do_handle_exception() resets exception.{delay,recovering,
> retry} to 0 on entry, so calling it on success is what previously
> cleared the retry flag set by the preceding NFS4ERR_DELAY iteration.
> With the gate in place, exception.retry stays at 1 after the successful
> retry, the loop runs once more, and the resulting CREATE for an
> already-created name yields NFS4ERR_EXIST -> -EEXIST to userspace.
>
> Drop the conditional and call nfs4_handle_exception() unconditionally,
> matching every other do-while in fs/nfs/nfs4proc.c (nfs4_proc_symlink(),
> nfs4_proc_link(), etc.). The dentry/status separation introduced by
> that commit is preserved.
>
> Fixes: dd862da61e91 ("nfs: fix incorrect handling of large-number NFS errors in nfs4_do_mkdir()")
> Reported-and-tested-by: Jan Čípa <jan.cipa@gooddata.com>
> Closes: https://lore.kernel.org/linux-nfs/CA+9S74hSp_tJu2Ffe2BPNC2T25gfkhgjjDkdgSsF5c2rnJq_wA@mail.gmail.com/
> Reviewed-by: NeilBrown <neil@brown.name>
> Cc: stable@vger.kernel.org
> Signed-off-by: Igor Raits <igor.raits@gmail.com>
> ---
> fs/nfs/nfs4proc.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index a0885ae55abc..ffd14141ea1d 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -5393,10 +5393,9 @@ static struct dentry *nfs4_proc_mkdir(struct inode *dir, struct dentry *dentry,
> do {
> alias = _nfs4_proc_mkdir(dir, dentry, sattr, label, &err);
> trace_nfs4_mkdir(dir, &dentry->d_name, err);
> + err = nfs4_handle_exception(NFS_SERVER(dir), err, &exception);
> if (err)
> - alias = ERR_PTR(nfs4_handle_exception(NFS_SERVER(dir),
> - err,
> - &exception));
> + alias = ERR_PTR(err);
> } while (exception.retry);
> nfs4_label_release_security(label);
>
prev parent reply other threads:[~2026-05-13 7:19 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-29 5:02 REGRESSION: NFSv4: mkdir returns EEXIST after NFS4ERR_DELAY-then-success; Igor Raits
2026-04-29 7:12 ` Igor Raits
2026-04-29 9:58 ` NeilBrown
2026-04-29 10:49 ` [PATCH] NFSv4: clear exception state on successful mkdir retry Igor Raits
2026-05-13 7:18 ` Thorsten Leemhuis [this message]
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