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[185.203.47.240]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48a7b8c2dd7sm37481365e9.0.2026.04.29.03.49.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 Apr 2026 03:49:57 -0700 (PDT) From: Igor Raits To: Trond Myklebust , Anna Schumaker Cc: NeilBrown , =?UTF-8?q?Jan=20=C4=8C=C3=ADpa?= , linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH] NFSv4: clear exception state on successful mkdir retry Date: Wed, 29 Apr 2026 12:49:38 +0200 Message-ID: <20260429104938.1776671-1-igor.raits@gmail.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <177745671692.1474915.5018486129724109553@noble.neil.brown.name> References: <177745671692.1474915.5018486129724109553@noble.neil.brown.name> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Closes: https://lore.kernel.org/linux-nfs/CA+9S74hSp_tJu2Ffe2BPNC2T25gfkhgjjDkdgSsF5c2rnJq_wA@mail.gmail.com/ Reviewed-by: NeilBrown Cc: stable@vger.kernel.org Signed-off-by: Igor Raits --- 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); -- 2.53.0