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Tue, 10 Nov 2026 00:00:45 -0800 (PST) Received: from osman.mioffice.cn ([43.224.245.178]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-1b3b5b11346sm6139313c88.7.2026.11.10.00.00.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Nov 2026 00:00:44 -0800 (PST) From: Zhan Xusheng To: cel@kernel.org, jlayton@kernel.org Cc: neil@brown.name, okorniev@redhat.com, Dai.Ngo@oracle.com, tom@talpey.com, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, zhanxusheng@xiaomi.com Subject: [PATCH] nfsd: don't block on a file lease while holding the parent lock Date: Tue, 10 Nov 2026 16:00:38 +0800 Message-ID: <20261110080038.232210-1-zhanxusheng1024@gmail.com> X-Mailer: git-send-email 2.43.0 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Zhan Xusheng Since commit 2a60db3525d4 ("nfsd: (almost) always open file in nfsd4_create_file()"), an NFSv4 OPEN with create that finds an existing file opens it with dentry_open() while start_creating() still holds the parent directory lock. The open flags lack O_NONBLOCK, so break_lease() in do_dentry_open() blocks. Before that commit the file was opened later by __nfsd_open(), which breaks leases with O_NONBLOCK, and the client retried on NFS4ERR_DELAY. A lease on the file now stalls an nfsd thread for up to lease-break-time with the directory locked, and other creates, unlinks and renames in that directory wait for it. To reproduce, set fs.lease-break-time=15, take F_SETLEASE F_WRLCK on /srv/g from a local process and keep it, and run "echo x >> /mnt/g" on an NFSv4.2 mount of /srv from localhost. The nfsd thread blocks in break_lease() for 15s, and "touch /srv/other" on the server takes 13s. Pass O_NONBLOCK so that break_lease() returns -EWOULDBLOCK and the client gets NFS4ERR_DELAY again. Fixes: 2a60db3525d4 ("nfsd: (almost) always open file in nfsd4_create_file()") Signed-off-by: Zhan Xusheng --- With this patch the same test hits break_lease_noblock and the touch takes 20-30ms (QEMU guest, f66469d9905b). NeilBrown's "nfsd: switch NFS4 OPEN to use vfs_lookup_open()" (v2 12/14) makes the same change; that series is not merged. fs/nfsd/nfs4proc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c index 3a82af381a8d..e95258b44c72 100644 --- a/fs/nfsd/nfs4proc.c +++ b/fs/nfsd/nfs4proc.c @@ -312,7 +312,7 @@ nfsd4_create_file(struct svc_rqst *rqstp, struct svc_fh *fhp, .na_iattr = iap, .na_seclabel = &open->op_label, }; - int oflags = O_CREAT | O_LARGEFILE; + int oflags = O_CREAT | O_LARGEFILE | O_NONBLOCK; struct dentry *child = ERR_PTR(-EINVAL); struct path parent = { .mnt = fhp->fh_export->ex_path.mnt, -- 2.43.0