linux-kernel - [Patch 0/2] NFSD: Fix server hang when there are multiple layout conflicts

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Message-ID: <20251106170729.310683-1-dai.ngo@oracle.com>
Date: Thu,  6 Nov 2025 09:05:24 -0800
From: Dai Ngo <dai.ngo@...cle.com>
To: chuck.lever@...cle.com, jlayton@...nel.org, neilb@...mail.net,
        okorniev@...hat.com, tom@...pey.com, hch@....de, alex.aring@...il.com,
        viro@...iv.linux.org.uk, brauner@...nel.org, jack@...e.cz
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-nfs@...r.kernel.org
Subject: [Patch 0/2] NFSD: Fix server hang when there are multiple layout conflicts

When a layout conflict triggers a call to __break_lease, the function
nfsd4_layout_lm_break clears the fl_break_time timeout before sending
the CB_LAYOUTRECALL. As a result, __break_lease repeatedly restarts
its loop, waiting indefinitely for the conflicting file lease to be
released.

If the number of lease conflicts matches the number of NFSD threads (which
defaults to 8), all available NFSD threads become occupied. Consequently,
there are no threads left to handle incoming requests or callback replies,
leading to a total hang of the NFS server.

This issue is reliably reproducible by running the Git test suite on a
configuration using SCSI layout.

This patchset fixes this problem by introducing the new lm_breaker_timedout
operation to lease_manager_operations and using timeout for layout
lease break.

 Documentation/filesystems/locking.rst |  2 ++
 fs/locks.c                            | 14 +++++++++++---
 fs/nfsd/nfs4layouts.c                 | 25 +++++++++++++++++++++----
 include/linux/filelock.h              |  2 ++
 4 files changed, 36 insertions(+), 7 deletions(-)