nfsd: drop st_mutex before calling move_to_close_lru()
[ Upstream commit 56c35f43eef013579c76c007ba1f386d8c2cac14 ]
move_to_close_lru() is currently called with ->st_mutex held.
This can lead to a deadlock as move_to_close_lru() waits for sc_count to
drop to 2, and some threads holding a reference might be waiting for the
mutex. These references will never be dropped so sc_count will never
reach 2.
There can be no harm in dropping ->st_mutex before
move_to_close_lru() because the only place that takes the mutex is
nfsd4_lock_ol_stateid(), and it quickly aborts if sc_type is
NFS4_CLOSED_STID, which it will be before move_to_close_lru() is called.
See also
https://lore.kernel.org/lkml/4dd1fe21e11344e5969bb112e954affb@jd.com/T/
where this problem was raised but not successfully resolved.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
(cherry picked from commit 52d3370e8022ce28cd8cf4d16c09245aa683d7fb)
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
1 file changed