[PATCH AUTOSEL 5.6 012/129] xfs: fix iclog release error check race with shutdown

Sasha Levin
2020-04-15T13:22:59Z

From: Brian Foster <bfoster@redhat.com>

[ Upstream commit 6b789c337a5963ae57cbc7fe9e41488c40a9b014 ]

Prior to commit df732b29c8 ("xfs: call xlog_state_release_iclog with
l_icloglock held"), xlog_state_release_iclog() always performed a
locked check of the iclog error state before proceeding into the
sync state processing code. As of this commit, part of
xlog_state_release_iclog() was open-coded into
xfs_log_release_iclog() and as a result the locked error state check
was lost.

The lockless check still exists, but this doesn't account for the
possibility of a race with a shutdown being performed by another
task causing the iclog state to change while the original task waits
on ->l_icloglock. This has reproduced very rarely via generic/475
and manifests as an assert failure in __xlog_state_release_iclog()
due to an unexpected iclog state.

Restore the locked error state check in xlog_state_release_iclog()
to ensure that an iclog state update via shutdown doesn't race with
the iclog release state processing code.

Fixes: df732b29c807 ("xfs: call xlog_state_release_iclog with l_icloglock held")
Reported-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/xfs/xfs_log.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index f6006d94a581e..796ff37d5bb5b 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -605,18 +605,23 @@ xfs_log_release_iclog(
struct xlog *log = mp->m_log;
bool sync;

- if (iclog->ic_state == XLOG_STATE_IOERROR) {
- xfs_force_shutdown(mp, SHUTDOWN_LOG_IO_ERROR);
- return -EIO;
- }
+ if (iclog->ic_state == XLOG_STATE_IOERROR)
+ goto error;

if (atomic_dec_and_lock(&iclog->ic_refcnt, &log->l_icloglock)) {
+ if (iclog->ic_state == XLOG_STATE_IOERROR) {
+ spin_unlock(&log->l_icloglock);
+ goto error;
+ }
sync = __xlog_state_release_iclog(log, iclog);
spin_unlock(&log->l_icloglock);
if (sync)
xlog_sync(log, iclog);
}
return 0;
+error:
+ xfs_force_shutdown(mp, SHUTDOWN_LOG_IO_ERROR);
+ return -EIO;
}

/*
--
2.20.1