linux-kernel - [PATCH 5.6 050/166] xfs: fix iclog release error check race with shutdown

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Message-Id: <20200422095054.425468418@linuxfoundation.org>
Date:   Wed, 22 Apr 2020 11:56:17 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Zorro Lang <zlang@...hat.com>,
        Brian Foster <bfoster@...hat.com>,
        Christoph Hellwig <hch@....de>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.6 050/166] xfs: fix iclog release error check race with shutdown

From: Brian Foster <bfoster@...hat.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@...hat.com>
Signed-off-by: Brian Foster <bfoster@...hat.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Reviewed-by: Darrick J. Wong <darrick.wong@...cle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
Signed-off-by: Sasha Levin <sashal@...nel.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