[Devel] [PATCH rh7 3/6] xfs: fix dquot isolation hang

[Vladimir Davydov]

From: Dave Chinner <david at fromorbit.com>

The new LRU list isolation code in xfs_qm_dquot_isolate() isn't
completely up to date.  Firstly, it needs conversion to return enum
lru_status values, not raw numbers. Secondly - most importantly - it
fails to unlock the dquot and relock the LRU in the LRU_RETRY path.
This leads to deadlocks in xfstests generic/232. Fix them.

Signed-off-by: Dave Chinner <dchinner at redhat.com>
Cc: Glauber Costa <glommer at gmail.com>
Cc: Michal Hocko <mhocko at suse.cz>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Al Viro <viro at zeniv.linux.org.uk>
(cherry picked from commit 35163417fb7a55a24b6b0ebb102e9991adf309aa)
Signed-off-by: Vladimir Davydov <vdavydov at virtuozzo.com>
---
 fs/xfs/xfs_qm.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c
index edf23494b594..1a454d162f14 100644
--- a/fs/xfs/xfs_qm.c
+++ b/fs/xfs/xfs_qm.c
@@ -451,7 +451,7 @@ xfs_qm_dquot_isolate(
 		trace_xfs_dqreclaim_want(dqp);
 		list_del_init(&dqp->q_lru);
 		XFS_STATS_DEC(xs_qm_dquot_unused);
-		return 0;
+		return LRU_REMOVED;
 	}
 
 	/*
@@ -497,17 +497,19 @@ xfs_qm_dquot_isolate(
 	XFS_STATS_DEC(xs_qm_dquot_unused);
 	trace_xfs_dqreclaim_done(dqp);
 	XFS_STATS_INC(xs_qm_dqreclaims);
-	return 0;
+	return LRU_REMOVED;
 
 out_miss_busy:
 	trace_xfs_dqreclaim_busy(dqp);
 	XFS_STATS_INC(xs_qm_dqreclaim_misses);
-	return 2;
+	return LRU_SKIP;
 
 out_unlock_dirty:
 	trace_xfs_dqreclaim_busy(dqp);
 	XFS_STATS_INC(xs_qm_dqreclaim_misses);
-	return 3;
+	xfs_dqunlock(dqp);
+	spin_lock(lru_lock);
+	return LRU_RETRY;
 }
 
 static unsigned long
-- 
2.1.4