xfs: fix dquot isolation hang

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@redhat.com>
Cc: Glauber Costa <glommer@gmail.com>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c
index 1a4217e..a29169b 100644 (file)
--- a/fs/xfs/xfs_qm.c
+++ b/fs/xfs/xfs_qm.c
@@ -707,7 +707,7 @@ 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;
        }
 
        /*
@@ -753,17 +753,19 @@ 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