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[PATCH] [MMOTM] xfs: fix dquot isolation hang

To: akpm@xxxxxxxxxxxxxxxxxxxx
Subject: [PATCH] [MMOTM] xfs: fix dquot isolation hang
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Mon, 8 Jul 2013 16:34:21 +1000
Cc: xfs@xxxxxxxxxxx, linux-mm@xxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, glommer@xxxxxxxxxx, mhocko@xxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
From: Dave Chinner <dchinner@xxxxxxxxxx>

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@xxxxxxxxxx>
---
 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 46743cf..a10a720 100644
--- a/fs/xfs/xfs_qm.c
+++ b/fs/xfs/xfs_qm.c
@@ -659,7 +659,7 @@ 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;
        }
 
        /*
@@ -705,17 +705,19 @@ 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
-- 
1.8.3.2

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