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

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH] [MMOTM] xfs: fix dquot isolation hang
From: Glauber Costa <glommer@xxxxxxxxx>
Date: Tue, 9 Jul 2013 22:02:05 +0400
Cc: akpm@xxxxxxxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx, linux-mm@xxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, glommer@xxxxxxxxxx, mhocko@xxxxxxx
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Michal and Andrew, here is the patch

On Mon, Jul 08, 2013 at 04:34:21PM +1000, Dave Chinner wrote:
> 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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