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Re: [patch 15/19] xfs: simplify xfs_qm_detach_gdquots

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: [patch 15/19] xfs: simplify xfs_qm_detach_gdquots
From: Ben Myers <bpm@xxxxxxx>
Date: Thu, 15 Dec 2011 10:43:14 -0600
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20111206215855.306880439@xxxxxxxxxxxxxxxxxxxxxx>
References: <20111206215806.844405397@xxxxxxxxxxxxxxxxxxxxxx> <20111206215855.306880439@xxxxxxxxxxxxxxxxxxxxxx>
User-agent: Mutt/1.5.18 (2008-05-17)
On Tue, Dec 06, 2011 at 04:58:21PM -0500, Christoph Hellwig wrote:
> There is no reason to drop qi_dqlist_lock around calls to xfs_qm_dqrele
> because the free list lock now nests inside qi_dqlist_lock and the
> dquot lock.
> 
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>
> 
> ---
>  fs/xfs/xfs_qm.c |   22 +++++-----------------
>  1 file changed, 5 insertions(+), 17 deletions(-)
> 
> Index: xfs/fs/xfs/xfs_qm.c
> ===================================================================
> --- xfs.orig/fs/xfs/xfs_qm.c  2011-10-27 22:40:07.538179215 +0200
> +++ xfs/fs/xfs/xfs_qm.c       2011-10-27 22:40:08.124671538 +0200
> @@ -449,7 +449,6 @@ xfs_qm_detach_gdquots(
>  {
>       struct xfs_quotainfo    *q = mp->m_quotainfo;
>       struct xfs_dquot        *dqp, *gdqp;
> -     int                     nrecl;
>  
>   again:
>       ASSERT(mutex_is_locked(&q->qi_dqlist_lock));
> @@ -462,25 +461,14 @@ xfs_qm_detach_gdquots(
>                       mutex_lock(&q->qi_dqlist_lock);
>                       goto again;
>               }
> -             if ((gdqp = dqp->q_gdquot)) {
> -                     xfs_dqlock(gdqp);

Why don't we need to take the dqlock on gdqp here before dropping the
lock on dqp?

> +
> +             gdqp = dqp->q_gdquot;
> +             if (gdqp)
>                       dqp->q_gdquot = NULL;
> -             }
>               xfs_dqunlock(dqp);
>  
> -             if (gdqp) {
> -                     /*
> -                      * Can't hold the mplist lock across a dqput.
> -                      * XXXmust convert to marker based iterations here.
> -                      */
> -                     nrecl = q->qi_dqreclaims;
> -                     mutex_unlock(&q->qi_dqlist_lock);
> -                     xfs_qm_dqput(gdqp);
> -
> -                     mutex_lock(&q->qi_dqlist_lock);
> -                     if (nrecl != q->qi_dqreclaims)

Why is it ok to ignore di_dqreclaims now?

> -                             goto again;
> -             }
> +             if (gdqp)
> +                     xfs_qm_dqrele(gdqp);
>       }
>  }
>  
> 
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