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Re: [PATCH] xfs: bulkstat doesn't release AGI buffer on error

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH] xfs: bulkstat doesn't release AGI buffer on error
From: Brian Foster <bfoster@xxxxxxxxxx>
Date: Wed, 15 Oct 2014 08:59:27 -0400
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1413324728-4008-1-git-send-email-david@xxxxxxxxxxxxx>
References: <1413324728-4008-1-git-send-email-david@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.23 (2014-03-12)
On Wed, Oct 15, 2014 at 09:12:08AM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
> 
> The recent refactoring of the bulkstat code left a small landmine in
> the code. If a inobt read fails, then the tree walk is aborted and
> returns without releasing the AGI buffer or freeing the cursor. This
> can lead to a subsequent bulkstat call hanging trying to grab the
> AGI buffer again.
> 
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> ---

Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>

>  fs/xfs/xfs_itable.c | 16 ++++++++++------
>  1 file changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/xfs/xfs_itable.c b/fs/xfs/xfs_itable.c
> index f1deb96..ef8ea05 100644
> --- a/fs/xfs/xfs_itable.c
> +++ b/fs/xfs/xfs_itable.c
> @@ -427,7 +427,7 @@ xfs_bulkstat(
>  
>                       error = xfs_bulkstat_grab_ichunk(cur, agino, &icount, 
> &r);
>                       if (error)
> -                             break;
> +                             goto del_cursor;
>                       if (icount) {
>                               irbp->ir_startino = r.ir_startino;
>                               irbp->ir_freecount = r.ir_freecount;
> @@ -442,7 +442,7 @@ xfs_bulkstat(
>                       error = xfs_inobt_lookup(cur, 0, XFS_LOOKUP_GE, &tmp);
>               }
>               if (error)
> -                     break;
> +                     goto del_cursor;
>  
>               /*
>                * Loop through inode btree records in this ag,
> @@ -454,7 +454,7 @@ xfs_bulkstat(
>                       error = xfs_inobt_get_rec(cur, &r, &i);
>                       if (error || i == 0) {
>                               end_of_ag = 1;
> -                             break;
> +                             goto del_cursor;
>                       }
>  
>                       /*
> @@ -476,13 +476,17 @@ xfs_bulkstat(
>                       error = xfs_btree_increment(cur, 0, &tmp);
>                       cond_resched();
>               }
> +
>               /*
> -              * Drop the btree buffers and the agi buffer.
> -              * We can't hold any of the locks these represent
> -              * when calling iget.
> +              * Drop the btree buffers and the agi buffer as we can't hold 
> any
> +              * of the locks these represent when calling iget. If there is a
> +              * pending error, then we are done.
>                */
> +del_cursor:
>               xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
>               xfs_buf_relse(agbp);
> +             if (error)
> +                     break;
>               /*
>                * Now format all the good inodes into the user's buffer.
>                */
> -- 
> 2.0.0
> 
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