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Re: [PATCH] xfs: fix error handling in xfs_qm_log_quotaoff()

To: Brian Foster <bfoster@xxxxxxxxxx>
Subject: Re: [PATCH] xfs: fix error handling in xfs_qm_log_quotaoff()
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Mon, 20 Oct 2014 11:31:20 +1100
Cc: xfs@xxxxxxxxxxx, Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1413466773-56087-1-git-send-email-bfoster@xxxxxxxxxx>
References: <1413466773-56087-1-git-send-email-bfoster@xxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Thu, Oct 16, 2014 at 09:39:33AM -0400, Brian Foster wrote:
> The error handling in xfs_qm_log_quotaoff() has a couple problems. If
> xfs_trans_commit() fails, we fall through to the error block and call
> xfs_trans_cancel(). This is incorrect on commit failure. If
> xfs_trans_reserve() fails, we jump to the error block, cancel the tp and
> restore the superblock qflags to oldsbqflag. However, oldsbqflag has
> been initialized to zero and not yet updated from the original flags so
> we set the flags to zero.
> 
> Fix up the error handling in xfs_qm_log_quotaoff() to not restore flags
> if they haven't been modified and not cancel the tp on commit failure.
> 
> Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
> ---
>  fs/xfs/xfs_qm_syscalls.c | 35 ++++++++++++++++++++---------------
>  1 file changed, 20 insertions(+), 15 deletions(-)
> 
> diff --git a/fs/xfs/xfs_qm_syscalls.c b/fs/xfs/xfs_qm_syscalls.c
> index 80f2d77..f2d454e 100644
> --- a/fs/xfs/xfs_qm_syscalls.c
> +++ b/fs/xfs/xfs_qm_syscalls.c
> @@ -784,13 +784,17 @@ xfs_qm_log_quotaoff(
>  {
>       xfs_trans_t            *tp;
>       int                     error;
> -     xfs_qoff_logitem_t     *qoffi=NULL;
> -     uint                    oldsbqflag=0;
> +     xfs_qoff_logitem_t     *qoffi;
> +     uint                    oldsbqflag;
> +
> +     *qoffstartp = NULL;
>  
>       tp = xfs_trans_alloc(mp, XFS_TRANS_QM_QUOTAOFF);
>       error = xfs_trans_reserve(tp, &M_RES(mp)->tr_qm_quotaoff, 0, 0);
> -     if (error)
> -             goto error0;
> +     if (error) {
> +             xfs_trans_cancel(tp, 0);
> +             return error;
> +     }
>  
>       qoffi = xfs_trans_get_qoff_item(tp, NULL, flags & XFS_ALL_QUOTA_ACCT);
>       xfs_trans_log_quotaoff_item(tp, qoffi);
> @@ -809,19 +813,20 @@ xfs_qm_log_quotaoff(
>        */
>       xfs_trans_set_sync(tp);
>       error = xfs_trans_commit(tp, 0);
> +     if (error)
> +             goto error_flags;


If the commit fails, the filesystem will be shut down and the state
of the quota flags is completely irrelevant at this point so there's
no reason to restore them. Indeed, is restoring them even the right
thing to do? The commit *may* have made it to disk, but a
subsequent error during completion handling resulted in the commit
failing....

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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