linux-kernel - Re: [PATCH v2 1/2] xfs: ensure logflagsp is initialized in xfs_bmap_del_extent

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Message-ID: <ZWb+pR7AvTY8VLRR@dread.disaster.area>
Date:   Wed, 29 Nov 2023 20:04:37 +1100
From:   Dave Chinner <david@...morbit.com>
To:     Jiachen Zhang <zhangjiachen.jaycee@...edance.com>
Cc:     Chandan Babu R <chandan.babu@...cle.com>,
        "Darrick J. Wong" <djwong@...nel.org>,
        Dave Chinner <dchinner@...hat.com>,
        Allison Henderson <allison.henderson@...cle.com>,
        Zhang Tianci <zhangtianci.1997@...edance.com>,
        Brian Foster <bfoster@...hat.com>, Ben Myers <bpm@....com>,
        linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        xieyongji@...edance.com, me@...x.top,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v2 1/2] xfs: ensure logflagsp is initialized in
 xfs_bmap_del_extent_real

On Wed, Nov 29, 2023 at 03:58:31PM +0800, Jiachen Zhang wrote:
> In the case of returning -ENOSPC, ensure logflagsp is initialized by 0.
> Otherwise the caller __xfs_bunmapi will set uninitialized illegal
> tmp_logflags value into xfs log, which might cause unpredictable error
> in the log recovery procedure.
> 
> Also, remove the flags variable and set the *logflagsp directly, so that
> the code should be more robust in the long run.
> 
> Fixes: 1b24b633aafe ("xfs: move some more code into xfs_bmap_del_extent_real")
> Signed-off-by: Jiachen Zhang <zhangjiachen.jaycee@...edance.com>
> Reviewed-by: Christoph Hellwig <hch@....de>
> ---
>  fs/xfs/libxfs/xfs_bmap.c | 26 ++++++++++++++------------
>  1 file changed, 14 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index be62acffad6c..9435bd6c950b 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -5010,7 +5010,6 @@ xfs_bmap_del_extent_real(
>  	xfs_fileoff_t		del_endoff;	/* first offset past del */
>  	int			do_fx;	/* free extent at end of routine */
>  	int			error;	/* error return value */
> -	int			flags = 0;/* inode logging flags */
>  	struct xfs_bmbt_irec	got;	/* current extent entry */
>  	xfs_fileoff_t		got_endoff;	/* first offset past got */
>  	int			i;	/* temp state */
> @@ -5023,6 +5022,8 @@ xfs_bmap_del_extent_real(
>  	uint32_t		state = xfs_bmap_fork_to_state(whichfork);
>  	struct xfs_bmbt_irec	old;
>  
> +	*logflagsp = 0;
> +
>  	mp = ip->i_mount;
>  	XFS_STATS_INC(mp, xs_del_exlist);
>  
> @@ -5048,10 +5049,12 @@ xfs_bmap_del_extent_real(
>  	if (tp->t_blk_res == 0 &&
>  	    ifp->if_format == XFS_DINODE_FMT_EXTENTS &&
>  	    ifp->if_nextents >= XFS_IFORK_MAXEXT(ip, whichfork) &&
> -	    del->br_startoff > got.br_startoff && del_endoff < got_endoff)
> -		return -ENOSPC;
> +	    del->br_startoff > got.br_startoff && del_endoff < got_endoff) {
> +		error = -ENOSPC;
> +		goto done;
> +	}

Now that you've added initialisation of logflagsp, the need for the
error stacking goto pattern goes away completely. Anywhere that has
a "goto done" can be converted to a direct 'return error' call and
the done label can be removed.

-Dave.
-- 
Dave Chinner
david@...morbit.com