Re: [PATCH 4/4] xfs: directory scrub should check the null bestfree entries too

[Chandan Babu R <chandanrlinux@gmail.com>]

On Monday 9 November 2020 11:47:58 PM IST Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> Teach the directory scrubber to check all the bestfree entries,
> including the null ones.  We want to be able to detect the case where
> the entry is null but there actually /is/ a directory data block.
> 
> Found by fuzzing lbests[0] = ones in xfs/391.
>

Looks good to me.

Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>

> Fixes: df481968f33b ("xfs: scrub directory freespace")
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
>  fs/xfs/scrub/dir.c |   27 ++++++++++++++++++++-------
>  1 file changed, 20 insertions(+), 7 deletions(-)
> 
> 
> diff --git a/fs/xfs/scrub/dir.c b/fs/xfs/scrub/dir.c
> index 7c432997edad..b045e95c2ea7 100644
> --- a/fs/xfs/scrub/dir.c
> +++ b/fs/xfs/scrub/dir.c
> @@ -558,14 +558,27 @@ xchk_directory_leaf1_bestfree(
>  	/* Check all the bestfree entries. */
>  	for (i = 0; i < bestcount; i++, bestp++) {
>  		best = be16_to_cpu(*bestp);
> +		error = xfs_dir3_data_read(sc->tp, sc->ip,
> +				xfs_dir2_db_to_da(args->geo, i),
> +				XFS_DABUF_MAP_HOLE_OK,
> +				&dbp);
> +		if (!xchk_fblock_process_error(sc, XFS_DATA_FORK, lblk,
> +				&error))
> +			break;
> +
> +		if (!dbp) {
> +			if (best != NULLDATAOFF) {
> +				xchk_fblock_set_corrupt(sc, XFS_DATA_FORK,
> +						lblk);
> +				break;
> +			}
> +			continue;
> +		}
> +
>  		if (best == NULLDATAOFF)
> -			continue;
> -		error = xfs_dir3_data_read(sc->tp, sc->ip,
> -				i * args->geo->fsbcount, 0, &dbp);
> -		if (!xchk_fblock_process_error(sc, XFS_DATA_FORK, lblk,
> -				&error))
> -			break;
> -		xchk_directory_check_freesp(sc, lblk, dbp, best);
> +			xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, lblk);
> +		else
> +			xchk_directory_check_freesp(sc, lblk, dbp, best);
>  		xfs_trans_brelse(sc->tp, dbp);
>  		if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
>  			break;
> 
> 


-- 
chandan