Re: [PATCH 32/46] xfs: cleanup xchk_directory_data_bestfree

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Thu, Nov 07, 2019 at 07:23:56PM +0100, Christoph Hellwig wrote:
> Use an offset as the main means for iteration, and only do pointer
> arithmetics to find the data/unused entries.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Looks ok,
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

> ---
>  fs/xfs/scrub/dir.c | 31 +++++++++++++++----------------
>  1 file changed, 15 insertions(+), 16 deletions(-)
> 
> diff --git a/fs/xfs/scrub/dir.c b/fs/xfs/scrub/dir.c
> index 501d60c9b09a..4cef21b9d336 100644
> --- a/fs/xfs/scrub/dir.c
> +++ b/fs/xfs/scrub/dir.c
> @@ -327,14 +327,13 @@ xchk_directory_data_bestfree(
>  	struct xfs_dir2_data_free	*bf;
>  	struct xfs_mount		*mp = sc->mp;
>  	const struct xfs_dir_ops	*d_ops;
> -	char				*ptr;
> -	char				*endptr;
>  	u16				tag;
>  	unsigned int			nr_bestfrees = 0;
>  	unsigned int			nr_frees = 0;
>  	unsigned int			smallest_bestfree;
>  	int				newlen;
> -	int				offset;
> +	unsigned int			offset;
> +	unsigned int			end;
>  	int				error;
>  
>  	d_ops = sc->ip->d_ops;
> @@ -368,13 +367,13 @@ xchk_directory_data_bestfree(
>  			xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, lblk);
>  			goto out_buf;
>  		}
> -		dup = (struct xfs_dir2_data_unused *)(bp->b_addr + offset);
> +		dup = bp->b_addr + offset;
>  		tag = be16_to_cpu(*xfs_dir2_data_unused_tag_p(dup));
>  
>  		/* bestfree doesn't match the entry it points at? */
>  		if (dup->freetag != cpu_to_be16(XFS_DIR2_DATA_FREE_TAG) ||
>  		    be16_to_cpu(dup->length) != be16_to_cpu(dfp->length) ||
> -		    tag != ((char *)dup - (char *)bp->b_addr)) {
> +		    tag != offset) {
>  			xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, lblk);
>  			goto out_buf;
>  		}
> @@ -390,30 +389,30 @@ xchk_directory_data_bestfree(
>  	}
>  
>  	/* Make sure the bestfrees are actually the best free spaces. */
> -	ptr = (char *)d_ops->data_entry_p(bp->b_addr);
> -	endptr = xfs_dir3_data_endp(mp->m_dir_geo, bp->b_addr);
> +	offset = d_ops->data_entry_offset;
> +	end = xfs_dir3_data_endp(mp->m_dir_geo, bp->b_addr) - bp->b_addr;
>  
>  	/* Iterate the entries, stopping when we hit or go past the end. */
> -	while (ptr < endptr) {
> -		dup = (struct xfs_dir2_data_unused *)ptr;
> +	while (offset < end) {
> +		dup = bp->b_addr + offset;
> +
>  		/* Skip real entries */
>  		if (dup->freetag != cpu_to_be16(XFS_DIR2_DATA_FREE_TAG)) {
> -			struct xfs_dir2_data_entry	*dep;
> +			struct xfs_dir2_data_entry *dep = bp->b_addr + offset;
>  
> -			dep = (struct xfs_dir2_data_entry *)ptr;
>  			newlen = d_ops->data_entsize(dep->namelen);
>  			if (newlen <= 0) {
>  				xchk_fblock_set_corrupt(sc, XFS_DATA_FORK,
>  						lblk);
>  				goto out_buf;
>  			}
> -			ptr += newlen;
> +			offset += newlen;
>  			continue;
>  		}
>  
>  		/* Spot check this free entry */
>  		tag = be16_to_cpu(*xfs_dir2_data_unused_tag_p(dup));
> -		if (tag != ((char *)dup - (char *)bp->b_addr)) {
> +		if (tag != offset) {
>  			xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, lblk);
>  			goto out_buf;
>  		}
> @@ -432,13 +431,13 @@ xchk_directory_data_bestfree(
>  			xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, lblk);
>  			goto out_buf;
>  		}
> -		ptr += newlen;
> -		if (ptr <= endptr)
> +		offset += newlen;
> +		if (offset <= end)
>  			nr_frees++;
>  	}
>  
>  	/* We're required to fill all the space. */
> -	if (ptr != endptr)
> +	if (offset != end)
>  		xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, lblk);
>  
>  	/* Did we see at least as many free slots as there are bestfrees? */
> -- 
> 2.20.1
>