Re: [PATCH 29/46] xfs: cleanup xfs_dir2_block_getdents

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

On Thu, Nov 07, 2019 at 07:23:53PM +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 fine,
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

> ---
>  fs/xfs/xfs_dir2_readdir.c | 32 ++++++++++++--------------------
>  1 file changed, 12 insertions(+), 20 deletions(-)
> 
> diff --git a/fs/xfs/xfs_dir2_readdir.c b/fs/xfs/xfs_dir2_readdir.c
> index 187bb51875c2..0d234b649d65 100644
> --- a/fs/xfs/xfs_dir2_readdir.c
> +++ b/fs/xfs/xfs_dir2_readdir.c
> @@ -142,17 +142,14 @@ xfs_dir2_block_getdents(
>  	struct dir_context	*ctx)
>  {
>  	struct xfs_inode	*dp = args->dp;	/* incore directory inode */
> -	xfs_dir2_data_hdr_t	*hdr;		/* block header */
>  	struct xfs_buf		*bp;		/* buffer for block */
> -	xfs_dir2_data_entry_t	*dep;		/* block data entry */
> -	xfs_dir2_data_unused_t	*dup;		/* block unused entry */
> -	char			*endptr;	/* end of the data entries */
>  	int			error;		/* error return value */
> -	char			*ptr;		/* current data entry */
>  	int			wantoff;	/* starting block offset */
>  	xfs_off_t		cook;
>  	struct xfs_da_geometry	*geo = args->geo;
>  	int			lock_mode;
> +	unsigned int		offset;
> +	unsigned int		end;
>  
>  	/*
>  	 * If the block number in the offset is out of range, we're done.
> @@ -171,44 +168,39 @@ xfs_dir2_block_getdents(
>  	 * We'll skip entries before this.
>  	 */
>  	wantoff = xfs_dir2_dataptr_to_off(geo, ctx->pos);
> -	hdr = bp->b_addr;
>  	xfs_dir3_data_check(dp, bp);
> -	/*
> -	 * Set up values for the loop.
> -	 */
> -	ptr = (char *)dp->d_ops->data_entry_p(hdr);
> -	endptr = xfs_dir3_data_endp(geo, hdr);
>  
>  	/*
>  	 * Loop over the data portion of the block.
>  	 * Each object is a real entry (dep) or an unused one (dup).
>  	 */
> -	while (ptr < endptr) {
> +	offset = dp->d_ops->data_entry_offset;
> +	end = xfs_dir3_data_endp(geo, bp->b_addr) - bp->b_addr;
> +	while (offset < end) {
> +		struct xfs_dir2_data_unused	*dup = bp->b_addr + offset;
> +		struct xfs_dir2_data_entry	*dep = bp->b_addr + offset;
>  		uint8_t filetype;
>  
> -		dup = (xfs_dir2_data_unused_t *)ptr;
>  		/*
>  		 * Unused, skip it.
>  		 */
>  		if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
> -			ptr += be16_to_cpu(dup->length);
> +			offset += be16_to_cpu(dup->length);
>  			continue;
>  		}
>  
> -		dep = (xfs_dir2_data_entry_t *)ptr;
> -
>  		/*
>  		 * Bump pointer for the next iteration.
>  		 */
> -		ptr += dp->d_ops->data_entsize(dep->namelen);
> +		offset += dp->d_ops->data_entsize(dep->namelen);
> +
>  		/*
>  		 * The entry is before the desired starting point, skip it.
>  		 */
> -		if ((char *)dep - (char *)hdr < wantoff)
> +		if (offset < wantoff)
>  			continue;
>  
> -		cook = xfs_dir2_db_off_to_dataptr(geo, geo->datablk,
> -					    (char *)dep - (char *)hdr);
> +		cook = xfs_dir2_db_off_to_dataptr(geo, geo->datablk, offset);
>  
>  		ctx->pos = cook & 0x7fffffff;
>  		filetype = dp->d_ops->data_get_ftype(dep);
> -- 
> 2.20.1
>