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

Darrick J. Wong
2019-11-08T00:52:35Z

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
>