Re: [PATCH 30/46] xfs: cleanup xfs_dir2_leaf_getdents

Darrick J. Wong
2019-11-07T22:42:06Z

On Thu, Nov 07, 2019 at 07:23:54PM +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>
> ---
> fs/xfs/xfs_dir2_readdir.c | 34 +++++++++++++++++-----------------
> 1 file changed, 17 insertions(+), 17 deletions(-)
>
> diff --git a/fs/xfs/xfs_dir2_readdir.c b/fs/xfs/xfs_dir2_readdir.c
> index 0d234b649d65..c4314e9e3dd8 100644
> --- a/fs/xfs/xfs_dir2_readdir.c
> +++ b/fs/xfs/xfs_dir2_readdir.c
> @@ -351,13 +351,13 @@ xfs_dir2_leaf_getdents(
> xfs_dir2_data_hdr_t *hdr; /* data block header */

gcc complained about this variable being set but not used.

> xfs_dir2_data_entry_t *dep; /* data entry */
> xfs_dir2_data_unused_t *dup; /* unused entry */
> - char *ptr = NULL; /* pointer to current data */
> struct xfs_da_geometry *geo = args->geo;
> xfs_dablk_t rablk = 0; /* current readahead block */
> xfs_dir2_off_t curoff; /* current overall offset */
> int length; /* temporary length value */
> int byteoff; /* offset in current block */
> int lock_mode;
> + unsigned int offset = 0;

This is the offset within the block, right?

> int error = 0; /* error return value */
>
> /*
> @@ -384,7 +384,7 @@ xfs_dir2_leaf_getdents(
> * If we have no buffer, or we're off the end of the
> * current buffer, need to get another one.
> */
> - if (!bp || ptr >= (char *)bp->b_addr + geo->blksize) {
> + if (!bp || offset + geo->blksize) {

^^^^^^^^^^^^^^^^^^^^^

In which case, isn't this always true? Was this supposed to be
offset >= geo->blksize?

--D

> if (bp) {
> xfs_trans_brelse(args->trans, bp);
> bp = NULL;
> @@ -402,7 +402,7 @@ xfs_dir2_leaf_getdents(
> /*
> * Find our position in the block.
> */
> - ptr = (char *)dp->d_ops->data_entry_p(hdr);
> + offset = dp->d_ops->data_entry_offset;
> byteoff = xfs_dir2_byte_to_off(geo, curoff);
> /*
> * Skip past the header.
> @@ -413,20 +413,20 @@ xfs_dir2_leaf_getdents(
> * Skip past entries until we reach our offset.
> */
> else {
> - while ((char *)ptr - (char *)hdr < byteoff) {
> - dup = (xfs_dir2_data_unused_t *)ptr;
> + while (offset < byteoff) {
> + dup = bp->b_addr + offset;
>
> if (be16_to_cpu(dup->freetag)
> == XFS_DIR2_DATA_FREE_TAG) {
>
> length = be16_to_cpu(dup->length);
> - ptr += length;
> + offset += length;
> continue;
> }
> - dep = (xfs_dir2_data_entry_t *)ptr;
> + dep = bp->b_addr + offset;
> length =
> dp->d_ops->data_entsize(dep->namelen);
> - ptr += length;
> + offset += length;
> }
> /*
> * Now set our real offset.
> @@ -434,28 +434,28 @@ xfs_dir2_leaf_getdents(
> curoff =
> xfs_dir2_db_off_to_byte(geo,
> xfs_dir2_byte_to_db(geo, curoff),
> - (char *)ptr - (char *)hdr);
> - if (ptr >= (char *)hdr + geo->blksize) {
> + offset);
> + if (offset >= geo->blksize)
> continue;
> - }
> }
> }
> +
> /*
> - * We have a pointer to an entry.
> - * Is it a live one?
> + * We have a pointer to an entry. Is it a live one?
> */
> - dup = (xfs_dir2_data_unused_t *)ptr;
> + dup = bp->b_addr + offset;
> +
> /*
> * No, it's unused, skip over it.
> */
> if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
> length = be16_to_cpu(dup->length);
> - ptr += length;
> + offset += length;
> curoff += length;
> continue;
> }
>
> - dep = (xfs_dir2_data_entry_t *)ptr;
> + dep = bp->b_addr + offset;
> length = dp->d_ops->data_entsize(dep->namelen);
> filetype = dp->d_ops->data_get_ftype(dep);
>
> @@ -474,7 +474,7 @@ xfs_dir2_leaf_getdents(
> /*
> * Advance to next entry in the block.
> */
> - ptr += length;
> + offset += length;
> curoff += length;
> /* bufsize may have just been a guess; don't go negative */
> bufsize = bufsize > length ? bufsize - length : 0;
> --
> 2.20.1
>