Re: [PATCH 2/9] xfs: improve the xfs_dabuf_map calling conventions

Darrick J. Wong
2019-11-17T18:35:36Z

On Sat, Nov 16, 2019 at 07:22:07PM +0100, Christoph Hellwig wrote:
> Use a flags argument with the XFS_DABUF_MAP_HOLE_OK flag to signal that
> a hole is okay and not corruption, and return -ENOENT instead of the
> nameless -1 to signal that case in the return value.

Why not set *nirecs = 0 and return 0 like we sometimes do for bmap
lookups?

--D

>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> fs/xfs/libxfs/xfs_da_btree.c | 25 +++++++++++++++----------
> fs/xfs/libxfs/xfs_da_btree.h | 3 +++
> 2 files changed, 18 insertions(+), 10 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_da_btree.c b/fs/xfs/libxfs/xfs_da_btree.c
> index 681fba5731c2..c26f139bcf00 100644
> --- a/fs/xfs/libxfs/xfs_da_btree.c
> +++ b/fs/xfs/libxfs/xfs_da_btree.c
> @@ -2571,7 +2571,7 @@ static int
> xfs_dabuf_map(
> struct xfs_inode *dp,
> xfs_dablk_t bno,
> - xfs_daddr_t mappedbno,
> + unsigned int flags,
> int whichfork,
> struct xfs_buf_map **map,
> int *nmaps)
> @@ -2596,8 +2596,8 @@ xfs_dabuf_map(
>
> if (!xfs_da_map_covers_blocks(nirecs, irecs, bno, nfsb)) {
> /* Caller ok with no mapping. */
> - if (mappedbno == -2) {
> - error = -1;
> + if (flags & XFS_DABUF_MAP_HOLE_OK) {
> + error = -ENOENT;
> goto out;
> }
>
> @@ -2655,10 +2655,12 @@ xfs_da_get_buf(
> goto done;
> }
>
> - error = xfs_dabuf_map(dp, bno, mappedbno, whichfork, &mapp, &nmap);
> + error = xfs_dabuf_map(dp, bno,
> + mappedbno == -1 ? XFS_DABUF_MAP_HOLE_OK : 0,
> + whichfork, &mapp, &nmap);
> if (error) {
> /* mapping a hole is not an error, but we don't continue */
> - if (error == -1)
> + if (error == -ENOENT)
> error = 0;
> goto out_free;
> }
> @@ -2710,10 +2712,12 @@ xfs_da_read_buf(
> goto done;
> }
>
> - error = xfs_dabuf_map(dp, bno, mappedbno, whichfork, &mapp, &nmap);
> + error = xfs_dabuf_map(dp, bno,
> + mappedbno == -1 ? XFS_DABUF_MAP_HOLE_OK : 0,
> + whichfork, &mapp, &nmap);
> if (error) {
> /* mapping a hole is not an error, but we don't continue */
> - if (error == -1)
> + if (error == -ENOENT)
> error = 0;
> goto out_free;
> }
> @@ -2757,11 +2761,12 @@ xfs_da_reada_buf(
>
> mapp = &map;
> nmap = 1;
> - error = xfs_dabuf_map(dp, bno, mappedbno, whichfork,
> - &mapp, &nmap);
> + error = xfs_dabuf_map(dp, bno,
> + mappedbno == -1 ? XFS_DABUF_MAP_HOLE_OK : 0,
> + whichfork, &mapp, &nmap);
> if (error) {
> /* mapping a hole is not an error, but we don't continue */
> - if (error == -1)
> + if (error == -ENOENT)
> error = 0;
> goto out_free;
> }
> diff --git a/fs/xfs/libxfs/xfs_da_btree.h b/fs/xfs/libxfs/xfs_da_btree.h
> index 5af4df71e92b..9ec0d0243e96 100644
> --- a/fs/xfs/libxfs/xfs_da_btree.h
> +++ b/fs/xfs/libxfs/xfs_da_btree.h
> @@ -204,6 +204,9 @@ int xfs_da3_node_read(struct xfs_trans *tp, struct xfs_inode *dp,
> /*
> * Utility routines.
> */
> +
> +#define XFS_DABUF_MAP_HOLE_OK (1 << 0)
> +
> int xfs_da_grow_inode(xfs_da_args_t *args, xfs_dablk_t *new_blkno);
> int xfs_da_grow_inode_int(struct xfs_da_args *args, xfs_fileoff_t *bno,
> int count);
> --
> 2.20.1
>