Re: [PATCH 03/10] xfs: improve the xfs_dabuf_map calling conventions

Darrick J. Wong
2019-11-20T18:17:16Z

On Wed, Nov 20, 2019 at 12:17:20PM +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 0 with *nmap set to 0 to
> signal that case in the return value instead of a nameless -1 return
> code.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> fs/xfs/libxfs/xfs_da_btree.c | 39 +++++++++++++-----------------------
> fs/xfs/libxfs/xfs_da_btree.h | 3 +++
> 2 files changed, 17 insertions(+), 25 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_da_btree.c b/fs/xfs/libxfs/xfs_da_btree.c
> index e078817fc26c..d85dd99d28a3 100644
> --- a/fs/xfs/libxfs/xfs_da_btree.c
> +++ b/fs/xfs/libxfs/xfs_da_btree.c
> @@ -2460,19 +2460,11 @@ xfs_da_shrink_inode(
> return error;
> }
>
> -/*
> - * Map the block we are given ready for reading. There are three possible return
> - * values:
> - * -1 - will be returned if we land in a hole and mappedbno == -2 so the
> - * caller knows not to execute a subsequent read.
> - * 0 - if we mapped the block successfully
> - * >0 - positive error number if there was an error.
> - */
> 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 **mapp,
> int *nmaps)
> @@ -2527,7 +2519,7 @@ xfs_dabuf_map(
>
> invalid_mapping:
> /* Caller ok with no mapping. */
> - if (XFS_IS_CORRUPT(mp, mappedbno != -2)) {
> + if (XFS_IS_CORRUPT(mp, !flags & XFS_DABUF_MAP_HOLE_OK)) {
> error = -EFSCORRUPTED;
> if (xfs_error_level >= XFS_ERRLEVEL_LOW) {
> xfs_alert(mp, "%s: bno %u inode %llu",
> @@ -2575,13 +2567,11 @@ xfs_da_get_buf(
> goto done;
> }
>
> - error = xfs_dabuf_map(dp, bno, mappedbno, whichfork, &mapp, &nmap);
> - if (error) {
> - /* mapping a hole is not an error, but we don't continue */
> - if (error == -1)
> - error = 0;
> + error = xfs_dabuf_map(dp, bno,
> + mappedbno == -1 ? XFS_DABUF_MAP_HOLE_OK : 0,
> + whichfork, &mapp, &nmap);
> + if (error || nmap == 0)
> goto out_free;
> - }
>
> bp = xfs_trans_get_buf_map(tp, mp->m_ddev_targp, mapp, nmap, 0);
> done:
> @@ -2630,13 +2620,11 @@ xfs_da_read_buf(
> goto done;
> }
>
> - error = xfs_dabuf_map(dp, bno, mappedbno, whichfork, &mapp, &nmap);
> - if (error) {
> - /* mapping a hole is not an error, but we don't continue */
> - if (error == -1)
> - error = 0;
> + error = xfs_dabuf_map(dp, bno,
> + mappedbno == -1 ? XFS_DABUF_MAP_HOLE_OK : 0,
> + whichfork, &mapp, &nmap);
> + if (error || !nmap)
> goto out_free;
> - }
>
> error = xfs_trans_read_buf_map(mp, tp, mp->m_ddev_targp, mapp, nmap, 0,
> &bp, ops);
> @@ -2677,11 +2665,12 @@ 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)

Shouldn't this turn into:

if (error || !nmap)
goto out_free;

Otherwise looks ok to me.

--D

> error = 0;
> goto out_free;
> }
> diff --git a/fs/xfs/libxfs/xfs_da_btree.h b/fs/xfs/libxfs/xfs_da_btree.h
> index ed3b558a9c1a..64624d5717c9 100644
> --- a/fs/xfs/libxfs/xfs_da_btree.h
> +++ b/fs/xfs/libxfs/xfs_da_btree.h
> @@ -194,6 +194,9 @@ 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
>