Re: [PATCH v6 14/16] xfs: Simplify xfs_attr_set_args

Darrick J. Wong
2020-01-21T23:31:53Z

On Sat, Jan 18, 2020 at 03:50:33PM -0700, Allison Collins wrote:
> Delayed attribute mechanics make frequent use of goto statements. We
> can use this to further simplify xfs_attr_set_args. In this patch we
> introduce one of the gotos now to help pre-simplify the routine. This
> will help make proceeding patches in this area easier to read.
>
> Signed-off-by: Allison Collins <allison.henderson@oracle.com>
> ---
> fs/xfs/libxfs/xfs_attr.c | 71 +++++++++++++++++++++++++-----------------------
> 1 file changed, 37 insertions(+), 34 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> index 453ea59..90e0b2d 100644
> --- a/fs/xfs/libxfs/xfs_attr.c
> +++ b/fs/xfs/libxfs/xfs_attr.c
> @@ -264,47 +264,50 @@ xfs_attr_set_args(
> int error, error2 = 0;
>
> /*
> - * If the attribute list is non-existent or a shortform list,
> - * upgrade it to a single-leaf-block attribute list.
> + * If the attribute list is non-existent or a shortform list, proceed to
> + * upgrade it to a single-leaf-block attribute list. Otherwise jump
> + * straight to leaf handling

We don't jump to "upgrade it to a single leaf block attr list" quite
that soon.

"If the attribute list is already in leaf format, jump straight to leaf
handling. Otherwise, try to add the attribute to the shortform list; if
there's no room then convert the list to leaf format and try again." ?

> */
> - if (dp->i_d.di_aformat == XFS_DINODE_FMT_LOCAL ||
> + if (!(dp->i_d.di_aformat == XFS_DINODE_FMT_LOCAL ||
> (dp->i_d.di_aformat == XFS_DINODE_FMT_EXTENTS &&
> - dp->i_d.di_anextents == 0)) {
> + dp->i_d.di_anextents == 0)))

Also... maybe this should just be a separate predicate?

static inline bool
xfs_attr_is_leaf_format(
struct xfs_inode *dp)
{
return dp->i_d.di_aformat == XFS_DINODE_FMT_EXTENTS &&
dp->i_d.di_anextents > 0;
}

if (xfs_attr_is_leaf_format(dp))
goto add_leaf;

> + goto sf_to_leaf;
>
> - /*
> - * Try to add the attr to the attribute list in the inode.
> - */
> - error = xfs_attr_try_sf_addname(dp, args);
> - if (error != -ENOSPC) {
> - error2 = xfs_trans_commit(args->trans);
> - args->trans = NULL;
> - return error ? error : error2;
> - }
> + /*
> + * Try to add the attr to the attribute list in the inode.
> + */
> + error = xfs_attr_try_sf_addname(dp, args);
> + if (error != -ENOSPC) {
> + error2 = xfs_trans_commit(args->trans);
> + args->trans = NULL;
> + return error ? error : error2;
> + }
>
> - /*
> - * It won't fit in the shortform, transform to a leaf block.
> - * GROT: another possible req'mt for a double-split btree op.
> - */
> - error = xfs_attr_shortform_to_leaf(args, &leaf_bp);
> - if (error)
> - return error;
> + /*
> + * It won't fit in the shortform, transform to a leaf block.
> + * GROT: another possible req'mt for a double-split btree op.
> + */
> + error = xfs_attr_shortform_to_leaf(args, &leaf_bp);
> + if (error)
> + return error;
>
> - /*
> - * Prevent the leaf buffer from being unlocked so that a
> - * concurrent AIL push cannot grab the half-baked leaf
> - * buffer and run into problems with the write verifier.
> - * Once we're done rolling the transaction we can release
> - * the hold and add the attr to the leaf.
> - */
> - xfs_trans_bhold(args->trans, leaf_bp);
> - error = xfs_defer_finish(&args->trans);
> - xfs_trans_bhold_release(args->trans, leaf_bp);
> - if (error) {
> - xfs_trans_brelse(args->trans, leaf_bp);
> - return error;
> - }
> + /*
> + * Prevent the leaf buffer from being unlocked so that a
> + * concurrent AIL push cannot grab the half-baked leaf
> + * buffer and run into problems with the write verifier.
> + * Once we're done rolling the transaction we can release
> + * the hold and add the attr to the leaf.
> + */
> + xfs_trans_bhold(args->trans, leaf_bp);
> + error = xfs_defer_finish(&args->trans);
> + xfs_trans_bhold_release(args->trans, leaf_bp);
> + if (error) {
> + xfs_trans_brelse(args->trans, leaf_bp);
> + return error;
> }
>
> +sf_to_leaf:

The attr list already has to be in list format by the time it gets here,
which means that the label name is misleading. How about "add_leaf" ?

--D

> if (xfs_bmap_one_block(dp, XFS_ATTR_FORK)) {
> error = xfs_attr_leaf_addname(args);
> if (error != -ENOSPC)
> --
> 2.7.4
>