Re: [PATCH] xfs: speed up parent pointer operations

[Christoph Hellwig <hch@infradead.org>]

On Fri, Dec 19, 2025 at 07:41:54AM -0800, Darrick J. Wong wrote:
> Now parent pointers only increase the system time by 8% for creation and
> 19% for deletion.  Wall time increases by 5% and 9%.

Nice!

> @@ -202,6 +203,16 @@ xfs_parent_addname(
>  	xfs_inode_to_parent_rec(&ppargs->rec, dp);
>  	xfs_parent_da_args_init(&ppargs->args, tp, &ppargs->rec, child,
>  			child->i_ino, parent_name);
> +
> +	if (xfs_inode_has_attr_fork(child) &&
> +	    xfs_attr_is_shortform(child)) {
> +		ppargs->args.op_flags |= XFS_DA_OP_ADDNAME;
> +
> +		error = xfs_attr_try_sf_addname(&ppargs->args);
> +		if (error != -ENOSPC)
> +			return error;
> +	}
> +
>  	xfs_attr_defer_add(&ppargs->args, XFS_ATTR_DEFER_SET);

We should be able to do this for all attrs, not just parent pointers,
right?  It might be nice to just do this for set and remove in
xfs_attr_defer_add and have it handle all attr operations.

> +	if (xfs_attr_is_shortform(child)) {
> +		ppargs->args.op_flags |= XFS_DA_OP_ADDNAME | XFS_DA_OP_REPLACE;
> +
> +		error = xfs_attr_sf_removename(&ppargs->args);
> +		if (error)
> +			return error;
> +
> +		xfs_parent_da_args_init(&ppargs->args, tp, &ppargs->new_rec,
> +				child, child->i_ino, new_name);
> +		ppargs->args.op_flags |= XFS_DA_OP_ADDNAME;
> +
> +		error = xfs_attr_try_sf_addname(&ppargs->args);
> +		if (error == -ENOSPC) {
> +			xfs_attr_defer_add(&ppargs->args, XFS_ATTR_DEFER_SET);
> +			return 0;
> +		}

And for replace we should be able to optimize this even further
by adding a new xfs_attr_sf_replacename that just checks if the new
version would fit, and then memmove everything behind the changed
attr and update it in place.  This should improve the operation a lot
more.