Re: [PATCH 12/13] xfs: stop the steal (of data blocks for RT indirect blocks)

["Darrick J. Wong" <djwong@kernel.org>]

On Wed, Mar 27, 2024 at 12:03:17PM +0100, Christoph Hellwig wrote:
> When xfs_bmap_del_extent_delay has to split an indirect block it tries
> to steal blocks from the the part that gets unmapped to increase the
> indirect block reservation that now needs to cover for two extents
> instead of one.
> 
> This works perfectly fine on the data device, where the data and
> indirect blocks come from the same pool.  It has no chance of working
> when the inode sits on the RT device.  To support re-enabling delalloc
> for inodes on the RT device, make this behavior conditional on not
> beeing for rt extents.

  being

> Note that split of delalloc extents should only happen on writeback
> failure, as for other kinds of hole punching we first write back all
> data and thus convert the delalloc reservations covering the hole to
> a real allocation.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

With that one spelling fix,
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
>  fs/xfs/libxfs/xfs_bmap.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index 9d0b7caa9a036c..ef34738fb0fedd 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -4981,9 +4981,14 @@ xfs_bmap_del_extent_delay(
>  		/*
>  		 * Steal as many blocks as we can to try and satisfy the worst
>  		 * case indlen for both new extents.
> +		 *
> +		 * However, we can't just steal reservations from the data
> +		 * blocks if this is an RT inodes as the data and metadata
> +		 * blocks come from different pools.  We'll have to live with
> +		 * under-filled indirect reservation in this case.
>  		 */
>  		da_new = got_indlen + new_indlen;
> -		if (da_new > da_old) {
> +		if (da_new > da_old && !isrt) {
>  			stolen = XFS_FILBLKS_MIN(da_new - da_old,
>  						 del->br_blockcount);
>  			da_old += stolen;
> -- 
> 2.39.2
> 
>