Re: [PATCH] xfs: restore old agirotor behavior

[Dave Chinner <david@fromorbit.com>]

On Tue, Feb 21, 2023 at 09:29:00PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
> 
> Prior to the removal of xfs_ialloc_next_ag, we would increment the agi
> rotor and return the *old* value.  atomic_inc_return returns the new
> value, which causes mkfs to allocate the root directory in AG 1.  Put
> back the old behavior (at least for mkfs) by subtracting 1 here.
> 
> Fixes: 20a5eab49d35 ("xfs: convert xfs_ialloc_next_ag() to an atomic")
> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> ---
>  fs/xfs/libxfs/xfs_ialloc.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c
> index 65832c74e86c..550c6351e9b6 100644
> --- a/fs/xfs/libxfs/xfs_ialloc.c
> +++ b/fs/xfs/libxfs/xfs_ialloc.c
> @@ -1729,7 +1729,7 @@ xfs_dialloc(
>  	 * an AG has enough space for file creation.
>  	 */
>  	if (S_ISDIR(mode))
> -		start_agno = atomic_inc_return(&mp->m_agirotor) % mp->m_maxagi;
> +		start_agno = (atomic_inc_return(&mp->m_agirotor) - 1) % mp->m_maxagi;
>  	else {
>  		start_agno = XFS_INO_TO_AGNO(mp, parent);
>  		if (start_agno >= mp->m_maxagi)

Change is fine, but it pushes the code to 85 columns. If you clean
it up to:

	if (S_ISDIR(mode)) {
		start_agno = (atomic_inc_return(&mp->m_agirotor) - 1) %
				mp->m_maxagi;
	} else {
		....

Then you can add:

Reviewed-by: Dave Chinner <dchinner@redhat.com>

-- 
Dave Chinner
david@fromorbit.com