Re: [PATCH 2/2] xfs: ignore extent size hints for always COW inodes

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Fri, Oct 11, 2019 at 06:03:16AM -0700, Christoph Hellwig wrote:
> There is no point in applying extent size hints for always COW inodes,
> as we would just have to COW any extra allocation beyond the data
> actually written.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Looks ok, I guess?

By the way, what's the plan for always_cow inodes, seeing as it's still
only a debugging feature?

Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

> ---
>  fs/xfs/xfs_inode.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> index 18f4b262e61c..2e94deb4610a 100644
> --- a/fs/xfs/xfs_inode.c
> +++ b/fs/xfs/xfs_inode.c
> @@ -55,6 +55,12 @@ xfs_extlen_t
>  xfs_get_extsz_hint(
>  	struct xfs_inode	*ip)
>  {
> +	/*
> +	 * No point in aligning allocations if we need to COW to actually
> +	 * write to them.
> +	 */
> +	if (xfs_is_always_cow_inode(ip))
> +		return 0;
>  	if ((ip->i_d.di_flags & XFS_DIFLAG_EXTSIZE) && ip->i_d.di_extsize)
>  		return ip->i_d.di_extsize;
>  	if (XFS_IS_REALTIME_INODE(ip))
> -- 
> 2.20.1
>