Re: [PATCH v4 11/12] xfs: Update atomic write max size

[Carlos Maiolino]

Hi John.

On Mon, Mar 03, 2025 at 05:11:19PM +0000, John Garry wrote:
> Now that CoW-based atomic writes are supported, update the max size of an
> atomic write.
> 
> For simplicity, limit at the max of what the mounted bdev can support in
> terms of atomic write limits. Maybe in future we will have a better way
> to advertise this optimised limit.
> 
> In addition, the max atomic write size needs to be aligned to the agsize.
> Limit the size of atomic writes to the greatest power-of-two factor of the
> agsize so that allocations for an atomic write will always be aligned
> compatibly with the alignment requirements of the storage.
> 
> For RT inode, just limit to 1x block, even though larger can be supported
> in future.
> 
> Reviewed-by: "Darrick J. Wong" <djwong@xxxxxxxxxx>
> Signed-off-by: John Garry <john.g.garry@xxxxxxxxxx>
> ---
>  fs/xfs/xfs_iops.c  | 13 ++++++++++++-
>  fs/xfs/xfs_mount.c | 28 ++++++++++++++++++++++++++++
>  fs/xfs/xfs_mount.h |  1 +
>  3 files changed, 41 insertions(+), 1 deletion(-)
> 

> diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
> index fbed172d6770..bc96b8214173 100644
> --- a/fs/xfs/xfs_mount.h
> +++ b/fs/xfs/xfs_mount.h
> @@ -198,6 +198,7 @@ typedef struct xfs_mount {
>  	bool			m_fail_unmount;
>  	bool			m_finobt_nores; /* no per-AG finobt resv. */
>  	bool			m_update_sb;	/* sb needs update in mount */
> +	xfs_extlen_t		awu_max;	/* data device max atomic write */

Could you please rename this to something else? All fields within xfs_mount
follows the same pattern m_<name>. Perhaps m_awu_max?

I was going to send a patch replacing it once I had this merged, but giving
Dave's new comments, and the conflicts with zoned devices, you'll need to send a
V5, so, please include this change if nobody else has any objections on keeping
the xfs_mount naming convention.

Carlos.

> 
>  	/*
>  	 * Bitsets of per-fs metadata that have been checked and/or are sick.
> --
> 2.31.1
>