Re: [PATCH] xfs: dax: facilitate EXPERIMENTAL warning for dax=inode case

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

On Thu, Aug 26, 2021 at 12:30:12PM -0500, Bill O'Donnell wrote:
> When dax-mode was tri-stated by adding dax=inode case, the EXPERIMENTAL
> warning on mount was missed for the case. Add logic to handle the
> warning similar to that of the 'dax=always' case.
> 
> Signed-off-by: Bill O'Donnell <bodonnel@redhat.com>
> ---
>  fs/xfs/xfs_mount.h | 2 ++
>  fs/xfs/xfs_super.c | 8 +++++---
>  2 files changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
> index e091f3b3fa15..c9243a1b8d05 100644
> --- a/fs/xfs/xfs_mount.h
> +++ b/fs/xfs/xfs_mount.h
> @@ -277,6 +277,7 @@ typedef struct xfs_mount {
>  #define XFS_FEAT_NEEDSREPAIR	(1ULL << 25)	/* needs xfs_repair */
>  
>  /* Mount features */
> +#define XFS_FEAT_DAX_INODE	(1ULL << 47)	/* DAX enabled */
>  #define XFS_FEAT_NOATTR2	(1ULL << 48)	/* disable attr2 creation */
>  #define XFS_FEAT_NOALIGN	(1ULL << 49)	/* ignore alignment */
>  #define XFS_FEAT_ALLOCSIZE	(1ULL << 50)	/* user specified allocation size */
> @@ -359,6 +360,7 @@ __XFS_HAS_FEAT(swalloc, SWALLOC)
>  __XFS_HAS_FEAT(filestreams, FILESTREAMS)
>  __XFS_HAS_FEAT(dax_always, DAX_ALWAYS)
>  __XFS_HAS_FEAT(dax_never, DAX_NEVER)
> +__XFS_HAS_FEAT(dax_inode, DAX_INODE)
>  __XFS_HAS_FEAT(norecovery, NORECOVERY)
>  __XFS_HAS_FEAT(nouuid, NOUUID)
>  
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index 5e73ac78bf2f..f73f3687f0a8 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -84,15 +84,16 @@ xfs_mount_set_dax_mode(
>  {
>  	switch (mode) {
>  	case XFS_DAX_INODE:
> +		mp->m_features |= XFS_FEAT_DAX_INODE;
>  		mp->m_features &= ~(XFS_FEAT_DAX_ALWAYS | XFS_FEAT_DAX_NEVER);
>  		break;
>  	case XFS_DAX_ALWAYS:
>  		mp->m_features |= XFS_FEAT_DAX_ALWAYS;
> -		mp->m_features &= ~XFS_FEAT_DAX_NEVER;
> +		mp->m_features &= ~(XFS_FEAT_DAX_NEVER | XFS_FEAT_DAX_INODE);
>  		break;
>  	case XFS_DAX_NEVER:
>  		mp->m_features |= XFS_FEAT_DAX_NEVER;
> -		mp->m_features &= ~XFS_FEAT_DAX_ALWAYS;
> +		mp->m_features &= ~(XFS_FEAT_DAX_ALWAYS | XFS_FEAT_DAX_INODE);
>  		break;
>  	}
>  }
> @@ -189,6 +190,7 @@ xfs_fs_show_options(
>  		{ XFS_FEAT_LARGE_IOSIZE,	",largeio" },
>  		{ XFS_FEAT_DAX_ALWAYS,		",dax=always" },
>  		{ XFS_FEAT_DAX_NEVER,		",dax=never" },
> +		{ XFS_FEAT_DAX_INODE,		",dax=inode" },
>  		{ 0, NULL }
>  	};
>  	struct xfs_mount	*mp = XFS_M(root->d_sb);
> @@ -1584,7 +1586,7 @@ xfs_fs_fill_super(
>  	if (xfs_has_crc(mp))
>  		sb->s_flags |= SB_I_VERSION;
>  
> -	if (xfs_has_dax_always(mp)) {
> +	if (xfs_has_dax_always(mp) || xfs_has_dax_inode(mp)) {

Er... can't this be done without burning another feature bit by:

	if (xfs_has_dax_always(mp) || (!xfs_has_dax_always(mp) &&
				       !xfs_has_dax_never(mp))) {
		...
		xfs_warn(mp, "DAX IS EXPERIMENTAL");
	}

--D

>  		bool rtdev_is_dax = false, datadev_is_dax;
>  
>  		xfs_warn(mp,
> -- 
> 2.31.1
>