Re: [PATCH 1/2] xfs: don't catch dax+reflink inodes as corruption in verifier

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

On Thu, Dec 03, 2020 at 04:19:35PM -0600, Eric Sandeen wrote:
> On 12/3/20 3:44 PM, Darrick J. Wong wrote:
> > On Tue, Dec 01, 2020 at 01:16:09PM -0600, Eric Sandeen wrote:
> >> We don't yet support dax on reflinked files, but that is in the works.
> >>
> >> Further, having the flag set does not automatically mean that the inode
> >> is actually "in the CPU direct access state," which depends on several
> >> other conditions in addition to the flag being set.
> >>
> >> As such, we should not catch this as corruption in the verifier - simply
> >> not actually enabling S_DAX on reflinked files is enough for now.
> >>
> >> Fixes: 4f435ebe7d04 ("xfs: don't mix reflink and DAX mode for now")
> >> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
> >> ---
> >>  fs/xfs/libxfs/xfs_inode_buf.c | 4 ----
> >>  1 file changed, 4 deletions(-)
> >>
> >> diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
> >> index c667c63f2cb0..4d7410e49db4 100644
> >> --- a/fs/xfs/libxfs/xfs_inode_buf.c
> >> +++ b/fs/xfs/libxfs/xfs_inode_buf.c
> >> @@ -547,10 +547,6 @@ xfs_dinode_verify(
> >>  	if ((flags2 & XFS_DIFLAG2_REFLINK) && (flags & XFS_DIFLAG_REALTIME))
> >>  		return __this_address;
> >>  
> >> -	/* don't let reflink and dax mix */
> >> -	if ((flags2 & XFS_DIFLAG2_REFLINK) && (flags2 & XFS_DIFLAG2_DAX))
> >> -		return __this_address;
> > 
> > If we're going to let in inodes with the DAX and REFLINK iflags set,
> > doesn't that mean that xfs_inode_should_enable_dax needs to return false
> > if REFLINK is set?
> 
> I think it does already, no?
> 
> static bool
> xfs_inode_should_enable_dax(
>         struct xfs_inode *ip)
> {
>         if (!IS_ENABLED(CONFIG_FS_DAX))
>                 return false;
>         if (ip->i_mount->m_flags & XFS_MOUNT_DAX_NEVER)
>                 return false;
>         if (!xfs_inode_supports_dax(ip)) <------
>                 return false;
> 
> 
> ----> xfs_inode_supports_dax ---> 
> 
> static bool
> xfs_inode_supports_dax(
>         struct xfs_inode        *ip)
> {
>         struct xfs_mount        *mp = ip->i_mount;
> 
>         /* Only supported on regular files. */
>         if (!S_ISREG(VFS_I(ip)->i_mode))
>                 return false;
> 
>         /* Only supported on non-reflinked files. */
>         if (xfs_is_reflink_inode(ip))
>                 return false;
> 

DOH  yes it does,
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D