Re: [PATCH v7 8/8] fs/xfs: Add dax dedupe support

[Shiyang Ruan]

On 2021/8/20 11:08, Dan Williams wrote:
> On Sun, Aug 15, 2021 at 11:05 PM Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx> wrote:
> > Introduce xfs_mmaplock_two_inodes_and_break_dax_layout() for dax files
> > who are going to be deduped.  After that, call compare range function
> > only when files are both DAX or not.
> >
> > Signed-off-by: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>
> > Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
> > ---
> >   fs/xfs/xfs_file.c    |  2 +-
> >   fs/xfs/xfs_inode.c   | 57 ++++++++++++++++++++++++++++++++++++++++++++
> >   fs/xfs/xfs_inode.h   |  1 +
> >   fs/xfs/xfs_reflink.c |  4 ++--
> >   4 files changed, 61 insertions(+), 3 deletions(-)
> [..]
> > diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
> > index 13e461cf2055..86c737c2baeb 100644
> > --- a/fs/xfs/xfs_reflink.c
> > +++ b/fs/xfs/xfs_reflink.c
> > @@ -1327,8 +1327,8 @@ xfs_reflink_remap_prep(
> >          if (XFS_IS_REALTIME_INODE(src) || XFS_IS_REALTIME_INODE(dest))
> >                  goto out_unlock;
> >
> > -       /* Don't share DAX file data for now. */
> > -       if (IS_DAX(inode_in) || IS_DAX(inode_out))
> > +       /* Don't share DAX file data with non-DAX file. */
> > +       if (IS_DAX(inode_in) != IS_DAX(inode_out))
> >                  goto out_unlock;
>
> What if you have 2 DAX inodes sharing data and one is flipped to
> non-DAX? Does that operation need to first go undo all sharing?

Yes, I think it is needed to unshare the extents when the DAX flags of 
the file is changed.  I'll look into it.


--
Thanks,
Ruan.