Re: [PATCH] xfs: fail dax mount if reflink is enabled on a partition

Darrick J. Wong
2022-07-29T04:54:16Z

On Fri, Jul 29, 2022 at 03:55:24AM +0000, ruansy.fnst@fujitsu.com wrote:
>
>
> 在 2022/7/22 0:16, Darrick J. Wong 写道:
> > On Thu, Jul 21, 2022 at 02:06:10PM +0000, ruansy.fnst@fujitsu.com wrote:
> >> 在 2022/7/1 8:31, Darrick J. Wong 写道:
> >>> On Thu, Jun 09, 2022 at 10:34:35PM +0800, Shiyang Ruan wrote:
> >>>> Failure notification is not supported on partitions. So, when we mount
> >>>> a reflink enabled xfs on a partition with dax option, let it fail with
> >>>> -EINVAL code.
> >>>>
> >>>> Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
> >>>
> >>> Looks good to me, though I think this patch applies to ... wherever all
> >>> those rmap+reflink+dax patches went. I think that's akpm's tree, right?
> >>>
> >>> Ideally this would go in through there to keep the pieces together, but
> >>> I don't mind tossing this in at the end of the 5.20 merge window if akpm
> >>> is unwilling.
> >>
> >> BTW, since these patches (dax&reflink&rmap + THIS + pmem-unbind) are
> >> waiting to be merged, is it time to think about "removing the
> >> experimental tag" again? :)
> >
> > It's probably time to take up that question again.
> >
> > Yesterday I tried running generic/470 (aka the MAP_SYNC test) and it
> > didn't succeed because it sets up dmlogwrites atop dmthinp atop pmem,
> > and at least one of those dm layers no longer allows fsdax pass-through,
> > so XFS silently turned mount -o dax into -o dax=never. :(
>
> Hi Darrick,
>
> I tried generic/470 but it didn't run:
> [not run] Cannot use thin-pool devices on DAX capable block devices.
>
> Did you modify the _require_dm_target() in common/rc? I added thin-pool
> to not to check dax capability:
>
> case $target in
> stripe|linear|log-writes|thin-pool) # add thin-pool here
> ;;
>
> then the case finally ran and it silently turned off dax as you said.
>
> Are the steps for reproduction correct? If so, I will continue to
> investigate this problem.

Ah, yes, I did add thin-pool to that case statement. Sorry I forgot to
mention that. I suspect that the removal of dm support for pmem is
going to force us to completely redesign this test. I can't really
think of how, though, since there's no good way that I know of to gain a
point-in-time snapshot of a pmem device.

--D

>
> --
> Thanks,
> Ruan.
>
>
>
> >
> > I'm not sure how to fix that...
> >
> > --D
> >
> >>
> >> --
> >> Thanks,
> >> Ruan.
> >>
> >>>
> >>> Reviewed-by: Darrick J. Wong <djwong@kernel.org>
> >>>
> >>> --D
> >>>
> >>>> ---
> >>>> fs/xfs/xfs_super.c | 6 ++++--
> >>>> 1 file changed, 4 insertions(+), 2 deletions(-)
> >>>>
> >>>> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> >>>> index 8495ef076ffc..a3c221841fa6 100644
> >>>> --- a/fs/xfs/xfs_super.c
> >>>> +++ b/fs/xfs/xfs_super.c
> >>>> @@ -348,8 +348,10 @@ xfs_setup_dax_always(
> >>>> goto disable_dax;
> >>>> }
> >>>>
> >>>> - if (xfs_has_reflink(mp)) {
> >>>> - xfs_alert(mp, "DAX and reflink cannot be used together!");
> >>>> + if (xfs_has_reflink(mp) &&
> >>>> + bdev_is_partition(mp->m_ddev_targp->bt_bdev)) {
> >>>> + xfs_alert(mp,
> >>>> + "DAX and reflink cannot work with multi-partitions!");
> >>>> return -EINVAL;
> >>>> }
> >>>>
> >>>> --
> >>>> 2.36.1
> >>>>
> >>>>
> >>>>