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

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Date:   Thu, 21 Jul 2022 09:16:08 -0700
From:   "Darrick J. Wong" <djwong@...nel.org>
To:     "ruansy.fnst@...itsu.com" <ruansy.fnst@...itsu.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-xfs@...r.kernel.org" <linux-xfs@...r.kernel.org>,
        "nvdimm@...ts.linux.dev" <nvdimm@...ts.linux.dev>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "david@...morbit.com" <david@...morbit.com>,
        "hch@...radead.org" <hch@...radead.org>
Subject: Re: [PATCH] xfs: fail dax mount if reflink is enabled on a partition

On Thu, Jul 21, 2022 at 02:06:10PM +0000, ruansy.fnst@...itsu.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@...itsu.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. :(

I'm not sure how to fix that...

--D

> 
> --
> Thanks,
> Ruan.
> 
> > 
> > Reviewed-by: Darrick J. Wong <djwong@...nel.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
> >>
> >>
> >>