Re: [PATCH] xfs: remove experimental tag for reflinks

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

On Wed, Nov 15, 2017 at 08:14:33AM +0200, Amir Goldstein wrote:
> On Wed, Nov 15, 2017 at 3:10 AM, Darrick J. Wong
> <darrick.wong@oracle.com> wrote:
> > On Wed, Aug 30, 2017 at 04:54:00PM +0200, Christoph Hellwig wrote:
> >> But reject reflink + DAX file systems for now until the code to
> >> support reflinks on DAX is actually implemented.
> >>
> >> Signed-off-by: Christoph Hellwig <hch@lst.de>
> >> ---
> >>  fs/xfs/xfs_super.c | 8 +++-----
> >>  1 file changed, 3 insertions(+), 5 deletions(-)
> >>
> >> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> >> index 38aaacdbb8b3..92521032468e 100644
> >> --- a/fs/xfs/xfs_super.c
> >> +++ b/fs/xfs/xfs_super.c
> >> @@ -1634,7 +1634,9 @@ xfs_fs_fill_super(
> >>               }
> >>               if (xfs_sb_version_hasreflink(&mp->m_sb))
> >>                       xfs_alert(mp,
> >> -             "DAX and reflink have not been tested together!");
> >> +             "DAX and reflink can not be used together!");
> >> +                     error = -EINVAL;
> >> +                     goto out_filestream_unmount;
> >>       }
> >>
> >>       if (xfs_sb_version_hasrmapbt(&mp->m_sb)) {
> >> @@ -1648,10 +1650,6 @@ xfs_fs_fill_super(
> >>       "EXPERIMENTAL reverse mapping btree feature enabled. Use at your own risk!");
> >>       }
> >>
> >> -     if (xfs_sb_version_hasreflink(&mp->m_sb))
> >> -             xfs_alert(mp,
> >> -     "EXPERIMENTAL reflink feature enabled. Use at your own risk!");
> >
> > Ok, now that the incore extent map rework has landed upstream, can we
> > please get everyone's QA to stress the reflink/cow code vigorously
> > during this release cycle so that we can re-consider this patch for
> > 4.16?
> >
> > (And if you're particularly mean, force cowextsize = 1fsb to age the
> > filesystem prematurely?)
> >
> > Right now I think the only problem I know about is that log recovery bug
> > where the defer ops of replayed defer ops get logged in the wrong order,
> > but that's it.
> >
> 
> Last time you wrote about this bug you had a "hard question" about transaction
> reservation for the solution and said your're going to go have a think about it:
> https://marc.info/?l=linux-xfs&m=150766311924170&w=2
> Did you come to any conclusions?
> That sounds like one of those nasty CoW corner cases, so I'd be happy to know
> there is at least a well thought design for a solution - if not a fix.

Sorry I let myself get distracted/stressed with the merge window;
hopefully the patch I sent out will address that problem?

> Practically, I would love if that bug could be solved soon so that we can all
> start running generic/503 for more than a few iterations to stress
> test reflink/cow
> with power failure. Success on this front could be a big upside before
> turning off
> EXPERIMENTAL.

Indeed!  What is the status of those tests, anyway?  Are they in xfstests?

--D

> Thanks,
> Amir.
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