Re: XFS over device mapper dm-thin device

[Dave Chinner <david@fromorbit.com>]

On Wed, Feb 07, 2018 at 09:53:40PM -0800, Darrick J. Wong wrote:
> On Wed, Feb 07, 2018 at 08:35:12PM -0600, Eric Sandeen wrote:
> > 
> > 
> > On 2/6/18 12:11 AM, Dave Chinner wrote:
> > > On Mon, Feb 05, 2018 at 04:37:22PM -0600, Eric Sandeen wrote:
> > >>
> > >>
> > >> On 2/5/18 4:36 PM, Dave Chinner wrote:
> > >>>> In retrospect I think we (I) should have left the "metadata" uuid as
> > >>>> the one to match the log, not the user-facing one.
> > >>> I suspect we can just change the log recovery code to accept either
> > >>> sb_uuid or sb_metauuid if the metauuid feature bit is set and
> > >>> change xfs_db to not rewrite the log when metauuid is used....
> > >>>
> > >>> Cheers,
> > >>
> > >> That was my first thought, but then newer userspace UUID changes
> > >> won't be mountable on older kernels.   I don't think we can just
> > >> change it w/o some thought re: compatibility...
> > > 
> > > So maybe we should use a log incompat bit and provide an alternative
> > > command for the old way of changing the UUID in the log?
> > 
> > Sure, if we're happy burning an incompat bit for this, sounds good.
> 
> Or a log incompat bit?

That's what I suggested :P

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com