Re: XFS over device mapper dm-thin device

[Dave Chinner <david@fromorbit.com>]

On Thu, Feb 08, 2018 at 08:31:21AM -0600, Eric Sandeen wrote:
> 
> 
> On 2/8/18 2:25 AM, Dave Chinner wrote:
> > 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
> 
> And that's what I /meant/, sorry for the lack of specificity ;)

So we are all happy to burn a log incompat bit for this? 

/me wonders how many one liners we can string this out into :)

-Dave.
-- 
Dave Chinner
david@fromorbit.com