Re: [PATCH v2] xfs_restore: detect rtinherit on destination

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

On Mon, Jun 17, 2019 at 03:09:15PM -0700, Sheena Artrip wrote:
> On Thu, Jun 6, 2019 at 3:37 PM Dave Chinner <david@fromorbit.com> wrote:
> >
> > On Thu, Jun 06, 2019 at 05:08:12PM -0500, Eric Sandeen wrote:
> > > On 6/6/19 4:50 PM, Dave Chinner wrote:
> > > > My take on this is that we need to decide which allocation policy to
> > > > use - the kernel policy or the dump file policy - in the different
> > > > situations. It's a simple, easy to document and understand solution.
> > > >
> > > > At minimum, if there's a mismatch between rtdev/non-rtdev between
> > > > dump and restore, then restore should not try to restore or clear rt
> > > > flags at all. i.e the rt flags in the dump image should be
> > > > considered invalid in this situation and masked out in the restore
> > > > process. This prevents errors from being reported during restore,
> > > > and it does "the right thing" according to how the user has
> > > > configured the destination directory. i.e.  if the destdir has the
> > > > rtinherit bit set and there's a rtdev present, the kernel policy
> > > > will cause all file data that is restored to be allocated on the
> > > > rtdev. Otherwise the kernel will place it (correctly) on the data
> > > > dev.
> > > >
> > > > In the case where both have rtdevs, but you want to restore to
> > > > ignore the dump file rtdev policy, we really only need to add a CLI
> > > > option to say "ignore rt flags" and that then allows the kernel
> > > > policy to dictate how the restored files are placed in the same way
> > > > that having a rtdev mismatch does.
> > > >
> > > > This is simple, consistent, fulfils the requirements and should have
> > > > no hidden surprises for users....
> > >
> > > Sounds reasonable.  So the CLI flag would say "ignore RT info in the
> > > dump, and write files according to the destination fs policy?"
> > > I think that makes sense.
> 
> Any suggested flag name/prefix for this? Last i checked all the single
> letters were taken up?

I suggest --preserve-xflags=<same letters as xfs_io lsattr command>

--D

> > *nod*
> >
> > > Now: do we need to do the same for all inheritable flags?  projid,
> > > extsize, etc?  I think we probably do.
> >
> > I disagree. These things are all supported on all destination
> > filesystems, unlike the rtdev. They are also things that can be
> > changed after the fact, unlike rtdev allocation policy. i.e. rtdev
> > has to be set /before/ restore, just about everything else can be
> > set or reset after the fact....
> > Cheers,
> >
> > Dave.
> > --
> > Dave Chinner
> > david@fromorbit.com