[PATCH, RFC] xfs_repair: allow filesystems with a single AG

[Eric Sandeen]

Christoph Hellwig wrote:
> Currently xfs_repair bails out on a filesystem with just a single AG.
> But that's a perfectly valid configureation, so we should allow it.
> 
> Skip the geomery validation because we simply can't do it if we don't
> have a secondary SB, and make sure to take the internal log into account
> when guestimating the first inode cluster.
> 
> I'll also cook up a testcase for repair on single AG filesystems.

While I think we should certainly allow this, what's the worst-case
scenario for a corrupted superblock when we can't validate it and
continue with repair?

I wonder if something like

# xfs_repair --allow-single-sb

should be required, with some man page docs suggesting a run with -n
first etc to be sure that garbled geometry doesn't trash the whole thing...?

-Eric