xfs_repair: check filesystem geometry before allowing upgrades

xfs_repair: check filesystem geometry before allowing upgrades

Currently, the two V5 feature upgrades permitted by xfs_repair do not
affect filesystem space usage, so we haven't needed to verify the
geometry.

However, this will change once we start to allow the sysadmin to add the
large extent count feature to existing filesystems.  Add all the
infrastructure we need to ensure that the log will still be large
enough, and the root inode will still be where we expect it to be after
the upgrade.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandan.babu@oracle.com>
[david: Recompute transaction reservation values; Exit with error if upgrade fails]
Signed-off-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>