Since the kernel doesn't currently support the realtime rmapbt,
don't allow such filesystems to be mounted.  Support will appear
in a future release.
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NCarlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NDave Chinner <david@fromorbit.com>