generic: test FIEMAP on extended attribute blocks

Make sure that FIEMAP produces some output when we add enough xattrs
to force the xattrs to be stored in an external block.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>
4 files changed