Rewrite the function using xfs_iext_lookup_extent and xfs_iext_get_extent,
and massage the flow into something easily understandable.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NDave Chinner <david@fromorbit.com>