We need to call xfs_iext_get_ext for the previous extent to get a
valid pointer, and can't just do pointer arithmetics as they might
be in different pages.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Lachlan McIlroy <lmcilroy@redhat.com> Signed-off-by: Alex Elder <aelder@sgi.com>