Pull Ceph fixes from Sage Weil:
 "These paches from Ilya finally squash a race condition with layered
  images that he's been chasing for a while"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client:
  rbd: drop parent_ref in rbd_dev_unprobe() unconditionally
  rbd: fix rbd_dev_parent_get() when parent_overlap == 0