v9.0.4
~~~~~

* The return code for librbd's rbd_aio_read and Image::aio_read API methods no
  longer returns the number of bytes read upon success.  Instead, it returns 0
  upon success and a negative value upon failure.

* 'ceph scrub', 'ceph compact' and 'ceph sync force are now DEPRECATED.  Users
  should instead use 'ceph mon scrub', 'ceph mon compact' and
  'ceph mon sync force'.

* 'ceph mon_metadata' should now be used as 'ceph mon metadata'. There is no
  need to deprecate this command (same major release since it was first
  introduced).