ceph/ceph — pull request #1644 by cmgitdream (2014-04-11 01:47:05+00:00)
Title: librbd: copy-on-read for clones

Add the feature copy-on-read in librbd.
Currently read the object not in clone, will request it from parent, but not keep it in clone,
so the next time will read the object from parent again.
This feature write the object in clone after read the object.