my suggest

[suzj801]

Now, the features of RBDSR is almost complete. But the biggist trouble is vdi.migrate.
In migrate progress, the vdi delete may be conflict with snapshot delete. (the value of compose_vdi1 not same with snapshot-of in fact)。 And, unmap in ceph_plugin may be conflict with composing(dmsetup cannot remove dm-in-using)。
I think, after (parent)vdi.delete called, hide the rbd from SR instead of rename it。Is this method more effective?

[suzj801]

I have slove it . i will commit it later.