After creating a volume from a snapshot, there is usually a problem with the inability to delete the snapshot, since the volume refers to it. To solve this problem, it is necessary to perform the operation of flattening the volume from a snapshot in Ceph.
(Since there is no such API in the Cinder driver, despite the fact that flattening is called in some cases)
volume_id - volume ID in OpenStack
pool_name - the Ceph pool name, in which the volume is located.
The command to untie (run on a machine that has access to the Ceph command-line API):
# rbd flatten <pool_name>/volume-<volume_id>
# rbd flatten -p <pool_name> volume-<volume_id>
# rbd flatten controller-volumes/volume-95e7e2ba-9d4a-47d4-aba9-