Description of problem:

If you want to delete a snapshot having a rw clone you can't and
cinder doesn't give any information of way, you have to check the
logs to find what is going on, because cinder doesn't keep any
track of it.

Example:


(overcloud) [stack@undercloud-0 ~]$ cinder list 
                                    
| da53019a-346e-4115-960d-0c791c9d84a7 | available | 03XXXXXX-vol          | 1    | tripleo     | false    |                                      


(overcloud) [stack@undercloud-0 ~]$ cinder snapshot-list 

| e499f160-d080-4077-bb8e-4ab41ba338aa | da53019a-346e-4115-960d-0c791c9d84a7 | available | 03XXXXXX-vol-snap | 1


I want to delete 03XXXXXX-vol-snap

$ openstack volume snapshot delete e499f160-d080-4077-bb8e-4ab41ba338aa
$ echo $?
0
$ openstack volume snapshot show  e499f160-d080-4077-bb8e-4ab41ba338aa
+--------------------------------------------+--------------------------------------+
| Field                                      | Value                                |
+--------------------------------------------+--------------------------------------+
| created_at                                 | 2022-02-03T09:18:17.000000           |
| description                                | None                                 |
| id                                         | e499f160-d080-4077-bb8e-4ab41ba338aa |
| name                                       | 03XXXXXX-vol-snap                    |
| os-extended-snapshot-attributes:progress   | 100%                                 |
| os-extended-snapshot-attributes:project_id | d7ad92b9537c4cf5966ad66012005ff7     |
| properties                                 |                                      |
| size                                       | 1                                    |
| status                                     | available                            |
| updated_at                                 | 2022-02-03T11:37:43.000000           |
| volume_id                                  | da53019a-346e-4115-960d-0c791c9d84a7 |
+--------------------------------------------+--------------------------------------+
There is no information about the dependent clones


we are forced to check the logs:

cinder-volume.log:
2022-02-03 11:37:43.040 59 INFO cinder.volume.drivers.rbd [req-02127f65-498a-405b-b27d-21bb13b9fe0b 92452da4acce4c49b3011ec1ad71d544 d7ad92b9537c4cf5966ad66012005ff7 - default default] Image volumes/volume-7051625d-2134-41fc-a398-c3c862e09a90 is dependent on the snapshot snapshot-e499f160-d080-4077-bb8e-4ab41ba338aa.
2022-02-03 11:37:43.053 59 ERROR cinder.volume.manager [req-02127f65-498a-405b-b27d-21bb13b9fe0b 92452da4acce4c49b3011ec1ad71d544 d7ad92b9537c4cf5966ad66012005ff7 - default default] Delete snapshot failed, due to snapshot busy.: cinder.exception.SnapshotIsBusy: deleting snapshot snapshot-e499f160-d080-4077-bb8e-4ab41ba338aa that has dependent volumes

Or check ceph:

# rbd children volumes/volume-da53019a-346e-4115-960d-0c791c9d84a7@snapshot-e499f160-d080-4077-bb8e-4ab41ba338aa
volumes/volume-7051625d-2134-41fc-a398-c3c862e09a90

Suggestions:
- keep track of the volumes from snapshots
- ability to flatten volumes from snapshots so they become independent


Version-Release number of selected component (if applicable):


How reproducible:
OSP 13
OSP 16.1

Steps to Reproduce:
1. Create a volume, a snapshot fo the volume and a volume from the snapshot
2.
3.

Actual results:
No way to find the volume created from the snapshot if we want to delete the snapshot