[Bug 1969643] Re: RBD: Unable to delete a volume which has snapshot/volume children

[Chengen Du]

Debdiff for Jammy

** Also affects: cinder (Ubuntu)
   Importance: Undecided
       Status: New

** Also affects: cinder (Ubuntu Jammy)
   Importance: Undecided
       Status: New

** Description changed:

- With the RBD driver, in this scenario:
+ [Impact]
+ Deleting a volume will fail if it has snapshot or volume children, resulting in an ImageBusy error.
  
- - Create volume A
- - Create snapshot B of volume A
- - Create cloned volume C from snapshot B
- - Delete snapshot B
- - Delete volume A
+ [Fix]
+ Upstream has a patch that uses RBD flatten operations to break dependencies between volumes and snapshots, reducing failures when using RBD volume clones and snapshots.
  
- Deleting volume A will fail with an ImageBusy error.
+ commit 1a675c9aa178c6d9c6ed10fd98f086c46d350d3f
+ Author:     Eric Harney <eharney at redhat.com>
+ CommitDate: Fri Dec 1 10:17:05 2023 -0500
+ 
+     RBD: Flattening of child volumes during deletion
+ 
+ [Test Plan]
+ 1. Prepare an OpenStack environment with cinder-ceph
+ 2. Create a volume named "vol"
+ openstack volume create --image jammy --size 10 vol
+ 3. Create a snapshot of the volume "vol"
+ openstack volume snapshot create --volume vol vol-snap
+ 4. Create a volume named "vol-copy" from the snapshot
+ openstack volume create --snapshot vol-snap vol-copy
+ 5. Delete the snapshot and then delete the volume "vol"
+ openstack volume snapshot delete vol-snap
+ openstack volume delete vol
+ 6. Confirm that the volume "vol" is successfully deleted
+ openstack volume list
+ 
+ [Where problems could occur]
+ The patch primarily modifies the workflow for volume deletion when using RBD as the backend and adds a retry mechanism for unprotecting snapshots during snapshot deletion.
+ If the patch has any undiscovered issues, it will only affect volume deletion. Other functionalities or non-RBD backends will not be impacted.

** Patch added: "lp1969643-cinder-jammy.debdiff"
   https://bugs.launchpad.net/ubuntu/+source/cinder/+bug/1969643/+attachment/5784118/+files/lp1969643-cinder-jammy.debdiff

** Changed in: cinder (Ubuntu Jammy)
       Status: New => In Progress

** Changed in: cinder (Ubuntu Jammy)
     Assignee: (unassigned) => Chengen Du (chengendu)

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https://bugs.launchpad.net/bugs/1969643

Title:
  RBD: Unable to delete a volume which has snapshot/volume children

Status in Cinder:
  Fix Released
Status in cinder package in Ubuntu:
  New
Status in cinder source package in Jammy:
  In Progress

Bug description:
  [Impact]
  Deleting a volume will fail if it has snapshot or volume children, resulting in an ImageBusy error.

  [Fix]
  Upstream has a patch that uses RBD flatten operations to break dependencies between volumes and snapshots, reducing failures when using RBD volume clones and snapshots.

  commit 1a675c9aa178c6d9c6ed10fd98f086c46d350d3f
  Author:     Eric Harney <eharney at redhat.com>
  CommitDate: Fri Dec 1 10:17:05 2023 -0500

      RBD: Flattening of child volumes during deletion

  [Test Plan]
  1. Prepare an OpenStack environment with cinder-ceph
  2. Create a volume named "vol"
  openstack volume create --image jammy --size 10 vol
  3. Create a snapshot of the volume "vol"
  openstack volume snapshot create --volume vol vol-snap
  4. Create a volume named "vol-copy" from the snapshot
  openstack volume create --snapshot vol-snap vol-copy
  5. Delete the snapshot and then delete the volume "vol"
  openstack volume snapshot delete vol-snap
  openstack volume delete vol
  6. Confirm that the volume "vol" is successfully deleted
  openstack volume list

  [Where problems could occur]
  The patch primarily modifies the workflow for volume deletion when using RBD as the backend and adds a retry mechanism for unprotecting snapshots during snapshot deletion.
  If the patch has any undiscovered issues, it will only affect volume deletion. Other functionalities or non-RBD backends will not be impacted.

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