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

[Mauricio Faria de Oliveira]

Hi Chengen,

Thanks for your work on this bug / fix / SRU template!

Some process review notes:

In the future, please update the bug tasks for the newer/devel releases
as well.

In this case, Mantic not marked as Won't Fix possibly would require you
an extra round-trip during the review with the SRU team later, to
clarify why it is affected but not being fixed.

I think this is because Mantic will EOL in less than a month, thus not worth fixing.
This type of information is helpful to add in the SRU template's Other Info section [1].

Please also see See SRU -> General Requirements > Newer Releases >
Exceptions > "2." [2]

$ ubuntu-distro-info --series=mantic --days=eol
29

$ rmadison -a source cinder | grep -e mantic -e noble -e oracular
 cinder | 2:23.0.0-0ubuntu1                            | mantic            | source
 cinder | 2:23.0.0-0ubuntu1.2                          | mantic-updates    | source
 cinder | 2:24.0.0-0ubuntu1                            | noble             | source
 cinder | 2:24.0.0-0ubuntu1                            | oracular          | source
 cinder | 2:24.0.0-0ubuntu2                            | oracular-proposed | source

$ pull-lp-source cinder noble
Found cinder 2:23.0.0-0ubuntu1.2 in mantic
...
$ grep -A2 'deployments must either' cinder-23.0.0/releasenotes/notes/rbd-flatten-child-volumes-4cb0b7fcf3a1df5e.yaml
grep: cinder-23.0.0/releasenotes/notes/rbd-flatten-child-volumes-4cb0b7fcf3a1df5e.yaml: No such file or directory

$ pull-lp-source cinder noble
Found cinder 2:24.0.0-0ubuntu1 in noble
...
$ grep -A2 'deployments must either' cinder-24.0.0/releasenotes/notes/rbd-flatten-child-volumes-4cb0b7fcf3a1df5e.yaml
    Therefore, deployments must either a) enable scheduled RBD trash purging on
    the RBD backend or b) enable the Cinder RBD driver's enable_deferred_deletion
    option to have Cinder purge the RBD trash.

[1] https://wiki.ubuntu.com/StableReleaseUpdates#SRU_Bug_Template
[2] https://wiki.ubuntu.com/StableReleaseUpdates#Newer_Releases

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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:
  Fix Released
Status in cinder source package in Jammy:
  In Progress
Status in cinder source package in Mantic:
  Won't Fix
Status in cinder source package in Noble:
  Fix Released
Status in cinder source package in Oracular:
  Fix Released

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
  # ^ This would fail with ImageBusy previously (see patch's "For example")
  openstack volume delete vol
  # ^ This would possibly fail previously (see patch's step "4.")
  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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