Add support for Pacific to RBD driver

[Jon Bernard]

When using ceph pacific, volume-from-image operations where both glance and cinder are configured to use RBD result in an exception when calling clone():

    rbd.InvalidArgument: [errno 22] RBD invalid argument (error creating clone)

    ERROR cinder.volume.manager Traceback (most recent call last):
    ERROR cinder.volume.manager File "/usr/local/lib/python3.9/site-packages/taskflow/engines/action_engine/executor.py", line 53, in _execute_task
    ERROR cinder.volume.manager result = task.execute(**arguments)
    ERROR cinder.volume.manager File "/opt/stack/cinder/cinder/volume/flows/manager/create_volume.py", line 1132, in execute
    ERROR cinder.volume.manager model_update = self._create_from_image(context,
    ERROR cinder.volume.manager File "/opt/stack/cinder/cinder/utils.py", line 638, in _wrapper
    ERROR cinder.volume.manager return r.call(f, *args, **kwargs)
    ERROR cinder.volume.manager File "/usr/local/lib/python3.9/site-packages/tenacity/__init__.py", line 411, in call
    ERROR cinder.volume.manager return self.__call__(*args, **kwargs)
    ERROR cinder.volume.manager File "/usr/local/lib/python3.9/site-packages/tenacity/__init__.py", line 423, in __call__
    ERROR cinder.volume.manager do = self.iter(retry_state=retry_state)
    ERROR cinder.volume.manager File "/usr/local/lib/python3.9/site-packages/tenacity/__init__.py", line 360, in iter
    ERROR cinder.volume.manager return fut.result()
    ERROR cinder.volume.manager File "/usr/lib64/python3.9/concurrent/futures/_base.py", line 438, in result
    ERROR cinder.volume.manager return self.__get_result()
    ERROR cinder.volume.manager File "/usr/lib64/python3.9/concurrent/futures/_base.py", line 390, in __get_result
    ERROR cinder.volume.manager raise self._exception
    ERROR cinder.volume.manager File "/usr/local/lib/python3.9/site-packages/tenacity/__init__.py", line 426, in __call__
    ERROR cinder.volume.manager result = fn(*args, **kwargs)
    ERROR cinder.volume.manager File "/opt/stack/cinder/cinder/volume/flows/manager/create_volume.py", line 998, in _create_from_image
    ERROR cinder.volume.manager model_update, cloned = self.driver.clone_image(context,
    ERROR cinder.volume.manager File "/opt/stack/cinder/cinder/volume/drivers/rbd.py", line 1571, in clone_image
    ERROR cinder.volume.manager volume_update = self._clone(volume, pool, image, snapshot)
    ERROR cinder.volume.manager File "/opt/stack/cinder/cinder/volume/drivers/rbd.py", line 1023, in _clone
    ERROR cinder.volume.manager self.RBDProxy().clone(src_client.ioctx,
    ERROR cinder.volume.manager File "/usr/local/lib/python3.9/site-packages/eventlet/tpool.py", line 190, in doit
    ERROR cinder.volume.manager result = proxy_call(self._autowrap, f, *args, **kwargs)
    ERROR cinder.volume.manager File "/usr/local/lib/python3.9/site-packages/eventlet/tpool.py", line 148, in proxy_call
    ERROR cinder.volume.manager rv = execute(f, *args, **kwargs)
    ERROR cinder.volume.manager File "/usr/local/lib/python3.9/site-packages/eventlet/tpool.py", line 129, in execute
    ERROR cinder.volume.manager six.reraise(c, e, tb)
    ERROR cinder.volume.manager File "/usr/local/lib/python3.9/site-packages/six.py", line 719, in reraise
    ERROR cinder.volume.manager raise value
    ERROR cinder.volume.manager File "/usr/local/lib/python3.9/site-packages/eventlet/tpool.py", line 83, in tworker
    ERROR cinder.volume.manager rv = meth(*args, **kwargs)
    ERROR cinder.volume.manager File "rbd.pyx", line 698, in rbd.RBD.clone
    ERROR cinder.volume.manager rbd.InvalidArgument: [errno 22] RBD invalid argument (error creating clone)
    ERROR cinder.volume.manager

In Pacific a check was added to make sure during a clone operation that the child's strip unit was not less than that of its parent. Failing this condition returns -EINVAL, which is then raised by python-rbd as an exception. This maps to the 'order' argument in clone(), where order is log base 2 of the strip unit. Ceph's default is 4 megabytes. The reason we're seeing EINVAL exceptions in the Pacific CI is that: when Openstack is configured to use Ceph for both cinder and glance, volume-from-image tests fail because Glance's default stripe unit is 8 (distinctly larger than Cinder's 4). This results in an order calculation of 22, which is invalid for clone() (too small).

I see two possible solutions and have proposed patches:

1. Increase Cinder's default chunk size to match Glance's. I think this makes sense for both consistency and performance.

2. When doing a clone(), consider the configured chunk size /and/ the strip unit of the parent volume and choose the higher value.

Either of these approaches prevent the failures we're seeing, I think they are both useful individually as well.

[Sofia Enriquez (lsofia-enriquez)]

- https://review.opendev.org/c/openstack/cinder/+/786260
- https://review.opendev.org/c/openstack/cinder/+/786266

[Boris Lukashev (rageltman)]

Cinder deals with a lot more small IO requests than Glance, so doubling the chunk size might not be ideal. Would conversion of volumes be required in an upgrade scenario? #2 seems like the more compatible approach given that Kolla-Ansible doesn't manage Ceph these days, and users are going to bring all sorts of Ceph backends into the mix on their own (we're using Canonical's for instance).