Volume is not unreserved when shelved_offloaded volume attach fails

[Matt Riedemann]

This code attaches a volume to a shelved offloaded instance:

https://github.com/openstack/nova/blob/b3d58ed718db91015582cf759a7c8af1874ef093/nova/compute/api.py#L3416

But it doesn't unreserve the volume if that fails in the exception block. This could happen if the os-attach call to cinder failed. And if that happens, then the volume is stuck in 'attaching' state and the admin has to reset the state on it to make it available again.

[Matt Riedemann (mriedem)]

This code might actually be part of an incomplete blueprint, and if that's the case and no one is working on finishing that blueprint (since Andrea Rosa is no longer working on openstack and I think he added the change), then we should maybe just remove this code.

[Matt Riedemann (mriedem)]

Looks like the blueprint was completely implemented:

https://blueprints.launchpad.net/nova/+spec/volume-ops-when-shelved

So we just need to fix this corner case.

[Matt Riedemann (mriedem)]

This might be fixed by https://review.openstack.org/#/c/290793/