Comment 3 for bug 1572730

There is handling later in the looping where the instance from the DB isn't on the hypervisor, and in that case we assume no power state:

https://github.com/openstack/nova/blob/4ad414f3b1216393301ef268a64e61ca1a3d5be9/nova/compute/manager.py#L6223-L6227

Which actually makes this probably wrong:

https://github.com/openstack/nova/blob/4ad414f3b1216393301ef268a64e61ca1a3d5be9/nova/compute/manager.py#L6282-L6294

So let's consider this scenario: we have 5 instances on the hypervisor and 5 in the database, that's all normal. However, we're currently taking snapshots of two of those instances. If we filter on task_state != None, then we'd get the warning in:

https://github.com/openstack/nova/blob/4ad414f3b1216393301ef268a64e61ca1a3d5be9/nova/compute/manager.py#L6180

Even though the instances are on the hypervisor.

I think the thing we need to warn about is if there are more instances for that host in the DB than what's in the hypervisor, so change:

if num_vm_instances != num_db_instances:

to

if num_vm_instances < num_db_instances: