resize revert still hitting the legacy allocation handling

[Balazs Gibizer]

During reverting a resize or a migration Nova still hits the legacy allocation handling code even if the migration is started without any old compute or controller in the system. Search for "Doing legacy allocation math" in [2] for examples.

It is caused by a faulty logic in compute manager[1]. It tries to decide if the reverted migration holds allocation or not to see if the migration is a legacy one or not. However in case of [1] the cn_uuid points to the destination node. Migration never holds allocation on the destination node so the condition at L3955 never be true and the code falls to the legacy path.

It seems that the legacy path still able to handled the allocation properly in the above case so no resource is leaked.

[1] https://github.com/openstack/nova/blob/8688b25ca7379391cba28fab30b5a628957e673e/nova/compute/manager.py#L3952-L3955
[2] http://logs.openstack.org/72/587772/1/check/neutron-tempest-multinode-full/0a2fb57/logs/screen-n-cpu.txt.gz

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/589425

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/589425
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=3311d579db2482c5d06cd4e245da57333b79a8db
Submitter: Zuul
Branch: master

commit 3311d579db2482c5d06cd4e245da57333b79a8db
Author: Balazs Gibizer <email address hidden>
Date: Tue Aug 7 12:57:47 2018 +0200

    Fix resize revert to use non-legacy alloc handling

    During the revert of resize or migrate nova tries to drop the
    allocation on the target host. But first it decides if the resize uses
    the new style allocation handling where the source host allocation is
    held by the migration. If not then the legacy double-up allocation
    handling is triggered.

    However the implementation tried to check if the migration holds
    allocation on the destination host and that is clearly wrong as migration
    only holds alloction on the source host.

    This patch now changes the check to simply assert if there is any
    allocation held by the migration.uuid.

    Change-Id: I41c10ca5caa01dda950dd17319889963850fed59
    Closes-Bug: #1785776

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/nova 18.0.0.0rc1 release candidate.