Comment 7 for bug 1821755

Reviewed: https://review.opendev.org/c/openstack/nova/+/784166
Committed: https://opendev.org/openstack/nova/commit/33c8af1f8c46c9c37fcc28fb3409fbd3a78ae39f
Submitter: "Zuul (22348)"
Branch: master

commit 33c8af1f8c46c9c37fcc28fb3409fbd3a78ae39f
Author: Rodrigo Barbieri <email address hidden>
Date: Wed Mar 31 11:06:49 2021 -0300

    Error anti-affinity violation on migrations

    Error-out the migrations (cold and live) whenever the
    anti-affinity policy is violated. This addresses
    violations when multiple concurrent migrations are
    requested.

    Added detection on:
    - prep_resize
    - check_can_live_migration_destination
    - pre_live_migration

    The improved method of detection now locks based on group_id
    and considers other migrations in-progress as well.

    Closes-bug: #1821755
    Change-Id: I32e6214568bb57f7613ddeba2c2c46da0320fabc