Comment 9 for bug 1896621

Reviewed: https://review.opendev.org/754695
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=6cf449bdd0d4beb95cf12311e7d2f8669e625fac
Submitter: Zuul
Branch: master

commit 6cf449bdd0d4beb95cf12311e7d2f8669e625fac
Author: Lee Yarwood <email address hidden>
Date: Mon Sep 28 12:18:29 2020 +0100

    compute: Lock by instance.uuid lock during swap_volume

    The libvirt driver is currently the only virt driver implementing swap
    volume within Nova. While libvirt itself does support moving between
    multiple volumes attached to the same instance at the same time the
    current logic within the libvirt driver makes a call to
    virDomainGetXMLDesc that fails if there are active block jobs against
    any disk attached to the domain.

    This change simply uses an instance.uuid based lock in the compute layer
    to serialise requests to swap_volume to avoid this from being possible.

    Closes-Bug: #1896621
    Change-Id: Ic5ce2580e7638a47f1ffddb4edbb503bf490504c