Comment 3 for bug 1885528

Reviewed: https://review.opendev.org/739246
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=b9333125790682f9d60bc74fdbb12a098565e7c2
Submitter: Zuul
Branch: master

commit b9333125790682f9d60bc74fdbb12a098565e7c2
Author: Balazs Gibizer <email address hidden>
Date: Thu Jul 2 12:13:29 2020 +0200

    Use absolute path during qemu img rebase

    During an assisted volume snapshot delete request from Cinder nova
    removes the snapshot from the backing file chain. During that nova
    checks the existence of such file. However in some cases (see the bug
    report) the path is relative and therefore os.path.exists fails.

    This patch makes sure that nova uses the volume absolute path to make
    the backing file path absolute as well.

    Closes-Bug #1885528

    Change-Id: I58dca95251b607eaff602783fee2fc38e2421944