Comment 3 for bug 1775418

Reviewed: https://review.opendev.org/572790
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=5a1d159d142997bb4288d4bf86d4e144334905cd
Submitter: Zuul
Branch: master

commit 5a1d159d142997bb4288d4bf86d4e144334905cd
Author: Matt Riedemann <email address hidden>
Date: Wed Jun 6 10:32:37 2018 -0400

    Block swap volume on volumes with >1 rw attachment

    If we're swapping from a multiattach volume that has more than one
    read/write attachment, another server on the secondary attachment could
    be writing to the volume which is not getting copied into the volume to
    which we're swapping, so we could have data loss during the swap.

    This change does volume read/write attachment counting for the volume
    we're swapping from and if there is more than one read/write attachment
    on the volume, the swap volume operation fails with a 400 BadRequest
    error.

    Depends-On: https://review.openstack.org/573025/
    Closes-Bug: #1775418
    Change-Id: Icd7fcb87a09c35a13e4e14235feb30a289d22778