Hyper-V: failed cold migrations cannot be reverted

[Lucian Petrut]

When performing a cold migration, the Hyper-V driver moves the instance files to a temporary folder, and from there, it copies them to the destination node.

The instance folder is not moved entirely, as it will hold some Hyper-V specific files that cannot be deleted/moved while the instance exists, basically we just take the files that we care about, while leaving the folder there.

If the migration fails, the driver tries to move the temporary directory to the actual instance path, but fails as there already is a folder.

Trace: http://paste.openstack.org/show/490025/

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/291733

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/291733
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=9740e18a31c0682d2852ac745242c69475d89113
Submitter: Jenkins
Branch: master

commit 9740e18a31c0682d2852ac745242c69475d89113
Author: Claudiu Belu <email address hidden>
Date: Fri Mar 11 16:09:52 2016 +0200

    hyper-v: Copies back files on failed migration

    On cold migration, the contents of the instance folder are
    copied to the new host. The original folder cannot be removed
    because the VM configuration files cannot be deleted until the VM
    is destroyed.

    Because of this, when the migration fails to copy the files, it will
    try to revert this through folder renaming. Since the original folder
    still exists, an exception is raised.

    Change-Id: Ia42ed873924999d57336a105bcaa2b856f3a3a9d
    Closes-Bug: #1555699

[Thierry Carrez (ttx)]

This issue was fixed in the openstack/nova 13.0.0.0rc1 release candidate.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/liberty
Review: https://review.openstack.org/320570

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/320570
Committed: https://git.openstack.org/cgit/openstack/compute-hyperv/commit/?id=7527a1f4d60a804f54cba7a7da706bf66863d789
Submitter: Jenkins
Branch: stable/liberty

commit 7527a1f4d60a804f54cba7a7da706bf66863d789
Author: Claudiu Belu <email address hidden>
Date: Thu Mar 17 03:35:51 2016 -0700

    hyper-v: Copies back files on failed migration

    On cold migration, the contents of the instance folder are
    copied to the new host. The original folder cannot be removed
    because the VM configuration files cannot be deleted until the VM
    is destroyed.

    Because of this, when the migration fails to copy the files, it will
    try to revert this through folder renaming. Since the original folder
    still exists, an exception is raised.

    Change-Id: Ia42ed873924999d57336a105bcaa2b856f3a3a9d
    Closes-Bug: #1555699
    (cherry picked from commit 7fb627c317d93b041b76263740f5729dade05b39)