Cold migration fails for instances with ephemeral disk

[Alexander Rubtsov]

Please backport the fix for the following upstream bug to Mitaka series:
https://bugs.launchpad.net/nova/+bug/1605720

--- Environment ---
* Mirantis OpenStack 9.2
* Qcow format for images
* Backend for ephemeral disks: file

--- Steps to reproduce ---
1) Build a new environment with at least 2 compute nodes

2) Create a new flavor with ephemeral disk
[root@node-2 ~]$ nova flavor-create --ephemeral 2 MigrationTest 10 512 0 1
+----+---------------+-----------+------+-----------+------+-------+-------------+-----------+
| ID | Name | Memory_MB | Disk | Ephemeral | Swap | VCPUs | RXTX_Factor | Is_Public |
+----+---------------+-----------+------+-----------+------+-------+-------------+-----------+
| 10 | MigrationTest | 512 | 0 | 2 | | 1 | 1.0 | True |
+----+---------------+-----------+------+-----------+------+-------+-------------+-----------+

3) Boot an instance based on this flavor
[root@node-2 ~]$ nova boot --image TestVM --flavor MigrationTest --nic net-id=d6bd7512-4f7e-46e1-8209-1dcc2f6ad44e MyVM-1 |

4) Migrate the instance
nova migrate --poll MyVM-1

--- Actual result ---
Server migrating... 0% complete
Error migrating server
ERROR (ResourceInErrorState):

In the nova-compute.log on target Compute node:
libvirtError: Cannot access backing file '/var/lib/nova/instances/_base/ephemeral_2_0706d66' of storage file '/var/lib/nova/instances/a1cbe06d-15f6-45b2-b17e-42bf250093ee/disk.eph0' (as uid:108, gid:117): No such file or directory

--- Expected result ---
The migration has successfully performed

[Alexander Rubtsov (arubtsov)]

sla1 for 9.0-updates

[Fuel Devops McRobotson (fuel-devops-robot)]

Fix proposed to branch: 9.0/mitaka
Change author: Chris Friesen <email address hidden>
Review: https://review.fuel-infra.org/35173

[Roman Podoliaka (rpodolyaka)]

The fix is already merged to 10.0: https://review.fuel-infra.org/#/c/30763/

[Fuel Devops McRobotson (fuel-devops-robot)]

Reviewed: https://review.fuel-infra.org/35173
Submitter: Pkgs Jenkins <email address hidden>
Branch: 9.0/mitaka

Commit: 019f3f79ebaaea5feafc70ac81c3c5846314ec36
Author: Chris Friesen <email address hidden>
Date: Thu May 4 10:00:52 2017

Fix cold migration with qcow2 ephemeral disks

If we have qcow2 ephemeral disks we need to ensure that the
backing file gets created on a cold migration.

This requires passing in the block_device_info when calling
_create_image() so that we can loop over the ephemeral disks.

Closes-Bug: #1686944
Co-Authored-By: Feodor Tersin <email address hidden>
Change-Id: Ie278bb10e1675ba1d903aaa3c0249be0d1cf147b
(cherry picked from commit d7b831e38cbc029b7975d1059ed212762a5f6a5e)

[TatyanaGladysheva (tgladysheva)]

Verified on 9.2 + mu2 updates.

The migration is finished successfully.
root@node-6:~# nova migrate --poll VM1
Server migrating... 100% complete
Finished

There is no errors in nova-compute.log on target compute node.

[Fuel Devops McRobotson (fuel-devops-robot)]

Fix proposed to branch: mcp/1.0/mitaka
Change author: Chris Friesen <email address hidden>
Review: https://review.fuel-infra.org/36364

[Fuel Devops McRobotson (fuel-devops-robot)]

Change abandoned by Vladyslav Drok <email address hidden> on branch: mcp/1.0/mitaka
Review: https://review.fuel-infra.org/36364

[Fuel Devops McRobotson (fuel-devops-robot)]

Change restored by Vladyslav Drok <email address hidden> on branch: mcp/1.0/mitaka
Review: https://review.fuel-infra.org/36364

[Fuel Devops McRobotson (fuel-devops-robot)]

Reviewed: https://review.fuel-infra.org/36364
Submitter: Pkgs Jenkins <email address hidden>
Branch: mcp/1.0/mitaka

Commit: ad686ec0dc8d72569b9470e5bfce88638aeac6af
Author: Chris Friesen <email address hidden>
Date: Wed Aug 30 18:45:15 2017

Fix cold migration with qcow2 ephemeral disks

If we have qcow2 ephemeral disks we need to ensure that the
backing file gets created on a cold migration.

This requires passing in the block_device_info when calling
_create_image() so that we can loop over the ephemeral disks.

Closes-Bug: #1686944
Co-Authored-By: Feodor Tersin <email address hidden>
(cherry picked from commit d7b831e38cbc029b7975d1059ed212762a5f6a5e)
(cherry picked from commit f1e07e8e5e34375d616e05b4b067930cdc48c664)
Change-Id: Ie278bb10e1675ba1d903aaa3c0249be0d1cf147b