Libvirt pre-Grizzly instances cannot be block migrated

[Rafi Khardalian]

This impacts Grizzly and master.

Any instances created prior to Grizzly will fail to block migrate. Prior to Grizzly, the default image structure was to convert all base images to RAW, then resize said image to match that of the selected flavor. Thus, the _base directory would contain <image_hash> and <image_hash>_<size_gb>. From there, QCOW2 files would be created, based on the resized backing file. The entire notion of resized base files was eliminated with Grizzly (rightfully so) and with it the code which would handle creating these resized backing files.

The problem is that many environments still have instances created with this backing structure. When utilizing live block migrations (nova live-migration --block-migrate), we rely on the destination hypervisor to re-populate _base images from Glance. Therein lies the problem, we do not have the code to detect or generate <image_hash>_<size_gb> base images. Thus, the block live migration will fail. The same situation applies if a _base image happens to go missing. We added code in Grizzly to re-download/generate missing _base images upon instance reboot, which cannot currently succeed due to the same issue.

[Rafi Khardalian (rkhardalian)]

I'll be submitting a patch for this shortly.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/30951

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/30951
Committed: http://github.com/openstack/nova/commit/6e768363450774cfee90e41aa5c40af780d3e04a
Submitter: Jenkins
Branch: master

commit 6e768363450774cfee90e41aa5c40af780d3e04a
Author: Rafi Khardalian <email address hidden>
Date: Wed May 29 21:26:19 2013 +0000

    Regenerate missing resized backing files

    Fixes bug 1185588

    The only way to reliably determine whether we are using a legacy
    (pre-Grizzly) backing structure is to look at the backing file
    reference for the instance/disk itself. Thus, if we determine the
    backing file contains an underscore, we use the value following it
    as our legacy_backing_size, which is then used to create the
    necessary backing file.

    Change-Id: I145f71068c972a604e5361ae79d6315286136786

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/grizzly
Review: https://review.openstack.org/32767

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/33007

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/32767
Committed: http://github.com/openstack/nova/commit/69dd7c50a95518788018dd1cb8aad60029fdac42
Submitter: Jenkins
Branch: stable/grizzly

commit 69dd7c50a95518788018dd1cb8aad60029fdac42
Author: Rafi Khardalian <email address hidden>
Date: Wed May 29 21:26:19 2013 +0000

    Regenerate missing resized backing files

    Fixes bug 1185588 (for stable/grizzly)

    The only way to reliably determine whether we are using a legacy
    (pre-Grizzly) backing structure is to look at the backing file
    reference for the instance/disk itself. Thus, if we determine the
    backing file contains an underscore, we use the value following it
    as our legacy_backing_size, which is then used to create the
    necessary backing file.

    Change-Id: I145f71068c972a604e5361ae79d6315286136786
    Cherry-Pick: 6e768363450774cfee90e41aa5c40af780d3e04a

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/33007
Committed: http://github.com/openstack/nova/commit/cf3cf3c8e5137e775eec9939e88aa1df339ba1bf
Submitter: Jenkins
Branch: master

commit cf3cf3c8e5137e775eec9939e88aa1df339ba1bf
Author: Rafi Khardalian <email address hidden>
Date: Fri Jun 14 06:47:57 2013 +0000

    libvirt fix resize/migrates with swap or ephemeral

    Fixes bug 1191608

    The code was not properly guarding against backing files not
    existing with QCOW2 images. As such, get_disk_backing_file() would
    return None, then the subsequent call to basename() on None would
    cause an exception.

    This bug was introduced with the fix for bug 1185588 and commit
    6e768363.

    Change-Id: I4b1237ddf01b9398bfdc141180260136b36cae5a