Booting Ceph instance using Ceph glance doesn't resize root disk to flavor size

[Matthew Booth]

This bug is purely from code inspection; I haven't replicated it on a running system.

Change I46b5658efafe558dd6b28c9910fb8fde830adec0 added a resize check that the backing file exists before checking its size. Unfortunately we forgot that Rbd overrides get_disk_size(path), and ignores the path argument, which means it would previously not have failed even when the given path didn't exist. Additionally, the callback function passed to cache() by driver will also ignore its path argument, and therefore not write to the image cache, when cloning to a ceph instance from a ceph glance store (see the section starting if backend.SUPPORTS_CLONE in driver._create_and_inject_local_root). Consequently, when creating a ceph instance using a ceph glance store:

1. 'base' will not exist in the image cache
2. get_disk_size(base) will return the correct value anyway

We broke this with change I46b5658efafe558dd6b28c9910fb8fde830adec0.

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: master
Review: https://review.openstack.org/370135

[Matthew Booth (mbooth-9)]

Turns out that this case is still covered because Rbd.create_image() does a redundant resize. So, while the resize described in the bug report doesn't happen, the image is still resized anyway. In fact, it's now only resized once whereas it was previously resized twice, so it's actually slightly more efficient.

I'm personally inclined to leave this alone now until the refactor lands and this all becomes a lot simpler to follow.

[Matt Riedemann (mriedem)]

https://review.openstack.org/#/c/370180/

[OpenStack Infra (hudson-openstack)]

Change abandoned by Matthew Booth (<email address hidden>) on branch: master
Review: https://review.openstack.org/370180
Reason: Not going to go this way.

[OpenStack Infra (hudson-openstack)]

Change abandoned by Matthew Booth (<email address hidden>) on branch: master
Review: https://review.openstack.org/370135
Reason: Not going to go this way.

[Sean Dague (sdague)]

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