Block device metadata may be bogus with Ironic driver

[Ben Nemec]

This is a followup to the regression reported in https://bugs.launchpad.net/nova/+bug/1464239 The problem there was that Nova changed how it does block device mapping for ephemeral partitions, and because Ironic isn't using that block device mapping the ephemeral path returned by the metadata server became incorrect. I'm opening this bug because while it is possible to fix the regression, the behavior is still bad. The ephemeral partition metadata is only valid if Ironic happens to assign the ephemeral partition to /dev/sda1. This is often the case, but there are valid situations where it is not true - consider deploying to a vm where the ephemeral partition ends up on /dev/vda1.

Since I believe this would require a new method of synchronizing the block device mapping between Nova and Ironic, I'm pushing a fix for the regression to unbreak the previously working cases, and opening this bug to document that the situation is still not right.

[Matt Riedemann (mriedem)]

Looks like this is the proposed change: https://review.openstack.org/#/c/205271/

[Michael Davies (mrda)]

Pinged Ben on IRC, to see if we can assign this one to him as well since the patch addresses most (all?) of this.

[John L. Villalovos (happycamp)]

mrda and I pinged bnemec on IRC:
http://eavesdrop.openstack.org/irclogs/%23openstack-ironic/%23openstack-ironic.2015-08-14.log.html

He thinks his patch does not fix all cases affected by this bug.

[Jim Rollenhagen (jim-rollenhagen)]

Seems related to https://bugs.launchpad.net/nova/+bug/1328939

[OpenStack Infra (hudson-openstack)]

Change abandoned by Ben Nemec (<email address hidden>) on branch: master
Review: https://review.openstack.org/205271
Reason: Yeah, I keep telling myself I'll come back to this, but at this point I think that's pretty clearly a lie. :-)

I'll restore if I get a chance to revisit it.