Comment 46 for bug 1469179

Reviewed: https://review.openstack.org/580720
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=03c596a9f4324e572bc04d4bbad09a6d3d47366c
Submitter: Zuul
Branch: master

commit 03c596a9f4324e572bc04d4bbad09a6d3d47366c
Author: Dan Smith <email address hidden>
Date: Fri Jul 6 09:09:05 2018 -0700

    Avoid requesting DISK_GB allocation for root_gb on BFV instances

    Right now, we still ask placement for a disk allocation covering
    swap, ephemeral, and root disks for the instance even if the instance
    is going to be volume-backed. This patch makes us not include the
    root size in that calculation for placement, avoiding a false
    failure because the volume size is counted against the compute's
    available space.

    To do this, we need another flag in request_spec to track the
    BFV-ness of the instance. Right now, this patch just sets that on
    new builds and the scheduler client assumes a lack of said flag
    as "I don't know, so assume not-BFV" for compatibility. A
    subsequent patch can calculate that flag for existing instances
    so that we will be able to heal over time by migrating instances
    or re-writing their allocations to reflect reality.

    Partial-Bug: #1469179
    Change-Id: I9c2111f7377df65c1fc3c72323f85483b3295989