Capacity filter should check free space if total space is unknown

[Clinton Knight]

The Manila capacity filter accepts values of 'unknown' for both total and free space in a pool. If free space is unknown, then the scheduler always allows a create (as it should). But the scheduler also always allows a create if total space is unknown, even if free space is known; in this case, the filter should compare the request against the available free space before allowing the create.

[Xing Yang (xing-yang)]

Is there any driver that reports 'unknown' for total but an actual number for free? I didn't think that is a realistic case. If a driver knows free, it should also know total. If a driver reports 'unknown' total but an actual number for free, I think that is an implementation error that we should not encourage.

[Clinton Knight (clintonk)]

Yes! When DHSS == False, the NetApp cDOT driver can run with either full cluster credentials, or with limited storage-virtual-machine-scoped credentials. The latter case applies when only part of a multi-workload cluster is being used for Manila shares. In that case, the driver is not able to access any APIs associated with physical attributes of the cluster (nodes, disks, aggregates, etc.), and the driver can get free space but not total space for an aggregate (i.e. a Manila pool). The thin-provisioning code that went into the Manila scheduler broke this operating mode of the driver (because it was reporting 0.0 instead of unknown for total space), and I noticed while debugging that the scheduler could safely check the free space in the case that total space is unknown.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/221809

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/221809
Committed: https://git.openstack.org/cgit/openstack/manila/commit/?id=209fdeebb1c61dddfa9793d6f969378f42f4fcdd
Submitter: Jenkins
Branch: master

commit 209fdeebb1c61dddfa9793d6f969378f42f4fcdd
Author: Clinton Knight <email address hidden>
Date: Sun Aug 30 22:01:26 2015 -0400

    Capacity filter should check free space if total space is unknown

    The Manila capacity filter accepts values of 'unknown' for both
    total and free space in a pool. If free space is unknown, then
    the scheduler always allows a create (as it should). But the
    scheduler also always allows a create if total space is unknown,
    even if free space is known; in this case, the filter should
    compare the request against the available free space before
    allowing the create.

    Change-Id: Iad357f2472da1db493df42484c90cacf688608f8
    Closes-Bug: 1490364