Hyper-V tries to logout from iSCSI targets in use

[Luis Fernández Álvarez]

When a volume is detached from a VM on Hyper-V, the Nova driver tries to disconnect from the iSCSI target, even if it's in use.

https://github.com/openstack/nova/blob/master/nova/virt/hyperv/volumeops.py#L194

This make sense when a volume (LUN) is associated with only one iscsi target, but this isn't always the case, you can have only one iSCSI target that exports more than one LUN to the hypervisor.

We could provide a general solution that will only disconnect from the iSCSI target when there aren't more disks exposed to the hypervisor.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/123695

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/123695
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=7cb0d9f8754e4f6b20c709a72ff87126c9972f51
Submitter: Jenkins
Branch: master

commit 7cb0d9f8754e4f6b20c709a72ff87126c9972f51
Author: Lucian Petrut <email address hidden>
Date: Wed Sep 24 12:22:35 2014 +0300

    Hyper-V: Skip logging out in-use targets

    As most of the Cinder volume drivers that use iSCSI export one LUN
    per iSCSI target, the Hyper-V driver was logging out the according
    target each time a volume was disconnected.

    This causes issues with some volume drivers that use multiple LUNs
    per iSCSI target and may disconnect in-use targets.

    This patch fixes the issue by checking if there are other LUNs
    being used, disconnecting the iSCSI targets otherwise.

    Change-Id: Ida08e7129a7b7940ddea488488cccc7571a43b76
    Closes-Bug: #1372815