EMC SMI-S driver needs to check if a volume is attached to a specific host

[Xing Yang]

There's a problem in the attach volume logic of the EMC SMI-S driver. The existing logic checks if a volume is already attached to a host, but it doesn’t check whether it is attached to the host inidicated by the connector info.
So we need to add a check to see if a volume is already attached to a specific host. If not, it will do the attach.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/82653

[Xing Yang (xing-yang)]

The reason that the volume being attached already could be due to a nova live-migration use case. Cinder doesn't support multiple attaches currently, but allows a volume to be attached multiple times from nova during live-migration.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/82653
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=7320422e5a496350906dcd2a1cd5487088cf63e5
Submitter: Jenkins
Branch: master

commit 7320422e5a496350906dcd2a1cd5487088cf63e5
Author: Xing Yang <email address hidden>
Date: Sat Mar 22 15:05:42 2014 -0400

    Fixes a problem in attach volume in EMC driver.

    This patch fixes a problem in attach volume in EMC SMI-S driver.
    The existing logic checks if a volume is already attached to any host,
    but it doesn't check whether a volume is already attached to the specific
    host that nova wants cinder to attach. As a result, initialize_connection
    could return success (thinking it is already attached), but nova will
    fail to discover the LUN later and fail the attach.

    This patch adds a check to see if a volume is already attached to a
    specific host. If not, it will do the attach. The reason that the
    volume being attached already could be due to a nova live-migration
    use case. Cinder doesn't support multiple attaches currently, but
    allows a volume to be attached multiple times from nova during
    live-migration.

    Change-Id: I05a2f57cd8708d7fcbe902ec13665a9cfb44db07
    Closes-Bug: #1295906