Add support for Cinder File IO

This blue print outlines the work to add support for File I/O based
cinder drivers to the PowerVM driver.  A File I/O based cinder driver is
one that presents a file to the hypervisor via some mounted file system.

blueprint file-io-cinder-connector

Change-Id: I4b6f258726de8ed095f284386308134200ffbf2a

specs/pike/fileio_cinder.rst

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+..
+ This work is licensed under a Creative Commons Attribution 3.0 Unported
+ License.
+
+ http://creativecommons.org/licenses/by/3.0/legalcode
+
+=========================
+File I/O Cinder Connector
+=========================
+
+https://blueprints.launchpad.net/nova-powervm/+spec/file-io-cinder-connector
+
+There are several Cinder drivers that support having the file system mounted
+locally and then connecting in to the VM as a volume (ex. GPFS, NFS, etc...).
+There is the ability to support this type of volume in PowerVM, if the user
+has mounted the file system to the NovaLink.  This blueprint adds support to
+the PowerVM driver to support such Cinder volumes.
+
+
+Problem description
+===================
+
+The PowerVM driver supports Fibre Channel and iSCSI based volumes.  It does not
+currently support volumes that are presented on a file system as files.
+
+The recent release of PowerVM NovaLink has added support for this in the REST
+API.  This blueprint looks to take advantage of that support.
+
+
+Use Cases
+---------
+
+* As a user, I want to attach a volume that is backed by a file based Cinder
+  volume (ex. NFS or GPFS).
+
+* As a user, I want to detach a volume that is backed by a file based Cinder
+  volume (ex. NFS or GPFS).
+
+
+Proposed change
+===============
+
+Add nova_powervm/virt/powervm/volume/fileio.py.  This would extend the existing
+volume drivers.  It would store the LUN ID on the scsi bus.
+
+This does not support traditional VIOS.  Like the iSCSI change, it would
+require running through the NovaLink partition.
+
+
+Alternatives
+------------
+
+None
+
+
+Security impact
+---------------
+
+None.
+
+One may consider the permission of the file presented by Cinder.  The Cinder
+driver's BDM will provide a path to a file.  The hypervisor will map that file
+as the root user.  So file permissions of the volume should not be a concern.
+This seems consistent with the other hypervisors utilizing these types of
+Cinder drivers.
+
+End user impact
+---------------
+
+None
+
+
+Performance Impact
+------------------
+
+None
+
+
+Deployer impact
+---------------
+
+Deployer must set up the backing Cinder driver and connect the file systems to
+the NovaLink partition in their environment.
+
+
+Developer impact
+----------------
+
+None
+
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+  thorst
+
+Other contributors:
+  shyama
+
+Work Items
+----------
+
+* Create a nova-powervm fileio cinder volume connector.  Create associated UT.
+
+* Validate with the GPFS cinder backend.
+
+
+Dependencies
+============
+
+* pypowervm 1.0.0.4 or higher
+
+
+Testing
+=======
+
+Unit Testing is obvious.
+
+Manual testing will be driven via connecting to a GPFS back-end.
+
+CI environments will be evaluated to determine if there is a way to add this
+to the current CI infrastructure.
+
+
+Documentation Impact
+====================
+
+None.  Will update the nova-powervm dev-ref to reflect that 'file I/O drivers'
+are supported, but the support matrix doesn't go into the detail of what cinder
+drivers work with nova drivers.
+
+
+References
+==========
+
+* pypowervm add storage element to scsi mapping: https://github.com/powervm/pypowervm/blob/release/1.0.0.4/pypowervm/tasks/scsi_mapper.py#L49
+
+* pypowervm file storage element: https://github.com/powervm/pypowervm/blob/release/1.0.0.4/pypowervm/wrappers/storage.py#L689