Add LibvirtGPFSVolumeDriver class

Currently, GPFS use LibvirtVolumeDriver to generate the libvirt
xml configuration when attaching a gpfs volume. But the driver
always set the disk_type to 'block' which should be 'file' for
GPFS volume.

This patch create a new volume driver class for GPFS, the class
can generate the right xml configuration for GPFS volume.

Change-Id: Ica1cf3558baeea12b519bda50c61cea446429364
Closes-Bug:#1405044

nova/tests/unit/virt/libvirt/test_volume.py

@@ -1350,3 +1350,17 @@ Setting up iSCSI targets: unused
              export_string, export_mnt_base),
             ('umount', export_mnt_base)]
         self.assertEqual(expected_commands, self.executes)
+
+    def test_libvirt_gpfs_driver_get_config(self):
+        libvirt_driver = volume.LibvirtGPFSVolumeDriver(self.fake_conn)
+        connection_info = {
+            'driver_volume_type': 'gpfs',
+            'data': {
+                'device_path': '/gpfs/foo',
+            },
+            'serial': 'fake_serial',
+        }
+        conf = libvirt_driver.get_config(connection_info, self.disk_info)
+        tree = conf.format_dom()
+        self.assertEqual('file', tree.get('type'))
+        self.assertEqual('fake_serial', tree.find('./serial').text)

nova/virt/libvirt/driver.py

@@ -180,6 +180,8 @@ libvirt_opts = [
                       'LibvirtFibreChannelVolumeDriver',
                   'scality='
                       'nova.virt.libvirt.volume.LibvirtScalityVolumeDriver',
+                  'gpfs='
+                      'nova.virt.libvirt.volume.LibvirtGPFSVolumeDriver',
                   ],
                 help='DEPRECATED. Libvirt handlers for remote volumes. '
                      'This option is deprecated and will be removed in the '

nova/virt/libvirt/volume.py

@@ -1252,3 +1252,18 @@ class LibvirtScalityVolumeDriver(LibvirtBaseVolumeDriver):
             msg = _LW("Cannot mount Scality SOFS, check syslog for errors")
             LOG.warn(msg)
             raise exception.NovaException(msg)
+
+
+class LibvirtGPFSVolumeDriver(LibvirtBaseVolumeDriver):
+    """Class for volumes backed by gpfs volume."""
+    def __init__(self, connection):
+        super(LibvirtGPFSVolumeDriver,
+              self).__init__(connection, is_block_dev=False)
+
+    def get_config(self, connection_info, disk_info):
+        """Returns xml for libvirt."""
+        conf = super(LibvirtGPFSVolumeDriver,
+                     self).get_config(connection_info, disk_info)
+        conf.source_type = "file"
+        conf.source_path = connection_info['data']['device_path']
+        return conf