Unity: add multiattach support

Add the ability to attach a volume to multiple servers simultaneously.

Implements: blueprint unity-multiattach-support

Change-Id: Ib7222bb3cd13505f9a8789f8cc85685e4ae9cce4

cinder/tests/unit/volume/drivers/dell_emc/unity/test_adapter.py

@@ -482,7 +482,8 @@ class CommonAdapterTest(test.TestCase):
 
     def test_terminate_connection_volume(self):
         def f():
-            volume = MockOSResource(provider_location='id^lun_43', id='id_43')
+            volume = MockOSResource(provider_location='id^lun_43', id='id_43',
+                                    volume_attachment=None)
             connector = {'host': 'host1'}
             self.adapter.terminate_connection(volume, connector)
 
@@ -490,7 +491,8 @@ class CommonAdapterTest(test.TestCase):
 
     def test_terminate_connection_force_detach(self):
         def f():
-            volume = MockOSResource(provider_location='id^lun_44', id='id_44')
+            volume = MockOSResource(provider_location='id^lun_44', id='id_44',
+                                    volume_attachment=None)
             self.adapter.terminate_connection(volume, None)
 
         self.assertRaises(ex.DetachAllIsCalled, f)
@@ -498,7 +500,8 @@ class CommonAdapterTest(test.TestCase):
     def test_terminate_connection_snapshot(self):
         def f():
             connector = {'host': 'host1'}
-            snap = MockOSResource(name='snap_0', id='snap_0')
+            snap = MockOSResource(name='snap_0', id='snap_0',
+                                  volume_attachment=None)
             self.adapter.terminate_connection_snapshot(snap, connector)
 
         self.assertRaises(ex.DetachIsCalled, f)
@@ -508,11 +511,27 @@ class CommonAdapterTest(test.TestCase):
 
         def f():
             connector = {'host': 'empty-host'}
-            vol = MockOSResource(provider_location='id^lun_45', id='id_45')
+            vol = MockOSResource(provider_location='id^lun_45', id='id_45',
+                                 volume_attachment=None)
             self.adapter.terminate_connection(vol, connector)
 
         self.assertRaises(ex.HostDeleteIsCalled, f)
 
+    def test_terminate_connection_multiattached_volume(self):
+        def f():
+            connector = {'host': 'host1'}
+            attachments = [MockOSResource(id='id-1',
+                                          attach_status='attached',
+                                          attached_host='host1'),
+                           MockOSResource(id='id-2',
+                                          attach_status='attached',
+                                          attached_host='host1')]
+            vol = MockOSResource(provider_location='id^lun_45', id='id_45',
+                                 volume_attachment=attachments)
+            self.adapter.terminate_connection(vol, connector)
+
+        self.assertIsNone(f())
+
     def test_manage_existing_by_name(self):
         ref = {'source-id': 12}
         volume = MockOSResource(name='lun1')
@@ -844,7 +863,8 @@ class FCAdapterTest(test.TestCase):
 
     def test_terminate_connection_auto_zone_enabled(self):
         connector = {'host': 'host1', 'wwpns': 'abcdefg'}
-        volume = MockOSResource(provider_location='id^lun_41', id='id_41')
+        volume = MockOSResource(provider_location='id^lun_41', id='id_41',
+                                volume_attachment=None)
         ret = self.adapter.terminate_connection(volume, connector)
         self.assertEqual('fibre_channel', ret['driver_volume_type'])
         data = ret['data']
@@ -857,7 +877,8 @@ class FCAdapterTest(test.TestCase):
 
     def test_terminate_connection_auto_zone_enabled_none_host_luns(self):
         connector = {'host': 'host-no-host_luns', 'wwpns': 'abcdefg'}
-        volume = MockOSResource(provider_location='id^lun_41', id='id_41')
+        volume = MockOSResource(provider_location='id^lun_41', id='id_41',
+                                volume_attachment=None)
         ret = self.adapter.terminate_connection(volume, connector)
         self.assertEqual('fibre_channel', ret['driver_volume_type'])
         data = ret['data']
@@ -871,7 +892,8 @@ class FCAdapterTest(test.TestCase):
     def test_terminate_connection_remove_empty_host_return_data(self):
         self.adapter.remove_empty_host = True
         connector = {'host': 'empty-host-return-data', 'wwpns': 'abcdefg'}
-        volume = MockOSResource(provider_location='id^lun_41', id='id_41')
+        volume = MockOSResource(provider_location='id^lun_41', id='id_41',
+                                volume_attachment=None)
         ret = self.adapter.terminate_connection(volume, connector)
         self.assertEqual('fibre_channel', ret['driver_volume_type'])
         data = ret['data']

cinder/volume/drivers/dell_emc/unity/adapter.py

@@ -348,11 +348,13 @@ class CommonAdapter(object):
         # No target info for iSCSI driver
         return []
 
-    def _detach_and_delete_host(self, host_name, lun_or_snap):
+    def _detach_and_delete_host(self, host_name, lun_or_snap,
+                                is_multiattach_to_host=False):
         @utils.lock_if(self.to_lock_host, '{lock_name}')
         def _lock_helper(lock_name):
             # Only get the host from cache here
             host = self.client.create_host_wo_lock(host_name)
+            if not is_multiattach_to_host:
                 self.client.detach(host, lun_or_snap)
             host.update()  # need update to get the latest `host_luns`
             targets = self.filter_targets_by_host(host)
@@ -368,14 +370,16 @@ class CommonAdapter(object):
         # No return data from terminate_connection for iSCSI driver
         return {}
 
-    def _terminate_connection(self, lun_or_snap, connector):
+    def _terminate_connection(self, lun_or_snap, connector,
+                              is_multiattach_to_host=False):
         is_force_detach = connector is None
         data = {}
         if is_force_detach:
             self.client.detach_all(lun_or_snap)
         else:
-            targets = self._detach_and_delete_host(connector['host'],
+            targets = self._detach_and_delete_host(
-                                                   lun_or_snap)
+                connector['host'], lun_or_snap,
+                is_multiattach_to_host=is_multiattach_to_host)
             data = self.get_terminate_connection_info(connector, targets)
         return {
             'driver_volume_type': self.driver_volume_type,
@@ -385,7 +389,14 @@ class CommonAdapter(object):
     @cinder_utils.trace
     def terminate_connection(self, volume, connector):
         lun = self.client.get_lun(lun_id=self.get_lun_id(volume))
-        return self._terminate_connection(lun, connector)
+        # None `connector` indicates force detach, then detach all even the
+        # volume is multi-attached.
+        multiattach_flag = (connector is not None and
+                            utils.is_multiattach_to_host(
+                                volume.volume_attachment,
+                                connector['host']))
+        return self._terminate_connection(
+            lun, connector, is_multiattach_to_host=multiattach_flag)
 
     def get_connector_uids(self, connector):
         return None
@@ -443,7 +454,9 @@ class CommonAdapter(object):
             'thin_provisioning_support': True,
             'thick_provisioning_support': True,
             'max_over_subscription_ratio': (
-                self.max_over_subscription_ratio)}
+                self.max_over_subscription_ratio),
+            'multiattach': True
+        }
 
     def get_lun_id(self, volume):
         """Retrieves id of the volume's backing LUN.

cinder/volume/drivers/dell_emc/unity/utils.py

@@ -26,6 +26,7 @@ import six
 from cinder import coordination
 from cinder import exception
 from cinder.i18n import _
+from cinder.objects import fields
 from cinder.volume import utils as vol_utils
 from cinder.volume import volume_types
 from cinder.zonemanager import utils as zm_utils
@@ -304,3 +305,18 @@ def lock_if(condition, lock_name):
         return coordination.synchronized(lock_name)
     else:
         return functools.partial
+
+
+def is_multiattach_to_host(volume_attachment, host_name):
+    # When multiattach is enabled, a volume could be attached to two or more
+    # instances which are hosted on one nova host.
+    # Because unity cannot recognize the volume is attached to two or more
+    # instances, we should keep the volume attached to the nova host until
+    # the volume is detached from the last instance.
+    if not volume_attachment:
+        return False
+
+    attachment = [a for a in volume_attachment
+                  if a.attach_status == fields.VolumeAttachStatus.ATTACHED and
+                  a.attached_host == host_name]
+    return len(attachment) > 1

doc/source/configuration/block-storage/drivers/dell-emc-unity-driver.rst

@@ -34,6 +34,7 @@ Supported operations
 - Efficient non-disruptive volume backup.
 - Revert a volume to a snapshot.
 - Create thick volumes.
+- Attach a volume to multiple servers simultaneously (multiattach).
 
 Driver configuration
 ~~~~~~~~~~~~~~~~~~~~

releasenotes/notes/unity-multiattach-support-993b997e522d9e84.yaml

@@ -0,0 +1,7 @@
+---
+features:
+  - |
+    Dell EMC Unity: Implements `bp unity-multiattach-support
+    <https://blueprints.launchpad.net/cinder/+spec/unity-multiattach-support>`__
+    to support attaching a volume to multiple servers simultaneously.
+