propagate OSError to MigrationPreCheckError

OSError will lead instance to ERROR state, change to
MigrationPreCheckError will make the instance status not changed.

Also, modify some test cases to make unit test easier

Closes-Bug: 1694636

Change-Id: I3286c32ca205ffd2d5d1aaab88cc96699476e410
(cherry picked from commit cb565d9bad)

nova/tests/unit/virt/hyperv/test_livemigrationops.py

@@ -17,6 +17,7 @@ import mock
 from os_win import exceptions as os_win_exc
 from oslo_config import cfg
 
+from nova import exception
 from nova.objects import migrate_data as migrate_data_obj
 from nova.tests.unit import fake_instance
 from nova.tests.unit.virt.hyperv import test_base
@@ -227,3 +228,13 @@ class LiveMigrationOpsTestCase(test_base.HyperVBaseTestCase):
             block_migration=mock.sentinel.BLOCK_INFO)
         mock_plug_vifs.assert_called_once_with(mock.sentinel.instance,
                                                mock.sentinel.NET_INFO)
+
+    def test_check_can_live_migrate_destination_exception(self):
+        mock_instance = fake_instance.fake_instance_obj(self.context)
+        mock_check = self._pathutils.check_remote_instances_dir_shared
+        mock_check.side_effect = exception.FileNotFound(file_path='C:\\baddir')
+        self.assertRaises(
+            exception.MigrationPreCheckError,
+            self._livemigrops.check_can_live_migrate_destination,
+            mock.sentinel.context, mock_instance, mock.sentinel.src_comp_info,
+            mock.sentinel.dest_comp_info)

nova/tests/unit/virt/hyperv/test_pathutils.py

@@ -196,6 +196,20 @@ class PathUtilsTestCase(test_base.HyperVBaseTestCase):
         mock_named_tempfile.assert_called_once_with(dir=fake_dest_dir)
         mock_exists.assert_called_once_with(expected_src_tmp_path)
 
+    @mock.patch('os.path.exists')
+    @mock.patch('tempfile.NamedTemporaryFile')
+    def test_check_dirs_shared_storage_exception(self, mock_named_tempfile,
+                                                 mock_exists):
+        fake_src_dir = 'fake_src_dir'
+        fake_dest_dir = 'fake_dest_dir'
+
+        mock_exists.return_value = True
+        mock_named_tempfile.side_effect = OSError('not exist')
+
+        self.assertRaises(exception.FileNotFound,
+            self._pathutils.check_dirs_shared_storage,
+            fake_src_dir, fake_dest_dir)
+
     @mock.patch.object(pathutils.PathUtils, 'check_dirs_shared_storage')
     @mock.patch.object(pathutils.PathUtils, 'get_instances_dir')
     def test_check_remote_instances_shared(self, mock_get_instances_dir,

nova/virt/hyperv/livemigrationops.py

@@ -22,6 +22,8 @@ from oslo_log import log as logging
 from oslo_utils import excutils
 
 import nova.conf
+from nova import exception
+from nova.i18n import _
 from nova.objects import migrate_data as migrate_data_obj
 from nova.virt.hyperv import block_device_manager
 from nova.virt.hyperv import imagecache
@@ -129,9 +131,16 @@ class LiveMigrationOps(object):
                   instance=instance_ref)
 
         migrate_data = migrate_data_obj.HyperVLiveMigrateData()
-        migrate_data.is_shared_instance_path = (
-            self._pathutils.check_remote_instances_dir_shared(
-                instance_ref.host))
+
+        try:
+            # The remote instance dir might not exist or other issue to cause
+            # OSError in check_remote_instances_dir_shared function
+            migrate_data.is_shared_instance_path = (
+                self._pathutils.check_remote_instances_dir_shared(
+                    instance_ref.host))
+        except exception.FileNotFound as e:
+            reason = _('Unavailable instance location: %s') % e
+            raise exception.MigrationPreCheckError(reason=reason)
         return migrate_data
 
     def cleanup_live_migration_destination_check(self, ctxt, dest_check_data):

nova/virt/hyperv/pathutils.py

@@ -14,6 +14,7 @@
 #    under the License.
 
 import os
+import six
 import tempfile
 import time
 
@@ -181,11 +182,15 @@ class PathUtils(pathutils.PathUtils):
         LOG.debug("Checking if %(src_dir)s and %(dest_dir)s point "
                   "to the same location.",
                   dict(src_dir=src_dir, dest_dir=dest_dir))
-        with tempfile.NamedTemporaryFile(dir=dest_dir) as tmp_file:
-            src_path = os.path.join(src_dir,
-                                    os.path.basename(tmp_file.name))
 
-            shared_storage = os.path.exists(src_path)
+        try:
+            with tempfile.NamedTemporaryFile(dir=dest_dir) as tmp_file:
+                src_path = os.path.join(src_dir,
+                                        os.path.basename(tmp_file.name))
+                shared_storage = os.path.exists(src_path)
+        except OSError as e:
+            raise exception.FileNotFound(six.text_type(e))
+
         return shared_storage
 
     def check_remote_instances_dir_shared(self, dest):