Merge "xenapi: ensure vdi is not too big when resizing down"

10 files changed, 384 insertions, 75 deletions

diff --git a/nova/compute/manager.py b/nova/compute/manager.py
index 79903f854..7bc8281d4 100755
--- a/nova/compute/manager.py
+++ b/nova/compute/manager.py
@@ -4117,6 +4117,13 @@ class ComputeManager(manager.SchedulerDependentManager):
                                         reservations=None):
         try:
             yield
+        except exception.InstanceFaultRollback, error:
+            self._quota_rollback(context, reservations)
+            msg = _("Setting instance back to ACTIVE after: %s")
+            LOG.info(msg % error, instance_uuid=instance_uuid)
+            self._instance_update(context, instance_uuid,
+                                  vm_state=vm_states.ACTIVE)
+            raise error.inner_exception
         except Exception, error:
             with excutils.save_and_reraise_exception():
                 self._quota_rollback(context, reservations)
diff --git a/nova/exception.py b/nova/exception.py
index a9afe37a7..439891153 100644
--- a/nova/exception.py
+++ b/nova/exception.py
@@ -1196,3 +1196,10 @@ class BuildAbortException(NovaException):
 class RescheduledException(NovaException):
     message = _("Build of instance %(instance_uuid)s was re-scheduled: "
                 "%(reason)s")
+
+
+class InstanceFaultRollback(NovaException):
+    def __init__(self, inner_exception=None):
+        message = _("Instance rollback performed due to: %s")
+        self.inner_exception = inner_exception
+        super(InstanceFaultRollback, self).__init__(message % inner_exception)
diff --git a/nova/tests/compute/test_compute.py b/nova/tests/compute/test_compute.py
index 9560fc78c..2adb07bdb 100644
--- a/nova/tests/compute/test_compute.py
+++ b/nova/tests/compute/test_compute.py
@@ -3089,6 +3089,43 @@ class ComputeTestCase(BaseTestCase):
         self.compute.terminate_instance(self.context,
             instance=jsonutils.to_primitive(instance))
 
+    def test_resize_instance_driver_rollback(self):
+        # Ensure instance status set to Running after rollback.
+
+        def throw_up(*args, **kwargs):
+            raise exception.InstanceFaultRollback(test.TestingException())
+
+        self.stubs.Set(self.compute.driver, 'migrate_disk_and_power_off',
+                       throw_up)
+
+        instance = jsonutils.to_primitive(self._create_fake_instance())
+        instance_type = flavors.get_default_instance_type()
+        reservations = self._ensure_quota_reservations_rolledback()
+        self.compute.run_instance(self.context, instance=instance)
+        new_instance = db.instance_update(self.context, instance['uuid'],
+                                      {'host': 'foo'})
+        new_instance = jsonutils.to_primitive(new_instance)
+        self.compute.prep_resize(self.context, instance=new_instance,
+                                 instance_type=instance_type, image={},
+                                 reservations=reservations)
+        migration_ref = db.migration_get_by_instance_and_status(
+                self.context.elevated(), new_instance['uuid'], 'pre-migrating')
+        db.instance_update(self.context, new_instance['uuid'],
+                           {"task_state": task_states.RESIZE_PREP})
+
+        self.assertRaises(test.TestingException, self.compute.resize_instance,
+                          self.context, instance=new_instance,
+                          migration=migration_ref, image={},
+                          reservations=reservations,
+                          instance_type=jsonutils.to_primitive(instance_type))
+
+        instance = db.instance_get_by_uuid(self.context, new_instance['uuid'])
+        self.assertEqual(instance['vm_state'], vm_states.ACTIVE)
+        self.assertEqual(instance['task_state'], None)
+
+        self.compute.terminate_instance(self.context,
+            instance=jsonutils.to_primitive(instance))
+
     def test_resize_instance(self):
         # Ensure instance can be migrated/resized.
         instance = jsonutils.to_primitive(self._create_fake_instance())
diff --git a/nova/tests/test_xenapi.py b/nova/tests/test_xenapi.py
index 9a366d7bf..45ebfaab3 100644
--- a/nova/tests/test_xenapi.py
+++ b/nova/tests/test_xenapi.py
@@ -1513,6 +1513,122 @@ class XenAPIMigrateInstance(stubs.XenAPITestBase):
                           self.context, instance,
                           '127.0.0.1', instance_type, None)
 
+    def test_migrate_rollback_when_resize_down_fs_fails(self):
+        conn = xenapi_conn.XenAPIDriver(fake.FakeVirtAPI(), False)
+        vmops = conn._vmops
+        virtapi = vmops._virtapi
+
+        self.mox.StubOutWithMock(vmops, '_resize_ensure_vm_is_shutdown')
+        self.mox.StubOutWithMock(vmops, '_apply_orig_vm_name_label')
+        self.mox.StubOutWithMock(vm_utils, 'resize_disk')
+        self.mox.StubOutWithMock(vmops, '_migrate_vhd')
+        self.mox.StubOutWithMock(vm_utils, 'destroy_vdi')
+        self.mox.StubOutWithMock(vm_utils, 'get_vdi_for_vm_safely')
+        self.mox.StubOutWithMock(vmops, '_restore_orig_vm_and_cleanup_orphan')
+        self.mox.StubOutWithMock(virtapi, 'instance_update')
+
+        instance = {'auto_disk_config': True, 'uuid': 'uuid'}
+        vm_ref = "vm_ref"
+        dest = "dest"
+        instance_type = "type"
+        sr_path = "sr_path"
+
+        virtapi.instance_update(self.context, 'uuid', {'progress': 20.0})
+        vmops._resize_ensure_vm_is_shutdown(instance, vm_ref)
+        vmops._apply_orig_vm_name_label(instance, vm_ref)
+        old_vdi_ref = "old_ref"
+        vm_utils.get_vdi_for_vm_safely(vmops._session, vm_ref).AndReturn(
+            (old_vdi_ref, None))
+        virtapi.instance_update(self.context, 'uuid', {'progress': 40.0})
+        new_vdi_ref = "new_ref"
+        new_vdi_uuid = "new_uuid"
+        vm_utils.resize_disk(vmops._session, instance, old_vdi_ref,
+            instance_type).AndReturn((new_vdi_ref, new_vdi_uuid))
+        virtapi.instance_update(self.context, 'uuid', {'progress': 60.0})
+        vmops._migrate_vhd(instance, new_vdi_uuid, dest,
+                           sr_path, 0).AndRaise(
+                                exception.ResizeError(reason="asdf"))
+
+        vm_utils.destroy_vdi(vmops._session, new_vdi_ref)
+        vmops._restore_orig_vm_and_cleanup_orphan(instance, None)
+
+        self.mox.ReplayAll()
+
+        self.assertRaises(exception.InstanceFaultRollback,
+                          vmops._migrate_disk_resizing_down, self.context,
+                          instance, dest, instance_type, vm_ref, sr_path)
+
+    def test_resize_ensure_vm_is_shutdown_cleanly(self):
+        conn = xenapi_conn.XenAPIDriver(fake.FakeVirtAPI(), False)
+        vmops = conn._vmops
+        fake_instance = {'uuid': 'uuid'}
+
+        self.mox.StubOutWithMock(vm_utils, 'is_vm_shutdown')
+        self.mox.StubOutWithMock(vm_utils, 'clean_shutdown_vm')
+        self.mox.StubOutWithMock(vm_utils, 'hard_shutdown_vm')
+
+        vm_utils.is_vm_shutdown(vmops._session, "ref").AndReturn(False)
+        vm_utils.clean_shutdown_vm(vmops._session, fake_instance,
+            "ref").AndReturn(True)
+
+        self.mox.ReplayAll()
+
+        vmops._resize_ensure_vm_is_shutdown(fake_instance, "ref")
+
+    def test_resize_ensure_vm_is_shutdown_forced(self):
+        conn = xenapi_conn.XenAPIDriver(fake.FakeVirtAPI(), False)
+        vmops = conn._vmops
+        fake_instance = {'uuid': 'uuid'}
+
+        self.mox.StubOutWithMock(vm_utils, 'is_vm_shutdown')
+        self.mox.StubOutWithMock(vm_utils, 'clean_shutdown_vm')
+        self.mox.StubOutWithMock(vm_utils, 'hard_shutdown_vm')
+
+        vm_utils.is_vm_shutdown(vmops._session, "ref").AndReturn(False)
+        vm_utils.clean_shutdown_vm(vmops._session, fake_instance,
+            "ref").AndReturn(False)
+        vm_utils.hard_shutdown_vm(vmops._session, fake_instance,
+            "ref").AndReturn(True)
+
+        self.mox.ReplayAll()
+
+        vmops._resize_ensure_vm_is_shutdown(fake_instance, "ref")
+
+    def test_resize_ensure_vm_is_shutdown_fails(self):
+        conn = xenapi_conn.XenAPIDriver(fake.FakeVirtAPI(), False)
+        vmops = conn._vmops
+        fake_instance = {'uuid': 'uuid'}
+
+        self.mox.StubOutWithMock(vm_utils, 'is_vm_shutdown')
+        self.mox.StubOutWithMock(vm_utils, 'clean_shutdown_vm')
+        self.mox.StubOutWithMock(vm_utils, 'hard_shutdown_vm')
+
+        vm_utils.is_vm_shutdown(vmops._session, "ref").AndReturn(False)
+        vm_utils.clean_shutdown_vm(vmops._session, fake_instance,
+            "ref").AndReturn(False)
+        vm_utils.hard_shutdown_vm(vmops._session, fake_instance,
+            "ref").AndReturn(False)
+
+        self.mox.ReplayAll()
+
+        self.assertRaises(exception.ResizeError,
+            vmops._resize_ensure_vm_is_shutdown, fake_instance, "ref")
+
+    def test_resize_ensure_vm_is_shutdown_already_shutdown(self):
+        conn = xenapi_conn.XenAPIDriver(fake.FakeVirtAPI(), False)
+        vmops = conn._vmops
+        fake_instance = {'uuid': 'uuid'}
+
+        self.mox.StubOutWithMock(vm_utils, 'is_vm_shutdown')
+        self.mox.StubOutWithMock(vm_utils, 'clean_shutdown_vm')
+        self.mox.StubOutWithMock(vm_utils, 'hard_shutdown_vm')
+
+        vm_utils.is_vm_shutdown(vmops._session, "ref").AndReturn(True)
+
+        self.mox.ReplayAll()
+
+        vmops._resize_ensure_vm_is_shutdown(fake_instance, "ref")
+
 
 class XenAPIImageTypeTestCase(test.TestCase):
     """Test ImageType class."""
diff --git a/nova/tests/virt/xenapi/test_vm_utils.py b/nova/tests/virt/xenapi/test_vm_utils.py
index 3e532a1c7..2180f75f9 100644
--- a/nova/tests/virt/xenapi/test_vm_utils.py
+++ b/nova/tests/virt/xenapi/test_vm_utils.py
@@ -278,3 +278,89 @@ class FetchVhdImageTestCase(test.TestCase):
             self.context, self.session, self.instance, self.image_id)
 
         self.mox.VerifyAll()
+
+
+class ResizeHelpersTestCase(test.TestCase):
+    def test_get_min_sectors(self):
+        self.mox.StubOutWithMock(utils, 'execute')
+
+        utils.execute('resize2fs', '-P', "fakepath",
+            run_as_root=True).AndReturn(("size is: 42", ""))
+
+        self.mox.ReplayAll()
+
+        result = vm_utils._get_min_sectors("fakepath")
+        self.assertEquals(42 * 4096 / 512, result)
+
+    def test_repair_filesystem(self):
+        self.mox.StubOutWithMock(utils, 'execute')
+
+        utils.execute('e2fsck', '-f', "-y", "fakepath",
+            run_as_root=True, check_exit_code=[0, 1, 2]).AndReturn(
+                ("size is: 42", ""))
+
+        self.mox.ReplayAll()
+
+        vm_utils._repair_filesystem("fakepath")
+
+    def _call_tune2fs_remove_journal(self, path):
+        utils.execute("tune2fs", "-O ^has_journal", path, run_as_root=True)
+
+    def _call_tune2fs_add_journal(self, path):
+        utils.execute("tune2fs", "-j", path, run_as_root=True)
+
+    def _call_parted(self, path, start, end):
+        utils.execute('parted', '--script', path, 'rm', '1',
+            run_as_root=True)
+        utils.execute('parted', '--script', path, 'mkpart',
+            'primary', '%ds' % start, '%ds' % end, run_as_root=True)
+
+    def test_resize_part_and_fs_down_succeeds(self):
+        self.mox.StubOutWithMock(vm_utils, "_repair_filesystem")
+        self.mox.StubOutWithMock(utils, 'execute')
+        self.mox.StubOutWithMock(vm_utils, "_get_min_sectors")
+
+        dev_path = "/dev/fake"
+        partition_path = "%s1" % dev_path
+        vm_utils._repair_filesystem(partition_path)
+        self._call_tune2fs_remove_journal(partition_path)
+        vm_utils._get_min_sectors(partition_path).AndReturn(9)
+        utils.execute("resize2fs", partition_path, "10s", run_as_root=True)
+        self._call_parted(dev_path, 0, 9)
+        self._call_tune2fs_add_journal(partition_path)
+
+        self.mox.ReplayAll()
+
+        vm_utils._resize_part_and_fs("fake", 0, 20, 10)
+
+    def test_resize_part_and_fs_down_fails_disk_too_big(self):
+        self.mox.StubOutWithMock(vm_utils, "_repair_filesystem")
+        self.mox.StubOutWithMock(utils, 'execute')
+        self.mox.StubOutWithMock(vm_utils, "_get_min_sectors")
+
+        dev_path = "/dev/fake"
+        partition_path = "%s1" % dev_path
+        vm_utils._repair_filesystem(partition_path)
+        self._call_tune2fs_remove_journal(partition_path)
+        vm_utils._get_min_sectors(partition_path).AndReturn(10)
+
+        self.mox.ReplayAll()
+
+        self.assertRaises(exception.ResizeError,
+            vm_utils._resize_part_and_fs, "fake", 0, 20, 10)
+
+    def test_resize_part_and_fs_up_succeeds(self):
+        self.mox.StubOutWithMock(vm_utils, "_repair_filesystem")
+        self.mox.StubOutWithMock(utils, 'execute')
+
+        dev_path = "/dev/fake"
+        partition_path = "%s1" % dev_path
+        vm_utils._repair_filesystem(partition_path)
+        self._call_tune2fs_remove_journal(partition_path)
+        self._call_parted(dev_path, 0, 29)
+        utils.execute("resize2fs", partition_path, run_as_root=True)
+        self._call_tune2fs_add_journal(partition_path)
+
+        self.mox.ReplayAll()
+
+        vm_utils._resize_part_and_fs("fake", 0, 20, 30)
diff --git a/nova/tests/virt/xenapi/test_volumeops.py b/nova/tests/virt/xenapi/test_volumeops.py
index 7ec9eb1ea..5d4344bb0 100644
--- a/nova/tests/virt/xenapi/test_volumeops.py
+++ b/nova/tests/virt/xenapi/test_volumeops.py
@@ -33,7 +33,7 @@ class VolumeAttachTestCase(test.TestCase):
         ops = volumeops.VolumeOps('session')
         self.mox.StubOutWithMock(volumeops.vm_utils, 'lookup')
         self.mox.StubOutWithMock(volumeops.vm_utils, 'find_vbd_by_number')
-        self.mox.StubOutWithMock(volumeops.vm_utils, '_is_vm_shutdown')
+        self.mox.StubOutWithMock(volumeops.vm_utils, 'is_vm_shutdown')
         self.mox.StubOutWithMock(volumeops.vm_utils, 'unplug_vbd')
         self.mox.StubOutWithMock(volumeops.vm_utils, 'destroy_vbd')
         self.mox.StubOutWithMock(volumeops.volume_utils, 'get_device_number')
@@ -49,7 +49,7 @@ class VolumeAttachTestCase(test.TestCase):
         volumeops.vm_utils.find_vbd_by_number(
             'session', 'vmref', 'devnumber').AndReturn('vbdref')
 
-        volumeops.vm_utils._is_vm_shutdown('session', 'vmref').AndReturn(
+        volumeops.vm_utils.is_vm_shutdown('session', 'vmref').AndReturn(
             False)
 
         volumeops.vm_utils.unplug_vbd('session', 'vbdref')
diff --git a/nova/virt/xenapi/driver.py b/nova/virt/xenapi/driver.py
index 02b849a99..5bc1a3049 100755
--- a/nova/virt/xenapi/driver.py
+++ b/nova/virt/xenapi/driver.py
@@ -239,17 +239,8 @@ class XenAPIDriver(driver.ComputeDriver):
         """Transfers the VHD of a running instance to another host, then shuts
         off the instance copies over the COW disk"""
         # NOTE(vish): Xen currently does not use network info.
-        rv = self._vmops.migrate_disk_and_power_off(context, instance,
-                                                    dest, instance_type)
-        block_device_mapping = driver.block_device_info_get_mapping(
-                block_device_info)
-        name_label = self._vmops._get_orig_vm_name_label(instance)
-        for vol in block_device_mapping:
-            connection_info = vol['connection_info']
-            mount_device = vol['mount_device'].rpartition("/")[2]
-            self._volumeops.detach_volume(connection_info,
-                    name_label, mount_device)
-        return rv
+        return self._vmops.migrate_disk_and_power_off(context, instance,
+                    dest, instance_type, block_device_info)
 
     def suspend(self, instance):
         """suspend the specified instance."""
diff --git a/nova/virt/xenapi/vm_utils.py b/nova/virt/xenapi/vm_utils.py
index 4cd2b2ab5..3f2c6835f 100644
--- a/nova/virt/xenapi/vm_utils.py
+++ b/nova/virt/xenapi/vm_utils.py
@@ -286,7 +286,7 @@ def destroy_vm(session, instance, vm_ref):
 
 
 def clean_shutdown_vm(session, instance, vm_ref):
-    if _is_vm_shutdown(session, vm_ref):
+    if is_vm_shutdown(session, vm_ref):
         LOG.warn(_("VM already halted, skipping shutdown..."),
                  instance=instance)
         return False
@@ -301,7 +301,7 @@ def clean_shutdown_vm(session, instance, vm_ref):
 
 
 def hard_shutdown_vm(session, instance, vm_ref):
-    if _is_vm_shutdown(session, vm_ref):
+    if is_vm_shutdown(session, vm_ref):
         LOG.warn(_("VM already halted, skipping shutdown..."),
                  instance=instance)
         return False
@@ -315,7 +315,7 @@ def hard_shutdown_vm(session, instance, vm_ref):
     return True
 
 
-def _is_vm_shutdown(session, vm_ref):
+def is_vm_shutdown(session, vm_ref):
     vm_rec = session.call_xenapi("VM.get_record", vm_ref)
     state = compile_info(vm_rec)['state']
     if state == power_state.SHUTDOWN:
@@ -2078,6 +2078,21 @@ def _write_partition(virtual_size, dev):
     LOG.debug(_('Writing partition table %s done.'), dev_path)
 
 
+def _get_min_sectors(partition_path, block_size=4096):
+    stdout, _err = utils.execute('resize2fs', '-P', partition_path,
+        run_as_root=True)
+    min_size_blocks = long(re.sub('[^0-9]', '', stdout))
+    min_size_bytes = min_size_blocks * block_size
+    return min_size_bytes / SECTOR_SIZE
+
+
+def _repair_filesystem(partition_path):
+    # Exit Code 1 = File system errors corrected
+    #           2 = File system errors corrected, system needs a reboot
+    utils.execute('e2fsck', '-f', '-y', partition_path, run_as_root=True,
+        check_exit_code=[0, 1, 2])
+
+
 def _resize_part_and_fs(dev, start, old_sectors, new_sectors):
     """Resize partition and fileystem.
 
@@ -2091,10 +2106,7 @@ def _resize_part_and_fs(dev, start, old_sectors, new_sectors):
     partition_path = utils.make_dev_path(dev, partition=1)
 
     # Replay journal if FS wasn't cleanly unmounted
-    # Exit Code 1 = File system errors corrected
-    #           2 = File system errors corrected, system needs a reboot
-    utils.execute('e2fsck', '-f', '-y', partition_path, run_as_root=True,
-                  check_exit_code=[0, 1, 2])
+    _repair_filesystem(partition_path)
 
     # Remove ext3 journal (making it ext2)
     utils.execute('tune2fs', '-O ^has_journal', partition_path,
@@ -2102,6 +2114,12 @@ def _resize_part_and_fs(dev, start, old_sectors, new_sectors):
 
     if new_sectors < old_sectors:
         # Resizing down, resize filesystem before partition resize
+        min_sectors = _get_min_sectors(partition_path)
+        if min_sectors >= new_sectors:
+            reason = _('Resize down not allowed because minimum '
+                       'filesystem sectors %(min_sectors)d is too big '
+                       'for target sectors %(new_sectors)d')
+            raise exception.ResizeError(reason=(reason % locals()))
         utils.execute('resize2fs', partition_path, '%ds' % size,
                       run_as_root=True)
 
diff --git a/nova/virt/xenapi/vmops.py b/nova/virt/xenapi/vmops.py
index 1dabe271d..034556809 100644
--- a/nova/virt/xenapi/vmops.py
+++ b/nova/virt/xenapi/vmops.py
@@ -209,6 +209,9 @@ class VMOps(object):
         return nova_uuids
 
     def confirm_migration(self, migration, instance, network_info):
+        self._destroy_orig_vm(instance, network_info)
+
+    def _destroy_orig_vm(self, instance, network_info):
         name_label = self._get_orig_vm_name_label(instance)
         vm_ref = vm_utils.lookup(self._session, name_label)
         return self._destroy(instance, vm_ref, network_info=network_info)
@@ -227,6 +230,9 @@ class VMOps(object):
                                           hotplug=False)
 
     def finish_revert_migration(self, instance, block_device_info=None):
+        self._restore_orig_vm_and_cleanup_orphan(instance, block_device_info)
+
+    def _restore_orig_vm_and_cleanup_orphan(self, instance, block_device_info):
         # NOTE(sirp): the original vm was suffixed with '-orig'; find it using
         # the old suffix, remove the suffix, then power it back on.
         name_label = self._get_orig_vm_name_label(instance)
@@ -797,53 +803,84 @@ class VMOps(object):
         self._virtapi.instance_update(context, instance['uuid'],
                                       {'progress': progress})
 
+    def _resize_ensure_vm_is_shutdown(self, instance, vm_ref):
+        if vm_utils.is_vm_shutdown(self._session, vm_ref):
+            LOG.debug(_("VM was already shutdown."), instance=instance)
+            return
+
+        if not vm_utils.clean_shutdown_vm(self._session, instance, vm_ref):
+            LOG.debug(_("Clean shutdown did not complete successfully, "
+                        "trying hard shutdown."), instance=instance)
+            if not vm_utils.hard_shutdown_vm(self._session, instance, vm_ref):
+                raise exception.ResizeError(
+                    reason=_("Unable to terminate instance."))
+
     def _migrate_disk_resizing_down(self, context, instance, dest,
                                     instance_type, vm_ref, sr_path):
-        # 1. NOOP since we're not transmitting the base-copy separately
-        self._update_instance_progress(context, instance,
-                                       step=1,
-                                       total_steps=RESIZE_TOTAL_STEPS)
+        if not instance['auto_disk_config']:
+            reason = _('Resize down not allowed without auto_disk_config')
+            raise exception.ResizeError(reason=reason)
 
-        vdi_ref, vm_vdi_rec = vm_utils.get_vdi_for_vm_safely(
-                self._session, vm_ref)
-        vdi_uuid = vm_vdi_rec['uuid']
+        step = make_step_decorator(context, instance,
+                                   self._virtapi.instance_update)
 
-        old_gb = instance['root_gb']
-        new_gb = instance_type['root_gb']
-        LOG.debug(_("Resizing down VDI %(vdi_uuid)s from "
-                    "%(old_gb)dGB to %(new_gb)dGB"), locals(),
-                  instance=instance)
+        @step
+        def fake_step_to_match_resizing_up():
+            pass
 
-        # 2. Power down the instance before resizing
-        if not vm_utils.clean_shutdown_vm(self._session, instance, vm_ref):
-            LOG.debug(_("Clean shutdown did not complete successfully, "
-                        "trying hard shutdown."), instance=instance)
-            vm_utils.hard_shutdown_vm(self._session, instance, vm_ref)
-        self._update_instance_progress(context, instance,
-                                       step=2,
-                                       total_steps=RESIZE_TOTAL_STEPS)
+        @step
+        def rename_and_power_off_vm(undo_mgr):
+            self._resize_ensure_vm_is_shutdown(instance, vm_ref)
+            self._apply_orig_vm_name_label(instance, vm_ref)
 
-        # 3. Copy VDI, resize partition and filesystem, forget VDI,
-        # truncate VHD
-        new_ref, new_uuid = vm_utils.resize_disk(self._session,
-                                                 instance,
-                                                 vdi_ref,
-                                                 instance_type)
-        self._update_instance_progress(context, instance,
-                                       step=3,
-                                       total_steps=RESIZE_TOTAL_STEPS)
+            def restore_orig_vm():
+                # Do not need to restore block devices, not yet been removed
+                self._restore_orig_vm_and_cleanup_orphan(instance, None)
 
-        # 4. Transfer the new VHD
-        self._migrate_vhd(instance, new_uuid, dest, sr_path, 0)
-        self._update_instance_progress(context, instance,
-                                       step=4,
-                                       total_steps=RESIZE_TOTAL_STEPS)
+            undo_mgr.undo_with(restore_orig_vm)
+
+        @step
+        def create_copy_vdi_and_resize(undo_mgr, old_vdi_ref):
+            new_vdi_ref, new_vdi_uuid = vm_utils.resize_disk(self._session,
+                instance, old_vdi_ref, instance_type)
 
-        # Clean up VDI now that it's been copied
-        vm_utils.destroy_vdi(self._session, new_ref)
+            def cleanup_vdi_copy():
+                vm_utils.destroy_vdi(self._session, new_vdi_ref)
+
+            undo_mgr.undo_with(cleanup_vdi_copy)
+
+            return new_vdi_ref, new_vdi_uuid
+
+        @step
+        def transfer_vhd_to_dest(new_vdi_ref, new_vdi_uuid):
+            self._migrate_vhd(instance, new_vdi_uuid, dest, sr_path, 0)
+            # Clean up VDI now that it's been copied
+            vm_utils.destroy_vdi(self._session, new_vdi_ref)
+
+        @step
+        def fake_step_to_be_executed_by_finish_migration():
+            pass
+
+        undo_mgr = utils.UndoManager()
+        try:
+            fake_step_to_match_resizing_up()
+            rename_and_power_off_vm(undo_mgr)
+            old_vdi_ref, _ignore = vm_utils.get_vdi_for_vm_safely(
+                self._session, vm_ref)
+            new_vdi_ref, new_vdi_uuid = create_copy_vdi_and_resize(
+                undo_mgr, old_vdi_ref)
+            transfer_vhd_to_dest(new_vdi_ref, new_vdi_uuid)
+        except Exception, error:
+            msg = _("_migrate_disk_resizing_down failed. "
+                    "Restoring orig vm due_to: %{exception}.")
+            LOG.exception(msg, instance=instance)
+            undo_mgr._rollback()
+            raise exception.InstanceFaultRollback(error)
 
     def _migrate_disk_resizing_up(self, context, instance, dest, vm_ref,
                                   sr_path):
+        self._apply_orig_vm_name_label(instance, vm_ref)
+
         # 1. Create Snapshot
         label = "%s-snapshot" % instance['name']
         with vm_utils.snapshot_attached_here(
@@ -865,10 +902,7 @@ class VMOps(object):
                                                total_steps=RESIZE_TOTAL_STEPS)
 
         # 3. Now power down the instance
-        if not vm_utils.clean_shutdown_vm(self._session, instance, vm_ref):
-            LOG.debug(_("Clean shutdown did not complete successfully, "
-                        "trying hard shutdown."), instance=instance)
-            vm_utils.hard_shutdown_vm(self._session, instance, vm_ref)
+        self._resize_ensure_vm_is_shutdown(instance, vm_ref)
         self._update_instance_progress(context, instance,
                                        step=3,
                                        total_steps=RESIZE_TOTAL_STEPS)
@@ -882,8 +916,15 @@ class VMOps(object):
                                        step=4,
                                        total_steps=RESIZE_TOTAL_STEPS)
 
+    def _apply_orig_vm_name_label(self, instance, vm_ref):
+        # NOTE(sirp): in case we're resizing to the same host (for dev
+        # purposes), apply a suffix to name-label so the two VM records
+        # extant until a confirm_resize don't collide.
+        name_label = self._get_orig_vm_name_label(instance)
+        vm_utils.set_vm_name_label(self._session, vm_ref, name_label)
+
     def migrate_disk_and_power_off(self, context, instance, dest,
-                                   instance_type):
+                                   instance_type, block_device_info):
         """Copies a VHD from one host machine to another, possibly
         resizing filesystem before hand.
 
@@ -891,23 +932,17 @@ class VMOps(object):
         :param dest: the destination host machine.
         :param instance_type: instance_type to resize to
         """
-        vm_ref = self._get_vm_opaque_ref(instance)
-        sr_path = vm_utils.get_sr_path(self._session)
-        resize_down = instance['root_gb'] > instance_type['root_gb']
-        if resize_down and not instance['auto_disk_config']:
-            reason = _('Resize down not allowed without auto_disk_config')
-            raise exception.ResizeError(reason=reason)
-
         # 0. Zero out the progress to begin
         self._update_instance_progress(context, instance,
                                        step=0,
                                        total_steps=RESIZE_TOTAL_STEPS)
 
-        # NOTE(sirp): in case we're resizing to the same host (for dev
-        # purposes), apply a suffix to name-label so the two VM records
-        # extant until a confirm_resize don't collide.
-        name_label = self._get_orig_vm_name_label(instance)
-        vm_utils.set_vm_name_label(self._session, vm_ref, name_label)
+        vm_ref = self._get_vm_opaque_ref(instance)
+        sr_path = vm_utils.get_sr_path(self._session)
+
+        old_gb = instance['root_gb']
+        new_gb = instance_type['root_gb']
+        resize_down = old_gb > new_gb
 
         if resize_down:
             self._migrate_disk_resizing_down(
@@ -916,12 +951,24 @@ class VMOps(object):
             self._migrate_disk_resizing_up(
                     context, instance, dest, vm_ref, sr_path)
 
+        self._detach_block_devices_from_orig_vm(instance, block_device_info)
+
         # NOTE(sirp): disk_info isn't used by the xenapi driver, instead it
         # uses a staging-area (/images/instance<uuid>) and sequence-numbered
         # VHDs to figure out how to reconstruct the VDI chain after syncing
         disk_info = {}
         return disk_info
 
+    def _detach_block_devices_from_orig_vm(self, instance, block_device_info):
+        block_device_mapping = virt_driver.block_device_info_get_mapping(
+                block_device_info)
+        name_label = self._get_orig_vm_name_label(instance)
+        for vol in block_device_mapping:
+            connection_info = vol['connection_info']
+            mount_device = vol['mount_device'].rpartition("/")[2]
+            self._volumeops.detach_volume(connection_info, name_label,
+                                          mount_device)
+
     def _resize_instance(self, instance, root_vdi):
         """Resize an instances root disk."""
 
diff --git a/nova/virt/xenapi/volumeops.py b/nova/virt/xenapi/volumeops.py
index 5e650f55d..3560edbc1 100644
--- a/nova/virt/xenapi/volumeops.py
+++ b/nova/virt/xenapi/volumeops.py
@@ -141,7 +141,7 @@ class VolumeOps(object):
             return
 
         # Unplug VBD if we're NOT shutdown
-        unplug = not vm_utils._is_vm_shutdown(self._session, vm_ref)
+        unplug = not vm_utils.is_vm_shutdown(self._session, vm_ref)
         self._detach_vbd(vbd_ref, unplug=unplug)
 
         LOG.info(_('Mountpoint %(mountpoint)s detached from instance'
@@ -171,7 +171,7 @@ class VolumeOps(object):
         # Generally speaking, detach_all will be called with VM already
         # shutdown; however if it's still running, we can still perform the
         # operation by unplugging the VBD first.
-        unplug = not vm_utils._is_vm_shutdown(self._session, vm_ref)
+        unplug = not vm_utils.is_vm_shutdown(self._session, vm_ref)
 
         vbd_refs = self._get_all_volume_vbd_refs(vm_ref)
         for vbd_ref in vbd_refs: