diff --git a/cinder/scheduler/manager.py b/cinder/scheduler/manager.py
index ab1c3d5e714..86611782204 100644
--- a/cinder/scheduler/manager.py
+++ b/cinder/scheduler/manager.py
@@ -348,9 +348,12 @@ class SchedulerManager(manager.CleanableManager, manager.Manager):
 
         filter_properties['new_size'] = new_size
         try:
-            self.driver.backend_passes_filters(context,
-                                               volume.service_topic_queue,
-                                               request_spec, filter_properties)
+            backend_state = self.driver.backend_passes_filters(
+                context,
+                volume.service_topic_queue,
+                request_spec, filter_properties)
+            backend_state.consume_from_volume(
+                {'size': new_size - volume.size})
             volume_rpcapi.VolumeAPI().extend_volume(context, volume, new_size,
                                                     reservations)
         except exception.NoValidBackend as ex:
diff --git a/cinder/tests/unit/scheduler/test_scheduler.py b/cinder/tests/unit/scheduler/test_scheduler.py
index 1e548f4e9ec..5c808b8ece8 100644
--- a/cinder/tests/unit/scheduler/test_scheduler.py
+++ b/cinder/tests/unit/scheduler/test_scheduler.py
@@ -32,6 +32,7 @@ from cinder.scheduler import manager
 from cinder import test
 from cinder.tests.unit import fake_constants as fake
 from cinder.tests.unit import fake_volume
+from cinder.tests.unit.scheduler import fakes as fake_scheduler
 from cinder.tests.unit import utils as tests_utils
 
 CONF = cfg.CONF
@@ -100,6 +101,45 @@ class SchedulerManagerTestCase(test.TestCase):
 
         mock_clean.assert_called_once_with(self.context)
 
+    @mock.patch('cinder.scheduler.driver.Scheduler.backend_passes_filters')
+    @mock.patch(
+        'cinder.scheduler.host_manager.BackendState.consume_from_volume')
+    @mock.patch('cinder.volume.rpcapi.VolumeAPI.extend_volume')
+    def test_extend_volume(self, mock_extend,
+                           mock_consume, mock_backend_passes):
+        volume = fake_volume.fake_volume_obj(self.context, **{'size': 1})
+        fake_backend = fake_scheduler.FakeBackendState('host1', {})
+        mock_backend_passes.return_value = fake_backend
+
+        self.manager.extend_volume(self.context, volume, 2, 'fake_reservation')
+
+        mock_consume.assert_called_once_with({'size': 1})
+        mock_extend.assert_called_once_with(
+            self.context, volume, 2, 'fake_reservation')
+
+    @mock.patch('cinder.scheduler.driver.Scheduler.backend_passes_filters')
+    @mock.patch(
+        'cinder.scheduler.host_manager.BackendState.consume_from_volume')
+    @mock.patch('cinder.volume.rpcapi.VolumeAPI.extend_volume')
+    @mock.patch('cinder.quota.QUOTAS.rollback')
+    def test_extend_volume_no_valid_host(self, mock_rollback, mock_extend,
+                                         mock_consume, mock_backend_passes):
+        volume = fake_volume.fake_volume_obj(self.context, **{'size': 1})
+        no_valid_backend = exception.NoValidBackend(reason='')
+        mock_backend_passes.side_effect = [no_valid_backend]
+
+        with mock.patch.object(self.manager,
+                               '_set_volume_state_and_notify') as mock_notify:
+            self.manager.extend_volume(self.context, volume, 2,
+                                       'fake_reservation')
+            mock_notify.assert_called_once_with(
+                'extend_volume', {'volume_state': {'status': 'available'}},
+                self.context, no_valid_backend, None)
+            mock_rollback.assert_called_once_with(
+                self.context, 'fake_reservation', project_id=volume.project_id)
+            mock_consume.assert_not_called()
+            mock_extend.assert_not_called()
+
     @mock.patch('cinder.quota.QuotaEngine.expire')
     def test_clean_expired_reservation(self, mock_clean):
 
diff --git a/releasenotes/notes/bug-1706888-update-backend-when-extending-3e4a9831a0w29d68.yaml b/releasenotes/notes/bug-1706888-update-backend-when-extending-3e4a9831a0w29d68.yaml
new file mode 100644
index 00000000000..650e88c9d36
--- /dev/null
+++ b/releasenotes/notes/bug-1706888-update-backend-when-extending-3e4a9831a0w29d68.yaml
@@ -0,0 +1,3 @@
+---
+fixes:
+  - Update backend state in scheduler when extending volume.
\ No newline at end of file