Rollback the quota_usages table when failed to create a incremental backup

If we firstly create a incremental backup without parent backup
or using unavailable backup file, like execute the command:
``cinder backup-create --name test_backup --incremental
2e3d9d0b-6b33-4cfe-a7c2-656415ee6f61``.

To satisfy one of the above reasons, we will be received an error
info: "Invalid backup: No backups available to do an incremental
backup. (HTTP 400)". But the reserved value of the ``quota_usages``
table has been updated, so we need to roll back the ``quota_usages``
table. Otherwise, after repetitive operation for many times,
create backup will be failed.

Co-Authored-By: Brin Zhang <zhangbailin@inspur.com>

Closes-Bug: #1809323
Change-Id: I1870633a5505bdb60d529fbda3147378b75e2b07

cinder/backup/api.py

@@ -274,6 +274,7 @@ class API(base.Base):
                                          < snapshot['created_at']))
                     else datetime(1, 1, 1, 1, 1, 1, tzinfo=timezone('UTC')))
             else:
+                QUOTAS.rollback(context, reservations)
                 msg = _('No backups available to do an incremental backup.')
                 raise exception.InvalidBackup(reason=msg)
 
@@ -281,6 +282,7 @@ class API(base.Base):
         if latest_backup:
             parent_id = latest_backup.id
             if latest_backup['status'] != fields.BackupStatus.AVAILABLE:
+                QUOTAS.rollback(context, reservations)
                 msg = _('The parent backup must be available for '
                         'incremental backup.')
                 raise exception.InvalidBackup(reason=msg)

cinder/tests/unit/backup/test_backup.py

@@ -39,6 +39,7 @@ from cinder.objects import fields
 from cinder import quota
 from cinder import test
 from cinder.tests import fake_driver
+from cinder.tests.unit.api.v2 import fakes as v2_fakes
 from cinder.tests.unit import fake_constants as fake
 from cinder.tests.unit import utils
 from cinder.volume import rpcapi as volume_rpcapi
@@ -2168,3 +2169,59 @@ class BackupAPITestCase(BaseBackupTest):
         mock_reserve.assert_called_with(
             self.ctxt, backups=1, backup_gigabytes=1)
         mock_rollback.assert_called_with(self.ctxt, "fake_reservation")
+
+    @mock.patch('cinder.db.backup_get_all_by_volume')
+    @mock.patch('cinder.backup.rpcapi.BackupAPI.create_backup')
+    @mock.patch.object(api.API, '_get_available_backup_service_host',
+                       return_value='fake_host')
+    @mock.patch.object(quota.QUOTAS, 'rollback')
+    @mock.patch.object(quota.QUOTAS, 'reserve')
+    def test_create_backup_failed_with_empty_backup_objects(
+            self, mock_reserve, mock_rollback, mock_get_service,
+            mock_create, mock_get_backups):
+        mock_get_backups.return_value = [v2_fakes.fake_backup('fake-1')]
+        backups = objects.BackupList.get_all_by_volume(self.ctxt,
+                                                       fake.VOLUME_ID)
+        backups.objects = []
+        is_incremental = True
+        self.ctxt.user_id = 'fake_user'
+        self.ctxt.project_id = 'fake_project'
+        mock_reserve.return_value = 'fake_reservation'
+
+        volume_id = self._create_volume_db_entry(status='available',
+                                                 host='testhost#rbd',
+                                                 size=1)
+        self.assertRaises(exception.InvalidBackup,
+                          self.api.create,
+                          self.ctxt,
+                          None, None,
+                          volume_id, None,
+                          incremental=is_incremental)
+        mock_rollback.assert_called_with(self.ctxt, "fake_reservation")
+
+    @mock.patch('cinder.db.backup_get_all_by_volume',
+                return_value=[v2_fakes.fake_backup('fake-1')])
+    @mock.patch('cinder.backup.rpcapi.BackupAPI.create_backup')
+    @mock.patch.object(api.API, '_get_available_backup_service_host',
+                       return_value='fake_host')
+    @mock.patch.object(quota.QUOTAS, 'rollback')
+    @mock.patch.object(quota.QUOTAS, 'reserve')
+    def test_create_backup_failed_with_backup_status_not_available(
+            self, mock_reserve, mock_rollback, mock_get_service,
+            mock_createi, mock_get_backups):
+
+        is_incremental = True
+        self.ctxt.user_id = 'fake_user'
+        self.ctxt.project_id = 'fake_project'
+        mock_reserve.return_value = 'fake_reservation'
+
+        volume_id = self._create_volume_db_entry(status='available',
+                                                 host='testhost#rbd',
+                                                 size=1)
+        self.assertRaises(exception.InvalidBackup,
+                          self.api.create,
+                          self.ctxt,
+                          None, None,
+                          volume_id, None,
+                          incremental=is_incremental)
+        mock_rollback.assert_called_with(self.ctxt, "fake_reservation")

releasenotes/notes/bug-1809323-fix-invalid-backup-4a341dc362ded88e.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Now cinder will be rollback the ``quota_usages`` table when failed
+    to create an incremental backup if there doesn't exist a parent
+    backup or the backup is not in available state.