Merge "Add support for RBD fast-diff feature for backups stored in Ceph"

cinder/backup/drivers/ceph.py

@@ -243,6 +243,11 @@ class CephBackupDriver(driver.BackupDriver):
         """Determine if journaling is supported by our version of librbd."""
         return hasattr(self.rbd, 'RBD_FEATURE_JOURNALING')
 
+    @property
+    def _supports_fast_diff(self):
+        """Determine if fast-diff is supported by our version of librbd."""
+        return hasattr(self.rbd, 'RBD_FEATURE_FAST_DIFF')
+
     def _get_rbd_support(self):
         """Determine RBD features supported by our version of librbd."""
         old_format = True
@@ -254,24 +259,22 @@ class CephBackupDriver(driver.BackupDriver):
             old_format = False
             features |= self.rbd.RBD_FEATURE_STRIPINGV2
 
-        # journaling requires exclusive_lock; check both together
         if CONF.backup_ceph_image_journals:
-            if self._supports_exclusive_lock and self._supports_journaling:
+            LOG.debug("RBD journaling supported by backend and requested "
+                      "via config. Enabling it together with "
+                      "exclusive-lock")
             old_format = False
             features |= (self.rbd.RBD_FEATURE_EXCLUSIVE_LOCK |
                          self.rbd.RBD_FEATURE_JOURNALING)
-            else:
-                # FIXME (tasker): when the backup manager supports loading the
-                #   driver during its initialization, this exception should be
-                #   moved to the driver's initialization so that it can stop
-                #   the service from starting when the underyling RBD does not
-                #   support the requested features.
-                LOG.error("RBD journaling not supported - unable to "
-                          "support per image mirroring in backup pool")
-                raise exception.BackupInvalidCephArgs(
-                    _("Image Journaling set but RBD backend does "
-                      "not support journaling")
-                )
+
+        # NOTE(christian_rohmann): Check for fast-diff support and enable it
+        if self._supports_fast_diff:
+            LOG.debug("RBD also supports fast-diff, enabling it "
+                      "together with exclusive-lock and object-map")
+            old_format = False
+            features |= (self.rbd.RBD_FEATURE_EXCLUSIVE_LOCK |
+                         self.rbd.RBD_FEATURE_OBJECT_MAP |
+                         self.rbd.RBD_FEATURE_FAST_DIFF)
 
         return (old_format, features)
 
@@ -293,6 +296,16 @@ class CephBackupDriver(driver.BackupDriver):
         with rbd_driver.RADOSClient(self, self._ceph_backup_pool):
             pass
 
+        # NOTE(christian_rohmann): Check features required for journaling
+        if CONF.backup_ceph_image_journals:
+            if not self._supports_exclusive_lock and self._supports_journaling:
+                LOG.error("RBD journaling not supported - unable to "
+                          "support per image mirroring in backup pool")
+                raise exception.BackupInvalidCephArgs(
+                    _("Image Journaling set but RBD backend does "
+                      "not support journaling")
+                )
+
     def _connect_to_rados(self, pool=None):
         """Establish connection to the backup Ceph cluster."""
         client = eventlet.tpool.Proxy(self.rados.Rados(

cinder/tests/unit/backup/drivers/test_backup_ceph.py

@@ -235,11 +235,15 @@ class BackupCephTestCase(test.TestCase):
         del self.service.rbd.RBD_FEATURE_STRIPINGV2
         del self.service.rbd.RBD_FEATURE_EXCLUSIVE_LOCK
         del self.service.rbd.RBD_FEATURE_JOURNALING
+        del self.service.rbd.RBD_FEATURE_OBJECT_MAP
+        del self.service.rbd.RBD_FEATURE_FAST_DIFF
         self.assertFalse(hasattr(self.service.rbd, 'RBD_FEATURE_LAYERING'))
         self.assertFalse(hasattr(self.service.rbd, 'RBD_FEATURE_STRIPINGV2'))
         self.assertFalse(hasattr(self.service.rbd,
                                  'RBD_FEATURE_EXCLUSIVE_LOCK'))
         self.assertFalse(hasattr(self.service.rbd, 'RBD_FEATURE_JOURNALING'))
+        self.assertFalse(hasattr(self.service.rbd, 'RBD_FEATURE_OBJECT_MAP'))
+        self.assertFalse(hasattr(self.service.rbd, 'RBD_FEATURE_FAST_DIFF'))
 
         oldformat, features = self.service._get_rbd_support()
         self.assertTrue(oldformat)
@@ -279,6 +283,17 @@ class BackupCephTestCase(test.TestCase):
         self.assertFalse(oldformat)
         self.assertEqual(1 | 2 | 4 | 64, features)
 
+        #
+        # test that FAST_DIFF is enabled if supported by RBD
+        #   this also enables OBJECT_MAP as required by Ceph
+        #
+        self.service.rbd.RBD_FEATURE_OBJECT_MAP = 8
+        self.service.rbd.RBD_FEATURE_FAST_DIFF = 16
+
+        oldformat, features = self.service._get_rbd_support()
+        self.assertFalse(oldformat)
+        self.assertEqual(1 | 2 | 4 | 8 | 16 | 64, features)
+
     @common_mocks
     def test_get_backup_snap_name(self):
         snap_name = 'backup.%s.snap.3824923.1412' % (fake.VOLUME3_ID)

releasenotes/notes/bug-1907964-9277e5ddec2abeda.yaml

@@ -0,0 +1,11 @@
+---
+fixes:
+  - |
+    RBD driver `bug #1907964
+    <https://bugs.launchpad.net/cinder/+bug/1907964>`_: Add support
+    for fast-diff on backup images stored in Ceph.
+    Provided fast-diff is supported by the backend it will automatically be
+    enabled and used.
+    With fast-diff enabled, the generation of diffs between images and
+    snapshots as well as determining the actual data usage of a snapshot
+    is speed up significantly.