[RBD] Clone v2: Image is unusable if deletion fails

Recently cinder has utilized Ceph clone v2 support for its
RBD backend, since then if you attempt to delete an image from
glance that has a dependent volume, all future uses of that
image will fail in error state. Despite the fact that image
itself is still inside of Ceph/Glance. This issue is reproducible
if you are using ceph client version greater than 'luminous'

To resolve this issue glance RBD driver now checks whether snapshot
of original image has any external references before deleting/removing
it's snapshot and returns 409 Conflict response if it has any.

NOTE: To check this dependency glance osd needs 'read' access to
cinder and nova side RBD pool.

Closes-Bug: #1954883
Depends-on: https://review.opendev.org/c/openstack/devstack-plugin-ceph/+/819476
Change-Id: If30b7bd7acac148b6f89ce46abbe128c678c90e7

2 files changed, 30 insertions, 0 deletions

diff --git a/glance_store/tests/unit/test_multistore_rbd.py b/glance_store/tests/unit/test_multistore_rbd.py
index 384fca0..822c1b5 100644
--- a/glance_store/tests/unit/test_multistore_rbd.py
+++ b/glance_store/tests/unit/test_multistore_rbd.py
@@ -113,6 +113,12 @@ class MockRBD(object):
         def remove_snap(self, *args, **kwargs):
             pass
 
+        def set_snap(self, *args, **kwargs):
+            pass
+
+        def list_children(self, *args, **kwargs):
+            pass
+
         def protect_snap(self, *args, **kwargs):
             pass
 
@@ -417,6 +423,15 @@ class TestMultiStore(base.MultiStoreBaseTest,
 
             self.called_commands_expected = ['unprotect_snap']
 
+    def test_delete_image_snap_has_external_references(self):
+        with mock.patch.object(MockRBD.Image, 'list_children') as mocked:
+            mocked.return_value = True
+
+            self.assertRaises(exceptions.InUseByStore,
+                              self.store._delete_image,
+                              'fake_pool', self.location.image,
+                              snapshot_name='snap')
+
     def test_delete_image_w_snap_exc_image_has_snap(self):
         def _fake_remove(*args, **kwargs):
             self.called_commands_actual.append('remove')
diff --git a/glance_store/tests/unit/test_rbd_store.py b/glance_store/tests/unit/test_rbd_store.py
index 2d1cae6..cbd34ac 100644
--- a/glance_store/tests/unit/test_rbd_store.py
+++ b/glance_store/tests/unit/test_rbd_store.py
@@ -114,6 +114,12 @@ class MockRBD(object):
         def remove_snap(self, *args, **kwargs):
             pass
 
+        def set_snap(self, *args, **kwargs):
+            pass
+
+        def list_children(self, *args, **kwargs):
+            pass
+
         def protect_snap(self, *args, **kwargs):
             pass
 
@@ -623,6 +629,15 @@ class TestStore(base.StoreBaseTest,
 
             self.called_commands_expected = ['unprotect_snap']
 
+    def test_delete_image_snap_has_external_references(self):
+        with mock.patch.object(MockRBD.Image, 'list_children') as mocked:
+            mocked.return_value = True
+
+            self.assertRaises(exceptions.InUseByStore,
+                              self.store._delete_image,
+                              'fake_pool', self.location.image,
+                              snapshot_name='snap')
+
     def test_delete_image_w_snap_exc_image_has_snap(self):
         def _fake_remove(*args, **kwargs):
             self.called_commands_actual.append('remove')