mgr/smb: prevent switching between clustering modes

Prevent users from changing the cluster resource values such that a
cluster is changed from not using CTDB to using CTDB and vice versa.
This avoids complex situations that arise when making these sorts of
changes, in particular going from CTDB to non-CTDB which I am very sure
will mess up the tdb files.

Blocking these changes limits the need to test changing clustering
behavior on the fly. We can always revisit this in the future if needed.

Fixes: https://tracker.ceph.com/issues/68511

Signed-off-by: John Mulligan <[email protected]>

Author: phlogistonjohn

src/pybind/mgr/smb/handler.py

@@ -29,6 +29,7 @@
     JoinSourceType,
     LoginAccess,
     LoginCategory,
+    SMBClustering,
     State,
     UserGroupSourceType,
 )
@@ -869,6 +870,25 @@ def _check_cluster_modifications(
                 'domain/realm value may not be changed',
                 status={'existing_domain_realm': prev.domain_settings.realm},
             )
+    if cluster.is_clustered() != prev.is_clustered():
+        prev_clustering = prev.is_clustered()
+        cterms = {True: 'enabled', False: 'disabled'}
+        msg = (
+            f'a cluster resource with clustering {cterms[prev_clustering]}'
+            f' may not be changed to clustering {cterms[not prev_clustering]}'
+        )
+        opt_terms = {
+            True: SMBClustering.ALWAYS.value,
+            False: SMBClustering.NEVER.value,
+        }
+        hint = {
+            'note': (
+                'Set "clustering" to an explicit value that matches the'
+                ' current clustering behavior'
+            ),
+            'value': opt_terms[prev_clustering],
+        }
+        raise ErrorResult(cluster, msg, status={'hint': hint})
 
 
 def _parse_earmark(earmark: str) -> dict: