fix: Require all nodes being shut down when mirroring the root inode

Except for the one that holds the root inode, of course.

Author: rustybee42

mgmtd/src/grpc/buddy_group.rs

@@ -267,7 +267,32 @@ pub(crate) async fn mirror_root_inode(
             })?;
 
             if clients > 0 {
-                bail!("This operation requires that all clients are disconnected/unmounted, but still has {clients} clients mounted.");
+                bail!(
+                    "This operation requires that all clients are disconnected/unmounted. \
+{clients} clients are still mounted."
+                );
+            }
+
+            let mut server_stmt = tx.prepare(sql!(
+                "SELECT COUNT(*) FROM nodes
+                WHERE node_type = ?1 AND UNIXEPOCH('now') - UNIXEPOCH(last_contact) < 180
+                AND node_uid != ?2"
+            ))?;
+
+            let metas = server_stmt.query_row([NodeType::Meta.sql_variant(), node_uid], |row| {
+                row.get::<_, i64>(0)
+            })?;
+            let storages = server_stmt
+                .query_row([NodeType::Storage.sql_variant(), node_uid], |row| {
+                    row.get::<_, i64>(0)
+                })?;
+
+            if metas > 0 || storages > 0 {
+                bail!(
+                    "This operation requires that all nodes except the root meta node are shut \
+down. {metas} meta nodes (excluding the root meta node) and {storages} storage nodes have \
+communicated during the last 180s."
+                );
             }
 
             Ok(node_uid)