of: overlay: expand check of whether overlay changeset can be removed

The test of whether it is safe to remove an overlay changeset
looked at whether any node in the overlay changeset was in a
subtree rooted at any more recently applied overlay changeset
node.

The test failed to determine whether any node in the overlay
changeset was the root of a subtree that contained a more
recently applied overlay changeset node.  Add this additional
check to the test.

The test is still lacking any check for any phandle dependencies.
Signed-off-by: Frank Rowand <frank.rowand@sony.com>
Signed-off-by: Rob Herring <robh@kernel.org>

drivers/of/overlay.c

@@ -707,13 +707,13 @@ static int find_node(struct device_node *tree, struct device_node *np)
 }
 
 /*
- * Is @remove_ce_np a child of or the same as any
+ * Is @remove_ce_node a child of, a parent of, or the same as any
  * node in an overlay changeset more topmost than @remove_ovcs?
  *
  * Returns 1 if found, else 0
  */
-static int node_in_later_cs(struct overlay_changeset *remove_ovcs,
-		struct device_node *remove_ce_np)
+static int node_overlaps_later_cs(struct overlay_changeset *remove_ovcs,
+		struct device_node *remove_ce_node)
 {
 	struct overlay_changeset *ovcs;
 	struct of_changeset_entry *ce;
@@ -723,10 +723,16 @@ static int node_in_later_cs(struct overlay_changeset *remove_ovcs,
 			break;
 
 		list_for_each_entry(ce, &ovcs->cset.entries, node) {
-			if (find_node(ce->np, remove_ce_np)) {
-				pr_err("%s: #%d clashes #%d @%pOF\n",
+			if (find_node(ce->np, remove_ce_node)) {
+				pr_err("%s: #%d overlaps with #%d @%pOF\n",
 					__func__, remove_ovcs->id, ovcs->id,
-					remove_ce_np);
+					remove_ce_node);
+				return 1;
+			}
+			if (find_node(remove_ce_node, ce->np)) {
+				pr_err("%s: #%d overlaps with #%d @%pOF\n",
+					__func__, remove_ovcs->id, ovcs->id,
+					remove_ce_node);
 				return 1;
 			}
 		}
@@ -750,7 +756,7 @@ static int overlay_removal_is_ok(struct overlay_changeset *remove_ovcs)
 	struct of_changeset_entry *remove_ce;
 
 	list_for_each_entry(remove_ce, &remove_ovcs->cset.entries, node) {
-		if (node_in_later_cs(remove_ovcs, remove_ce->np)) {
+		if (node_overlaps_later_cs(remove_ovcs, remove_ce->np)) {
 			pr_err("overlay #%d is not topmost\n", remove_ovcs->id);
 			return 0;
 		}