maple_tree: make mas_validate_limits() check root node and node limit

Update mas_validate_limits() to check root node, check node limit pivot if
there is enough room for it to exist and check data_end.  Remove the check
for child existence as it is done in mas_validate_child_slot().

Link: https://lkml.kernel.org/r/20230711035444.526-6-zhangpeng.00@bytedance.com
Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

lib/maple_tree.c

@@ -7120,7 +7120,9 @@ static void mas_validate_child_slot(struct ma_state *mas)
 }
 
 /*
- * Validate all pivots are within mas->min and mas->max.
+ * Validate all pivots are within mas->min and mas->max, check metadata ends
+ * where the maximum ends and ensure there is no slots or pivots set outside of
+ * the end of the data.
  */
 static void mas_validate_limits(struct ma_state *mas)
 {
@@ -7130,26 +7132,15 @@ static void mas_validate_limits(struct ma_state *mas)
 	void __rcu **slots = ma_slots(mte_to_node(mas->node), type);
 	unsigned long *pivots = ma_pivots(mas_mn(mas), type);
 
-	/* all limits are fine here. */
-	if (mte_is_root(mas->node))
-		return;
-
 	for (i = 0; i < mt_slots[type]; i++) {
 		unsigned long piv;
 
 		piv = mas_safe_pivot(mas, pivots, i, type);
 
-		if (!piv && (i != 0))
-			break;
-
-		if (!mte_is_leaf(mas->node)) {
-			void *entry = mas_slot(mas, slots, i);
-
-			if (!entry)
-				pr_err("%p[%u] cannot be null\n",
-				       mas_mn(mas), i);
-
-			MT_BUG_ON(mas->tree, !entry);
+		if (!piv && (i != 0)) {
+			pr_err("Missing node limit pivot at %p[%u]",
+			       mas_mn(mas), i);
+			MAS_WARN_ON(mas, 1);
 		}
 
 		if (prev_piv > piv) {
@@ -7172,6 +7163,13 @@ static void mas_validate_limits(struct ma_state *mas)
 		if (piv == mas->max)
 			break;
 	}
+
+	if (mas_data_end(mas) != i) {
+		pr_err("node%p: data_end %u != the last slot offset %u\n",
+		       mas_mn(mas), mas_data_end(mas), i);
+		MT_BUG_ON(mas->tree, 1);
+	}
+
 	for (i += 1; i < mt_slots[type]; i++) {
 		void *entry = mas_slot(mas, slots, i);