maple_tree: refine ma_state init from mas_start()

If mas->node is an MAS_START, there are three cases, and they all assign
different values to mas->node and mas->offset.  So there is no need to set
them to a default value before updating.

Update them directly to make them easier to understand and for better
readability.

Link: https://lkml.kernel.org/r/20221221060058.609003-7-vernon2gm@gmail.comSigned-off-by: Vernon Yang <vernon2gm@gmail.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

lib/maple_tree.c

@@ -1329,7 +1329,7 @@ static void mas_node_count(struct ma_state *mas, int count)
  * mas_start() - Sets up maple state for operations.
  * @mas: The maple state.
  *
- * If mas->node == MAS_START, then set the min, max, depth, and offset to
+ * If mas->node == MAS_START, then set the min, max and depth to
  * defaults.
  *
  * Return:
@@ -1343,22 +1343,22 @@ static inline struct maple_enode *mas_start(struct ma_state *mas)
 	if (likely(mas_is_start(mas))) {
 		struct maple_enode *root;
 
-		mas->node = MAS_NONE;
 		mas->min = 0;
 		mas->max = ULONG_MAX;
 		mas->depth = 0;
-		mas->offset = 0;
 
 		root = mas_root(mas);
 		/* Tree with nodes */
 		if (likely(xa_is_node(root))) {
 			mas->depth = 1;
 			mas->node = mte_safe_root(root);
+			mas->offset = 0;
 			return NULL;
 		}
 
 		/* empty tree */
 		if (unlikely(!root)) {
+			mas->node = MAS_NONE;
 			mas->offset = MAPLE_NODE_SLOTS;
 			return NULL;
 		}