maple_tree: simplify mas_commit_b_node()

The only callers of mas_commit_b_node() are those with store type of
wr_rebalance and wr_split_store. Use mas->store_type to dispatch to the
correct helper function. This allows the removal of mas_reuse_node() as
it is no longer used.

Link: https://lkml.kernel.org/r/20240814161944.55347-12-sidhartha.kumar@oracle.comSigned-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

lib/maple_tree.c

@@ -3395,72 +3395,22 @@ static int mas_split(struct ma_state *mas, struct maple_big_node *b_node)
 	return 1;
 }
 
-/*
- * mas_reuse_node() - Reuse the node to store the data.
- * @wr_mas: The maple write state
- * @bn: The maple big node
- * @end: The end of the data.
- *
- * Will always return false in RCU mode.
- *
- * Return: True if node was reused, false otherwise.
- */
-static inline bool mas_reuse_node(struct ma_wr_state *wr_mas,
-			  struct maple_big_node *bn, unsigned char end)
-{
-	/* Need to be rcu safe. */
-	if (mt_in_rcu(wr_mas->mas->tree))
-		return false;
-
-	if (end > bn->b_end) {
-		int clear = mt_slots[wr_mas->type] - bn->b_end;
-
-		memset(wr_mas->slots + bn->b_end, 0, sizeof(void *) * clear--);
-		memset(wr_mas->pivots + bn->b_end, 0, sizeof(void *) * clear);
-	}
-	mab_mas_cp(bn, 0, bn->b_end, wr_mas->mas, false);
-	return true;
-}
-
 /*
  * mas_commit_b_node() - Commit the big node into the tree.
  * @wr_mas: The maple write state
  * @b_node: The maple big node
- * @end: The end of the data.
  */
 static noinline_for_kasan int mas_commit_b_node(struct ma_wr_state *wr_mas,
-			    struct maple_big_node *b_node, unsigned char end)
+			    struct maple_big_node *b_node)
 {
-	struct maple_node *node;
-	struct maple_enode *old_enode;
-	unsigned char b_end = b_node->b_end;
-	enum maple_type b_type = b_node->type;
-
-	old_enode = wr_mas->mas->node;
-	if ((b_end < mt_min_slots[b_type]) &&
-	    (!mte_is_root(old_enode)) &&
-	    (mas_mt_height(wr_mas->mas) > 1))
-		return mas_rebalance(wr_mas->mas, b_node);
-
-	if (b_end >= mt_slots[b_type])
-		return mas_split(wr_mas->mas, b_node);
+	enum store_type type = wr_mas->mas->store_type;
 
-	if (mas_reuse_node(wr_mas, b_node, end))
-		goto reuse_node;
+	WARN_ON_ONCE(type != wr_rebalance && type != wr_split_store);
 
-	mas_node_count(wr_mas->mas, 1);
-	if (mas_is_err(wr_mas->mas))
-		return 0;
+	if (type == wr_rebalance)
+		return mas_rebalance(wr_mas->mas, b_node);
 
-	node = mas_pop_node(wr_mas->mas);
-	node->parent = mas_mn(wr_mas->mas)->parent;
-	wr_mas->mas->node = mt_mk_node(node, b_type);
-	mab_mas_cp(b_node, 0, b_end, wr_mas->mas, false);
-	mas_replace_node(wr_mas->mas, old_enode);
-reuse_node:
-	mas_update_gap(wr_mas->mas);
-	wr_mas->mas->end = b_end;
-	return 1;
+	return mas_split(wr_mas->mas, b_node);
 }
 
 /*
@@ -4155,7 +4105,7 @@ static void mas_wr_bnode(struct ma_wr_state *wr_mas)
 	trace_ma_write(__func__, wr_mas->mas, 0, wr_mas->entry);
 	memset(&b_node, 0, sizeof(struct maple_big_node));
 	mas_store_b_node(wr_mas, &b_node, wr_mas->offset_end);
-	mas_commit_b_node(wr_mas, &b_node, wr_mas->mas->end);
+	mas_commit_b_node(wr_mas, &b_node);
 }
 
 static inline void mas_wr_modify(struct ma_wr_state *wr_mas)