prio_tree: simplify prio_tree_expand()

In current code, the deleted-node is recorded from first to last,
actually, we can directly attach these node on 'node' we will insert as
the left child, it can let the code more readable.

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/prio_tree.c

@@ -94,43 +94,33 @@ static inline unsigned long prio_tree_maxindex(unsigned int bits)
 static struct prio_tree_node *prio_tree_expand(struct prio_tree_root *root,
 		struct prio_tree_node *node, unsigned long max_heap_index)
 {
-	struct prio_tree_node *first = NULL, *prev, *last = NULL;
+	struct prio_tree_node *prev;
 
 	if (max_heap_index > prio_tree_maxindex(root->index_bits))
 		root->index_bits++;
 
+	prev = node;
+	INIT_PRIO_TREE_NODE(node);
+
 	while (max_heap_index > prio_tree_maxindex(root->index_bits)) {
+		struct prio_tree_node *tmp = root->prio_tree_node;
+
 		root->index_bits++;
 
 		if (prio_tree_empty(root))
 			continue;
 
-		if (first == NULL) {
-			first = root->prio_tree_node;
-			prio_tree_remove(root, root->prio_tree_node);
-			INIT_PRIO_TREE_NODE(first);
-			last = first;
-		} else {
-			prev = last;
-			last = root->prio_tree_node;
-			prio_tree_remove(root, root->prio_tree_node);
-			INIT_PRIO_TREE_NODE(last);
-			prev->left = last;
-			last->parent = prev;
-		}
+		prio_tree_remove(root, root->prio_tree_node);
+		INIT_PRIO_TREE_NODE(tmp);
+
+		prev->left = tmp;
+		tmp->parent = prev;
+		prev = tmp;
 	}
 
-	INIT_PRIO_TREE_NODE(node);
-
-	if (first) {
-		node->left = first;
-		first->parent = node;
-	} else
-		last = node;
-
 	if (!prio_tree_empty(root)) {
-		last->left = root->prio_tree_node;
-		last->left->parent = last;
+		prev->left = root->prio_tree_node;
+		prev->left->parent = prev;
 	}
 
 	root->prio_tree_node = node;