[JFFS2] Use rb_first() and rb_last() cleanup

Use rb_first() and rb_last() to implement frag_first() and frag_last().

Signed-off-by: Akinbou Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
diff --git a/fs/jffs2/nodelist.h b/fs/jffs2/nodelist.h
index 0ddfd70..4178b4b5 100644
--- a/fs/jffs2/nodelist.h
+++ b/fs/jffs2/nodelist.h
@@ -294,23 +294,21 @@
 
 static inline struct jffs2_node_frag *frag_first(struct rb_root *root)
 {
-	struct rb_node *node = root->rb_node;
+	struct rb_node *node = rb_first(root);
 
 	if (!node)
 		return NULL;
-	while(node->rb_left)
-		node = node->rb_left;
+
 	return rb_entry(node, struct jffs2_node_frag, rb);
 }
 
 static inline struct jffs2_node_frag *frag_last(struct rb_root *root)
 {
-	struct rb_node *node = root->rb_node;
+	struct rb_node *node = rb_last(root);
 
 	if (!node)
 		return NULL;
-	while(node->rb_right)
-		node = node->rb_right;
+
 	return rb_entry(node, struct jffs2_node_frag, rb);
 }