1 files changed, 40 insertions, 0 deletions

diff --git a/lib/rbtree.c b/lib/rbtree.c
index c0e31fe2fabf..65f4effd117f 100644
--- a/lib/rbtree.c
+++ b/lib/rbtree.c
@@ -518,3 +518,43 @@ void rb_replace_node(struct rb_node *victim, struct rb_node *new,
         *new = *victim;
 }
 EXPORT_SYMBOL(rb_replace_node);
+
+static struct rb_node *rb_left_deepest_node(const struct rb_node *node)
+{
+        for (;;) {
+                if (node->rb_left)
+                        node = node->rb_left;
+                else if (node->rb_right)
+                        node = node->rb_right;
+                else
+                        return (struct rb_node *)node;
+        }
+}
+
+struct rb_node *rb_next_postorder(const struct rb_node *node)
+{
+        const struct rb_node *parent;
+        if (!node)
+                return NULL;
+        parent = rb_parent(node);
+
+        /* If we're sitting on node, we've already seen our children */
+        if (parent && node == parent->rb_left && parent->rb_right) {
+                /* If we are the parent's left node, go to the parent's right
+                 * node then all the way down to the left */
+                return rb_left_deepest_node(parent->rb_right);
+        } else
+                /* Otherwise we are the parent's right node, and the parent
+                 * should be next */
+                return (struct rb_node *)parent;
+}
+EXPORT_SYMBOL(rb_next_postorder);
+
+struct rb_node *rb_first_postorder(const struct rb_root *root)
+{
+        if (!root->rb_node)
+                return NULL;
+
+        return rb_left_deepest_node(root->rb_node);
+}
+EXPORT_SYMBOL(rb_first_postorder);