rbtree: add comment to rb_insert_augmented()

The comment is copied from Documentation/rbtree.txt, but this comment is
so important that it should also be in the code.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: Michel Lespinasse <walken@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/rbtree_augmented.h b/include/linux/rbtree_augmented.h
index fea49b5da12a99bfa6c87b865a461a2a28e0495b..378c5ee75f78f5e1a521d87afeaf13fe21999af5 100644 (file)
--- a/include/linux/rbtree_augmented.h
+++ b/include/linux/rbtree_augmented.h
@@ -43,6 +43,16 @@ struct rb_augment_callbacks {
 
 extern void __rb_insert_augmented(struct rb_node *node, struct rb_root *root,
        void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
+/*
+ * Fixup the rbtree and update the augmented information when rebalancing.
+ *
+ * On insertion, the user must update the augmented information on the path
+ * leading to the inserted node, then call rb_link_node() as usual and
+ * rb_augment_inserted() instead of the usual rb_insert_color() call.
+ * If rb_augment_inserted() rebalances the rbtree, it will callback into
+ * a user provided function to update the augmented information on the
+ * affected subtrees.
+ */
 static inline void
 rb_insert_augmented(struct rb_node *node, struct rb_root *root,
                    const struct rb_augment_callbacks *augment)