-infrastructure. rbtree user who wants this feature will have an augment
-callback function in rb_root initialized.
-
-This callback function will be called from rbtree core routines whenever
-a node has a change in one or both of its children. It is the responsibility
-of the callback function to recalculate the additional data that is in the
-rb node using new children information. Note that if this new additional
-data affects the parent node's additional data, then callback function has
-to handle it and do the recursive updates.
+infrastructure. An rbtree user who wants this feature will have to call the
+augmentation functions with the user provided augmentation callback
+when inserting and erasing nodes.
+
+On insertion, the user must call rb_augment_insert() once the new node is in
+place. This will cause the augmentation function callback to be called for
+each node between the new node and the root which has been affected by the
+insertion.
+
+When erasing a node, the user must call rb_augment_erase_begin() first to
+retrieve the deepest node on the rebalance path. Then, after erasing the
+original node, the user must call rb_augment_erase_end() with the deepest
+node found earlier. This will cause the augmentation function to be called
+for each affected node between the deepest node and the root.