rbtree: Add rb_add_augmented_cached() helper

While slightly sub-optimal, updating the augmented data while going
down the tree during lookup would be faster -- alas the augment
interface does not currently allow for that, provide a generic helper
to add a node to an augmented cached tree.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230531124603.862983648@infradead.org

diff --git a/include/linux/rbtree_augmented.h b/include/linux/rbtree_augmented.h
index 7ee7ed5..6dbc5a1 100644 (file)
--- a/include/linux/rbtree_augmented.h
+++ b/include/linux/rbtree_augmented.h
@@ -60,6 +60,32 @@ rb_insert_augmented_cached(struct rb_node *node,
        rb_insert_augmented(node, &root->rb_root, augment);
 }
 
+static __always_inline struct rb_node *
+rb_add_augmented_cached(struct rb_node *node, struct rb_root_cached *tree,
+                       bool (*less)(struct rb_node *, const struct rb_node *),
+                       const struct rb_augment_callbacks *augment)
+{
+       struct rb_node **link = &tree->rb_root.rb_node;
+       struct rb_node *parent = NULL;
+       bool leftmost = true;
+
+       while (*link) {
+               parent = *link;
+               if (less(node, parent)) {
+                       link = &parent->rb_left;
+               } else {
+                       link = &parent->rb_right;
+                       leftmost = false;
+               }
+       }
+
+       rb_link_node(node, parent, link);
+       augment->propagate(parent, NULL); /* suboptimal */
+       rb_insert_augmented_cached(node, tree, leftmost, augment);
+
+       return leftmost ? node : NULL;
+}
+
 /*
  * Template for declaring augmented rbtree callbacks (generic case)
  *