tools: Update rbtree implementation

[linux.git] / tools / include / linux / rbtree.h

diff --git a/tools/include/linux/rbtree.h b/tools/include/linux/rbtree.h
index 112582253dd0319004e691953c27a475509a005e..8e9ed4786269260acb443182287fb41368815894 100644 (file)
--- a/tools/include/linux/rbtree.h
+++ b/tools/include/linux/rbtree.h
@@ -43,13 +43,28 @@ struct rb_root {
        struct rb_node *rb_node;
 };
 
+/*
+ * Leftmost-cached rbtrees.
+ *
+ * We do not cache the rightmost node based on footprint
+ * size vs number of potential users that could benefit
+ * from O(1) rb_last(). Just not worth it, users that want
+ * this feature can always implement the logic explicitly.
+ * Furthermore, users that want to cache both pointers may
+ * find it a bit asymmetric, but that's ok.
+ */
+struct rb_root_cached {
+       struct rb_root rb_root;
+       struct rb_node *rb_leftmost;
+};
 
 #define rb_parent(r)   ((struct rb_node *)((r)->__rb_parent_color & ~3))
 
 #define RB_ROOT        (struct rb_root) { NULL, }
+#define RB_ROOT_CACHED (struct rb_root_cached) { {NULL, }, NULL }
 #define        rb_entry(ptr, type, member) container_of(ptr, type, member)
 
-#define RB_EMPTY_ROOT(root)  ((root)->rb_node == NULL)
+#define RB_EMPTY_ROOT(root)  (READ_ONCE((root)->rb_node) == NULL)
 
 /* 'empty' nodes are nodes that are known not to be inserted in an rbtree */
 #define RB_EMPTY_NODE(node)  \
@@ -68,6 +83,12 @@ extern struct rb_node *rb_prev(const struct rb_node *);
 extern struct rb_node *rb_first(const struct rb_root *);
 extern struct rb_node *rb_last(const struct rb_root *);
 
+extern void rb_insert_color_cached(struct rb_node *,
+                                  struct rb_root_cached *, bool);
+extern void rb_erase_cached(struct rb_node *node, struct rb_root_cached *);
+/* Same as rb_first(), but O(1) */
+#define rb_first_cached(root) (root)->rb_leftmost
+
 /* Postorder iteration - always visit the parent after its children */
 extern struct rb_node *rb_first_postorder(const struct rb_root *);
 extern struct rb_node *rb_next_postorder(const struct rb_node *);
@@ -75,6 +96,8 @@ extern struct rb_node *rb_next_postorder(const struct rb_node *);
 /* Fast replacement of a single node without remove/rebalance/add/rebalance */
 extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
                            struct rb_root *root);
+extern void rb_replace_node_cached(struct rb_node *victim, struct rb_node *new,
+                                  struct rb_root_cached *root);
 
 static inline void rb_link_node(struct rb_node *node, struct rb_node *parent,
                                struct rb_node **rb_link)
@@ -90,12 +113,29 @@ static inline void rb_link_node(struct rb_node *node, struct rb_node *parent,
           ____ptr ? rb_entry(____ptr, type, member) : NULL; \
        })
 
-
-/*
- * Handy for checking that we are not deleting an entry that is
- * already in a list, found in block/{blk-throttle,cfq-iosched}.c,
- * probably should be moved to lib/rbtree.c...
+/**
+ * rbtree_postorder_for_each_entry_safe - iterate in post-order over rb_root of
+ * given type allowing the backing memory of @pos to be invalidated
+ *
+ * @pos:       the 'type *' to use as a loop cursor.
+ * @n:         another 'type *' to use as temporary storage
+ * @root:      'rb_root *' of the rbtree.
+ * @field:     the name of the rb_node field within 'type'.
+ *
+ * rbtree_postorder_for_each_entry_safe() provides a similar guarantee as
+ * list_for_each_entry_safe() and allows the iteration to continue independent
+ * of changes to @pos by the body of the loop.
+ *
+ * Note, however, that it cannot handle other modifications that re-order the
+ * rbtree it is iterating over. This includes calling rb_erase() on @pos, as
+ * rb_erase() may rebalance the tree, causing us to miss some nodes.
  */
+#define rbtree_postorder_for_each_entry_safe(pos, n, root, field) \
+       for (pos = rb_entry_safe(rb_first_postorder(root), typeof(*pos), field); \
+            pos && ({ n = rb_entry_safe(rb_next_postorder(&pos->field), \
+                       typeof(*pos), field); 1; }); \
+            pos = n)
+
 static inline void rb_erase_init(struct rb_node *n, struct rb_root *root)
 {
        rb_erase(n, root);