1/* SPDX-License-Identifier: GPL-2.0-or-later */
2/*
3 Red Black Trees
4 (C) 1999 Andrea Arcangeli <andrea@suse.de>
5
6
7 linux/include/linux/rbtree.h
8
9 To use rbtrees you'll have to implement your own insert and search cores.
10 This will avoid us to use callbacks and to drop drammatically performances.
11 I know it's not the cleaner way, but in C (not in C++) to get
12 performances and genericity...
13
14 See Documentation/core-api/rbtree.rst for documentation and samples.
15*/
16
17#ifndef _LINUX_RBTREE_H
18#define _LINUX_RBTREE_H
19
20#include <linux/container_of.h>
21#include <linux/rbtree_types.h>
22
23#include <linux/stddef.h>
24#include <linux/rcupdate.h>
25
26#define rb_parent(r) ((struct rb_node *)((r)->__rb_parent_color & ~3))
27
28#define rb_entry(ptr, type, member) container_of(ptr, type, member)
29
30#define RB_EMPTY_ROOT(root) (READ_ONCE((root)->rb_node) == NULL)
31
32/* 'empty' nodes are nodes that are known not to be inserted in an rbtree */
33#define RB_EMPTY_NODE(node) \
34 ((node)->__rb_parent_color == (unsigned long)(node))
35#define RB_CLEAR_NODE(node) \
36 ((node)->__rb_parent_color = (unsigned long)(node))
37
38
39extern void rb_insert_color(struct rb_node *, struct rb_root *);
40extern void rb_erase(struct rb_node *, struct rb_root *);
41
42
43/* Find logical next and previous nodes in a tree */
44extern struct rb_node *rb_next(const struct rb_node *);
45extern struct rb_node *rb_prev(const struct rb_node *);
46extern struct rb_node *rb_first(const struct rb_root *);
47extern struct rb_node *rb_last(const struct rb_root *);
48
49/* Postorder iteration - always visit the parent after its children */
50extern struct rb_node *rb_first_postorder(const struct rb_root *);
51extern struct rb_node *rb_next_postorder(const struct rb_node *);
52
53/* Fast replacement of a single node without remove/rebalance/add/rebalance */
54extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
55 struct rb_root *root);
56extern void rb_replace_node_rcu(struct rb_node *victim, struct rb_node *new,
57 struct rb_root *root);
58
59static inline void rb_link_node(struct rb_node *node, struct rb_node *parent,
60 struct rb_node **rb_link)
61{
62 node->__rb_parent_color = (unsigned long)parent;
63 node->rb_left = node->rb_right = NULL;
64
65 *rb_link = node;
66}
67
68static inline void rb_link_node_rcu(struct rb_node *node, struct rb_node *parent,
69 struct rb_node **rb_link)
70{
71 node->__rb_parent_color = (unsigned long)parent;
72 node->rb_left = node->rb_right = NULL;
73
74 rcu_assign_pointer(*rb_link, node);
75}
76
77#define rb_entry_safe(ptr, type, member) \
78 ({ typeof(ptr) ____ptr = (ptr); \
79 ____ptr ? rb_entry(____ptr, type, member) : NULL; \
80 })
81
82/**
83 * rbtree_postorder_for_each_entry_safe - iterate in post-order over rb_root of
84 * given type allowing the backing memory of @pos to be invalidated
85 *
86 * @pos: the 'type *' to use as a loop cursor.
87 * @n: another 'type *' to use as temporary storage
88 * @root: 'rb_root *' of the rbtree.
89 * @field: the name of the rb_node field within 'type'.
90 *
91 * rbtree_postorder_for_each_entry_safe() provides a similar guarantee as
92 * list_for_each_entry_safe() and allows the iteration to continue independent
93 * of changes to @pos by the body of the loop.
94 *
95 * Note, however, that it cannot handle other modifications that re-order the
96 * rbtree it is iterating over. This includes calling rb_erase() on @pos, as
97 * rb_erase() may rebalance the tree, causing us to miss some nodes.
98 */
99#define rbtree_postorder_for_each_entry_safe(pos, n, root, field) \
100 for (pos = rb_entry_safe(rb_first_postorder(root), typeof(*pos), field); \
101 pos && ({ n = rb_entry_safe(rb_next_postorder(&pos->field), \
102 typeof(*pos), field); 1; }); \
103 pos = n)
104
105/* Same as rb_first(), but O(1) */
106#define rb_first_cached(root) (root)->rb_leftmost
107
108static inline void rb_insert_color_cached(struct rb_node *node,
109 struct rb_root_cached *root,
110 bool leftmost)
111{
112 if (leftmost)
113 root->rb_leftmost = node;
114 rb_insert_color(node, &root->rb_root);
115}
116
117
118static inline struct rb_node *
119rb_erase_cached(struct rb_node *node, struct rb_root_cached *root)
120{
121 struct rb_node *leftmost = NULL;
122
123 if (root->rb_leftmost == node)
124 leftmost = root->rb_leftmost = rb_next(node);
125
126 rb_erase(node, &root->rb_root);
127
128 return leftmost;
129}
130
131static inline void rb_replace_node_cached(struct rb_node *victim,
132 struct rb_node *new,
133 struct rb_root_cached *root)
134{
135 if (root->rb_leftmost == victim)
136 root->rb_leftmost = new;
137 rb_replace_node(victim, new, root: &root->rb_root);
138}
139
140/*
141 * The below helper functions use 2 operators with 3 different
142 * calling conventions. The operators are related like:
143 *
144 * comp(a->key,b) < 0 := less(a,b)
145 * comp(a->key,b) > 0 := less(b,a)
146 * comp(a->key,b) == 0 := !less(a,b) && !less(b,a)
147 *
148 * If these operators define a partial order on the elements we make no
149 * guarantee on which of the elements matching the key is found. See
150 * rb_find().
151 *
152 * The reason for this is to allow the find() interface without requiring an
153 * on-stack dummy object, which might not be feasible due to object size.
154 */
155
156/**
157 * rb_add_cached() - insert @node into the leftmost cached tree @tree
158 * @node: node to insert
159 * @tree: leftmost cached tree to insert @node into
160 * @less: operator defining the (partial) node order
161 *
162 * Returns @node when it is the new leftmost, or NULL.
163 */
164static __always_inline struct rb_node *
165rb_add_cached(struct rb_node *node, struct rb_root_cached *tree,
166 bool (*less)(struct rb_node *, const struct rb_node *))
167{
168 struct rb_node **link = &tree->rb_root.rb_node;
169 struct rb_node *parent = NULL;
170 bool leftmost = true;
171
172 while (*link) {
173 parent = *link;
174 if (less(node, parent)) {
175 link = &parent->rb_left;
176 } else {
177 link = &parent->rb_right;
178 leftmost = false;
179 }
180 }
181
182 rb_link_node(node, parent, rb_link: link);
183 rb_insert_color_cached(node, root: tree, leftmost);
184
185 return leftmost ? node : NULL;
186}
187
188/**
189 * rb_add() - insert @node into @tree
190 * @node: node to insert
191 * @tree: tree to insert @node into
192 * @less: operator defining the (partial) node order
193 */
194static __always_inline void
195rb_add(struct rb_node *node, struct rb_root *tree,
196 bool (*less)(struct rb_node *, const struct rb_node *))
197{
198 struct rb_node **link = &tree->rb_node;
199 struct rb_node *parent = NULL;
200
201 while (*link) {
202 parent = *link;
203 if (less(node, parent))
204 link = &parent->rb_left;
205 else
206 link = &parent->rb_right;
207 }
208
209 rb_link_node(node, parent, rb_link: link);
210 rb_insert_color(node, tree);
211}
212
213/**
214 * rb_find_add_cached() - find equivalent @node in @tree, or add @node
215 * @node: node to look-for / insert
216 * @tree: tree to search / modify
217 * @cmp: operator defining the node order
218 *
219 * Returns the rb_node matching @node, or NULL when no match is found and @node
220 * is inserted.
221 */
222static __always_inline struct rb_node *
223rb_find_add_cached(struct rb_node *node, struct rb_root_cached *tree,
224 int (*cmp)(const struct rb_node *new, const struct rb_node *exist))
225{
226 bool leftmost = true;
227 struct rb_node **link = &tree->rb_root.rb_node;
228 struct rb_node *parent = NULL;
229 int c;
230
231 while (*link) {
232 parent = *link;
233 c = cmp(node, parent);
234
235 if (c < 0) {
236 link = &parent->rb_left;
237 } else if (c > 0) {
238 link = &parent->rb_right;
239 leftmost = false;
240 } else {
241 return parent;
242 }
243 }
244
245 rb_link_node(node, parent, rb_link: link);
246 rb_insert_color_cached(node, root: tree, leftmost);
247 return NULL;
248}
249
250/**
251 * rb_find_add() - find equivalent @node in @tree, or add @node
252 * @node: node to look-for / insert
253 * @tree: tree to search / modify
254 * @cmp: operator defining the node order
255 *
256 * Returns the rb_node matching @node, or NULL when no match is found and @node
257 * is inserted.
258 */
259static __always_inline struct rb_node *
260rb_find_add(struct rb_node *node, struct rb_root *tree,
261 int (*cmp)(struct rb_node *, const struct rb_node *))
262{
263 struct rb_node **link = &tree->rb_node;
264 struct rb_node *parent = NULL;
265 int c;
266
267 while (*link) {
268 parent = *link;
269 c = cmp(node, parent);
270
271 if (c < 0)
272 link = &parent->rb_left;
273 else if (c > 0)
274 link = &parent->rb_right;
275 else
276 return parent;
277 }
278
279 rb_link_node(node, parent, rb_link: link);
280 rb_insert_color(node, tree);
281 return NULL;
282}
283
284/**
285 * rb_find_add_rcu() - find equivalent @node in @tree, or add @node
286 * @node: node to look-for / insert
287 * @tree: tree to search / modify
288 * @cmp: operator defining the node order
289 *
290 * Adds a Store-Release for link_node.
291 *
292 * Returns the rb_node matching @node, or NULL when no match is found and @node
293 * is inserted.
294 */
295static __always_inline struct rb_node *
296rb_find_add_rcu(struct rb_node *node, struct rb_root *tree,
297 int (*cmp)(struct rb_node *, const struct rb_node *))
298{
299 struct rb_node **link = &tree->rb_node;
300 struct rb_node *parent = NULL;
301 int c;
302
303 while (*link) {
304 parent = *link;
305 c = cmp(node, parent);
306
307 if (c < 0)
308 link = &parent->rb_left;
309 else if (c > 0)
310 link = &parent->rb_right;
311 else
312 return parent;
313 }
314
315 rb_link_node_rcu(node, parent, rb_link: link);
316 rb_insert_color(node, tree);
317 return NULL;
318}
319
320/**
321 * rb_find() - find @key in tree @tree
322 * @key: key to match
323 * @tree: tree to search
324 * @cmp: operator defining the node order
325 *
326 * Returns the rb_node matching @key or NULL.
327 */
328static __always_inline struct rb_node *
329rb_find(const void *key, const struct rb_root *tree,
330 int (*cmp)(const void *key, const struct rb_node *))
331{
332 struct rb_node *node = tree->rb_node;
333
334 while (node) {
335 int c = cmp(key, node);
336
337 if (c < 0)
338 node = node->rb_left;
339 else if (c > 0)
340 node = node->rb_right;
341 else
342 return node;
343 }
344
345 return NULL;
346}
347
348/**
349 * rb_find_rcu() - find @key in tree @tree
350 * @key: key to match
351 * @tree: tree to search
352 * @cmp: operator defining the node order
353 *
354 * Notably, tree descent vs concurrent tree rotations is unsound and can result
355 * in false-negatives.
356 *
357 * Returns the rb_node matching @key or NULL.
358 */
359static __always_inline struct rb_node *
360rb_find_rcu(const void *key, const struct rb_root *tree,
361 int (*cmp)(const void *key, const struct rb_node *))
362{
363 struct rb_node *node = tree->rb_node;
364
365 while (node) {
366 int c = cmp(key, node);
367
368 if (c < 0)
369 node = rcu_dereference_raw(node->rb_left);
370 else if (c > 0)
371 node = rcu_dereference_raw(node->rb_right);
372 else
373 return node;
374 }
375
376 return NULL;
377}
378
379/**
380 * rb_find_first() - find the first @key in @tree
381 * @key: key to match
382 * @tree: tree to search
383 * @cmp: operator defining node order
384 *
385 * Returns the leftmost node matching @key, or NULL.
386 */
387static __always_inline struct rb_node *
388rb_find_first(const void *key, const struct rb_root *tree,
389 int (*cmp)(const void *key, const struct rb_node *))
390{
391 struct rb_node *node = tree->rb_node;
392 struct rb_node *match = NULL;
393
394 while (node) {
395 int c = cmp(key, node);
396
397 if (c <= 0) {
398 if (!c)
399 match = node;
400 node = node->rb_left;
401 } else if (c > 0) {
402 node = node->rb_right;
403 }
404 }
405
406 return match;
407}
408
409/**
410 * rb_next_match() - find the next @key in @tree
411 * @key: key to match
412 * @tree: tree to search
413 * @cmp: operator defining node order
414 *
415 * Returns the next node matching @key, or NULL.
416 */
417static __always_inline struct rb_node *
418rb_next_match(const void *key, struct rb_node *node,
419 int (*cmp)(const void *key, const struct rb_node *))
420{
421 node = rb_next(node);
422 if (node && cmp(key, node))
423 node = NULL;
424 return node;
425}
426
427/**
428 * rb_for_each() - iterates a subtree matching @key
429 * @node: iterator
430 * @key: key to match
431 * @tree: tree to search
432 * @cmp: operator defining node order
433 */
434#define rb_for_each(node, key, tree, cmp) \
435 for ((node) = rb_find_first((key), (tree), (cmp)); \
436 (node); (node) = rb_next_match((key), (node), (cmp)))
437
438#endif /* _LINUX_RBTREE_H */
439