xref: /linux/include/linux/rbtree.h (revision 0eb4aaa230d725fa9b1cd758c0f17abca5597af6)
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 
39 extern void rb_insert_color(struct rb_node *, struct rb_root *);
40 extern void rb_erase(struct rb_node *, struct rb_root *);
41 
42 
43 /* Find logical next and previous nodes in a tree */
44 extern struct rb_node *rb_next(const struct rb_node *);
45 extern struct rb_node *rb_prev(const struct rb_node *);
46 extern struct rb_node *rb_first(const struct rb_root *);
47 extern struct rb_node *rb_last(const struct rb_root *);
48 
49 /* Postorder iteration - always visit the parent after its children */
50 extern struct rb_node *rb_first_postorder(const struct rb_root *);
51 extern struct rb_node *rb_next_postorder(const struct rb_node *);
52 
53 /* Fast replacement of a single node without remove/rebalance/add/rebalance */
54 extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
55 			    struct rb_root *root);
56 extern void rb_replace_node_rcu(struct rb_node *victim, struct rb_node *new,
57 				struct rb_root *root);
58 
rb_link_node(struct rb_node * node,struct rb_node * parent,struct rb_node ** rb_link)59 static 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 
rb_link_node_rcu(struct rb_node * node,struct rb_node * parent,struct rb_node ** rb_link)68 static 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 
rb_insert_color_cached(struct rb_node * node,struct rb_root_cached * root,bool leftmost)108 static 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 
118 static inline struct rb_node *
rb_erase_cached(struct rb_node * node,struct rb_root_cached * root)119 rb_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 
rb_replace_node_cached(struct rb_node * victim,struct rb_node * new,struct rb_root_cached * root)131 static 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->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  */
164 static __always_inline struct rb_node *
rb_add_cached(struct rb_node * node,struct rb_root_cached * tree,bool (* less)(struct rb_node *,const struct rb_node *))165 rb_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, link);
183 	rb_insert_color_cached(node, 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  */
194 static __always_inline void
rb_add(struct rb_node * node,struct rb_root * tree,bool (* less)(struct rb_node *,const struct rb_node *))195 rb_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, 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  */
222 static __always_inline struct rb_node *
rb_find_add_cached(struct rb_node * node,struct rb_root_cached * tree,int (* cmp)(const struct rb_node * new,const struct rb_node * exist))223 rb_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, link);
246 	rb_insert_color_cached(node, 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  */
259 static __always_inline struct rb_node *
rb_find_add(struct rb_node * node,struct rb_root * tree,int (* cmp)(struct rb_node *,const struct rb_node *))260 rb_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, 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  */
295 static __always_inline struct rb_node *
rb_find_add_rcu(struct rb_node * node,struct rb_root * tree,int (* cmp)(struct rb_node *,const struct rb_node *))296 rb_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, 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  */
328 static __always_inline struct rb_node *
rb_find(const void * key,const struct rb_root * tree,int (* cmp)(const void * key,const struct rb_node *))329 rb_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  */
359 static __always_inline struct rb_node *
rb_find_rcu(const void * key,const struct rb_root * tree,int (* cmp)(const void * key,const struct rb_node *))360 rb_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  */
387 static __always_inline struct rb_node *
rb_find_first(const void * key,const struct rb_root * tree,int (* cmp)(const void * key,const struct rb_node *))388 rb_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  */
417 static __always_inline struct rb_node *
rb_next_match(const void * key,struct rb_node * node,int (* cmp)(const void * key,const struct rb_node *))418 rb_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