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1a59d1b8 | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
1da177e4 LT |
2 | /* |
3 | Red Black Trees | |
4 | (C) 1999 Andrea Arcangeli <andrea@suse.de> | |
5 | (C) 2002 David Woodhouse <dwmw2@infradead.org> | |
46b6135a ML |
6 | (C) 2012 Michel Lespinasse <walken@google.com> |
7 | ||
1da177e4 LT |
8 | |
9 | linux/lib/rbtree.c | |
10 | */ | |
11 | ||
9c079add | 12 | #include <linux/rbtree_augmented.h> |
8bc3bcc9 | 13 | #include <linux/export.h> |
1da177e4 | 14 | |
5bc9188a ML |
15 | /* |
16 | * red-black trees properties: http://en.wikipedia.org/wiki/Rbtree | |
17 | * | |
18 | * 1) A node is either red or black | |
19 | * 2) The root is black | |
20 | * 3) All leaves (NULL) are black | |
21 | * 4) Both children of every red node are black | |
22 | * 5) Every simple path from root to leaves contains the same number | |
23 | * of black nodes. | |
24 | * | |
25 | * 4 and 5 give the O(log n) guarantee, since 4 implies you cannot have two | |
26 | * consecutive red nodes in a path and every red node is therefore followed by | |
27 | * a black. So if B is the number of black nodes on every simple path (as per | |
28 | * 5), then the longest possible path due to 4 is 2B. | |
29 | * | |
30 | * We shall indicate color with case, where black nodes are uppercase and red | |
6280d235 ML |
31 | * nodes will be lowercase. Unknown color nodes shall be drawn as red within |
32 | * parentheses and have some accompanying text comment. | |
5bc9188a ML |
33 | */ |
34 | ||
d72da4a4 PZ |
35 | /* |
36 | * Notes on lockless lookups: | |
37 | * | |
38 | * All stores to the tree structure (rb_left and rb_right) must be done using | |
39 | * WRITE_ONCE(). And we must not inadvertently cause (temporary) loops in the | |
40 | * tree structure as seen in program order. | |
41 | * | |
42 | * These two requirements will allow lockless iteration of the tree -- not | |
43 | * correct iteration mind you, tree rotations are not atomic so a lookup might | |
44 | * miss entire subtrees. | |
45 | * | |
46 | * But they do guarantee that any such traversal will only see valid elements | |
47 | * and that it will indeed complete -- does not get stuck in a loop. | |
48 | * | |
49 | * It also guarantees that if the lookup returns an element it is the 'correct' | |
50 | * one. But not returning an element does _NOT_ mean it's not present. | |
51 | * | |
52 | * NOTE: | |
53 | * | |
54 | * Stores to __rb_parent_color are not important for simple lookups so those | |
55 | * are left undone as of now. Nor did I check for loops involving parent | |
56 | * pointers. | |
57 | */ | |
58 | ||
46b6135a ML |
59 | static inline void rb_set_black(struct rb_node *rb) |
60 | { | |
61 | rb->__rb_parent_color |= RB_BLACK; | |
62 | } | |
63 | ||
5bc9188a ML |
64 | static inline struct rb_node *rb_red_parent(struct rb_node *red) |
65 | { | |
66 | return (struct rb_node *)red->__rb_parent_color; | |
67 | } | |
68 | ||
5bc9188a ML |
69 | /* |
70 | * Helper function for rotations: | |
71 | * - old's parent and color get assigned to new | |
72 | * - old gets assigned new as a parent and 'color' as a color. | |
73 | */ | |
74 | static inline void | |
75 | __rb_rotate_set_parents(struct rb_node *old, struct rb_node *new, | |
76 | struct rb_root *root, int color) | |
77 | { | |
78 | struct rb_node *parent = rb_parent(old); | |
79 | new->__rb_parent_color = old->__rb_parent_color; | |
80 | rb_set_parent_color(old, new, color); | |
7abc704a | 81 | __rb_change_child(old, new, parent, root); |
5bc9188a ML |
82 | } |
83 | ||
14b94af0 ML |
84 | static __always_inline void |
85 | __rb_insert(struct rb_node *node, struct rb_root *root, | |
cd9e61ed | 86 | bool newleft, struct rb_node **leftmost, |
14b94af0 | 87 | void (*augment_rotate)(struct rb_node *old, struct rb_node *new)) |
1da177e4 | 88 | { |
5bc9188a | 89 | struct rb_node *parent = rb_red_parent(node), *gparent, *tmp; |
1da177e4 | 90 | |
cd9e61ed DB |
91 | if (newleft) |
92 | *leftmost = node; | |
93 | ||
6d58452d ML |
94 | while (true) { |
95 | /* | |
2aadf7fc | 96 | * Loop invariant: node is red. |
6d58452d | 97 | */ |
2aadf7fc DB |
98 | if (unlikely(!parent)) { |
99 | /* | |
100 | * The inserted node is root. Either this is the | |
101 | * first node, or we recursed at Case 1 below and | |
102 | * are no longer violating 4). | |
103 | */ | |
5bc9188a | 104 | rb_set_parent_color(node, NULL, RB_BLACK); |
6d58452d | 105 | break; |
2aadf7fc DB |
106 | } |
107 | ||
108 | /* | |
109 | * If there is a black parent, we are done. | |
110 | * Otherwise, take some corrective action as, | |
111 | * per 4), we don't want a red root or two | |
112 | * consecutive red nodes. | |
113 | */ | |
114 | if(rb_is_black(parent)) | |
6d58452d ML |
115 | break; |
116 | ||
5bc9188a ML |
117 | gparent = rb_red_parent(parent); |
118 | ||
59633abf ML |
119 | tmp = gparent->rb_right; |
120 | if (parent != tmp) { /* parent == gparent->rb_left */ | |
5bc9188a ML |
121 | if (tmp && rb_is_red(tmp)) { |
122 | /* | |
35dc67d7 | 123 | * Case 1 - node's uncle is red (color flips). |
5bc9188a ML |
124 | * |
125 | * G g | |
126 | * / \ / \ | |
127 | * p u --> P U | |
128 | * / / | |
1b9c53e8 | 129 | * n n |
5bc9188a ML |
130 | * |
131 | * However, since g's parent might be red, and | |
132 | * 4) does not allow this, we need to recurse | |
133 | * at g. | |
134 | */ | |
135 | rb_set_parent_color(tmp, gparent, RB_BLACK); | |
136 | rb_set_parent_color(parent, gparent, RB_BLACK); | |
137 | node = gparent; | |
138 | parent = rb_parent(node); | |
139 | rb_set_parent_color(node, parent, RB_RED); | |
140 | continue; | |
1da177e4 LT |
141 | } |
142 | ||
59633abf ML |
143 | tmp = parent->rb_right; |
144 | if (node == tmp) { | |
5bc9188a | 145 | /* |
35dc67d7 DB |
146 | * Case 2 - node's uncle is black and node is |
147 | * the parent's right child (left rotate at parent). | |
5bc9188a ML |
148 | * |
149 | * G G | |
150 | * / \ / \ | |
151 | * p U --> n U | |
152 | * \ / | |
153 | * n p | |
154 | * | |
155 | * This still leaves us in violation of 4), the | |
156 | * continuation into Case 3 will fix that. | |
157 | */ | |
d72da4a4 PZ |
158 | tmp = node->rb_left; |
159 | WRITE_ONCE(parent->rb_right, tmp); | |
160 | WRITE_ONCE(node->rb_left, parent); | |
5bc9188a ML |
161 | if (tmp) |
162 | rb_set_parent_color(tmp, parent, | |
163 | RB_BLACK); | |
164 | rb_set_parent_color(parent, node, RB_RED); | |
14b94af0 | 165 | augment_rotate(parent, node); |
1da177e4 | 166 | parent = node; |
59633abf | 167 | tmp = node->rb_right; |
1da177e4 LT |
168 | } |
169 | ||
5bc9188a | 170 | /* |
35dc67d7 DB |
171 | * Case 3 - node's uncle is black and node is |
172 | * the parent's left child (right rotate at gparent). | |
5bc9188a ML |
173 | * |
174 | * G P | |
175 | * / \ / \ | |
176 | * p U --> n g | |
177 | * / \ | |
178 | * n U | |
179 | */ | |
d72da4a4 PZ |
180 | WRITE_ONCE(gparent->rb_left, tmp); /* == parent->rb_right */ |
181 | WRITE_ONCE(parent->rb_right, gparent); | |
5bc9188a ML |
182 | if (tmp) |
183 | rb_set_parent_color(tmp, gparent, RB_BLACK); | |
184 | __rb_rotate_set_parents(gparent, parent, root, RB_RED); | |
14b94af0 | 185 | augment_rotate(gparent, parent); |
1f052865 | 186 | break; |
1da177e4 | 187 | } else { |
5bc9188a ML |
188 | tmp = gparent->rb_left; |
189 | if (tmp && rb_is_red(tmp)) { | |
190 | /* Case 1 - color flips */ | |
191 | rb_set_parent_color(tmp, gparent, RB_BLACK); | |
192 | rb_set_parent_color(parent, gparent, RB_BLACK); | |
193 | node = gparent; | |
194 | parent = rb_parent(node); | |
195 | rb_set_parent_color(node, parent, RB_RED); | |
196 | continue; | |
1da177e4 LT |
197 | } |
198 | ||
59633abf ML |
199 | tmp = parent->rb_left; |
200 | if (node == tmp) { | |
5bc9188a | 201 | /* Case 2 - right rotate at parent */ |
d72da4a4 PZ |
202 | tmp = node->rb_right; |
203 | WRITE_ONCE(parent->rb_left, tmp); | |
204 | WRITE_ONCE(node->rb_right, parent); | |
5bc9188a ML |
205 | if (tmp) |
206 | rb_set_parent_color(tmp, parent, | |
207 | RB_BLACK); | |
208 | rb_set_parent_color(parent, node, RB_RED); | |
14b94af0 | 209 | augment_rotate(parent, node); |
1da177e4 | 210 | parent = node; |
59633abf | 211 | tmp = node->rb_left; |
1da177e4 LT |
212 | } |
213 | ||
5bc9188a | 214 | /* Case 3 - left rotate at gparent */ |
d72da4a4 PZ |
215 | WRITE_ONCE(gparent->rb_right, tmp); /* == parent->rb_left */ |
216 | WRITE_ONCE(parent->rb_left, gparent); | |
5bc9188a ML |
217 | if (tmp) |
218 | rb_set_parent_color(tmp, gparent, RB_BLACK); | |
219 | __rb_rotate_set_parents(gparent, parent, root, RB_RED); | |
14b94af0 | 220 | augment_rotate(gparent, parent); |
1f052865 | 221 | break; |
1da177e4 LT |
222 | } |
223 | } | |
1da177e4 | 224 | } |
1da177e4 | 225 | |
3cb7a563 ML |
226 | /* |
227 | * Inline version for rb_erase() use - we want to be able to inline | |
228 | * and eliminate the dummy_rotate callback there | |
229 | */ | |
230 | static __always_inline void | |
231 | ____rb_erase_color(struct rb_node *parent, struct rb_root *root, | |
9c079add | 232 | void (*augment_rotate)(struct rb_node *old, struct rb_node *new)) |
1da177e4 | 233 | { |
46b6135a | 234 | struct rb_node *node = NULL, *sibling, *tmp1, *tmp2; |
1da177e4 | 235 | |
d6ff1273 ML |
236 | while (true) { |
237 | /* | |
46b6135a ML |
238 | * Loop invariants: |
239 | * - node is black (or NULL on first iteration) | |
240 | * - node is not the root (parent is not NULL) | |
241 | * - All leaf paths going through parent and node have a | |
242 | * black node count that is 1 lower than other leaf paths. | |
d6ff1273 | 243 | */ |
59633abf ML |
244 | sibling = parent->rb_right; |
245 | if (node != sibling) { /* node == parent->rb_left */ | |
6280d235 ML |
246 | if (rb_is_red(sibling)) { |
247 | /* | |
248 | * Case 1 - left rotate at parent | |
249 | * | |
250 | * P S | |
251 | * / \ / \ | |
252 | * N s --> p Sr | |
253 | * / \ / \ | |
254 | * Sl Sr N Sl | |
255 | */ | |
d72da4a4 PZ |
256 | tmp1 = sibling->rb_left; |
257 | WRITE_ONCE(parent->rb_right, tmp1); | |
258 | WRITE_ONCE(sibling->rb_left, parent); | |
6280d235 ML |
259 | rb_set_parent_color(tmp1, parent, RB_BLACK); |
260 | __rb_rotate_set_parents(parent, sibling, root, | |
261 | RB_RED); | |
9c079add | 262 | augment_rotate(parent, sibling); |
6280d235 | 263 | sibling = tmp1; |
1da177e4 | 264 | } |
6280d235 ML |
265 | tmp1 = sibling->rb_right; |
266 | if (!tmp1 || rb_is_black(tmp1)) { | |
267 | tmp2 = sibling->rb_left; | |
268 | if (!tmp2 || rb_is_black(tmp2)) { | |
269 | /* | |
270 | * Case 2 - sibling color flip | |
271 | * (p could be either color here) | |
272 | * | |
273 | * (p) (p) | |
274 | * / \ / \ | |
275 | * N S --> N s | |
276 | * / \ / \ | |
277 | * Sl Sr Sl Sr | |
278 | * | |
46b6135a ML |
279 | * This leaves us violating 5) which |
280 | * can be fixed by flipping p to black | |
281 | * if it was red, or by recursing at p. | |
282 | * p is red when coming from Case 1. | |
6280d235 ML |
283 | */ |
284 | rb_set_parent_color(sibling, parent, | |
285 | RB_RED); | |
46b6135a ML |
286 | if (rb_is_red(parent)) |
287 | rb_set_black(parent); | |
288 | else { | |
289 | node = parent; | |
290 | parent = rb_parent(node); | |
291 | if (parent) | |
292 | continue; | |
293 | } | |
294 | break; | |
1da177e4 | 295 | } |
6280d235 ML |
296 | /* |
297 | * Case 3 - right rotate at sibling | |
298 | * (p could be either color here) | |
299 | * | |
300 | * (p) (p) | |
301 | * / \ / \ | |
ce093a04 | 302 | * N S --> N sl |
6280d235 | 303 | * / \ \ |
ce093a04 | 304 | * sl Sr S |
6280d235 ML |
305 | * \ |
306 | * Sr | |
ce093a04 JC |
307 | * |
308 | * Note: p might be red, and then both | |
309 | * p and sl are red after rotation(which | |
310 | * breaks property 4). This is fixed in | |
311 | * Case 4 (in __rb_rotate_set_parents() | |
312 | * which set sl the color of p | |
313 | * and set p RB_BLACK) | |
314 | * | |
315 | * (p) (sl) | |
316 | * / \ / \ | |
317 | * N sl --> P S | |
318 | * \ / \ | |
319 | * S N Sr | |
320 | * \ | |
321 | * Sr | |
6280d235 | 322 | */ |
d72da4a4 PZ |
323 | tmp1 = tmp2->rb_right; |
324 | WRITE_ONCE(sibling->rb_left, tmp1); | |
325 | WRITE_ONCE(tmp2->rb_right, sibling); | |
326 | WRITE_ONCE(parent->rb_right, tmp2); | |
6280d235 ML |
327 | if (tmp1) |
328 | rb_set_parent_color(tmp1, sibling, | |
329 | RB_BLACK); | |
9c079add | 330 | augment_rotate(sibling, tmp2); |
6280d235 ML |
331 | tmp1 = sibling; |
332 | sibling = tmp2; | |
1da177e4 | 333 | } |
6280d235 ML |
334 | /* |
335 | * Case 4 - left rotate at parent + color flips | |
336 | * (p and sl could be either color here. | |
337 | * After rotation, p becomes black, s acquires | |
338 | * p's color, and sl keeps its color) | |
339 | * | |
340 | * (p) (s) | |
341 | * / \ / \ | |
342 | * N S --> P Sr | |
343 | * / \ / \ | |
344 | * (sl) sr N (sl) | |
345 | */ | |
d72da4a4 PZ |
346 | tmp2 = sibling->rb_left; |
347 | WRITE_ONCE(parent->rb_right, tmp2); | |
348 | WRITE_ONCE(sibling->rb_left, parent); | |
6280d235 ML |
349 | rb_set_parent_color(tmp1, sibling, RB_BLACK); |
350 | if (tmp2) | |
351 | rb_set_parent(tmp2, parent); | |
352 | __rb_rotate_set_parents(parent, sibling, root, | |
353 | RB_BLACK); | |
9c079add | 354 | augment_rotate(parent, sibling); |
e125d147 | 355 | break; |
d6ff1273 | 356 | } else { |
6280d235 ML |
357 | sibling = parent->rb_left; |
358 | if (rb_is_red(sibling)) { | |
359 | /* Case 1 - right rotate at parent */ | |
d72da4a4 PZ |
360 | tmp1 = sibling->rb_right; |
361 | WRITE_ONCE(parent->rb_left, tmp1); | |
362 | WRITE_ONCE(sibling->rb_right, parent); | |
6280d235 ML |
363 | rb_set_parent_color(tmp1, parent, RB_BLACK); |
364 | __rb_rotate_set_parents(parent, sibling, root, | |
365 | RB_RED); | |
9c079add | 366 | augment_rotate(parent, sibling); |
6280d235 | 367 | sibling = tmp1; |
1da177e4 | 368 | } |
6280d235 ML |
369 | tmp1 = sibling->rb_left; |
370 | if (!tmp1 || rb_is_black(tmp1)) { | |
371 | tmp2 = sibling->rb_right; | |
372 | if (!tmp2 || rb_is_black(tmp2)) { | |
373 | /* Case 2 - sibling color flip */ | |
374 | rb_set_parent_color(sibling, parent, | |
375 | RB_RED); | |
46b6135a ML |
376 | if (rb_is_red(parent)) |
377 | rb_set_black(parent); | |
378 | else { | |
379 | node = parent; | |
380 | parent = rb_parent(node); | |
381 | if (parent) | |
382 | continue; | |
383 | } | |
384 | break; | |
1da177e4 | 385 | } |
ce093a04 | 386 | /* Case 3 - left rotate at sibling */ |
d72da4a4 PZ |
387 | tmp1 = tmp2->rb_left; |
388 | WRITE_ONCE(sibling->rb_right, tmp1); | |
389 | WRITE_ONCE(tmp2->rb_left, sibling); | |
390 | WRITE_ONCE(parent->rb_left, tmp2); | |
6280d235 ML |
391 | if (tmp1) |
392 | rb_set_parent_color(tmp1, sibling, | |
393 | RB_BLACK); | |
9c079add | 394 | augment_rotate(sibling, tmp2); |
6280d235 ML |
395 | tmp1 = sibling; |
396 | sibling = tmp2; | |
1da177e4 | 397 | } |
ce093a04 | 398 | /* Case 4 - right rotate at parent + color flips */ |
d72da4a4 PZ |
399 | tmp2 = sibling->rb_right; |
400 | WRITE_ONCE(parent->rb_left, tmp2); | |
401 | WRITE_ONCE(sibling->rb_right, parent); | |
6280d235 ML |
402 | rb_set_parent_color(tmp1, sibling, RB_BLACK); |
403 | if (tmp2) | |
404 | rb_set_parent(tmp2, parent); | |
405 | __rb_rotate_set_parents(parent, sibling, root, | |
406 | RB_BLACK); | |
9c079add | 407 | augment_rotate(parent, sibling); |
e125d147 | 408 | break; |
1da177e4 LT |
409 | } |
410 | } | |
1da177e4 | 411 | } |
3cb7a563 ML |
412 | |
413 | /* Non-inline version for rb_erase_augmented() use */ | |
414 | void __rb_erase_color(struct rb_node *parent, struct rb_root *root, | |
415 | void (*augment_rotate)(struct rb_node *old, struct rb_node *new)) | |
416 | { | |
417 | ____rb_erase_color(parent, root, augment_rotate); | |
418 | } | |
9c079add | 419 | EXPORT_SYMBOL(__rb_erase_color); |
14b94af0 ML |
420 | |
421 | /* | |
422 | * Non-augmented rbtree manipulation functions. | |
423 | * | |
424 | * We use dummy augmented callbacks here, and have the compiler optimize them | |
425 | * out of the rb_insert_color() and rb_erase() function definitions. | |
426 | */ | |
427 | ||
428 | static inline void dummy_propagate(struct rb_node *node, struct rb_node *stop) {} | |
429 | static inline void dummy_copy(struct rb_node *old, struct rb_node *new) {} | |
430 | static inline void dummy_rotate(struct rb_node *old, struct rb_node *new) {} | |
431 | ||
432 | static const struct rb_augment_callbacks dummy_callbacks = { | |
f231aebf KC |
433 | .propagate = dummy_propagate, |
434 | .copy = dummy_copy, | |
435 | .rotate = dummy_rotate | |
14b94af0 ML |
436 | }; |
437 | ||
438 | void rb_insert_color(struct rb_node *node, struct rb_root *root) | |
439 | { | |
cd9e61ed | 440 | __rb_insert(node, root, false, NULL, dummy_rotate); |
14b94af0 ML |
441 | } |
442 | EXPORT_SYMBOL(rb_insert_color); | |
443 | ||
444 | void rb_erase(struct rb_node *node, struct rb_root *root) | |
445 | { | |
3cb7a563 | 446 | struct rb_node *rebalance; |
cd9e61ed DB |
447 | rebalance = __rb_erase_augmented(node, root, |
448 | NULL, &dummy_callbacks); | |
3cb7a563 ML |
449 | if (rebalance) |
450 | ____rb_erase_color(rebalance, root, dummy_rotate); | |
1da177e4 LT |
451 | } |
452 | EXPORT_SYMBOL(rb_erase); | |
453 | ||
cd9e61ed DB |
454 | void rb_insert_color_cached(struct rb_node *node, |
455 | struct rb_root_cached *root, bool leftmost) | |
456 | { | |
457 | __rb_insert(node, &root->rb_root, leftmost, | |
458 | &root->rb_leftmost, dummy_rotate); | |
459 | } | |
460 | EXPORT_SYMBOL(rb_insert_color_cached); | |
461 | ||
462 | void rb_erase_cached(struct rb_node *node, struct rb_root_cached *root) | |
463 | { | |
464 | struct rb_node *rebalance; | |
465 | rebalance = __rb_erase_augmented(node, &root->rb_root, | |
466 | &root->rb_leftmost, &dummy_callbacks); | |
467 | if (rebalance) | |
468 | ____rb_erase_color(rebalance, &root->rb_root, dummy_rotate); | |
469 | } | |
470 | EXPORT_SYMBOL(rb_erase_cached); | |
471 | ||
14b94af0 ML |
472 | /* |
473 | * Augmented rbtree manipulation functions. | |
474 | * | |
475 | * This instantiates the same __always_inline functions as in the non-augmented | |
476 | * case, but this time with user-defined callbacks. | |
477 | */ | |
478 | ||
479 | void __rb_insert_augmented(struct rb_node *node, struct rb_root *root, | |
cd9e61ed | 480 | bool newleft, struct rb_node **leftmost, |
14b94af0 ML |
481 | void (*augment_rotate)(struct rb_node *old, struct rb_node *new)) |
482 | { | |
cd9e61ed | 483 | __rb_insert(node, root, newleft, leftmost, augment_rotate); |
14b94af0 ML |
484 | } |
485 | EXPORT_SYMBOL(__rb_insert_augmented); | |
486 | ||
1da177e4 LT |
487 | /* |
488 | * This function returns the first node (in sort order) of the tree. | |
489 | */ | |
f4b477c4 | 490 | struct rb_node *rb_first(const struct rb_root *root) |
1da177e4 LT |
491 | { |
492 | struct rb_node *n; | |
493 | ||
494 | n = root->rb_node; | |
495 | if (!n) | |
496 | return NULL; | |
497 | while (n->rb_left) | |
498 | n = n->rb_left; | |
499 | return n; | |
500 | } | |
501 | EXPORT_SYMBOL(rb_first); | |
502 | ||
f4b477c4 | 503 | struct rb_node *rb_last(const struct rb_root *root) |
1da177e4 LT |
504 | { |
505 | struct rb_node *n; | |
506 | ||
507 | n = root->rb_node; | |
508 | if (!n) | |
509 | return NULL; | |
510 | while (n->rb_right) | |
511 | n = n->rb_right; | |
512 | return n; | |
513 | } | |
514 | EXPORT_SYMBOL(rb_last); | |
515 | ||
f4b477c4 | 516 | struct rb_node *rb_next(const struct rb_node *node) |
1da177e4 | 517 | { |
55a98102 DW |
518 | struct rb_node *parent; |
519 | ||
4c199a93 | 520 | if (RB_EMPTY_NODE(node)) |
10fd48f2 JA |
521 | return NULL; |
522 | ||
7ce6ff9e ML |
523 | /* |
524 | * If we have a right-hand child, go down and then left as far | |
525 | * as we can. | |
526 | */ | |
1da177e4 | 527 | if (node->rb_right) { |
cd9e61ed | 528 | node = node->rb_right; |
1da177e4 LT |
529 | while (node->rb_left) |
530 | node=node->rb_left; | |
f4b477c4 | 531 | return (struct rb_node *)node; |
1da177e4 LT |
532 | } |
533 | ||
7ce6ff9e ML |
534 | /* |
535 | * No right-hand children. Everything down and left is smaller than us, | |
536 | * so any 'next' node must be in the general direction of our parent. | |
537 | * Go up the tree; any time the ancestor is a right-hand child of its | |
538 | * parent, keep going up. First time it's a left-hand child of its | |
539 | * parent, said parent is our 'next' node. | |
540 | */ | |
55a98102 DW |
541 | while ((parent = rb_parent(node)) && node == parent->rb_right) |
542 | node = parent; | |
1da177e4 | 543 | |
55a98102 | 544 | return parent; |
1da177e4 LT |
545 | } |
546 | EXPORT_SYMBOL(rb_next); | |
547 | ||
f4b477c4 | 548 | struct rb_node *rb_prev(const struct rb_node *node) |
1da177e4 | 549 | { |
55a98102 DW |
550 | struct rb_node *parent; |
551 | ||
4c199a93 | 552 | if (RB_EMPTY_NODE(node)) |
10fd48f2 JA |
553 | return NULL; |
554 | ||
7ce6ff9e ML |
555 | /* |
556 | * If we have a left-hand child, go down and then right as far | |
557 | * as we can. | |
558 | */ | |
1da177e4 | 559 | if (node->rb_left) { |
cd9e61ed | 560 | node = node->rb_left; |
1da177e4 LT |
561 | while (node->rb_right) |
562 | node=node->rb_right; | |
f4b477c4 | 563 | return (struct rb_node *)node; |
1da177e4 LT |
564 | } |
565 | ||
7ce6ff9e ML |
566 | /* |
567 | * No left-hand children. Go up till we find an ancestor which | |
568 | * is a right-hand child of its parent. | |
569 | */ | |
55a98102 DW |
570 | while ((parent = rb_parent(node)) && node == parent->rb_left) |
571 | node = parent; | |
1da177e4 | 572 | |
55a98102 | 573 | return parent; |
1da177e4 LT |
574 | } |
575 | EXPORT_SYMBOL(rb_prev); | |
576 | ||
577 | void rb_replace_node(struct rb_node *victim, struct rb_node *new, | |
578 | struct rb_root *root) | |
579 | { | |
55a98102 | 580 | struct rb_node *parent = rb_parent(victim); |
1da177e4 | 581 | |
c1adf200 DH |
582 | /* Copy the pointers/colour from the victim to the replacement */ |
583 | *new = *victim; | |
584 | ||
1da177e4 | 585 | /* Set the surrounding nodes to point to the replacement */ |
1da177e4 | 586 | if (victim->rb_left) |
55a98102 | 587 | rb_set_parent(victim->rb_left, new); |
1da177e4 | 588 | if (victim->rb_right) |
55a98102 | 589 | rb_set_parent(victim->rb_right, new); |
c1adf200 DH |
590 | __rb_change_child(victim, new, parent, root); |
591 | } | |
592 | EXPORT_SYMBOL(rb_replace_node); | |
593 | ||
338f1d9d CW |
594 | void rb_replace_node_cached(struct rb_node *victim, struct rb_node *new, |
595 | struct rb_root_cached *root) | |
596 | { | |
597 | rb_replace_node(victim, new, &root->rb_root); | |
598 | ||
599 | if (root->rb_leftmost == victim) | |
600 | root->rb_leftmost = new; | |
601 | } | |
602 | EXPORT_SYMBOL(rb_replace_node_cached); | |
603 | ||
c1adf200 DH |
604 | void rb_replace_node_rcu(struct rb_node *victim, struct rb_node *new, |
605 | struct rb_root *root) | |
606 | { | |
607 | struct rb_node *parent = rb_parent(victim); | |
1da177e4 LT |
608 | |
609 | /* Copy the pointers/colour from the victim to the replacement */ | |
610 | *new = *victim; | |
c1adf200 DH |
611 | |
612 | /* Set the surrounding nodes to point to the replacement */ | |
613 | if (victim->rb_left) | |
614 | rb_set_parent(victim->rb_left, new); | |
615 | if (victim->rb_right) | |
616 | rb_set_parent(victim->rb_right, new); | |
617 | ||
618 | /* Set the parent's pointer to the new node last after an RCU barrier | |
619 | * so that the pointers onwards are seen to be set correctly when doing | |
620 | * an RCU walk over the tree. | |
621 | */ | |
622 | __rb_change_child_rcu(victim, new, parent, root); | |
1da177e4 | 623 | } |
c1adf200 | 624 | EXPORT_SYMBOL(rb_replace_node_rcu); |
9dee5c51 CS |
625 | |
626 | static struct rb_node *rb_left_deepest_node(const struct rb_node *node) | |
627 | { | |
628 | for (;;) { | |
629 | if (node->rb_left) | |
630 | node = node->rb_left; | |
631 | else if (node->rb_right) | |
632 | node = node->rb_right; | |
633 | else | |
634 | return (struct rb_node *)node; | |
635 | } | |
636 | } | |
637 | ||
638 | struct rb_node *rb_next_postorder(const struct rb_node *node) | |
639 | { | |
640 | const struct rb_node *parent; | |
641 | if (!node) | |
642 | return NULL; | |
643 | parent = rb_parent(node); | |
644 | ||
645 | /* If we're sitting on node, we've already seen our children */ | |
646 | if (parent && node == parent->rb_left && parent->rb_right) { | |
647 | /* If we are the parent's left node, go to the parent's right | |
648 | * node then all the way down to the left */ | |
649 | return rb_left_deepest_node(parent->rb_right); | |
650 | } else | |
651 | /* Otherwise we are the parent's right node, and the parent | |
652 | * should be next */ | |
653 | return (struct rb_node *)parent; | |
654 | } | |
655 | EXPORT_SYMBOL(rb_next_postorder); | |
656 | ||
657 | struct rb_node *rb_first_postorder(const struct rb_root *root) | |
658 | { | |
659 | if (!root->rb_node) | |
660 | return NULL; | |
661 | ||
662 | return rb_left_deepest_node(root->rb_node); | |
663 | } | |
664 | EXPORT_SYMBOL(rb_first_postorder); |