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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 Red Black Trees
3 (C) 1999 Andrea Arcangeli <andrea@suse.de>
4 (C) 2002 David Woodhouse <dwmw2@infradead.org>
Michel Lespinasse46b61352012-10-08 16:31:11 -07005 (C) 2012 Michel Lespinasse <walken@google.com>
6
Linus Torvalds1da177e2005-04-16 15:20:36 -07007 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2 of the License, or
10 (at your option) any later version.
11
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
16
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software
19 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20
21 linux/lib/rbtree.c
22*/
23
Michel Lespinasse9c079ad2012-10-08 16:31:33 -070024#include <linux/rbtree_augmented.h>
Paul Gortmaker8bc3bcc2011-11-16 21:29:17 -050025#include <linux/export.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070026
Michel Lespinasse5bc91882012-10-08 16:30:47 -070027/*
28 * red-black trees properties: http://en.wikipedia.org/wiki/Rbtree
29 *
30 * 1) A node is either red or black
31 * 2) The root is black
32 * 3) All leaves (NULL) are black
33 * 4) Both children of every red node are black
34 * 5) Every simple path from root to leaves contains the same number
35 * of black nodes.
36 *
37 * 4 and 5 give the O(log n) guarantee, since 4 implies you cannot have two
38 * consecutive red nodes in a path and every red node is therefore followed by
39 * a black. So if B is the number of black nodes on every simple path (as per
40 * 5), then the longest possible path due to 4 is 2B.
41 *
42 * We shall indicate color with case, where black nodes are uppercase and red
Michel Lespinasse6280d232012-10-08 16:30:57 -070043 * nodes will be lowercase. Unknown color nodes shall be drawn as red within
44 * parentheses and have some accompanying text comment.
Michel Lespinasse5bc91882012-10-08 16:30:47 -070045 */
46
Michel Lespinasse46b61352012-10-08 16:31:11 -070047static inline void rb_set_black(struct rb_node *rb)
48{
49 rb->__rb_parent_color |= RB_BLACK;
50}
51
Michel Lespinasse5bc91882012-10-08 16:30:47 -070052static inline struct rb_node *rb_red_parent(struct rb_node *red)
53{
54 return (struct rb_node *)red->__rb_parent_color;
55}
56
Michel Lespinasse5bc91882012-10-08 16:30:47 -070057/*
58 * Helper function for rotations:
59 * - old's parent and color get assigned to new
60 * - old gets assigned new as a parent and 'color' as a color.
61 */
62static inline void
63__rb_rotate_set_parents(struct rb_node *old, struct rb_node *new,
64 struct rb_root *root, int color)
65{
66 struct rb_node *parent = rb_parent(old);
67 new->__rb_parent_color = old->__rb_parent_color;
68 rb_set_parent_color(old, new, color);
Michel Lespinasse7abc7042012-10-08 16:31:07 -070069 __rb_change_child(old, new, parent, root);
Michel Lespinasse5bc91882012-10-08 16:30:47 -070070}
71
Michel Lespinasse14b94af2012-10-08 16:31:17 -070072static __always_inline void
73__rb_insert(struct rb_node *node, struct rb_root *root,
74 void (*augment_rotate)(struct rb_node *old, struct rb_node *new))
Linus Torvalds1da177e2005-04-16 15:20:36 -070075{
Michel Lespinasse5bc91882012-10-08 16:30:47 -070076 struct rb_node *parent = rb_red_parent(node), *gparent, *tmp;
Linus Torvalds1da177e2005-04-16 15:20:36 -070077
Michel Lespinasse6d584522012-10-08 16:30:44 -070078 while (true) {
79 /*
80 * Loop invariant: node is red
81 *
82 * If there is a black parent, we are done.
83 * Otherwise, take some corrective action as we don't
84 * want a red root or two consecutive red nodes.
85 */
Michel Lespinasse6d584522012-10-08 16:30:44 -070086 if (!parent) {
Michel Lespinasse5bc91882012-10-08 16:30:47 -070087 rb_set_parent_color(node, NULL, RB_BLACK);
Michel Lespinasse6d584522012-10-08 16:30:44 -070088 break;
89 } else if (rb_is_black(parent))
90 break;
91
Michel Lespinasse5bc91882012-10-08 16:30:47 -070092 gparent = rb_red_parent(parent);
Linus Torvalds1da177e2005-04-16 15:20:36 -070093
Michel Lespinasse59633ab2012-10-08 16:31:02 -070094 tmp = gparent->rb_right;
95 if (parent != tmp) { /* parent == gparent->rb_left */
Michel Lespinasse5bc91882012-10-08 16:30:47 -070096 if (tmp && rb_is_red(tmp)) {
97 /*
98 * Case 1 - color flips
99 *
100 * G g
101 * / \ / \
102 * p u --> P U
103 * / /
104 * n N
105 *
106 * However, since g's parent might be red, and
107 * 4) does not allow this, we need to recurse
108 * at g.
109 */
110 rb_set_parent_color(tmp, gparent, RB_BLACK);
111 rb_set_parent_color(parent, gparent, RB_BLACK);
112 node = gparent;
113 parent = rb_parent(node);
114 rb_set_parent_color(node, parent, RB_RED);
115 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700116 }
117
Michel Lespinasse59633ab2012-10-08 16:31:02 -0700118 tmp = parent->rb_right;
119 if (node == tmp) {
Michel Lespinasse5bc91882012-10-08 16:30:47 -0700120 /*
121 * Case 2 - left rotate at parent
122 *
123 * G G
124 * / \ / \
125 * p U --> n U
126 * \ /
127 * n p
128 *
129 * This still leaves us in violation of 4), the
130 * continuation into Case 3 will fix that.
131 */
132 parent->rb_right = tmp = node->rb_left;
133 node->rb_left = parent;
134 if (tmp)
135 rb_set_parent_color(tmp, parent,
136 RB_BLACK);
137 rb_set_parent_color(parent, node, RB_RED);
Michel Lespinasse14b94af2012-10-08 16:31:17 -0700138 augment_rotate(parent, node);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700139 parent = node;
Michel Lespinasse59633ab2012-10-08 16:31:02 -0700140 tmp = node->rb_right;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700141 }
142
Michel Lespinasse5bc91882012-10-08 16:30:47 -0700143 /*
144 * Case 3 - right rotate at gparent
145 *
146 * G P
147 * / \ / \
148 * p U --> n g
149 * / \
150 * n U
151 */
Michel Lespinasse59633ab2012-10-08 16:31:02 -0700152 gparent->rb_left = tmp; /* == parent->rb_right */
Michel Lespinasse5bc91882012-10-08 16:30:47 -0700153 parent->rb_right = gparent;
154 if (tmp)
155 rb_set_parent_color(tmp, gparent, RB_BLACK);
156 __rb_rotate_set_parents(gparent, parent, root, RB_RED);
Michel Lespinasse14b94af2012-10-08 16:31:17 -0700157 augment_rotate(gparent, parent);
Michel Lespinasse1f052862012-10-08 16:30:42 -0700158 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700159 } else {
Michel Lespinasse5bc91882012-10-08 16:30:47 -0700160 tmp = gparent->rb_left;
161 if (tmp && rb_is_red(tmp)) {
162 /* Case 1 - color flips */
163 rb_set_parent_color(tmp, gparent, RB_BLACK);
164 rb_set_parent_color(parent, gparent, RB_BLACK);
165 node = gparent;
166 parent = rb_parent(node);
167 rb_set_parent_color(node, parent, RB_RED);
168 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700169 }
170
Michel Lespinasse59633ab2012-10-08 16:31:02 -0700171 tmp = parent->rb_left;
172 if (node == tmp) {
Michel Lespinasse5bc91882012-10-08 16:30:47 -0700173 /* Case 2 - right rotate at parent */
174 parent->rb_left = tmp = node->rb_right;
175 node->rb_right = parent;
176 if (tmp)
177 rb_set_parent_color(tmp, parent,
178 RB_BLACK);
179 rb_set_parent_color(parent, node, RB_RED);
Michel Lespinasse14b94af2012-10-08 16:31:17 -0700180 augment_rotate(parent, node);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700181 parent = node;
Michel Lespinasse59633ab2012-10-08 16:31:02 -0700182 tmp = node->rb_left;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700183 }
184
Michel Lespinasse5bc91882012-10-08 16:30:47 -0700185 /* Case 3 - left rotate at gparent */
Michel Lespinasse59633ab2012-10-08 16:31:02 -0700186 gparent->rb_right = tmp; /* == parent->rb_left */
Michel Lespinasse5bc91882012-10-08 16:30:47 -0700187 parent->rb_left = gparent;
188 if (tmp)
189 rb_set_parent_color(tmp, gparent, RB_BLACK);
190 __rb_rotate_set_parents(gparent, parent, root, RB_RED);
Michel Lespinasse14b94af2012-10-08 16:31:17 -0700191 augment_rotate(gparent, parent);
Michel Lespinasse1f052862012-10-08 16:30:42 -0700192 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700193 }
194 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700195}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700196
Michel Lespinasse3cb7a562013-01-11 14:32:20 -0800197/*
198 * Inline version for rb_erase() use - we want to be able to inline
199 * and eliminate the dummy_rotate callback there
200 */
201static __always_inline void
202____rb_erase_color(struct rb_node *parent, struct rb_root *root,
Michel Lespinasse9c079ad2012-10-08 16:31:33 -0700203 void (*augment_rotate)(struct rb_node *old, struct rb_node *new))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700204{
Michel Lespinasse46b61352012-10-08 16:31:11 -0700205 struct rb_node *node = NULL, *sibling, *tmp1, *tmp2;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700206
Michel Lespinassed6ff1272012-10-08 16:30:50 -0700207 while (true) {
208 /*
Michel Lespinasse46b61352012-10-08 16:31:11 -0700209 * Loop invariants:
210 * - node is black (or NULL on first iteration)
211 * - node is not the root (parent is not NULL)
212 * - All leaf paths going through parent and node have a
213 * black node count that is 1 lower than other leaf paths.
Michel Lespinassed6ff1272012-10-08 16:30:50 -0700214 */
Michel Lespinasse59633ab2012-10-08 16:31:02 -0700215 sibling = parent->rb_right;
216 if (node != sibling) { /* node == parent->rb_left */
Michel Lespinasse6280d232012-10-08 16:30:57 -0700217 if (rb_is_red(sibling)) {
218 /*
219 * Case 1 - left rotate at parent
220 *
221 * P S
222 * / \ / \
223 * N s --> p Sr
224 * / \ / \
225 * Sl Sr N Sl
226 */
227 parent->rb_right = tmp1 = sibling->rb_left;
228 sibling->rb_left = parent;
229 rb_set_parent_color(tmp1, parent, RB_BLACK);
230 __rb_rotate_set_parents(parent, sibling, root,
231 RB_RED);
Michel Lespinasse9c079ad2012-10-08 16:31:33 -0700232 augment_rotate(parent, sibling);
Michel Lespinasse6280d232012-10-08 16:30:57 -0700233 sibling = tmp1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700234 }
Michel Lespinasse6280d232012-10-08 16:30:57 -0700235 tmp1 = sibling->rb_right;
236 if (!tmp1 || rb_is_black(tmp1)) {
237 tmp2 = sibling->rb_left;
238 if (!tmp2 || rb_is_black(tmp2)) {
239 /*
240 * Case 2 - sibling color flip
241 * (p could be either color here)
242 *
243 * (p) (p)
244 * / \ / \
245 * N S --> N s
246 * / \ / \
247 * Sl Sr Sl Sr
248 *
Michel Lespinasse46b61352012-10-08 16:31:11 -0700249 * This leaves us violating 5) which
250 * can be fixed by flipping p to black
251 * if it was red, or by recursing at p.
252 * p is red when coming from Case 1.
Michel Lespinasse6280d232012-10-08 16:30:57 -0700253 */
254 rb_set_parent_color(sibling, parent,
255 RB_RED);
Michel Lespinasse46b61352012-10-08 16:31:11 -0700256 if (rb_is_red(parent))
257 rb_set_black(parent);
258 else {
259 node = parent;
260 parent = rb_parent(node);
261 if (parent)
262 continue;
263 }
264 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700265 }
Michel Lespinasse6280d232012-10-08 16:30:57 -0700266 /*
267 * Case 3 - right rotate at sibling
268 * (p could be either color here)
269 *
270 * (p) (p)
271 * / \ / \
272 * N S --> N Sl
273 * / \ \
274 * sl Sr s
275 * \
276 * Sr
277 */
278 sibling->rb_left = tmp1 = tmp2->rb_right;
279 tmp2->rb_right = sibling;
280 parent->rb_right = tmp2;
281 if (tmp1)
282 rb_set_parent_color(tmp1, sibling,
283 RB_BLACK);
Michel Lespinasse9c079ad2012-10-08 16:31:33 -0700284 augment_rotate(sibling, tmp2);
Michel Lespinasse6280d232012-10-08 16:30:57 -0700285 tmp1 = sibling;
286 sibling = tmp2;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700287 }
Michel Lespinasse6280d232012-10-08 16:30:57 -0700288 /*
289 * Case 4 - left rotate at parent + color flips
290 * (p and sl could be either color here.
291 * After rotation, p becomes black, s acquires
292 * p's color, and sl keeps its color)
293 *
294 * (p) (s)
295 * / \ / \
296 * N S --> P Sr
297 * / \ / \
298 * (sl) sr N (sl)
299 */
300 parent->rb_right = tmp2 = sibling->rb_left;
301 sibling->rb_left = parent;
302 rb_set_parent_color(tmp1, sibling, RB_BLACK);
303 if (tmp2)
304 rb_set_parent(tmp2, parent);
305 __rb_rotate_set_parents(parent, sibling, root,
306 RB_BLACK);
Michel Lespinasse9c079ad2012-10-08 16:31:33 -0700307 augment_rotate(parent, sibling);
Michel Lespinassee125d142012-10-08 16:30:54 -0700308 break;
Michel Lespinassed6ff1272012-10-08 16:30:50 -0700309 } else {
Michel Lespinasse6280d232012-10-08 16:30:57 -0700310 sibling = parent->rb_left;
311 if (rb_is_red(sibling)) {
312 /* Case 1 - right rotate at parent */
313 parent->rb_left = tmp1 = sibling->rb_right;
314 sibling->rb_right = parent;
315 rb_set_parent_color(tmp1, parent, RB_BLACK);
316 __rb_rotate_set_parents(parent, sibling, root,
317 RB_RED);
Michel Lespinasse9c079ad2012-10-08 16:31:33 -0700318 augment_rotate(parent, sibling);
Michel Lespinasse6280d232012-10-08 16:30:57 -0700319 sibling = tmp1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700320 }
Michel Lespinasse6280d232012-10-08 16:30:57 -0700321 tmp1 = sibling->rb_left;
322 if (!tmp1 || rb_is_black(tmp1)) {
323 tmp2 = sibling->rb_right;
324 if (!tmp2 || rb_is_black(tmp2)) {
325 /* Case 2 - sibling color flip */
326 rb_set_parent_color(sibling, parent,
327 RB_RED);
Michel Lespinasse46b61352012-10-08 16:31:11 -0700328 if (rb_is_red(parent))
329 rb_set_black(parent);
330 else {
331 node = parent;
332 parent = rb_parent(node);
333 if (parent)
334 continue;
335 }
336 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700337 }
Michel Lespinasse6280d232012-10-08 16:30:57 -0700338 /* Case 3 - right rotate at sibling */
339 sibling->rb_right = tmp1 = tmp2->rb_left;
340 tmp2->rb_left = sibling;
341 parent->rb_left = tmp2;
342 if (tmp1)
343 rb_set_parent_color(tmp1, sibling,
344 RB_BLACK);
Michel Lespinasse9c079ad2012-10-08 16:31:33 -0700345 augment_rotate(sibling, tmp2);
Michel Lespinasse6280d232012-10-08 16:30:57 -0700346 tmp1 = sibling;
347 sibling = tmp2;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700348 }
Michel Lespinasse6280d232012-10-08 16:30:57 -0700349 /* Case 4 - left rotate at parent + color flips */
350 parent->rb_left = tmp2 = sibling->rb_right;
351 sibling->rb_right = parent;
352 rb_set_parent_color(tmp1, sibling, RB_BLACK);
353 if (tmp2)
354 rb_set_parent(tmp2, parent);
355 __rb_rotate_set_parents(parent, sibling, root,
356 RB_BLACK);
Michel Lespinasse9c079ad2012-10-08 16:31:33 -0700357 augment_rotate(parent, sibling);
Michel Lespinassee125d142012-10-08 16:30:54 -0700358 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700359 }
360 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700361}
Michel Lespinasse3cb7a562013-01-11 14:32:20 -0800362
363/* Non-inline version for rb_erase_augmented() use */
364void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
365 void (*augment_rotate)(struct rb_node *old, struct rb_node *new))
366{
367 ____rb_erase_color(parent, root, augment_rotate);
368}
Michel Lespinasse9c079ad2012-10-08 16:31:33 -0700369EXPORT_SYMBOL(__rb_erase_color);
Michel Lespinasse14b94af2012-10-08 16:31:17 -0700370
371/*
372 * Non-augmented rbtree manipulation functions.
373 *
374 * We use dummy augmented callbacks here, and have the compiler optimize them
375 * out of the rb_insert_color() and rb_erase() function definitions.
376 */
377
378static inline void dummy_propagate(struct rb_node *node, struct rb_node *stop) {}
379static inline void dummy_copy(struct rb_node *old, struct rb_node *new) {}
380static inline void dummy_rotate(struct rb_node *old, struct rb_node *new) {}
381
382static const struct rb_augment_callbacks dummy_callbacks = {
383 dummy_propagate, dummy_copy, dummy_rotate
384};
385
386void rb_insert_color(struct rb_node *node, struct rb_root *root)
387{
388 __rb_insert(node, root, dummy_rotate);
389}
390EXPORT_SYMBOL(rb_insert_color);
391
392void rb_erase(struct rb_node *node, struct rb_root *root)
393{
Michel Lespinasse3cb7a562013-01-11 14:32:20 -0800394 struct rb_node *rebalance;
395 rebalance = __rb_erase_augmented(node, root, &dummy_callbacks);
396 if (rebalance)
397 ____rb_erase_color(rebalance, root, dummy_rotate);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700398}
399EXPORT_SYMBOL(rb_erase);
400
Michel Lespinasse14b94af2012-10-08 16:31:17 -0700401/*
402 * Augmented rbtree manipulation functions.
403 *
404 * This instantiates the same __always_inline functions as in the non-augmented
405 * case, but this time with user-defined callbacks.
406 */
407
408void __rb_insert_augmented(struct rb_node *node, struct rb_root *root,
409 void (*augment_rotate)(struct rb_node *old, struct rb_node *new))
410{
411 __rb_insert(node, root, augment_rotate);
412}
413EXPORT_SYMBOL(__rb_insert_augmented);
414
Linus Torvalds1da177e2005-04-16 15:20:36 -0700415/*
416 * This function returns the first node (in sort order) of the tree.
417 */
Artem Bityutskiyf4b477c2009-01-10 11:12:09 +0000418struct rb_node *rb_first(const struct rb_root *root)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700419{
420 struct rb_node *n;
421
422 n = root->rb_node;
423 if (!n)
424 return NULL;
425 while (n->rb_left)
426 n = n->rb_left;
427 return n;
428}
429EXPORT_SYMBOL(rb_first);
430
Artem Bityutskiyf4b477c2009-01-10 11:12:09 +0000431struct rb_node *rb_last(const struct rb_root *root)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700432{
433 struct rb_node *n;
434
435 n = root->rb_node;
436 if (!n)
437 return NULL;
438 while (n->rb_right)
439 n = n->rb_right;
440 return n;
441}
442EXPORT_SYMBOL(rb_last);
443
Artem Bityutskiyf4b477c2009-01-10 11:12:09 +0000444struct rb_node *rb_next(const struct rb_node *node)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700445{
David Woodhouse55a98102006-04-21 13:35:51 +0100446 struct rb_node *parent;
447
Michel Lespinasse4c199a92012-10-08 16:30:32 -0700448 if (RB_EMPTY_NODE(node))
Jens Axboe10fd48f2006-07-11 21:15:52 +0200449 return NULL;
450
Michel Lespinasse7ce6ff92012-10-08 16:31:01 -0700451 /*
452 * If we have a right-hand child, go down and then left as far
453 * as we can.
454 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700455 if (node->rb_right) {
456 node = node->rb_right;
457 while (node->rb_left)
458 node=node->rb_left;
Artem Bityutskiyf4b477c2009-01-10 11:12:09 +0000459 return (struct rb_node *)node;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700460 }
461
Michel Lespinasse7ce6ff92012-10-08 16:31:01 -0700462 /*
463 * No right-hand children. Everything down and left is smaller than us,
464 * so any 'next' node must be in the general direction of our parent.
465 * Go up the tree; any time the ancestor is a right-hand child of its
466 * parent, keep going up. First time it's a left-hand child of its
467 * parent, said parent is our 'next' node.
468 */
David Woodhouse55a98102006-04-21 13:35:51 +0100469 while ((parent = rb_parent(node)) && node == parent->rb_right)
470 node = parent;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700471
David Woodhouse55a98102006-04-21 13:35:51 +0100472 return parent;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700473}
474EXPORT_SYMBOL(rb_next);
475
Artem Bityutskiyf4b477c2009-01-10 11:12:09 +0000476struct rb_node *rb_prev(const struct rb_node *node)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700477{
David Woodhouse55a98102006-04-21 13:35:51 +0100478 struct rb_node *parent;
479
Michel Lespinasse4c199a92012-10-08 16:30:32 -0700480 if (RB_EMPTY_NODE(node))
Jens Axboe10fd48f2006-07-11 21:15:52 +0200481 return NULL;
482
Michel Lespinasse7ce6ff92012-10-08 16:31:01 -0700483 /*
484 * If we have a left-hand child, go down and then right as far
485 * as we can.
486 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700487 if (node->rb_left) {
488 node = node->rb_left;
489 while (node->rb_right)
490 node=node->rb_right;
Artem Bityutskiyf4b477c2009-01-10 11:12:09 +0000491 return (struct rb_node *)node;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700492 }
493
Michel Lespinasse7ce6ff92012-10-08 16:31:01 -0700494 /*
495 * No left-hand children. Go up till we find an ancestor which
496 * is a right-hand child of its parent.
497 */
David Woodhouse55a98102006-04-21 13:35:51 +0100498 while ((parent = rb_parent(node)) && node == parent->rb_left)
499 node = parent;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700500
David Woodhouse55a98102006-04-21 13:35:51 +0100501 return parent;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700502}
503EXPORT_SYMBOL(rb_prev);
504
505void rb_replace_node(struct rb_node *victim, struct rb_node *new,
506 struct rb_root *root)
507{
David Woodhouse55a98102006-04-21 13:35:51 +0100508 struct rb_node *parent = rb_parent(victim);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700509
510 /* Set the surrounding nodes to point to the replacement */
Michel Lespinasse7abc7042012-10-08 16:31:07 -0700511 __rb_change_child(victim, new, parent, root);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700512 if (victim->rb_left)
David Woodhouse55a98102006-04-21 13:35:51 +0100513 rb_set_parent(victim->rb_left, new);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700514 if (victim->rb_right)
David Woodhouse55a98102006-04-21 13:35:51 +0100515 rb_set_parent(victim->rb_right, new);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700516
517 /* Copy the pointers/colour from the victim to the replacement */
518 *new = *victim;
519}
520EXPORT_SYMBOL(rb_replace_node);