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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2011 Red Hat, Inc.
4 *
5 * This file is released under the GPL.
6 */
7
8#include "dm-btree.h"
9#include "dm-btree-internal.h"
10#include "dm-transaction-manager.h"
11
12#include <linux/export.h>
13#include <linux/device-mapper.h>
14
15#define DM_MSG_PREFIX "btree"
16
17/*
18 * Removing an entry from a btree
19 * ==============================
20 *
21 * A very important constraint for our btree is that no node, except the
22 * root, may have fewer than a certain number of entries.
23 * (MIN_ENTRIES <= nr_entries <= MAX_ENTRIES).
24 *
25 * Ensuring this is complicated by the way we want to only ever hold the
26 * locks on 2 nodes concurrently, and only change nodes in a top to bottom
27 * fashion.
28 *
29 * Each node may have a left or right sibling. When decending the spine,
30 * if a node contains only MIN_ENTRIES then we try and increase this to at
31 * least MIN_ENTRIES + 1. We do this in the following ways:
32 *
33 * [A] No siblings => this can only happen if the node is the root, in which
34 * case we copy the childs contents over the root.
35 *
36 * [B] No left sibling
37 * ==> rebalance(node, right sibling)
38 *
39 * [C] No right sibling
40 * ==> rebalance(left sibling, node)
41 *
42 * [D] Both siblings, total_entries(left, node, right) <= DEL_THRESHOLD
43 * ==> delete node adding it's contents to left and right
44 *
45 * [E] Both siblings, total_entries(left, node, right) > DEL_THRESHOLD
46 * ==> rebalance(left, node, right)
47 *
48 * After these operations it's possible that the our original node no
49 * longer contains the desired sub tree. For this reason this rebalancing
50 * is performed on the children of the current node. This also avoids
51 * having a special case for the root.
52 *
53 * Once this rebalancing has occurred we can then step into the child node
54 * for internal nodes. Or delete the entry for leaf nodes.
55 */
56
57/*
58 * Some little utilities for moving node data around.
59 */
60static void node_shift(struct btree_node *n, int shift)
61{
62 uint32_t nr_entries = le32_to_cpu(n->header.nr_entries);
63 uint32_t value_size = le32_to_cpu(n->header.value_size);
64
65 if (shift < 0) {
66 shift = -shift;
67 BUG_ON(shift > nr_entries);
68 BUG_ON((void *) key_ptr(n, shift) >= value_ptr(n, shift));
69 memmove(key_ptr(n, 0),
70 key_ptr(n, shift),
71 (nr_entries - shift) * sizeof(__le64));
72 memmove(value_ptr(n, 0),
73 value_ptr(n, shift),
74 (nr_entries - shift) * value_size);
75 } else {
76 BUG_ON(nr_entries + shift > le32_to_cpu(n->header.max_entries));
77 memmove(key_ptr(n, shift),
78 key_ptr(n, 0),
79 nr_entries * sizeof(__le64));
80 memmove(value_ptr(n, shift),
81 value_ptr(n, 0),
82 nr_entries * value_size);
83 }
84}
85
86static int node_copy(struct btree_node *left, struct btree_node *right, int shift)
87{
88 uint32_t nr_left = le32_to_cpu(left->header.nr_entries);
89 uint32_t value_size = le32_to_cpu(left->header.value_size);
90
91 if (value_size != le32_to_cpu(right->header.value_size)) {
92 DMERR("mismatched value size");
93 return -EILSEQ;
94 }
95
96 if (shift < 0) {
97 shift = -shift;
98
99 if (nr_left + shift > le32_to_cpu(left->header.max_entries)) {
100 DMERR("bad shift");
101 return -EINVAL;
102 }
103
104 memcpy(key_ptr(left, nr_left),
105 key_ptr(right, 0),
106 shift * sizeof(__le64));
107 memcpy(value_ptr(left, nr_left),
108 value_ptr(right, 0),
109 shift * value_size);
110 } else {
111 if (shift > le32_to_cpu(right->header.max_entries)) {
112 DMERR("bad shift");
113 return -EINVAL;
114 }
115
116 memcpy(key_ptr(right, 0),
117 key_ptr(left, nr_left - shift),
118 shift * sizeof(__le64));
119 memcpy(value_ptr(right, 0),
120 value_ptr(left, nr_left - shift),
121 shift * value_size);
122 }
123 return 0;
124}
125
126/*
127 * Delete a specific entry from a leaf node.
128 */
129static void delete_at(struct btree_node *n, unsigned int index)
130{
131 unsigned int nr_entries = le32_to_cpu(n->header.nr_entries);
132 unsigned int nr_to_copy = nr_entries - (index + 1);
133 uint32_t value_size = le32_to_cpu(n->header.value_size);
134
135 BUG_ON(index >= nr_entries);
136
137 if (nr_to_copy) {
138 memmove(key_ptr(n, index),
139 key_ptr(n, index + 1),
140 nr_to_copy * sizeof(__le64));
141
142 memmove(value_ptr(n, index),
143 value_ptr(n, index + 1),
144 nr_to_copy * value_size);
145 }
146
147 n->header.nr_entries = cpu_to_le32(nr_entries - 1);
148}
149
150static unsigned int merge_threshold(struct btree_node *n)
151{
152 return le32_to_cpu(n->header.max_entries) / 3;
153}
154
155struct child {
156 unsigned int index;
157 struct dm_block *block;
158 struct btree_node *n;
159};
160
161static int init_child(struct dm_btree_info *info, struct dm_btree_value_type *vt,
162 struct btree_node *parent,
163 unsigned int index, struct child *result)
164{
165 int r, inc;
166 dm_block_t root;
167
168 result->index = index;
169 root = value64(parent, index);
170
171 r = dm_tm_shadow_block(info->tm, root, &btree_node_validator,
172 &result->block, &inc);
173 if (r)
174 return r;
175
176 result->n = dm_block_data(result->block);
177
178 if (inc)
179 inc_children(info->tm, result->n, vt);
180
181 *((__le64 *) value_ptr(parent, index)) =
182 cpu_to_le64(dm_block_location(result->block));
183
184 return 0;
185}
186
187static void exit_child(struct dm_btree_info *info, struct child *c)
188{
189 dm_tm_unlock(info->tm, c->block);
190}
191
192static int shift(struct btree_node *left, struct btree_node *right, int count)
193{
194 int r;
195 uint32_t nr_left = le32_to_cpu(left->header.nr_entries);
196 uint32_t nr_right = le32_to_cpu(right->header.nr_entries);
197 uint32_t max_entries = le32_to_cpu(left->header.max_entries);
198 uint32_t r_max_entries = le32_to_cpu(right->header.max_entries);
199
200 if (max_entries != r_max_entries) {
201 DMERR("node max_entries mismatch");
202 return -EILSEQ;
203 }
204
205 if (nr_left - count > max_entries) {
206 DMERR("node shift out of bounds");
207 return -EINVAL;
208 }
209
210 if (nr_right + count > max_entries) {
211 DMERR("node shift out of bounds");
212 return -EINVAL;
213 }
214
215 if (!count)
216 return 0;
217
218 if (count > 0) {
219 node_shift(right, count);
220 r = node_copy(left, right, count);
221 if (r)
222 return r;
223 } else {
224 r = node_copy(left, right, count);
225 if (r)
226 return r;
227 node_shift(right, count);
228 }
229
230 left->header.nr_entries = cpu_to_le32(nr_left - count);
231 right->header.nr_entries = cpu_to_le32(nr_right + count);
232
233 return 0;
234}
235
236static int __rebalance2(struct dm_btree_info *info, struct btree_node *parent,
237 struct child *l, struct child *r)
238{
239 int ret;
240 struct btree_node *left = l->n;
241 struct btree_node *right = r->n;
242 uint32_t nr_left = le32_to_cpu(left->header.nr_entries);
243 uint32_t nr_right = le32_to_cpu(right->header.nr_entries);
244 /*
245 * Ensure the number of entries in each child will be greater
246 * than or equal to (max_entries / 3 + 1), so no matter which
247 * child is used for removal, the number will still be not
248 * less than (max_entries / 3).
249 */
250 unsigned int threshold = 2 * (merge_threshold(left) + 1);
251
252 if (nr_left + nr_right < threshold) {
253 /*
254 * Merge
255 */
256 node_copy(left, right, -nr_right);
257 left->header.nr_entries = cpu_to_le32(nr_left + nr_right);
258 delete_at(parent, r->index);
259
260 /*
261 * We need to decrement the right block, but not it's
262 * children, since they're still referenced by left.
263 */
264 dm_tm_dec(info->tm, dm_block_location(r->block));
265 } else {
266 /*
267 * Rebalance.
268 */
269 unsigned int target_left = (nr_left + nr_right) / 2;
270
271 ret = shift(left, right, nr_left - target_left);
272 if (ret)
273 return ret;
274 *key_ptr(parent, r->index) = right->keys[0];
275 }
276 return 0;
277}
278
279static int rebalance2(struct shadow_spine *s, struct dm_btree_info *info,
280 struct dm_btree_value_type *vt, unsigned int left_index)
281{
282 int r;
283 struct btree_node *parent;
284 struct child left, right;
285
286 parent = dm_block_data(shadow_current(s));
287
288 r = init_child(info, vt, parent, left_index, &left);
289 if (r)
290 return r;
291
292 r = init_child(info, vt, parent, left_index + 1, &right);
293 if (r) {
294 exit_child(info, &left);
295 return r;
296 }
297
298 r = __rebalance2(info, parent, &left, &right);
299
300 exit_child(info, &left);
301 exit_child(info, &right);
302
303 return r;
304}
305
306/*
307 * We dump as many entries from center as possible into left, then the rest
308 * in right, then rebalance2. This wastes some cpu, but I want something
309 * simple atm.
310 */
311static int delete_center_node(struct dm_btree_info *info, struct btree_node *parent,
312 struct child *l, struct child *c, struct child *r,
313 struct btree_node *left, struct btree_node *center, struct btree_node *right,
314 uint32_t nr_left, uint32_t nr_center, uint32_t nr_right)
315{
316 uint32_t max_entries = le32_to_cpu(left->header.max_entries);
317 unsigned int shift = min(max_entries - nr_left, nr_center);
318
319 if (nr_left + shift > max_entries) {
320 DMERR("node shift out of bounds");
321 return -EINVAL;
322 }
323
324 node_copy(left, center, -shift);
325 left->header.nr_entries = cpu_to_le32(nr_left + shift);
326
327 if (shift != nr_center) {
328 shift = nr_center - shift;
329
330 if ((nr_right + shift) > max_entries) {
331 DMERR("node shift out of bounds");
332 return -EINVAL;
333 }
334
335 node_shift(right, shift);
336 node_copy(center, right, shift);
337 right->header.nr_entries = cpu_to_le32(nr_right + shift);
338 }
339 *key_ptr(parent, r->index) = right->keys[0];
340
341 delete_at(parent, c->index);
342 r->index--;
343
344 dm_tm_dec(info->tm, dm_block_location(c->block));
345 return __rebalance2(info, parent, l, r);
346}
347
348/*
349 * Redistributes entries among 3 sibling nodes.
350 */
351static int redistribute3(struct dm_btree_info *info, struct btree_node *parent,
352 struct child *l, struct child *c, struct child *r,
353 struct btree_node *left, struct btree_node *center, struct btree_node *right,
354 uint32_t nr_left, uint32_t nr_center, uint32_t nr_right)
355{
356 int s, ret;
357 uint32_t max_entries = le32_to_cpu(left->header.max_entries);
358 unsigned int total = nr_left + nr_center + nr_right;
359 unsigned int target_right = total / 3;
360 unsigned int remainder = (target_right * 3) != total;
361 unsigned int target_left = target_right + remainder;
362
363 BUG_ON(target_left > max_entries);
364 BUG_ON(target_right > max_entries);
365
366 if (nr_left < nr_right) {
367 s = nr_left - target_left;
368
369 if (s < 0 && nr_center < -s) {
370 /* not enough in central node */
371 ret = shift(left, center, -nr_center);
372 if (ret)
373 return ret;
374
375 s += nr_center;
376 ret = shift(left, right, s);
377 if (ret)
378 return ret;
379
380 nr_right += s;
381 } else {
382 ret = shift(left, center, s);
383 if (ret)
384 return ret;
385 }
386
387 ret = shift(center, right, target_right - nr_right);
388 if (ret)
389 return ret;
390 } else {
391 s = target_right - nr_right;
392 if (s > 0 && nr_center < s) {
393 /* not enough in central node */
394 ret = shift(center, right, nr_center);
395 if (ret)
396 return ret;
397 s -= nr_center;
398 ret = shift(left, right, s);
399 if (ret)
400 return ret;
401 nr_left -= s;
402 } else {
403 ret = shift(center, right, s);
404 if (ret)
405 return ret;
406 }
407
408 ret = shift(left, center, nr_left - target_left);
409 if (ret)
410 return ret;
411 }
412
413 *key_ptr(parent, c->index) = center->keys[0];
414 *key_ptr(parent, r->index) = right->keys[0];
415 return 0;
416}
417
418static int __rebalance3(struct dm_btree_info *info, struct btree_node *parent,
419 struct child *l, struct child *c, struct child *r)
420{
421 struct btree_node *left = l->n;
422 struct btree_node *center = c->n;
423 struct btree_node *right = r->n;
424
425 uint32_t nr_left = le32_to_cpu(left->header.nr_entries);
426 uint32_t nr_center = le32_to_cpu(center->header.nr_entries);
427 uint32_t nr_right = le32_to_cpu(right->header.nr_entries);
428
429 unsigned int threshold = merge_threshold(left) * 4 + 1;
430
431 if ((left->header.max_entries != center->header.max_entries) ||
432 (center->header.max_entries != right->header.max_entries)) {
433 DMERR("bad btree metadata, max_entries differ");
434 return -EILSEQ;
435 }
436
437 if ((nr_left + nr_center + nr_right) < threshold) {
438 return delete_center_node(info, parent, l, c, r, left, center, right,
439 nr_left, nr_center, nr_right);
440 }
441
442 return redistribute3(info, parent, l, c, r, left, center, right,
443 nr_left, nr_center, nr_right);
444}
445
446static int rebalance3(struct shadow_spine *s, struct dm_btree_info *info,
447 struct dm_btree_value_type *vt, unsigned int left_index)
448{
449 int r;
450 struct btree_node *parent = dm_block_data(shadow_current(s));
451 struct child left, center, right;
452
453 /*
454 * FIXME: fill out an array?
455 */
456 r = init_child(info, vt, parent, left_index, &left);
457 if (r)
458 return r;
459
460 r = init_child(info, vt, parent, left_index + 1, ¢er);
461 if (r) {
462 exit_child(info, &left);
463 return r;
464 }
465
466 r = init_child(info, vt, parent, left_index + 2, &right);
467 if (r) {
468 exit_child(info, &left);
469 exit_child(info, ¢er);
470 return r;
471 }
472
473 r = __rebalance3(info, parent, &left, ¢er, &right);
474
475 exit_child(info, &left);
476 exit_child(info, ¢er);
477 exit_child(info, &right);
478
479 return r;
480}
481
482static int rebalance_children(struct shadow_spine *s,
483 struct dm_btree_info *info,
484 struct dm_btree_value_type *vt, uint64_t key)
485{
486 int i, r, has_left_sibling, has_right_sibling;
487 struct btree_node *n;
488
489 n = dm_block_data(shadow_current(s));
490
491 if (le32_to_cpu(n->header.nr_entries) == 1) {
492 struct dm_block *child;
493 dm_block_t b = value64(n, 0);
494
495 r = dm_tm_read_lock(info->tm, b, &btree_node_validator, &child);
496 if (r)
497 return r;
498
499 memcpy(n, dm_block_data(child),
500 dm_bm_block_size(dm_tm_get_bm(info->tm)));
501
502 dm_tm_dec(info->tm, dm_block_location(child));
503 dm_tm_unlock(info->tm, child);
504 return 0;
505 }
506
507 i = lower_bound(n, key);
508 if (i < 0)
509 return -ENODATA;
510
511 has_left_sibling = i > 0;
512 has_right_sibling = i < (le32_to_cpu(n->header.nr_entries) - 1);
513
514 if (!has_left_sibling)
515 r = rebalance2(s, info, vt, i);
516
517 else if (!has_right_sibling)
518 r = rebalance2(s, info, vt, i - 1);
519
520 else
521 r = rebalance3(s, info, vt, i - 1);
522
523 return r;
524}
525
526static int do_leaf(struct btree_node *n, uint64_t key, unsigned int *index)
527{
528 int i = lower_bound(n, key);
529
530 if ((i < 0) ||
531 (i >= le32_to_cpu(n->header.nr_entries)) ||
532 (le64_to_cpu(n->keys[i]) != key))
533 return -ENODATA;
534
535 *index = i;
536
537 return 0;
538}
539
540/*
541 * Prepares for removal from one level of the hierarchy. The caller must
542 * call delete_at() to remove the entry at index.
543 */
544static int remove_raw(struct shadow_spine *s, struct dm_btree_info *info,
545 struct dm_btree_value_type *vt, dm_block_t root,
546 uint64_t key, unsigned int *index)
547{
548 int i = *index, r;
549 struct btree_node *n;
550
551 for (;;) {
552 r = shadow_step(s, root, vt);
553 if (r < 0)
554 break;
555
556 /*
557 * We have to patch up the parent node, ugly, but I don't
558 * see a way to do this automatically as part of the spine
559 * op.
560 */
561 if (shadow_has_parent(s)) {
562 __le64 location = cpu_to_le64(dm_block_location(shadow_current(s)));
563
564 memcpy(value_ptr(dm_block_data(shadow_parent(s)), i),
565 &location, sizeof(__le64));
566 }
567
568 n = dm_block_data(shadow_current(s));
569
570 if (le32_to_cpu(n->header.flags) & LEAF_NODE)
571 return do_leaf(n, key, index);
572
573 r = rebalance_children(s, info, vt, key);
574 if (r)
575 break;
576
577 n = dm_block_data(shadow_current(s));
578 if (le32_to_cpu(n->header.flags) & LEAF_NODE)
579 return do_leaf(n, key, index);
580
581 i = lower_bound(n, key);
582
583 /*
584 * We know the key is present, or else
585 * rebalance_children would have returned
586 * -ENODATA
587 */
588 root = value64(n, i);
589 }
590
591 return r;
592}
593
594int dm_btree_remove(struct dm_btree_info *info, dm_block_t root,
595 uint64_t *keys, dm_block_t *new_root)
596{
597 unsigned int level, last_level = info->levels - 1;
598 int index = 0, r = 0;
599 struct shadow_spine spine;
600 struct btree_node *n;
601 struct dm_btree_value_type le64_vt;
602
603 init_le64_type(info->tm, &le64_vt);
604 init_shadow_spine(&spine, info);
605 for (level = 0; level < info->levels; level++) {
606 r = remove_raw(&spine, info,
607 (level == last_level ?
608 &info->value_type : &le64_vt),
609 root, keys[level], (unsigned int *)&index);
610 if (r < 0)
611 break;
612
613 n = dm_block_data(shadow_current(&spine));
614 if (level != last_level) {
615 root = value64(n, index);
616 continue;
617 }
618
619 BUG_ON(index < 0 || index >= le32_to_cpu(n->header.nr_entries));
620
621 if (info->value_type.dec)
622 info->value_type.dec(info->value_type.context,
623 value_ptr(n, index), 1);
624
625 delete_at(n, index);
626 }
627
628 if (!r)
629 *new_root = shadow_root(&spine);
630 exit_shadow_spine(&spine);
631
632 return r;
633}
634EXPORT_SYMBOL_GPL(dm_btree_remove);
635
636/*----------------------------------------------------------------*/
637
638static int remove_nearest(struct shadow_spine *s, struct dm_btree_info *info,
639 struct dm_btree_value_type *vt, dm_block_t root,
640 uint64_t key, int *index)
641{
642 int i = *index, r;
643 struct btree_node *n;
644
645 for (;;) {
646 r = shadow_step(s, root, vt);
647 if (r < 0)
648 break;
649
650 /*
651 * We have to patch up the parent node, ugly, but I don't
652 * see a way to do this automatically as part of the spine
653 * op.
654 */
655 if (shadow_has_parent(s)) {
656 __le64 location = cpu_to_le64(dm_block_location(shadow_current(s)));
657
658 memcpy(value_ptr(dm_block_data(shadow_parent(s)), i),
659 &location, sizeof(__le64));
660 }
661
662 n = dm_block_data(shadow_current(s));
663
664 if (le32_to_cpu(n->header.flags) & LEAF_NODE) {
665 *index = lower_bound(n, key);
666 return 0;
667 }
668
669 r = rebalance_children(s, info, vt, key);
670 if (r)
671 break;
672
673 n = dm_block_data(shadow_current(s));
674 if (le32_to_cpu(n->header.flags) & LEAF_NODE) {
675 *index = lower_bound(n, key);
676 return 0;
677 }
678
679 i = lower_bound(n, key);
680
681 /*
682 * We know the key is present, or else
683 * rebalance_children would have returned
684 * -ENODATA
685 */
686 root = value64(n, i);
687 }
688
689 return r;
690}
691
692static int remove_one(struct dm_btree_info *info, dm_block_t root,
693 uint64_t *keys, uint64_t end_key,
694 dm_block_t *new_root, unsigned int *nr_removed)
695{
696 unsigned int level, last_level = info->levels - 1;
697 int index = 0, r = 0;
698 struct shadow_spine spine;
699 struct btree_node *n;
700 struct dm_btree_value_type le64_vt;
701 uint64_t k;
702
703 init_le64_type(info->tm, &le64_vt);
704 init_shadow_spine(&spine, info);
705 for (level = 0; level < last_level; level++) {
706 r = remove_raw(&spine, info, &le64_vt,
707 root, keys[level], (unsigned int *) &index);
708 if (r < 0)
709 goto out;
710
711 n = dm_block_data(shadow_current(&spine));
712 root = value64(n, index);
713 }
714
715 r = remove_nearest(&spine, info, &info->value_type,
716 root, keys[last_level], &index);
717 if (r < 0)
718 goto out;
719
720 n = dm_block_data(shadow_current(&spine));
721
722 if (index < 0)
723 index = 0;
724
725 if (index >= le32_to_cpu(n->header.nr_entries)) {
726 r = -ENODATA;
727 goto out;
728 }
729
730 k = le64_to_cpu(n->keys[index]);
731 if (k >= keys[last_level] && k < end_key) {
732 if (info->value_type.dec)
733 info->value_type.dec(info->value_type.context,
734 value_ptr(n, index), 1);
735
736 delete_at(n, index);
737 keys[last_level] = k + 1ull;
738
739 } else
740 r = -ENODATA;
741
742out:
743 *new_root = shadow_root(&spine);
744 exit_shadow_spine(&spine);
745
746 return r;
747}
748
749int dm_btree_remove_leaves(struct dm_btree_info *info, dm_block_t root,
750 uint64_t *first_key, uint64_t end_key,
751 dm_block_t *new_root, unsigned int *nr_removed)
752{
753 int r;
754
755 *nr_removed = 0;
756 do {
757 r = remove_one(info, root, first_key, end_key, &root, nr_removed);
758 if (!r)
759 (*nr_removed)++;
760 } while (!r);
761
762 *new_root = root;
763 return r == -ENODATA ? 0 : r;
764}
765EXPORT_SYMBOL_GPL(dm_btree_remove_leaves);
1/*
2 * Copyright (C) 2011 Red Hat, Inc.
3 *
4 * This file is released under the GPL.
5 */
6
7#include "dm-btree.h"
8#include "dm-btree-internal.h"
9#include "dm-transaction-manager.h"
10
11#include <linux/export.h>
12
13/*
14 * Removing an entry from a btree
15 * ==============================
16 *
17 * A very important constraint for our btree is that no node, except the
18 * root, may have fewer than a certain number of entries.
19 * (MIN_ENTRIES <= nr_entries <= MAX_ENTRIES).
20 *
21 * Ensuring this is complicated by the way we want to only ever hold the
22 * locks on 2 nodes concurrently, and only change nodes in a top to bottom
23 * fashion.
24 *
25 * Each node may have a left or right sibling. When decending the spine,
26 * if a node contains only MIN_ENTRIES then we try and increase this to at
27 * least MIN_ENTRIES + 1. We do this in the following ways:
28 *
29 * [A] No siblings => this can only happen if the node is the root, in which
30 * case we copy the childs contents over the root.
31 *
32 * [B] No left sibling
33 * ==> rebalance(node, right sibling)
34 *
35 * [C] No right sibling
36 * ==> rebalance(left sibling, node)
37 *
38 * [D] Both siblings, total_entries(left, node, right) <= DEL_THRESHOLD
39 * ==> delete node adding it's contents to left and right
40 *
41 * [E] Both siblings, total_entries(left, node, right) > DEL_THRESHOLD
42 * ==> rebalance(left, node, right)
43 *
44 * After these operations it's possible that the our original node no
45 * longer contains the desired sub tree. For this reason this rebalancing
46 * is performed on the children of the current node. This also avoids
47 * having a special case for the root.
48 *
49 * Once this rebalancing has occurred we can then step into the child node
50 * for internal nodes. Or delete the entry for leaf nodes.
51 */
52
53/*
54 * Some little utilities for moving node data around.
55 */
56static void node_shift(struct btree_node *n, int shift)
57{
58 uint32_t nr_entries = le32_to_cpu(n->header.nr_entries);
59 uint32_t value_size = le32_to_cpu(n->header.value_size);
60
61 if (shift < 0) {
62 shift = -shift;
63 BUG_ON(shift > nr_entries);
64 BUG_ON((void *) key_ptr(n, shift) >= value_ptr(n, shift));
65 memmove(key_ptr(n, 0),
66 key_ptr(n, shift),
67 (nr_entries - shift) * sizeof(__le64));
68 memmove(value_ptr(n, 0),
69 value_ptr(n, shift),
70 (nr_entries - shift) * value_size);
71 } else {
72 BUG_ON(nr_entries + shift > le32_to_cpu(n->header.max_entries));
73 memmove(key_ptr(n, shift),
74 key_ptr(n, 0),
75 nr_entries * sizeof(__le64));
76 memmove(value_ptr(n, shift),
77 value_ptr(n, 0),
78 nr_entries * value_size);
79 }
80}
81
82static void node_copy(struct btree_node *left, struct btree_node *right, int shift)
83{
84 uint32_t nr_left = le32_to_cpu(left->header.nr_entries);
85 uint32_t value_size = le32_to_cpu(left->header.value_size);
86 BUG_ON(value_size != le32_to_cpu(right->header.value_size));
87
88 if (shift < 0) {
89 shift = -shift;
90 BUG_ON(nr_left + shift > le32_to_cpu(left->header.max_entries));
91 memcpy(key_ptr(left, nr_left),
92 key_ptr(right, 0),
93 shift * sizeof(__le64));
94 memcpy(value_ptr(left, nr_left),
95 value_ptr(right, 0),
96 shift * value_size);
97 } else {
98 BUG_ON(shift > le32_to_cpu(right->header.max_entries));
99 memcpy(key_ptr(right, 0),
100 key_ptr(left, nr_left - shift),
101 shift * sizeof(__le64));
102 memcpy(value_ptr(right, 0),
103 value_ptr(left, nr_left - shift),
104 shift * value_size);
105 }
106}
107
108/*
109 * Delete a specific entry from a leaf node.
110 */
111static void delete_at(struct btree_node *n, unsigned index)
112{
113 unsigned nr_entries = le32_to_cpu(n->header.nr_entries);
114 unsigned nr_to_copy = nr_entries - (index + 1);
115 uint32_t value_size = le32_to_cpu(n->header.value_size);
116 BUG_ON(index >= nr_entries);
117
118 if (nr_to_copy) {
119 memmove(key_ptr(n, index),
120 key_ptr(n, index + 1),
121 nr_to_copy * sizeof(__le64));
122
123 memmove(value_ptr(n, index),
124 value_ptr(n, index + 1),
125 nr_to_copy * value_size);
126 }
127
128 n->header.nr_entries = cpu_to_le32(nr_entries - 1);
129}
130
131static unsigned merge_threshold(struct btree_node *n)
132{
133 return le32_to_cpu(n->header.max_entries) / 3;
134}
135
136struct child {
137 unsigned index;
138 struct dm_block *block;
139 struct btree_node *n;
140};
141
142static int init_child(struct dm_btree_info *info, struct dm_btree_value_type *vt,
143 struct btree_node *parent,
144 unsigned index, struct child *result)
145{
146 int r, inc;
147 dm_block_t root;
148
149 result->index = index;
150 root = value64(parent, index);
151
152 r = dm_tm_shadow_block(info->tm, root, &btree_node_validator,
153 &result->block, &inc);
154 if (r)
155 return r;
156
157 result->n = dm_block_data(result->block);
158
159 if (inc)
160 inc_children(info->tm, result->n, vt);
161
162 *((__le64 *) value_ptr(parent, index)) =
163 cpu_to_le64(dm_block_location(result->block));
164
165 return 0;
166}
167
168static void exit_child(struct dm_btree_info *info, struct child *c)
169{
170 dm_tm_unlock(info->tm, c->block);
171}
172
173static void shift(struct btree_node *left, struct btree_node *right, int count)
174{
175 uint32_t nr_left = le32_to_cpu(left->header.nr_entries);
176 uint32_t nr_right = le32_to_cpu(right->header.nr_entries);
177 uint32_t max_entries = le32_to_cpu(left->header.max_entries);
178 uint32_t r_max_entries = le32_to_cpu(right->header.max_entries);
179
180 BUG_ON(max_entries != r_max_entries);
181 BUG_ON(nr_left - count > max_entries);
182 BUG_ON(nr_right + count > max_entries);
183
184 if (!count)
185 return;
186
187 if (count > 0) {
188 node_shift(right, count);
189 node_copy(left, right, count);
190 } else {
191 node_copy(left, right, count);
192 node_shift(right, count);
193 }
194
195 left->header.nr_entries = cpu_to_le32(nr_left - count);
196 right->header.nr_entries = cpu_to_le32(nr_right + count);
197}
198
199static void __rebalance2(struct dm_btree_info *info, struct btree_node *parent,
200 struct child *l, struct child *r)
201{
202 struct btree_node *left = l->n;
203 struct btree_node *right = r->n;
204 uint32_t nr_left = le32_to_cpu(left->header.nr_entries);
205 uint32_t nr_right = le32_to_cpu(right->header.nr_entries);
206 /*
207 * Ensure the number of entries in each child will be greater
208 * than or equal to (max_entries / 3 + 1), so no matter which
209 * child is used for removal, the number will still be not
210 * less than (max_entries / 3).
211 */
212 unsigned int threshold = 2 * (merge_threshold(left) + 1);
213
214 if (nr_left + nr_right < threshold) {
215 /*
216 * Merge
217 */
218 node_copy(left, right, -nr_right);
219 left->header.nr_entries = cpu_to_le32(nr_left + nr_right);
220 delete_at(parent, r->index);
221
222 /*
223 * We need to decrement the right block, but not it's
224 * children, since they're still referenced by left.
225 */
226 dm_tm_dec(info->tm, dm_block_location(r->block));
227 } else {
228 /*
229 * Rebalance.
230 */
231 unsigned target_left = (nr_left + nr_right) / 2;
232 shift(left, right, nr_left - target_left);
233 *key_ptr(parent, r->index) = right->keys[0];
234 }
235}
236
237static int rebalance2(struct shadow_spine *s, struct dm_btree_info *info,
238 struct dm_btree_value_type *vt, unsigned left_index)
239{
240 int r;
241 struct btree_node *parent;
242 struct child left, right;
243
244 parent = dm_block_data(shadow_current(s));
245
246 r = init_child(info, vt, parent, left_index, &left);
247 if (r)
248 return r;
249
250 r = init_child(info, vt, parent, left_index + 1, &right);
251 if (r) {
252 exit_child(info, &left);
253 return r;
254 }
255
256 __rebalance2(info, parent, &left, &right);
257
258 exit_child(info, &left);
259 exit_child(info, &right);
260
261 return 0;
262}
263
264/*
265 * We dump as many entries from center as possible into left, then the rest
266 * in right, then rebalance2. This wastes some cpu, but I want something
267 * simple atm.
268 */
269static void delete_center_node(struct dm_btree_info *info, struct btree_node *parent,
270 struct child *l, struct child *c, struct child *r,
271 struct btree_node *left, struct btree_node *center, struct btree_node *right,
272 uint32_t nr_left, uint32_t nr_center, uint32_t nr_right)
273{
274 uint32_t max_entries = le32_to_cpu(left->header.max_entries);
275 unsigned shift = min(max_entries - nr_left, nr_center);
276
277 BUG_ON(nr_left + shift > max_entries);
278 node_copy(left, center, -shift);
279 left->header.nr_entries = cpu_to_le32(nr_left + shift);
280
281 if (shift != nr_center) {
282 shift = nr_center - shift;
283 BUG_ON((nr_right + shift) > max_entries);
284 node_shift(right, shift);
285 node_copy(center, right, shift);
286 right->header.nr_entries = cpu_to_le32(nr_right + shift);
287 }
288 *key_ptr(parent, r->index) = right->keys[0];
289
290 delete_at(parent, c->index);
291 r->index--;
292
293 dm_tm_dec(info->tm, dm_block_location(c->block));
294 __rebalance2(info, parent, l, r);
295}
296
297/*
298 * Redistributes entries among 3 sibling nodes.
299 */
300static void redistribute3(struct dm_btree_info *info, struct btree_node *parent,
301 struct child *l, struct child *c, struct child *r,
302 struct btree_node *left, struct btree_node *center, struct btree_node *right,
303 uint32_t nr_left, uint32_t nr_center, uint32_t nr_right)
304{
305 int s;
306 uint32_t max_entries = le32_to_cpu(left->header.max_entries);
307 unsigned total = nr_left + nr_center + nr_right;
308 unsigned target_right = total / 3;
309 unsigned remainder = (target_right * 3) != total;
310 unsigned target_left = target_right + remainder;
311
312 BUG_ON(target_left > max_entries);
313 BUG_ON(target_right > max_entries);
314
315 if (nr_left < nr_right) {
316 s = nr_left - target_left;
317
318 if (s < 0 && nr_center < -s) {
319 /* not enough in central node */
320 shift(left, center, -nr_center);
321 s += nr_center;
322 shift(left, right, s);
323 nr_right += s;
324 } else
325 shift(left, center, s);
326
327 shift(center, right, target_right - nr_right);
328
329 } else {
330 s = target_right - nr_right;
331 if (s > 0 && nr_center < s) {
332 /* not enough in central node */
333 shift(center, right, nr_center);
334 s -= nr_center;
335 shift(left, right, s);
336 nr_left -= s;
337 } else
338 shift(center, right, s);
339
340 shift(left, center, nr_left - target_left);
341 }
342
343 *key_ptr(parent, c->index) = center->keys[0];
344 *key_ptr(parent, r->index) = right->keys[0];
345}
346
347static void __rebalance3(struct dm_btree_info *info, struct btree_node *parent,
348 struct child *l, struct child *c, struct child *r)
349{
350 struct btree_node *left = l->n;
351 struct btree_node *center = c->n;
352 struct btree_node *right = r->n;
353
354 uint32_t nr_left = le32_to_cpu(left->header.nr_entries);
355 uint32_t nr_center = le32_to_cpu(center->header.nr_entries);
356 uint32_t nr_right = le32_to_cpu(right->header.nr_entries);
357
358 unsigned threshold = merge_threshold(left) * 4 + 1;
359
360 BUG_ON(left->header.max_entries != center->header.max_entries);
361 BUG_ON(center->header.max_entries != right->header.max_entries);
362
363 if ((nr_left + nr_center + nr_right) < threshold)
364 delete_center_node(info, parent, l, c, r, left, center, right,
365 nr_left, nr_center, nr_right);
366 else
367 redistribute3(info, parent, l, c, r, left, center, right,
368 nr_left, nr_center, nr_right);
369}
370
371static int rebalance3(struct shadow_spine *s, struct dm_btree_info *info,
372 struct dm_btree_value_type *vt, unsigned left_index)
373{
374 int r;
375 struct btree_node *parent = dm_block_data(shadow_current(s));
376 struct child left, center, right;
377
378 /*
379 * FIXME: fill out an array?
380 */
381 r = init_child(info, vt, parent, left_index, &left);
382 if (r)
383 return r;
384
385 r = init_child(info, vt, parent, left_index + 1, ¢er);
386 if (r) {
387 exit_child(info, &left);
388 return r;
389 }
390
391 r = init_child(info, vt, parent, left_index + 2, &right);
392 if (r) {
393 exit_child(info, &left);
394 exit_child(info, ¢er);
395 return r;
396 }
397
398 __rebalance3(info, parent, &left, ¢er, &right);
399
400 exit_child(info, &left);
401 exit_child(info, ¢er);
402 exit_child(info, &right);
403
404 return 0;
405}
406
407static int rebalance_children(struct shadow_spine *s,
408 struct dm_btree_info *info,
409 struct dm_btree_value_type *vt, uint64_t key)
410{
411 int i, r, has_left_sibling, has_right_sibling;
412 struct btree_node *n;
413
414 n = dm_block_data(shadow_current(s));
415
416 if (le32_to_cpu(n->header.nr_entries) == 1) {
417 struct dm_block *child;
418 dm_block_t b = value64(n, 0);
419
420 r = dm_tm_read_lock(info->tm, b, &btree_node_validator, &child);
421 if (r)
422 return r;
423
424 memcpy(n, dm_block_data(child),
425 dm_bm_block_size(dm_tm_get_bm(info->tm)));
426 dm_tm_unlock(info->tm, child);
427
428 dm_tm_dec(info->tm, dm_block_location(child));
429 return 0;
430 }
431
432 i = lower_bound(n, key);
433 if (i < 0)
434 return -ENODATA;
435
436 has_left_sibling = i > 0;
437 has_right_sibling = i < (le32_to_cpu(n->header.nr_entries) - 1);
438
439 if (!has_left_sibling)
440 r = rebalance2(s, info, vt, i);
441
442 else if (!has_right_sibling)
443 r = rebalance2(s, info, vt, i - 1);
444
445 else
446 r = rebalance3(s, info, vt, i - 1);
447
448 return r;
449}
450
451static int do_leaf(struct btree_node *n, uint64_t key, unsigned *index)
452{
453 int i = lower_bound(n, key);
454
455 if ((i < 0) ||
456 (i >= le32_to_cpu(n->header.nr_entries)) ||
457 (le64_to_cpu(n->keys[i]) != key))
458 return -ENODATA;
459
460 *index = i;
461
462 return 0;
463}
464
465/*
466 * Prepares for removal from one level of the hierarchy. The caller must
467 * call delete_at() to remove the entry at index.
468 */
469static int remove_raw(struct shadow_spine *s, struct dm_btree_info *info,
470 struct dm_btree_value_type *vt, dm_block_t root,
471 uint64_t key, unsigned *index)
472{
473 int i = *index, r;
474 struct btree_node *n;
475
476 for (;;) {
477 r = shadow_step(s, root, vt);
478 if (r < 0)
479 break;
480
481 /*
482 * We have to patch up the parent node, ugly, but I don't
483 * see a way to do this automatically as part of the spine
484 * op.
485 */
486 if (shadow_has_parent(s)) {
487 __le64 location = cpu_to_le64(dm_block_location(shadow_current(s)));
488 memcpy(value_ptr(dm_block_data(shadow_parent(s)), i),
489 &location, sizeof(__le64));
490 }
491
492 n = dm_block_data(shadow_current(s));
493
494 if (le32_to_cpu(n->header.flags) & LEAF_NODE)
495 return do_leaf(n, key, index);
496
497 r = rebalance_children(s, info, vt, key);
498 if (r)
499 break;
500
501 n = dm_block_data(shadow_current(s));
502 if (le32_to_cpu(n->header.flags) & LEAF_NODE)
503 return do_leaf(n, key, index);
504
505 i = lower_bound(n, key);
506
507 /*
508 * We know the key is present, or else
509 * rebalance_children would have returned
510 * -ENODATA
511 */
512 root = value64(n, i);
513 }
514
515 return r;
516}
517
518int dm_btree_remove(struct dm_btree_info *info, dm_block_t root,
519 uint64_t *keys, dm_block_t *new_root)
520{
521 unsigned level, last_level = info->levels - 1;
522 int index = 0, r = 0;
523 struct shadow_spine spine;
524 struct btree_node *n;
525 struct dm_btree_value_type le64_vt;
526
527 init_le64_type(info->tm, &le64_vt);
528 init_shadow_spine(&spine, info);
529 for (level = 0; level < info->levels; level++) {
530 r = remove_raw(&spine, info,
531 (level == last_level ?
532 &info->value_type : &le64_vt),
533 root, keys[level], (unsigned *)&index);
534 if (r < 0)
535 break;
536
537 n = dm_block_data(shadow_current(&spine));
538 if (level != last_level) {
539 root = value64(n, index);
540 continue;
541 }
542
543 BUG_ON(index < 0 || index >= le32_to_cpu(n->header.nr_entries));
544
545 if (info->value_type.dec)
546 info->value_type.dec(info->value_type.context,
547 value_ptr(n, index));
548
549 delete_at(n, index);
550 }
551
552 *new_root = shadow_root(&spine);
553 exit_shadow_spine(&spine);
554
555 return r;
556}
557EXPORT_SYMBOL_GPL(dm_btree_remove);
558
559/*----------------------------------------------------------------*/
560
561static int remove_nearest(struct shadow_spine *s, struct dm_btree_info *info,
562 struct dm_btree_value_type *vt, dm_block_t root,
563 uint64_t key, int *index)
564{
565 int i = *index, r;
566 struct btree_node *n;
567
568 for (;;) {
569 r = shadow_step(s, root, vt);
570 if (r < 0)
571 break;
572
573 /*
574 * We have to patch up the parent node, ugly, but I don't
575 * see a way to do this automatically as part of the spine
576 * op.
577 */
578 if (shadow_has_parent(s)) {
579 __le64 location = cpu_to_le64(dm_block_location(shadow_current(s)));
580 memcpy(value_ptr(dm_block_data(shadow_parent(s)), i),
581 &location, sizeof(__le64));
582 }
583
584 n = dm_block_data(shadow_current(s));
585
586 if (le32_to_cpu(n->header.flags) & LEAF_NODE) {
587 *index = lower_bound(n, key);
588 return 0;
589 }
590
591 r = rebalance_children(s, info, vt, key);
592 if (r)
593 break;
594
595 n = dm_block_data(shadow_current(s));
596 if (le32_to_cpu(n->header.flags) & LEAF_NODE) {
597 *index = lower_bound(n, key);
598 return 0;
599 }
600
601 i = lower_bound(n, key);
602
603 /*
604 * We know the key is present, or else
605 * rebalance_children would have returned
606 * -ENODATA
607 */
608 root = value64(n, i);
609 }
610
611 return r;
612}
613
614static int remove_one(struct dm_btree_info *info, dm_block_t root,
615 uint64_t *keys, uint64_t end_key,
616 dm_block_t *new_root, unsigned *nr_removed)
617{
618 unsigned level, last_level = info->levels - 1;
619 int index = 0, r = 0;
620 struct shadow_spine spine;
621 struct btree_node *n;
622 struct dm_btree_value_type le64_vt;
623 uint64_t k;
624
625 init_le64_type(info->tm, &le64_vt);
626 init_shadow_spine(&spine, info);
627 for (level = 0; level < last_level; level++) {
628 r = remove_raw(&spine, info, &le64_vt,
629 root, keys[level], (unsigned *) &index);
630 if (r < 0)
631 goto out;
632
633 n = dm_block_data(shadow_current(&spine));
634 root = value64(n, index);
635 }
636
637 r = remove_nearest(&spine, info, &info->value_type,
638 root, keys[last_level], &index);
639 if (r < 0)
640 goto out;
641
642 n = dm_block_data(shadow_current(&spine));
643
644 if (index < 0)
645 index = 0;
646
647 if (index >= le32_to_cpu(n->header.nr_entries)) {
648 r = -ENODATA;
649 goto out;
650 }
651
652 k = le64_to_cpu(n->keys[index]);
653 if (k >= keys[last_level] && k < end_key) {
654 if (info->value_type.dec)
655 info->value_type.dec(info->value_type.context,
656 value_ptr(n, index));
657
658 delete_at(n, index);
659 keys[last_level] = k + 1ull;
660
661 } else
662 r = -ENODATA;
663
664out:
665 *new_root = shadow_root(&spine);
666 exit_shadow_spine(&spine);
667
668 return r;
669}
670
671int dm_btree_remove_leaves(struct dm_btree_info *info, dm_block_t root,
672 uint64_t *first_key, uint64_t end_key,
673 dm_block_t *new_root, unsigned *nr_removed)
674{
675 int r;
676
677 *nr_removed = 0;
678 do {
679 r = remove_one(info, root, first_key, end_key, &root, nr_removed);
680 if (!r)
681 (*nr_removed)++;
682 } while (!r);
683
684 *new_root = root;
685 return r == -ENODATA ? 0 : r;
686}
687EXPORT_SYMBOL_GPL(dm_btree_remove_leaves);