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1// SPDX-License-Identifier: GPL-2.0
2
3#include "messages.h"
4#include "tree-mod-log.h"
5#include "disk-io.h"
6#include "fs.h"
7#include "accessors.h"
8#include "tree-checker.h"
9
10struct tree_mod_root {
11 u64 logical;
12 u8 level;
13};
14
15struct tree_mod_elem {
16 struct rb_node node;
17 u64 logical;
18 u64 seq;
19 enum btrfs_mod_log_op op;
20
21 /*
22 * This is used for BTRFS_MOD_LOG_KEY_* and BTRFS_MOD_LOG_MOVE_KEYS
23 * operations.
24 */
25 int slot;
26
27 /* This is used for BTRFS_MOD_LOG_KEY* and BTRFS_MOD_LOG_ROOT_REPLACE. */
28 u64 generation;
29
30 /* Those are used for op == BTRFS_MOD_LOG_KEY_{REPLACE,REMOVE}. */
31 struct btrfs_disk_key key;
32 u64 blockptr;
33
34 /* This is used for op == BTRFS_MOD_LOG_MOVE_KEYS. */
35 struct {
36 int dst_slot;
37 int nr_items;
38 } move;
39
40 /* This is used for op == BTRFS_MOD_LOG_ROOT_REPLACE. */
41 struct tree_mod_root old_root;
42};
43
44/*
45 * Pull a new tree mod seq number for our operation.
46 */
47static u64 btrfs_inc_tree_mod_seq(struct btrfs_fs_info *fs_info)
48{
49 return atomic64_inc_return(&fs_info->tree_mod_seq);
50}
51
52/*
53 * This adds a new blocker to the tree mod log's blocker list if the @elem
54 * passed does not already have a sequence number set. So when a caller expects
55 * to record tree modifications, it should ensure to set elem->seq to zero
56 * before calling btrfs_get_tree_mod_seq.
57 * Returns a fresh, unused tree log modification sequence number, even if no new
58 * blocker was added.
59 */
60u64 btrfs_get_tree_mod_seq(struct btrfs_fs_info *fs_info,
61 struct btrfs_seq_list *elem)
62{
63 write_lock(&fs_info->tree_mod_log_lock);
64 if (!elem->seq) {
65 elem->seq = btrfs_inc_tree_mod_seq(fs_info);
66 list_add_tail(&elem->list, &fs_info->tree_mod_seq_list);
67 set_bit(BTRFS_FS_TREE_MOD_LOG_USERS, &fs_info->flags);
68 }
69 write_unlock(&fs_info->tree_mod_log_lock);
70
71 return elem->seq;
72}
73
74void btrfs_put_tree_mod_seq(struct btrfs_fs_info *fs_info,
75 struct btrfs_seq_list *elem)
76{
77 struct rb_root *tm_root;
78 struct rb_node *node;
79 struct rb_node *next;
80 struct tree_mod_elem *tm;
81 u64 min_seq = BTRFS_SEQ_LAST;
82 u64 seq_putting = elem->seq;
83
84 if (!seq_putting)
85 return;
86
87 write_lock(&fs_info->tree_mod_log_lock);
88 list_del(&elem->list);
89 elem->seq = 0;
90
91 if (list_empty(&fs_info->tree_mod_seq_list)) {
92 clear_bit(BTRFS_FS_TREE_MOD_LOG_USERS, &fs_info->flags);
93 } else {
94 struct btrfs_seq_list *first;
95
96 first = list_first_entry(&fs_info->tree_mod_seq_list,
97 struct btrfs_seq_list, list);
98 if (seq_putting > first->seq) {
99 /*
100 * Blocker with lower sequence number exists, we cannot
101 * remove anything from the log.
102 */
103 write_unlock(&fs_info->tree_mod_log_lock);
104 return;
105 }
106 min_seq = first->seq;
107 }
108
109 /*
110 * Anything that's lower than the lowest existing (read: blocked)
111 * sequence number can be removed from the tree.
112 */
113 tm_root = &fs_info->tree_mod_log;
114 for (node = rb_first(tm_root); node; node = next) {
115 next = rb_next(node);
116 tm = rb_entry(node, struct tree_mod_elem, node);
117 if (tm->seq >= min_seq)
118 continue;
119 rb_erase(node, tm_root);
120 kfree(tm);
121 }
122 write_unlock(&fs_info->tree_mod_log_lock);
123}
124
125/*
126 * Key order of the log:
127 * node/leaf start address -> sequence
128 *
129 * The 'start address' is the logical address of the *new* root node for root
130 * replace operations, or the logical address of the affected block for all
131 * other operations.
132 */
133static noinline int tree_mod_log_insert(struct btrfs_fs_info *fs_info,
134 struct tree_mod_elem *tm)
135{
136 struct rb_root *tm_root;
137 struct rb_node **new;
138 struct rb_node *parent = NULL;
139 struct tree_mod_elem *cur;
140
141 lockdep_assert_held_write(&fs_info->tree_mod_log_lock);
142
143 tm->seq = btrfs_inc_tree_mod_seq(fs_info);
144
145 tm_root = &fs_info->tree_mod_log;
146 new = &tm_root->rb_node;
147 while (*new) {
148 cur = rb_entry(*new, struct tree_mod_elem, node);
149 parent = *new;
150 if (cur->logical < tm->logical)
151 new = &((*new)->rb_left);
152 else if (cur->logical > tm->logical)
153 new = &((*new)->rb_right);
154 else if (cur->seq < tm->seq)
155 new = &((*new)->rb_left);
156 else if (cur->seq > tm->seq)
157 new = &((*new)->rb_right);
158 else
159 return -EEXIST;
160 }
161
162 rb_link_node(&tm->node, parent, new);
163 rb_insert_color(&tm->node, tm_root);
164 return 0;
165}
166
167/*
168 * Determines if logging can be omitted. Returns true if it can. Otherwise, it
169 * returns false with the tree_mod_log_lock acquired. The caller must hold
170 * this until all tree mod log insertions are recorded in the rb tree and then
171 * write unlock fs_info::tree_mod_log_lock.
172 */
173static bool tree_mod_dont_log(struct btrfs_fs_info *fs_info, const struct extent_buffer *eb)
174{
175 if (!test_bit(BTRFS_FS_TREE_MOD_LOG_USERS, &fs_info->flags))
176 return true;
177 if (eb && btrfs_header_level(eb) == 0)
178 return true;
179
180 write_lock(&fs_info->tree_mod_log_lock);
181 if (list_empty(&(fs_info)->tree_mod_seq_list)) {
182 write_unlock(&fs_info->tree_mod_log_lock);
183 return true;
184 }
185
186 return false;
187}
188
189/* Similar to tree_mod_dont_log, but doesn't acquire any locks. */
190static bool tree_mod_need_log(const struct btrfs_fs_info *fs_info,
191 const struct extent_buffer *eb)
192{
193 if (!test_bit(BTRFS_FS_TREE_MOD_LOG_USERS, &fs_info->flags))
194 return false;
195 if (eb && btrfs_header_level(eb) == 0)
196 return false;
197
198 return true;
199}
200
201static struct tree_mod_elem *alloc_tree_mod_elem(const struct extent_buffer *eb,
202 int slot,
203 enum btrfs_mod_log_op op)
204{
205 struct tree_mod_elem *tm;
206
207 tm = kzalloc(sizeof(*tm), GFP_NOFS);
208 if (!tm)
209 return NULL;
210
211 tm->logical = eb->start;
212 if (op != BTRFS_MOD_LOG_KEY_ADD) {
213 btrfs_node_key(eb, &tm->key, slot);
214 tm->blockptr = btrfs_node_blockptr(eb, slot);
215 }
216 tm->op = op;
217 tm->slot = slot;
218 tm->generation = btrfs_node_ptr_generation(eb, slot);
219 RB_CLEAR_NODE(&tm->node);
220
221 return tm;
222}
223
224int btrfs_tree_mod_log_insert_key(const struct extent_buffer *eb, int slot,
225 enum btrfs_mod_log_op op)
226{
227 struct tree_mod_elem *tm;
228 int ret = 0;
229
230 if (!tree_mod_need_log(eb->fs_info, eb))
231 return 0;
232
233 tm = alloc_tree_mod_elem(eb, slot, op);
234 if (!tm)
235 ret = -ENOMEM;
236
237 if (tree_mod_dont_log(eb->fs_info, eb)) {
238 kfree(tm);
239 /*
240 * Don't error if we failed to allocate memory because we don't
241 * need to log.
242 */
243 return 0;
244 } else if (ret != 0) {
245 /*
246 * We previously failed to allocate memory and we need to log,
247 * so we have to fail.
248 */
249 goto out_unlock;
250 }
251
252 ret = tree_mod_log_insert(eb->fs_info, tm);
253out_unlock:
254 write_unlock(&eb->fs_info->tree_mod_log_lock);
255 if (ret)
256 kfree(tm);
257
258 return ret;
259}
260
261static struct tree_mod_elem *tree_mod_log_alloc_move(const struct extent_buffer *eb,
262 int dst_slot, int src_slot,
263 int nr_items)
264{
265 struct tree_mod_elem *tm;
266
267 tm = kzalloc(sizeof(*tm), GFP_NOFS);
268 if (!tm)
269 return ERR_PTR(-ENOMEM);
270
271 tm->logical = eb->start;
272 tm->slot = src_slot;
273 tm->move.dst_slot = dst_slot;
274 tm->move.nr_items = nr_items;
275 tm->op = BTRFS_MOD_LOG_MOVE_KEYS;
276 RB_CLEAR_NODE(&tm->node);
277
278 return tm;
279}
280
281int btrfs_tree_mod_log_insert_move(const struct extent_buffer *eb,
282 int dst_slot, int src_slot,
283 int nr_items)
284{
285 struct tree_mod_elem *tm = NULL;
286 struct tree_mod_elem **tm_list = NULL;
287 int ret = 0;
288 int i;
289 bool locked = false;
290
291 if (!tree_mod_need_log(eb->fs_info, eb))
292 return 0;
293
294 tm_list = kcalloc(nr_items, sizeof(struct tree_mod_elem *), GFP_NOFS);
295 if (!tm_list) {
296 ret = -ENOMEM;
297 goto lock;
298 }
299
300 tm = tree_mod_log_alloc_move(eb, dst_slot, src_slot, nr_items);
301 if (IS_ERR(tm)) {
302 ret = PTR_ERR(tm);
303 tm = NULL;
304 goto lock;
305 }
306
307 for (i = 0; i + dst_slot < src_slot && i < nr_items; i++) {
308 tm_list[i] = alloc_tree_mod_elem(eb, i + dst_slot,
309 BTRFS_MOD_LOG_KEY_REMOVE_WHILE_MOVING);
310 if (!tm_list[i]) {
311 ret = -ENOMEM;
312 goto lock;
313 }
314 }
315
316lock:
317 if (tree_mod_dont_log(eb->fs_info, eb)) {
318 /*
319 * Don't error if we failed to allocate memory because we don't
320 * need to log.
321 */
322 ret = 0;
323 goto free_tms;
324 }
325 locked = true;
326
327 /*
328 * We previously failed to allocate memory and we need to log, so we
329 * have to fail.
330 */
331 if (ret != 0)
332 goto free_tms;
333
334 /*
335 * When we override something during the move, we log these removals.
336 * This can only happen when we move towards the beginning of the
337 * buffer, i.e. dst_slot < src_slot.
338 */
339 for (i = 0; i + dst_slot < src_slot && i < nr_items; i++) {
340 ret = tree_mod_log_insert(eb->fs_info, tm_list[i]);
341 if (ret)
342 goto free_tms;
343 }
344
345 ret = tree_mod_log_insert(eb->fs_info, tm);
346 if (ret)
347 goto free_tms;
348 write_unlock(&eb->fs_info->tree_mod_log_lock);
349 kfree(tm_list);
350
351 return 0;
352
353free_tms:
354 if (tm_list) {
355 for (i = 0; i < nr_items; i++) {
356 if (tm_list[i] && !RB_EMPTY_NODE(&tm_list[i]->node))
357 rb_erase(&tm_list[i]->node, &eb->fs_info->tree_mod_log);
358 kfree(tm_list[i]);
359 }
360 }
361 if (locked)
362 write_unlock(&eb->fs_info->tree_mod_log_lock);
363 kfree(tm_list);
364 kfree(tm);
365
366 return ret;
367}
368
369static int tree_mod_log_free_eb(struct btrfs_fs_info *fs_info,
370 struct tree_mod_elem **tm_list,
371 int nritems)
372{
373 int i, j;
374 int ret;
375
376 for (i = nritems - 1; i >= 0; i--) {
377 ret = tree_mod_log_insert(fs_info, tm_list[i]);
378 if (ret) {
379 for (j = nritems - 1; j > i; j--)
380 rb_erase(&tm_list[j]->node,
381 &fs_info->tree_mod_log);
382 return ret;
383 }
384 }
385
386 return 0;
387}
388
389int btrfs_tree_mod_log_insert_root(struct extent_buffer *old_root,
390 struct extent_buffer *new_root,
391 bool log_removal)
392{
393 struct btrfs_fs_info *fs_info = old_root->fs_info;
394 struct tree_mod_elem *tm = NULL;
395 struct tree_mod_elem **tm_list = NULL;
396 int nritems = 0;
397 int ret = 0;
398 int i;
399
400 if (!tree_mod_need_log(fs_info, NULL))
401 return 0;
402
403 if (log_removal && btrfs_header_level(old_root) > 0) {
404 nritems = btrfs_header_nritems(old_root);
405 tm_list = kcalloc(nritems, sizeof(struct tree_mod_elem *),
406 GFP_NOFS);
407 if (!tm_list) {
408 ret = -ENOMEM;
409 goto lock;
410 }
411 for (i = 0; i < nritems; i++) {
412 tm_list[i] = alloc_tree_mod_elem(old_root, i,
413 BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING);
414 if (!tm_list[i]) {
415 ret = -ENOMEM;
416 goto lock;
417 }
418 }
419 }
420
421 tm = kzalloc(sizeof(*tm), GFP_NOFS);
422 if (!tm) {
423 ret = -ENOMEM;
424 goto lock;
425 }
426
427 tm->logical = new_root->start;
428 tm->old_root.logical = old_root->start;
429 tm->old_root.level = btrfs_header_level(old_root);
430 tm->generation = btrfs_header_generation(old_root);
431 tm->op = BTRFS_MOD_LOG_ROOT_REPLACE;
432
433lock:
434 if (tree_mod_dont_log(fs_info, NULL)) {
435 /*
436 * Don't error if we failed to allocate memory because we don't
437 * need to log.
438 */
439 ret = 0;
440 goto free_tms;
441 } else if (ret != 0) {
442 /*
443 * We previously failed to allocate memory and we need to log,
444 * so we have to fail.
445 */
446 goto out_unlock;
447 }
448
449 if (tm_list)
450 ret = tree_mod_log_free_eb(fs_info, tm_list, nritems);
451 if (!ret)
452 ret = tree_mod_log_insert(fs_info, tm);
453
454out_unlock:
455 write_unlock(&fs_info->tree_mod_log_lock);
456 if (ret)
457 goto free_tms;
458 kfree(tm_list);
459
460 return ret;
461
462free_tms:
463 if (tm_list) {
464 for (i = 0; i < nritems; i++)
465 kfree(tm_list[i]);
466 kfree(tm_list);
467 }
468 kfree(tm);
469
470 return ret;
471}
472
473static struct tree_mod_elem *__tree_mod_log_search(struct btrfs_fs_info *fs_info,
474 u64 start, u64 min_seq,
475 bool smallest)
476{
477 struct rb_root *tm_root;
478 struct rb_node *node;
479 struct tree_mod_elem *cur = NULL;
480 struct tree_mod_elem *found = NULL;
481
482 read_lock(&fs_info->tree_mod_log_lock);
483 tm_root = &fs_info->tree_mod_log;
484 node = tm_root->rb_node;
485 while (node) {
486 cur = rb_entry(node, struct tree_mod_elem, node);
487 if (cur->logical < start) {
488 node = node->rb_left;
489 } else if (cur->logical > start) {
490 node = node->rb_right;
491 } else if (cur->seq < min_seq) {
492 node = node->rb_left;
493 } else if (!smallest) {
494 /* We want the node with the highest seq */
495 if (found)
496 BUG_ON(found->seq > cur->seq);
497 found = cur;
498 node = node->rb_left;
499 } else if (cur->seq > min_seq) {
500 /* We want the node with the smallest seq */
501 if (found)
502 BUG_ON(found->seq < cur->seq);
503 found = cur;
504 node = node->rb_right;
505 } else {
506 found = cur;
507 break;
508 }
509 }
510 read_unlock(&fs_info->tree_mod_log_lock);
511
512 return found;
513}
514
515/*
516 * This returns the element from the log with the smallest time sequence
517 * value that's in the log (the oldest log item). Any element with a time
518 * sequence lower than min_seq will be ignored.
519 */
520static struct tree_mod_elem *tree_mod_log_search_oldest(struct btrfs_fs_info *fs_info,
521 u64 start, u64 min_seq)
522{
523 return __tree_mod_log_search(fs_info, start, min_seq, true);
524}
525
526/*
527 * This returns the element from the log with the largest time sequence
528 * value that's in the log (the most recent log item). Any element with
529 * a time sequence lower than min_seq will be ignored.
530 */
531static struct tree_mod_elem *tree_mod_log_search(struct btrfs_fs_info *fs_info,
532 u64 start, u64 min_seq)
533{
534 return __tree_mod_log_search(fs_info, start, min_seq, false);
535}
536
537int btrfs_tree_mod_log_eb_copy(struct extent_buffer *dst,
538 const struct extent_buffer *src,
539 unsigned long dst_offset,
540 unsigned long src_offset,
541 int nr_items)
542{
543 struct btrfs_fs_info *fs_info = dst->fs_info;
544 int ret = 0;
545 struct tree_mod_elem **tm_list = NULL;
546 struct tree_mod_elem **tm_list_add = NULL;
547 struct tree_mod_elem **tm_list_rem = NULL;
548 int i;
549 bool locked = false;
550 struct tree_mod_elem *dst_move_tm = NULL;
551 struct tree_mod_elem *src_move_tm = NULL;
552 u32 dst_move_nr_items = btrfs_header_nritems(dst) - dst_offset;
553 u32 src_move_nr_items = btrfs_header_nritems(src) - (src_offset + nr_items);
554
555 if (!tree_mod_need_log(fs_info, NULL))
556 return 0;
557
558 if (btrfs_header_level(dst) == 0 && btrfs_header_level(src) == 0)
559 return 0;
560
561 tm_list = kcalloc(nr_items * 2, sizeof(struct tree_mod_elem *),
562 GFP_NOFS);
563 if (!tm_list) {
564 ret = -ENOMEM;
565 goto lock;
566 }
567
568 if (dst_move_nr_items) {
569 dst_move_tm = tree_mod_log_alloc_move(dst, dst_offset + nr_items,
570 dst_offset, dst_move_nr_items);
571 if (IS_ERR(dst_move_tm)) {
572 ret = PTR_ERR(dst_move_tm);
573 dst_move_tm = NULL;
574 goto lock;
575 }
576 }
577 if (src_move_nr_items) {
578 src_move_tm = tree_mod_log_alloc_move(src, src_offset,
579 src_offset + nr_items,
580 src_move_nr_items);
581 if (IS_ERR(src_move_tm)) {
582 ret = PTR_ERR(src_move_tm);
583 src_move_tm = NULL;
584 goto lock;
585 }
586 }
587
588 tm_list_add = tm_list;
589 tm_list_rem = tm_list + nr_items;
590 for (i = 0; i < nr_items; i++) {
591 tm_list_rem[i] = alloc_tree_mod_elem(src, i + src_offset,
592 BTRFS_MOD_LOG_KEY_REMOVE);
593 if (!tm_list_rem[i]) {
594 ret = -ENOMEM;
595 goto lock;
596 }
597
598 tm_list_add[i] = alloc_tree_mod_elem(dst, i + dst_offset,
599 BTRFS_MOD_LOG_KEY_ADD);
600 if (!tm_list_add[i]) {
601 ret = -ENOMEM;
602 goto lock;
603 }
604 }
605
606lock:
607 if (tree_mod_dont_log(fs_info, NULL)) {
608 /*
609 * Don't error if we failed to allocate memory because we don't
610 * need to log.
611 */
612 ret = 0;
613 goto free_tms;
614 }
615 locked = true;
616
617 /*
618 * We previously failed to allocate memory and we need to log, so we
619 * have to fail.
620 */
621 if (ret != 0)
622 goto free_tms;
623
624 if (dst_move_tm) {
625 ret = tree_mod_log_insert(fs_info, dst_move_tm);
626 if (ret)
627 goto free_tms;
628 }
629 for (i = 0; i < nr_items; i++) {
630 ret = tree_mod_log_insert(fs_info, tm_list_rem[i]);
631 if (ret)
632 goto free_tms;
633 ret = tree_mod_log_insert(fs_info, tm_list_add[i]);
634 if (ret)
635 goto free_tms;
636 }
637 if (src_move_tm) {
638 ret = tree_mod_log_insert(fs_info, src_move_tm);
639 if (ret)
640 goto free_tms;
641 }
642
643 write_unlock(&fs_info->tree_mod_log_lock);
644 kfree(tm_list);
645
646 return 0;
647
648free_tms:
649 if (dst_move_tm && !RB_EMPTY_NODE(&dst_move_tm->node))
650 rb_erase(&dst_move_tm->node, &fs_info->tree_mod_log);
651 kfree(dst_move_tm);
652 if (src_move_tm && !RB_EMPTY_NODE(&src_move_tm->node))
653 rb_erase(&src_move_tm->node, &fs_info->tree_mod_log);
654 kfree(src_move_tm);
655 if (tm_list) {
656 for (i = 0; i < nr_items * 2; i++) {
657 if (tm_list[i] && !RB_EMPTY_NODE(&tm_list[i]->node))
658 rb_erase(&tm_list[i]->node, &fs_info->tree_mod_log);
659 kfree(tm_list[i]);
660 }
661 }
662 if (locked)
663 write_unlock(&fs_info->tree_mod_log_lock);
664 kfree(tm_list);
665
666 return ret;
667}
668
669int btrfs_tree_mod_log_free_eb(struct extent_buffer *eb)
670{
671 struct tree_mod_elem **tm_list = NULL;
672 int nritems = 0;
673 int i;
674 int ret = 0;
675
676 if (!tree_mod_need_log(eb->fs_info, eb))
677 return 0;
678
679 nritems = btrfs_header_nritems(eb);
680 tm_list = kcalloc(nritems, sizeof(struct tree_mod_elem *), GFP_NOFS);
681 if (!tm_list) {
682 ret = -ENOMEM;
683 goto lock;
684 }
685
686 for (i = 0; i < nritems; i++) {
687 tm_list[i] = alloc_tree_mod_elem(eb, i,
688 BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING);
689 if (!tm_list[i]) {
690 ret = -ENOMEM;
691 goto lock;
692 }
693 }
694
695lock:
696 if (tree_mod_dont_log(eb->fs_info, eb)) {
697 /*
698 * Don't error if we failed to allocate memory because we don't
699 * need to log.
700 */
701 ret = 0;
702 goto free_tms;
703 } else if (ret != 0) {
704 /*
705 * We previously failed to allocate memory and we need to log,
706 * so we have to fail.
707 */
708 goto out_unlock;
709 }
710
711 ret = tree_mod_log_free_eb(eb->fs_info, tm_list, nritems);
712out_unlock:
713 write_unlock(&eb->fs_info->tree_mod_log_lock);
714 if (ret)
715 goto free_tms;
716 kfree(tm_list);
717
718 return 0;
719
720free_tms:
721 if (tm_list) {
722 for (i = 0; i < nritems; i++)
723 kfree(tm_list[i]);
724 kfree(tm_list);
725 }
726
727 return ret;
728}
729
730/*
731 * Returns the logical address of the oldest predecessor of the given root.
732 * Entries older than time_seq are ignored.
733 */
734static struct tree_mod_elem *tree_mod_log_oldest_root(struct extent_buffer *eb_root,
735 u64 time_seq)
736{
737 struct tree_mod_elem *tm;
738 struct tree_mod_elem *found = NULL;
739 u64 root_logical = eb_root->start;
740 bool looped = false;
741
742 if (!time_seq)
743 return NULL;
744
745 /*
746 * The very last operation that's logged for a root is the replacement
747 * operation (if it is replaced at all). This has the logical address
748 * of the *new* root, making it the very first operation that's logged
749 * for this root.
750 */
751 while (1) {
752 tm = tree_mod_log_search_oldest(eb_root->fs_info, root_logical,
753 time_seq);
754 if (!looped && !tm)
755 return NULL;
756 /*
757 * If there are no tree operation for the oldest root, we simply
758 * return it. This should only happen if that (old) root is at
759 * level 0.
760 */
761 if (!tm)
762 break;
763
764 /*
765 * If there's an operation that's not a root replacement, we
766 * found the oldest version of our root. Normally, we'll find a
767 * BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING operation here.
768 */
769 if (tm->op != BTRFS_MOD_LOG_ROOT_REPLACE)
770 break;
771
772 found = tm;
773 root_logical = tm->old_root.logical;
774 looped = true;
775 }
776
777 /* If there's no old root to return, return what we found instead */
778 if (!found)
779 found = tm;
780
781 return found;
782}
783
784
785/*
786 * tm is a pointer to the first operation to rewind within eb. Then, all
787 * previous operations will be rewound (until we reach something older than
788 * time_seq).
789 */
790static void tree_mod_log_rewind(struct btrfs_fs_info *fs_info,
791 struct extent_buffer *eb,
792 u64 time_seq,
793 struct tree_mod_elem *first_tm)
794{
795 u32 n;
796 struct rb_node *next;
797 struct tree_mod_elem *tm = first_tm;
798 unsigned long o_dst;
799 unsigned long o_src;
800 unsigned long p_size = sizeof(struct btrfs_key_ptr);
801 /*
802 * max_slot tracks the maximum valid slot of the rewind eb at every
803 * step of the rewind. This is in contrast with 'n' which eventually
804 * matches the number of items, but can be wrong during moves or if
805 * removes overlap on already valid slots (which is probably separately
806 * a bug). We do this to validate the offsets of memmoves for rewinding
807 * moves and detect invalid memmoves.
808 *
809 * Since a rewind eb can start empty, max_slot is a signed integer with
810 * a special meaning for -1, which is that no slot is valid to move out
811 * of. Any other negative value is invalid.
812 */
813 int max_slot;
814 int move_src_end_slot;
815 int move_dst_end_slot;
816
817 n = btrfs_header_nritems(eb);
818 max_slot = n - 1;
819 read_lock(&fs_info->tree_mod_log_lock);
820 while (tm && tm->seq >= time_seq) {
821 ASSERT(max_slot >= -1);
822 /*
823 * All the operations are recorded with the operator used for
824 * the modification. As we're going backwards, we do the
825 * opposite of each operation here.
826 */
827 switch (tm->op) {
828 case BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING:
829 BUG_ON(tm->slot < n);
830 fallthrough;
831 case BTRFS_MOD_LOG_KEY_REMOVE_WHILE_MOVING:
832 case BTRFS_MOD_LOG_KEY_REMOVE:
833 btrfs_set_node_key(eb, &tm->key, tm->slot);
834 btrfs_set_node_blockptr(eb, tm->slot, tm->blockptr);
835 btrfs_set_node_ptr_generation(eb, tm->slot,
836 tm->generation);
837 n++;
838 if (tm->slot > max_slot)
839 max_slot = tm->slot;
840 break;
841 case BTRFS_MOD_LOG_KEY_REPLACE:
842 BUG_ON(tm->slot >= n);
843 btrfs_set_node_key(eb, &tm->key, tm->slot);
844 btrfs_set_node_blockptr(eb, tm->slot, tm->blockptr);
845 btrfs_set_node_ptr_generation(eb, tm->slot,
846 tm->generation);
847 break;
848 case BTRFS_MOD_LOG_KEY_ADD:
849 /*
850 * It is possible we could have already removed keys
851 * behind the known max slot, so this will be an
852 * overestimate. In practice, the copy operation
853 * inserts them in increasing order, and overestimating
854 * just means we miss some warnings, so it's OK. It
855 * isn't worth carefully tracking the full array of
856 * valid slots to check against when moving.
857 */
858 if (tm->slot == max_slot)
859 max_slot--;
860 /* if a move operation is needed it's in the log */
861 n--;
862 break;
863 case BTRFS_MOD_LOG_MOVE_KEYS:
864 ASSERT(tm->move.nr_items > 0);
865 move_src_end_slot = tm->move.dst_slot + tm->move.nr_items - 1;
866 move_dst_end_slot = tm->slot + tm->move.nr_items - 1;
867 o_dst = btrfs_node_key_ptr_offset(eb, tm->slot);
868 o_src = btrfs_node_key_ptr_offset(eb, tm->move.dst_slot);
869 if (WARN_ON(move_src_end_slot > max_slot ||
870 tm->move.nr_items <= 0)) {
871 btrfs_warn(fs_info,
872"move from invalid tree mod log slot eb %llu slot %d dst_slot %d nr_items %d seq %llu n %u max_slot %d",
873 eb->start, tm->slot,
874 tm->move.dst_slot, tm->move.nr_items,
875 tm->seq, n, max_slot);
876 }
877 memmove_extent_buffer(eb, o_dst, o_src,
878 tm->move.nr_items * p_size);
879 max_slot = move_dst_end_slot;
880 break;
881 case BTRFS_MOD_LOG_ROOT_REPLACE:
882 /*
883 * This operation is special. For roots, this must be
884 * handled explicitly before rewinding.
885 * For non-roots, this operation may exist if the node
886 * was a root: root A -> child B; then A gets empty and
887 * B is promoted to the new root. In the mod log, we'll
888 * have a root-replace operation for B, a tree block
889 * that is no root. We simply ignore that operation.
890 */
891 break;
892 }
893 next = rb_next(&tm->node);
894 if (!next)
895 break;
896 tm = rb_entry(next, struct tree_mod_elem, node);
897 if (tm->logical != first_tm->logical)
898 break;
899 }
900 read_unlock(&fs_info->tree_mod_log_lock);
901 btrfs_set_header_nritems(eb, n);
902}
903
904/*
905 * Called with eb read locked. If the buffer cannot be rewound, the same buffer
906 * is returned. If rewind operations happen, a fresh buffer is returned. The
907 * returned buffer is always read-locked. If the returned buffer is not the
908 * input buffer, the lock on the input buffer is released and the input buffer
909 * is freed (its refcount is decremented).
910 */
911struct extent_buffer *btrfs_tree_mod_log_rewind(struct btrfs_fs_info *fs_info,
912 struct extent_buffer *eb,
913 u64 time_seq)
914{
915 struct extent_buffer *eb_rewin;
916 struct tree_mod_elem *tm;
917
918 if (!time_seq)
919 return eb;
920
921 if (btrfs_header_level(eb) == 0)
922 return eb;
923
924 tm = tree_mod_log_search(fs_info, eb->start, time_seq);
925 if (!tm)
926 return eb;
927
928 if (tm->op == BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING) {
929 BUG_ON(tm->slot != 0);
930 eb_rewin = alloc_dummy_extent_buffer(fs_info, eb->start);
931 if (!eb_rewin) {
932 btrfs_tree_read_unlock(eb);
933 free_extent_buffer(eb);
934 return NULL;
935 }
936 btrfs_set_header_bytenr(eb_rewin, eb->start);
937 btrfs_set_header_backref_rev(eb_rewin,
938 btrfs_header_backref_rev(eb));
939 btrfs_set_header_owner(eb_rewin, btrfs_header_owner(eb));
940 btrfs_set_header_level(eb_rewin, btrfs_header_level(eb));
941 } else {
942 eb_rewin = btrfs_clone_extent_buffer(eb);
943 if (!eb_rewin) {
944 btrfs_tree_read_unlock(eb);
945 free_extent_buffer(eb);
946 return NULL;
947 }
948 }
949
950 btrfs_tree_read_unlock(eb);
951 free_extent_buffer(eb);
952
953 btrfs_set_buffer_lockdep_class(btrfs_header_owner(eb_rewin),
954 eb_rewin, btrfs_header_level(eb_rewin));
955 btrfs_tree_read_lock(eb_rewin);
956 tree_mod_log_rewind(fs_info, eb_rewin, time_seq, tm);
957 WARN_ON(btrfs_header_nritems(eb_rewin) >
958 BTRFS_NODEPTRS_PER_BLOCK(fs_info));
959
960 return eb_rewin;
961}
962
963/*
964 * Rewind the state of @root's root node to the given @time_seq value.
965 * If there are no changes, the current root->root_node is returned. If anything
966 * changed in between, there's a fresh buffer allocated on which the rewind
967 * operations are done. In any case, the returned buffer is read locked.
968 * Returns NULL on error (with no locks held).
969 */
970struct extent_buffer *btrfs_get_old_root(struct btrfs_root *root, u64 time_seq)
971{
972 struct btrfs_fs_info *fs_info = root->fs_info;
973 struct tree_mod_elem *tm;
974 struct extent_buffer *eb = NULL;
975 struct extent_buffer *eb_root;
976 u64 eb_root_owner = 0;
977 struct extent_buffer *old;
978 struct tree_mod_root *old_root = NULL;
979 u64 old_generation = 0;
980 u64 logical;
981 int level;
982
983 eb_root = btrfs_read_lock_root_node(root);
984 tm = tree_mod_log_oldest_root(eb_root, time_seq);
985 if (!tm)
986 return eb_root;
987
988 if (tm->op == BTRFS_MOD_LOG_ROOT_REPLACE) {
989 old_root = &tm->old_root;
990 old_generation = tm->generation;
991 logical = old_root->logical;
992 level = old_root->level;
993 } else {
994 logical = eb_root->start;
995 level = btrfs_header_level(eb_root);
996 }
997
998 tm = tree_mod_log_search(fs_info, logical, time_seq);
999 if (old_root && tm && tm->op != BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING) {
1000 struct btrfs_tree_parent_check check = { 0 };
1001
1002 btrfs_tree_read_unlock(eb_root);
1003 free_extent_buffer(eb_root);
1004
1005 check.level = level;
1006 check.owner_root = btrfs_root_id(root);
1007
1008 old = read_tree_block(fs_info, logical, &check);
1009 if (WARN_ON(IS_ERR(old) || !extent_buffer_uptodate(old))) {
1010 if (!IS_ERR(old))
1011 free_extent_buffer(old);
1012 btrfs_warn(fs_info,
1013 "failed to read tree block %llu from get_old_root",
1014 logical);
1015 } else {
1016 struct tree_mod_elem *tm2;
1017
1018 btrfs_tree_read_lock(old);
1019 eb = btrfs_clone_extent_buffer(old);
1020 /*
1021 * After the lookup for the most recent tree mod operation
1022 * above and before we locked and cloned the extent buffer
1023 * 'old', a new tree mod log operation may have been added.
1024 * So lookup for a more recent one to make sure the number
1025 * of mod log operations we replay is consistent with the
1026 * number of items we have in the cloned extent buffer,
1027 * otherwise we can hit a BUG_ON when rewinding the extent
1028 * buffer.
1029 */
1030 tm2 = tree_mod_log_search(fs_info, logical, time_seq);
1031 btrfs_tree_read_unlock(old);
1032 free_extent_buffer(old);
1033 ASSERT(tm2);
1034 ASSERT(tm2 == tm || tm2->seq > tm->seq);
1035 if (!tm2 || tm2->seq < tm->seq) {
1036 free_extent_buffer(eb);
1037 return NULL;
1038 }
1039 tm = tm2;
1040 }
1041 } else if (old_root) {
1042 eb_root_owner = btrfs_header_owner(eb_root);
1043 btrfs_tree_read_unlock(eb_root);
1044 free_extent_buffer(eb_root);
1045 eb = alloc_dummy_extent_buffer(fs_info, logical);
1046 } else {
1047 eb = btrfs_clone_extent_buffer(eb_root);
1048 btrfs_tree_read_unlock(eb_root);
1049 free_extent_buffer(eb_root);
1050 }
1051
1052 if (!eb)
1053 return NULL;
1054 if (old_root) {
1055 btrfs_set_header_bytenr(eb, eb->start);
1056 btrfs_set_header_backref_rev(eb, BTRFS_MIXED_BACKREF_REV);
1057 btrfs_set_header_owner(eb, eb_root_owner);
1058 btrfs_set_header_level(eb, old_root->level);
1059 btrfs_set_header_generation(eb, old_generation);
1060 }
1061 btrfs_set_buffer_lockdep_class(btrfs_header_owner(eb), eb,
1062 btrfs_header_level(eb));
1063 btrfs_tree_read_lock(eb);
1064 if (tm)
1065 tree_mod_log_rewind(fs_info, eb, time_seq, tm);
1066 else
1067 WARN_ON(btrfs_header_level(eb) != 0);
1068 WARN_ON(btrfs_header_nritems(eb) > BTRFS_NODEPTRS_PER_BLOCK(fs_info));
1069
1070 return eb;
1071}
1072
1073int btrfs_old_root_level(struct btrfs_root *root, u64 time_seq)
1074{
1075 struct tree_mod_elem *tm;
1076 int level;
1077 struct extent_buffer *eb_root = btrfs_root_node(root);
1078
1079 tm = tree_mod_log_oldest_root(eb_root, time_seq);
1080 if (tm && tm->op == BTRFS_MOD_LOG_ROOT_REPLACE)
1081 level = tm->old_root.level;
1082 else
1083 level = btrfs_header_level(eb_root);
1084
1085 free_extent_buffer(eb_root);
1086
1087 return level;
1088}
1089
1090/*
1091 * Return the lowest sequence number in the tree modification log.
1092 *
1093 * Return the sequence number of the oldest tree modification log user, which
1094 * corresponds to the lowest sequence number of all existing users. If there are
1095 * no users it returns 0.
1096 */
1097u64 btrfs_tree_mod_log_lowest_seq(struct btrfs_fs_info *fs_info)
1098{
1099 u64 ret = 0;
1100
1101 read_lock(&fs_info->tree_mod_log_lock);
1102 if (!list_empty(&fs_info->tree_mod_seq_list)) {
1103 struct btrfs_seq_list *elem;
1104
1105 elem = list_first_entry(&fs_info->tree_mod_seq_list,
1106 struct btrfs_seq_list, list);
1107 ret = elem->seq;
1108 }
1109 read_unlock(&fs_info->tree_mod_log_lock);
1110
1111 return ret;
1112}