Loading...
Note: File does not exist in v3.5.6.
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 inline 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 inline bool tree_mod_dont_log(struct btrfs_fs_info *fs_info,
174 struct extent_buffer *eb)
175{
176 if (!test_bit(BTRFS_FS_TREE_MOD_LOG_USERS, &fs_info->flags))
177 return true;
178 if (eb && btrfs_header_level(eb) == 0)
179 return true;
180
181 write_lock(&fs_info->tree_mod_log_lock);
182 if (list_empty(&(fs_info)->tree_mod_seq_list)) {
183 write_unlock(&fs_info->tree_mod_log_lock);
184 return true;
185 }
186
187 return false;
188}
189
190/* Similar to tree_mod_dont_log, but doesn't acquire any locks. */
191static inline bool tree_mod_need_log(const struct btrfs_fs_info *fs_info,
192 struct extent_buffer *eb)
193{
194 if (!test_bit(BTRFS_FS_TREE_MOD_LOG_USERS, &fs_info->flags))
195 return false;
196 if (eb && btrfs_header_level(eb) == 0)
197 return false;
198
199 return true;
200}
201
202static struct tree_mod_elem *alloc_tree_mod_elem(struct extent_buffer *eb,
203 int slot,
204 enum btrfs_mod_log_op op)
205{
206 struct tree_mod_elem *tm;
207
208 tm = kzalloc(sizeof(*tm), GFP_NOFS);
209 if (!tm)
210 return NULL;
211
212 tm->logical = eb->start;
213 if (op != BTRFS_MOD_LOG_KEY_ADD) {
214 btrfs_node_key(eb, &tm->key, slot);
215 tm->blockptr = btrfs_node_blockptr(eb, slot);
216 }
217 tm->op = op;
218 tm->slot = slot;
219 tm->generation = btrfs_node_ptr_generation(eb, slot);
220 RB_CLEAR_NODE(&tm->node);
221
222 return tm;
223}
224
225int btrfs_tree_mod_log_insert_key(struct extent_buffer *eb, int slot,
226 enum btrfs_mod_log_op op)
227{
228 struct tree_mod_elem *tm;
229 int ret;
230
231 if (!tree_mod_need_log(eb->fs_info, eb))
232 return 0;
233
234 tm = alloc_tree_mod_elem(eb, slot, op);
235 if (!tm)
236 return -ENOMEM;
237
238 if (tree_mod_dont_log(eb->fs_info, eb)) {
239 kfree(tm);
240 return 0;
241 }
242
243 ret = tree_mod_log_insert(eb->fs_info, tm);
244 write_unlock(&eb->fs_info->tree_mod_log_lock);
245 if (ret)
246 kfree(tm);
247
248 return ret;
249}
250
251int btrfs_tree_mod_log_insert_move(struct extent_buffer *eb,
252 int dst_slot, int src_slot,
253 int nr_items)
254{
255 struct tree_mod_elem *tm = NULL;
256 struct tree_mod_elem **tm_list = NULL;
257 int ret = 0;
258 int i;
259 bool locked = false;
260
261 if (!tree_mod_need_log(eb->fs_info, eb))
262 return 0;
263
264 tm_list = kcalloc(nr_items, sizeof(struct tree_mod_elem *), GFP_NOFS);
265 if (!tm_list)
266 return -ENOMEM;
267
268 tm = kzalloc(sizeof(*tm), GFP_NOFS);
269 if (!tm) {
270 ret = -ENOMEM;
271 goto free_tms;
272 }
273
274 tm->logical = eb->start;
275 tm->slot = src_slot;
276 tm->move.dst_slot = dst_slot;
277 tm->move.nr_items = nr_items;
278 tm->op = BTRFS_MOD_LOG_MOVE_KEYS;
279
280 for (i = 0; i + dst_slot < src_slot && i < nr_items; i++) {
281 tm_list[i] = alloc_tree_mod_elem(eb, i + dst_slot,
282 BTRFS_MOD_LOG_KEY_REMOVE_WHILE_MOVING);
283 if (!tm_list[i]) {
284 ret = -ENOMEM;
285 goto free_tms;
286 }
287 }
288
289 if (tree_mod_dont_log(eb->fs_info, eb))
290 goto free_tms;
291 locked = true;
292
293 /*
294 * When we override something during the move, we log these removals.
295 * This can only happen when we move towards the beginning of the
296 * buffer, i.e. dst_slot < src_slot.
297 */
298 for (i = 0; i + dst_slot < src_slot && i < nr_items; i++) {
299 ret = tree_mod_log_insert(eb->fs_info, tm_list[i]);
300 if (ret)
301 goto free_tms;
302 }
303
304 ret = tree_mod_log_insert(eb->fs_info, tm);
305 if (ret)
306 goto free_tms;
307 write_unlock(&eb->fs_info->tree_mod_log_lock);
308 kfree(tm_list);
309
310 return 0;
311
312free_tms:
313 for (i = 0; i < nr_items; i++) {
314 if (tm_list[i] && !RB_EMPTY_NODE(&tm_list[i]->node))
315 rb_erase(&tm_list[i]->node, &eb->fs_info->tree_mod_log);
316 kfree(tm_list[i]);
317 }
318 if (locked)
319 write_unlock(&eb->fs_info->tree_mod_log_lock);
320 kfree(tm_list);
321 kfree(tm);
322
323 return ret;
324}
325
326static inline int tree_mod_log_free_eb(struct btrfs_fs_info *fs_info,
327 struct tree_mod_elem **tm_list,
328 int nritems)
329{
330 int i, j;
331 int ret;
332
333 for (i = nritems - 1; i >= 0; i--) {
334 ret = tree_mod_log_insert(fs_info, tm_list[i]);
335 if (ret) {
336 for (j = nritems - 1; j > i; j--)
337 rb_erase(&tm_list[j]->node,
338 &fs_info->tree_mod_log);
339 return ret;
340 }
341 }
342
343 return 0;
344}
345
346int btrfs_tree_mod_log_insert_root(struct extent_buffer *old_root,
347 struct extent_buffer *new_root,
348 bool log_removal)
349{
350 struct btrfs_fs_info *fs_info = old_root->fs_info;
351 struct tree_mod_elem *tm = NULL;
352 struct tree_mod_elem **tm_list = NULL;
353 int nritems = 0;
354 int ret = 0;
355 int i;
356
357 if (!tree_mod_need_log(fs_info, NULL))
358 return 0;
359
360 if (log_removal && btrfs_header_level(old_root) > 0) {
361 nritems = btrfs_header_nritems(old_root);
362 tm_list = kcalloc(nritems, sizeof(struct tree_mod_elem *),
363 GFP_NOFS);
364 if (!tm_list) {
365 ret = -ENOMEM;
366 goto free_tms;
367 }
368 for (i = 0; i < nritems; i++) {
369 tm_list[i] = alloc_tree_mod_elem(old_root, i,
370 BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING);
371 if (!tm_list[i]) {
372 ret = -ENOMEM;
373 goto free_tms;
374 }
375 }
376 }
377
378 tm = kzalloc(sizeof(*tm), GFP_NOFS);
379 if (!tm) {
380 ret = -ENOMEM;
381 goto free_tms;
382 }
383
384 tm->logical = new_root->start;
385 tm->old_root.logical = old_root->start;
386 tm->old_root.level = btrfs_header_level(old_root);
387 tm->generation = btrfs_header_generation(old_root);
388 tm->op = BTRFS_MOD_LOG_ROOT_REPLACE;
389
390 if (tree_mod_dont_log(fs_info, NULL))
391 goto free_tms;
392
393 if (tm_list)
394 ret = tree_mod_log_free_eb(fs_info, tm_list, nritems);
395 if (!ret)
396 ret = tree_mod_log_insert(fs_info, tm);
397
398 write_unlock(&fs_info->tree_mod_log_lock);
399 if (ret)
400 goto free_tms;
401 kfree(tm_list);
402
403 return ret;
404
405free_tms:
406 if (tm_list) {
407 for (i = 0; i < nritems; i++)
408 kfree(tm_list[i]);
409 kfree(tm_list);
410 }
411 kfree(tm);
412
413 return ret;
414}
415
416static struct tree_mod_elem *__tree_mod_log_search(struct btrfs_fs_info *fs_info,
417 u64 start, u64 min_seq,
418 bool smallest)
419{
420 struct rb_root *tm_root;
421 struct rb_node *node;
422 struct tree_mod_elem *cur = NULL;
423 struct tree_mod_elem *found = NULL;
424
425 read_lock(&fs_info->tree_mod_log_lock);
426 tm_root = &fs_info->tree_mod_log;
427 node = tm_root->rb_node;
428 while (node) {
429 cur = rb_entry(node, struct tree_mod_elem, node);
430 if (cur->logical < start) {
431 node = node->rb_left;
432 } else if (cur->logical > start) {
433 node = node->rb_right;
434 } else if (cur->seq < min_seq) {
435 node = node->rb_left;
436 } else if (!smallest) {
437 /* We want the node with the highest seq */
438 if (found)
439 BUG_ON(found->seq > cur->seq);
440 found = cur;
441 node = node->rb_left;
442 } else if (cur->seq > min_seq) {
443 /* We want the node with the smallest seq */
444 if (found)
445 BUG_ON(found->seq < cur->seq);
446 found = cur;
447 node = node->rb_right;
448 } else {
449 found = cur;
450 break;
451 }
452 }
453 read_unlock(&fs_info->tree_mod_log_lock);
454
455 return found;
456}
457
458/*
459 * This returns the element from the log with the smallest time sequence
460 * value that's in the log (the oldest log item). Any element with a time
461 * sequence lower than min_seq will be ignored.
462 */
463static struct tree_mod_elem *tree_mod_log_search_oldest(struct btrfs_fs_info *fs_info,
464 u64 start, u64 min_seq)
465{
466 return __tree_mod_log_search(fs_info, start, min_seq, true);
467}
468
469/*
470 * This returns the element from the log with the largest time sequence
471 * value that's in the log (the most recent log item). Any element with
472 * a time sequence lower than min_seq will be ignored.
473 */
474static struct tree_mod_elem *tree_mod_log_search(struct btrfs_fs_info *fs_info,
475 u64 start, u64 min_seq)
476{
477 return __tree_mod_log_search(fs_info, start, min_seq, false);
478}
479
480int btrfs_tree_mod_log_eb_copy(struct extent_buffer *dst,
481 struct extent_buffer *src,
482 unsigned long dst_offset,
483 unsigned long src_offset,
484 int nr_items)
485{
486 struct btrfs_fs_info *fs_info = dst->fs_info;
487 int ret = 0;
488 struct tree_mod_elem **tm_list = NULL;
489 struct tree_mod_elem **tm_list_add, **tm_list_rem;
490 int i;
491 bool locked = false;
492
493 if (!tree_mod_need_log(fs_info, NULL))
494 return 0;
495
496 if (btrfs_header_level(dst) == 0 && btrfs_header_level(src) == 0)
497 return 0;
498
499 tm_list = kcalloc(nr_items * 2, sizeof(struct tree_mod_elem *),
500 GFP_NOFS);
501 if (!tm_list)
502 return -ENOMEM;
503
504 tm_list_add = tm_list;
505 tm_list_rem = tm_list + nr_items;
506 for (i = 0; i < nr_items; i++) {
507 tm_list_rem[i] = alloc_tree_mod_elem(src, i + src_offset,
508 BTRFS_MOD_LOG_KEY_REMOVE);
509 if (!tm_list_rem[i]) {
510 ret = -ENOMEM;
511 goto free_tms;
512 }
513
514 tm_list_add[i] = alloc_tree_mod_elem(dst, i + dst_offset,
515 BTRFS_MOD_LOG_KEY_ADD);
516 if (!tm_list_add[i]) {
517 ret = -ENOMEM;
518 goto free_tms;
519 }
520 }
521
522 if (tree_mod_dont_log(fs_info, NULL))
523 goto free_tms;
524 locked = true;
525
526 for (i = 0; i < nr_items; i++) {
527 ret = tree_mod_log_insert(fs_info, tm_list_rem[i]);
528 if (ret)
529 goto free_tms;
530 ret = tree_mod_log_insert(fs_info, tm_list_add[i]);
531 if (ret)
532 goto free_tms;
533 }
534
535 write_unlock(&fs_info->tree_mod_log_lock);
536 kfree(tm_list);
537
538 return 0;
539
540free_tms:
541 for (i = 0; i < nr_items * 2; i++) {
542 if (tm_list[i] && !RB_EMPTY_NODE(&tm_list[i]->node))
543 rb_erase(&tm_list[i]->node, &fs_info->tree_mod_log);
544 kfree(tm_list[i]);
545 }
546 if (locked)
547 write_unlock(&fs_info->tree_mod_log_lock);
548 kfree(tm_list);
549
550 return ret;
551}
552
553int btrfs_tree_mod_log_free_eb(struct extent_buffer *eb)
554{
555 struct tree_mod_elem **tm_list = NULL;
556 int nritems = 0;
557 int i;
558 int ret = 0;
559
560 if (!tree_mod_need_log(eb->fs_info, eb))
561 return 0;
562
563 nritems = btrfs_header_nritems(eb);
564 tm_list = kcalloc(nritems, sizeof(struct tree_mod_elem *), GFP_NOFS);
565 if (!tm_list)
566 return -ENOMEM;
567
568 for (i = 0; i < nritems; i++) {
569 tm_list[i] = alloc_tree_mod_elem(eb, i,
570 BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING);
571 if (!tm_list[i]) {
572 ret = -ENOMEM;
573 goto free_tms;
574 }
575 }
576
577 if (tree_mod_dont_log(eb->fs_info, eb))
578 goto free_tms;
579
580 ret = tree_mod_log_free_eb(eb->fs_info, tm_list, nritems);
581 write_unlock(&eb->fs_info->tree_mod_log_lock);
582 if (ret)
583 goto free_tms;
584 kfree(tm_list);
585
586 return 0;
587
588free_tms:
589 for (i = 0; i < nritems; i++)
590 kfree(tm_list[i]);
591 kfree(tm_list);
592
593 return ret;
594}
595
596/*
597 * Returns the logical address of the oldest predecessor of the given root.
598 * Entries older than time_seq are ignored.
599 */
600static struct tree_mod_elem *tree_mod_log_oldest_root(struct extent_buffer *eb_root,
601 u64 time_seq)
602{
603 struct tree_mod_elem *tm;
604 struct tree_mod_elem *found = NULL;
605 u64 root_logical = eb_root->start;
606 bool looped = false;
607
608 if (!time_seq)
609 return NULL;
610
611 /*
612 * The very last operation that's logged for a root is the replacement
613 * operation (if it is replaced at all). This has the logical address
614 * of the *new* root, making it the very first operation that's logged
615 * for this root.
616 */
617 while (1) {
618 tm = tree_mod_log_search_oldest(eb_root->fs_info, root_logical,
619 time_seq);
620 if (!looped && !tm)
621 return NULL;
622 /*
623 * If there are no tree operation for the oldest root, we simply
624 * return it. This should only happen if that (old) root is at
625 * level 0.
626 */
627 if (!tm)
628 break;
629
630 /*
631 * If there's an operation that's not a root replacement, we
632 * found the oldest version of our root. Normally, we'll find a
633 * BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING operation here.
634 */
635 if (tm->op != BTRFS_MOD_LOG_ROOT_REPLACE)
636 break;
637
638 found = tm;
639 root_logical = tm->old_root.logical;
640 looped = true;
641 }
642
643 /* If there's no old root to return, return what we found instead */
644 if (!found)
645 found = tm;
646
647 return found;
648}
649
650
651/*
652 * tm is a pointer to the first operation to rewind within eb. Then, all
653 * previous operations will be rewound (until we reach something older than
654 * time_seq).
655 */
656static void tree_mod_log_rewind(struct btrfs_fs_info *fs_info,
657 struct extent_buffer *eb,
658 u64 time_seq,
659 struct tree_mod_elem *first_tm)
660{
661 u32 n;
662 struct rb_node *next;
663 struct tree_mod_elem *tm = first_tm;
664 unsigned long o_dst;
665 unsigned long o_src;
666 unsigned long p_size = sizeof(struct btrfs_key_ptr);
667
668 n = btrfs_header_nritems(eb);
669 read_lock(&fs_info->tree_mod_log_lock);
670 while (tm && tm->seq >= time_seq) {
671 /*
672 * All the operations are recorded with the operator used for
673 * the modification. As we're going backwards, we do the
674 * opposite of each operation here.
675 */
676 switch (tm->op) {
677 case BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING:
678 BUG_ON(tm->slot < n);
679 fallthrough;
680 case BTRFS_MOD_LOG_KEY_REMOVE_WHILE_MOVING:
681 case BTRFS_MOD_LOG_KEY_REMOVE:
682 btrfs_set_node_key(eb, &tm->key, tm->slot);
683 btrfs_set_node_blockptr(eb, tm->slot, tm->blockptr);
684 btrfs_set_node_ptr_generation(eb, tm->slot,
685 tm->generation);
686 n++;
687 break;
688 case BTRFS_MOD_LOG_KEY_REPLACE:
689 BUG_ON(tm->slot >= n);
690 btrfs_set_node_key(eb, &tm->key, tm->slot);
691 btrfs_set_node_blockptr(eb, tm->slot, tm->blockptr);
692 btrfs_set_node_ptr_generation(eb, tm->slot,
693 tm->generation);
694 break;
695 case BTRFS_MOD_LOG_KEY_ADD:
696 /* if a move operation is needed it's in the log */
697 n--;
698 break;
699 case BTRFS_MOD_LOG_MOVE_KEYS:
700 o_dst = btrfs_node_key_ptr_offset(eb, tm->slot);
701 o_src = btrfs_node_key_ptr_offset(eb, tm->move.dst_slot);
702 memmove_extent_buffer(eb, o_dst, o_src,
703 tm->move.nr_items * p_size);
704 break;
705 case BTRFS_MOD_LOG_ROOT_REPLACE:
706 /*
707 * This operation is special. For roots, this must be
708 * handled explicitly before rewinding.
709 * For non-roots, this operation may exist if the node
710 * was a root: root A -> child B; then A gets empty and
711 * B is promoted to the new root. In the mod log, we'll
712 * have a root-replace operation for B, a tree block
713 * that is no root. We simply ignore that operation.
714 */
715 break;
716 }
717 next = rb_next(&tm->node);
718 if (!next)
719 break;
720 tm = rb_entry(next, struct tree_mod_elem, node);
721 if (tm->logical != first_tm->logical)
722 break;
723 }
724 read_unlock(&fs_info->tree_mod_log_lock);
725 btrfs_set_header_nritems(eb, n);
726}
727
728/*
729 * Called with eb read locked. If the buffer cannot be rewound, the same buffer
730 * is returned. If rewind operations happen, a fresh buffer is returned. The
731 * returned buffer is always read-locked. If the returned buffer is not the
732 * input buffer, the lock on the input buffer is released and the input buffer
733 * is freed (its refcount is decremented).
734 */
735struct extent_buffer *btrfs_tree_mod_log_rewind(struct btrfs_fs_info *fs_info,
736 struct btrfs_path *path,
737 struct extent_buffer *eb,
738 u64 time_seq)
739{
740 struct extent_buffer *eb_rewin;
741 struct tree_mod_elem *tm;
742
743 if (!time_seq)
744 return eb;
745
746 if (btrfs_header_level(eb) == 0)
747 return eb;
748
749 tm = tree_mod_log_search(fs_info, eb->start, time_seq);
750 if (!tm)
751 return eb;
752
753 if (tm->op == BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING) {
754 BUG_ON(tm->slot != 0);
755 eb_rewin = alloc_dummy_extent_buffer(fs_info, eb->start);
756 if (!eb_rewin) {
757 btrfs_tree_read_unlock(eb);
758 free_extent_buffer(eb);
759 return NULL;
760 }
761 btrfs_set_header_bytenr(eb_rewin, eb->start);
762 btrfs_set_header_backref_rev(eb_rewin,
763 btrfs_header_backref_rev(eb));
764 btrfs_set_header_owner(eb_rewin, btrfs_header_owner(eb));
765 btrfs_set_header_level(eb_rewin, btrfs_header_level(eb));
766 } else {
767 eb_rewin = btrfs_clone_extent_buffer(eb);
768 if (!eb_rewin) {
769 btrfs_tree_read_unlock(eb);
770 free_extent_buffer(eb);
771 return NULL;
772 }
773 }
774
775 btrfs_tree_read_unlock(eb);
776 free_extent_buffer(eb);
777
778 btrfs_set_buffer_lockdep_class(btrfs_header_owner(eb_rewin),
779 eb_rewin, btrfs_header_level(eb_rewin));
780 btrfs_tree_read_lock(eb_rewin);
781 tree_mod_log_rewind(fs_info, eb_rewin, time_seq, tm);
782 WARN_ON(btrfs_header_nritems(eb_rewin) >
783 BTRFS_NODEPTRS_PER_BLOCK(fs_info));
784
785 return eb_rewin;
786}
787
788/*
789 * Rewind the state of @root's root node to the given @time_seq value.
790 * If there are no changes, the current root->root_node is returned. If anything
791 * changed in between, there's a fresh buffer allocated on which the rewind
792 * operations are done. In any case, the returned buffer is read locked.
793 * Returns NULL on error (with no locks held).
794 */
795struct extent_buffer *btrfs_get_old_root(struct btrfs_root *root, u64 time_seq)
796{
797 struct btrfs_fs_info *fs_info = root->fs_info;
798 struct tree_mod_elem *tm;
799 struct extent_buffer *eb = NULL;
800 struct extent_buffer *eb_root;
801 u64 eb_root_owner = 0;
802 struct extent_buffer *old;
803 struct tree_mod_root *old_root = NULL;
804 u64 old_generation = 0;
805 u64 logical;
806 int level;
807
808 eb_root = btrfs_read_lock_root_node(root);
809 tm = tree_mod_log_oldest_root(eb_root, time_seq);
810 if (!tm)
811 return eb_root;
812
813 if (tm->op == BTRFS_MOD_LOG_ROOT_REPLACE) {
814 old_root = &tm->old_root;
815 old_generation = tm->generation;
816 logical = old_root->logical;
817 level = old_root->level;
818 } else {
819 logical = eb_root->start;
820 level = btrfs_header_level(eb_root);
821 }
822
823 tm = tree_mod_log_search(fs_info, logical, time_seq);
824 if (old_root && tm && tm->op != BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING) {
825 struct btrfs_tree_parent_check check = { 0 };
826
827 btrfs_tree_read_unlock(eb_root);
828 free_extent_buffer(eb_root);
829
830 check.level = level;
831 check.owner_root = root->root_key.objectid;
832
833 old = read_tree_block(fs_info, logical, &check);
834 if (WARN_ON(IS_ERR(old) || !extent_buffer_uptodate(old))) {
835 if (!IS_ERR(old))
836 free_extent_buffer(old);
837 btrfs_warn(fs_info,
838 "failed to read tree block %llu from get_old_root",
839 logical);
840 } else {
841 struct tree_mod_elem *tm2;
842
843 btrfs_tree_read_lock(old);
844 eb = btrfs_clone_extent_buffer(old);
845 /*
846 * After the lookup for the most recent tree mod operation
847 * above and before we locked and cloned the extent buffer
848 * 'old', a new tree mod log operation may have been added.
849 * So lookup for a more recent one to make sure the number
850 * of mod log operations we replay is consistent with the
851 * number of items we have in the cloned extent buffer,
852 * otherwise we can hit a BUG_ON when rewinding the extent
853 * buffer.
854 */
855 tm2 = tree_mod_log_search(fs_info, logical, time_seq);
856 btrfs_tree_read_unlock(old);
857 free_extent_buffer(old);
858 ASSERT(tm2);
859 ASSERT(tm2 == tm || tm2->seq > tm->seq);
860 if (!tm2 || tm2->seq < tm->seq) {
861 free_extent_buffer(eb);
862 return NULL;
863 }
864 tm = tm2;
865 }
866 } else if (old_root) {
867 eb_root_owner = btrfs_header_owner(eb_root);
868 btrfs_tree_read_unlock(eb_root);
869 free_extent_buffer(eb_root);
870 eb = alloc_dummy_extent_buffer(fs_info, logical);
871 } else {
872 eb = btrfs_clone_extent_buffer(eb_root);
873 btrfs_tree_read_unlock(eb_root);
874 free_extent_buffer(eb_root);
875 }
876
877 if (!eb)
878 return NULL;
879 if (old_root) {
880 btrfs_set_header_bytenr(eb, eb->start);
881 btrfs_set_header_backref_rev(eb, BTRFS_MIXED_BACKREF_REV);
882 btrfs_set_header_owner(eb, eb_root_owner);
883 btrfs_set_header_level(eb, old_root->level);
884 btrfs_set_header_generation(eb, old_generation);
885 }
886 btrfs_set_buffer_lockdep_class(btrfs_header_owner(eb), eb,
887 btrfs_header_level(eb));
888 btrfs_tree_read_lock(eb);
889 if (tm)
890 tree_mod_log_rewind(fs_info, eb, time_seq, tm);
891 else
892 WARN_ON(btrfs_header_level(eb) != 0);
893 WARN_ON(btrfs_header_nritems(eb) > BTRFS_NODEPTRS_PER_BLOCK(fs_info));
894
895 return eb;
896}
897
898int btrfs_old_root_level(struct btrfs_root *root, u64 time_seq)
899{
900 struct tree_mod_elem *tm;
901 int level;
902 struct extent_buffer *eb_root = btrfs_root_node(root);
903
904 tm = tree_mod_log_oldest_root(eb_root, time_seq);
905 if (tm && tm->op == BTRFS_MOD_LOG_ROOT_REPLACE)
906 level = tm->old_root.level;
907 else
908 level = btrfs_header_level(eb_root);
909
910 free_extent_buffer(eb_root);
911
912 return level;
913}
914
915/*
916 * Return the lowest sequence number in the tree modification log.
917 *
918 * Return the sequence number of the oldest tree modification log user, which
919 * corresponds to the lowest sequence number of all existing users. If there are
920 * no users it returns 0.
921 */
922u64 btrfs_tree_mod_log_lowest_seq(struct btrfs_fs_info *fs_info)
923{
924 u64 ret = 0;
925
926 read_lock(&fs_info->tree_mod_log_lock);
927 if (!list_empty(&fs_info->tree_mod_seq_list)) {
928 struct btrfs_seq_list *elem;
929
930 elem = list_first_entry(&fs_info->tree_mod_seq_list,
931 struct btrfs_seq_list, list);
932 ret = elem->seq;
933 }
934 read_unlock(&fs_info->tree_mod_log_lock);
935
936 return ret;
937}