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