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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2009 Oracle. All rights reserved.
4 */
5
6#include <linux/sched.h>
7#include <linux/slab.h>
8#include <linux/sort.h>
9#include "messages.h"
10#include "ctree.h"
11#include "delayed-ref.h"
12#include "transaction.h"
13#include "qgroup.h"
14#include "space-info.h"
15#include "tree-mod-log.h"
16#include "fs.h"
17
18struct kmem_cache *btrfs_delayed_ref_head_cachep;
19struct kmem_cache *btrfs_delayed_tree_ref_cachep;
20struct kmem_cache *btrfs_delayed_data_ref_cachep;
21struct kmem_cache *btrfs_delayed_extent_op_cachep;
22/*
23 * delayed back reference update tracking. For subvolume trees
24 * we queue up extent allocations and backref maintenance for
25 * delayed processing. This avoids deep call chains where we
26 * add extents in the middle of btrfs_search_slot, and it allows
27 * us to buffer up frequently modified backrefs in an rb tree instead
28 * of hammering updates on the extent allocation tree.
29 */
30
31bool btrfs_check_space_for_delayed_refs(struct btrfs_fs_info *fs_info)
32{
33 struct btrfs_block_rsv *delayed_refs_rsv = &fs_info->delayed_refs_rsv;
34 struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
35 bool ret = false;
36 u64 reserved;
37
38 spin_lock(&global_rsv->lock);
39 reserved = global_rsv->reserved;
40 spin_unlock(&global_rsv->lock);
41
42 /*
43 * Since the global reserve is just kind of magic we don't really want
44 * to rely on it to save our bacon, so if our size is more than the
45 * delayed_refs_rsv and the global rsv then it's time to think about
46 * bailing.
47 */
48 spin_lock(&delayed_refs_rsv->lock);
49 reserved += delayed_refs_rsv->reserved;
50 if (delayed_refs_rsv->size >= reserved)
51 ret = true;
52 spin_unlock(&delayed_refs_rsv->lock);
53 return ret;
54}
55
56/*
57 * Release a ref head's reservation.
58 *
59 * @fs_info: the filesystem
60 * @nr_refs: number of delayed refs to drop
61 * @nr_csums: number of csum items to drop
62 *
63 * Drops the delayed ref head's count from the delayed refs rsv and free any
64 * excess reservation we had.
65 */
66void btrfs_delayed_refs_rsv_release(struct btrfs_fs_info *fs_info, int nr_refs, int nr_csums)
67{
68 struct btrfs_block_rsv *block_rsv = &fs_info->delayed_refs_rsv;
69 u64 num_bytes;
70 u64 released;
71
72 num_bytes = btrfs_calc_delayed_ref_bytes(fs_info, nr_refs);
73 num_bytes += btrfs_calc_delayed_ref_csum_bytes(fs_info, nr_csums);
74
75 released = btrfs_block_rsv_release(fs_info, block_rsv, num_bytes, NULL);
76 if (released)
77 trace_btrfs_space_reservation(fs_info, "delayed_refs_rsv",
78 0, released, 0);
79}
80
81/*
82 * Adjust the size of the delayed refs rsv.
83 *
84 * This is to be called anytime we may have adjusted trans->delayed_ref_updates
85 * or trans->delayed_ref_csum_deletions, it'll calculate the additional size and
86 * add it to the delayed_refs_rsv.
87 */
88void btrfs_update_delayed_refs_rsv(struct btrfs_trans_handle *trans)
89{
90 struct btrfs_fs_info *fs_info = trans->fs_info;
91 struct btrfs_block_rsv *delayed_rsv = &fs_info->delayed_refs_rsv;
92 struct btrfs_block_rsv *local_rsv = &trans->delayed_rsv;
93 u64 num_bytes;
94 u64 reserved_bytes;
95
96 num_bytes = btrfs_calc_delayed_ref_bytes(fs_info, trans->delayed_ref_updates);
97 num_bytes += btrfs_calc_delayed_ref_csum_bytes(fs_info,
98 trans->delayed_ref_csum_deletions);
99
100 if (num_bytes == 0)
101 return;
102
103 /*
104 * Try to take num_bytes from the transaction's local delayed reserve.
105 * If not possible, try to take as much as it's available. If the local
106 * reserve doesn't have enough reserved space, the delayed refs reserve
107 * will be refilled next time btrfs_delayed_refs_rsv_refill() is called
108 * by someone or if a transaction commit is triggered before that, the
109 * global block reserve will be used. We want to minimize using the
110 * global block reserve for cases we can account for in advance, to
111 * avoid exhausting it and reach -ENOSPC during a transaction commit.
112 */
113 spin_lock(&local_rsv->lock);
114 reserved_bytes = min(num_bytes, local_rsv->reserved);
115 local_rsv->reserved -= reserved_bytes;
116 local_rsv->full = (local_rsv->reserved >= local_rsv->size);
117 spin_unlock(&local_rsv->lock);
118
119 spin_lock(&delayed_rsv->lock);
120 delayed_rsv->size += num_bytes;
121 delayed_rsv->reserved += reserved_bytes;
122 delayed_rsv->full = (delayed_rsv->reserved >= delayed_rsv->size);
123 spin_unlock(&delayed_rsv->lock);
124 trans->delayed_ref_updates = 0;
125 trans->delayed_ref_csum_deletions = 0;
126}
127
128/*
129 * Adjust the size of the delayed refs block reserve for 1 block group item
130 * insertion, used after allocating a block group.
131 */
132void btrfs_inc_delayed_refs_rsv_bg_inserts(struct btrfs_fs_info *fs_info)
133{
134 struct btrfs_block_rsv *delayed_rsv = &fs_info->delayed_refs_rsv;
135
136 spin_lock(&delayed_rsv->lock);
137 /*
138 * Inserting a block group item does not require changing the free space
139 * tree, only the extent tree or the block group tree, so this is all we
140 * need.
141 */
142 delayed_rsv->size += btrfs_calc_insert_metadata_size(fs_info, 1);
143 delayed_rsv->full = false;
144 spin_unlock(&delayed_rsv->lock);
145}
146
147/*
148 * Adjust the size of the delayed refs block reserve to release space for 1
149 * block group item insertion.
150 */
151void btrfs_dec_delayed_refs_rsv_bg_inserts(struct btrfs_fs_info *fs_info)
152{
153 struct btrfs_block_rsv *delayed_rsv = &fs_info->delayed_refs_rsv;
154 const u64 num_bytes = btrfs_calc_insert_metadata_size(fs_info, 1);
155 u64 released;
156
157 released = btrfs_block_rsv_release(fs_info, delayed_rsv, num_bytes, NULL);
158 if (released > 0)
159 trace_btrfs_space_reservation(fs_info, "delayed_refs_rsv",
160 0, released, 0);
161}
162
163/*
164 * Adjust the size of the delayed refs block reserve for 1 block group item
165 * update.
166 */
167void btrfs_inc_delayed_refs_rsv_bg_updates(struct btrfs_fs_info *fs_info)
168{
169 struct btrfs_block_rsv *delayed_rsv = &fs_info->delayed_refs_rsv;
170
171 spin_lock(&delayed_rsv->lock);
172 /*
173 * Updating a block group item does not result in new nodes/leaves and
174 * does not require changing the free space tree, only the extent tree
175 * or the block group tree, so this is all we need.
176 */
177 delayed_rsv->size += btrfs_calc_metadata_size(fs_info, 1);
178 delayed_rsv->full = false;
179 spin_unlock(&delayed_rsv->lock);
180}
181
182/*
183 * Adjust the size of the delayed refs block reserve to release space for 1
184 * block group item update.
185 */
186void btrfs_dec_delayed_refs_rsv_bg_updates(struct btrfs_fs_info *fs_info)
187{
188 struct btrfs_block_rsv *delayed_rsv = &fs_info->delayed_refs_rsv;
189 const u64 num_bytes = btrfs_calc_metadata_size(fs_info, 1);
190 u64 released;
191
192 released = btrfs_block_rsv_release(fs_info, delayed_rsv, num_bytes, NULL);
193 if (released > 0)
194 trace_btrfs_space_reservation(fs_info, "delayed_refs_rsv",
195 0, released, 0);
196}
197
198/*
199 * Transfer bytes to our delayed refs rsv.
200 *
201 * @fs_info: the filesystem
202 * @num_bytes: number of bytes to transfer
203 *
204 * This transfers up to the num_bytes amount, previously reserved, to the
205 * delayed_refs_rsv. Any extra bytes are returned to the space info.
206 */
207void btrfs_migrate_to_delayed_refs_rsv(struct btrfs_fs_info *fs_info,
208 u64 num_bytes)
209{
210 struct btrfs_block_rsv *delayed_refs_rsv = &fs_info->delayed_refs_rsv;
211 u64 to_free = 0;
212
213 spin_lock(&delayed_refs_rsv->lock);
214 if (delayed_refs_rsv->size > delayed_refs_rsv->reserved) {
215 u64 delta = delayed_refs_rsv->size -
216 delayed_refs_rsv->reserved;
217 if (num_bytes > delta) {
218 to_free = num_bytes - delta;
219 num_bytes = delta;
220 }
221 } else {
222 to_free = num_bytes;
223 num_bytes = 0;
224 }
225
226 if (num_bytes)
227 delayed_refs_rsv->reserved += num_bytes;
228 if (delayed_refs_rsv->reserved >= delayed_refs_rsv->size)
229 delayed_refs_rsv->full = true;
230 spin_unlock(&delayed_refs_rsv->lock);
231
232 if (num_bytes)
233 trace_btrfs_space_reservation(fs_info, "delayed_refs_rsv",
234 0, num_bytes, 1);
235 if (to_free)
236 btrfs_space_info_free_bytes_may_use(fs_info,
237 delayed_refs_rsv->space_info, to_free);
238}
239
240/*
241 * Refill based on our delayed refs usage.
242 *
243 * @fs_info: the filesystem
244 * @flush: control how we can flush for this reservation.
245 *
246 * This will refill the delayed block_rsv up to 1 items size worth of space and
247 * will return -ENOSPC if we can't make the reservation.
248 */
249int btrfs_delayed_refs_rsv_refill(struct btrfs_fs_info *fs_info,
250 enum btrfs_reserve_flush_enum flush)
251{
252 struct btrfs_block_rsv *block_rsv = &fs_info->delayed_refs_rsv;
253 struct btrfs_space_info *space_info = block_rsv->space_info;
254 u64 limit = btrfs_calc_delayed_ref_bytes(fs_info, 1);
255 u64 num_bytes = 0;
256 u64 refilled_bytes;
257 u64 to_free;
258 int ret = -ENOSPC;
259
260 spin_lock(&block_rsv->lock);
261 if (block_rsv->reserved < block_rsv->size) {
262 num_bytes = block_rsv->size - block_rsv->reserved;
263 num_bytes = min(num_bytes, limit);
264 }
265 spin_unlock(&block_rsv->lock);
266
267 if (!num_bytes)
268 return 0;
269
270 ret = btrfs_reserve_metadata_bytes(fs_info, space_info, num_bytes, flush);
271 if (ret)
272 return ret;
273
274 /*
275 * We may have raced with someone else, so check again if we the block
276 * reserve is still not full and release any excess space.
277 */
278 spin_lock(&block_rsv->lock);
279 if (block_rsv->reserved < block_rsv->size) {
280 u64 needed = block_rsv->size - block_rsv->reserved;
281
282 if (num_bytes >= needed) {
283 block_rsv->reserved += needed;
284 block_rsv->full = true;
285 to_free = num_bytes - needed;
286 refilled_bytes = needed;
287 } else {
288 block_rsv->reserved += num_bytes;
289 to_free = 0;
290 refilled_bytes = num_bytes;
291 }
292 } else {
293 to_free = num_bytes;
294 refilled_bytes = 0;
295 }
296 spin_unlock(&block_rsv->lock);
297
298 if (to_free > 0)
299 btrfs_space_info_free_bytes_may_use(fs_info, space_info, to_free);
300
301 if (refilled_bytes > 0)
302 trace_btrfs_space_reservation(fs_info, "delayed_refs_rsv", 0,
303 refilled_bytes, 1);
304 return 0;
305}
306
307/*
308 * compare two delayed tree backrefs with same bytenr and type
309 */
310static int comp_tree_refs(struct btrfs_delayed_tree_ref *ref1,
311 struct btrfs_delayed_tree_ref *ref2)
312{
313 if (ref1->node.type == BTRFS_TREE_BLOCK_REF_KEY) {
314 if (ref1->root < ref2->root)
315 return -1;
316 if (ref1->root > ref2->root)
317 return 1;
318 } else {
319 if (ref1->parent < ref2->parent)
320 return -1;
321 if (ref1->parent > ref2->parent)
322 return 1;
323 }
324 return 0;
325}
326
327/*
328 * compare two delayed data backrefs with same bytenr and type
329 */
330static int comp_data_refs(struct btrfs_delayed_data_ref *ref1,
331 struct btrfs_delayed_data_ref *ref2)
332{
333 if (ref1->node.type == BTRFS_EXTENT_DATA_REF_KEY) {
334 if (ref1->root < ref2->root)
335 return -1;
336 if (ref1->root > ref2->root)
337 return 1;
338 if (ref1->objectid < ref2->objectid)
339 return -1;
340 if (ref1->objectid > ref2->objectid)
341 return 1;
342 if (ref1->offset < ref2->offset)
343 return -1;
344 if (ref1->offset > ref2->offset)
345 return 1;
346 } else {
347 if (ref1->parent < ref2->parent)
348 return -1;
349 if (ref1->parent > ref2->parent)
350 return 1;
351 }
352 return 0;
353}
354
355static int comp_refs(struct btrfs_delayed_ref_node *ref1,
356 struct btrfs_delayed_ref_node *ref2,
357 bool check_seq)
358{
359 int ret = 0;
360
361 if (ref1->type < ref2->type)
362 return -1;
363 if (ref1->type > ref2->type)
364 return 1;
365 if (ref1->type == BTRFS_TREE_BLOCK_REF_KEY ||
366 ref1->type == BTRFS_SHARED_BLOCK_REF_KEY)
367 ret = comp_tree_refs(btrfs_delayed_node_to_tree_ref(ref1),
368 btrfs_delayed_node_to_tree_ref(ref2));
369 else
370 ret = comp_data_refs(btrfs_delayed_node_to_data_ref(ref1),
371 btrfs_delayed_node_to_data_ref(ref2));
372 if (ret)
373 return ret;
374 if (check_seq) {
375 if (ref1->seq < ref2->seq)
376 return -1;
377 if (ref1->seq > ref2->seq)
378 return 1;
379 }
380 return 0;
381}
382
383/* insert a new ref to head ref rbtree */
384static struct btrfs_delayed_ref_head *htree_insert(struct rb_root_cached *root,
385 struct rb_node *node)
386{
387 struct rb_node **p = &root->rb_root.rb_node;
388 struct rb_node *parent_node = NULL;
389 struct btrfs_delayed_ref_head *entry;
390 struct btrfs_delayed_ref_head *ins;
391 u64 bytenr;
392 bool leftmost = true;
393
394 ins = rb_entry(node, struct btrfs_delayed_ref_head, href_node);
395 bytenr = ins->bytenr;
396 while (*p) {
397 parent_node = *p;
398 entry = rb_entry(parent_node, struct btrfs_delayed_ref_head,
399 href_node);
400
401 if (bytenr < entry->bytenr) {
402 p = &(*p)->rb_left;
403 } else if (bytenr > entry->bytenr) {
404 p = &(*p)->rb_right;
405 leftmost = false;
406 } else {
407 return entry;
408 }
409 }
410
411 rb_link_node(node, parent_node, p);
412 rb_insert_color_cached(node, root, leftmost);
413 return NULL;
414}
415
416static struct btrfs_delayed_ref_node* tree_insert(struct rb_root_cached *root,
417 struct btrfs_delayed_ref_node *ins)
418{
419 struct rb_node **p = &root->rb_root.rb_node;
420 struct rb_node *node = &ins->ref_node;
421 struct rb_node *parent_node = NULL;
422 struct btrfs_delayed_ref_node *entry;
423 bool leftmost = true;
424
425 while (*p) {
426 int comp;
427
428 parent_node = *p;
429 entry = rb_entry(parent_node, struct btrfs_delayed_ref_node,
430 ref_node);
431 comp = comp_refs(ins, entry, true);
432 if (comp < 0) {
433 p = &(*p)->rb_left;
434 } else if (comp > 0) {
435 p = &(*p)->rb_right;
436 leftmost = false;
437 } else {
438 return entry;
439 }
440 }
441
442 rb_link_node(node, parent_node, p);
443 rb_insert_color_cached(node, root, leftmost);
444 return NULL;
445}
446
447static struct btrfs_delayed_ref_head *find_first_ref_head(
448 struct btrfs_delayed_ref_root *dr)
449{
450 struct rb_node *n;
451 struct btrfs_delayed_ref_head *entry;
452
453 n = rb_first_cached(&dr->href_root);
454 if (!n)
455 return NULL;
456
457 entry = rb_entry(n, struct btrfs_delayed_ref_head, href_node);
458
459 return entry;
460}
461
462/*
463 * Find a head entry based on bytenr. This returns the delayed ref head if it
464 * was able to find one, or NULL if nothing was in that spot. If return_bigger
465 * is given, the next bigger entry is returned if no exact match is found.
466 */
467static struct btrfs_delayed_ref_head *find_ref_head(
468 struct btrfs_delayed_ref_root *dr, u64 bytenr,
469 bool return_bigger)
470{
471 struct rb_root *root = &dr->href_root.rb_root;
472 struct rb_node *n;
473 struct btrfs_delayed_ref_head *entry;
474
475 n = root->rb_node;
476 entry = NULL;
477 while (n) {
478 entry = rb_entry(n, struct btrfs_delayed_ref_head, href_node);
479
480 if (bytenr < entry->bytenr)
481 n = n->rb_left;
482 else if (bytenr > entry->bytenr)
483 n = n->rb_right;
484 else
485 return entry;
486 }
487 if (entry && return_bigger) {
488 if (bytenr > entry->bytenr) {
489 n = rb_next(&entry->href_node);
490 if (!n)
491 return NULL;
492 entry = rb_entry(n, struct btrfs_delayed_ref_head,
493 href_node);
494 }
495 return entry;
496 }
497 return NULL;
498}
499
500int btrfs_delayed_ref_lock(struct btrfs_delayed_ref_root *delayed_refs,
501 struct btrfs_delayed_ref_head *head)
502{
503 lockdep_assert_held(&delayed_refs->lock);
504 if (mutex_trylock(&head->mutex))
505 return 0;
506
507 refcount_inc(&head->refs);
508 spin_unlock(&delayed_refs->lock);
509
510 mutex_lock(&head->mutex);
511 spin_lock(&delayed_refs->lock);
512 if (RB_EMPTY_NODE(&head->href_node)) {
513 mutex_unlock(&head->mutex);
514 btrfs_put_delayed_ref_head(head);
515 return -EAGAIN;
516 }
517 btrfs_put_delayed_ref_head(head);
518 return 0;
519}
520
521static inline void drop_delayed_ref(struct btrfs_fs_info *fs_info,
522 struct btrfs_delayed_ref_root *delayed_refs,
523 struct btrfs_delayed_ref_head *head,
524 struct btrfs_delayed_ref_node *ref)
525{
526 lockdep_assert_held(&head->lock);
527 rb_erase_cached(&ref->ref_node, &head->ref_tree);
528 RB_CLEAR_NODE(&ref->ref_node);
529 if (!list_empty(&ref->add_list))
530 list_del(&ref->add_list);
531 btrfs_put_delayed_ref(ref);
532 atomic_dec(&delayed_refs->num_entries);
533 btrfs_delayed_refs_rsv_release(fs_info, 1, 0);
534}
535
536static bool merge_ref(struct btrfs_fs_info *fs_info,
537 struct btrfs_delayed_ref_root *delayed_refs,
538 struct btrfs_delayed_ref_head *head,
539 struct btrfs_delayed_ref_node *ref,
540 u64 seq)
541{
542 struct btrfs_delayed_ref_node *next;
543 struct rb_node *node = rb_next(&ref->ref_node);
544 bool done = false;
545
546 while (!done && node) {
547 int mod;
548
549 next = rb_entry(node, struct btrfs_delayed_ref_node, ref_node);
550 node = rb_next(node);
551 if (seq && next->seq >= seq)
552 break;
553 if (comp_refs(ref, next, false))
554 break;
555
556 if (ref->action == next->action) {
557 mod = next->ref_mod;
558 } else {
559 if (ref->ref_mod < next->ref_mod) {
560 swap(ref, next);
561 done = true;
562 }
563 mod = -next->ref_mod;
564 }
565
566 drop_delayed_ref(fs_info, delayed_refs, head, next);
567 ref->ref_mod += mod;
568 if (ref->ref_mod == 0) {
569 drop_delayed_ref(fs_info, delayed_refs, head, ref);
570 done = true;
571 } else {
572 /*
573 * Can't have multiples of the same ref on a tree block.
574 */
575 WARN_ON(ref->type == BTRFS_TREE_BLOCK_REF_KEY ||
576 ref->type == BTRFS_SHARED_BLOCK_REF_KEY);
577 }
578 }
579
580 return done;
581}
582
583void btrfs_merge_delayed_refs(struct btrfs_fs_info *fs_info,
584 struct btrfs_delayed_ref_root *delayed_refs,
585 struct btrfs_delayed_ref_head *head)
586{
587 struct btrfs_delayed_ref_node *ref;
588 struct rb_node *node;
589 u64 seq = 0;
590
591 lockdep_assert_held(&head->lock);
592
593 if (RB_EMPTY_ROOT(&head->ref_tree.rb_root))
594 return;
595
596 /* We don't have too many refs to merge for data. */
597 if (head->is_data)
598 return;
599
600 seq = btrfs_tree_mod_log_lowest_seq(fs_info);
601again:
602 for (node = rb_first_cached(&head->ref_tree); node;
603 node = rb_next(node)) {
604 ref = rb_entry(node, struct btrfs_delayed_ref_node, ref_node);
605 if (seq && ref->seq >= seq)
606 continue;
607 if (merge_ref(fs_info, delayed_refs, head, ref, seq))
608 goto again;
609 }
610}
611
612int btrfs_check_delayed_seq(struct btrfs_fs_info *fs_info, u64 seq)
613{
614 int ret = 0;
615 u64 min_seq = btrfs_tree_mod_log_lowest_seq(fs_info);
616
617 if (min_seq != 0 && seq >= min_seq) {
618 btrfs_debug(fs_info,
619 "holding back delayed_ref %llu, lowest is %llu",
620 seq, min_seq);
621 ret = 1;
622 }
623
624 return ret;
625}
626
627struct btrfs_delayed_ref_head *btrfs_select_ref_head(
628 struct btrfs_delayed_ref_root *delayed_refs)
629{
630 struct btrfs_delayed_ref_head *head;
631
632 lockdep_assert_held(&delayed_refs->lock);
633again:
634 head = find_ref_head(delayed_refs, delayed_refs->run_delayed_start,
635 true);
636 if (!head && delayed_refs->run_delayed_start != 0) {
637 delayed_refs->run_delayed_start = 0;
638 head = find_first_ref_head(delayed_refs);
639 }
640 if (!head)
641 return NULL;
642
643 while (head->processing) {
644 struct rb_node *node;
645
646 node = rb_next(&head->href_node);
647 if (!node) {
648 if (delayed_refs->run_delayed_start == 0)
649 return NULL;
650 delayed_refs->run_delayed_start = 0;
651 goto again;
652 }
653 head = rb_entry(node, struct btrfs_delayed_ref_head,
654 href_node);
655 }
656
657 head->processing = true;
658 WARN_ON(delayed_refs->num_heads_ready == 0);
659 delayed_refs->num_heads_ready--;
660 delayed_refs->run_delayed_start = head->bytenr +
661 head->num_bytes;
662 return head;
663}
664
665void btrfs_delete_ref_head(struct btrfs_delayed_ref_root *delayed_refs,
666 struct btrfs_delayed_ref_head *head)
667{
668 lockdep_assert_held(&delayed_refs->lock);
669 lockdep_assert_held(&head->lock);
670
671 rb_erase_cached(&head->href_node, &delayed_refs->href_root);
672 RB_CLEAR_NODE(&head->href_node);
673 atomic_dec(&delayed_refs->num_entries);
674 delayed_refs->num_heads--;
675 if (!head->processing)
676 delayed_refs->num_heads_ready--;
677}
678
679/*
680 * Helper to insert the ref_node to the tail or merge with tail.
681 *
682 * Return false if the ref was inserted.
683 * Return true if the ref was merged into an existing one (and therefore can be
684 * freed by the caller).
685 */
686static bool insert_delayed_ref(struct btrfs_trans_handle *trans,
687 struct btrfs_delayed_ref_head *href,
688 struct btrfs_delayed_ref_node *ref)
689{
690 struct btrfs_delayed_ref_root *root = &trans->transaction->delayed_refs;
691 struct btrfs_delayed_ref_node *exist;
692 int mod;
693
694 spin_lock(&href->lock);
695 exist = tree_insert(&href->ref_tree, ref);
696 if (!exist) {
697 if (ref->action == BTRFS_ADD_DELAYED_REF)
698 list_add_tail(&ref->add_list, &href->ref_add_list);
699 atomic_inc(&root->num_entries);
700 spin_unlock(&href->lock);
701 trans->delayed_ref_updates++;
702 return false;
703 }
704
705 /* Now we are sure we can merge */
706 if (exist->action == ref->action) {
707 mod = ref->ref_mod;
708 } else {
709 /* Need to change action */
710 if (exist->ref_mod < ref->ref_mod) {
711 exist->action = ref->action;
712 mod = -exist->ref_mod;
713 exist->ref_mod = ref->ref_mod;
714 if (ref->action == BTRFS_ADD_DELAYED_REF)
715 list_add_tail(&exist->add_list,
716 &href->ref_add_list);
717 else if (ref->action == BTRFS_DROP_DELAYED_REF) {
718 ASSERT(!list_empty(&exist->add_list));
719 list_del(&exist->add_list);
720 } else {
721 ASSERT(0);
722 }
723 } else
724 mod = -ref->ref_mod;
725 }
726 exist->ref_mod += mod;
727
728 /* remove existing tail if its ref_mod is zero */
729 if (exist->ref_mod == 0)
730 drop_delayed_ref(trans->fs_info, root, href, exist);
731 spin_unlock(&href->lock);
732 return true;
733}
734
735/*
736 * helper function to update the accounting in the head ref
737 * existing and update must have the same bytenr
738 */
739static noinline void update_existing_head_ref(struct btrfs_trans_handle *trans,
740 struct btrfs_delayed_ref_head *existing,
741 struct btrfs_delayed_ref_head *update)
742{
743 struct btrfs_delayed_ref_root *delayed_refs =
744 &trans->transaction->delayed_refs;
745 struct btrfs_fs_info *fs_info = trans->fs_info;
746 int old_ref_mod;
747
748 BUG_ON(existing->is_data != update->is_data);
749
750 spin_lock(&existing->lock);
751
752 /*
753 * When freeing an extent, we may not know the owning root when we
754 * first create the head_ref. However, some deref before the last deref
755 * will know it, so we just need to update the head_ref accordingly.
756 */
757 if (!existing->owning_root)
758 existing->owning_root = update->owning_root;
759
760 if (update->must_insert_reserved) {
761 /* if the extent was freed and then
762 * reallocated before the delayed ref
763 * entries were processed, we can end up
764 * with an existing head ref without
765 * the must_insert_reserved flag set.
766 * Set it again here
767 */
768 existing->must_insert_reserved = update->must_insert_reserved;
769 existing->owning_root = update->owning_root;
770
771 /*
772 * update the num_bytes so we make sure the accounting
773 * is done correctly
774 */
775 existing->num_bytes = update->num_bytes;
776
777 }
778
779 if (update->extent_op) {
780 if (!existing->extent_op) {
781 existing->extent_op = update->extent_op;
782 } else {
783 if (update->extent_op->update_key) {
784 memcpy(&existing->extent_op->key,
785 &update->extent_op->key,
786 sizeof(update->extent_op->key));
787 existing->extent_op->update_key = true;
788 }
789 if (update->extent_op->update_flags) {
790 existing->extent_op->flags_to_set |=
791 update->extent_op->flags_to_set;
792 existing->extent_op->update_flags = true;
793 }
794 btrfs_free_delayed_extent_op(update->extent_op);
795 }
796 }
797 /*
798 * update the reference mod on the head to reflect this new operation,
799 * only need the lock for this case cause we could be processing it
800 * currently, for refs we just added we know we're a-ok.
801 */
802 old_ref_mod = existing->total_ref_mod;
803 existing->ref_mod += update->ref_mod;
804 existing->total_ref_mod += update->ref_mod;
805
806 /*
807 * If we are going to from a positive ref mod to a negative or vice
808 * versa we need to make sure to adjust pending_csums accordingly.
809 * We reserve bytes for csum deletion when adding or updating a ref head
810 * see add_delayed_ref_head() for more details.
811 */
812 if (existing->is_data) {
813 u64 csum_leaves =
814 btrfs_csum_bytes_to_leaves(fs_info,
815 existing->num_bytes);
816
817 if (existing->total_ref_mod >= 0 && old_ref_mod < 0) {
818 delayed_refs->pending_csums -= existing->num_bytes;
819 btrfs_delayed_refs_rsv_release(fs_info, 0, csum_leaves);
820 }
821 if (existing->total_ref_mod < 0 && old_ref_mod >= 0) {
822 delayed_refs->pending_csums += existing->num_bytes;
823 trans->delayed_ref_csum_deletions += csum_leaves;
824 }
825 }
826
827 spin_unlock(&existing->lock);
828}
829
830static void init_delayed_ref_head(struct btrfs_delayed_ref_head *head_ref,
831 struct btrfs_qgroup_extent_record *qrecord,
832 u64 bytenr, u64 num_bytes, u64 ref_root,
833 u64 reserved, int action, bool is_data,
834 bool is_system, u64 owning_root)
835{
836 int count_mod = 1;
837 bool must_insert_reserved = false;
838
839 /* If reserved is provided, it must be a data extent. */
840 BUG_ON(!is_data && reserved);
841
842 switch (action) {
843 case BTRFS_UPDATE_DELAYED_HEAD:
844 count_mod = 0;
845 break;
846 case BTRFS_DROP_DELAYED_REF:
847 /*
848 * The head node stores the sum of all the mods, so dropping a ref
849 * should drop the sum in the head node by one.
850 */
851 count_mod = -1;
852 break;
853 case BTRFS_ADD_DELAYED_EXTENT:
854 /*
855 * BTRFS_ADD_DELAYED_EXTENT means that we need to update the
856 * reserved accounting when the extent is finally added, or if a
857 * later modification deletes the delayed ref without ever
858 * inserting the extent into the extent allocation tree.
859 * ref->must_insert_reserved is the flag used to record that
860 * accounting mods are required.
861 *
862 * Once we record must_insert_reserved, switch the action to
863 * BTRFS_ADD_DELAYED_REF because other special casing is not
864 * required.
865 */
866 must_insert_reserved = true;
867 break;
868 }
869
870 refcount_set(&head_ref->refs, 1);
871 head_ref->bytenr = bytenr;
872 head_ref->num_bytes = num_bytes;
873 head_ref->ref_mod = count_mod;
874 head_ref->reserved_bytes = reserved;
875 head_ref->must_insert_reserved = must_insert_reserved;
876 head_ref->owning_root = owning_root;
877 head_ref->is_data = is_data;
878 head_ref->is_system = is_system;
879 head_ref->ref_tree = RB_ROOT_CACHED;
880 INIT_LIST_HEAD(&head_ref->ref_add_list);
881 RB_CLEAR_NODE(&head_ref->href_node);
882 head_ref->processing = false;
883 head_ref->total_ref_mod = count_mod;
884 spin_lock_init(&head_ref->lock);
885 mutex_init(&head_ref->mutex);
886
887 if (qrecord) {
888 if (ref_root && reserved) {
889 qrecord->data_rsv = reserved;
890 qrecord->data_rsv_refroot = ref_root;
891 }
892 qrecord->bytenr = bytenr;
893 qrecord->num_bytes = num_bytes;
894 qrecord->old_roots = NULL;
895 }
896}
897
898/*
899 * helper function to actually insert a head node into the rbtree.
900 * this does all the dirty work in terms of maintaining the correct
901 * overall modification count.
902 */
903static noinline struct btrfs_delayed_ref_head *
904add_delayed_ref_head(struct btrfs_trans_handle *trans,
905 struct btrfs_delayed_ref_head *head_ref,
906 struct btrfs_qgroup_extent_record *qrecord,
907 int action, bool *qrecord_inserted_ret)
908{
909 struct btrfs_delayed_ref_head *existing;
910 struct btrfs_delayed_ref_root *delayed_refs;
911 bool qrecord_inserted = false;
912
913 delayed_refs = &trans->transaction->delayed_refs;
914
915 /* Record qgroup extent info if provided */
916 if (qrecord) {
917 if (btrfs_qgroup_trace_extent_nolock(trans->fs_info,
918 delayed_refs, qrecord))
919 kfree(qrecord);
920 else
921 qrecord_inserted = true;
922 }
923
924 trace_add_delayed_ref_head(trans->fs_info, head_ref, action);
925
926 existing = htree_insert(&delayed_refs->href_root,
927 &head_ref->href_node);
928 if (existing) {
929 update_existing_head_ref(trans, existing, head_ref);
930 /*
931 * we've updated the existing ref, free the newly
932 * allocated ref
933 */
934 kmem_cache_free(btrfs_delayed_ref_head_cachep, head_ref);
935 head_ref = existing;
936 } else {
937 /*
938 * We reserve the amount of bytes needed to delete csums when
939 * adding the ref head and not when adding individual drop refs
940 * since the csum items are deleted only after running the last
941 * delayed drop ref (the data extent's ref count drops to 0).
942 */
943 if (head_ref->is_data && head_ref->ref_mod < 0) {
944 delayed_refs->pending_csums += head_ref->num_bytes;
945 trans->delayed_ref_csum_deletions +=
946 btrfs_csum_bytes_to_leaves(trans->fs_info,
947 head_ref->num_bytes);
948 }
949 delayed_refs->num_heads++;
950 delayed_refs->num_heads_ready++;
951 atomic_inc(&delayed_refs->num_entries);
952 }
953 if (qrecord_inserted_ret)
954 *qrecord_inserted_ret = qrecord_inserted;
955
956 return head_ref;
957}
958
959/*
960 * Initialize the structure which represents a modification to a an extent.
961 *
962 * @fs_info: Internal to the mounted filesystem mount structure.
963 *
964 * @ref: The structure which is going to be initialized.
965 *
966 * @bytenr: The logical address of the extent for which a modification is
967 * going to be recorded.
968 *
969 * @num_bytes: Size of the extent whose modification is being recorded.
970 *
971 * @ref_root: The id of the root where this modification has originated, this
972 * can be either one of the well-known metadata trees or the
973 * subvolume id which references this extent.
974 *
975 * @action: Can be one of BTRFS_ADD_DELAYED_REF/BTRFS_DROP_DELAYED_REF or
976 * BTRFS_ADD_DELAYED_EXTENT
977 *
978 * @ref_type: Holds the type of the extent which is being recorded, can be
979 * one of BTRFS_SHARED_BLOCK_REF_KEY/BTRFS_TREE_BLOCK_REF_KEY
980 * when recording a metadata extent or BTRFS_SHARED_DATA_REF_KEY/
981 * BTRFS_EXTENT_DATA_REF_KEY when recording data extent
982 */
983static void init_delayed_ref_common(struct btrfs_fs_info *fs_info,
984 struct btrfs_delayed_ref_node *ref,
985 u64 bytenr, u64 num_bytes, u64 ref_root,
986 int action, u8 ref_type)
987{
988 u64 seq = 0;
989
990 if (action == BTRFS_ADD_DELAYED_EXTENT)
991 action = BTRFS_ADD_DELAYED_REF;
992
993 if (is_fstree(ref_root))
994 seq = atomic64_read(&fs_info->tree_mod_seq);
995
996 refcount_set(&ref->refs, 1);
997 ref->bytenr = bytenr;
998 ref->num_bytes = num_bytes;
999 ref->ref_mod = 1;
1000 ref->action = action;
1001 ref->seq = seq;
1002 ref->type = ref_type;
1003 RB_CLEAR_NODE(&ref->ref_node);
1004 INIT_LIST_HEAD(&ref->add_list);
1005}
1006
1007/*
1008 * add a delayed tree ref. This does all of the accounting required
1009 * to make sure the delayed ref is eventually processed before this
1010 * transaction commits.
1011 */
1012int btrfs_add_delayed_tree_ref(struct btrfs_trans_handle *trans,
1013 struct btrfs_ref *generic_ref,
1014 struct btrfs_delayed_extent_op *extent_op)
1015{
1016 struct btrfs_fs_info *fs_info = trans->fs_info;
1017 struct btrfs_delayed_tree_ref *ref;
1018 struct btrfs_delayed_ref_head *head_ref;
1019 struct btrfs_delayed_ref_root *delayed_refs;
1020 struct btrfs_qgroup_extent_record *record = NULL;
1021 bool qrecord_inserted;
1022 bool is_system;
1023 bool merged;
1024 int action = generic_ref->action;
1025 int level = generic_ref->tree_ref.level;
1026 u64 bytenr = generic_ref->bytenr;
1027 u64 num_bytes = generic_ref->len;
1028 u64 parent = generic_ref->parent;
1029 u8 ref_type;
1030
1031 is_system = (generic_ref->tree_ref.ref_root == BTRFS_CHUNK_TREE_OBJECTID);
1032
1033 ASSERT(generic_ref->type == BTRFS_REF_METADATA && generic_ref->action);
1034 ref = kmem_cache_alloc(btrfs_delayed_tree_ref_cachep, GFP_NOFS);
1035 if (!ref)
1036 return -ENOMEM;
1037
1038 head_ref = kmem_cache_alloc(btrfs_delayed_ref_head_cachep, GFP_NOFS);
1039 if (!head_ref) {
1040 kmem_cache_free(btrfs_delayed_tree_ref_cachep, ref);
1041 return -ENOMEM;
1042 }
1043
1044 if (btrfs_qgroup_full_accounting(fs_info) && !generic_ref->skip_qgroup) {
1045 record = kzalloc(sizeof(*record), GFP_NOFS);
1046 if (!record) {
1047 kmem_cache_free(btrfs_delayed_tree_ref_cachep, ref);
1048 kmem_cache_free(btrfs_delayed_ref_head_cachep, head_ref);
1049 return -ENOMEM;
1050 }
1051 }
1052
1053 if (parent)
1054 ref_type = BTRFS_SHARED_BLOCK_REF_KEY;
1055 else
1056 ref_type = BTRFS_TREE_BLOCK_REF_KEY;
1057
1058 init_delayed_ref_common(fs_info, &ref->node, bytenr, num_bytes,
1059 generic_ref->tree_ref.ref_root, action,
1060 ref_type);
1061 ref->root = generic_ref->tree_ref.ref_root;
1062 ref->parent = parent;
1063 ref->level = level;
1064
1065 init_delayed_ref_head(head_ref, record, bytenr, num_bytes,
1066 generic_ref->tree_ref.ref_root, 0, action,
1067 false, is_system, generic_ref->owning_root);
1068 head_ref->extent_op = extent_op;
1069
1070 delayed_refs = &trans->transaction->delayed_refs;
1071 spin_lock(&delayed_refs->lock);
1072
1073 /*
1074 * insert both the head node and the new ref without dropping
1075 * the spin lock
1076 */
1077 head_ref = add_delayed_ref_head(trans, head_ref, record,
1078 action, &qrecord_inserted);
1079
1080 merged = insert_delayed_ref(trans, head_ref, &ref->node);
1081 spin_unlock(&delayed_refs->lock);
1082
1083 /*
1084 * Need to update the delayed_refs_rsv with any changes we may have
1085 * made.
1086 */
1087 btrfs_update_delayed_refs_rsv(trans);
1088
1089 trace_add_delayed_tree_ref(fs_info, &ref->node, ref,
1090 action == BTRFS_ADD_DELAYED_EXTENT ?
1091 BTRFS_ADD_DELAYED_REF : action);
1092 if (merged)
1093 kmem_cache_free(btrfs_delayed_tree_ref_cachep, ref);
1094
1095 if (qrecord_inserted)
1096 btrfs_qgroup_trace_extent_post(trans, record);
1097
1098 return 0;
1099}
1100
1101/*
1102 * add a delayed data ref. it's similar to btrfs_add_delayed_tree_ref.
1103 */
1104int btrfs_add_delayed_data_ref(struct btrfs_trans_handle *trans,
1105 struct btrfs_ref *generic_ref,
1106 u64 reserved)
1107{
1108 struct btrfs_fs_info *fs_info = trans->fs_info;
1109 struct btrfs_delayed_data_ref *ref;
1110 struct btrfs_delayed_ref_head *head_ref;
1111 struct btrfs_delayed_ref_root *delayed_refs;
1112 struct btrfs_qgroup_extent_record *record = NULL;
1113 bool qrecord_inserted;
1114 int action = generic_ref->action;
1115 bool merged;
1116 u64 bytenr = generic_ref->bytenr;
1117 u64 num_bytes = generic_ref->len;
1118 u64 parent = generic_ref->parent;
1119 u64 ref_root = generic_ref->data_ref.ref_root;
1120 u64 owner = generic_ref->data_ref.ino;
1121 u64 offset = generic_ref->data_ref.offset;
1122 u8 ref_type;
1123
1124 ASSERT(generic_ref->type == BTRFS_REF_DATA && action);
1125 ref = kmem_cache_alloc(btrfs_delayed_data_ref_cachep, GFP_NOFS);
1126 if (!ref)
1127 return -ENOMEM;
1128
1129 if (parent)
1130 ref_type = BTRFS_SHARED_DATA_REF_KEY;
1131 else
1132 ref_type = BTRFS_EXTENT_DATA_REF_KEY;
1133 init_delayed_ref_common(fs_info, &ref->node, bytenr, num_bytes,
1134 ref_root, action, ref_type);
1135 ref->root = ref_root;
1136 ref->parent = parent;
1137 ref->objectid = owner;
1138 ref->offset = offset;
1139
1140
1141 head_ref = kmem_cache_alloc(btrfs_delayed_ref_head_cachep, GFP_NOFS);
1142 if (!head_ref) {
1143 kmem_cache_free(btrfs_delayed_data_ref_cachep, ref);
1144 return -ENOMEM;
1145 }
1146
1147 if (btrfs_qgroup_full_accounting(fs_info) && !generic_ref->skip_qgroup) {
1148 record = kzalloc(sizeof(*record), GFP_NOFS);
1149 if (!record) {
1150 kmem_cache_free(btrfs_delayed_data_ref_cachep, ref);
1151 kmem_cache_free(btrfs_delayed_ref_head_cachep,
1152 head_ref);
1153 return -ENOMEM;
1154 }
1155 }
1156
1157 init_delayed_ref_head(head_ref, record, bytenr, num_bytes, ref_root,
1158 reserved, action, true, false, generic_ref->owning_root);
1159 head_ref->extent_op = NULL;
1160
1161 delayed_refs = &trans->transaction->delayed_refs;
1162 spin_lock(&delayed_refs->lock);
1163
1164 /*
1165 * insert both the head node and the new ref without dropping
1166 * the spin lock
1167 */
1168 head_ref = add_delayed_ref_head(trans, head_ref, record,
1169 action, &qrecord_inserted);
1170
1171 merged = insert_delayed_ref(trans, head_ref, &ref->node);
1172 spin_unlock(&delayed_refs->lock);
1173
1174 /*
1175 * Need to update the delayed_refs_rsv with any changes we may have
1176 * made.
1177 */
1178 btrfs_update_delayed_refs_rsv(trans);
1179
1180 trace_add_delayed_data_ref(trans->fs_info, &ref->node, ref,
1181 action == BTRFS_ADD_DELAYED_EXTENT ?
1182 BTRFS_ADD_DELAYED_REF : action);
1183 if (merged)
1184 kmem_cache_free(btrfs_delayed_data_ref_cachep, ref);
1185
1186
1187 if (qrecord_inserted)
1188 return btrfs_qgroup_trace_extent_post(trans, record);
1189 return 0;
1190}
1191
1192int btrfs_add_delayed_extent_op(struct btrfs_trans_handle *trans,
1193 u64 bytenr, u64 num_bytes,
1194 struct btrfs_delayed_extent_op *extent_op)
1195{
1196 struct btrfs_delayed_ref_head *head_ref;
1197 struct btrfs_delayed_ref_root *delayed_refs;
1198
1199 head_ref = kmem_cache_alloc(btrfs_delayed_ref_head_cachep, GFP_NOFS);
1200 if (!head_ref)
1201 return -ENOMEM;
1202
1203 init_delayed_ref_head(head_ref, NULL, bytenr, num_bytes, 0, 0,
1204 BTRFS_UPDATE_DELAYED_HEAD, false, false, 0);
1205 head_ref->extent_op = extent_op;
1206
1207 delayed_refs = &trans->transaction->delayed_refs;
1208 spin_lock(&delayed_refs->lock);
1209
1210 add_delayed_ref_head(trans, head_ref, NULL, BTRFS_UPDATE_DELAYED_HEAD,
1211 NULL);
1212
1213 spin_unlock(&delayed_refs->lock);
1214
1215 /*
1216 * Need to update the delayed_refs_rsv with any changes we may have
1217 * made.
1218 */
1219 btrfs_update_delayed_refs_rsv(trans);
1220 return 0;
1221}
1222
1223/*
1224 * This does a simple search for the head node for a given extent. Returns the
1225 * head node if found, or NULL if not.
1226 */
1227struct btrfs_delayed_ref_head *
1228btrfs_find_delayed_ref_head(struct btrfs_delayed_ref_root *delayed_refs, u64 bytenr)
1229{
1230 lockdep_assert_held(&delayed_refs->lock);
1231
1232 return find_ref_head(delayed_refs, bytenr, false);
1233}
1234
1235void __cold btrfs_delayed_ref_exit(void)
1236{
1237 kmem_cache_destroy(btrfs_delayed_ref_head_cachep);
1238 kmem_cache_destroy(btrfs_delayed_tree_ref_cachep);
1239 kmem_cache_destroy(btrfs_delayed_data_ref_cachep);
1240 kmem_cache_destroy(btrfs_delayed_extent_op_cachep);
1241}
1242
1243int __init btrfs_delayed_ref_init(void)
1244{
1245 btrfs_delayed_ref_head_cachep = kmem_cache_create(
1246 "btrfs_delayed_ref_head",
1247 sizeof(struct btrfs_delayed_ref_head), 0,
1248 SLAB_MEM_SPREAD, NULL);
1249 if (!btrfs_delayed_ref_head_cachep)
1250 goto fail;
1251
1252 btrfs_delayed_tree_ref_cachep = kmem_cache_create(
1253 "btrfs_delayed_tree_ref",
1254 sizeof(struct btrfs_delayed_tree_ref), 0,
1255 SLAB_MEM_SPREAD, NULL);
1256 if (!btrfs_delayed_tree_ref_cachep)
1257 goto fail;
1258
1259 btrfs_delayed_data_ref_cachep = kmem_cache_create(
1260 "btrfs_delayed_data_ref",
1261 sizeof(struct btrfs_delayed_data_ref), 0,
1262 SLAB_MEM_SPREAD, NULL);
1263 if (!btrfs_delayed_data_ref_cachep)
1264 goto fail;
1265
1266 btrfs_delayed_extent_op_cachep = kmem_cache_create(
1267 "btrfs_delayed_extent_op",
1268 sizeof(struct btrfs_delayed_extent_op), 0,
1269 SLAB_MEM_SPREAD, NULL);
1270 if (!btrfs_delayed_extent_op_cachep)
1271 goto fail;
1272
1273 return 0;
1274fail:
1275 btrfs_delayed_ref_exit();
1276 return -ENOMEM;
1277}
1/*
2 * Copyright (C) 2009 Oracle. All rights reserved.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public
6 * License v2 as published by the Free Software Foundation.
7 *
8 * This program is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
11 * General Public License for more details.
12 *
13 * You should have received a copy of the GNU General Public
14 * License along with this program; if not, write to the
15 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
16 * Boston, MA 021110-1307, USA.
17 */
18
19#include <linux/sched.h>
20#include <linux/slab.h>
21#include <linux/sort.h>
22#include "ctree.h"
23#include "delayed-ref.h"
24#include "transaction.h"
25
26/*
27 * delayed back reference update tracking. For subvolume trees
28 * we queue up extent allocations and backref maintenance for
29 * delayed processing. This avoids deep call chains where we
30 * add extents in the middle of btrfs_search_slot, and it allows
31 * us to buffer up frequently modified backrefs in an rb tree instead
32 * of hammering updates on the extent allocation tree.
33 */
34
35/*
36 * compare two delayed tree backrefs with same bytenr and type
37 */
38static int comp_tree_refs(struct btrfs_delayed_tree_ref *ref2,
39 struct btrfs_delayed_tree_ref *ref1)
40{
41 if (ref1->node.type == BTRFS_TREE_BLOCK_REF_KEY) {
42 if (ref1->root < ref2->root)
43 return -1;
44 if (ref1->root > ref2->root)
45 return 1;
46 } else {
47 if (ref1->parent < ref2->parent)
48 return -1;
49 if (ref1->parent > ref2->parent)
50 return 1;
51 }
52 return 0;
53}
54
55/*
56 * compare two delayed data backrefs with same bytenr and type
57 */
58static int comp_data_refs(struct btrfs_delayed_data_ref *ref2,
59 struct btrfs_delayed_data_ref *ref1)
60{
61 if (ref1->node.type == BTRFS_EXTENT_DATA_REF_KEY) {
62 if (ref1->root < ref2->root)
63 return -1;
64 if (ref1->root > ref2->root)
65 return 1;
66 if (ref1->objectid < ref2->objectid)
67 return -1;
68 if (ref1->objectid > ref2->objectid)
69 return 1;
70 if (ref1->offset < ref2->offset)
71 return -1;
72 if (ref1->offset > ref2->offset)
73 return 1;
74 } else {
75 if (ref1->parent < ref2->parent)
76 return -1;
77 if (ref1->parent > ref2->parent)
78 return 1;
79 }
80 return 0;
81}
82
83/*
84 * entries in the rb tree are ordered by the byte number of the extent,
85 * type of the delayed backrefs and content of delayed backrefs.
86 */
87static int comp_entry(struct btrfs_delayed_ref_node *ref2,
88 struct btrfs_delayed_ref_node *ref1)
89{
90 if (ref1->bytenr < ref2->bytenr)
91 return -1;
92 if (ref1->bytenr > ref2->bytenr)
93 return 1;
94 if (ref1->is_head && ref2->is_head)
95 return 0;
96 if (ref2->is_head)
97 return -1;
98 if (ref1->is_head)
99 return 1;
100 if (ref1->type < ref2->type)
101 return -1;
102 if (ref1->type > ref2->type)
103 return 1;
104 /* merging of sequenced refs is not allowed */
105 if (ref1->seq < ref2->seq)
106 return -1;
107 if (ref1->seq > ref2->seq)
108 return 1;
109 if (ref1->type == BTRFS_TREE_BLOCK_REF_KEY ||
110 ref1->type == BTRFS_SHARED_BLOCK_REF_KEY) {
111 return comp_tree_refs(btrfs_delayed_node_to_tree_ref(ref2),
112 btrfs_delayed_node_to_tree_ref(ref1));
113 } else if (ref1->type == BTRFS_EXTENT_DATA_REF_KEY ||
114 ref1->type == BTRFS_SHARED_DATA_REF_KEY) {
115 return comp_data_refs(btrfs_delayed_node_to_data_ref(ref2),
116 btrfs_delayed_node_to_data_ref(ref1));
117 }
118 BUG();
119 return 0;
120}
121
122/*
123 * insert a new ref into the rbtree. This returns any existing refs
124 * for the same (bytenr,parent) tuple, or NULL if the new node was properly
125 * inserted.
126 */
127static struct btrfs_delayed_ref_node *tree_insert(struct rb_root *root,
128 struct rb_node *node)
129{
130 struct rb_node **p = &root->rb_node;
131 struct rb_node *parent_node = NULL;
132 struct btrfs_delayed_ref_node *entry;
133 struct btrfs_delayed_ref_node *ins;
134 int cmp;
135
136 ins = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);
137 while (*p) {
138 parent_node = *p;
139 entry = rb_entry(parent_node, struct btrfs_delayed_ref_node,
140 rb_node);
141
142 cmp = comp_entry(entry, ins);
143 if (cmp < 0)
144 p = &(*p)->rb_left;
145 else if (cmp > 0)
146 p = &(*p)->rb_right;
147 else
148 return entry;
149 }
150
151 rb_link_node(node, parent_node, p);
152 rb_insert_color(node, root);
153 return NULL;
154}
155
156/*
157 * find an head entry based on bytenr. This returns the delayed ref
158 * head if it was able to find one, or NULL if nothing was in that spot.
159 * If return_bigger is given, the next bigger entry is returned if no exact
160 * match is found.
161 */
162static struct btrfs_delayed_ref_node *find_ref_head(struct rb_root *root,
163 u64 bytenr,
164 struct btrfs_delayed_ref_node **last,
165 int return_bigger)
166{
167 struct rb_node *n;
168 struct btrfs_delayed_ref_node *entry;
169 int cmp = 0;
170
171again:
172 n = root->rb_node;
173 entry = NULL;
174 while (n) {
175 entry = rb_entry(n, struct btrfs_delayed_ref_node, rb_node);
176 WARN_ON(!entry->in_tree);
177 if (last)
178 *last = entry;
179
180 if (bytenr < entry->bytenr)
181 cmp = -1;
182 else if (bytenr > entry->bytenr)
183 cmp = 1;
184 else if (!btrfs_delayed_ref_is_head(entry))
185 cmp = 1;
186 else
187 cmp = 0;
188
189 if (cmp < 0)
190 n = n->rb_left;
191 else if (cmp > 0)
192 n = n->rb_right;
193 else
194 return entry;
195 }
196 if (entry && return_bigger) {
197 if (cmp > 0) {
198 n = rb_next(&entry->rb_node);
199 if (!n)
200 n = rb_first(root);
201 entry = rb_entry(n, struct btrfs_delayed_ref_node,
202 rb_node);
203 bytenr = entry->bytenr;
204 return_bigger = 0;
205 goto again;
206 }
207 return entry;
208 }
209 return NULL;
210}
211
212int btrfs_delayed_ref_lock(struct btrfs_trans_handle *trans,
213 struct btrfs_delayed_ref_head *head)
214{
215 struct btrfs_delayed_ref_root *delayed_refs;
216
217 delayed_refs = &trans->transaction->delayed_refs;
218 assert_spin_locked(&delayed_refs->lock);
219 if (mutex_trylock(&head->mutex))
220 return 0;
221
222 atomic_inc(&head->node.refs);
223 spin_unlock(&delayed_refs->lock);
224
225 mutex_lock(&head->mutex);
226 spin_lock(&delayed_refs->lock);
227 if (!head->node.in_tree) {
228 mutex_unlock(&head->mutex);
229 btrfs_put_delayed_ref(&head->node);
230 return -EAGAIN;
231 }
232 btrfs_put_delayed_ref(&head->node);
233 return 0;
234}
235
236int btrfs_check_delayed_seq(struct btrfs_delayed_ref_root *delayed_refs,
237 u64 seq)
238{
239 struct seq_list *elem;
240
241 assert_spin_locked(&delayed_refs->lock);
242 if (list_empty(&delayed_refs->seq_head))
243 return 0;
244
245 elem = list_first_entry(&delayed_refs->seq_head, struct seq_list, list);
246 if (seq >= elem->seq) {
247 pr_debug("holding back delayed_ref %llu, lowest is %llu (%p)\n",
248 seq, elem->seq, delayed_refs);
249 return 1;
250 }
251 return 0;
252}
253
254int btrfs_find_ref_cluster(struct btrfs_trans_handle *trans,
255 struct list_head *cluster, u64 start)
256{
257 int count = 0;
258 struct btrfs_delayed_ref_root *delayed_refs;
259 struct rb_node *node;
260 struct btrfs_delayed_ref_node *ref;
261 struct btrfs_delayed_ref_head *head;
262
263 delayed_refs = &trans->transaction->delayed_refs;
264 if (start == 0) {
265 node = rb_first(&delayed_refs->root);
266 } else {
267 ref = NULL;
268 find_ref_head(&delayed_refs->root, start + 1, &ref, 1);
269 if (ref) {
270 node = &ref->rb_node;
271 } else
272 node = rb_first(&delayed_refs->root);
273 }
274again:
275 while (node && count < 32) {
276 ref = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);
277 if (btrfs_delayed_ref_is_head(ref)) {
278 head = btrfs_delayed_node_to_head(ref);
279 if (list_empty(&head->cluster)) {
280 list_add_tail(&head->cluster, cluster);
281 delayed_refs->run_delayed_start =
282 head->node.bytenr;
283 count++;
284
285 WARN_ON(delayed_refs->num_heads_ready == 0);
286 delayed_refs->num_heads_ready--;
287 } else if (count) {
288 /* the goal of the clustering is to find extents
289 * that are likely to end up in the same extent
290 * leaf on disk. So, we don't want them spread
291 * all over the tree. Stop now if we've hit
292 * a head that was already in use
293 */
294 break;
295 }
296 }
297 node = rb_next(node);
298 }
299 if (count) {
300 return 0;
301 } else if (start) {
302 /*
303 * we've gone to the end of the rbtree without finding any
304 * clusters. start from the beginning and try again
305 */
306 start = 0;
307 node = rb_first(&delayed_refs->root);
308 goto again;
309 }
310 return 1;
311}
312
313/*
314 * helper function to update an extent delayed ref in the
315 * rbtree. existing and update must both have the same
316 * bytenr and parent
317 *
318 * This may free existing if the update cancels out whatever
319 * operation it was doing.
320 */
321static noinline void
322update_existing_ref(struct btrfs_trans_handle *trans,
323 struct btrfs_delayed_ref_root *delayed_refs,
324 struct btrfs_delayed_ref_node *existing,
325 struct btrfs_delayed_ref_node *update)
326{
327 if (update->action != existing->action) {
328 /*
329 * this is effectively undoing either an add or a
330 * drop. We decrement the ref_mod, and if it goes
331 * down to zero we just delete the entry without
332 * every changing the extent allocation tree.
333 */
334 existing->ref_mod--;
335 if (existing->ref_mod == 0) {
336 rb_erase(&existing->rb_node,
337 &delayed_refs->root);
338 existing->in_tree = 0;
339 btrfs_put_delayed_ref(existing);
340 delayed_refs->num_entries--;
341 if (trans->delayed_ref_updates)
342 trans->delayed_ref_updates--;
343 } else {
344 WARN_ON(existing->type == BTRFS_TREE_BLOCK_REF_KEY ||
345 existing->type == BTRFS_SHARED_BLOCK_REF_KEY);
346 }
347 } else {
348 WARN_ON(existing->type == BTRFS_TREE_BLOCK_REF_KEY ||
349 existing->type == BTRFS_SHARED_BLOCK_REF_KEY);
350 /*
351 * the action on the existing ref matches
352 * the action on the ref we're trying to add.
353 * Bump the ref_mod by one so the backref that
354 * is eventually added/removed has the correct
355 * reference count
356 */
357 existing->ref_mod += update->ref_mod;
358 }
359}
360
361/*
362 * helper function to update the accounting in the head ref
363 * existing and update must have the same bytenr
364 */
365static noinline void
366update_existing_head_ref(struct btrfs_delayed_ref_node *existing,
367 struct btrfs_delayed_ref_node *update)
368{
369 struct btrfs_delayed_ref_head *existing_ref;
370 struct btrfs_delayed_ref_head *ref;
371
372 existing_ref = btrfs_delayed_node_to_head(existing);
373 ref = btrfs_delayed_node_to_head(update);
374 BUG_ON(existing_ref->is_data != ref->is_data);
375
376 if (ref->must_insert_reserved) {
377 /* if the extent was freed and then
378 * reallocated before the delayed ref
379 * entries were processed, we can end up
380 * with an existing head ref without
381 * the must_insert_reserved flag set.
382 * Set it again here
383 */
384 existing_ref->must_insert_reserved = ref->must_insert_reserved;
385
386 /*
387 * update the num_bytes so we make sure the accounting
388 * is done correctly
389 */
390 existing->num_bytes = update->num_bytes;
391
392 }
393
394 if (ref->extent_op) {
395 if (!existing_ref->extent_op) {
396 existing_ref->extent_op = ref->extent_op;
397 } else {
398 if (ref->extent_op->update_key) {
399 memcpy(&existing_ref->extent_op->key,
400 &ref->extent_op->key,
401 sizeof(ref->extent_op->key));
402 existing_ref->extent_op->update_key = 1;
403 }
404 if (ref->extent_op->update_flags) {
405 existing_ref->extent_op->flags_to_set |=
406 ref->extent_op->flags_to_set;
407 existing_ref->extent_op->update_flags = 1;
408 }
409 kfree(ref->extent_op);
410 }
411 }
412 /*
413 * update the reference mod on the head to reflect this new operation
414 */
415 existing->ref_mod += update->ref_mod;
416}
417
418/*
419 * helper function to actually insert a head node into the rbtree.
420 * this does all the dirty work in terms of maintaining the correct
421 * overall modification count.
422 */
423static noinline void add_delayed_ref_head(struct btrfs_fs_info *fs_info,
424 struct btrfs_trans_handle *trans,
425 struct btrfs_delayed_ref_node *ref,
426 u64 bytenr, u64 num_bytes,
427 int action, int is_data)
428{
429 struct btrfs_delayed_ref_node *existing;
430 struct btrfs_delayed_ref_head *head_ref = NULL;
431 struct btrfs_delayed_ref_root *delayed_refs;
432 int count_mod = 1;
433 int must_insert_reserved = 0;
434
435 /*
436 * the head node stores the sum of all the mods, so dropping a ref
437 * should drop the sum in the head node by one.
438 */
439 if (action == BTRFS_UPDATE_DELAYED_HEAD)
440 count_mod = 0;
441 else if (action == BTRFS_DROP_DELAYED_REF)
442 count_mod = -1;
443
444 /*
445 * BTRFS_ADD_DELAYED_EXTENT means that we need to update
446 * the reserved accounting when the extent is finally added, or
447 * if a later modification deletes the delayed ref without ever
448 * inserting the extent into the extent allocation tree.
449 * ref->must_insert_reserved is the flag used to record
450 * that accounting mods are required.
451 *
452 * Once we record must_insert_reserved, switch the action to
453 * BTRFS_ADD_DELAYED_REF because other special casing is not required.
454 */
455 if (action == BTRFS_ADD_DELAYED_EXTENT)
456 must_insert_reserved = 1;
457 else
458 must_insert_reserved = 0;
459
460 delayed_refs = &trans->transaction->delayed_refs;
461
462 /* first set the basic ref node struct up */
463 atomic_set(&ref->refs, 1);
464 ref->bytenr = bytenr;
465 ref->num_bytes = num_bytes;
466 ref->ref_mod = count_mod;
467 ref->type = 0;
468 ref->action = 0;
469 ref->is_head = 1;
470 ref->in_tree = 1;
471 ref->seq = 0;
472
473 head_ref = btrfs_delayed_node_to_head(ref);
474 head_ref->must_insert_reserved = must_insert_reserved;
475 head_ref->is_data = is_data;
476
477 INIT_LIST_HEAD(&head_ref->cluster);
478 mutex_init(&head_ref->mutex);
479
480 trace_btrfs_delayed_ref_head(ref, head_ref, action);
481
482 existing = tree_insert(&delayed_refs->root, &ref->rb_node);
483
484 if (existing) {
485 update_existing_head_ref(existing, ref);
486 /*
487 * we've updated the existing ref, free the newly
488 * allocated ref
489 */
490 kfree(head_ref);
491 } else {
492 delayed_refs->num_heads++;
493 delayed_refs->num_heads_ready++;
494 delayed_refs->num_entries++;
495 trans->delayed_ref_updates++;
496 }
497}
498
499/*
500 * helper to insert a delayed tree ref into the rbtree.
501 */
502static noinline void add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
503 struct btrfs_trans_handle *trans,
504 struct btrfs_delayed_ref_node *ref,
505 u64 bytenr, u64 num_bytes, u64 parent,
506 u64 ref_root, int level, int action,
507 int for_cow)
508{
509 struct btrfs_delayed_ref_node *existing;
510 struct btrfs_delayed_tree_ref *full_ref;
511 struct btrfs_delayed_ref_root *delayed_refs;
512 u64 seq = 0;
513
514 if (action == BTRFS_ADD_DELAYED_EXTENT)
515 action = BTRFS_ADD_DELAYED_REF;
516
517 delayed_refs = &trans->transaction->delayed_refs;
518
519 /* first set the basic ref node struct up */
520 atomic_set(&ref->refs, 1);
521 ref->bytenr = bytenr;
522 ref->num_bytes = num_bytes;
523 ref->ref_mod = 1;
524 ref->action = action;
525 ref->is_head = 0;
526 ref->in_tree = 1;
527
528 if (is_fstree(ref_root))
529 seq = inc_delayed_seq(delayed_refs);
530 ref->seq = seq;
531
532 full_ref = btrfs_delayed_node_to_tree_ref(ref);
533 full_ref->parent = parent;
534 full_ref->root = ref_root;
535 if (parent)
536 ref->type = BTRFS_SHARED_BLOCK_REF_KEY;
537 else
538 ref->type = BTRFS_TREE_BLOCK_REF_KEY;
539 full_ref->level = level;
540
541 trace_btrfs_delayed_tree_ref(ref, full_ref, action);
542
543 existing = tree_insert(&delayed_refs->root, &ref->rb_node);
544
545 if (existing) {
546 update_existing_ref(trans, delayed_refs, existing, ref);
547 /*
548 * we've updated the existing ref, free the newly
549 * allocated ref
550 */
551 kfree(full_ref);
552 } else {
553 delayed_refs->num_entries++;
554 trans->delayed_ref_updates++;
555 }
556}
557
558/*
559 * helper to insert a delayed data ref into the rbtree.
560 */
561static noinline void add_delayed_data_ref(struct btrfs_fs_info *fs_info,
562 struct btrfs_trans_handle *trans,
563 struct btrfs_delayed_ref_node *ref,
564 u64 bytenr, u64 num_bytes, u64 parent,
565 u64 ref_root, u64 owner, u64 offset,
566 int action, int for_cow)
567{
568 struct btrfs_delayed_ref_node *existing;
569 struct btrfs_delayed_data_ref *full_ref;
570 struct btrfs_delayed_ref_root *delayed_refs;
571 u64 seq = 0;
572
573 if (action == BTRFS_ADD_DELAYED_EXTENT)
574 action = BTRFS_ADD_DELAYED_REF;
575
576 delayed_refs = &trans->transaction->delayed_refs;
577
578 /* first set the basic ref node struct up */
579 atomic_set(&ref->refs, 1);
580 ref->bytenr = bytenr;
581 ref->num_bytes = num_bytes;
582 ref->ref_mod = 1;
583 ref->action = action;
584 ref->is_head = 0;
585 ref->in_tree = 1;
586
587 if (is_fstree(ref_root))
588 seq = inc_delayed_seq(delayed_refs);
589 ref->seq = seq;
590
591 full_ref = btrfs_delayed_node_to_data_ref(ref);
592 full_ref->parent = parent;
593 full_ref->root = ref_root;
594 if (parent)
595 ref->type = BTRFS_SHARED_DATA_REF_KEY;
596 else
597 ref->type = BTRFS_EXTENT_DATA_REF_KEY;
598
599 full_ref->objectid = owner;
600 full_ref->offset = offset;
601
602 trace_btrfs_delayed_data_ref(ref, full_ref, action);
603
604 existing = tree_insert(&delayed_refs->root, &ref->rb_node);
605
606 if (existing) {
607 update_existing_ref(trans, delayed_refs, existing, ref);
608 /*
609 * we've updated the existing ref, free the newly
610 * allocated ref
611 */
612 kfree(full_ref);
613 } else {
614 delayed_refs->num_entries++;
615 trans->delayed_ref_updates++;
616 }
617}
618
619/*
620 * add a delayed tree ref. This does all of the accounting required
621 * to make sure the delayed ref is eventually processed before this
622 * transaction commits.
623 */
624int btrfs_add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
625 struct btrfs_trans_handle *trans,
626 u64 bytenr, u64 num_bytes, u64 parent,
627 u64 ref_root, int level, int action,
628 struct btrfs_delayed_extent_op *extent_op,
629 int for_cow)
630{
631 struct btrfs_delayed_tree_ref *ref;
632 struct btrfs_delayed_ref_head *head_ref;
633 struct btrfs_delayed_ref_root *delayed_refs;
634
635 BUG_ON(extent_op && extent_op->is_data);
636 ref = kmalloc(sizeof(*ref), GFP_NOFS);
637 if (!ref)
638 return -ENOMEM;
639
640 head_ref = kmalloc(sizeof(*head_ref), GFP_NOFS);
641 if (!head_ref) {
642 kfree(ref);
643 return -ENOMEM;
644 }
645
646 head_ref->extent_op = extent_op;
647
648 delayed_refs = &trans->transaction->delayed_refs;
649 spin_lock(&delayed_refs->lock);
650
651 /*
652 * insert both the head node and the new ref without dropping
653 * the spin lock
654 */
655 add_delayed_ref_head(fs_info, trans, &head_ref->node, bytenr,
656 num_bytes, action, 0);
657
658 add_delayed_tree_ref(fs_info, trans, &ref->node, bytenr,
659 num_bytes, parent, ref_root, level, action,
660 for_cow);
661 if (!is_fstree(ref_root) &&
662 waitqueue_active(&delayed_refs->seq_wait))
663 wake_up(&delayed_refs->seq_wait);
664 spin_unlock(&delayed_refs->lock);
665
666 return 0;
667}
668
669/*
670 * add a delayed data ref. it's similar to btrfs_add_delayed_tree_ref.
671 */
672int btrfs_add_delayed_data_ref(struct btrfs_fs_info *fs_info,
673 struct btrfs_trans_handle *trans,
674 u64 bytenr, u64 num_bytes,
675 u64 parent, u64 ref_root,
676 u64 owner, u64 offset, int action,
677 struct btrfs_delayed_extent_op *extent_op,
678 int for_cow)
679{
680 struct btrfs_delayed_data_ref *ref;
681 struct btrfs_delayed_ref_head *head_ref;
682 struct btrfs_delayed_ref_root *delayed_refs;
683
684 BUG_ON(extent_op && !extent_op->is_data);
685 ref = kmalloc(sizeof(*ref), GFP_NOFS);
686 if (!ref)
687 return -ENOMEM;
688
689 head_ref = kmalloc(sizeof(*head_ref), GFP_NOFS);
690 if (!head_ref) {
691 kfree(ref);
692 return -ENOMEM;
693 }
694
695 head_ref->extent_op = extent_op;
696
697 delayed_refs = &trans->transaction->delayed_refs;
698 spin_lock(&delayed_refs->lock);
699
700 /*
701 * insert both the head node and the new ref without dropping
702 * the spin lock
703 */
704 add_delayed_ref_head(fs_info, trans, &head_ref->node, bytenr,
705 num_bytes, action, 1);
706
707 add_delayed_data_ref(fs_info, trans, &ref->node, bytenr,
708 num_bytes, parent, ref_root, owner, offset,
709 action, for_cow);
710 if (!is_fstree(ref_root) &&
711 waitqueue_active(&delayed_refs->seq_wait))
712 wake_up(&delayed_refs->seq_wait);
713 spin_unlock(&delayed_refs->lock);
714
715 return 0;
716}
717
718int btrfs_add_delayed_extent_op(struct btrfs_fs_info *fs_info,
719 struct btrfs_trans_handle *trans,
720 u64 bytenr, u64 num_bytes,
721 struct btrfs_delayed_extent_op *extent_op)
722{
723 struct btrfs_delayed_ref_head *head_ref;
724 struct btrfs_delayed_ref_root *delayed_refs;
725
726 head_ref = kmalloc(sizeof(*head_ref), GFP_NOFS);
727 if (!head_ref)
728 return -ENOMEM;
729
730 head_ref->extent_op = extent_op;
731
732 delayed_refs = &trans->transaction->delayed_refs;
733 spin_lock(&delayed_refs->lock);
734
735 add_delayed_ref_head(fs_info, trans, &head_ref->node, bytenr,
736 num_bytes, BTRFS_UPDATE_DELAYED_HEAD,
737 extent_op->is_data);
738
739 if (waitqueue_active(&delayed_refs->seq_wait))
740 wake_up(&delayed_refs->seq_wait);
741 spin_unlock(&delayed_refs->lock);
742 return 0;
743}
744
745/*
746 * this does a simple search for the head node for a given extent.
747 * It must be called with the delayed ref spinlock held, and it returns
748 * the head node if any where found, or NULL if not.
749 */
750struct btrfs_delayed_ref_head *
751btrfs_find_delayed_ref_head(struct btrfs_trans_handle *trans, u64 bytenr)
752{
753 struct btrfs_delayed_ref_node *ref;
754 struct btrfs_delayed_ref_root *delayed_refs;
755
756 delayed_refs = &trans->transaction->delayed_refs;
757 ref = find_ref_head(&delayed_refs->root, bytenr, NULL, 0);
758 if (ref)
759 return btrfs_delayed_node_to_head(ref);
760 return NULL;
761}