summaryrefslogtreecommitdiffstats
path: root/fs/btrfs/delayed-ref.c
blob: c219463fb1fde9ede3cbe9d53622c8659b1545b0 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
/*
 * Copyright (C) 2009 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/sort.h>
#include "ctree.h"
#include "delayed-ref.h"
#include "transaction.h"

struct kmem_cache *btrfs_delayed_ref_head_cachep;
struct kmem_cache *btrfs_delayed_tree_ref_cachep;
struct kmem_cache *btrfs_delayed_data_ref_cachep;
struct kmem_cache *btrfs_delayed_extent_op_cachep;
/*
 * delayed back reference update tracking.  For subvolume trees
 * we queue up extent allocations and backref maintenance for
 * delayed processing.   This avoids deep call chains where we
 * add extents in the middle of btrfs_search_slot, and it allows
 * us to buffer up frequently modified backrefs in an rb tree instead
 * of hammering updates on the extent allocation tree.
 */

/*
 * compare two delayed tree backrefs with same bytenr and type
 */
static int comp_tree_refs(struct btrfs_delayed_tree_ref *ref2,
			  struct btrfs_delayed_tree_ref *ref1, int type)
{
	if (type == BTRFS_TREE_BLOCK_REF_KEY) {
		if (ref1->root < ref2->root)
			return -1;
		if (ref1->root > ref2->root)
			return 1;
	} else {
		if (ref1->parent < ref2->parent)
			return -1;
		if (ref1->parent > ref2->parent)
			return 1;
	}
	return 0;
}

/*
 * compare two delayed data backrefs with same bytenr and type
 */
static int comp_data_refs(struct btrfs_delayed_data_ref *ref2,
			  struct btrfs_delayed_data_ref *ref1)
{
	if (ref1->node.type == BTRFS_EXTENT_DATA_REF_KEY) {
		if (ref1->root < ref2->root)
			return -1;
		if (ref1->root > ref2->root)
			return 1;
		if (ref1->objectid < ref2->objectid)
			return -1;
		if (ref1->objectid > ref2->objectid)
			return 1;
		if (ref1->offset < ref2->offset)
			return -1;
		if (ref1->offset > ref2->offset)
			return 1;
	} else {
		if (ref1->parent < ref2->parent)
			return -1;
		if (ref1->parent > ref2->parent)
			return 1;
	}
	return 0;
}

/*
 * entries in the rb tree are ordered by the byte number of the extent,
 * type of the delayed backrefs and content of delayed backrefs.
 */
static int comp_entry(struct btrfs_delayed_ref_node *ref2,
		      struct btrfs_delayed_ref_node *ref1,
		      bool compare_seq)
{
	if (ref1->bytenr < ref2->bytenr)
		return -1;
	if (ref1->bytenr > ref2->bytenr)
		return 1;
	if (ref1->is_head && ref2->is_head)
		return 0;
	if (ref2->is_head)
		return -1;
	if (ref1->is_head)
		return 1;
	if (ref1->type < ref2->type)
		return -1;
	if (ref1->type > ref2->type)
		return 1;
	/* merging of sequenced refs is not allowed */
	if (compare_seq) {
		if (ref1->seq < ref2->seq)
			return -1;
		if (ref1->seq > ref2->seq)
			return 1;
	}
	if (ref1->type == BTRFS_TREE_BLOCK_REF_KEY ||
	    ref1->type == BTRFS_SHARED_BLOCK_REF_KEY) {
		return comp_tree_refs(btrfs_delayed_node_to_tree_ref(ref2),
				      btrfs_delayed_node_to_tree_ref(ref1),
				      ref1->type);
	} else if (ref1->type == BTRFS_EXTENT_DATA_REF_KEY ||
		   ref1->type == BTRFS_SHARED_DATA_REF_KEY) {
		return comp_data_refs(btrfs_delayed_node_to_data_ref(ref2),
				      btrfs_delayed_node_to_data_ref(ref1));
	}
	BUG();
	return 0;
}

/*
 * insert a new ref into the rbtree.  This returns any existing refs
 * for the same (bytenr,parent) tuple, or NULL if the new node was properly
 * inserted.
 */
static struct btrfs_delayed_ref_node *tree_insert(struct rb_root *root,
						  struct rb_node *node)
{
	struct rb_node **p = &root->rb_node;
	struct rb_node *parent_node = NULL;
	struct btrfs_delayed_ref_node *entry;
	struct btrfs_delayed_ref_node *ins;
	int cmp;

	ins = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);
	while (*p) {
		parent_node = *p;
		entry = rb_entry(parent_node, struct btrfs_delayed_ref_node,
				 rb_node);

		cmp = comp_entry(entry, ins, 1);
		if (cmp < 0)
			p = &(*p)->rb_left;
		else if (cmp > 0)
			p = &(*p)->rb_right;
		else
			return entry;
	}

	rb_link_node(node, parent_node, p);
	rb_insert_color(node, root);
	return NULL;
}

/*
 * find an head entry based on bytenr. This returns the delayed ref
 * head if it was able to find one, or NULL if nothing was in that spot.
 * If return_bigger is given, the next bigger entry is returned if no exact
 * match is found.
 */
static struct btrfs_delayed_ref_node *find_ref_head(struct rb_root *root,
				  u64 bytenr,
				  struct btrfs_delayed_ref_node **last,
				  int return_bigger)
{
	struct rb_node *n;
	struct btrfs_delayed_ref_node *entry;
	int cmp = 0;

again:
	n = root->rb_node;
	entry = NULL;
	while (n) {
		entry = rb_entry(n, struct btrfs_delayed_ref_node, rb_node);
		WARN_ON(!entry->in_tree);
		if (last)
			*last = entry;

		if (bytenr < entry->bytenr)
			cmp = -1;
		else if (bytenr > entry->bytenr)
			cmp = 1;
		else if (!btrfs_delayed_ref_is_head(entry))
			cmp = 1;
		else
			cmp = 0;

		if (cmp < 0)
			n = n->rb_left;
		else if (cmp > 0)
			n = n->rb_right;
		else
			return entry;
	}
	if (entry && return_bigger) {
		if (cmp > 0) {
			n = rb_next(&entry->rb_node);
			if (!n)
				n = rb_first(root);
			entry = rb_entry(n, struct btrfs_delayed_ref_node,
					 rb_node);
			bytenr = entry->bytenr;
			return_bigger = 0;
			goto again;
		}
		return entry;
	}
	return NULL;
}

int btrfs_delayed_ref_lock(struct btrfs_trans_handle *trans,
			   struct btrfs_delayed_ref_head *head)
{
	struct btrfs_delayed_ref_root *delayed_refs;

	delayed_refs = &trans->transaction->delayed_refs;
	assert_spin_locked(&delayed_refs->lock);
	if (mutex_trylock(&head->mutex))
		return 0;

	atomic_inc(&head->node.refs);
	spin_unlock(&delayed_refs->lock);

	mutex_lock(&head->mutex);
	spin_lock(&delayed_refs->lock);
	if (!head->node.in_tree) {
		mutex_unlock(&head->mutex);
		btrfs_put_delayed_ref(&head->node);
		return -EAGAIN;
	}
	btrfs_put_delayed_ref(&head->node);
	return 0;
}

static void inline drop_delayed_ref(struct btrfs_trans_handle *trans,
				    struct btrfs_delayed_ref_root *delayed_refs,
				    struct btrfs_delayed_ref_node *ref)
{
	rb_erase(&ref->rb_node, &delayed_refs->root);
	ref->in_tree = 0;
	btrfs_put_delayed_ref(ref);
	delayed_refs->num_entries--;
	if (trans->delayed_ref_updates)
		trans->delayed_ref_updates--;
}

static int merge_ref(struct btrfs_trans_handle *trans,
		     struct btrfs_delayed_ref_root *delayed_refs,
		     struct btrfs_delayed_ref_node *ref, u64 seq)
{
	struct rb_node *node;
	int merged = 0;
	int mod = 0;
	int done = 0;

	node = rb_prev(&ref->rb_node);
	while (node) {
		struct btrfs_delayed_ref_node *next;

		next = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);
		node = rb_prev(node);
		if (next->bytenr != ref->bytenr)
			break;
		if (seq && next->seq >= seq)
			break;
		if (comp_entry(ref, next, 0))
			continue;

		if (ref->action == next->action) {
			mod = next->ref_mod;
		} else {
			if (ref->ref_mod < next->ref_mod) {
				struct btrfs_delayed_ref_node *tmp;

				tmp = ref;
				ref = next;
				next = tmp;
				done = 1;
			}
			mod = -next->ref_mod;
		}

		merged++;
		drop_delayed_ref(trans, delayed_refs, next);
		ref->ref_mod += mod;
		if (ref->ref_mod == 0) {
			drop_delayed_ref(trans, delayed_refs, ref);
			break;
		} else {
			/*
			 * You can't have multiples of the same ref on a tree
			 * block.
			 */
			WARN_ON(ref->type == BTRFS_TREE_BLOCK_REF_KEY ||
				ref->type == BTRFS_SHARED_BLOCK_REF_KEY);
		}

		if (done)
			break;
		node = rb_prev(&ref->rb_node);
	}

	return merged;
}

void btrfs_merge_delayed_refs(struct btrfs_trans_handle *trans,
			      struct btrfs_fs_info *fs_info,
			      struct btrfs_delayed_ref_root *delayed_refs,
			      struct btrfs_delayed_ref_head *head)
{
	struct rb_node *node;
	u64 seq = 0;

	spin_lock(&fs_info->tree_mod_seq_lock);
	if (!list_empty(&fs_info->tree_mod_seq_list)) {
		struct seq_list *elem;

		elem = list_first_entry(&fs_info->tree_mod_seq_list,
					struct seq_list, list);
		seq = elem->seq;
	}
	spin_unlock(&fs_info->tree_mod_seq_lock);

	node = rb_prev(&head->node.rb_node);
	while (node) {
		struct btrfs_delayed_ref_node *ref;

		ref = rb_entry(node, struct btrfs_delayed_ref_node,
			       rb_node);
		if (ref->bytenr != head->node.bytenr)
			break;

		/* We can't merge refs that are outside of our seq count */
		if (seq && ref->seq >= seq)
			break;
		if (merge_ref(trans, delayed_refs, ref, seq))
			node = rb_prev(&head->node.rb_node);
		else
			node = rb_prev(node);
	}
}

int btrfs_check_delayed_seq(struct btrfs_fs_info *fs_info,
			    struct btrfs_delayed_ref_root *delayed_refs,
			    u64 seq)
{
	struct seq_list *elem;
	int ret = 0;

	spin_lock(&fs_info->tree_mod_seq_lock);
	if (!list_empty(&fs_info->tree_mod_seq_list)) {
		elem = list_first_entry(&fs_info->tree_mod_seq_list,
					struct seq_list, list);
		if (seq >= elem->seq) {
			pr_debug("holding back delayed_ref %#x.%x, lowest is %#x.%x (%p)\n",
				 (u32)(seq >> 32), (u32)seq,
				 (u32)(elem->seq >> 32), (u32)elem->seq,
				 delayed_refs);
			ret = 1;
		}
	}

	spin_unlock(&fs_info->tree_mod_seq_lock);
	return ret;
}

int btrfs_find_ref_cluster(struct btrfs_trans_handle *trans,
			   struct list_head *cluster, u64 start)
{
	int count = 0;
	struct btrfs_delayed_ref_root *delayed_refs;
	struct rb_node *node;
	struct btrfs_delayed_ref_node *ref;
	struct btrfs_delayed_ref_head *head;

	delayed_refs = &trans->transaction->delayed_refs;
	if (start == 0) {
		node = rb_first(&delayed_refs->root);
	} else {
		ref = NULL;
		find_ref_head(&delayed_refs->root, start + 1, &ref, 1);
		if (ref) {
			node = &ref->rb_node;
		} else
			node = rb_first(&delayed_refs->root);
	}
again:
	while (node && count < 32) {
		ref = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);
		if (btrfs_delayed_ref_is_head(ref)) {
			head = btrfs_delayed_node_to_head(ref);
			if (list_empty(&head->cluster)) {
				list_add_tail(&head->cluster, cluster);
				delayed_refs->run_delayed_start =
					head->node.bytenr;
				count++;

				WARN_ON(delayed_refs->num_heads_ready == 0);
				delayed_refs->num_heads_ready--;
			} else if (count) {
				/* the goal of the clustering is to find extents
				 * that are likely to end up in the same extent
				 * leaf on disk.  So, we don't want them spread
				 * all over the tree.  Stop now if we've hit
				 * a head that was already in use
				 */
				break;
			}
		}
		node = rb_next(node);
	}
	if (count) {
		return 0;
	} else if (start) {
		/*
		 * we've gone to the end of the rbtree without finding any
		 * clusters.  start from the beginning and try again
		 */
		start = 0;
		node = rb_first(&delayed_refs->root);
		goto again;
	}
	return 1;
}

void btrfs_release_ref_cluster(struct list_head *cluster)
{
	struct list_head *pos, *q;

	list_for_each_safe(pos, q, cluster)
		list_del_init(pos);
}

/*
 * helper function to update an extent delayed ref in the
 * rbtree.  existing and update must both have the same
 * bytenr and parent
 *
 * This may free existing if the update cancels out whatever
 * operation it was doing.
 */
static noinline void
update_existing_ref(struct btrfs_trans_handle *trans,
		    struct btrfs_delayed_ref_root *delayed_refs,
		    struct btrfs_delayed_ref_node *existing,
		    struct btrfs_delayed_ref_node *update)
{
	if (update->action != existing->action) {
		/*
		 * this is effectively undoing either an add or a
		 * drop.  We decrement the ref_mod, and if it goes
		 * down to zero we just delete the entry without
		 * every changing the extent allocation tree.
		 */
		existing->ref_mod--;
		if (existing->ref_mod == 0)
			drop_delayed_ref(trans, delayed_refs, existing);
		else
			WARN_ON(existing->type == BTRFS_TREE_BLOCK_REF_KEY ||
				existing->type == BTRFS_SHARED_BLOCK_REF_KEY);
	} else {
		WARN_ON(existing->type == BTRFS_TREE_BLOCK_REF_KEY ||
			existing->type == BTRFS_SHARED_BLOCK_REF_KEY);
		/*
		 * the action on the existing ref matches
		 * the action on the ref we're trying to add.
		 * Bump the ref_mod by one so the backref that
		 * is eventually added/removed has the correct
		 * reference count
		 */
		existing->ref_mod += update->ref_mod;
	}
}

/*
 * helper function to update the accounting in the head ref
 * existing and update must have the same bytenr
 */
static noinline void
update_existing_head_ref(struct btrfs_delayed_ref_node *existing,
			 struct btrfs_delayed_ref_node *update)
{
	struct btrfs_delayed_ref_head *existing_ref;
	struct btrfs_delayed_ref_head *ref;

	existing_ref = btrfs_delayed_node_to_head(existing);
	ref = btrfs_delayed_node_to_head(update);
	BUG_ON(existing_ref->is_data != ref->is_data);

	if (ref->must_insert_reserved) {
		/* if the extent was freed and then
		 * reallocated before the delayed ref
		 * entries were processed, we can end up
		 * with an existing head ref without
		 * the must_insert_reserved flag set.
		 * Set it again here
		 */
		existing_ref->must_insert_reserved = ref->must_insert_reserved;

		/*
		 * update the num_bytes so we make sure the accounting
		 * is done correctly
		 */
		existing->num_bytes = update->num_bytes;

	}

	if (ref->extent_op) {
		if (!existing_ref->extent_op) {
			existing_ref->extent_op = ref->extent_op;
		} else {
			if (ref->extent_op->update_key) {
				memcpy(&existing_ref->extent_op->key,
				       &ref->extent_op->key,
				       sizeof(ref->extent_op->key));
				existing_ref->extent_op->update_key = 1;
			}
			if (ref->extent_op->update_flags) {
				existing_ref->extent_op->flags_to_set |=
					ref->extent_op->flags_to_set;
				existing_ref->extent_op->update_flags = 1;
			}
			btrfs_free_delayed_extent_op(ref->extent_op);
		}
	}
	/*
	 * update the reference mod on the head to reflect this new operation
	 */
	existing->ref_mod += update->ref_mod;
}

/*
 * helper function to actually insert a head node into the rbtree.
 * this does all the dirty work in terms of maintaining the correct
 * overall modification count.
 */
static noinline void add_delayed_ref_head(struct btrfs_fs_info *fs_info,
					struct btrfs_trans_handle *trans,
					struct btrfs_delayed_ref_node *ref,
					u64 bytenr, u64 num_bytes,
					int action, int is_data)
{
	struct btrfs_delayed_ref_node *existing;
	struct btrfs_delayed_ref_head *head_ref = NULL;
	struct btrfs_delayed_ref_root *delayed_refs;
	int count_mod = 1;
	int must_insert_reserved = 0;

	/*
	 * the head node stores the sum of all the mods, so dropping a ref
	 * should drop the sum in the head node by one.
	 */
	if (action == BTRFS_UPDATE_DELAYED_HEAD)
		count_mod = 0;
	else if (action == BTRFS_DROP_DELAYED_REF)
		count_mod = -1;

	/*
	 * BTRFS_ADD_DELAYED_EXTENT means that we need to update
	 * the reserved accounting when the extent is finally added, or
	 * if a later modification deletes the delayed ref without ever
	 * inserting the extent into the extent allocation tree.
	 * ref->must_insert_reserved is the flag used to record
	 * that accounting mods are required.
	 *
	 * Once we record must_insert_reserved, switch the action to
	 * BTRFS_ADD_DELAYED_REF because other special casing is not required.
	 */
	if (action == BTRFS_ADD_DELAYED_EXTENT)
		must_insert_reserved = 1;
	else
		must_insert_reserved = 0;

	delayed_refs = &trans->transaction->delayed_refs;

	/* first set the basic ref node struct up */
	atomic_set(&ref->refs, 1);
	ref->bytenr = bytenr;
	ref->num_bytes = num_bytes;
	ref->ref_mod = count_mod;
	ref->type  = 0;
	ref->action  = 0;
	ref->is_head = 1;
	ref->in_tree = 1;
	ref->seq = 0;

	head_ref = btrfs_delayed_node_to_head(ref);
	head_ref->must_insert_reserved = must_insert_reserved;
	head_ref->is_data = is_data;

	INIT_LIST_HEAD(&head_ref->cluster);
	mutex_init(&head_ref->mutex);

	trace_btrfs_delayed_ref_head(ref, head_ref, action);

	existing = tree_insert(&delayed_refs->root, &ref->rb_node);

	if (existing) {
		update_existing_head_ref(existing, ref);
		/*
		 * we've updated the existing ref, free the newly
		 * allocated ref
		 */
		kmem_cache_free(btrfs_delayed_ref_head_cachep, head_ref);
	} else {
		delayed_refs->num_heads++;
		delayed_refs->num_heads_ready++;
		delayed_refs->num_entries++;
		trans->delayed_ref_updates++;
	}
}

/*
 * helper to insert a delayed tree ref into the rbtree.
 */
static noinline void add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
					 struct btrfs_trans_handle *trans,
					 struct btrfs_delayed_ref_node *ref,
					 u64 bytenr, u64 num_bytes, u64 parent,
					 u64 ref_root, int level, int action,
					 int for_cow)
{
	struct btrfs_delayed_ref_node *existing;
	struct btrfs_delayed_tree_ref *full_ref;
	struct btrfs_delayed_ref_root *delayed_refs;
	u64 seq = 0;

	if (action == BTRFS_ADD_DELAYED_EXTENT)
		action = BTRFS_ADD_DELAYED_REF;

	delayed_refs = &trans->transaction->delayed_refs;

	/* first set the basic ref node struct up */
	atomic_set(&ref->refs, 1);
	ref->bytenr = bytenr;
	ref->num_bytes = num_bytes;
	ref->ref_mod = 1;
	ref->action = action;
	ref->is_head = 0;
	ref->in_tree = 1;

	if (need_ref_seq(for_cow, ref_root))
		seq = btrfs_get_tree_mod_seq(fs_info, &trans->delayed_ref_elem);
	ref->seq = seq;

	full_ref = btrfs_delayed_node_to_tree_ref(ref);
	full_ref->parent = parent;
	full_ref->root = ref_root;
	if (parent)
		ref->type = BTRFS_SHARED_BLOCK_REF_KEY;
	else
		ref->type = BTRFS_TREE_BLOCK_REF_KEY;
	full_ref->level = level;

	trace_btrfs_delayed_tree_ref(ref, full_ref, action);

	existing = tree_insert(&delayed_refs->root, &ref->rb_node);

	if (existing) {
		update_existing_ref(trans, delayed_refs, existing, ref);
		/*
		 * we've updated the existing ref, free the newly
		 * allocated ref
		 */
		kmem_cache_free(btrfs_delayed_tree_ref_cachep, full_ref);
	} else {
		delayed_refs->num_entries++;
		trans->delayed_ref_updates++;
	}
}

/*
 * helper to insert a delayed data ref into the rbtree.
 */
static noinline void add_delayed_data_ref(struct btrfs_fs_info *fs_info,
					 struct btrfs_trans_handle *trans,
					 struct btrfs_delayed_ref_node *ref,
					 u64 bytenr, u64 num_bytes, u64 parent,
					 u64 ref_root, u64 owner, u64 offset,
					 int action, int for_cow)
{
	struct btrfs_delayed_ref_node *existing;
	struct btrfs_delayed_data_ref *full_ref;
	struct btrfs_delayed_ref_root *delayed_refs;
	u64 seq = 0;

	if (action == BTRFS_ADD_DELAYED_EXTENT)
		action = BTRFS_ADD_DELAYED_REF;

	delayed_refs = &trans->transaction->delayed_refs;

	/* first set the basic ref node struct up */
	atomic_set(&ref->refs, 1);
	ref->bytenr = bytenr;
	ref->num_bytes = num_bytes;
	ref->ref_mod = 1;
	ref->action = action;
	ref->is_head = 0;
	ref->in_tree = 1;

	if (need_ref_seq(for_cow, ref_root))
		seq = btrfs_get_tree_mod_seq(fs_info, &trans->delayed_ref_elem);
	ref->seq = seq;

	full_ref = btrfs_delayed_node_to_data_ref(ref);
	full_ref->parent = parent;
	full_ref->root = ref_root;
	if (parent)
		ref->type = BTRFS_SHARED_DATA_REF_KEY;
	else
		ref->type = BTRFS_EXTENT_DATA_REF_KEY;

	full_ref->objectid = owner;
	full_ref->offset = offset;

	trace_btrfs_delayed_data_ref(ref, full_ref, action);

	existing = tree_insert(&delayed_refs->root, &ref->rb_node);

	if (existing) {
		update_existing_ref(trans, delayed_refs, existing, ref);
		/*
		 * we've updated the existing ref, free the newly
		 * allocated ref
		 */
		kmem_cache_free(btrfs_delayed_data_ref_cachep, full_ref);
	} else {
		delayed_refs->num_entries++;
		trans->delayed_ref_updates++;
	}
}

/*
 * add a delayed tree ref.  This does all of the accounting required
 * to make sure the delayed ref is eventually processed before this
 * transaction commits.
 */
int btrfs_add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
			       struct btrfs_trans_handle *trans,
			       u64 bytenr, u64 num_bytes, u64 parent,
			       u64 ref_root,  int level, int action,
			       struct btrfs_delayed_extent_op *extent_op,
			       int for_cow)
{
	struct btrfs_delayed_tree_ref *ref;
	struct btrfs_delayed_ref_head *head_ref;
	struct btrfs_delayed_ref_root *delayed_refs;

	BUG_ON(extent_op && extent_op->is_data);
	ref = kmem_cache_alloc(btrfs_delayed_tree_ref_cachep, GFP_NOFS);
	if (!ref)
		return -ENOMEM;

	head_ref = kmem_cache_alloc(btrfs_delayed_ref_head_cachep, GFP_NOFS);
	if (!head_ref) {
		kmem_cache_free(btrfs_delayed_tree_ref_cachep, ref);
		return -ENOMEM;
	}

	head_ref->extent_op = extent_op;

	delayed_refs = &trans->transaction->delayed_refs;
	spin_lock(&delayed_refs->lock);

	/*
	 * insert both the head node and the new ref without dropping
	 * the spin lock
	 */
	add_delayed_ref_head(fs_info, trans, &head_ref->node, bytenr,
				   num_bytes, action, 0);

	add_delayed_tree_ref(fs_info, trans, &ref->node, bytenr,
				   num_bytes, parent, ref_root, level, action,
				   for_cow);
	spin_unlock(&delayed_refs->lock);
	if (need_ref_seq(for_cow, ref_root))
		btrfs_qgroup_record_ref(trans, &ref->node, extent_op);

	return 0;
}

/*
 * add a delayed data ref. it's similar to btrfs_add_delayed_tree_ref.
 */
int btrfs_add_delayed_data_ref(struct btrfs_fs_info *fs_info,
			       struct btrfs_trans_handle *trans,
			       u64 bytenr, u64 num_bytes,
			       u64 parent, u64 ref_root,
			       u64 owner, u64 offset, int action,
			       struct btrfs_delayed_extent_op *extent_op,
			       int for_cow)
{
	struct btrfs_delayed_data_ref *ref;
	struct btrfs_delayed_ref_head *head_ref;
	struct btrfs_delayed_ref_root *delayed_refs;

	BUG_ON(extent_op && !extent_op->is_data);
	ref = kmem_cache_alloc(btrfs_delayed_data_ref_cachep, GFP_NOFS);
	if (!ref)
		return -ENOMEM;

	head_ref = kmem_cache_alloc(btrfs_delayed_ref_head_cachep, GFP_NOFS);
	if (!head_ref) {
		kmem_cache_free(btrfs_delayed_data_ref_cachep, ref);
		return -ENOMEM;
	}

	head_ref->extent_op = extent_op;

	delayed_refs = &trans->transaction->delayed_refs;
	spin_lock(&delayed_refs->lock);

	/*
	 * insert both the head node and the new ref without dropping
	 * the spin lock
	 */
	add_delayed_ref_head(fs_info, trans, &head_ref->node, bytenr,
				   num_bytes, action, 1);

	add_delayed_data_ref(fs_info, trans, &ref->node, bytenr,
				   num_bytes, parent, ref_root, owner, offset,
				   action, for_cow);
	spin_unlock(&delayed_refs->lock);
	if (need_ref_seq(for_cow, ref_root))
		btrfs_qgroup_record_ref(trans, &ref->node, extent_op);

	return 0;
}

int btrfs_add_delayed_extent_op(struct btrfs_fs_info *fs_info,
				struct btrfs_trans_handle *trans,
				u64 bytenr, u64 num_bytes,
				struct btrfs_delayed_extent_op *extent_op)
{
	struct btrfs_delayed_ref_head *head_ref;
	struct btrfs_delayed_ref_root *delayed_refs;

	head_ref = kmem_cache_alloc(btrfs_delayed_ref_head_cachep, GFP_NOFS);
	if (!head_ref)
		return -ENOMEM;

	head_ref->extent_op = extent_op;

	delayed_refs = &trans->transaction->delayed_refs;
	spin_lock(&delayed_refs->lock);

	add_delayed_ref_head(fs_info, trans, &head_ref->node, bytenr,
				   num_bytes, BTRFS_UPDATE_DELAYED_HEAD,
				   extent_op->is_data);

	spin_unlock(&delayed_refs->lock);
	return 0;
}

/*
 * this does a simple search for the head node for a given extent.
 * It must be called with the delayed ref spinlock held, and it returns
 * the head node if any where found, or NULL if not.
 */
struct btrfs_delayed_ref_head *
btrfs_find_delayed_ref_head(struct btrfs_trans_handle *trans, u64 bytenr)
{
	struct btrfs_delayed_ref_node *ref;
	struct btrfs_delayed_ref_root *delayed_refs;

	delayed_refs = &trans->transaction->delayed_refs;
	ref = find_ref_head(&delayed_refs->root, bytenr, NULL, 0);
	if (ref)
		return btrfs_delayed_node_to_head(ref);
	return NULL;
}

void btrfs_delayed_ref_exit(void)
{
	if (btrfs_delayed_ref_head_cachep)
		kmem_cache_destroy(btrfs_delayed_ref_head_cachep);
	if (btrfs_delayed_tree_ref_cachep)
		kmem_cache_destroy(btrfs_delayed_tree_ref_cachep);
	if (btrfs_delayed_data_ref_cachep)
		kmem_cache_destroy(btrfs_delayed_data_ref_cachep);
	if (btrfs_delayed_extent_op_cachep)
		kmem_cache_destroy(btrfs_delayed_extent_op_cachep);
}

int btrfs_delayed_ref_init(void)
{
	btrfs_delayed_ref_head_cachep = kmem_cache_create(
				"btrfs_delayed_ref_head",
				sizeof(struct btrfs_delayed_ref_head), 0,
				SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);
	if (!btrfs_delayed_ref_head_cachep)
		goto fail;

	btrfs_delayed_tree_ref_cachep = kmem_cache_create(
				"btrfs_delayed_tree_ref",
				sizeof(struct btrfs_delayed_tree_ref), 0,
				SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);
	if (!btrfs_delayed_tree_ref_cachep)
		goto fail;

	btrfs_delayed_data_ref_cachep = kmem_cache_create(
				"btrfs_delayed_data_ref",
				sizeof(struct btrfs_delayed_data_ref), 0,
				SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);
	if (!btrfs_delayed_data_ref_cachep)
		goto fail;

	btrfs_delayed_extent_op_cachep = kmem_cache_create(
				"btrfs_delayed_extent_op",
				sizeof(struct btrfs_delayed_extent_op), 0,
				SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);
	if (!btrfs_delayed_extent_op_cachep)
		goto fail;

	return 0;
fail:
	btrfs_delayed_ref_exit();
	return -ENOMEM;
}