summaryrefslogtreecommitdiff
path: root/fs/btrfs/extent-io-tree.c
blob: ff8e117a1ace6a43e393ab58ff5d77875fcde70f (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
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
// SPDX-License-Identifier: GPL-2.0

#include <linux/slab.h>
#include <trace/events/btrfs.h>
#include "messages.h"
#include "ctree.h"
#include "extent-io-tree.h"
#include "btrfs_inode.h"
#include "misc.h"

static struct kmem_cache *extent_state_cache;

static inline bool extent_state_in_tree(const struct extent_state *state)
{
	return !RB_EMPTY_NODE(&state->rb_node);
}

#ifdef CONFIG_BTRFS_DEBUG
static LIST_HEAD(states);
static DEFINE_SPINLOCK(leak_lock);

static inline void btrfs_leak_debug_add_state(struct extent_state *state)
{
	unsigned long flags;

	spin_lock_irqsave(&leak_lock, flags);
	list_add(&state->leak_list, &states);
	spin_unlock_irqrestore(&leak_lock, flags);
}

static inline void btrfs_leak_debug_del_state(struct extent_state *state)
{
	unsigned long flags;

	spin_lock_irqsave(&leak_lock, flags);
	list_del(&state->leak_list);
	spin_unlock_irqrestore(&leak_lock, flags);
}

static inline void btrfs_extent_state_leak_debug_check(void)
{
	struct extent_state *state;

	while (!list_empty(&states)) {
		state = list_entry(states.next, struct extent_state, leak_list);
		pr_err("BTRFS: state leak: start %llu end %llu state %u in tree %d refs %d\n",
		       state->start, state->end, state->state,
		       extent_state_in_tree(state),
		       refcount_read(&state->refs));
		list_del(&state->leak_list);
		kmem_cache_free(extent_state_cache, state);
	}
}

#define btrfs_debug_check_extent_io_range(tree, start, end)		\
	__btrfs_debug_check_extent_io_range(__func__, (tree), (start), (end))
static inline void __btrfs_debug_check_extent_io_range(const char *caller,
						       struct extent_io_tree *tree,
						       u64 start, u64 end)
{
	struct btrfs_inode *inode = tree->inode;
	u64 isize;

	if (!inode)
		return;

	isize = i_size_read(&inode->vfs_inode);
	if (end >= PAGE_SIZE && (end % 2) == 0 && end != isize - 1) {
		btrfs_debug_rl(inode->root->fs_info,
		    "%s: ino %llu isize %llu odd range [%llu,%llu]",
			caller, btrfs_ino(inode), isize, start, end);
	}
}
#else
#define btrfs_leak_debug_add_state(state)		do {} while (0)
#define btrfs_leak_debug_del_state(state)		do {} while (0)
#define btrfs_extent_state_leak_debug_check()		do {} while (0)
#define btrfs_debug_check_extent_io_range(c, s, e)	do {} while (0)
#endif

/*
 * For the file_extent_tree, we want to hold the inode lock when we lookup and
 * update the disk_i_size, but lockdep will complain because our io_tree we hold
 * the tree lock and get the inode lock when setting delalloc.  These two things
 * are unrelated, so make a class for the file_extent_tree so we don't get the
 * two locking patterns mixed up.
 */
static struct lock_class_key file_extent_tree_class;

struct tree_entry {
	u64 start;
	u64 end;
	struct rb_node rb_node;
};

void extent_io_tree_init(struct btrfs_fs_info *fs_info,
			 struct extent_io_tree *tree, unsigned int owner)
{
	tree->fs_info = fs_info;
	tree->state = RB_ROOT;
	spin_lock_init(&tree->lock);
	tree->inode = NULL;
	tree->owner = owner;
	if (owner == IO_TREE_INODE_FILE_EXTENT)
		lockdep_set_class(&tree->lock, &file_extent_tree_class);
}

void extent_io_tree_release(struct extent_io_tree *tree)
{
	spin_lock(&tree->lock);
	/*
	 * Do a single barrier for the waitqueue_active check here, the state
	 * of the waitqueue should not change once extent_io_tree_release is
	 * called.
	 */
	smp_mb();
	while (!RB_EMPTY_ROOT(&tree->state)) {
		struct rb_node *node;
		struct extent_state *state;

		node = rb_first(&tree->state);
		state = rb_entry(node, struct extent_state, rb_node);
		rb_erase(&state->rb_node, &tree->state);
		RB_CLEAR_NODE(&state->rb_node);
		/*
		 * btree io trees aren't supposed to have tasks waiting for
		 * changes in the flags of extent states ever.
		 */
		ASSERT(!waitqueue_active(&state->wq));
		free_extent_state(state);

		cond_resched_lock(&tree->lock);
	}
	spin_unlock(&tree->lock);
}

static struct extent_state *alloc_extent_state(gfp_t mask)
{
	struct extent_state *state;

	/*
	 * The given mask might be not appropriate for the slab allocator,
	 * drop the unsupported bits
	 */
	mask &= ~(__GFP_DMA32|__GFP_HIGHMEM);
	state = kmem_cache_alloc(extent_state_cache, mask);
	if (!state)
		return state;
	state->state = 0;
	RB_CLEAR_NODE(&state->rb_node);
	btrfs_leak_debug_add_state(state);
	refcount_set(&state->refs, 1);
	init_waitqueue_head(&state->wq);
	trace_alloc_extent_state(state, mask, _RET_IP_);
	return state;
}

static struct extent_state *alloc_extent_state_atomic(struct extent_state *prealloc)
{
	if (!prealloc)
		prealloc = alloc_extent_state(GFP_ATOMIC);

	return prealloc;
}

void free_extent_state(struct extent_state *state)
{
	if (!state)
		return;
	if (refcount_dec_and_test(&state->refs)) {
		WARN_ON(extent_state_in_tree(state));
		btrfs_leak_debug_del_state(state);
		trace_free_extent_state(state, _RET_IP_);
		kmem_cache_free(extent_state_cache, state);
	}
}

static int add_extent_changeset(struct extent_state *state, u32 bits,
				 struct extent_changeset *changeset,
				 int set)
{
	int ret;

	if (!changeset)
		return 0;
	if (set && (state->state & bits) == bits)
		return 0;
	if (!set && (state->state & bits) == 0)
		return 0;
	changeset->bytes_changed += state->end - state->start + 1;
	ret = ulist_add(&changeset->range_changed, state->start, state->end,
			GFP_ATOMIC);
	return ret;
}

static inline struct extent_state *next_state(struct extent_state *state)
{
	struct rb_node *next = rb_next(&state->rb_node);

	if (next)
		return rb_entry(next, struct extent_state, rb_node);
	else
		return NULL;
}

static inline struct extent_state *prev_state(struct extent_state *state)
{
	struct rb_node *next = rb_prev(&state->rb_node);

	if (next)
		return rb_entry(next, struct extent_state, rb_node);
	else
		return NULL;
}

/*
 * Search @tree for an entry that contains @offset. Such entry would have
 * entry->start <= offset && entry->end >= offset.
 *
 * @tree:       the tree to search
 * @offset:     offset that should fall within an entry in @tree
 * @node_ret:   pointer where new node should be anchored (used when inserting an
 *	        entry in the tree)
 * @parent_ret: points to entry which would have been the parent of the entry,
 *               containing @offset
 *
 * Return a pointer to the entry that contains @offset byte address and don't change
 * @node_ret and @parent_ret.
 *
 * If no such entry exists, return pointer to entry that ends before @offset
 * and fill parameters @node_ret and @parent_ret, ie. does not return NULL.
 */
static inline struct extent_state *tree_search_for_insert(struct extent_io_tree *tree,
							  u64 offset,
							  struct rb_node ***node_ret,
							  struct rb_node **parent_ret)
{
	struct rb_root *root = &tree->state;
	struct rb_node **node = &root->rb_node;
	struct rb_node *prev = NULL;
	struct extent_state *entry = NULL;

	while (*node) {
		prev = *node;
		entry = rb_entry(prev, struct extent_state, rb_node);

		if (offset < entry->start)
			node = &(*node)->rb_left;
		else if (offset > entry->end)
			node = &(*node)->rb_right;
		else
			return entry;
	}

	if (node_ret)
		*node_ret = node;
	if (parent_ret)
		*parent_ret = prev;

	/* Search neighbors until we find the first one past the end */
	while (entry && offset > entry->end)
		entry = next_state(entry);

	return entry;
}

/*
 * Search offset in the tree or fill neighbor rbtree node pointers.
 *
 * @tree:      the tree to search
 * @offset:    offset that should fall within an entry in @tree
 * @next_ret:  pointer to the first entry whose range ends after @offset
 * @prev_ret:  pointer to the first entry whose range begins before @offset
 *
 * Return a pointer to the entry that contains @offset byte address. If no
 * such entry exists, then return NULL and fill @prev_ret and @next_ret.
 * Otherwise return the found entry and other pointers are left untouched.
 */
static struct extent_state *tree_search_prev_next(struct extent_io_tree *tree,
						  u64 offset,
						  struct extent_state **prev_ret,
						  struct extent_state **next_ret)
{
	struct rb_root *root = &tree->state;
	struct rb_node **node = &root->rb_node;
	struct extent_state *orig_prev;
	struct extent_state *entry = NULL;

	ASSERT(prev_ret);
	ASSERT(next_ret);

	while (*node) {
		entry = rb_entry(*node, struct extent_state, rb_node);

		if (offset < entry->start)
			node = &(*node)->rb_left;
		else if (offset > entry->end)
			node = &(*node)->rb_right;
		else
			return entry;
	}

	orig_prev = entry;
	while (entry && offset > entry->end)
		entry = next_state(entry);
	*next_ret = entry;
	entry = orig_prev;

	while (entry && offset < entry->start)
		entry = prev_state(entry);
	*prev_ret = entry;

	return NULL;
}

/*
 * Inexact rb-tree search, return the next entry if @offset is not found
 */
static inline struct extent_state *tree_search(struct extent_io_tree *tree, u64 offset)
{
	return tree_search_for_insert(tree, offset, NULL, NULL);
}

static void extent_io_tree_panic(struct extent_io_tree *tree, int err)
{
	btrfs_panic(tree->fs_info, err,
	"locking error: extent tree was modified by another thread while locked");
}

/*
 * Utility function to look for merge candidates inside a given range.  Any
 * extents with matching state are merged together into a single extent in the
 * tree.  Extents with EXTENT_IO in their state field are not merged because
 * the end_io handlers need to be able to do operations on them without
 * sleeping (or doing allocations/splits).
 *
 * This should be called with the tree lock held.
 */
static void merge_state(struct extent_io_tree *tree, struct extent_state *state)
{
	struct extent_state *other;

	if (state->state & (EXTENT_LOCKED | EXTENT_BOUNDARY))
		return;

	other = prev_state(state);
	if (other && other->end == state->start - 1 &&
	    other->state == state->state) {
		if (tree->inode)
			btrfs_merge_delalloc_extent(tree->inode, state, other);
		state->start = other->start;
		rb_erase(&other->rb_node, &tree->state);
		RB_CLEAR_NODE(&other->rb_node);
		free_extent_state(other);
	}
	other = next_state(state);
	if (other && other->start == state->end + 1 &&
	    other->state == state->state) {
		if (tree->inode)
			btrfs_merge_delalloc_extent(tree->inode, state, other);
		state->end = other->end;
		rb_erase(&other->rb_node, &tree->state);
		RB_CLEAR_NODE(&other->rb_node);
		free_extent_state(other);
	}
}

static void set_state_bits(struct extent_io_tree *tree,
			   struct extent_state *state,
			   u32 bits, struct extent_changeset *changeset)
{
	u32 bits_to_set = bits & ~EXTENT_CTLBITS;
	int ret;

	if (tree->inode)
		btrfs_set_delalloc_extent(tree->inode, state, bits);

	ret = add_extent_changeset(state, bits_to_set, changeset, 1);
	BUG_ON(ret < 0);
	state->state |= bits_to_set;
}

/*
 * Insert an extent_state struct into the tree.  'bits' are set on the
 * struct before it is inserted.
 *
 * This may return -EEXIST if the extent is already there, in which case the
 * state struct is freed.
 *
 * The tree lock is not taken internally.  This is a utility function and
 * probably isn't what you want to call (see set/clear_extent_bit).
 */
static int insert_state(struct extent_io_tree *tree,
			struct extent_state *state,
			u32 bits, struct extent_changeset *changeset)
{
	struct rb_node **node;
	struct rb_node *parent = NULL;
	const u64 end = state->end;

	set_state_bits(tree, state, bits, changeset);

	node = &tree->state.rb_node;
	while (*node) {
		struct extent_state *entry;

		parent = *node;
		entry = rb_entry(parent, struct extent_state, rb_node);

		if (end < entry->start) {
			node = &(*node)->rb_left;
		} else if (end > entry->end) {
			node = &(*node)->rb_right;
		} else {
			btrfs_err(tree->fs_info,
			       "found node %llu %llu on insert of %llu %llu",
			       entry->start, entry->end, state->start, end);
			return -EEXIST;
		}
	}

	rb_link_node(&state->rb_node, parent, node);
	rb_insert_color(&state->rb_node, &tree->state);

	merge_state(tree, state);
	return 0;
}

/*
 * Insert state to @tree to the location given by @node and @parent.
 */
static void insert_state_fast(struct extent_io_tree *tree,
			      struct extent_state *state, struct rb_node **node,
			      struct rb_node *parent, unsigned bits,
			      struct extent_changeset *changeset)
{
	set_state_bits(tree, state, bits, changeset);
	rb_link_node(&state->rb_node, parent, node);
	rb_insert_color(&state->rb_node, &tree->state);
	merge_state(tree, state);
}

/*
 * Split a given extent state struct in two, inserting the preallocated
 * struct 'prealloc' as the newly created second half.  'split' indicates an
 * offset inside 'orig' where it should be split.
 *
 * Before calling,
 * the tree has 'orig' at [orig->start, orig->end].  After calling, there
 * are two extent state structs in the tree:
 * prealloc: [orig->start, split - 1]
 * orig: [ split, orig->end ]
 *
 * The tree locks are not taken by this function. They need to be held
 * by the caller.
 */
static int split_state(struct extent_io_tree *tree, struct extent_state *orig,
		       struct extent_state *prealloc, u64 split)
{
	struct rb_node *parent = NULL;
	struct rb_node **node;

	if (tree->inode)
		btrfs_split_delalloc_extent(tree->inode, orig, split);

	prealloc->start = orig->start;
	prealloc->end = split - 1;
	prealloc->state = orig->state;
	orig->start = split;

	parent = &orig->rb_node;
	node = &parent;
	while (*node) {
		struct extent_state *entry;

		parent = *node;
		entry = rb_entry(parent, struct extent_state, rb_node);

		if (prealloc->end < entry->start) {
			node = &(*node)->rb_left;
		} else if (prealloc->end > entry->end) {
			node = &(*node)->rb_right;
		} else {
			free_extent_state(prealloc);
			return -EEXIST;
		}
	}

	rb_link_node(&prealloc->rb_node, parent, node);
	rb_insert_color(&prealloc->rb_node, &tree->state);

	return 0;
}

/*
 * Utility function to clear some bits in an extent state struct.  It will
 * optionally wake up anyone waiting on this state (wake == 1).
 *
 * If no bits are set on the state struct after clearing things, the
 * struct is freed and removed from the tree
 */
static struct extent_state *clear_state_bit(struct extent_io_tree *tree,
					    struct extent_state *state,
					    u32 bits, int wake,
					    struct extent_changeset *changeset)
{
	struct extent_state *next;
	u32 bits_to_clear = bits & ~EXTENT_CTLBITS;
	int ret;

	if (tree->inode)
		btrfs_clear_delalloc_extent(tree->inode, state, bits);

	ret = add_extent_changeset(state, bits_to_clear, changeset, 0);
	BUG_ON(ret < 0);
	state->state &= ~bits_to_clear;
	if (wake)
		wake_up(&state->wq);
	if (state->state == 0) {
		next = next_state(state);
		if (extent_state_in_tree(state)) {
			rb_erase(&state->rb_node, &tree->state);
			RB_CLEAR_NODE(&state->rb_node);
			free_extent_state(state);
		} else {
			WARN_ON(1);
		}
	} else {
		merge_state(tree, state);
		next = next_state(state);
	}
	return next;
}

/*
 * Detect if extent bits request NOWAIT semantics and set the gfp mask accordingly,
 * unset the EXTENT_NOWAIT bit.
 */
static void set_gfp_mask_from_bits(u32 *bits, gfp_t *mask)
{
	*mask = (*bits & EXTENT_NOWAIT ? GFP_NOWAIT : GFP_NOFS);
	*bits &= EXTENT_NOWAIT - 1;
}

/*
 * Clear some bits on a range in the tree.  This may require splitting or
 * inserting elements in the tree, so the gfp mask is used to indicate which
 * allocations or sleeping are allowed.
 *
 * Pass 'wake' == 1 to kick any sleepers, and 'delete' == 1 to remove the given
 * range from the tree regardless of state (ie for truncate).
 *
 * The range [start, end] is inclusive.
 *
 * This takes the tree lock, and returns 0 on success and < 0 on error.
 */
int __clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
		       u32 bits, struct extent_state **cached_state,
		       struct extent_changeset *changeset)
{
	struct extent_state *state;
	struct extent_state *cached;
	struct extent_state *prealloc = NULL;
	u64 last_end;
	int err;
	int clear = 0;
	int wake;
	int delete = (bits & EXTENT_CLEAR_ALL_BITS);
	gfp_t mask;

	set_gfp_mask_from_bits(&bits, &mask);
	btrfs_debug_check_extent_io_range(tree, start, end);
	trace_btrfs_clear_extent_bit(tree, start, end - start + 1, bits);

	if (delete)
		bits |= ~EXTENT_CTLBITS;

	if (bits & EXTENT_DELALLOC)
		bits |= EXTENT_NORESERVE;

	wake = (bits & EXTENT_LOCKED) ? 1 : 0;
	if (bits & (EXTENT_LOCKED | EXTENT_BOUNDARY))
		clear = 1;
again:
	if (!prealloc) {
		/*
		 * Don't care for allocation failure here because we might end
		 * up not needing the pre-allocated extent state at all, which
		 * is the case if we only have in the tree extent states that
		 * cover our input range and don't cover too any other range.
		 * If we end up needing a new extent state we allocate it later.
		 */
		prealloc = alloc_extent_state(mask);
	}

	spin_lock(&tree->lock);
	if (cached_state) {
		cached = *cached_state;

		if (clear) {
			*cached_state = NULL;
			cached_state = NULL;
		}

		if (cached && extent_state_in_tree(cached) &&
		    cached->start <= start && cached->end > start) {
			if (clear)
				refcount_dec(&cached->refs);
			state = cached;
			goto hit_next;
		}
		if (clear)
			free_extent_state(cached);
	}

	/* This search will find the extents that end after our range starts. */
	state = tree_search(tree, start);
	if (!state)
		goto out;
hit_next:
	if (state->start > end)
		goto out;
	WARN_ON(state->end < start);
	last_end = state->end;

	/* The state doesn't have the wanted bits, go ahead. */
	if (!(state->state & bits)) {
		state = next_state(state);
		goto next;
	}

	/*
	 *     | ---- desired range ---- |
	 *  | state | or
	 *  | ------------- state -------------- |
	 *
	 * We need to split the extent we found, and may flip bits on second
	 * half.
	 *
	 * If the extent we found extends past our range, we just split and
	 * search again.  It'll get split again the next time though.
	 *
	 * If the extent we found is inside our range, we clear the desired bit
	 * on it.
	 */

	if (state->start < start) {
		prealloc = alloc_extent_state_atomic(prealloc);
		if (!prealloc)
			goto search_again;
		err = split_state(tree, state, prealloc, start);
		if (err)
			extent_io_tree_panic(tree, err);

		prealloc = NULL;
		if (err)
			goto out;
		if (state->end <= end) {
			state = clear_state_bit(tree, state, bits, wake, changeset);
			goto next;
		}
		goto search_again;
	}
	/*
	 * | ---- desired range ---- |
	 *                        | state |
	 * We need to split the extent, and clear the bit on the first half.
	 */
	if (state->start <= end && state->end > end) {
		prealloc = alloc_extent_state_atomic(prealloc);
		if (!prealloc)
			goto search_again;
		err = split_state(tree, state, prealloc, end + 1);
		if (err)
			extent_io_tree_panic(tree, err);

		if (wake)
			wake_up(&state->wq);

		clear_state_bit(tree, prealloc, bits, wake, changeset);

		prealloc = NULL;
		goto out;
	}

	state = clear_state_bit(tree, state, bits, wake, changeset);
next:
	if (last_end == (u64)-1)
		goto out;
	start = last_end + 1;
	if (start <= end && state && !need_resched())
		goto hit_next;

search_again:
	if (start > end)
		goto out;
	spin_unlock(&tree->lock);
	if (gfpflags_allow_blocking(mask))
		cond_resched();
	goto again;

out:
	spin_unlock(&tree->lock);
	if (prealloc)
		free_extent_state(prealloc);

	return 0;

}

static void wait_on_state(struct extent_io_tree *tree,
			  struct extent_state *state)
		__releases(tree->lock)
		__acquires(tree->lock)
{
	DEFINE_WAIT(wait);
	prepare_to_wait(&state->wq, &wait, TASK_UNINTERRUPTIBLE);
	spin_unlock(&tree->lock);
	schedule();
	spin_lock(&tree->lock);
	finish_wait(&state->wq, &wait);
}

/*
 * Wait for one or more bits to clear on a range in the state tree.
 * The range [start, end] is inclusive.
 * The tree lock is taken by this function
 */
void wait_extent_bit(struct extent_io_tree *tree, u64 start, u64 end, u32 bits,
		     struct extent_state **cached_state)
{
	struct extent_state *state;

	btrfs_debug_check_extent_io_range(tree, start, end);

	spin_lock(&tree->lock);
again:
	/*
	 * Maintain cached_state, as we may not remove it from the tree if there
	 * are more bits than the bits we're waiting on set on this state.
	 */
	if (cached_state && *cached_state) {
		state = *cached_state;
		if (extent_state_in_tree(state) &&
		    state->start <= start && start < state->end)
			goto process_node;
	}
	while (1) {
		/*
		 * This search will find all the extents that end after our
		 * range starts.
		 */
		state = tree_search(tree, start);
process_node:
		if (!state)
			break;
		if (state->start > end)
			goto out;

		if (state->state & bits) {
			start = state->start;
			refcount_inc(&state->refs);
			wait_on_state(tree, state);
			free_extent_state(state);
			goto again;
		}
		start = state->end + 1;

		if (start > end)
			break;

		if (!cond_resched_lock(&tree->lock)) {
			state = next_state(state);
			goto process_node;
		}
	}
out:
	/* This state is no longer useful, clear it and free it up. */
	if (cached_state && *cached_state) {
		state = *cached_state;
		*cached_state = NULL;
		free_extent_state(state);
	}
	spin_unlock(&tree->lock);
}

static void cache_state_if_flags(struct extent_state *state,
				 struct extent_state **cached_ptr,
				 unsigned flags)
{
	if (cached_ptr && !(*cached_ptr)) {
		if (!flags || (state->state & flags)) {
			*cached_ptr = state;
			refcount_inc(&state->refs);
		}
	}
}

static void cache_state(struct extent_state *state,
			struct extent_state **cached_ptr)
{
	return cache_state_if_flags(state, cached_ptr,
				    EXTENT_LOCKED | EXTENT_BOUNDARY);
}

/*
 * Find the first state struct with 'bits' set after 'start', and return it.
 * tree->lock must be held.  NULL will returned if nothing was found after
 * 'start'.
 */
static struct extent_state *find_first_extent_bit_state(struct extent_io_tree *tree,
							u64 start, u32 bits)
{
	struct extent_state *state;

	/*
	 * This search will find all the extents that end after our range
	 * starts.
	 */
	state = tree_search(tree, start);
	while (state) {
		if (state->end >= start && (state->state & bits))
			return state;
		state = next_state(state);
	}
	return NULL;
}

/*
 * Find the first offset in the io tree with one or more @bits set.
 *
 * Note: If there are multiple bits set in @bits, any of them will match.
 *
 * Return true if we find something, and update @start_ret and @end_ret.
 * Return false if we found nothing.
 */
bool find_first_extent_bit(struct extent_io_tree *tree, u64 start,
			   u64 *start_ret, u64 *end_ret, u32 bits,
			   struct extent_state **cached_state)
{
	struct extent_state *state;
	bool ret = false;

	spin_lock(&tree->lock);
	if (cached_state && *cached_state) {
		state = *cached_state;
		if (state->end == start - 1 && extent_state_in_tree(state)) {
			while ((state = next_state(state)) != NULL) {
				if (state->state & bits)
					goto got_it;
			}
			free_extent_state(*cached_state);
			*cached_state = NULL;
			goto out;
		}
		free_extent_state(*cached_state);
		*cached_state = NULL;
	}

	state = find_first_extent_bit_state(tree, start, bits);
got_it:
	if (state) {
		cache_state_if_flags(state, cached_state, 0);
		*start_ret = state->start;
		*end_ret = state->end;
		ret = true;
	}
out:
	spin_unlock(&tree->lock);
	return ret;
}

/*
 * Find a contiguous area of bits
 *
 * @tree:      io tree to check
 * @start:     offset to start the search from
 * @start_ret: the first offset we found with the bits set
 * @end_ret:   the final contiguous range of the bits that were set
 * @bits:      bits to look for
 *
 * set_extent_bit and clear_extent_bit can temporarily split contiguous ranges
 * to set bits appropriately, and then merge them again.  During this time it
 * will drop the tree->lock, so use this helper if you want to find the actual
 * contiguous area for given bits.  We will search to the first bit we find, and
 * then walk down the tree until we find a non-contiguous area.  The area
 * returned will be the full contiguous area with the bits set.
 */
int find_contiguous_extent_bit(struct extent_io_tree *tree, u64 start,
			       u64 *start_ret, u64 *end_ret, u32 bits)
{
	struct extent_state *state;
	int ret = 1;

	spin_lock(&tree->lock);
	state = find_first_extent_bit_state(tree, start, bits);
	if (state) {
		*start_ret = state->start;
		*end_ret = state->end;
		while ((state = next_state(state)) != NULL) {
			if (state->start > (*end_ret + 1))
				break;
			*end_ret = state->end;
		}
		ret = 0;
	}
	spin_unlock(&tree->lock);
	return ret;
}

/*
 * Find a contiguous range of bytes in the file marked as delalloc, not more
 * than 'max_bytes'.  start and end are used to return the range,
 *
 * True is returned if we find something, false if nothing was in the tree.
 */
bool btrfs_find_delalloc_range(struct extent_io_tree *tree, u64 *start,
			       u64 *end, u64 max_bytes,
			       struct extent_state **cached_state)
{
	struct extent_state *state;
	u64 cur_start = *start;
	bool found = false;
	u64 total_bytes = 0;

	spin_lock(&tree->lock);

	/*
	 * This search will find all the extents that end after our range
	 * starts.
	 */
	state = tree_search(tree, cur_start);
	if (!state) {
		*end = (u64)-1;
		goto out;
	}

	while (state) {
		if (found && (state->start != cur_start ||
			      (state->state & EXTENT_BOUNDARY))) {
			goto out;
		}
		if (!(state->state & EXTENT_DELALLOC)) {
			if (!found)
				*end = state->end;
			goto out;
		}
		if (!found) {
			*start = state->start;
			*cached_state = state;
			refcount_inc(&state->refs);
		}
		found = true;
		*end = state->end;
		cur_start = state->end + 1;
		total_bytes += state->end - state->start + 1;
		if (total_bytes >= max_bytes)
			break;
		state = next_state(state);
	}
out:
	spin_unlock(&tree->lock);
	return found;
}

/*
 * Set some bits on a range in the tree.  This may require allocations or
 * sleeping. By default all allocations use GFP_NOFS, use EXTENT_NOWAIT for
 * GFP_NOWAIT.
 *
 * If any of the exclusive bits are set, this will fail with -EEXIST if some
 * part of the range already has the desired bits set.  The extent_state of the
 * existing range is returned in failed_state in this case, and the start of the
 * existing range is returned in failed_start.  failed_state is used as an
 * optimization for wait_extent_bit, failed_start must be used as the source of
 * truth as failed_state may have changed since we returned.
 *
 * [start, end] is inclusive This takes the tree lock.
 */
static int __set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
			    u32 bits, u64 *failed_start,
			    struct extent_state **failed_state,
			    struct extent_state **cached_state,
			    struct extent_changeset *changeset)
{
	struct extent_state *state;
	struct extent_state *prealloc = NULL;
	struct rb_node **p = NULL;
	struct rb_node *parent = NULL;
	int err = 0;
	u64 last_start;
	u64 last_end;
	u32 exclusive_bits = (bits & EXTENT_LOCKED);
	gfp_t mask;

	set_gfp_mask_from_bits(&bits, &mask);
	btrfs_debug_check_extent_io_range(tree, start, end);
	trace_btrfs_set_extent_bit(tree, start, end - start + 1, bits);

	if (exclusive_bits)
		ASSERT(failed_start);
	else
		ASSERT(failed_start == NULL && failed_state == NULL);
again:
	if (!prealloc) {
		/*
		 * Don't care for allocation failure here because we might end
		 * up not needing the pre-allocated extent state at all, which
		 * is the case if we only have in the tree extent states that
		 * cover our input range and don't cover too any other range.
		 * If we end up needing a new extent state we allocate it later.
		 */
		prealloc = alloc_extent_state(mask);
	}

	spin_lock(&tree->lock);
	if (cached_state && *cached_state) {
		state = *cached_state;
		if (state->start <= start && state->end > start &&
		    extent_state_in_tree(state))
			goto hit_next;
	}
	/*
	 * This search will find all the extents that end after our range
	 * starts.
	 */
	state = tree_search_for_insert(tree, start, &p, &parent);
	if (!state) {
		prealloc = alloc_extent_state_atomic(prealloc);
		if (!prealloc)
			goto search_again;
		prealloc->start = start;
		prealloc->end = end;
		insert_state_fast(tree, prealloc, p, parent, bits, changeset);
		cache_state(prealloc, cached_state);
		prealloc = NULL;
		goto out;
	}
hit_next:
	last_start = state->start;
	last_end = state->end;

	/*
	 * | ---- desired range ---- |
	 * | state |
	 *
	 * Just lock what we found and keep going
	 */
	if (state->start == start && state->end <= end) {
		if (state->state & exclusive_bits) {
			*failed_start = state->start;
			cache_state(state, failed_state);
			err = -EEXIST;
			goto out;
		}

		set_state_bits(tree, state, bits, changeset);
		cache_state(state, cached_state);
		merge_state(tree, state);
		if (last_end == (u64)-1)
			goto out;
		start = last_end + 1;
		state = next_state(state);
		if (start < end && state && state->start == start &&
		    !need_resched())
			goto hit_next;
		goto search_again;
	}

	/*
	 *     | ---- desired range ---- |
	 * | state |
	 *   or
	 * | ------------- state -------------- |
	 *
	 * We need to split the extent we found, and may flip bits on second
	 * half.
	 *
	 * If the extent we found extends past our range, we just split and
	 * search again.  It'll get split again the next time though.
	 *
	 * If the extent we found is inside our range, we set the desired bit
	 * on it.
	 */
	if (state->start < start) {
		if (state->state & exclusive_bits) {
			*failed_start = start;
			cache_state(state, failed_state);
			err = -EEXIST;
			goto out;
		}

		/*
		 * If this extent already has all the bits we want set, then
		 * skip it, not necessary to split it or do anything with it.
		 */
		if ((state->state & bits) == bits) {
			start = state->end + 1;
			cache_state(state, cached_state);
			goto search_again;
		}

		prealloc = alloc_extent_state_atomic(prealloc);
		if (!prealloc)
			goto search_again;
		err = split_state(tree, state, prealloc, start);
		if (err)
			extent_io_tree_panic(tree, err);

		prealloc = NULL;
		if (err)
			goto out;
		if (state->end <= end) {
			set_state_bits(tree, state, bits, changeset);
			cache_state(state, cached_state);
			merge_state(tree, state);
			if (last_end == (u64)-1)
				goto out;
			start = last_end + 1;
			state = next_state(state);
			if (start < end && state && state->start == start &&
			    !need_resched())
				goto hit_next;
		}
		goto search_again;
	}
	/*
	 * | ---- desired range ---- |
	 *     | state | or               | state |
	 *
	 * There's a hole, we need to insert something in it and ignore the
	 * extent we found.
	 */
	if (state->start > start) {
		u64 this_end;
		if (end < last_start)
			this_end = end;
		else
			this_end = last_start - 1;

		prealloc = alloc_extent_state_atomic(prealloc);
		if (!prealloc)
			goto search_again;

		/*
		 * Avoid to free 'prealloc' if it can be merged with the later
		 * extent.
		 */
		prealloc->start = start;
		prealloc->end = this_end;
		err = insert_state(tree, prealloc, bits, changeset);
		if (err)
			extent_io_tree_panic(tree, err);

		cache_state(prealloc, cached_state);
		prealloc = NULL;
		start = this_end + 1;
		goto search_again;
	}
	/*
	 * | ---- desired range ---- |
	 *                        | state |
	 *
	 * We need to split the extent, and set the bit on the first half
	 */
	if (state->start <= end && state->end > end) {
		if (state->state & exclusive_bits) {
			*failed_start = start;
			cache_state(state, failed_state);
			err = -EEXIST;
			goto out;
		}

		prealloc = alloc_extent_state_atomic(prealloc);
		if (!prealloc)
			goto search_again;
		err = split_state(tree, state, prealloc, end + 1);
		if (err)
			extent_io_tree_panic(tree, err);

		set_state_bits(tree, prealloc, bits, changeset);
		cache_state(prealloc, cached_state);
		merge_state(tree, prealloc);
		prealloc = NULL;
		goto out;
	}

search_again:
	if (start > end)
		goto out;
	spin_unlock(&tree->lock);
	if (gfpflags_allow_blocking(mask))
		cond_resched();
	goto again;

out:
	spin_unlock(&tree->lock);
	if (prealloc)
		free_extent_state(prealloc);

	return err;

}

int set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
		   u32 bits, struct extent_state **cached_state)
{
	return __set_extent_bit(tree, start, end, bits, NULL, NULL,
				cached_state, NULL);
}

/*
 * Convert all bits in a given range from one bit to another
 *
 * @tree:	the io tree to search
 * @start:	the start offset in bytes
 * @end:	the end offset in bytes (inclusive)
 * @bits:	the bits to set in this range
 * @clear_bits:	the bits to clear in this range
 * @cached_state:	state that we're going to cache
 *
 * This will go through and set bits for the given range.  If any states exist
 * already in this range they are set with the given bit and cleared of the
 * clear_bits.  This is only meant to be used by things that are mergeable, ie.
 * converting from say DELALLOC to DIRTY.  This is not meant to be used with
 * boundary bits like LOCK.
 *
 * All allocations are done with GFP_NOFS.
 */
int convert_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
		       u32 bits, u32 clear_bits,
		       struct extent_state **cached_state)
{
	struct extent_state *state;
	struct extent_state *prealloc = NULL;
	struct rb_node **p = NULL;
	struct rb_node *parent = NULL;
	int err = 0;
	u64 last_start;
	u64 last_end;
	bool first_iteration = true;

	btrfs_debug_check_extent_io_range(tree, start, end);
	trace_btrfs_convert_extent_bit(tree, start, end - start + 1, bits,
				       clear_bits);

again:
	if (!prealloc) {
		/*
		 * Best effort, don't worry if extent state allocation fails
		 * here for the first iteration. We might have a cached state
		 * that matches exactly the target range, in which case no
		 * extent state allocations are needed. We'll only know this
		 * after locking the tree.
		 */
		prealloc = alloc_extent_state(GFP_NOFS);
		if (!prealloc && !first_iteration)
			return -ENOMEM;
	}

	spin_lock(&tree->lock);
	if (cached_state && *cached_state) {
		state = *cached_state;
		if (state->start <= start && state->end > start &&
		    extent_state_in_tree(state))
			goto hit_next;
	}

	/*
	 * This search will find all the extents that end after our range
	 * starts.
	 */
	state = tree_search_for_insert(tree, start, &p, &parent);
	if (!state) {
		prealloc = alloc_extent_state_atomic(prealloc);
		if (!prealloc) {
			err = -ENOMEM;
			goto out;
		}
		prealloc->start = start;
		prealloc->end = end;
		insert_state_fast(tree, prealloc, p, parent, bits, NULL);
		cache_state(prealloc, cached_state);
		prealloc = NULL;
		goto out;
	}
hit_next:
	last_start = state->start;
	last_end = state->end;

	/*
	 * | ---- desired range ---- |
	 * | state |
	 *
	 * Just lock what we found and keep going.
	 */
	if (state->start == start && state->end <= end) {
		set_state_bits(tree, state, bits, NULL);
		cache_state(state, cached_state);
		state = clear_state_bit(tree, state, clear_bits, 0, NULL);
		if (last_end == (u64)-1)
			goto out;
		start = last_end + 1;
		if (start < end && state && state->start == start &&
		    !need_resched())
			goto hit_next;
		goto search_again;
	}

	/*
	 *     | ---- desired range ---- |
	 * | state |
	 *   or
	 * | ------------- state -------------- |
	 *
	 * We need to split the extent we found, and may flip bits on second
	 * half.
	 *
	 * If the extent we found extends past our range, we just split and
	 * search again.  It'll get split again the next time though.
	 *
	 * If the extent we found is inside our range, we set the desired bit
	 * on it.
	 */
	if (state->start < start) {
		prealloc = alloc_extent_state_atomic(prealloc);
		if (!prealloc) {
			err = -ENOMEM;
			goto out;
		}
		err = split_state(tree, state, prealloc, start);
		if (err)
			extent_io_tree_panic(tree, err);
		prealloc = NULL;
		if (err)
			goto out;
		if (state->end <= end) {
			set_state_bits(tree, state, bits, NULL);
			cache_state(state, cached_state);
			state = clear_state_bit(tree, state, clear_bits, 0, NULL);
			if (last_end == (u64)-1)
				goto out;
			start = last_end + 1;
			if (start < end && state && state->start == start &&
			    !need_resched())
				goto hit_next;
		}
		goto search_again;
	}
	/*
	 * | ---- desired range ---- |
	 *     | state | or               | state |
	 *
	 * There's a hole, we need to insert something in it and ignore the
	 * extent we found.
	 */
	if (state->start > start) {
		u64 this_end;
		if (end < last_start)
			this_end = end;
		else
			this_end = last_start - 1;

		prealloc = alloc_extent_state_atomic(prealloc);
		if (!prealloc) {
			err = -ENOMEM;
			goto out;
		}

		/*
		 * Avoid to free 'prealloc' if it can be merged with the later
		 * extent.
		 */
		prealloc->start = start;
		prealloc->end = this_end;
		err = insert_state(tree, prealloc, bits, NULL);
		if (err)
			extent_io_tree_panic(tree, err);
		cache_state(prealloc, cached_state);
		prealloc = NULL;
		start = this_end + 1;
		goto search_again;
	}
	/*
	 * | ---- desired range ---- |
	 *                        | state |
	 *
	 * We need to split the extent, and set the bit on the first half.
	 */
	if (state->start <= end && state->end > end) {
		prealloc = alloc_extent_state_atomic(prealloc);
		if (!prealloc) {
			err = -ENOMEM;
			goto out;
		}

		err = split_state(tree, state, prealloc, end + 1);
		if (err)
			extent_io_tree_panic(tree, err);

		set_state_bits(tree, prealloc, bits, NULL);
		cache_state(prealloc, cached_state);
		clear_state_bit(tree, prealloc, clear_bits, 0, NULL);
		prealloc = NULL;
		goto out;
	}

search_again:
	if (start > end)
		goto out;
	spin_unlock(&tree->lock);
	cond_resched();
	first_iteration = false;
	goto again;

out:
	spin_unlock(&tree->lock);
	if (prealloc)
		free_extent_state(prealloc);

	return err;
}

/*
 * Find the first range that has @bits not set. This range could start before
 * @start.
 *
 * @tree:      the tree to search
 * @start:     offset at/after which the found extent should start
 * @start_ret: records the beginning of the range
 * @end_ret:   records the end of the range (inclusive)
 * @bits:      the set of bits which must be unset
 *
 * Since unallocated range is also considered one which doesn't have the bits
 * set it's possible that @end_ret contains -1, this happens in case the range
 * spans (last_range_end, end of device]. In this case it's up to the caller to
 * trim @end_ret to the appropriate size.
 */
void find_first_clear_extent_bit(struct extent_io_tree *tree, u64 start,
				 u64 *start_ret, u64 *end_ret, u32 bits)
{
	struct extent_state *state;
	struct extent_state *prev = NULL, *next = NULL;

	spin_lock(&tree->lock);

	/* Find first extent with bits cleared */
	while (1) {
		state = tree_search_prev_next(tree, start, &prev, &next);
		if (!state && !next && !prev) {
			/*
			 * Tree is completely empty, send full range and let
			 * caller deal with it
			 */
			*start_ret = 0;
			*end_ret = -1;
			goto out;
		} else if (!state && !next) {
			/*
			 * We are past the last allocated chunk, set start at
			 * the end of the last extent.
			 */
			*start_ret = prev->end + 1;
			*end_ret = -1;
			goto out;
		} else if (!state) {
			state = next;
		}

		/*
		 * At this point 'state' either contains 'start' or start is
		 * before 'state'
		 */
		if (in_range(start, state->start, state->end - state->start + 1)) {
			if (state->state & bits) {
				/*
				 * |--range with bits sets--|
				 *    |
				 *    start
				 */
				start = state->end + 1;
			} else {
				/*
				 * 'start' falls within a range that doesn't
				 * have the bits set, so take its start as the
				 * beginning of the desired range
				 *
				 * |--range with bits cleared----|
				 *      |
				 *      start
				 */
				*start_ret = state->start;
				break;
			}
		} else {
			/*
			 * |---prev range---|---hole/unset---|---node range---|
			 *                          |
			 *                        start
			 *
			 *                        or
			 *
			 * |---hole/unset--||--first node--|
			 * 0   |
			 *    start
			 */
			if (prev)
				*start_ret = prev->end + 1;
			else
				*start_ret = 0;
			break;
		}
	}

	/*
	 * Find the longest stretch from start until an entry which has the
	 * bits set
	 */
	while (state) {
		if (state->end >= start && !(state->state & bits)) {
			*end_ret = state->end;
		} else {
			*end_ret = state->start - 1;
			break;
		}
		state = next_state(state);
	}
out:
	spin_unlock(&tree->lock);
}

/*
 * Count the number of bytes in the tree that have a given bit(s) set for a
 * given range.
 *
 * @tree:         The io tree to search.
 * @start:        The start offset of the range. This value is updated to the
 *                offset of the first byte found with the given bit(s), so it
 *                can end up being bigger than the initial value.
 * @search_end:   The end offset (inclusive value) of the search range.
 * @max_bytes:    The maximum byte count we are interested. The search stops
 *                once it reaches this count.
 * @bits:         The bits the range must have in order to be accounted for.
 *                If multiple bits are set, then only subranges that have all
 *                the bits set are accounted for.
 * @contig:       Indicate if we should ignore holes in the range or not. If
 *                this is true, then stop once we find a hole.
 * @cached_state: A cached state to be used across multiple calls to this
 *                function in order to speedup searches. Use NULL if this is
 *                called only once or if each call does not start where the
 *                previous one ended.
 *
 * Returns the total number of bytes found within the given range that have
 * all given bits set. If the returned number of bytes is greater than zero
 * then @start is updated with the offset of the first byte with the bits set.
 */
u64 count_range_bits(struct extent_io_tree *tree,
		     u64 *start, u64 search_end, u64 max_bytes,
		     u32 bits, int contig,
		     struct extent_state **cached_state)
{
	struct extent_state *state = NULL;
	struct extent_state *cached;
	u64 cur_start = *start;
	u64 total_bytes = 0;
	u64 last = 0;
	int found = 0;

	if (WARN_ON(search_end < cur_start))
		return 0;

	spin_lock(&tree->lock);

	if (!cached_state || !*cached_state)
		goto search;

	cached = *cached_state;

	if (!extent_state_in_tree(cached))
		goto search;

	if (cached->start <= cur_start && cur_start <= cached->end) {
		state = cached;
	} else if (cached->start > cur_start) {
		struct extent_state *prev;

		/*
		 * The cached state starts after our search range's start. Check
		 * if the previous state record starts at or before the range we
		 * are looking for, and if so, use it - this is a common case
		 * when there are holes between records in the tree. If there is
		 * no previous state record, we can start from our cached state.
		 */
		prev = prev_state(cached);
		if (!prev)
			state = cached;
		else if (prev->start <= cur_start && cur_start <= prev->end)
			state = prev;
	}

	/*
	 * This search will find all the extents that end after our range
	 * starts.
	 */
search:
	if (!state)
		state = tree_search(tree, cur_start);

	while (state) {
		if (state->start > search_end)
			break;
		if (contig && found && state->start > last + 1)
			break;
		if (state->end >= cur_start && (state->state & bits) == bits) {
			total_bytes += min(search_end, state->end) + 1 -
				       max(cur_start, state->start);
			if (total_bytes >= max_bytes)
				break;
			if (!found) {
				*start = max(cur_start, state->start);
				found = 1;
			}
			last = state->end;
		} else if (contig && found) {
			break;
		}
		state = next_state(state);
	}

	if (cached_state) {
		free_extent_state(*cached_state);
		*cached_state = state;
		if (state)
			refcount_inc(&state->refs);
	}

	spin_unlock(&tree->lock);

	return total_bytes;
}

/*
 * Search a range in the state tree for a given mask.  If 'filled' == 1, this
 * returns 1 only if every extent in the tree has the bits set.  Otherwise, 1
 * is returned if any bit in the range is found set.
 */
int test_range_bit(struct extent_io_tree *tree, u64 start, u64 end,
		   u32 bits, int filled, struct extent_state *cached)
{
	struct extent_state *state = NULL;
	int bitset = 0;

	spin_lock(&tree->lock);
	if (cached && extent_state_in_tree(cached) && cached->start <= start &&
	    cached->end > start)
		state = cached;
	else
		state = tree_search(tree, start);
	while (state && start <= end) {
		if (filled && state->start > start) {
			bitset = 0;
			break;
		}

		if (state->start > end)
			break;

		if (state->state & bits) {
			bitset = 1;
			if (!filled)
				break;
		} else if (filled) {
			bitset = 0;
			break;
		}

		if (state->end == (u64)-1)
			break;

		start = state->end + 1;
		if (start > end)
			break;
		state = next_state(state);
	}

	/* We ran out of states and were still inside of our range. */
	if (filled && !state)
		bitset = 0;
	spin_unlock(&tree->lock);
	return bitset;
}

/* Wrappers around set/clear extent bit */
int set_record_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
			   u32 bits, struct extent_changeset *changeset)
{
	/*
	 * We don't support EXTENT_LOCKED yet, as current changeset will
	 * record any bits changed, so for EXTENT_LOCKED case, it will
	 * either fail with -EEXIST or changeset will record the whole
	 * range.
	 */
	ASSERT(!(bits & EXTENT_LOCKED));

	return __set_extent_bit(tree, start, end, bits, NULL, NULL, NULL, changeset);
}

int clear_record_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
			     u32 bits, struct extent_changeset *changeset)
{
	/*
	 * Don't support EXTENT_LOCKED case, same reason as
	 * set_record_extent_bits().
	 */
	ASSERT(!(bits & EXTENT_LOCKED));

	return __clear_extent_bit(tree, start, end, bits, NULL, changeset);
}

int try_lock_extent(struct extent_io_tree *tree, u64 start, u64 end,
		    struct extent_state **cached)
{
	int err;
	u64 failed_start;

	err = __set_extent_bit(tree, start, end, EXTENT_LOCKED, &failed_start,
			       NULL, cached, NULL);
	if (err == -EEXIST) {
		if (failed_start > start)
			clear_extent_bit(tree, start, failed_start - 1,
					 EXTENT_LOCKED, cached);
		return 0;
	}
	return 1;
}

/*
 * Either insert or lock state struct between start and end use mask to tell
 * us if waiting is desired.
 */
int lock_extent(struct extent_io_tree *tree, u64 start, u64 end,
		struct extent_state **cached_state)
{
	struct extent_state *failed_state = NULL;
	int err;
	u64 failed_start;

	err = __set_extent_bit(tree, start, end, EXTENT_LOCKED, &failed_start,
			       &failed_state, cached_state, NULL);
	while (err == -EEXIST) {
		if (failed_start != start)
			clear_extent_bit(tree, start, failed_start - 1,
					 EXTENT_LOCKED, cached_state);

		wait_extent_bit(tree, failed_start, end, EXTENT_LOCKED,
				&failed_state);
		err = __set_extent_bit(tree, start, end, EXTENT_LOCKED,
				       &failed_start, &failed_state,
				       cached_state, NULL);
	}
	return err;
}

void __cold extent_state_free_cachep(void)
{
	btrfs_extent_state_leak_debug_check();
	kmem_cache_destroy(extent_state_cache);
}

int __init extent_state_init_cachep(void)
{
	extent_state_cache = kmem_cache_create("btrfs_extent_state",
			sizeof(struct extent_state), 0,
			SLAB_MEM_SPREAD, NULL);
	if (!extent_state_cache)
		return -ENOMEM;

	return 0;
}