summaryrefslogtreecommitdiff
path: root/fs/btrfs/space-info.c
blob: ae8c56442549c737da754778f1c1866a8f8ddd07 (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
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
// SPDX-License-Identifier: GPL-2.0

#include "misc.h"
#include "ctree.h"
#include "space-info.h"
#include "sysfs.h"
#include "volumes.h"
#include "free-space-cache.h"
#include "ordered-data.h"
#include "transaction.h"
#include "block-group.h"
#include "fs.h"
#include "accessors.h"
#include "extent-tree.h"

/*
 * HOW DOES SPACE RESERVATION WORK
 *
 * If you want to know about delalloc specifically, there is a separate comment
 * for that with the delalloc code.  This comment is about how the whole system
 * works generally.
 *
 * BASIC CONCEPTS
 *
 *   1) space_info.  This is the ultimate arbiter of how much space we can use.
 *   There's a description of the bytes_ fields with the struct declaration,
 *   refer to that for specifics on each field.  Suffice it to say that for
 *   reservations we care about total_bytes - SUM(space_info->bytes_) when
 *   determining if there is space to make an allocation.  There is a space_info
 *   for METADATA, SYSTEM, and DATA areas.
 *
 *   2) block_rsv's.  These are basically buckets for every different type of
 *   metadata reservation we have.  You can see the comment in the block_rsv
 *   code on the rules for each type, but generally block_rsv->reserved is how
 *   much space is accounted for in space_info->bytes_may_use.
 *
 *   3) btrfs_calc*_size.  These are the worst case calculations we used based
 *   on the number of items we will want to modify.  We have one for changing
 *   items, and one for inserting new items.  Generally we use these helpers to
 *   determine the size of the block reserves, and then use the actual bytes
 *   values to adjust the space_info counters.
 *
 * MAKING RESERVATIONS, THE NORMAL CASE
 *
 *   We call into either btrfs_reserve_data_bytes() or
 *   btrfs_reserve_metadata_bytes(), depending on which we're looking for, with
 *   num_bytes we want to reserve.
 *
 *   ->reserve
 *     space_info->bytes_may_reserve += num_bytes
 *
 *   ->extent allocation
 *     Call btrfs_add_reserved_bytes() which does
 *     space_info->bytes_may_reserve -= num_bytes
 *     space_info->bytes_reserved += extent_bytes
 *
 *   ->insert reference
 *     Call btrfs_update_block_group() which does
 *     space_info->bytes_reserved -= extent_bytes
 *     space_info->bytes_used += extent_bytes
 *
 * MAKING RESERVATIONS, FLUSHING NORMALLY (non-priority)
 *
 *   Assume we are unable to simply make the reservation because we do not have
 *   enough space
 *
 *   -> __reserve_bytes
 *     create a reserve_ticket with ->bytes set to our reservation, add it to
 *     the tail of space_info->tickets, kick async flush thread
 *
 *   ->handle_reserve_ticket
 *     wait on ticket->wait for ->bytes to be reduced to 0, or ->error to be set
 *     on the ticket.
 *
 *   -> btrfs_async_reclaim_metadata_space/btrfs_async_reclaim_data_space
 *     Flushes various things attempting to free up space.
 *
 *   -> btrfs_try_granting_tickets()
 *     This is called by anything that either subtracts space from
 *     space_info->bytes_may_use, ->bytes_pinned, etc, or adds to the
 *     space_info->total_bytes.  This loops through the ->priority_tickets and
 *     then the ->tickets list checking to see if the reservation can be
 *     completed.  If it can the space is added to space_info->bytes_may_use and
 *     the ticket is woken up.
 *
 *   -> ticket wakeup
 *     Check if ->bytes == 0, if it does we got our reservation and we can carry
 *     on, if not return the appropriate error (ENOSPC, but can be EINTR if we
 *     were interrupted.)
 *
 * MAKING RESERVATIONS, FLUSHING HIGH PRIORITY
 *
 *   Same as the above, except we add ourselves to the
 *   space_info->priority_tickets, and we do not use ticket->wait, we simply
 *   call flush_space() ourselves for the states that are safe for us to call
 *   without deadlocking and hope for the best.
 *
 * THE FLUSHING STATES
 *
 *   Generally speaking we will have two cases for each state, a "nice" state
 *   and a "ALL THE THINGS" state.  In btrfs we delay a lot of work in order to
 *   reduce the locking over head on the various trees, and even to keep from
 *   doing any work at all in the case of delayed refs.  Each of these delayed
 *   things however hold reservations, and so letting them run allows us to
 *   reclaim space so we can make new reservations.
 *
 *   FLUSH_DELAYED_ITEMS
 *     Every inode has a delayed item to update the inode.  Take a simple write
 *     for example, we would update the inode item at write time to update the
 *     mtime, and then again at finish_ordered_io() time in order to update the
 *     isize or bytes.  We keep these delayed items to coalesce these operations
 *     into a single operation done on demand.  These are an easy way to reclaim
 *     metadata space.
 *
 *   FLUSH_DELALLOC
 *     Look at the delalloc comment to get an idea of how much space is reserved
 *     for delayed allocation.  We can reclaim some of this space simply by
 *     running delalloc, but usually we need to wait for ordered extents to
 *     reclaim the bulk of this space.
 *
 *   FLUSH_DELAYED_REFS
 *     We have a block reserve for the outstanding delayed refs space, and every
 *     delayed ref operation holds a reservation.  Running these is a quick way
 *     to reclaim space, but we want to hold this until the end because COW can
 *     churn a lot and we can avoid making some extent tree modifications if we
 *     are able to delay for as long as possible.
 *
 *   ALLOC_CHUNK
 *     We will skip this the first time through space reservation, because of
 *     overcommit and we don't want to have a lot of useless metadata space when
 *     our worst case reservations will likely never come true.
 *
 *   RUN_DELAYED_IPUTS
 *     If we're freeing inodes we're likely freeing checksums, file extent
 *     items, and extent tree items.  Loads of space could be freed up by these
 *     operations, however they won't be usable until the transaction commits.
 *
 *   COMMIT_TRANS
 *     This will commit the transaction.  Historically we had a lot of logic
 *     surrounding whether or not we'd commit the transaction, but this waits born
 *     out of a pre-tickets era where we could end up committing the transaction
 *     thousands of times in a row without making progress.  Now thanks to our
 *     ticketing system we know if we're not making progress and can error
 *     everybody out after a few commits rather than burning the disk hoping for
 *     a different answer.
 *
 * OVERCOMMIT
 *
 *   Because we hold so many reservations for metadata we will allow you to
 *   reserve more space than is currently free in the currently allocate
 *   metadata space.  This only happens with metadata, data does not allow
 *   overcommitting.
 *
 *   You can see the current logic for when we allow overcommit in
 *   btrfs_can_overcommit(), but it only applies to unallocated space.  If there
 *   is no unallocated space to be had, all reservations are kept within the
 *   free space in the allocated metadata chunks.
 *
 *   Because of overcommitting, you generally want to use the
 *   btrfs_can_overcommit() logic for metadata allocations, as it does the right
 *   thing with or without extra unallocated space.
 */

u64 __pure btrfs_space_info_used(struct btrfs_space_info *s_info,
			  bool may_use_included)
{
	ASSERT(s_info);
	return s_info->bytes_used + s_info->bytes_reserved +
		s_info->bytes_pinned + s_info->bytes_readonly +
		s_info->bytes_zone_unusable +
		(may_use_included ? s_info->bytes_may_use : 0);
}

/*
 * after adding space to the filesystem, we need to clear the full flags
 * on all the space infos.
 */
void btrfs_clear_space_info_full(struct btrfs_fs_info *info)
{
	struct list_head *head = &info->space_info;
	struct btrfs_space_info *found;

	list_for_each_entry(found, head, list)
		found->full = 0;
}

/*
 * Block groups with more than this value (percents) of unusable space will be
 * scheduled for background reclaim.
 */
#define BTRFS_DEFAULT_ZONED_RECLAIM_THRESH			(75)

/*
 * Calculate chunk size depending on volume type (regular or zoned).
 */
static u64 calc_chunk_size(const struct btrfs_fs_info *fs_info, u64 flags)
{
	if (btrfs_is_zoned(fs_info))
		return fs_info->zone_size;

	ASSERT(flags & BTRFS_BLOCK_GROUP_TYPE_MASK);

	if (flags & BTRFS_BLOCK_GROUP_DATA)
		return BTRFS_MAX_DATA_CHUNK_SIZE;
	else if (flags & BTRFS_BLOCK_GROUP_SYSTEM)
		return SZ_32M;

	/* Handle BTRFS_BLOCK_GROUP_METADATA */
	if (fs_info->fs_devices->total_rw_bytes > 50ULL * SZ_1G)
		return SZ_1G;

	return SZ_256M;
}

/*
 * Update default chunk size.
 */
void btrfs_update_space_info_chunk_size(struct btrfs_space_info *space_info,
					u64 chunk_size)
{
	WRITE_ONCE(space_info->chunk_size, chunk_size);
}

static int create_space_info(struct btrfs_fs_info *info, u64 flags)
{

	struct btrfs_space_info *space_info;
	int i;
	int ret;

	space_info = kzalloc(sizeof(*space_info), GFP_NOFS);
	if (!space_info)
		return -ENOMEM;

	for (i = 0; i < BTRFS_NR_RAID_TYPES; i++)
		INIT_LIST_HEAD(&space_info->block_groups[i]);
	init_rwsem(&space_info->groups_sem);
	spin_lock_init(&space_info->lock);
	space_info->flags = flags & BTRFS_BLOCK_GROUP_TYPE_MASK;
	space_info->force_alloc = CHUNK_ALLOC_NO_FORCE;
	INIT_LIST_HEAD(&space_info->ro_bgs);
	INIT_LIST_HEAD(&space_info->tickets);
	INIT_LIST_HEAD(&space_info->priority_tickets);
	space_info->clamp = 1;
	btrfs_update_space_info_chunk_size(space_info, calc_chunk_size(info, flags));

	if (btrfs_is_zoned(info))
		space_info->bg_reclaim_threshold = BTRFS_DEFAULT_ZONED_RECLAIM_THRESH;

	ret = btrfs_sysfs_add_space_info_type(info, space_info);
	if (ret)
		return ret;

	list_add(&space_info->list, &info->space_info);
	if (flags & BTRFS_BLOCK_GROUP_DATA)
		info->data_sinfo = space_info;

	return ret;
}

int btrfs_init_space_info(struct btrfs_fs_info *fs_info)
{
	struct btrfs_super_block *disk_super;
	u64 features;
	u64 flags;
	int mixed = 0;
	int ret;

	disk_super = fs_info->super_copy;
	if (!btrfs_super_root(disk_super))
		return -EINVAL;

	features = btrfs_super_incompat_flags(disk_super);
	if (features & BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS)
		mixed = 1;

	flags = BTRFS_BLOCK_GROUP_SYSTEM;
	ret = create_space_info(fs_info, flags);
	if (ret)
		goto out;

	if (mixed) {
		flags = BTRFS_BLOCK_GROUP_METADATA | BTRFS_BLOCK_GROUP_DATA;
		ret = create_space_info(fs_info, flags);
	} else {
		flags = BTRFS_BLOCK_GROUP_METADATA;
		ret = create_space_info(fs_info, flags);
		if (ret)
			goto out;

		flags = BTRFS_BLOCK_GROUP_DATA;
		ret = create_space_info(fs_info, flags);
	}
out:
	return ret;
}

void btrfs_add_bg_to_space_info(struct btrfs_fs_info *info,
				struct btrfs_block_group *block_group)
{
	struct btrfs_space_info *found;
	int factor, index;

	factor = btrfs_bg_type_to_factor(block_group->flags);

	found = btrfs_find_space_info(info, block_group->flags);
	ASSERT(found);
	spin_lock(&found->lock);
	found->total_bytes += block_group->length;
	found->disk_total += block_group->length * factor;
	found->bytes_used += block_group->used;
	found->disk_used += block_group->used * factor;
	found->bytes_readonly += block_group->bytes_super;
	found->bytes_zone_unusable += block_group->zone_unusable;
	if (block_group->length > 0)
		found->full = 0;
	btrfs_try_granting_tickets(info, found);
	spin_unlock(&found->lock);

	block_group->space_info = found;

	index = btrfs_bg_flags_to_raid_index(block_group->flags);
	down_write(&found->groups_sem);
	list_add_tail(&block_group->list, &found->block_groups[index]);
	up_write(&found->groups_sem);
}

struct btrfs_space_info *btrfs_find_space_info(struct btrfs_fs_info *info,
					       u64 flags)
{
	struct list_head *head = &info->space_info;
	struct btrfs_space_info *found;

	flags &= BTRFS_BLOCK_GROUP_TYPE_MASK;

	list_for_each_entry(found, head, list) {
		if (found->flags & flags)
			return found;
	}
	return NULL;
}

static u64 calc_available_free_space(struct btrfs_fs_info *fs_info,
			  struct btrfs_space_info *space_info,
			  enum btrfs_reserve_flush_enum flush)
{
	struct btrfs_space_info *data_sinfo;
	u64 profile;
	u64 avail;
	u64 data_chunk_size;
	int factor;

	if (space_info->flags & BTRFS_BLOCK_GROUP_SYSTEM)
		profile = btrfs_system_alloc_profile(fs_info);
	else
		profile = btrfs_metadata_alloc_profile(fs_info);

	avail = atomic64_read(&fs_info->free_chunk_space);

	/*
	 * If we have dup, raid1 or raid10 then only half of the free
	 * space is actually usable.  For raid56, the space info used
	 * doesn't include the parity drive, so we don't have to
	 * change the math
	 */
	factor = btrfs_bg_type_to_factor(profile);
	avail = div_u64(avail, factor);
	if (avail == 0)
		return 0;

	/*
	 * Calculate the data_chunk_size, space_info->chunk_size is the
	 * "optimal" chunk size based on the fs size.  However when we actually
	 * allocate the chunk we will strip this down further, making it no more
	 * than 10% of the disk or 1G, whichever is smaller.
	 *
	 * On the zoned mode, we need to use zone_size (=
	 * data_sinfo->chunk_size) as it is.
	 */
	data_sinfo = btrfs_find_space_info(fs_info, BTRFS_BLOCK_GROUP_DATA);
	if (!btrfs_is_zoned(fs_info)) {
		data_chunk_size = min(data_sinfo->chunk_size,
				      mult_perc(fs_info->fs_devices->total_rw_bytes, 10));
		data_chunk_size = min_t(u64, data_chunk_size, SZ_1G);
	} else {
		data_chunk_size = data_sinfo->chunk_size;
	}

	/*
	 * Since data allocations immediately use block groups as part of the
	 * reservation, because we assume that data reservations will == actual
	 * usage, we could potentially overcommit and then immediately have that
	 * available space used by a data allocation, which could put us in a
	 * bind when we get close to filling the file system.
	 *
	 * To handle this simply remove the data_chunk_size from the available
	 * space.  If we are relatively empty this won't affect our ability to
	 * overcommit much, and if we're very close to full it'll keep us from
	 * getting into a position where we've given ourselves very little
	 * metadata wiggle room.
	 */
	if (avail <= data_chunk_size)
		return 0;
	avail -= data_chunk_size;

	/*
	 * If we aren't flushing all things, let us overcommit up to
	 * 1/2th of the space. If we can flush, don't let us overcommit
	 * too much, let it overcommit up to 1/8 of the space.
	 */
	if (flush == BTRFS_RESERVE_FLUSH_ALL)
		avail >>= 3;
	else
		avail >>= 1;

	/*
	 * On the zoned mode, we always allocate one zone as one chunk.
	 * Returning non-zone size alingned bytes here will result in
	 * less pressure for the async metadata reclaim process, and it
	 * will over-commit too much leading to ENOSPC. Align down to the
	 * zone size to avoid that.
	 */
	if (btrfs_is_zoned(fs_info))
		avail = ALIGN_DOWN(avail, fs_info->zone_size);

	return avail;
}

int btrfs_can_overcommit(struct btrfs_fs_info *fs_info,
			 struct btrfs_space_info *space_info, u64 bytes,
			 enum btrfs_reserve_flush_enum flush)
{
	u64 avail;
	u64 used;

	/* Don't overcommit when in mixed mode */
	if (space_info->flags & BTRFS_BLOCK_GROUP_DATA)
		return 0;

	used = btrfs_space_info_used(space_info, true);
	avail = calc_available_free_space(fs_info, space_info, flush);

	if (used + bytes < space_info->total_bytes + avail)
		return 1;
	return 0;
}

static void remove_ticket(struct btrfs_space_info *space_info,
			  struct reserve_ticket *ticket)
{
	if (!list_empty(&ticket->list)) {
		list_del_init(&ticket->list);
		ASSERT(space_info->reclaim_size >= ticket->bytes);
		space_info->reclaim_size -= ticket->bytes;
	}
}

/*
 * This is for space we already have accounted in space_info->bytes_may_use, so
 * basically when we're returning space from block_rsv's.
 */
void btrfs_try_granting_tickets(struct btrfs_fs_info *fs_info,
				struct btrfs_space_info *space_info)
{
	struct list_head *head;
	enum btrfs_reserve_flush_enum flush = BTRFS_RESERVE_NO_FLUSH;

	lockdep_assert_held(&space_info->lock);

	head = &space_info->priority_tickets;
again:
	while (!list_empty(head)) {
		struct reserve_ticket *ticket;
		u64 used = btrfs_space_info_used(space_info, true);

		ticket = list_first_entry(head, struct reserve_ticket, list);

		/* Check and see if our ticket can be satisfied now. */
		if ((used + ticket->bytes <= space_info->total_bytes) ||
		    btrfs_can_overcommit(fs_info, space_info, ticket->bytes,
					 flush)) {
			btrfs_space_info_update_bytes_may_use(fs_info,
							      space_info,
							      ticket->bytes);
			remove_ticket(space_info, ticket);
			ticket->bytes = 0;
			space_info->tickets_id++;
			wake_up(&ticket->wait);
		} else {
			break;
		}
	}

	if (head == &space_info->priority_tickets) {
		head = &space_info->tickets;
		flush = BTRFS_RESERVE_FLUSH_ALL;
		goto again;
	}
}

#define DUMP_BLOCK_RSV(fs_info, rsv_name)				\
do {									\
	struct btrfs_block_rsv *__rsv = &(fs_info)->rsv_name;		\
	spin_lock(&__rsv->lock);					\
	btrfs_info(fs_info, #rsv_name ": size %llu reserved %llu",	\
		   __rsv->size, __rsv->reserved);			\
	spin_unlock(&__rsv->lock);					\
} while (0)

static const char *space_info_flag_to_str(const struct btrfs_space_info *space_info)
{
	switch (space_info->flags) {
	case BTRFS_BLOCK_GROUP_SYSTEM:
		return "SYSTEM";
	case BTRFS_BLOCK_GROUP_METADATA | BTRFS_BLOCK_GROUP_DATA:
		return "DATA+METADATA";
	case BTRFS_BLOCK_GROUP_DATA:
		return "DATA";
	case BTRFS_BLOCK_GROUP_METADATA:
		return "METADATA";
	default:
		return "UNKNOWN";
	}
}

static void dump_global_block_rsv(struct btrfs_fs_info *fs_info)
{
	DUMP_BLOCK_RSV(fs_info, global_block_rsv);
	DUMP_BLOCK_RSV(fs_info, trans_block_rsv);
	DUMP_BLOCK_RSV(fs_info, chunk_block_rsv);
	DUMP_BLOCK_RSV(fs_info, delayed_block_rsv);
	DUMP_BLOCK_RSV(fs_info, delayed_refs_rsv);
}

static void __btrfs_dump_space_info(struct btrfs_fs_info *fs_info,
				    struct btrfs_space_info *info)
{
	const char *flag_str = space_info_flag_to_str(info);
	lockdep_assert_held(&info->lock);

	/* The free space could be negative in case of overcommit */
	btrfs_info(fs_info, "space_info %s has %lld free, is %sfull",
		   flag_str,
		   (s64)(info->total_bytes - btrfs_space_info_used(info, true)),
		   info->full ? "" : "not ");
	btrfs_info(fs_info,
"space_info total=%llu, used=%llu, pinned=%llu, reserved=%llu, may_use=%llu, readonly=%llu zone_unusable=%llu",
		info->total_bytes, info->bytes_used, info->bytes_pinned,
		info->bytes_reserved, info->bytes_may_use,
		info->bytes_readonly, info->bytes_zone_unusable);
}

void btrfs_dump_space_info(struct btrfs_fs_info *fs_info,
			   struct btrfs_space_info *info, u64 bytes,
			   int dump_block_groups)
{
	struct btrfs_block_group *cache;
	u64 total_avail = 0;
	int index = 0;

	spin_lock(&info->lock);
	__btrfs_dump_space_info(fs_info, info);
	dump_global_block_rsv(fs_info);
	spin_unlock(&info->lock);

	if (!dump_block_groups)
		return;

	down_read(&info->groups_sem);
again:
	list_for_each_entry(cache, &info->block_groups[index], list) {
		u64 avail;

		spin_lock(&cache->lock);
		avail = cache->length - cache->used - cache->pinned -
			cache->reserved - cache->delalloc_bytes -
			cache->bytes_super - cache->zone_unusable;
		btrfs_info(fs_info,
"block group %llu has %llu bytes, %llu used %llu pinned %llu reserved %llu delalloc %llu super %llu zone_unusable (%llu bytes available) %s",
			   cache->start, cache->length, cache->used, cache->pinned,
			   cache->reserved, cache->delalloc_bytes,
			   cache->bytes_super, cache->zone_unusable,
			   avail, cache->ro ? "[readonly]" : "");
		spin_unlock(&cache->lock);
		btrfs_dump_free_space(cache, bytes);
		total_avail += avail;
	}
	if (++index < BTRFS_NR_RAID_TYPES)
		goto again;
	up_read(&info->groups_sem);

	btrfs_info(fs_info, "%llu bytes available across all block groups", total_avail);
}

static inline u64 calc_reclaim_items_nr(const struct btrfs_fs_info *fs_info,
					u64 to_reclaim)
{
	u64 bytes;
	u64 nr;

	bytes = btrfs_calc_insert_metadata_size(fs_info, 1);
	nr = div64_u64(to_reclaim, bytes);
	if (!nr)
		nr = 1;
	return nr;
}

#define EXTENT_SIZE_PER_ITEM	SZ_256K

/*
 * shrink metadata reservation for delalloc
 */
static void shrink_delalloc(struct btrfs_fs_info *fs_info,
			    struct btrfs_space_info *space_info,
			    u64 to_reclaim, bool wait_ordered,
			    bool for_preempt)
{
	struct btrfs_trans_handle *trans;
	u64 delalloc_bytes;
	u64 ordered_bytes;
	u64 items;
	long time_left;
	int loops;

	delalloc_bytes = percpu_counter_sum_positive(&fs_info->delalloc_bytes);
	ordered_bytes = percpu_counter_sum_positive(&fs_info->ordered_bytes);
	if (delalloc_bytes == 0 && ordered_bytes == 0)
		return;

	/* Calc the number of the pages we need flush for space reservation */
	if (to_reclaim == U64_MAX) {
		items = U64_MAX;
	} else {
		/*
		 * to_reclaim is set to however much metadata we need to
		 * reclaim, but reclaiming that much data doesn't really track
		 * exactly.  What we really want to do is reclaim full inode's
		 * worth of reservations, however that's not available to us
		 * here.  We will take a fraction of the delalloc bytes for our
		 * flushing loops and hope for the best.  Delalloc will expand
		 * the amount we write to cover an entire dirty extent, which
		 * will reclaim the metadata reservation for that range.  If
		 * it's not enough subsequent flush stages will be more
		 * aggressive.
		 */
		to_reclaim = max(to_reclaim, delalloc_bytes >> 3);
		items = calc_reclaim_items_nr(fs_info, to_reclaim) * 2;
	}

	trans = current->journal_info;

	/*
	 * If we are doing more ordered than delalloc we need to just wait on
	 * ordered extents, otherwise we'll waste time trying to flush delalloc
	 * that likely won't give us the space back we need.
	 */
	if (ordered_bytes > delalloc_bytes && !for_preempt)
		wait_ordered = true;

	loops = 0;
	while ((delalloc_bytes || ordered_bytes) && loops < 3) {
		u64 temp = min(delalloc_bytes, to_reclaim) >> PAGE_SHIFT;
		long nr_pages = min_t(u64, temp, LONG_MAX);
		int async_pages;

		btrfs_start_delalloc_roots(fs_info, nr_pages, true);

		/*
		 * We need to make sure any outstanding async pages are now
		 * processed before we continue.  This is because things like
		 * sync_inode() try to be smart and skip writing if the inode is
		 * marked clean.  We don't use filemap_fwrite for flushing
		 * because we want to control how many pages we write out at a
		 * time, thus this is the only safe way to make sure we've
		 * waited for outstanding compressed workers to have started
		 * their jobs and thus have ordered extents set up properly.
		 *
		 * This exists because we do not want to wait for each
		 * individual inode to finish its async work, we simply want to
		 * start the IO on everybody, and then come back here and wait
		 * for all of the async work to catch up.  Once we're done with
		 * that we know we'll have ordered extents for everything and we
		 * can decide if we wait for that or not.
		 *
		 * If we choose to replace this in the future, make absolutely
		 * sure that the proper waiting is being done in the async case,
		 * as there have been bugs in that area before.
		 */
		async_pages = atomic_read(&fs_info->async_delalloc_pages);
		if (!async_pages)
			goto skip_async;

		/*
		 * We don't want to wait forever, if we wrote less pages in this
		 * loop than we have outstanding, only wait for that number of
		 * pages, otherwise we can wait for all async pages to finish
		 * before continuing.
		 */
		if (async_pages > nr_pages)
			async_pages -= nr_pages;
		else
			async_pages = 0;
		wait_event(fs_info->async_submit_wait,
			   atomic_read(&fs_info->async_delalloc_pages) <=
			   async_pages);
skip_async:
		loops++;
		if (wait_ordered && !trans) {
			btrfs_wait_ordered_roots(fs_info, items, 0, (u64)-1);
		} else {
			time_left = schedule_timeout_killable(1);
			if (time_left)
				break;
		}

		/*
		 * If we are for preemption we just want a one-shot of delalloc
		 * flushing so we can stop flushing if we decide we don't need
		 * to anymore.
		 */
		if (for_preempt)
			break;

		spin_lock(&space_info->lock);
		if (list_empty(&space_info->tickets) &&
		    list_empty(&space_info->priority_tickets)) {
			spin_unlock(&space_info->lock);
			break;
		}
		spin_unlock(&space_info->lock);

		delalloc_bytes = percpu_counter_sum_positive(
						&fs_info->delalloc_bytes);
		ordered_bytes = percpu_counter_sum_positive(
						&fs_info->ordered_bytes);
	}
}

/*
 * Try to flush some data based on policy set by @state. This is only advisory
 * and may fail for various reasons. The caller is supposed to examine the
 * state of @space_info to detect the outcome.
 */
static void flush_space(struct btrfs_fs_info *fs_info,
		       struct btrfs_space_info *space_info, u64 num_bytes,
		       enum btrfs_flush_state state, bool for_preempt)
{
	struct btrfs_root *root = fs_info->tree_root;
	struct btrfs_trans_handle *trans;
	int nr;
	int ret = 0;

	switch (state) {
	case FLUSH_DELAYED_ITEMS_NR:
	case FLUSH_DELAYED_ITEMS:
		if (state == FLUSH_DELAYED_ITEMS_NR)
			nr = calc_reclaim_items_nr(fs_info, num_bytes) * 2;
		else
			nr = -1;

		trans = btrfs_join_transaction_nostart(root);
		if (IS_ERR(trans)) {
			ret = PTR_ERR(trans);
			if (ret == -ENOENT)
				ret = 0;
			break;
		}
		ret = btrfs_run_delayed_items_nr(trans, nr);
		btrfs_end_transaction(trans);
		break;
	case FLUSH_DELALLOC:
	case FLUSH_DELALLOC_WAIT:
	case FLUSH_DELALLOC_FULL:
		if (state == FLUSH_DELALLOC_FULL)
			num_bytes = U64_MAX;
		shrink_delalloc(fs_info, space_info, num_bytes,
				state != FLUSH_DELALLOC, for_preempt);
		break;
	case FLUSH_DELAYED_REFS_NR:
	case FLUSH_DELAYED_REFS:
		trans = btrfs_join_transaction_nostart(root);
		if (IS_ERR(trans)) {
			ret = PTR_ERR(trans);
			if (ret == -ENOENT)
				ret = 0;
			break;
		}
		if (state == FLUSH_DELAYED_REFS_NR)
			btrfs_run_delayed_refs(trans, num_bytes);
		else
			btrfs_run_delayed_refs(trans, 0);
		btrfs_end_transaction(trans);
		break;
	case ALLOC_CHUNK:
	case ALLOC_CHUNK_FORCE:
		trans = btrfs_join_transaction(root);
		if (IS_ERR(trans)) {
			ret = PTR_ERR(trans);
			break;
		}
		ret = btrfs_chunk_alloc(trans,
				btrfs_get_alloc_profile(fs_info, space_info->flags),
				(state == ALLOC_CHUNK) ? CHUNK_ALLOC_NO_FORCE :
					CHUNK_ALLOC_FORCE);
		btrfs_end_transaction(trans);

		if (ret > 0 || ret == -ENOSPC)
			ret = 0;
		break;
	case RUN_DELAYED_IPUTS:
		/*
		 * If we have pending delayed iputs then we could free up a
		 * bunch of pinned space, so make sure we run the iputs before
		 * we do our pinned bytes check below.
		 */
		btrfs_run_delayed_iputs(fs_info);
		btrfs_wait_on_delayed_iputs(fs_info);
		break;
	case COMMIT_TRANS:
		ASSERT(current->journal_info == NULL);
		/*
		 * We don't want to start a new transaction, just attach to the
		 * current one or wait it fully commits in case its commit is
		 * happening at the moment. Note: we don't use a nostart join
		 * because that does not wait for a transaction to fully commit
		 * (only for it to be unblocked, state TRANS_STATE_UNBLOCKED).
		 */
		trans = btrfs_attach_transaction_barrier(root);
		if (IS_ERR(trans)) {
			ret = PTR_ERR(trans);
			if (ret == -ENOENT)
				ret = 0;
			break;
		}
		ret = btrfs_commit_transaction(trans);
		break;
	default:
		ret = -ENOSPC;
		break;
	}

	trace_btrfs_flush_space(fs_info, space_info->flags, num_bytes, state,
				ret, for_preempt);
	return;
}

static inline u64
btrfs_calc_reclaim_metadata_size(struct btrfs_fs_info *fs_info,
				 struct btrfs_space_info *space_info)
{
	u64 used;
	u64 avail;
	u64 to_reclaim = space_info->reclaim_size;

	lockdep_assert_held(&space_info->lock);

	avail = calc_available_free_space(fs_info, space_info,
					  BTRFS_RESERVE_FLUSH_ALL);
	used = btrfs_space_info_used(space_info, true);

	/*
	 * We may be flushing because suddenly we have less space than we had
	 * before, and now we're well over-committed based on our current free
	 * space.  If that's the case add in our overage so we make sure to put
	 * appropriate pressure on the flushing state machine.
	 */
	if (space_info->total_bytes + avail < used)
		to_reclaim += used - (space_info->total_bytes + avail);

	return to_reclaim;
}

static bool need_preemptive_reclaim(struct btrfs_fs_info *fs_info,
				    struct btrfs_space_info *space_info)
{
	const u64 global_rsv_size = btrfs_block_rsv_reserved(&fs_info->global_block_rsv);
	u64 ordered, delalloc;
	u64 thresh;
	u64 used;

	thresh = mult_perc(space_info->total_bytes, 90);

	lockdep_assert_held(&space_info->lock);

	/* If we're just plain full then async reclaim just slows us down. */
	if ((space_info->bytes_used + space_info->bytes_reserved +
	     global_rsv_size) >= thresh)
		return false;

	used = space_info->bytes_may_use + space_info->bytes_pinned;

	/* The total flushable belongs to the global rsv, don't flush. */
	if (global_rsv_size >= used)
		return false;

	/*
	 * 128MiB is 1/4 of the maximum global rsv size.  If we have less than
	 * that devoted to other reservations then there's no sense in flushing,
	 * we don't have a lot of things that need flushing.
	 */
	if (used - global_rsv_size <= SZ_128M)
		return false;

	/*
	 * We have tickets queued, bail so we don't compete with the async
	 * flushers.
	 */
	if (space_info->reclaim_size)
		return false;

	/*
	 * If we have over half of the free space occupied by reservations or
	 * pinned then we want to start flushing.
	 *
	 * We do not do the traditional thing here, which is to say
	 *
	 *   if (used >= ((total_bytes + avail) / 2))
	 *     return 1;
	 *
	 * because this doesn't quite work how we want.  If we had more than 50%
	 * of the space_info used by bytes_used and we had 0 available we'd just
	 * constantly run the background flusher.  Instead we want it to kick in
	 * if our reclaimable space exceeds our clamped free space.
	 *
	 * Our clamping range is 2^1 -> 2^8.  Practically speaking that means
	 * the following:
	 *
	 * Amount of RAM        Minimum threshold       Maximum threshold
	 *
	 *        256GiB                     1GiB                  128GiB
	 *        128GiB                   512MiB                   64GiB
	 *         64GiB                   256MiB                   32GiB
	 *         32GiB                   128MiB                   16GiB
	 *         16GiB                    64MiB                    8GiB
	 *
	 * These are the range our thresholds will fall in, corresponding to how
	 * much delalloc we need for the background flusher to kick in.
	 */

	thresh = calc_available_free_space(fs_info, space_info,
					   BTRFS_RESERVE_FLUSH_ALL);
	used = space_info->bytes_used + space_info->bytes_reserved +
	       space_info->bytes_readonly + global_rsv_size;
	if (used < space_info->total_bytes)
		thresh += space_info->total_bytes - used;
	thresh >>= space_info->clamp;

	used = space_info->bytes_pinned;

	/*
	 * If we have more ordered bytes than delalloc bytes then we're either
	 * doing a lot of DIO, or we simply don't have a lot of delalloc waiting
	 * around.  Preemptive flushing is only useful in that it can free up
	 * space before tickets need to wait for things to finish.  In the case
	 * of ordered extents, preemptively waiting on ordered extents gets us
	 * nothing, if our reservations are tied up in ordered extents we'll
	 * simply have to slow down writers by forcing them to wait on ordered
	 * extents.
	 *
	 * In the case that ordered is larger than delalloc, only include the
	 * block reserves that we would actually be able to directly reclaim
	 * from.  In this case if we're heavy on metadata operations this will
	 * clearly be heavy enough to warrant preemptive flushing.  In the case
	 * of heavy DIO or ordered reservations, preemptive flushing will just
	 * waste time and cause us to slow down.
	 *
	 * We want to make sure we truly are maxed out on ordered however, so
	 * cut ordered in half, and if it's still higher than delalloc then we
	 * can keep flushing.  This is to avoid the case where we start
	 * flushing, and now delalloc == ordered and we stop preemptively
	 * flushing when we could still have several gigs of delalloc to flush.
	 */
	ordered = percpu_counter_read_positive(&fs_info->ordered_bytes) >> 1;
	delalloc = percpu_counter_read_positive(&fs_info->delalloc_bytes);
	if (ordered >= delalloc)
		used += btrfs_block_rsv_reserved(&fs_info->delayed_refs_rsv) +
			btrfs_block_rsv_reserved(&fs_info->delayed_block_rsv);
	else
		used += space_info->bytes_may_use - global_rsv_size;

	return (used >= thresh && !btrfs_fs_closing(fs_info) &&
		!test_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state));
}

static bool steal_from_global_rsv(struct btrfs_fs_info *fs_info,
				  struct btrfs_space_info *space_info,
				  struct reserve_ticket *ticket)
{
	struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
	u64 min_bytes;

	if (!ticket->steal)
		return false;

	if (global_rsv->space_info != space_info)
		return false;

	spin_lock(&global_rsv->lock);
	min_bytes = mult_perc(global_rsv->size, 10);
	if (global_rsv->reserved < min_bytes + ticket->bytes) {
		spin_unlock(&global_rsv->lock);
		return false;
	}
	global_rsv->reserved -= ticket->bytes;
	remove_ticket(space_info, ticket);
	ticket->bytes = 0;
	wake_up(&ticket->wait);
	space_info->tickets_id++;
	if (global_rsv->reserved < global_rsv->size)
		global_rsv->full = 0;
	spin_unlock(&global_rsv->lock);

	return true;
}

/*
 * We've exhausted our flushing, start failing tickets.
 *
 * @fs_info - fs_info for this fs
 * @space_info - the space info we were flushing
 *
 * We call this when we've exhausted our flushing ability and haven't made
 * progress in satisfying tickets.  The reservation code handles tickets in
 * order, so if there is a large ticket first and then smaller ones we could
 * very well satisfy the smaller tickets.  This will attempt to wake up any
 * tickets in the list to catch this case.
 *
 * This function returns true if it was able to make progress by clearing out
 * other tickets, or if it stumbles across a ticket that was smaller than the
 * first ticket.
 */
static bool maybe_fail_all_tickets(struct btrfs_fs_info *fs_info,
				   struct btrfs_space_info *space_info)
{
	struct reserve_ticket *ticket;
	u64 tickets_id = space_info->tickets_id;
	const bool aborted = BTRFS_FS_ERROR(fs_info);

	trace_btrfs_fail_all_tickets(fs_info, space_info);

	if (btrfs_test_opt(fs_info, ENOSPC_DEBUG)) {
		btrfs_info(fs_info, "cannot satisfy tickets, dumping space info");
		__btrfs_dump_space_info(fs_info, space_info);
	}

	while (!list_empty(&space_info->tickets) &&
	       tickets_id == space_info->tickets_id) {
		ticket = list_first_entry(&space_info->tickets,
					  struct reserve_ticket, list);

		if (!aborted && steal_from_global_rsv(fs_info, space_info, ticket))
			return true;

		if (!aborted && btrfs_test_opt(fs_info, ENOSPC_DEBUG))
			btrfs_info(fs_info, "failing ticket with %llu bytes",
				   ticket->bytes);

		remove_ticket(space_info, ticket);
		if (aborted)
			ticket->error = -EIO;
		else
			ticket->error = -ENOSPC;
		wake_up(&ticket->wait);

		/*
		 * We're just throwing tickets away, so more flushing may not
		 * trip over btrfs_try_granting_tickets, so we need to call it
		 * here to see if we can make progress with the next ticket in
		 * the list.
		 */
		if (!aborted)
			btrfs_try_granting_tickets(fs_info, space_info);
	}
	return (tickets_id != space_info->tickets_id);
}

/*
 * This is for normal flushers, we can wait all goddamned day if we want to.  We
 * will loop and continuously try to flush as long as we are making progress.
 * We count progress as clearing off tickets each time we have to loop.
 */
static void btrfs_async_reclaim_metadata_space(struct work_struct *work)
{
	struct btrfs_fs_info *fs_info;
	struct btrfs_space_info *space_info;
	u64 to_reclaim;
	enum btrfs_flush_state flush_state;
	int commit_cycles = 0;
	u64 last_tickets_id;

	fs_info = container_of(work, struct btrfs_fs_info, async_reclaim_work);
	space_info = btrfs_find_space_info(fs_info, BTRFS_BLOCK_GROUP_METADATA);

	spin_lock(&space_info->lock);
	to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info, space_info);
	if (!to_reclaim) {
		space_info->flush = 0;
		spin_unlock(&space_info->lock);
		return;
	}
	last_tickets_id = space_info->tickets_id;
	spin_unlock(&space_info->lock);

	flush_state = FLUSH_DELAYED_ITEMS_NR;
	do {
		flush_space(fs_info, space_info, to_reclaim, flush_state, false);
		spin_lock(&space_info->lock);
		if (list_empty(&space_info->tickets)) {
			space_info->flush = 0;
			spin_unlock(&space_info->lock);
			return;
		}
		to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info,
							      space_info);
		if (last_tickets_id == space_info->tickets_id) {
			flush_state++;
		} else {
			last_tickets_id = space_info->tickets_id;
			flush_state = FLUSH_DELAYED_ITEMS_NR;
			if (commit_cycles)
				commit_cycles--;
		}

		/*
		 * We do not want to empty the system of delalloc unless we're
		 * under heavy pressure, so allow one trip through the flushing
		 * logic before we start doing a FLUSH_DELALLOC_FULL.
		 */
		if (flush_state == FLUSH_DELALLOC_FULL && !commit_cycles)
			flush_state++;

		/*
		 * We don't want to force a chunk allocation until we've tried
		 * pretty hard to reclaim space.  Think of the case where we
		 * freed up a bunch of space and so have a lot of pinned space
		 * to reclaim.  We would rather use that than possibly create a
		 * underutilized metadata chunk.  So if this is our first run
		 * through the flushing state machine skip ALLOC_CHUNK_FORCE and
		 * commit the transaction.  If nothing has changed the next go
		 * around then we can force a chunk allocation.
		 */
		if (flush_state == ALLOC_CHUNK_FORCE && !commit_cycles)
			flush_state++;

		if (flush_state > COMMIT_TRANS) {
			commit_cycles++;
			if (commit_cycles > 2) {
				if (maybe_fail_all_tickets(fs_info, space_info)) {
					flush_state = FLUSH_DELAYED_ITEMS_NR;
					commit_cycles--;
				} else {
					space_info->flush = 0;
				}
			} else {
				flush_state = FLUSH_DELAYED_ITEMS_NR;
			}
		}
		spin_unlock(&space_info->lock);
	} while (flush_state <= COMMIT_TRANS);
}

/*
 * This handles pre-flushing of metadata space before we get to the point that
 * we need to start blocking threads on tickets.  The logic here is different
 * from the other flush paths because it doesn't rely on tickets to tell us how
 * much we need to flush, instead it attempts to keep us below the 80% full
 * watermark of space by flushing whichever reservation pool is currently the
 * largest.
 */
static void btrfs_preempt_reclaim_metadata_space(struct work_struct *work)
{
	struct btrfs_fs_info *fs_info;
	struct btrfs_space_info *space_info;
	struct btrfs_block_rsv *delayed_block_rsv;
	struct btrfs_block_rsv *delayed_refs_rsv;
	struct btrfs_block_rsv *global_rsv;
	struct btrfs_block_rsv *trans_rsv;
	int loops = 0;

	fs_info = container_of(work, struct btrfs_fs_info,
			       preempt_reclaim_work);
	space_info = btrfs_find_space_info(fs_info, BTRFS_BLOCK_GROUP_METADATA);
	delayed_block_rsv = &fs_info->delayed_block_rsv;
	delayed_refs_rsv = &fs_info->delayed_refs_rsv;
	global_rsv = &fs_info->global_block_rsv;
	trans_rsv = &fs_info->trans_block_rsv;

	spin_lock(&space_info->lock);
	while (need_preemptive_reclaim(fs_info, space_info)) {
		enum btrfs_flush_state flush;
		u64 delalloc_size = 0;
		u64 to_reclaim, block_rsv_size;
		const u64 global_rsv_size = btrfs_block_rsv_reserved(global_rsv);

		loops++;

		/*
		 * We don't have a precise counter for the metadata being
		 * reserved for delalloc, so we'll approximate it by subtracting
		 * out the block rsv's space from the bytes_may_use.  If that
		 * amount is higher than the individual reserves, then we can
		 * assume it's tied up in delalloc reservations.
		 */
		block_rsv_size = global_rsv_size +
			btrfs_block_rsv_reserved(delayed_block_rsv) +
			btrfs_block_rsv_reserved(delayed_refs_rsv) +
			btrfs_block_rsv_reserved(trans_rsv);
		if (block_rsv_size < space_info->bytes_may_use)
			delalloc_size = space_info->bytes_may_use - block_rsv_size;

		/*
		 * We don't want to include the global_rsv in our calculation,
		 * because that's space we can't touch.  Subtract it from the
		 * block_rsv_size for the next checks.
		 */
		block_rsv_size -= global_rsv_size;

		/*
		 * We really want to avoid flushing delalloc too much, as it
		 * could result in poor allocation patterns, so only flush it if
		 * it's larger than the rest of the pools combined.
		 */
		if (delalloc_size > block_rsv_size) {
			to_reclaim = delalloc_size;
			flush = FLUSH_DELALLOC;
		} else if (space_info->bytes_pinned >
			   (btrfs_block_rsv_reserved(delayed_block_rsv) +
			    btrfs_block_rsv_reserved(delayed_refs_rsv))) {
			to_reclaim = space_info->bytes_pinned;
			flush = COMMIT_TRANS;
		} else if (btrfs_block_rsv_reserved(delayed_block_rsv) >
			   btrfs_block_rsv_reserved(delayed_refs_rsv)) {
			to_reclaim = btrfs_block_rsv_reserved(delayed_block_rsv);
			flush = FLUSH_DELAYED_ITEMS_NR;
		} else {
			to_reclaim = btrfs_block_rsv_reserved(delayed_refs_rsv);
			flush = FLUSH_DELAYED_REFS_NR;
		}

		spin_unlock(&space_info->lock);

		/*
		 * We don't want to reclaim everything, just a portion, so scale
		 * down the to_reclaim by 1/4.  If it takes us down to 0,
		 * reclaim 1 items worth.
		 */
		to_reclaim >>= 2;
		if (!to_reclaim)
			to_reclaim = btrfs_calc_insert_metadata_size(fs_info, 1);
		flush_space(fs_info, space_info, to_reclaim, flush, true);
		cond_resched();
		spin_lock(&space_info->lock);
	}

	/* We only went through once, back off our clamping. */
	if (loops == 1 && !space_info->reclaim_size)
		space_info->clamp = max(1, space_info->clamp - 1);
	trace_btrfs_done_preemptive_reclaim(fs_info, space_info);
	spin_unlock(&space_info->lock);
}

/*
 * FLUSH_DELALLOC_WAIT:
 *   Space is freed from flushing delalloc in one of two ways.
 *
 *   1) compression is on and we allocate less space than we reserved
 *   2) we are overwriting existing space
 *
 *   For #1 that extra space is reclaimed as soon as the delalloc pages are
 *   COWed, by way of btrfs_add_reserved_bytes() which adds the actual extent
 *   length to ->bytes_reserved, and subtracts the reserved space from
 *   ->bytes_may_use.
 *
 *   For #2 this is trickier.  Once the ordered extent runs we will drop the
 *   extent in the range we are overwriting, which creates a delayed ref for
 *   that freed extent.  This however is not reclaimed until the transaction
 *   commits, thus the next stages.
 *
 * RUN_DELAYED_IPUTS
 *   If we are freeing inodes, we want to make sure all delayed iputs have
 *   completed, because they could have been on an inode with i_nlink == 0, and
 *   thus have been truncated and freed up space.  But again this space is not
 *   immediately re-usable, it comes in the form of a delayed ref, which must be
 *   run and then the transaction must be committed.
 *
 * COMMIT_TRANS
 *   This is where we reclaim all of the pinned space generated by running the
 *   iputs
 *
 * ALLOC_CHUNK_FORCE
 *   For data we start with alloc chunk force, however we could have been full
 *   before, and then the transaction commit could have freed new block groups,
 *   so if we now have space to allocate do the force chunk allocation.
 */
static const enum btrfs_flush_state data_flush_states[] = {
	FLUSH_DELALLOC_FULL,
	RUN_DELAYED_IPUTS,
	COMMIT_TRANS,
	ALLOC_CHUNK_FORCE,
};

static void btrfs_async_reclaim_data_space(struct work_struct *work)
{
	struct btrfs_fs_info *fs_info;
	struct btrfs_space_info *space_info;
	u64 last_tickets_id;
	enum btrfs_flush_state flush_state = 0;

	fs_info = container_of(work, struct btrfs_fs_info, async_data_reclaim_work);
	space_info = fs_info->data_sinfo;

	spin_lock(&space_info->lock);
	if (list_empty(&space_info->tickets)) {
		space_info->flush = 0;
		spin_unlock(&space_info->lock);
		return;
	}
	last_tickets_id = space_info->tickets_id;
	spin_unlock(&space_info->lock);

	while (!space_info->full) {
		flush_space(fs_info, space_info, U64_MAX, ALLOC_CHUNK_FORCE, false);
		spin_lock(&space_info->lock);
		if (list_empty(&space_info->tickets)) {
			space_info->flush = 0;
			spin_unlock(&space_info->lock);
			return;
		}

		/* Something happened, fail everything and bail. */
		if (BTRFS_FS_ERROR(fs_info))
			goto aborted_fs;
		last_tickets_id = space_info->tickets_id;
		spin_unlock(&space_info->lock);
	}

	while (flush_state < ARRAY_SIZE(data_flush_states)) {
		flush_space(fs_info, space_info, U64_MAX,
			    data_flush_states[flush_state], false);
		spin_lock(&space_info->lock);
		if (list_empty(&space_info->tickets)) {
			space_info->flush = 0;
			spin_unlock(&space_info->lock);
			return;
		}

		if (last_tickets_id == space_info->tickets_id) {
			flush_state++;
		} else {
			last_tickets_id = space_info->tickets_id;
			flush_state = 0;
		}

		if (flush_state >= ARRAY_SIZE(data_flush_states)) {
			if (space_info->full) {
				if (maybe_fail_all_tickets(fs_info, space_info))
					flush_state = 0;
				else
					space_info->flush = 0;
			} else {
				flush_state = 0;
			}

			/* Something happened, fail everything and bail. */
			if (BTRFS_FS_ERROR(fs_info))
				goto aborted_fs;

		}
		spin_unlock(&space_info->lock);
	}
	return;

aborted_fs:
	maybe_fail_all_tickets(fs_info, space_info);
	space_info->flush = 0;
	spin_unlock(&space_info->lock);
}

void btrfs_init_async_reclaim_work(struct btrfs_fs_info *fs_info)
{
	INIT_WORK(&fs_info->async_reclaim_work, btrfs_async_reclaim_metadata_space);
	INIT_WORK(&fs_info->async_data_reclaim_work, btrfs_async_reclaim_data_space);
	INIT_WORK(&fs_info->preempt_reclaim_work,
		  btrfs_preempt_reclaim_metadata_space);
}

static const enum btrfs_flush_state priority_flush_states[] = {
	FLUSH_DELAYED_ITEMS_NR,
	FLUSH_DELAYED_ITEMS,
	ALLOC_CHUNK,
};

static const enum btrfs_flush_state evict_flush_states[] = {
	FLUSH_DELAYED_ITEMS_NR,
	FLUSH_DELAYED_ITEMS,
	FLUSH_DELAYED_REFS_NR,
	FLUSH_DELAYED_REFS,
	FLUSH_DELALLOC,
	FLUSH_DELALLOC_WAIT,
	FLUSH_DELALLOC_FULL,
	ALLOC_CHUNK,
	COMMIT_TRANS,
};

static void priority_reclaim_metadata_space(struct btrfs_fs_info *fs_info,
				struct btrfs_space_info *space_info,
				struct reserve_ticket *ticket,
				const enum btrfs_flush_state *states,
				int states_nr)
{
	u64 to_reclaim;
	int flush_state = 0;

	spin_lock(&space_info->lock);
	to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info, space_info);
	/*
	 * This is the priority reclaim path, so to_reclaim could be >0 still
	 * because we may have only satisfied the priority tickets and still
	 * left non priority tickets on the list.  We would then have
	 * to_reclaim but ->bytes == 0.
	 */
	if (ticket->bytes == 0) {
		spin_unlock(&space_info->lock);
		return;
	}

	while (flush_state < states_nr) {
		spin_unlock(&space_info->lock);
		flush_space(fs_info, space_info, to_reclaim, states[flush_state],
			    false);
		flush_state++;
		spin_lock(&space_info->lock);
		if (ticket->bytes == 0) {
			spin_unlock(&space_info->lock);
			return;
		}
	}

	/*
	 * Attempt to steal from the global rsv if we can, except if the fs was
	 * turned into error mode due to a transaction abort when flushing space
	 * above, in that case fail with the abort error instead of returning
	 * success to the caller if we can steal from the global rsv - this is
	 * just to have caller fail immeditelly instead of later when trying to
	 * modify the fs, making it easier to debug -ENOSPC problems.
	 */
	if (BTRFS_FS_ERROR(fs_info)) {
		ticket->error = BTRFS_FS_ERROR(fs_info);
		remove_ticket(space_info, ticket);
	} else if (!steal_from_global_rsv(fs_info, space_info, ticket)) {
		ticket->error = -ENOSPC;
		remove_ticket(space_info, ticket);
	}

	/*
	 * We must run try_granting_tickets here because we could be a large
	 * ticket in front of a smaller ticket that can now be satisfied with
	 * the available space.
	 */
	btrfs_try_granting_tickets(fs_info, space_info);
	spin_unlock(&space_info->lock);
}

static void priority_reclaim_data_space(struct btrfs_fs_info *fs_info,
					struct btrfs_space_info *space_info,
					struct reserve_ticket *ticket)
{
	spin_lock(&space_info->lock);

	/* We could have been granted before we got here. */
	if (ticket->bytes == 0) {
		spin_unlock(&space_info->lock);
		return;
	}

	while (!space_info->full) {
		spin_unlock(&space_info->lock);
		flush_space(fs_info, space_info, U64_MAX, ALLOC_CHUNK_FORCE, false);
		spin_lock(&space_info->lock);
		if (ticket->bytes == 0) {
			spin_unlock(&space_info->lock);
			return;
		}
	}

	ticket->error = -ENOSPC;
	remove_ticket(space_info, ticket);
	btrfs_try_granting_tickets(fs_info, space_info);
	spin_unlock(&space_info->lock);
}

static void wait_reserve_ticket(struct btrfs_fs_info *fs_info,
				struct btrfs_space_info *space_info,
				struct reserve_ticket *ticket)

{
	DEFINE_WAIT(wait);
	int ret = 0;

	spin_lock(&space_info->lock);
	while (ticket->bytes > 0 && ticket->error == 0) {
		ret = prepare_to_wait_event(&ticket->wait, &wait, TASK_KILLABLE);
		if (ret) {
			/*
			 * Delete us from the list. After we unlock the space
			 * info, we don't want the async reclaim job to reserve
			 * space for this ticket. If that would happen, then the
			 * ticket's task would not known that space was reserved
			 * despite getting an error, resulting in a space leak
			 * (bytes_may_use counter of our space_info).
			 */
			remove_ticket(space_info, ticket);
			ticket->error = -EINTR;
			break;
		}
		spin_unlock(&space_info->lock);

		schedule();

		finish_wait(&ticket->wait, &wait);
		spin_lock(&space_info->lock);
	}
	spin_unlock(&space_info->lock);
}

/*
 * Do the appropriate flushing and waiting for a ticket.
 *
 * @fs_info:    the filesystem
 * @space_info: space info for the reservation
 * @ticket:     ticket for the reservation
 * @start_ns:   timestamp when the reservation started
 * @orig_bytes: amount of bytes originally reserved
 * @flush:      how much we can flush
 *
 * This does the work of figuring out how to flush for the ticket, waiting for
 * the reservation, and returning the appropriate error if there is one.
 */
static int handle_reserve_ticket(struct btrfs_fs_info *fs_info,
				 struct btrfs_space_info *space_info,
				 struct reserve_ticket *ticket,
				 u64 start_ns, u64 orig_bytes,
				 enum btrfs_reserve_flush_enum flush)
{
	int ret;

	switch (flush) {
	case BTRFS_RESERVE_FLUSH_DATA:
	case BTRFS_RESERVE_FLUSH_ALL:
	case BTRFS_RESERVE_FLUSH_ALL_STEAL:
		wait_reserve_ticket(fs_info, space_info, ticket);
		break;
	case BTRFS_RESERVE_FLUSH_LIMIT:
		priority_reclaim_metadata_space(fs_info, space_info, ticket,
						priority_flush_states,
						ARRAY_SIZE(priority_flush_states));
		break;
	case BTRFS_RESERVE_FLUSH_EVICT:
		priority_reclaim_metadata_space(fs_info, space_info, ticket,
						evict_flush_states,
						ARRAY_SIZE(evict_flush_states));
		break;
	case BTRFS_RESERVE_FLUSH_FREE_SPACE_INODE:
		priority_reclaim_data_space(fs_info, space_info, ticket);
		break;
	default:
		ASSERT(0);
		break;
	}

	ret = ticket->error;
	ASSERT(list_empty(&ticket->list));
	/*
	 * Check that we can't have an error set if the reservation succeeded,
	 * as that would confuse tasks and lead them to error out without
	 * releasing reserved space (if an error happens the expectation is that
	 * space wasn't reserved at all).
	 */
	ASSERT(!(ticket->bytes == 0 && ticket->error));
	trace_btrfs_reserve_ticket(fs_info, space_info->flags, orig_bytes,
				   start_ns, flush, ticket->error);
	return ret;
}

/*
 * This returns true if this flush state will go through the ordinary flushing
 * code.
 */
static inline bool is_normal_flushing(enum btrfs_reserve_flush_enum flush)
{
	return	(flush == BTRFS_RESERVE_FLUSH_ALL) ||
		(flush == BTRFS_RESERVE_FLUSH_ALL_STEAL);
}

static inline void maybe_clamp_preempt(struct btrfs_fs_info *fs_info,
				       struct btrfs_space_info *space_info)
{
	u64 ordered = percpu_counter_sum_positive(&fs_info->ordered_bytes);
	u64 delalloc = percpu_counter_sum_positive(&fs_info->delalloc_bytes);

	/*
	 * If we're heavy on ordered operations then clamping won't help us.  We
	 * need to clamp specifically to keep up with dirty'ing buffered
	 * writers, because there's not a 1:1 correlation of writing delalloc
	 * and freeing space, like there is with flushing delayed refs or
	 * delayed nodes.  If we're already more ordered than delalloc then
	 * we're keeping up, otherwise we aren't and should probably clamp.
	 */
	if (ordered < delalloc)
		space_info->clamp = min(space_info->clamp + 1, 8);
}

static inline bool can_steal(enum btrfs_reserve_flush_enum flush)
{
	return (flush == BTRFS_RESERVE_FLUSH_ALL_STEAL ||
		flush == BTRFS_RESERVE_FLUSH_EVICT);
}

/*
 * NO_FLUSH and FLUSH_EMERGENCY don't want to create a ticket, they just want to
 * fail as quickly as possible.
 */
static inline bool can_ticket(enum btrfs_reserve_flush_enum flush)
{
	return (flush != BTRFS_RESERVE_NO_FLUSH &&
		flush != BTRFS_RESERVE_FLUSH_EMERGENCY);
}

/*
 * Try to reserve bytes from the block_rsv's space.
 *
 * @fs_info:    the filesystem
 * @space_info: space info we want to allocate from
 * @orig_bytes: number of bytes we want
 * @flush:      whether or not we can flush to make our reservation
 *
 * This will reserve orig_bytes number of bytes from the space info associated
 * with the block_rsv.  If there is not enough space it will make an attempt to
 * flush out space to make room.  It will do this by flushing delalloc if
 * possible or committing the transaction.  If flush is 0 then no attempts to
 * regain reservations will be made and this will fail if there is not enough
 * space already.
 */
static int __reserve_bytes(struct btrfs_fs_info *fs_info,
			   struct btrfs_space_info *space_info, u64 orig_bytes,
			   enum btrfs_reserve_flush_enum flush)
{
	struct work_struct *async_work;
	struct reserve_ticket ticket;
	u64 start_ns = 0;
	u64 used;
	int ret = -ENOSPC;
	bool pending_tickets;

	ASSERT(orig_bytes);
	/*
	 * If have a transaction handle (current->journal_info != NULL), then
	 * the flush method can not be neither BTRFS_RESERVE_FLUSH_ALL* nor
	 * BTRFS_RESERVE_FLUSH_EVICT, as we could deadlock because those
	 * flushing methods can trigger transaction commits.
	 */
	if (current->journal_info) {
		/* One assert per line for easier debugging. */
		ASSERT(flush != BTRFS_RESERVE_FLUSH_ALL);
		ASSERT(flush != BTRFS_RESERVE_FLUSH_ALL_STEAL);
		ASSERT(flush != BTRFS_RESERVE_FLUSH_EVICT);
	}

	if (flush == BTRFS_RESERVE_FLUSH_DATA)
		async_work = &fs_info->async_data_reclaim_work;
	else
		async_work = &fs_info->async_reclaim_work;

	spin_lock(&space_info->lock);
	used = btrfs_space_info_used(space_info, true);

	/*
	 * We don't want NO_FLUSH allocations to jump everybody, they can
	 * generally handle ENOSPC in a different way, so treat them the same as
	 * normal flushers when it comes to skipping pending tickets.
	 */
	if (is_normal_flushing(flush) || (flush == BTRFS_RESERVE_NO_FLUSH))
		pending_tickets = !list_empty(&space_info->tickets) ||
			!list_empty(&space_info->priority_tickets);
	else
		pending_tickets = !list_empty(&space_info->priority_tickets);

	/*
	 * Carry on if we have enough space (short-circuit) OR call
	 * can_overcommit() to ensure we can overcommit to continue.
	 */
	if (!pending_tickets &&
	    ((used + orig_bytes <= space_info->total_bytes) ||
	     btrfs_can_overcommit(fs_info, space_info, orig_bytes, flush))) {
		btrfs_space_info_update_bytes_may_use(fs_info, space_info,
						      orig_bytes);
		ret = 0;
	}

	/*
	 * Things are dire, we need to make a reservation so we don't abort.  We
	 * will let this reservation go through as long as we have actual space
	 * left to allocate for the block.
	 */
	if (ret && unlikely(flush == BTRFS_RESERVE_FLUSH_EMERGENCY)) {
		used = btrfs_space_info_used(space_info, false);
		if (used + orig_bytes <= space_info->total_bytes) {
			btrfs_space_info_update_bytes_may_use(fs_info, space_info,
							      orig_bytes);
			ret = 0;
		}
	}

	/*
	 * If we couldn't make a reservation then setup our reservation ticket
	 * and kick the async worker if it's not already running.
	 *
	 * If we are a priority flusher then we just need to add our ticket to
	 * the list and we will do our own flushing further down.
	 */
	if (ret && can_ticket(flush)) {
		ticket.bytes = orig_bytes;
		ticket.error = 0;
		space_info->reclaim_size += ticket.bytes;
		init_waitqueue_head(&ticket.wait);
		ticket.steal = can_steal(flush);
		if (trace_btrfs_reserve_ticket_enabled())
			start_ns = ktime_get_ns();

		if (flush == BTRFS_RESERVE_FLUSH_ALL ||
		    flush == BTRFS_RESERVE_FLUSH_ALL_STEAL ||
		    flush == BTRFS_RESERVE_FLUSH_DATA) {
			list_add_tail(&ticket.list, &space_info->tickets);
			if (!space_info->flush) {
				/*
				 * We were forced to add a reserve ticket, so
				 * our preemptive flushing is unable to keep
				 * up.  Clamp down on the threshold for the
				 * preemptive flushing in order to keep up with
				 * the workload.
				 */
				maybe_clamp_preempt(fs_info, space_info);

				space_info->flush = 1;
				trace_btrfs_trigger_flush(fs_info,
							  space_info->flags,
							  orig_bytes, flush,
							  "enospc");
				queue_work(system_unbound_wq, async_work);
			}
		} else {
			list_add_tail(&ticket.list,
				      &space_info->priority_tickets);
		}
	} else if (!ret && space_info->flags & BTRFS_BLOCK_GROUP_METADATA) {
		/*
		 * We will do the space reservation dance during log replay,
		 * which means we won't have fs_info->fs_root set, so don't do
		 * the async reclaim as we will panic.
		 */
		if (!test_bit(BTRFS_FS_LOG_RECOVERING, &fs_info->flags) &&
		    !work_busy(&fs_info->preempt_reclaim_work) &&
		    need_preemptive_reclaim(fs_info, space_info)) {
			trace_btrfs_trigger_flush(fs_info, space_info->flags,
						  orig_bytes, flush, "preempt");
			queue_work(system_unbound_wq,
				   &fs_info->preempt_reclaim_work);
		}
	}
	spin_unlock(&space_info->lock);
	if (!ret || !can_ticket(flush))
		return ret;

	return handle_reserve_ticket(fs_info, space_info, &ticket, start_ns,
				     orig_bytes, flush);
}

/*
 * Try to reserve metadata bytes from the block_rsv's space.
 *
 * @fs_info:    the filesystem
 * @space_info: the space_info we're allocating for
 * @orig_bytes: number of bytes we want
 * @flush:      whether or not we can flush to make our reservation
 *
 * This will reserve orig_bytes number of bytes from the space info associated
 * with the block_rsv.  If there is not enough space it will make an attempt to
 * flush out space to make room.  It will do this by flushing delalloc if
 * possible or committing the transaction.  If flush is 0 then no attempts to
 * regain reservations will be made and this will fail if there is not enough
 * space already.
 */
int btrfs_reserve_metadata_bytes(struct btrfs_fs_info *fs_info,
				 struct btrfs_space_info *space_info,
				 u64 orig_bytes,
				 enum btrfs_reserve_flush_enum flush)
{
	int ret;

	ret = __reserve_bytes(fs_info, space_info, orig_bytes, flush);
	if (ret == -ENOSPC) {
		trace_btrfs_space_reservation(fs_info, "space_info:enospc",
					      space_info->flags, orig_bytes, 1);

		if (btrfs_test_opt(fs_info, ENOSPC_DEBUG))
			btrfs_dump_space_info(fs_info, space_info, orig_bytes, 0);
	}
	return ret;
}

/*
 * Try to reserve data bytes for an allocation.
 *
 * @fs_info: the filesystem
 * @bytes:   number of bytes we need
 * @flush:   how we are allowed to flush
 *
 * This will reserve bytes from the data space info.  If there is not enough
 * space then we will attempt to flush space as specified by flush.
 */
int btrfs_reserve_data_bytes(struct btrfs_fs_info *fs_info, u64 bytes,
			     enum btrfs_reserve_flush_enum flush)
{
	struct btrfs_space_info *data_sinfo = fs_info->data_sinfo;
	int ret;

	ASSERT(flush == BTRFS_RESERVE_FLUSH_DATA ||
	       flush == BTRFS_RESERVE_FLUSH_FREE_SPACE_INODE ||
	       flush == BTRFS_RESERVE_NO_FLUSH);
	ASSERT(!current->journal_info || flush != BTRFS_RESERVE_FLUSH_DATA);

	ret = __reserve_bytes(fs_info, data_sinfo, bytes, flush);
	if (ret == -ENOSPC) {
		trace_btrfs_space_reservation(fs_info, "space_info:enospc",
					      data_sinfo->flags, bytes, 1);
		if (btrfs_test_opt(fs_info, ENOSPC_DEBUG))
			btrfs_dump_space_info(fs_info, data_sinfo, bytes, 0);
	}
	return ret;
}

/* Dump all the space infos when we abort a transaction due to ENOSPC. */
__cold void btrfs_dump_space_info_for_trans_abort(struct btrfs_fs_info *fs_info)
{
	struct btrfs_space_info *space_info;

	btrfs_info(fs_info, "dumping space info:");
	list_for_each_entry(space_info, &fs_info->space_info, list) {
		spin_lock(&space_info->lock);
		__btrfs_dump_space_info(fs_info, space_info);
		spin_unlock(&space_info->lock);
	}
	dump_global_block_rsv(fs_info);
}

/*
 * Account the unused space of all the readonly block group in the space_info.
 * takes mirrors into account.
 */
u64 btrfs_account_ro_block_groups_free_space(struct btrfs_space_info *sinfo)
{
	struct btrfs_block_group *block_group;
	u64 free_bytes = 0;
	int factor;

	/* It's df, we don't care if it's racy */
	if (list_empty(&sinfo->ro_bgs))
		return 0;

	spin_lock(&sinfo->lock);
	list_for_each_entry(block_group, &sinfo->ro_bgs, ro_list) {
		spin_lock(&block_group->lock);

		if (!block_group->ro) {
			spin_unlock(&block_group->lock);
			continue;
		}

		factor = btrfs_bg_type_to_factor(block_group->flags);
		free_bytes += (block_group->length -
			       block_group->used) * factor;

		spin_unlock(&block_group->lock);
	}
	spin_unlock(&sinfo->lock);

	return free_bytes;
}