summaryrefslogtreecommitdiff
path: root/fs/bcachefs/io_write.c
blob: b72cf31f72743c553c9f646f308986b93047ab64 (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
// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
 * Copyright 2012 Google, Inc.
 */

#include "bcachefs.h"
#include "alloc_foreground.h"
#include "bkey_buf.h"
#include "bset.h"
#include "btree_update.h"
#include "buckets.h"
#include "checksum.h"
#include "clock.h"
#include "compress.h"
#include "debug.h"
#include "ec.h"
#include "error.h"
#include "extent_update.h"
#include "inode.h"
#include "io_write.h"
#include "journal.h"
#include "keylist.h"
#include "move.h"
#include "nocow_locking.h"
#include "rebalance.h"
#include "subvolume.h"
#include "super.h"
#include "super-io.h"
#include "trace.h"

#include <linux/blkdev.h>
#include <linux/prefetch.h>
#include <linux/random.h>
#include <linux/sched/mm.h>

#ifndef CONFIG_BCACHEFS_NO_LATENCY_ACCT

static inline void bch2_congested_acct(struct bch_dev *ca, u64 io_latency,
				       u64 now, int rw)
{
	u64 latency_capable =
		ca->io_latency[rw].quantiles.entries[QUANTILE_IDX(1)].m;
	/* ideally we'd be taking into account the device's variance here: */
	u64 latency_threshold = latency_capable << (rw == READ ? 2 : 3);
	s64 latency_over = io_latency - latency_threshold;

	if (latency_threshold && latency_over > 0) {
		/*
		 * bump up congested by approximately latency_over * 4 /
		 * latency_threshold - we don't need much accuracy here so don't
		 * bother with the divide:
		 */
		if (atomic_read(&ca->congested) < CONGESTED_MAX)
			atomic_add(latency_over >>
				   max_t(int, ilog2(latency_threshold) - 2, 0),
				   &ca->congested);

		ca->congested_last = now;
	} else if (atomic_read(&ca->congested) > 0) {
		atomic_dec(&ca->congested);
	}
}

void bch2_latency_acct(struct bch_dev *ca, u64 submit_time, int rw)
{
	atomic64_t *latency = &ca->cur_latency[rw];
	u64 now = local_clock();
	u64 io_latency = time_after64(now, submit_time)
		? now - submit_time
		: 0;
	u64 old, new, v = atomic64_read(latency);

	do {
		old = v;

		/*
		 * If the io latency was reasonably close to the current
		 * latency, skip doing the update and atomic operation - most of
		 * the time:
		 */
		if (abs((int) (old - io_latency)) < (old >> 1) &&
		    now & ~(~0U << 5))
			break;

		new = ewma_add(old, io_latency, 5);
	} while ((v = atomic64_cmpxchg(latency, old, new)) != old);

	bch2_congested_acct(ca, io_latency, now, rw);

	__bch2_time_stats_update(&ca->io_latency[rw].stats, submit_time, now);
}

#endif

/* Allocate, free from mempool: */

void bch2_bio_free_pages_pool(struct bch_fs *c, struct bio *bio)
{
	struct bvec_iter_all iter;
	struct bio_vec *bv;

	bio_for_each_segment_all(bv, bio, iter)
		if (bv->bv_page != ZERO_PAGE(0))
			mempool_free(bv->bv_page, &c->bio_bounce_pages);
	bio->bi_vcnt = 0;
}

static struct page *__bio_alloc_page_pool(struct bch_fs *c, bool *using_mempool)
{
	struct page *page;

	if (likely(!*using_mempool)) {
		page = alloc_page(GFP_NOFS);
		if (unlikely(!page)) {
			mutex_lock(&c->bio_bounce_pages_lock);
			*using_mempool = true;
			goto pool_alloc;

		}
	} else {
pool_alloc:
		page = mempool_alloc(&c->bio_bounce_pages, GFP_NOFS);
	}

	return page;
}

void bch2_bio_alloc_pages_pool(struct bch_fs *c, struct bio *bio,
			       size_t size)
{
	bool using_mempool = false;

	while (size) {
		struct page *page = __bio_alloc_page_pool(c, &using_mempool);
		unsigned len = min_t(size_t, PAGE_SIZE, size);

		BUG_ON(!bio_add_page(bio, page, len, 0));
		size -= len;
	}

	if (using_mempool)
		mutex_unlock(&c->bio_bounce_pages_lock);
}

/* Extent update path: */

int bch2_sum_sector_overwrites(struct btree_trans *trans,
			       struct btree_iter *extent_iter,
			       struct bkey_i *new,
			       bool *usage_increasing,
			       s64 *i_sectors_delta,
			       s64 *disk_sectors_delta)
{
	struct bch_fs *c = trans->c;
	struct btree_iter iter;
	struct bkey_s_c old;
	unsigned new_replicas = bch2_bkey_replicas(c, bkey_i_to_s_c(new));
	bool new_compressed = bch2_bkey_sectors_compressed(bkey_i_to_s_c(new));
	int ret = 0;

	*usage_increasing	= false;
	*i_sectors_delta	= 0;
	*disk_sectors_delta	= 0;

	bch2_trans_copy_iter(&iter, extent_iter);

	for_each_btree_key_upto_continue_norestart(iter,
				new->k.p, BTREE_ITER_SLOTS, old, ret) {
		s64 sectors = min(new->k.p.offset, old.k->p.offset) -
			max(bkey_start_offset(&new->k),
			    bkey_start_offset(old.k));

		*i_sectors_delta += sectors *
			(bkey_extent_is_allocation(&new->k) -
			 bkey_extent_is_allocation(old.k));

		*disk_sectors_delta += sectors * bch2_bkey_nr_ptrs_allocated(bkey_i_to_s_c(new));
		*disk_sectors_delta -= new->k.p.snapshot == old.k->p.snapshot
			? sectors * bch2_bkey_nr_ptrs_fully_allocated(old)
			: 0;

		if (!*usage_increasing &&
		    (new->k.p.snapshot != old.k->p.snapshot ||
		     new_replicas > bch2_bkey_replicas(c, old) ||
		     (!new_compressed && bch2_bkey_sectors_compressed(old))))
			*usage_increasing = true;

		if (bkey_ge(old.k->p, new->k.p))
			break;
	}

	bch2_trans_iter_exit(trans, &iter);
	return ret;
}

static inline int bch2_extent_update_i_size_sectors(struct btree_trans *trans,
						    struct btree_iter *extent_iter,
						    u64 new_i_size,
						    s64 i_sectors_delta)
{
	/*
	 * Crazy performance optimization:
	 * Every extent update needs to also update the inode: the inode trigger
	 * will set bi->journal_seq to the journal sequence number of this
	 * transaction - for fsync.
	 *
	 * But if that's the only reason we're updating the inode (we're not
	 * updating bi_size or bi_sectors), then we don't need the inode update
	 * to be journalled - if we crash, the bi_journal_seq update will be
	 * lost, but that's fine.
	 */
	unsigned inode_update_flags = BTREE_UPDATE_NOJOURNAL;

	struct btree_iter iter;
	struct bkey_s_c k = bch2_bkey_get_iter(trans, &iter, BTREE_ID_inodes,
			      SPOS(0,
				   extent_iter->pos.inode,
				   extent_iter->snapshot),
			      BTREE_ITER_CACHED);
	int ret = bkey_err(k);
	if (unlikely(ret))
		return ret;

	/*
	 * varint_decode_fast(), in the inode .invalid method, reads up to 7
	 * bytes past the end of the buffer:
	 */
	struct bkey_i *k_mut = bch2_trans_kmalloc_nomemzero(trans, bkey_bytes(k.k) + 8);
	ret = PTR_ERR_OR_ZERO(k_mut);
	if (unlikely(ret))
		goto err;

	bkey_reassemble(k_mut, k);

	if (unlikely(k_mut->k.type != KEY_TYPE_inode_v3)) {
		k_mut = bch2_inode_to_v3(trans, k_mut);
		ret = PTR_ERR_OR_ZERO(k_mut);
		if (unlikely(ret))
			goto err;
	}

	struct bkey_i_inode_v3 *inode = bkey_i_to_inode_v3(k_mut);

	if (!(le64_to_cpu(inode->v.bi_flags) & BCH_INODE_i_size_dirty) &&
	    new_i_size > le64_to_cpu(inode->v.bi_size)) {
		inode->v.bi_size = cpu_to_le64(new_i_size);
		inode_update_flags = 0;
	}

	if (i_sectors_delta) {
		le64_add_cpu(&inode->v.bi_sectors, i_sectors_delta);
		inode_update_flags = 0;
	}

	if (inode->k.p.snapshot != iter.snapshot) {
		inode->k.p.snapshot = iter.snapshot;
		inode_update_flags = 0;
	}

	ret = bch2_trans_update(trans, &iter, &inode->k_i,
				BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE|
				inode_update_flags);
err:
	bch2_trans_iter_exit(trans, &iter);
	return ret;
}

int bch2_extent_update(struct btree_trans *trans,
		       subvol_inum inum,
		       struct btree_iter *iter,
		       struct bkey_i *k,
		       struct disk_reservation *disk_res,
		       u64 new_i_size,
		       s64 *i_sectors_delta_total,
		       bool check_enospc)
{
	struct bpos next_pos;
	bool usage_increasing;
	s64 i_sectors_delta = 0, disk_sectors_delta = 0;
	int ret;

	/*
	 * This traverses us the iterator without changing iter->path->pos to
	 * search_key() (which is pos + 1 for extents): we want there to be a
	 * path already traversed at iter->pos because
	 * bch2_trans_extent_update() will use it to attempt extent merging
	 */
	ret = __bch2_btree_iter_traverse(iter);
	if (ret)
		return ret;

	ret = bch2_extent_trim_atomic(trans, iter, k);
	if (ret)
		return ret;

	next_pos = k->k.p;

	ret = bch2_sum_sector_overwrites(trans, iter, k,
			&usage_increasing,
			&i_sectors_delta,
			&disk_sectors_delta);
	if (ret)
		return ret;

	if (disk_res &&
	    disk_sectors_delta > (s64) disk_res->sectors) {
		ret = bch2_disk_reservation_add(trans->c, disk_res,
					disk_sectors_delta - disk_res->sectors,
					!check_enospc || !usage_increasing
					? BCH_DISK_RESERVATION_NOFAIL : 0);
		if (ret)
			return ret;
	}

	/*
	 * Note:
	 * We always have to do an inode update - even when i_size/i_sectors
	 * aren't changing - for fsync to work properly; fsync relies on
	 * inode->bi_journal_seq which is updated by the trigger code:
	 */
	ret =   bch2_extent_update_i_size_sectors(trans, iter,
						  min(k->k.p.offset << 9, new_i_size),
						  i_sectors_delta) ?:
		bch2_trans_update(trans, iter, k, 0) ?:
		bch2_trans_commit(trans, disk_res, NULL,
				BCH_TRANS_COMMIT_no_check_rw|
				BCH_TRANS_COMMIT_no_enospc);
	if (unlikely(ret))
		return ret;

	if (i_sectors_delta_total)
		*i_sectors_delta_total += i_sectors_delta;
	bch2_btree_iter_set_pos(iter, next_pos);
	return 0;
}

static int bch2_write_index_default(struct bch_write_op *op)
{
	struct bch_fs *c = op->c;
	struct bkey_buf sk;
	struct keylist *keys = &op->insert_keys;
	struct bkey_i *k = bch2_keylist_front(keys);
	struct btree_trans *trans = bch2_trans_get(c);
	struct btree_iter iter;
	subvol_inum inum = {
		.subvol = op->subvol,
		.inum	= k->k.p.inode,
	};
	int ret;

	BUG_ON(!inum.subvol);

	bch2_bkey_buf_init(&sk);

	do {
		bch2_trans_begin(trans);

		k = bch2_keylist_front(keys);
		bch2_bkey_buf_copy(&sk, c, k);

		ret = bch2_subvolume_get_snapshot(trans, inum.subvol,
						  &sk.k->k.p.snapshot);
		if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
			continue;
		if (ret)
			break;

		bch2_trans_iter_init(trans, &iter, BTREE_ID_extents,
				     bkey_start_pos(&sk.k->k),
				     BTREE_ITER_SLOTS|BTREE_ITER_INTENT);

		ret =   bch2_bkey_set_needs_rebalance(c, sk.k, &op->opts) ?:
			bch2_extent_update(trans, inum, &iter, sk.k,
					&op->res,
					op->new_i_size, &op->i_sectors_delta,
					op->flags & BCH_WRITE_CHECK_ENOSPC);
		bch2_trans_iter_exit(trans, &iter);

		if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
			continue;
		if (ret)
			break;

		if (bkey_ge(iter.pos, k->k.p))
			bch2_keylist_pop_front(&op->insert_keys);
		else
			bch2_cut_front(iter.pos, k);
	} while (!bch2_keylist_empty(keys));

	bch2_trans_put(trans);
	bch2_bkey_buf_exit(&sk, c);

	return ret;
}

/* Writes */

void bch2_submit_wbio_replicas(struct bch_write_bio *wbio, struct bch_fs *c,
			       enum bch_data_type type,
			       const struct bkey_i *k,
			       bool nocow)
{
	struct bkey_ptrs_c ptrs = bch2_bkey_ptrs_c(bkey_i_to_s_c(k));
	struct bch_write_bio *n;

	BUG_ON(c->opts.nochanges);

	bkey_for_each_ptr(ptrs, ptr) {
		BUG_ON(!bch2_dev_exists2(c, ptr->dev));

		struct bch_dev *ca = bch_dev_bkey_exists(c, ptr->dev);

		if (to_entry(ptr + 1) < ptrs.end) {
			n = to_wbio(bio_alloc_clone(NULL, &wbio->bio,
						GFP_NOFS, &ca->replica_set));

			n->bio.bi_end_io	= wbio->bio.bi_end_io;
			n->bio.bi_private	= wbio->bio.bi_private;
			n->parent		= wbio;
			n->split		= true;
			n->bounce		= false;
			n->put_bio		= true;
			n->bio.bi_opf		= wbio->bio.bi_opf;
			bio_inc_remaining(&wbio->bio);
		} else {
			n = wbio;
			n->split		= false;
		}

		n->c			= c;
		n->dev			= ptr->dev;
		n->have_ioref		= nocow || bch2_dev_get_ioref(ca,
					type == BCH_DATA_btree ? READ : WRITE);
		n->nocow		= nocow;
		n->submit_time		= local_clock();
		n->inode_offset		= bkey_start_offset(&k->k);
		n->bio.bi_iter.bi_sector = ptr->offset;

		if (likely(n->have_ioref)) {
			this_cpu_add(ca->io_done->sectors[WRITE][type],
				     bio_sectors(&n->bio));

			bio_set_dev(&n->bio, ca->disk_sb.bdev);

			if (type != BCH_DATA_btree && unlikely(c->opts.no_data_io)) {
				bio_endio(&n->bio);
				continue;
			}

			submit_bio(&n->bio);
		} else {
			n->bio.bi_status	= BLK_STS_REMOVED;
			bio_endio(&n->bio);
		}
	}
}

static void __bch2_write(struct bch_write_op *);

static void bch2_write_done(struct closure *cl)
{
	struct bch_write_op *op = container_of(cl, struct bch_write_op, cl);
	struct bch_fs *c = op->c;

	EBUG_ON(op->open_buckets.nr);

	bch2_time_stats_update(&c->times[BCH_TIME_data_write], op->start_time);
	bch2_disk_reservation_put(c, &op->res);

	if (!(op->flags & BCH_WRITE_MOVE))
		bch2_write_ref_put(c, BCH_WRITE_REF_write);
	bch2_keylist_free(&op->insert_keys, op->inline_keys);

	EBUG_ON(cl->parent);
	closure_debug_destroy(cl);
	if (op->end_io)
		op->end_io(op);
}

static noinline int bch2_write_drop_io_error_ptrs(struct bch_write_op *op)
{
	struct keylist *keys = &op->insert_keys;
	struct bch_extent_ptr *ptr;
	struct bkey_i *src, *dst = keys->keys, *n;

	for (src = keys->keys; src != keys->top; src = n) {
		n = bkey_next(src);

		if (bkey_extent_is_direct_data(&src->k)) {
			bch2_bkey_drop_ptrs(bkey_i_to_s(src), ptr,
					    test_bit(ptr->dev, op->failed.d));

			if (!bch2_bkey_nr_ptrs(bkey_i_to_s_c(src)))
				return -EIO;
		}

		if (dst != src)
			memmove_u64s_down(dst, src, src->k.u64s);
		dst = bkey_next(dst);
	}

	keys->top = dst;
	return 0;
}

/**
 * __bch2_write_index - after a write, update index to point to new data
 * @op:		bch_write_op to process
 */
static void __bch2_write_index(struct bch_write_op *op)
{
	struct bch_fs *c = op->c;
	struct keylist *keys = &op->insert_keys;
	unsigned dev;
	int ret = 0;

	if (unlikely(op->flags & BCH_WRITE_IO_ERROR)) {
		ret = bch2_write_drop_io_error_ptrs(op);
		if (ret)
			goto err;
	}

	if (!bch2_keylist_empty(keys)) {
		u64 sectors_start = keylist_sectors(keys);

		ret = !(op->flags & BCH_WRITE_MOVE)
			? bch2_write_index_default(op)
			: bch2_data_update_index_update(op);

		BUG_ON(bch2_err_matches(ret, BCH_ERR_transaction_restart));
		BUG_ON(keylist_sectors(keys) && !ret);

		op->written += sectors_start - keylist_sectors(keys);

		if (ret && !bch2_err_matches(ret, EROFS)) {
			struct bkey_i *insert = bch2_keylist_front(&op->insert_keys);

			bch_err_inum_offset_ratelimited(c,
				insert->k.p.inode, insert->k.p.offset << 9,
				"%s write error while doing btree update: %s",
				op->flags & BCH_WRITE_MOVE ? "move" : "user",
				bch2_err_str(ret));
		}

		if (ret)
			goto err;
	}
out:
	/* If some a bucket wasn't written, we can't erasure code it: */
	for_each_set_bit(dev, op->failed.d, BCH_SB_MEMBERS_MAX)
		bch2_open_bucket_write_error(c, &op->open_buckets, dev);

	bch2_open_buckets_put(c, &op->open_buckets);
	return;
err:
	keys->top = keys->keys;
	op->error = ret;
	op->flags |= BCH_WRITE_DONE;
	goto out;
}

static inline void __wp_update_state(struct write_point *wp, enum write_point_state state)
{
	if (state != wp->state) {
		u64 now = ktime_get_ns();

		if (wp->last_state_change &&
		    time_after64(now, wp->last_state_change))
			wp->time[wp->state] += now - wp->last_state_change;
		wp->state = state;
		wp->last_state_change = now;
	}
}

static inline void wp_update_state(struct write_point *wp, bool running)
{
	enum write_point_state state;

	state = running			 ? WRITE_POINT_running :
		!list_empty(&wp->writes) ? WRITE_POINT_waiting_io
					 : WRITE_POINT_stopped;

	__wp_update_state(wp, state);
}

static CLOSURE_CALLBACK(bch2_write_index)
{
	closure_type(op, struct bch_write_op, cl);
	struct write_point *wp = op->wp;
	struct workqueue_struct *wq = index_update_wq(op);
	unsigned long flags;

	if ((op->flags & BCH_WRITE_DONE) &&
	    (op->flags & BCH_WRITE_MOVE))
		bch2_bio_free_pages_pool(op->c, &op->wbio.bio);

	spin_lock_irqsave(&wp->writes_lock, flags);
	if (wp->state == WRITE_POINT_waiting_io)
		__wp_update_state(wp, WRITE_POINT_waiting_work);
	list_add_tail(&op->wp_list, &wp->writes);
	spin_unlock_irqrestore (&wp->writes_lock, flags);

	queue_work(wq, &wp->index_update_work);
}

static inline void bch2_write_queue(struct bch_write_op *op, struct write_point *wp)
{
	op->wp = wp;

	if (wp->state == WRITE_POINT_stopped) {
		spin_lock_irq(&wp->writes_lock);
		__wp_update_state(wp, WRITE_POINT_waiting_io);
		spin_unlock_irq(&wp->writes_lock);
	}
}

void bch2_write_point_do_index_updates(struct work_struct *work)
{
	struct write_point *wp =
		container_of(work, struct write_point, index_update_work);
	struct bch_write_op *op;

	while (1) {
		spin_lock_irq(&wp->writes_lock);
		op = list_first_entry_or_null(&wp->writes, struct bch_write_op, wp_list);
		if (op)
			list_del(&op->wp_list);
		wp_update_state(wp, op != NULL);
		spin_unlock_irq(&wp->writes_lock);

		if (!op)
			break;

		op->flags |= BCH_WRITE_IN_WORKER;

		__bch2_write_index(op);

		if (!(op->flags & BCH_WRITE_DONE))
			__bch2_write(op);
		else
			bch2_write_done(&op->cl);
	}
}

static void bch2_write_endio(struct bio *bio)
{
	struct closure *cl		= bio->bi_private;
	struct bch_write_op *op		= container_of(cl, struct bch_write_op, cl);
	struct bch_write_bio *wbio	= to_wbio(bio);
	struct bch_write_bio *parent	= wbio->split ? wbio->parent : NULL;
	struct bch_fs *c		= wbio->c;
	struct bch_dev *ca		= bch_dev_bkey_exists(c, wbio->dev);

	if (bch2_dev_inum_io_err_on(bio->bi_status, ca, BCH_MEMBER_ERROR_write,
				    op->pos.inode,
				    wbio->inode_offset << 9,
				    "data write error: %s",
				    bch2_blk_status_to_str(bio->bi_status))) {
		set_bit(wbio->dev, op->failed.d);
		op->flags |= BCH_WRITE_IO_ERROR;
	}

	if (wbio->nocow)
		set_bit(wbio->dev, op->devs_need_flush->d);

	if (wbio->have_ioref) {
		bch2_latency_acct(ca, wbio->submit_time, WRITE);
		percpu_ref_put(&ca->io_ref);
	}

	if (wbio->bounce)
		bch2_bio_free_pages_pool(c, bio);

	if (wbio->put_bio)
		bio_put(bio);

	if (parent)
		bio_endio(&parent->bio);
	else
		closure_put(cl);
}

static void init_append_extent(struct bch_write_op *op,
			       struct write_point *wp,
			       struct bversion version,
			       struct bch_extent_crc_unpacked crc)
{
	struct bkey_i_extent *e;

	op->pos.offset += crc.uncompressed_size;

	e = bkey_extent_init(op->insert_keys.top);
	e->k.p		= op->pos;
	e->k.size	= crc.uncompressed_size;
	e->k.version	= version;

	if (crc.csum_type ||
	    crc.compression_type ||
	    crc.nonce)
		bch2_extent_crc_append(&e->k_i, crc);

	bch2_alloc_sectors_append_ptrs_inlined(op->c, wp, &e->k_i, crc.compressed_size,
				       op->flags & BCH_WRITE_CACHED);

	bch2_keylist_push(&op->insert_keys);
}

static struct bio *bch2_write_bio_alloc(struct bch_fs *c,
					struct write_point *wp,
					struct bio *src,
					bool *page_alloc_failed,
					void *buf)
{
	struct bch_write_bio *wbio;
	struct bio *bio;
	unsigned output_available =
		min(wp->sectors_free << 9, src->bi_iter.bi_size);
	unsigned pages = DIV_ROUND_UP(output_available +
				      (buf
				       ? ((unsigned long) buf & (PAGE_SIZE - 1))
				       : 0), PAGE_SIZE);

	pages = min(pages, BIO_MAX_VECS);

	bio = bio_alloc_bioset(NULL, pages, 0,
			       GFP_NOFS, &c->bio_write);
	wbio			= wbio_init(bio);
	wbio->put_bio		= true;
	/* copy WRITE_SYNC flag */
	wbio->bio.bi_opf	= src->bi_opf;

	if (buf) {
		bch2_bio_map(bio, buf, output_available);
		return bio;
	}

	wbio->bounce		= true;

	/*
	 * We can't use mempool for more than c->sb.encoded_extent_max
	 * worth of pages, but we'd like to allocate more if we can:
	 */
	bch2_bio_alloc_pages_pool(c, bio,
				  min_t(unsigned, output_available,
					c->opts.encoded_extent_max));

	if (bio->bi_iter.bi_size < output_available)
		*page_alloc_failed =
			bch2_bio_alloc_pages(bio,
					     output_available -
					     bio->bi_iter.bi_size,
					     GFP_NOFS) != 0;

	return bio;
}

static int bch2_write_rechecksum(struct bch_fs *c,
				 struct bch_write_op *op,
				 unsigned new_csum_type)
{
	struct bio *bio = &op->wbio.bio;
	struct bch_extent_crc_unpacked new_crc;
	int ret;

	/* bch2_rechecksum_bio() can't encrypt or decrypt data: */

	if (bch2_csum_type_is_encryption(op->crc.csum_type) !=
	    bch2_csum_type_is_encryption(new_csum_type))
		new_csum_type = op->crc.csum_type;

	ret = bch2_rechecksum_bio(c, bio, op->version, op->crc,
				  NULL, &new_crc,
				  op->crc.offset, op->crc.live_size,
				  new_csum_type);
	if (ret)
		return ret;

	bio_advance(bio, op->crc.offset << 9);
	bio->bi_iter.bi_size = op->crc.live_size << 9;
	op->crc = new_crc;
	return 0;
}

static int bch2_write_decrypt(struct bch_write_op *op)
{
	struct bch_fs *c = op->c;
	struct nonce nonce = extent_nonce(op->version, op->crc);
	struct bch_csum csum;
	int ret;

	if (!bch2_csum_type_is_encryption(op->crc.csum_type))
		return 0;

	/*
	 * If we need to decrypt data in the write path, we'll no longer be able
	 * to verify the existing checksum (poly1305 mac, in this case) after
	 * it's decrypted - this is the last point we'll be able to reverify the
	 * checksum:
	 */
	csum = bch2_checksum_bio(c, op->crc.csum_type, nonce, &op->wbio.bio);
	if (bch2_crc_cmp(op->crc.csum, csum) && !c->opts.no_data_io)
		return -EIO;

	ret = bch2_encrypt_bio(c, op->crc.csum_type, nonce, &op->wbio.bio);
	op->crc.csum_type = 0;
	op->crc.csum = (struct bch_csum) { 0, 0 };
	return ret;
}

static enum prep_encoded_ret {
	PREP_ENCODED_OK,
	PREP_ENCODED_ERR,
	PREP_ENCODED_CHECKSUM_ERR,
	PREP_ENCODED_DO_WRITE,
} bch2_write_prep_encoded_data(struct bch_write_op *op, struct write_point *wp)
{
	struct bch_fs *c = op->c;
	struct bio *bio = &op->wbio.bio;

	if (!(op->flags & BCH_WRITE_DATA_ENCODED))
		return PREP_ENCODED_OK;

	BUG_ON(bio_sectors(bio) != op->crc.compressed_size);

	/* Can we just write the entire extent as is? */
	if (op->crc.uncompressed_size == op->crc.live_size &&
	    op->crc.uncompressed_size <= c->opts.encoded_extent_max >> 9 &&
	    op->crc.compressed_size <= wp->sectors_free &&
	    (op->crc.compression_type == bch2_compression_opt_to_type(op->compression_opt) ||
	     op->incompressible)) {
		if (!crc_is_compressed(op->crc) &&
		    op->csum_type != op->crc.csum_type &&
		    bch2_write_rechecksum(c, op, op->csum_type) &&
		    !c->opts.no_data_io)
			return PREP_ENCODED_CHECKSUM_ERR;

		return PREP_ENCODED_DO_WRITE;
	}

	/*
	 * If the data is compressed and we couldn't write the entire extent as
	 * is, we have to decompress it:
	 */
	if (crc_is_compressed(op->crc)) {
		struct bch_csum csum;

		if (bch2_write_decrypt(op))
			return PREP_ENCODED_CHECKSUM_ERR;

		/* Last point we can still verify checksum: */
		csum = bch2_checksum_bio(c, op->crc.csum_type,
					 extent_nonce(op->version, op->crc),
					 bio);
		if (bch2_crc_cmp(op->crc.csum, csum) && !c->opts.no_data_io)
			return PREP_ENCODED_CHECKSUM_ERR;

		if (bch2_bio_uncompress_inplace(c, bio, &op->crc))
			return PREP_ENCODED_ERR;
	}

	/*
	 * No longer have compressed data after this point - data might be
	 * encrypted:
	 */

	/*
	 * If the data is checksummed and we're only writing a subset,
	 * rechecksum and adjust bio to point to currently live data:
	 */
	if ((op->crc.live_size != op->crc.uncompressed_size ||
	     op->crc.csum_type != op->csum_type) &&
	    bch2_write_rechecksum(c, op, op->csum_type) &&
	    !c->opts.no_data_io)
		return PREP_ENCODED_CHECKSUM_ERR;

	/*
	 * If we want to compress the data, it has to be decrypted:
	 */
	if ((op->compression_opt ||
	     bch2_csum_type_is_encryption(op->crc.csum_type) !=
	     bch2_csum_type_is_encryption(op->csum_type)) &&
	    bch2_write_decrypt(op))
		return PREP_ENCODED_CHECKSUM_ERR;

	return PREP_ENCODED_OK;
}

static int bch2_write_extent(struct bch_write_op *op, struct write_point *wp,
			     struct bio **_dst)
{
	struct bch_fs *c = op->c;
	struct bio *src = &op->wbio.bio, *dst = src;
	struct bvec_iter saved_iter;
	void *ec_buf;
	unsigned total_output = 0, total_input = 0;
	bool bounce = false;
	bool page_alloc_failed = false;
	int ret, more = 0;

	BUG_ON(!bio_sectors(src));

	ec_buf = bch2_writepoint_ec_buf(c, wp);

	switch (bch2_write_prep_encoded_data(op, wp)) {
	case PREP_ENCODED_OK:
		break;
	case PREP_ENCODED_ERR:
		ret = -EIO;
		goto err;
	case PREP_ENCODED_CHECKSUM_ERR:
		goto csum_err;
	case PREP_ENCODED_DO_WRITE:
		/* XXX look for bug here */
		if (ec_buf) {
			dst = bch2_write_bio_alloc(c, wp, src,
						   &page_alloc_failed,
						   ec_buf);
			bio_copy_data(dst, src);
			bounce = true;
		}
		init_append_extent(op, wp, op->version, op->crc);
		goto do_write;
	}

	if (ec_buf ||
	    op->compression_opt ||
	    (op->csum_type &&
	     !(op->flags & BCH_WRITE_PAGES_STABLE)) ||
	    (bch2_csum_type_is_encryption(op->csum_type) &&
	     !(op->flags & BCH_WRITE_PAGES_OWNED))) {
		dst = bch2_write_bio_alloc(c, wp, src,
					   &page_alloc_failed,
					   ec_buf);
		bounce = true;
	}

	saved_iter = dst->bi_iter;

	do {
		struct bch_extent_crc_unpacked crc = { 0 };
		struct bversion version = op->version;
		size_t dst_len = 0, src_len = 0;

		if (page_alloc_failed &&
		    dst->bi_iter.bi_size  < (wp->sectors_free << 9) &&
		    dst->bi_iter.bi_size < c->opts.encoded_extent_max)
			break;

		BUG_ON(op->compression_opt &&
		       (op->flags & BCH_WRITE_DATA_ENCODED) &&
		       bch2_csum_type_is_encryption(op->crc.csum_type));
		BUG_ON(op->compression_opt && !bounce);

		crc.compression_type = op->incompressible
			? BCH_COMPRESSION_TYPE_incompressible
			: op->compression_opt
			? bch2_bio_compress(c, dst, &dst_len, src, &src_len,
					    op->compression_opt)
			: 0;
		if (!crc_is_compressed(crc)) {
			dst_len = min(dst->bi_iter.bi_size, src->bi_iter.bi_size);
			dst_len = min_t(unsigned, dst_len, wp->sectors_free << 9);

			if (op->csum_type)
				dst_len = min_t(unsigned, dst_len,
						c->opts.encoded_extent_max);

			if (bounce) {
				swap(dst->bi_iter.bi_size, dst_len);
				bio_copy_data(dst, src);
				swap(dst->bi_iter.bi_size, dst_len);
			}

			src_len = dst_len;
		}

		BUG_ON(!src_len || !dst_len);

		if (bch2_csum_type_is_encryption(op->csum_type)) {
			if (bversion_zero(version)) {
				version.lo = atomic64_inc_return(&c->key_version);
			} else {
				crc.nonce = op->nonce;
				op->nonce += src_len >> 9;
			}
		}

		if ((op->flags & BCH_WRITE_DATA_ENCODED) &&
		    !crc_is_compressed(crc) &&
		    bch2_csum_type_is_encryption(op->crc.csum_type) ==
		    bch2_csum_type_is_encryption(op->csum_type)) {
			u8 compression_type = crc.compression_type;
			u16 nonce = crc.nonce;
			/*
			 * Note: when we're using rechecksum(), we need to be
			 * checksumming @src because it has all the data our
			 * existing checksum covers - if we bounced (because we
			 * were trying to compress), @dst will only have the
			 * part of the data the new checksum will cover.
			 *
			 * But normally we want to be checksumming post bounce,
			 * because part of the reason for bouncing is so the
			 * data can't be modified (by userspace) while it's in
			 * flight.
			 */
			if (bch2_rechecksum_bio(c, src, version, op->crc,
					&crc, &op->crc,
					src_len >> 9,
					bio_sectors(src) - (src_len >> 9),
					op->csum_type))
				goto csum_err;
			/*
			 * rchecksum_bio sets compression_type on crc from op->crc,
			 * this isn't always correct as sometimes we're changing
			 * an extent from uncompressed to incompressible.
			 */
			crc.compression_type = compression_type;
			crc.nonce = nonce;
		} else {
			if ((op->flags & BCH_WRITE_DATA_ENCODED) &&
			    bch2_rechecksum_bio(c, src, version, op->crc,
					NULL, &op->crc,
					src_len >> 9,
					bio_sectors(src) - (src_len >> 9),
					op->crc.csum_type))
				goto csum_err;

			crc.compressed_size	= dst_len >> 9;
			crc.uncompressed_size	= src_len >> 9;
			crc.live_size		= src_len >> 9;

			swap(dst->bi_iter.bi_size, dst_len);
			ret = bch2_encrypt_bio(c, op->csum_type,
					       extent_nonce(version, crc), dst);
			if (ret)
				goto err;

			crc.csum = bch2_checksum_bio(c, op->csum_type,
					 extent_nonce(version, crc), dst);
			crc.csum_type = op->csum_type;
			swap(dst->bi_iter.bi_size, dst_len);
		}

		init_append_extent(op, wp, version, crc);

		if (dst != src)
			bio_advance(dst, dst_len);
		bio_advance(src, src_len);
		total_output	+= dst_len;
		total_input	+= src_len;
	} while (dst->bi_iter.bi_size &&
		 src->bi_iter.bi_size &&
		 wp->sectors_free &&
		 !bch2_keylist_realloc(&op->insert_keys,
				      op->inline_keys,
				      ARRAY_SIZE(op->inline_keys),
				      BKEY_EXTENT_U64s_MAX));

	more = src->bi_iter.bi_size != 0;

	dst->bi_iter = saved_iter;

	if (dst == src && more) {
		BUG_ON(total_output != total_input);

		dst = bio_split(src, total_input >> 9,
				GFP_NOFS, &c->bio_write);
		wbio_init(dst)->put_bio	= true;
		/* copy WRITE_SYNC flag */
		dst->bi_opf		= src->bi_opf;
	}

	dst->bi_iter.bi_size = total_output;
do_write:
	*_dst = dst;
	return more;
csum_err:
	bch_err(c, "%s writ error: error verifying existing checksum while rewriting existing data (memory corruption?)",
		op->flags & BCH_WRITE_MOVE ? "move" : "user");
	ret = -EIO;
err:
	if (to_wbio(dst)->bounce)
		bch2_bio_free_pages_pool(c, dst);
	if (to_wbio(dst)->put_bio)
		bio_put(dst);

	return ret;
}

static bool bch2_extent_is_writeable(struct bch_write_op *op,
				     struct bkey_s_c k)
{
	struct bch_fs *c = op->c;
	struct bkey_s_c_extent e;
	struct extent_ptr_decoded p;
	const union bch_extent_entry *entry;
	unsigned replicas = 0;

	if (k.k->type != KEY_TYPE_extent)
		return false;

	e = bkey_s_c_to_extent(k);
	extent_for_each_ptr_decode(e, p, entry) {
		if (crc_is_encoded(p.crc) || p.has_ec)
			return false;

		replicas += bch2_extent_ptr_durability(c, &p);
	}

	return replicas >= op->opts.data_replicas;
}

static inline void bch2_nocow_write_unlock(struct bch_write_op *op)
{
	struct bch_fs *c = op->c;

	for_each_keylist_key(&op->insert_keys, k) {
		struct bkey_ptrs_c ptrs = bch2_bkey_ptrs_c(bkey_i_to_s_c(k));

		bkey_for_each_ptr(ptrs, ptr)
			bch2_bucket_nocow_unlock(&c->nocow_locks,
						 PTR_BUCKET_POS(c, ptr),
						 BUCKET_NOCOW_LOCK_UPDATE);
	}
}

static int bch2_nocow_write_convert_one_unwritten(struct btree_trans *trans,
						  struct btree_iter *iter,
						  struct bkey_i *orig,
						  struct bkey_s_c k,
						  u64 new_i_size)
{
	if (!bch2_extents_match(bkey_i_to_s_c(orig), k)) {
		/* trace this */
		return 0;
	}

	struct bkey_i *new = bch2_bkey_make_mut_noupdate(trans, k);
	int ret = PTR_ERR_OR_ZERO(new);
	if (ret)
		return ret;

	bch2_cut_front(bkey_start_pos(&orig->k), new);
	bch2_cut_back(orig->k.p, new);

	struct bkey_ptrs ptrs = bch2_bkey_ptrs(bkey_i_to_s(new));
	bkey_for_each_ptr(ptrs, ptr)
		ptr->unwritten = 0;

	/*
	 * Note that we're not calling bch2_subvol_get_snapshot() in this path -
	 * that was done when we kicked off the write, and here it's important
	 * that we update the extent that we wrote to - even if a snapshot has
	 * since been created. The write is still outstanding, so we're ok
	 * w.r.t. snapshot atomicity:
	 */
	return  bch2_extent_update_i_size_sectors(trans, iter,
					min(new->k.p.offset << 9, new_i_size), 0) ?:
		bch2_trans_update(trans, iter, new,
				  BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE);
}

static void bch2_nocow_write_convert_unwritten(struct bch_write_op *op)
{
	struct bch_fs *c = op->c;
	struct btree_trans *trans = bch2_trans_get(c);

	for_each_keylist_key(&op->insert_keys, orig) {
		int ret = for_each_btree_key_upto_commit(trans, iter, BTREE_ID_extents,
				     bkey_start_pos(&orig->k), orig->k.p,
				     BTREE_ITER_INTENT, k,
				     NULL, NULL, BCH_TRANS_COMMIT_no_enospc, ({
			bch2_nocow_write_convert_one_unwritten(trans, &iter, orig, k, op->new_i_size);
		}));

		if (ret && !bch2_err_matches(ret, EROFS)) {
			struct bkey_i *insert = bch2_keylist_front(&op->insert_keys);

			bch_err_inum_offset_ratelimited(c,
				insert->k.p.inode, insert->k.p.offset << 9,
				"%s write error while doing btree update: %s",
				op->flags & BCH_WRITE_MOVE ? "move" : "user",
				bch2_err_str(ret));
		}

		if (ret) {
			op->error = ret;
			break;
		}
	}

	bch2_trans_put(trans);
}

static void __bch2_nocow_write_done(struct bch_write_op *op)
{
	bch2_nocow_write_unlock(op);

	if (unlikely(op->flags & BCH_WRITE_IO_ERROR)) {
		op->error = -EIO;
	} else if (unlikely(op->flags & BCH_WRITE_CONVERT_UNWRITTEN))
		bch2_nocow_write_convert_unwritten(op);
}

static CLOSURE_CALLBACK(bch2_nocow_write_done)
{
	closure_type(op, struct bch_write_op, cl);

	__bch2_nocow_write_done(op);
	bch2_write_done(cl);
}

struct bucket_to_lock {
	struct bpos		b;
	unsigned		gen;
	struct nocow_lock_bucket *l;
};

static void bch2_nocow_write(struct bch_write_op *op)
{
	struct bch_fs *c = op->c;
	struct btree_trans *trans;
	struct btree_iter iter;
	struct bkey_s_c k;
	DARRAY_PREALLOCATED(struct bucket_to_lock, 3) buckets;
	u32 snapshot;
	struct bucket_to_lock *stale_at;
	int ret;

	if (op->flags & BCH_WRITE_MOVE)
		return;

	darray_init(&buckets);
	trans = bch2_trans_get(c);
retry:
	bch2_trans_begin(trans);

	ret = bch2_subvolume_get_snapshot(trans, op->subvol, &snapshot);
	if (unlikely(ret))
		goto err;

	bch2_trans_iter_init(trans, &iter, BTREE_ID_extents,
			     SPOS(op->pos.inode, op->pos.offset, snapshot),
			     BTREE_ITER_SLOTS);
	while (1) {
		struct bio *bio = &op->wbio.bio;

		buckets.nr = 0;

		k = bch2_btree_iter_peek_slot(&iter);
		ret = bkey_err(k);
		if (ret)
			break;

		/* fall back to normal cow write path? */
		if (unlikely(k.k->p.snapshot != snapshot ||
			     !bch2_extent_is_writeable(op, k)))
			break;

		if (bch2_keylist_realloc(&op->insert_keys,
					 op->inline_keys,
					 ARRAY_SIZE(op->inline_keys),
					 k.k->u64s))
			break;

		/* Get iorefs before dropping btree locks: */
		struct bkey_ptrs_c ptrs = bch2_bkey_ptrs_c(k);
		bkey_for_each_ptr(ptrs, ptr) {
			struct bpos b = PTR_BUCKET_POS(c, ptr);
			struct nocow_lock_bucket *l =
				bucket_nocow_lock(&c->nocow_locks, bucket_to_u64(b));
			prefetch(l);

			if (unlikely(!bch2_dev_get_ioref(bch_dev_bkey_exists(c, ptr->dev), WRITE)))
				goto err_get_ioref;

			/* XXX allocating memory with btree locks held - rare */
			darray_push_gfp(&buckets, ((struct bucket_to_lock) {
						   .b = b, .gen = ptr->gen, .l = l,
						   }), GFP_KERNEL|__GFP_NOFAIL);

			if (ptr->unwritten)
				op->flags |= BCH_WRITE_CONVERT_UNWRITTEN;
		}

		/* Unlock before taking nocow locks, doing IO: */
		bkey_reassemble(op->insert_keys.top, k);
		bch2_trans_unlock(trans);

		bch2_cut_front(op->pos, op->insert_keys.top);
		if (op->flags & BCH_WRITE_CONVERT_UNWRITTEN)
			bch2_cut_back(POS(op->pos.inode, op->pos.offset + bio_sectors(bio)), op->insert_keys.top);

		darray_for_each(buckets, i) {
			struct bch_dev *ca = bch_dev_bkey_exists(c, i->b.inode);

			__bch2_bucket_nocow_lock(&c->nocow_locks, i->l,
						 bucket_to_u64(i->b),
						 BUCKET_NOCOW_LOCK_UPDATE);

			rcu_read_lock();
			bool stale = gen_after(*bucket_gen(ca, i->b.offset), i->gen);
			rcu_read_unlock();

			if (unlikely(stale)) {
				stale_at = i;
				goto err_bucket_stale;
			}
		}

		bio = &op->wbio.bio;
		if (k.k->p.offset < op->pos.offset + bio_sectors(bio)) {
			bio = bio_split(bio, k.k->p.offset - op->pos.offset,
					GFP_KERNEL, &c->bio_write);
			wbio_init(bio)->put_bio = true;
			bio->bi_opf = op->wbio.bio.bi_opf;
		} else {
			op->flags |= BCH_WRITE_DONE;
		}

		op->pos.offset += bio_sectors(bio);
		op->written += bio_sectors(bio);

		bio->bi_end_io	= bch2_write_endio;
		bio->bi_private	= &op->cl;
		bio->bi_opf |= REQ_OP_WRITE;
		closure_get(&op->cl);
		bch2_submit_wbio_replicas(to_wbio(bio), c, BCH_DATA_user,
					  op->insert_keys.top, true);

		bch2_keylist_push(&op->insert_keys);
		if (op->flags & BCH_WRITE_DONE)
			break;
		bch2_btree_iter_advance(&iter);
	}
out:
	bch2_trans_iter_exit(trans, &iter);
err:
	if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
		goto retry;

	if (ret) {
		bch_err_inum_offset_ratelimited(c,
			op->pos.inode, op->pos.offset << 9,
			"%s: btree lookup error %s", __func__, bch2_err_str(ret));
		op->error = ret;
		op->flags |= BCH_WRITE_DONE;
	}

	bch2_trans_put(trans);
	darray_exit(&buckets);

	/* fallback to cow write path? */
	if (!(op->flags & BCH_WRITE_DONE)) {
		closure_sync(&op->cl);
		__bch2_nocow_write_done(op);
		op->insert_keys.top = op->insert_keys.keys;
	} else if (op->flags & BCH_WRITE_SYNC) {
		closure_sync(&op->cl);
		bch2_nocow_write_done(&op->cl.work);
	} else {
		/*
		 * XXX
		 * needs to run out of process context because ei_quota_lock is
		 * a mutex
		 */
		continue_at(&op->cl, bch2_nocow_write_done, index_update_wq(op));
	}
	return;
err_get_ioref:
	darray_for_each(buckets, i)
		percpu_ref_put(&bch_dev_bkey_exists(c, i->b.inode)->io_ref);

	/* Fall back to COW path: */
	goto out;
err_bucket_stale:
	darray_for_each(buckets, i) {
		bch2_bucket_nocow_unlock(&c->nocow_locks, i->b, BUCKET_NOCOW_LOCK_UPDATE);
		if (i == stale_at)
			break;
	}

	/* We can retry this: */
	ret = -BCH_ERR_transaction_restart;
	goto err_get_ioref;
}

static void __bch2_write(struct bch_write_op *op)
{
	struct bch_fs *c = op->c;
	struct write_point *wp = NULL;
	struct bio *bio = NULL;
	unsigned nofs_flags;
	int ret;

	nofs_flags = memalloc_nofs_save();

	if (unlikely(op->opts.nocow && c->opts.nocow_enabled)) {
		bch2_nocow_write(op);
		if (op->flags & BCH_WRITE_DONE)
			goto out_nofs_restore;
	}
again:
	memset(&op->failed, 0, sizeof(op->failed));

	do {
		struct bkey_i *key_to_write;
		unsigned key_to_write_offset = op->insert_keys.top_p -
			op->insert_keys.keys_p;

		/* +1 for possible cache device: */
		if (op->open_buckets.nr + op->nr_replicas + 1 >
		    ARRAY_SIZE(op->open_buckets.v))
			break;

		if (bch2_keylist_realloc(&op->insert_keys,
					op->inline_keys,
					ARRAY_SIZE(op->inline_keys),
					BKEY_EXTENT_U64s_MAX))
			break;

		/*
		 * The copygc thread is now global, which means it's no longer
		 * freeing up space on specific disks, which means that
		 * allocations for specific disks may hang arbitrarily long:
		 */
		ret = bch2_trans_do(c, NULL, NULL, 0,
			bch2_alloc_sectors_start_trans(trans,
				op->target,
				op->opts.erasure_code && !(op->flags & BCH_WRITE_CACHED),
				op->write_point,
				&op->devs_have,
				op->nr_replicas,
				op->nr_replicas_required,
				op->watermark,
				op->flags,
				(op->flags & (BCH_WRITE_ALLOC_NOWAIT|
					      BCH_WRITE_ONLY_SPECIFIED_DEVS))
				? NULL : &op->cl, &wp));
		if (unlikely(ret)) {
			if (bch2_err_matches(ret, BCH_ERR_operation_blocked))
				break;

			goto err;
		}

		EBUG_ON(!wp);

		bch2_open_bucket_get(c, wp, &op->open_buckets);
		ret = bch2_write_extent(op, wp, &bio);

		bch2_alloc_sectors_done_inlined(c, wp);
err:
		if (ret <= 0) {
			op->flags |= BCH_WRITE_DONE;

			if (ret < 0) {
				if (!(op->flags & BCH_WRITE_ALLOC_NOWAIT))
					bch_err_inum_offset_ratelimited(c,
						op->pos.inode,
						op->pos.offset << 9,
						"%s(): %s error: %s", __func__,
						op->flags & BCH_WRITE_MOVE ? "move" : "user",
						bch2_err_str(ret));
				op->error = ret;
				break;
			}
		}

		bio->bi_end_io	= bch2_write_endio;
		bio->bi_private	= &op->cl;
		bio->bi_opf |= REQ_OP_WRITE;

		closure_get(bio->bi_private);

		key_to_write = (void *) (op->insert_keys.keys_p +
					 key_to_write_offset);

		bch2_submit_wbio_replicas(to_wbio(bio), c, BCH_DATA_user,
					  key_to_write, false);
	} while (ret);

	/*
	 * Sync or no?
	 *
	 * If we're running asynchronously, wne may still want to block
	 * synchronously here if we weren't able to submit all of the IO at
	 * once, as that signals backpressure to the caller.
	 */
	if ((op->flags & BCH_WRITE_SYNC) ||
	    (!(op->flags & BCH_WRITE_DONE) &&
	     !(op->flags & BCH_WRITE_IN_WORKER))) {
		closure_sync(&op->cl);
		__bch2_write_index(op);

		if (!(op->flags & BCH_WRITE_DONE))
			goto again;
		bch2_write_done(&op->cl);
	} else {
		bch2_write_queue(op, wp);
		continue_at(&op->cl, bch2_write_index, NULL);
	}
out_nofs_restore:
	memalloc_nofs_restore(nofs_flags);
}

static void bch2_write_data_inline(struct bch_write_op *op, unsigned data_len)
{
	struct bio *bio = &op->wbio.bio;
	struct bvec_iter iter;
	struct bkey_i_inline_data *id;
	unsigned sectors;
	int ret;

	op->flags |= BCH_WRITE_WROTE_DATA_INLINE;
	op->flags |= BCH_WRITE_DONE;

	bch2_check_set_feature(op->c, BCH_FEATURE_inline_data);

	ret = bch2_keylist_realloc(&op->insert_keys, op->inline_keys,
				   ARRAY_SIZE(op->inline_keys),
				   BKEY_U64s + DIV_ROUND_UP(data_len, 8));
	if (ret) {
		op->error = ret;
		goto err;
	}

	sectors = bio_sectors(bio);
	op->pos.offset += sectors;

	id = bkey_inline_data_init(op->insert_keys.top);
	id->k.p		= op->pos;
	id->k.version	= op->version;
	id->k.size	= sectors;

	iter = bio->bi_iter;
	iter.bi_size = data_len;
	memcpy_from_bio(id->v.data, bio, iter);

	while (data_len & 7)
		id->v.data[data_len++] = '\0';
	set_bkey_val_bytes(&id->k, data_len);
	bch2_keylist_push(&op->insert_keys);

	__bch2_write_index(op);
err:
	bch2_write_done(&op->cl);
}

/**
 * bch2_write() - handle a write to a cache device or flash only volume
 * @cl:		&bch_write_op->cl
 *
 * This is the starting point for any data to end up in a cache device; it could
 * be from a normal write, or a writeback write, or a write to a flash only
 * volume - it's also used by the moving garbage collector to compact data in
 * mostly empty buckets.
 *
 * It first writes the data to the cache, creating a list of keys to be inserted
 * (if the data won't fit in a single open bucket, there will be multiple keys);
 * after the data is written it calls bch_journal, and after the keys have been
 * added to the next journal write they're inserted into the btree.
 *
 * If op->discard is true, instead of inserting the data it invalidates the
 * region of the cache represented by op->bio and op->inode.
 */
CLOSURE_CALLBACK(bch2_write)
{
	closure_type(op, struct bch_write_op, cl);
	struct bio *bio = &op->wbio.bio;
	struct bch_fs *c = op->c;
	unsigned data_len;

	EBUG_ON(op->cl.parent);
	BUG_ON(!op->nr_replicas);
	BUG_ON(!op->write_point.v);
	BUG_ON(bkey_eq(op->pos, POS_MAX));

	op->nr_replicas_required = min_t(unsigned, op->nr_replicas_required, op->nr_replicas);
	op->start_time = local_clock();
	bch2_keylist_init(&op->insert_keys, op->inline_keys);
	wbio_init(bio)->put_bio = false;

	if (bio->bi_iter.bi_size & (c->opts.block_size - 1)) {
		bch_err_inum_offset_ratelimited(c,
			op->pos.inode,
			op->pos.offset << 9,
			"%s write error: misaligned write",
			op->flags & BCH_WRITE_MOVE ? "move" : "user");
		op->error = -EIO;
		goto err;
	}

	if (c->opts.nochanges) {
		op->error = -BCH_ERR_erofs_no_writes;
		goto err;
	}

	if (!(op->flags & BCH_WRITE_MOVE) &&
	    !bch2_write_ref_tryget(c, BCH_WRITE_REF_write)) {
		op->error = -BCH_ERR_erofs_no_writes;
		goto err;
	}

	this_cpu_add(c->counters[BCH_COUNTER_io_write], bio_sectors(bio));
	bch2_increment_clock(c, bio_sectors(bio), WRITE);

	data_len = min_t(u64, bio->bi_iter.bi_size,
			 op->new_i_size - (op->pos.offset << 9));

	if (c->opts.inline_data &&
	    data_len <= min(block_bytes(c) / 2, 1024U)) {
		bch2_write_data_inline(op, data_len);
		return;
	}

	__bch2_write(op);
	return;
err:
	bch2_disk_reservation_put(c, &op->res);

	closure_debug_destroy(&op->cl);
	if (op->end_io)
		op->end_io(op);
}

static const char * const bch2_write_flags[] = {
#define x(f)	#f,
	BCH_WRITE_FLAGS()
#undef x
	NULL
};

void bch2_write_op_to_text(struct printbuf *out, struct bch_write_op *op)
{
	prt_str(out, "pos: ");
	bch2_bpos_to_text(out, op->pos);
	prt_newline(out);
	printbuf_indent_add(out, 2);

	prt_str(out, "started: ");
	bch2_pr_time_units(out, local_clock() - op->start_time);
	prt_newline(out);

	prt_str(out, "flags: ");
	prt_bitflags(out, bch2_write_flags, op->flags);
	prt_newline(out);

	prt_printf(out, "ref: %u", closure_nr_remaining(&op->cl));
	prt_newline(out);

	printbuf_indent_sub(out, 2);
}

void bch2_fs_io_write_exit(struct bch_fs *c)
{
	mempool_exit(&c->bio_bounce_pages);
	bioset_exit(&c->bio_write);
}

int bch2_fs_io_write_init(struct bch_fs *c)
{
	if (bioset_init(&c->bio_write, 1, offsetof(struct bch_write_bio, bio),
			BIOSET_NEED_BVECS))
		return -BCH_ERR_ENOMEM_bio_write_init;

	if (mempool_init_page_pool(&c->bio_bounce_pages,
				   max_t(unsigned,
					 c->opts.btree_node_size,
					 c->opts.encoded_extent_max) /
				   PAGE_SIZE, 0))
		return -BCH_ERR_ENOMEM_bio_bounce_pages_init;

	return 0;
}