aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/md/bcache/btree.c
blob: f9764e61978b5749487862b5ab88eb73b13f18ba (plain) (blame)
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
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
/*
 * Copyright (C) 2010 Kent Overstreet <kent.overstreet@gmail.com>
 *
 * Uses a block device as cache for other block devices; optimized for SSDs.
 * All allocation is done in buckets, which should match the erase block size
 * of the device.
 *
 * Buckets containing cached data are kept on a heap sorted by priority;
 * bucket priority is increased on cache hit, and periodically all the buckets
 * on the heap have their priority scaled down. This currently is just used as
 * an LRU but in the future should allow for more intelligent heuristics.
 *
 * Buckets have an 8 bit counter; freeing is accomplished by incrementing the
 * counter. Garbage collection is used to remove stale pointers.
 *
 * Indexing is done via a btree; nodes are not necessarily fully sorted, rather
 * as keys are inserted we only sort the pages that have not yet been written.
 * When garbage collection is run, we resort the entire node.
 *
 * All configuration is done via sysfs; see Documentation/bcache.txt.
 */

#include "bcache.h"
#include "btree.h"
#include "debug.h"
#include "request.h"
#include "writeback.h"

#include <linux/slab.h>
#include <linux/bitops.h>
#include <linux/hash.h>
#include <linux/prefetch.h>
#include <linux/random.h>
#include <linux/rcupdate.h>
#include <trace/events/bcache.h>

/*
 * Todo:
 * register_bcache: Return errors out to userspace correctly
 *
 * Writeback: don't undirty key until after a cache flush
 *
 * Create an iterator for key pointers
 *
 * On btree write error, mark bucket such that it won't be freed from the cache
 *
 * Journalling:
 *   Check for bad keys in replay
 *   Propagate barriers
 *   Refcount journal entries in journal_replay
 *
 * Garbage collection:
 *   Finish incremental gc
 *   Gc should free old UUIDs, data for invalid UUIDs
 *
 * Provide a way to list backing device UUIDs we have data cached for, and
 * probably how long it's been since we've seen them, and a way to invalidate
 * dirty data for devices that will never be attached again
 *
 * Keep 1 min/5 min/15 min statistics of how busy a block device has been, so
 * that based on that and how much dirty data we have we can keep writeback
 * from being starved
 *
 * Add a tracepoint or somesuch to watch for writeback starvation
 *
 * When btree depth > 1 and splitting an interior node, we have to make sure
 * alloc_bucket() cannot fail. This should be true but is not completely
 * obvious.
 *
 * Make sure all allocations get charged to the root cgroup
 *
 * Plugging?
 *
 * If data write is less than hard sector size of ssd, round up offset in open
 * bucket to the next whole sector
 *
 * Also lookup by cgroup in get_open_bucket()
 *
 * Superblock needs to be fleshed out for multiple cache devices
 *
 * Add a sysfs tunable for the number of writeback IOs in flight
 *
 * Add a sysfs tunable for the number of open data buckets
 *
 * IO tracking: Can we track when one process is doing io on behalf of another?
 * IO tracking: Don't use just an average, weigh more recent stuff higher
 *
 * Test module load/unload
 */

static const char * const op_types[] = {
	"insert", "replace"
};

static const char *op_type(struct btree_op *op)
{
	return op_types[op->type];
}

#define MAX_NEED_GC		64
#define MAX_SAVE_PRIO		72

#define PTR_DIRTY_BIT		(((uint64_t) 1 << 36))

#define PTR_HASH(c, k)							\
	(((k)->ptr[0] >> c->bucket_bits) | PTR_GEN(k, 0))

struct workqueue_struct *bch_gc_wq;
static struct workqueue_struct *btree_io_wq;

void bch_btree_op_init_stack(struct btree_op *op)
{
	memset(op, 0, sizeof(struct btree_op));
	closure_init_stack(&op->cl);
	op->lock = -1;
	bch_keylist_init(&op->keys);
}

/* Btree key manipulation */

static void bkey_put(struct cache_set *c, struct bkey *k, int level)
{
	if ((level && KEY_OFFSET(k)) || !level)
		__bkey_put(c, k);
}

/* Btree IO */

static uint64_t btree_csum_set(struct btree *b, struct bset *i)
{
	uint64_t crc = b->key.ptr[0];
	void *data = (void *) i + 8, *end = end(i);

	crc = bch_crc64_update(crc, data, end - data);
	return crc ^ 0xffffffffffffffffULL;
}

static void bch_btree_node_read_done(struct btree *b)
{
	const char *err = "bad btree header";
	struct bset *i = b->sets[0].data;
	struct btree_iter *iter;

	iter = mempool_alloc(b->c->fill_iter, GFP_NOWAIT);
	iter->size = b->c->sb.bucket_size / b->c->sb.block_size;
	iter->used = 0;

	if (!i->seq)
		goto err;

	for (;
	     b->written < btree_blocks(b) && i->seq == b->sets[0].data->seq;
	     i = write_block(b)) {
		err = "unsupported bset version";
		if (i->version > BCACHE_BSET_VERSION)
			goto err;

		err = "bad btree header";
		if (b->written + set_blocks(i, b->c) > btree_blocks(b))
			goto err;

		err = "bad magic";
		if (i->magic != bset_magic(b->c))
			goto err;

		err = "bad checksum";
		switch (i->version) {
		case 0:
			if (i->csum != csum_set(i))
				goto err;
			break;
		case BCACHE_BSET_VERSION:
			if (i->csum != btree_csum_set(b, i))
				goto err;
			break;
		}

		err = "empty set";
		if (i != b->sets[0].data && !i->keys)
			goto err;

		bch_btree_iter_push(iter, i->start, end(i));

		b->written += set_blocks(i, b->c);
	}

	err = "corrupted btree";
	for (i = write_block(b);
	     index(i, b) < btree_blocks(b);
	     i = ((void *) i) + block_bytes(b->c))
		if (i->seq == b->sets[0].data->seq)
			goto err;

	bch_btree_sort_and_fix_extents(b, iter);

	i = b->sets[0].data;
	err = "short btree key";
	if (b->sets[0].size &&
	    bkey_cmp(&b->key, &b->sets[0].end) < 0)
		goto err;

	if (b->written < btree_blocks(b))
		bch_bset_init_next(b);
out:
	mempool_free(iter, b->c->fill_iter);
	return;
err:
	set_btree_node_io_error(b);
	bch_cache_set_error(b->c, "%s at bucket %zu, block %zu, %u keys",
			    err, PTR_BUCKET_NR(b->c, &b->key, 0),
			    index(i, b), i->keys);
	goto out;
}

static void btree_node_read_endio(struct bio *bio, int error)
{
	struct closure *cl = bio->bi_private;
	closure_put(cl);
}

void bch_btree_node_read(struct btree *b)
{
	uint64_t start_time = local_clock();
	struct closure cl;
	struct bio *bio;

	trace_bcache_btree_read(b);

	closure_init_stack(&cl);

	bio = bch_bbio_alloc(b->c);
	bio->bi_rw	= REQ_META|READ_SYNC;
	bio->bi_size	= KEY_SIZE(&b->key) << 9;
	bio->bi_end_io	= btree_node_read_endio;
	bio->bi_private	= &cl;

	bch_bio_map(bio, b->sets[0].data);

	bch_submit_bbio(bio, b->c, &b->key, 0);
	closure_sync(&cl);

	if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
		set_btree_node_io_error(b);

	bch_bbio_free(bio, b->c);

	if (btree_node_io_error(b))
		goto err;

	bch_btree_node_read_done(b);

	spin_lock(&b->c->btree_read_time_lock);
	bch_time_stats_update(&b->c->btree_read_time, start_time);
	spin_unlock(&b->c->btree_read_time_lock);

	return;
err:
	bch_cache_set_error(b->c, "io error reading bucket %lu",
			    PTR_BUCKET_NR(b->c, &b->key, 0));
}

static void btree_complete_write(struct btree *b, struct btree_write *w)
{
	if (w->prio_blocked &&
	    !atomic_sub_return(w->prio_blocked, &b->c->prio_blocked))
		wake_up_allocators(b->c);

	if (w->journal) {
		atomic_dec_bug(w->journal);
		__closure_wake_up(&b->c->journal.wait);
	}

	w->prio_blocked	= 0;
	w->journal	= NULL;
}

static void __btree_node_write_done(struct closure *cl)
{
	struct btree *b = container_of(cl, struct btree, io.cl);
	struct btree_write *w = btree_prev_write(b);

	bch_bbio_free(b->bio, b->c);
	b->bio = NULL;
	btree_complete_write(b, w);

	if (btree_node_dirty(b))
		queue_delayed_work(btree_io_wq, &b->work,
				   msecs_to_jiffies(30000));

	closure_return(cl);
}

static void btree_node_write_done(struct closure *cl)
{
	struct btree *b = container_of(cl, struct btree, io.cl);
	struct bio_vec *bv;
	int n;

	__bio_for_each_segment(bv, b->bio, n, 0)
		__free_page(bv->bv_page);

	__btree_node_write_done(cl);
}

static void btree_node_write_endio(struct bio *bio, int error)
{
	struct closure *cl = bio->bi_private;
	struct btree *b = container_of(cl, struct btree, io.cl);

	if (error)
		set_btree_node_io_error(b);

	bch_bbio_count_io_errors(b->c, bio, error, "writing btree");
	closure_put(cl);
}

static void do_btree_node_write(struct btree *b)
{
	struct closure *cl = &b->io.cl;
	struct bset *i = b->sets[b->nsets].data;
	BKEY_PADDED(key) k;

	i->version	= BCACHE_BSET_VERSION;
	i->csum		= btree_csum_set(b, i);

	BUG_ON(b->bio);
	b->bio = bch_bbio_alloc(b->c);

	b->bio->bi_end_io	= btree_node_write_endio;
	b->bio->bi_private	= &b->io.cl;
	b->bio->bi_rw		= REQ_META|WRITE_SYNC|REQ_FUA;
	b->bio->bi_size		= set_blocks(i, b->c) * block_bytes(b->c);
	bch_bio_map(b->bio, i);

	/*
	 * If we're appending to a leaf node, we don't technically need FUA -
	 * this write just needs to be persisted before the next journal write,
	 * which will be marked FLUSH|FUA.
	 *
	 * Similarly if we're writing a new btree root - the pointer is going to
	 * be in the next journal entry.
	 *
	 * But if we're writing a new btree node (that isn't a root) or
	 * appending to a non leaf btree node, we need either FUA or a flush
	 * when we write the parent with the new pointer. FUA is cheaper than a
	 * flush, and writes appending to leaf nodes aren't blocking anything so
	 * just make all btree node writes FUA to keep things sane.
	 */

	bkey_copy(&k.key, &b->key);
	SET_PTR_OFFSET(&k.key, 0, PTR_OFFSET(&k.key, 0) + bset_offset(b, i));

	if (!bio_alloc_pages(b->bio, GFP_NOIO)) {
		int j;
		struct bio_vec *bv;
		void *base = (void *) ((unsigned long) i & ~(PAGE_SIZE - 1));

		bio_for_each_segment(bv, b->bio, j)
			memcpy(page_address(bv->bv_page),
			       base + j * PAGE_SIZE, PAGE_SIZE);

		bch_submit_bbio(b->bio, b->c, &k.key, 0);

		continue_at(cl, btree_node_write_done, NULL);
	} else {
		b->bio->bi_vcnt = 0;
		bch_bio_map(b->bio, i);

		bch_submit_bbio(b->bio, b->c, &k.key, 0);

		closure_sync(cl);
		__btree_node_write_done(cl);
	}
}

void bch_btree_node_write(struct btree *b, struct closure *parent)
{
	struct bset *i = b->sets[b->nsets].data;

	trace_bcache_btree_write(b);

	BUG_ON(current->bio_list);
	BUG_ON(b->written >= btree_blocks(b));
	BUG_ON(b->written && !i->keys);
	BUG_ON(b->sets->data->seq != i->seq);
	bch_check_key_order(b, i);

	cancel_delayed_work(&b->work);

	/* If caller isn't waiting for write, parent refcount is cache set */
	closure_lock(&b->io, parent ?: &b->c->cl);

	clear_bit(BTREE_NODE_dirty,	 &b->flags);
	change_bit(BTREE_NODE_write_idx, &b->flags);

	do_btree_node_write(b);

	b->written += set_blocks(i, b->c);
	atomic_long_add(set_blocks(i, b->c) * b->c->sb.block_size,
			&PTR_CACHE(b->c, &b->key, 0)->btree_sectors_written);

	bch_btree_sort_lazy(b);

	if (b->written < btree_blocks(b))
		bch_bset_init_next(b);
}

static void btree_node_write_work(struct work_struct *w)
{
	struct btree *b = container_of(to_delayed_work(w), struct btree, work);

	rw_lock(true, b, b->level);

	if (btree_node_dirty(b))
		bch_btree_node_write(b, NULL);
	rw_unlock(true, b);
}

static void bch_btree_leaf_dirty(struct btree *b, struct btree_op *op)
{
	struct bset *i = b->sets[b->nsets].data;
	struct btree_write *w = btree_current_write(b);

	BUG_ON(!b->written);
	BUG_ON(!i->keys);

	if (!btree_node_dirty(b))
		queue_delayed_work(btree_io_wq, &b->work, 30 * HZ);

	set_btree_node_dirty(b);

	if (op && op->journal) {
		if (w->journal &&
		    journal_pin_cmp(b->c, w, op)) {
			atomic_dec_bug(w->journal);
			w->journal = NULL;
		}

		if (!w->journal) {
			w->journal = op->journal;
			atomic_inc(w->journal);
		}
	}

	/* Force write if set is too big */
	if (set_bytes(i) > PAGE_SIZE - 48 &&
	    !current->bio_list)
		bch_btree_node_write(b, NULL);
}

/*
 * Btree in memory cache - allocation/freeing
 * mca -> memory cache
 */

static void mca_reinit(struct btree *b)
{
	unsigned i;

	b->flags	= 0;
	b->written	= 0;
	b->nsets	= 0;

	for (i = 0; i < MAX_BSETS; i++)
		b->sets[i].size = 0;
	/*
	 * Second loop starts at 1 because b->sets[0]->data is the memory we
	 * allocated
	 */
	for (i = 1; i < MAX_BSETS; i++)
		b->sets[i].data = NULL;
}

#define mca_reserve(c)	(((c->root && c->root->level)		\
			  ? c->root->level : 1) * 8 + 16)
#define mca_can_free(c)						\
	max_t(int, 0, c->bucket_cache_used - mca_reserve(c))

static void mca_data_free(struct btree *b)
{
	struct bset_tree *t = b->sets;
	BUG_ON(!closure_is_unlocked(&b->io.cl));

	if (bset_prev_bytes(b) < PAGE_SIZE)
		kfree(t->prev);
	else
		free_pages((unsigned long) t->prev,
			   get_order(bset_prev_bytes(b)));

	if (bset_tree_bytes(b) < PAGE_SIZE)
		kfree(t->tree);
	else
		free_pages((unsigned long) t->tree,
			   get_order(bset_tree_bytes(b)));

	free_pages((unsigned long) t->data, b->page_order);

	t->prev = NULL;
	t->tree = NULL;
	t->data = NULL;
	list_move(&b->list, &b->c->btree_cache_freed);
	b->c->bucket_cache_used--;
}

static void mca_bucket_free(struct btree *b)
{
	BUG_ON(btree_node_dirty(b));

	b->key.ptr[0] = 0;
	hlist_del_init_rcu(&b->hash);
	list_move(&b->list, &b->c->btree_cache_freeable);
}

static unsigned btree_order(struct bkey *k)
{
	return ilog2(KEY_SIZE(k) / PAGE_SECTORS ?: 1);
}

static void mca_data_alloc(struct btree *b, struct bkey *k, gfp_t gfp)
{
	struct bset_tree *t = b->sets;
	BUG_ON(t->data);

	b->page_order = max_t(unsigned,
			      ilog2(b->c->btree_pages),
			      btree_order(k));

	t->data = (void *) __get_free_pages(gfp, b->page_order);
	if (!t->data)
		goto err;

	t->tree = bset_tree_bytes(b) < PAGE_SIZE
		? kmalloc(bset_tree_bytes(b), gfp)
		: (void *) __get_free_pages(gfp, get_order(bset_tree_bytes(b)));
	if (!t->tree)
		goto err;

	t->prev = bset_prev_bytes(b) < PAGE_SIZE
		? kmalloc(bset_prev_bytes(b), gfp)
		: (void *) __get_free_pages(gfp, get_order(bset_prev_bytes(b)));
	if (!t->prev)
		goto err;

	list_move(&b->list, &b->c->btree_cache);
	b->c->bucket_cache_used++;
	return;
err:
	mca_data_free(b);
}

static struct btree *mca_bucket_alloc(struct cache_set *c,
				      struct bkey *k, gfp_t gfp)
{
	struct btree *b = kzalloc(sizeof(struct btree), gfp);
	if (!b)
		return NULL;

	init_rwsem(&b->lock);
	lockdep_set_novalidate_class(&b->lock);
	INIT_LIST_HEAD(&b->list);
	INIT_DELAYED_WORK(&b->work, btree_node_write_work);
	b->c = c;
	closure_init_unlocked(&b->io);

	mca_data_alloc(b, k, gfp);
	return b;
}

static int mca_reap(struct btree *b, struct closure *cl, unsigned min_order)
{
	lockdep_assert_held(&b->c->bucket_lock);

	if (!down_write_trylock(&b->lock))
		return -ENOMEM;

	if (b->page_order < min_order) {
		rw_unlock(true, b);
		return -ENOMEM;
	}

	BUG_ON(btree_node_dirty(b) && !b->sets[0].data);

	if (cl && btree_node_dirty(b))
		bch_btree_node_write(b, NULL);

	if (cl)
		closure_wait_event_async(&b->io.wait, cl,
			 atomic_read(&b->io.cl.remaining) == -1);

	if (btree_node_dirty(b) ||
	    !closure_is_unlocked(&b->io.cl) ||
	    work_pending(&b->work.work)) {
		rw_unlock(true, b);
		return -EAGAIN;
	}

	return 0;
}

static unsigned long bch_mca_scan(struct shrinker *shrink,
				  struct shrink_control *sc)
{
	struct cache_set *c = container_of(shrink, struct cache_set, shrink);
	struct btree *b, *t;
	unsigned long i, nr = sc->nr_to_scan;
	unsigned long freed = 0;

	if (c->shrinker_disabled)
		return SHRINK_STOP;

	if (c->try_harder)
		return SHRINK_STOP;

	/* Return -1 if we can't do anything right now */
	if (sc->gfp_mask & __GFP_WAIT)
		mutex_lock(&c->bucket_lock);
	else if (!mutex_trylock(&c->bucket_lock))
		return -1;

	/*
	 * It's _really_ critical that we don't free too many btree nodes - we
	 * have to always leave ourselves a reserve. The reserve is how we
	 * guarantee that allocating memory for a new btree node can always
	 * succeed, so that inserting keys into the btree can always succeed and
	 * IO can always make forward progress:
	 */
	nr /= c->btree_pages;
	nr = min_t(unsigned long, nr, mca_can_free(c));

	i = 0;
	list_for_each_entry_safe(b, t, &c->btree_cache_freeable, list) {
		if (freed >= nr)
			break;

		if (++i > 3 &&
		    !mca_reap(b, NULL, 0)) {
			mca_data_free(b);
			rw_unlock(true, b);
			freed++;
		}
	}

	/*
	 * Can happen right when we first start up, before we've read in any
	 * btree nodes
	 */
	if (list_empty(&c->btree_cache))
		goto out;

	for (i = 0; (nr--) && i < c->bucket_cache_used; i++) {
		b = list_first_entry(&c->btree_cache, struct btree, list);
		list_rotate_left(&c->btree_cache);

		if (!b->accessed &&
		    !mca_reap(b, NULL, 0)) {
			mca_bucket_free(b);
			mca_data_free(b);
			rw_unlock(true, b);
			freed++;
		} else
			b->accessed = 0;
	}
out:
	mutex_unlock(&c->bucket_lock);
	return freed;
}

static unsigned long bch_mca_count(struct shrinker *shrink,
				   struct shrink_control *sc)
{
	struct cache_set *c = container_of(shrink, struct cache_set, shrink);

	if (c->shrinker_disabled)
		return 0;

	if (c->try_harder)
		return 0;

	return mca_can_free(c) * c->btree_pages;
}

void bch_btree_cache_free(struct cache_set *c)
{
	struct btree *b;
	struct closure cl;
	closure_init_stack(&cl);

	if (c->shrink.list.next)
		unregister_shrinker(&c->shrink);

	mutex_lock(&c->bucket_lock);

#ifdef CONFIG_BCACHE_DEBUG
	if (c->verify_data)
		list_move(&c->verify_data->list, &c->btree_cache);
#endif

	list_splice(&c->btree_cache_freeable,
		    &c->btree_cache);

	while (!list_empty(&c->btree_cache)) {
		b = list_first_entry(&c->btree_cache, struct btree, list);

		if (btree_node_dirty(b))
			btree_complete_write(b, btree_current_write(b));
		clear_bit(BTREE_NODE_dirty, &b->flags);

		mca_data_free(b);
	}

	while (!list_empty(&c->btree_cache_freed)) {
		b = list_first_entry(&c->btree_cache_freed,
				     struct btree, list);
		list_del(&b->list);
		cancel_delayed_work_sync(&b->work);
		kfree(b);
	}

	mutex_unlock(&c->bucket_lock);
}

int bch_btree_cache_alloc(struct cache_set *c)
{
	unsigned i;

	/* XXX: doesn't check for errors */

	closure_init_unlocked(&c->gc);

	for (i = 0; i < mca_reserve(c); i++)
		mca_bucket_alloc(c, &ZERO_KEY, GFP_KERNEL);

	list_splice_init(&c->btree_cache,
			 &c->btree_cache_freeable);

#ifdef CONFIG_BCACHE_DEBUG
	mutex_init(&c->verify_lock);

	c->verify_data = mca_bucket_alloc(c, &ZERO_KEY, GFP_KERNEL);

	if (c->verify_data &&
	    c->verify_data->sets[0].data)
		list_del_init(&c->verify_data->list);
	else
		c->verify_data = NULL;
#endif

	c->shrink.count_objects = bch_mca_count;
	c->shrink.scan_objects = bch_mca_scan;
	c->shrink.seeks = 4;
	c->shrink.batch = c->btree_pages * 2;
	register_shrinker(&c->shrink);

	return 0;
}

/* Btree in memory cache - hash table */

static struct hlist_head *mca_hash(struct cache_set *c, struct bkey *k)
{
	return &c->bucket_hash[hash_32(PTR_HASH(c, k), BUCKET_HASH_BITS)];
}

static struct btree *mca_find(struct cache_set *c, struct bkey *k)
{
	struct btree *b;

	rcu_read_lock();
	hlist_for_each_entry_rcu(b, mca_hash(c, k), hash)
		if (PTR_HASH(c, &b->key) == PTR_HASH(c, k))
			goto out;
	b = NULL;
out:
	rcu_read_unlock();
	return b;
}

static struct btree *mca_cannibalize(struct cache_set *c, struct bkey *k,
				     int level, struct closure *cl)
{
	int ret = -ENOMEM;
	struct btree *i;

	trace_bcache_btree_cache_cannibalize(c);

	if (!cl)
		return ERR_PTR(-ENOMEM);

	/*
	 * Trying to free up some memory - i.e. reuse some btree nodes - may
	 * require initiating IO to flush the dirty part of the node. If we're
	 * running under generic_make_request(), that IO will never finish and
	 * we would deadlock. Returning -EAGAIN causes the cache lookup code to
	 * punt to workqueue and retry.
	 */
	if (current->bio_list)
		return ERR_PTR(-EAGAIN);

	if (c->try_harder && c->try_harder != cl) {
		closure_wait_event_async(&c->try_wait, cl, !c->try_harder);
		return ERR_PTR(-EAGAIN);
	}

	c->try_harder = cl;
	c->try_harder_start = local_clock();
retry:
	list_for_each_entry_reverse(i, &c->btree_cache, list) {
		int r = mca_reap(i, cl, btree_order(k));
		if (!r)
			return i;
		if (r != -ENOMEM)
			ret = r;
	}

	if (ret == -EAGAIN &&
	    closure_blocking(cl)) {
		mutex_unlock(&c->bucket_lock);
		closure_sync(cl);
		mutex_lock(&c->bucket_lock);
		goto retry;
	}

	return ERR_PTR(ret);
}

/*
 * We can only have one thread cannibalizing other cached btree nodes at a time,
 * or we'll deadlock. We use an open coded mutex to ensure that, which a
 * cannibalize_bucket() will take. This means every time we unlock the root of
 * the btree, we need to release this lock if we have it held.
 */
void bch_cannibalize_unlock(struct cache_set *c, struct closure *cl)
{
	if (c->try_harder == cl) {
		bch_time_stats_update(&c->try_harder_time, c->try_harder_start);
		c->try_harder = NULL;
		__closure_wake_up(&c->try_wait);
	}
}

static struct btree *mca_alloc(struct cache_set *c, struct bkey *k,
			       int level, struct closure *cl)
{
	struct btree *b;

	lockdep_assert_held(&c->bucket_lock);

	if (mca_find(c, k))
		return NULL;

	/* btree_free() doesn't free memory; it sticks the node on the end of
	 * the list. Check if there's any freed nodes there:
	 */
	list_for_each_entry(b, &c->btree_cache_freeable, list)
		if (!mca_reap(b, NULL, btree_order(k)))
			goto out;

	/* We never free struct btree itself, just the memory that holds the on
	 * disk node. Check the freed list before allocating a new one:
	 */
	list_for_each_entry(b, &c->btree_cache_freed, list)
		if (!mca_reap(b, NULL, 0)) {
			mca_data_alloc(b, k, __GFP_NOWARN|GFP_NOIO);
			if (!b->sets[0].data)
				goto err;
			else
				goto out;
		}

	b = mca_bucket_alloc(c, k, __GFP_NOWARN|GFP_NOIO);
	if (!b)
		goto err;

	BUG_ON(!down_write_trylock(&b->lock));
	if (!b->sets->data)
		goto err;
out:
	BUG_ON(!closure_is_unlocked(&b->io.cl));

	bkey_copy(&b->key, k);
	list_move(&b->list, &c->btree_cache);
	hlist_del_init_rcu(&b->hash);
	hlist_add_head_rcu(&b->hash, mca_hash(c, k));

	lock_set_subclass(&b->lock.dep_map, level + 1, _THIS_IP_);
	b->level	= level;

	mca_reinit(b);

	return b;
err:
	if (b)
		rw_unlock(true, b);

	b = mca_cannibalize(c, k, level, cl);
	if (!IS_ERR(b))
		goto out;

	return b;
}

/**
 * bch_btree_node_get - find a btree node in the cache and lock it, reading it
 * in from disk if necessary.
 *
 * If IO is necessary, it uses the closure embedded in struct btree_op to wait;
 * if that closure is in non blocking mode, will return -EAGAIN.
 *
 * The btree node will have either a read or a write lock held, depending on
 * level and op->lock.
 */
struct btree *bch_btree_node_get(struct cache_set *c, struct bkey *k,
				 int level, struct btree_op *op)
{
	int i = 0;
	bool write = level <= op->lock;
	struct btree *b;

	BUG_ON(level < 0);
retry:
	b = mca_find(c, k);

	if (!b) {
		if (current->bio_list)
			return ERR_PTR(-EAGAIN);

		mutex_lock(&c->bucket_lock);
		b = mca_alloc(c, k, level, &op->cl);
		mutex_unlock(&c->bucket_lock);

		if (!b)
			goto retry;
		if (IS_ERR(b))
			return b;

		bch_btree_node_read(b);

		if (!write)
			downgrade_write(&b->lock);
	} else {
		rw_lock(write, b, level);
		if (PTR_HASH(c, &b->key) != PTR_HASH(c, k)) {
			rw_unlock(write, b);
			goto retry;
		}
		BUG_ON(b->level != level);
	}

	b->accessed = 1;

	for (; i <= b->nsets && b->sets[i].size; i++) {
		prefetch(b->sets[i].tree);
		prefetch(b->sets[i].data);
	}

	for (; i <= b->nsets; i++)
		prefetch(b->sets[i].data);

	if (btree_node_io_error(b)) {
		rw_unlock(write, b);
		return ERR_PTR(-EIO);
	}

	BUG_ON(!b->written);

	return b;
}

static void btree_node_prefetch(struct cache_set *c, struct bkey *k, int level)
{
	struct btree *b;

	mutex_lock(&c->bucket_lock);
	b = mca_alloc(c, k, level, NULL);
	mutex_unlock(&c->bucket_lock);

	if (!IS_ERR_OR_NULL(b)) {
		bch_btree_node_read(b);
		rw_unlock(true, b);
	}
}

/* Btree alloc */

static void btree_node_free(struct btree *b, struct btree_op *op)
{
	unsigned i;

	trace_bcache_btree_node_free(b);

	/*
	 * The BUG_ON() in btree_node_get() implies that we must have a write
	 * lock on parent to free or even invalidate a node
	 */
	BUG_ON(op->lock <= b->level);
	BUG_ON(b == b->c->root);

	if (btree_node_dirty(b))
		btree_complete_write(b, btree_current_write(b));
	clear_bit(BTREE_NODE_dirty, &b->flags);

	cancel_delayed_work(&b->work);

	mutex_lock(&b->c->bucket_lock);

	for (i = 0; i < KEY_PTRS(&b->key); i++) {
		BUG_ON(atomic_read(&PTR_BUCKET(b->c, &b->key, i)->pin));

		bch_inc_gen(PTR_CACHE(b->c, &b->key, i),
			    PTR_BUCKET(b->c, &b->key, i));
	}

	bch_bucket_free(b->c, &b->key);
	mca_bucket_free(b);
	mutex_unlock(&b->c->bucket_lock);
}

struct btree *bch_btree_node_alloc(struct cache_set *c, int level,
				   struct closure *cl)
{
	BKEY_PADDED(key) k;
	struct btree *b = ERR_PTR(-EAGAIN);

	mutex_lock(&c->bucket_lock);
retry:
	if (__bch_bucket_alloc_set(c, WATERMARK_METADATA, &k.key, 1, cl))
		goto err;

	SET_KEY_SIZE(&k.key, c->btree_pages * PAGE_SECTORS);

	b = mca_alloc(c, &k.key, level, cl);
	if (IS_ERR(b))
		goto err_free;

	if (!b) {
		cache_bug(c,
			"Tried to allocate bucket that was in btree cache");
		__bkey_put(c, &k.key);
		goto retry;
	}

	b->accessed = 1;
	bch_bset_init_next(b);

	mutex_unlock(&c->bucket_lock);

	trace_bcache_btree_node_alloc(b);
	return b;
err_free:
	bch_bucket_free(c, &k.key);
	__bkey_put(c, &k.key);
err:
	mutex_unlock(&c->bucket_lock);

	trace_bcache_btree_node_alloc_fail(b);
	return b;
}

static struct btree *btree_node_alloc_replacement(struct btree *b,
						  struct closure *cl)
{
	struct btree *n = bch_btree_node_alloc(b->c, b->level, cl);
	if (!IS_ERR_OR_NULL(n))
		bch_btree_sort_into(b, n);

	return n;
}

/* Garbage collection */

uint8_t __bch_btree_mark_key(struct cache_set *c, int level, struct bkey *k)
{
	uint8_t stale = 0;
	unsigned i;
	struct bucket *g;

	/*
	 * ptr_invalid() can't return true for the keys that mark btree nodes as
	 * freed, but since ptr_bad() returns true we'll never actually use them
	 * for anything and thus we don't want mark their pointers here
	 */
	if (!bkey_cmp(k, &ZERO_KEY))
		return stale;

	for (i = 0; i < KEY_PTRS(k); i++) {
		if (!ptr_available(c, k, i))
			continue;

		g = PTR_BUCKET(c, k, i);

		if (gen_after(g->gc_gen, PTR_GEN(k, i)))
			g->gc_gen = PTR_GEN(k, i);

		if (ptr_stale(c, k, i)) {
			stale = max(stale, ptr_stale(c, k, i));
			continue;
		}

		cache_bug_on(GC_MARK(g) &&
			     (GC_MARK(g) == GC_MARK_METADATA) != (level != 0),
			     c, "inconsistent ptrs: mark = %llu, level = %i",
			     GC_MARK(g), level);

		if (level)
			SET_GC_MARK(g, GC_MARK_METADATA);
		else if (KEY_DIRTY(k))
			SET_GC_MARK(g, GC_MARK_DIRTY);

		/* guard against overflow */
		SET_GC_SECTORS_USED(g, min_t(unsigned,
					     GC_SECTORS_USED(g) + KEY_SIZE(k),
					     (1 << 14) - 1));

		BUG_ON(!GC_SECTORS_USED(g));
	}

	return stale;
}

#define btree_mark_key(b, k)	__bch_btree_mark_key(b->c, b->level, k)

static int btree_gc_mark_node(struct btree *b, unsigned *keys,
			      struct gc_stat *gc)
{
	uint8_t stale = 0;
	unsigned last_dev = -1;
	struct bcache_device *d = NULL;
	struct bkey *k;
	struct btree_iter iter;
	struct bset_tree *t;

	gc->nodes++;

	for_each_key_filter(b, k, &iter, bch_ptr_invalid) {
		if (last_dev != KEY_INODE(k)) {
			last_dev = KEY_INODE(k);

			d = KEY_INODE(k) < b->c->nr_uuids
				? b->c->devices[last_dev]
				: NULL;
		}

		stale = max(stale, btree_mark_key(b, k));

		if (bch_ptr_bad(b, k))
			continue;

		*keys += bkey_u64s(k);

		gc->key_bytes += bkey_u64s(k);
		gc->nkeys++;

		gc->data += KEY_SIZE(k);
		if (KEY_DIRTY(k))
			gc->dirty += KEY_SIZE(k);
	}

	for (t = b->sets; t <= &b->sets[b->nsets]; t++)
		btree_bug_on(t->size &&
			     bset_written(b, t) &&
			     bkey_cmp(&b->key, &t->end) < 0,
			     b, "found short btree key in gc");

	return stale;
}

static struct btree *btree_gc_alloc(struct btree *b, struct bkey *k,
				    struct btree_op *op)
{
	/*
	 * We block priorities from being written for the duration of garbage
	 * collection, so we can't sleep in btree_alloc() ->
	 * bch_bucket_alloc_set(), or we'd risk deadlock - so we don't pass it
	 * our closure.
	 */
	struct btree *n = btree_node_alloc_replacement(b, NULL);

	if (!IS_ERR_OR_NULL(n)) {
		swap(b, n);
		__bkey_put(b->c, &b->key);

		memcpy(k->ptr, b->key.ptr,
		       sizeof(uint64_t) * KEY_PTRS(&b->key));

		btree_node_free(n, op);
		up_write(&n->lock);
	}

	return b;
}

/*
 * Leaving this at 2 until we've got incremental garbage collection done; it
 * could be higher (and has been tested with 4) except that garbage collection
 * could take much longer, adversely affecting latency.
 */
#define GC_MERGE_NODES	2U

struct gc_merge_info {
	struct btree	*b;
	struct bkey	*k;
	unsigned	keys;
};

static void btree_gc_coalesce(struct btree *b, struct btree_op *op,
			      struct gc_stat *gc, struct gc_merge_info *r)
{
	unsigned nodes = 0, keys = 0, blocks;
	int i;

	while (nodes < GC_MERGE_NODES && r[nodes].b)
		keys += r[nodes++].keys;

	blocks = btree_default_blocks(b->c) * 2 / 3;

	if (nodes < 2 ||
	    __set_blocks(b->sets[0].data, keys, b->c) > blocks * (nodes - 1))
		return;

	for (i = nodes - 1; i >= 0; --i) {
		if (r[i].b->written)
			r[i].b = btree_gc_alloc(r[i].b, r[i].k, op);

		if (r[i].b->written)
			return;
	}

	for (i = nodes - 1; i > 0; --i) {
		struct bset *n1 = r[i].b->sets->data;
		struct bset *n2 = r[i - 1].b->sets->data;
		struct bkey *k, *last = NULL;

		keys = 0;

		if (i == 1) {
			/*
			 * Last node we're not getting rid of - we're getting
			 * rid of the node at r[0]. Have to try and fit all of
			 * the remaining keys into this node; we can't ensure
			 * they will always fit due to rounding and variable
			 * length keys (shouldn't be possible in practice,
			 * though)
			 */
			if (__set_blocks(n1, n1->keys + r->keys,
					 b->c) > btree_blocks(r[i].b))
				return;

			keys = n2->keys;
			last = &r->b->key;
		} else
			for (k = n2->start;
			     k < end(n2);
			     k = bkey_next(k)) {
				if (__set_blocks(n1, n1->keys + keys +
						 bkey_u64s(k), b->c) > blocks)
					break;

				last = k;
				keys += bkey_u64s(k);
			}

		BUG_ON(__set_blocks(n1, n1->keys + keys,
				    b->c) > btree_blocks(r[i].b));

		if (last) {
			bkey_copy_key(&r[i].b->key, last);
			bkey_copy_key(r[i].k, last);
		}

		memcpy(end(n1),
		       n2->start,
		       (void *) node(n2, keys) - (void *) n2->start);

		n1->keys += keys;

		memmove(n2->start,
			node(n2, keys),
			(void *) end(n2) - (void *) node(n2, keys));

		n2->keys -= keys;

		r[i].keys	= n1->keys;
		r[i - 1].keys	= n2->keys;
	}

	btree_node_free(r->b, op);
	up_write(&r->b->lock);

	trace_bcache_btree_gc_coalesce(nodes);

	gc->nodes--;
	nodes--;

	memmove(&r[0], &r[1], sizeof(struct gc_merge_info) * nodes);
	memset(&r[nodes], 0, sizeof(struct gc_merge_info));
}

static int btree_gc_recurse(struct btree *b, struct btree_op *op,
			    struct closure *writes, struct gc_stat *gc)
{
	void write(struct btree *r)
	{
		if (!r->written)
			bch_btree_node_write(r, &op->cl);
		else if (btree_node_dirty(r))
			bch_btree_node_write(r, writes);

		up_write(&r->lock);
	}

	int ret = 0, stale;
	unsigned i;
	struct gc_merge_info r[GC_MERGE_NODES];

	memset(r, 0, sizeof(r));

	while ((r->k = bch_next_recurse_key(b, &b->c->gc_done))) {
		r->b = bch_btree_node_get(b->c, r->k, b->level - 1, op);

		if (IS_ERR(r->b)) {
			ret = PTR_ERR(r->b);
			break;
		}

		r->keys	= 0;
		stale = btree_gc_mark_node(r->b, &r->keys, gc);

		if (!b->written &&
		    (r->b->level || stale > 10 ||
		     b->c->gc_always_rewrite))
			r->b = btree_gc_alloc(r->b, r->k, op);

		if (r->b->level)
			ret = btree_gc_recurse(r->b, op, writes, gc);

		if (ret) {
			write(r->b);
			break;
		}

		bkey_copy_key(&b->c->gc_done, r->k);

		if (!b->written)
			btree_gc_coalesce(b, op, gc, r);

		if (r[GC_MERGE_NODES - 1].b)
			write(r[GC_MERGE_NODES - 1].b);

		memmove(&r[1], &r[0],
			sizeof(struct gc_merge_info) * (GC_MERGE_NODES - 1));

		/* When we've got incremental GC working, we'll want to do
		 * if (should_resched())
		 *	return -EAGAIN;
		 */
		cond_resched();
#if 0
		if (need_resched()) {
			ret = -EAGAIN;
			break;
		}
#endif
	}

	for (i = 1; i < GC_MERGE_NODES && r[i].b; i++)
		write(r[i].b);

	/* Might have freed some children, must remove their keys */
	if (!b->written)
		bch_btree_sort(b);

	return ret;
}

static int bch_btree_gc_root(struct btree *b, struct btree_op *op,
			     struct closure *writes, struct gc_stat *gc)
{
	struct btree *n = NULL;
	unsigned keys = 0;
	int ret = 0, stale = btree_gc_mark_node(b, &keys, gc);

	if (b->level || stale > 10)
		n = btree_node_alloc_replacement(b, NULL);

	if (!IS_ERR_OR_NULL(n))
		swap(b, n);

	if (b->level)
		ret = btree_gc_recurse(b, op, writes, gc);

	if (!b->written || btree_node_dirty(b)) {
		bch_btree_node_write(b, n ? &op->cl : NULL);
	}

	if (!IS_ERR_OR_NULL(n)) {
		closure_sync(&op->cl);
		bch_btree_set_root(b);
		btree_node_free(n, op);
		rw_unlock(true, b);
	}

	return ret;
}

static void btree_gc_start(struct cache_set *c)
{
	struct cache *ca;
	struct bucket *b;
	unsigned i;

	if (!c->gc_mark_valid)
		return;

	mutex_lock(&c->bucket_lock);

	c->gc_mark_valid = 0;
	c->gc_done = ZERO_KEY;

	for_each_cache(ca, c, i)
		for_each_bucket(b, ca) {
			b->gc_gen = b->gen;
			if (!atomic_read(&b->pin)) {
				SET_GC_MARK(b, GC_MARK_RECLAIMABLE);
				SET_GC_SECTORS_USED(b, 0);
			}
		}

	mutex_unlock(&c->bucket_lock);
}

size_t bch_btree_gc_finish(struct cache_set *c)
{
	size_t available = 0;
	struct bucket *b;
	struct cache *ca;
	unsigned i;

	mutex_lock(&c->bucket_lock);

	set_gc_sectors(c);
	c->gc_mark_valid = 1;
	c->need_gc	= 0;

	if (c->root)
		for (i = 0; i < KEY_PTRS(&c->root->key); i++)
			SET_GC_MARK(PTR_BUCKET(c, &c->root->key, i),
				    GC_MARK_METADATA);

	for (i = 0; i < KEY_PTRS(&c->uuid_bucket); i++)
		SET_GC_MARK(PTR_BUCKET(c, &c->uuid_bucket, i),
			    GC_MARK_METADATA);

	for_each_cache(ca, c, i) {
		uint64_t *i;

		ca->invalidate_needs_gc = 0;

		for (i = ca->sb.d; i < ca->sb.d + ca->sb.keys; i++)
			SET_GC_MARK(ca->buckets + *i, GC_MARK_METADATA);

		for (i = ca->prio_buckets;
		     i < ca->prio_buckets + prio_buckets(ca) * 2; i++)
			SET_GC_MARK(ca->buckets + *i, GC_MARK_METADATA);

		for_each_bucket(b, ca) {
			b->last_gc	= b->gc_gen;
			c->need_gc	= max(c->need_gc, bucket_gc_gen(b));

			if (!atomic_read(&b->pin) &&
			    GC_MARK(b) == GC_MARK_RECLAIMABLE) {
				available++;
				if (!GC_SECTORS_USED(b))
					bch_bucket_add_unused(ca, b);
			}
		}
	}

	mutex_unlock(&c->bucket_lock);
	return available;
}

static void bch_btree_gc(struct closure *cl)
{
	struct cache_set *c = container_of(cl, struct cache_set, gc.cl);
	int ret;
	unsigned long available;
	struct gc_stat stats;
	struct closure writes;
	struct btree_op op;
	uint64_t start_time = local_clock();

	trace_bcache_gc_start(c);

	memset(&stats, 0, sizeof(struct gc_stat));
	closure_init_stack(&writes);
	bch_btree_op_init_stack(&op);
	op.lock = SHRT_MAX;

	btree_gc_start(c);

	atomic_inc(&c->prio_blocked);

	ret = btree_root(gc_root, c, &op, &writes, &stats);
	closure_sync(&op.cl);
	closure_sync(&writes);

	if (ret) {
		pr_warn("gc failed!");
		continue_at(cl, bch_btree_gc, bch_gc_wq);
	}

	/* Possibly wait for new UUIDs or whatever to hit disk */
	bch_journal_meta(c, &op.cl);
	closure_sync(&op.cl);

	available = bch_btree_gc_finish(c);

	atomic_dec(&c->prio_blocked);
	wake_up_allocators(c);

	bch_time_stats_update(&c->btree_gc_time, start_time);

	stats.key_bytes *= sizeof(uint64_t);
	stats.dirty	<<= 9;
	stats.data	<<= 9;
	stats.in_use	= (c->nbuckets - available) * 100 / c->nbuckets;
	memcpy(&c->gc_stats, &stats, sizeof(struct gc_stat));

	trace_bcache_gc_end(c);

	continue_at(cl, bch_moving_gc, bch_gc_wq);
}

void bch_queue_gc(struct cache_set *c)
{
	closure_trylock_call(&c->gc.cl, bch_btree_gc, bch_gc_wq, &c->cl);
}

/* Initial partial gc */

static int bch_btree_check_recurse(struct btree *b, struct btree_op *op,
				   unsigned long **seen)
{
	int ret;
	unsigned i;
	struct bkey *k;
	struct bucket *g;
	struct btree_iter iter;

	for_each_key_filter(b, k, &iter, bch_ptr_invalid) {
		for (i = 0; i < KEY_PTRS(k); i++) {
			if (!ptr_available(b->c, k, i))
				continue;

			g = PTR_BUCKET(b->c, k, i);

			if (!__test_and_set_bit(PTR_BUCKET_NR(b->c, k, i),
						seen[PTR_DEV(k, i)]) ||
			    !ptr_stale(b->c, k, i)) {
				g->gen = PTR_GEN(k, i);

				if (b->level)
					g->prio = BTREE_PRIO;
				else if (g->prio == BTREE_PRIO)
					g->prio = INITIAL_PRIO;
			}
		}

		btree_mark_key(b, k);
	}

	if (b->level) {
		k = bch_next_recurse_key(b, &ZERO_KEY);

		while (k) {
			struct bkey *p = bch_next_recurse_key(b, k);
			if (p)
				btree_node_prefetch(b->c, p, b->level - 1);

			ret = btree(check_recurse, k, b, op, seen);
			if (ret)
				return ret;

			k = p;
		}
	}

	return 0;
}

int bch_btree_check(struct cache_set *c, struct btree_op *op)
{
	int ret = -ENOMEM;
	unsigned i;
	unsigned long *seen[MAX_CACHES_PER_SET];

	memset(seen, 0, sizeof(seen));

	for (i = 0; c->cache[i]; i++) {
		size_t n = DIV_ROUND_UP(c->cache[i]->sb.nbuckets, 8);
		seen[i] = kmalloc(n, GFP_KERNEL);
		if (!seen[i])
			goto err;

		/* Disables the seen array until prio_read() uses it too */
		memset(seen[i], 0xFF, n);
	}

	ret = btree_root(check_recurse, c, op, seen);
err:
	for (i = 0; i < MAX_CACHES_PER_SET; i++)
		kfree(seen[i]);
	return ret;
}

/* Btree insertion */

static void shift_keys(struct btree *b, struct bkey *where, struct bkey *insert)
{
	struct bset *i = b->sets[b->nsets].data;

	memmove((uint64_t *) where + bkey_u64s(insert),
		where,
		(void *) end(i) - (void *) where);

	i->keys += bkey_u64s(insert);
	bkey_copy(where, insert);
	bch_bset_fix_lookup_table(b, where);
}

static bool fix_overlapping_extents(struct btree *b,
				    struct bkey *insert,
				    struct btree_iter *iter,
				    struct btree_op *op)
{
	void subtract_dirty(struct bkey *k, uint64_t offset, int sectors)
	{
		if (KEY_DIRTY(k))
			bcache_dev_sectors_dirty_add(b->c, KEY_INODE(k),
						     offset, -sectors);
	}

	uint64_t old_offset;
	unsigned old_size, sectors_found = 0;

	while (1) {
		struct bkey *k = bch_btree_iter_next(iter);
		if (!k ||
		    bkey_cmp(&START_KEY(k), insert) >= 0)
			break;

		if (bkey_cmp(k, &START_KEY(insert)) <= 0)
			continue;

		old_offset = KEY_START(k);
		old_size = KEY_SIZE(k);

		/*
		 * We might overlap with 0 size extents; we can't skip these
		 * because if they're in the set we're inserting to we have to
		 * adjust them so they don't overlap with the key we're
		 * inserting. But we don't want to check them for BTREE_REPLACE
		 * operations.
		 */

		if (op->type == BTREE_REPLACE &&
		    KEY_SIZE(k)) {
			/*
			 * k might have been split since we inserted/found the
			 * key we're replacing
			 */
			unsigned i;
			uint64_t offset = KEY_START(k) -
				KEY_START(&op->replace);

			/* But it must be a subset of the replace key */
			if (KEY_START(k) < KEY_START(&op->replace) ||
			    KEY_OFFSET(k) > KEY_OFFSET(&op->replace))
				goto check_failed;

			/* We didn't find a key that we were supposed to */
			if (KEY_START(k) > KEY_START(insert) + sectors_found)
				goto check_failed;

			if (KEY_PTRS(&op->replace) != KEY_PTRS(k))
				goto check_failed;

			/* skip past gen */
			offset <<= 8;

			BUG_ON(!KEY_PTRS(&op->replace));

			for (i = 0; i < KEY_PTRS(&op->replace); i++)
				if (k->ptr[i] != op->replace.ptr[i] + offset)
					goto check_failed;

			sectors_found = KEY_OFFSET(k) - KEY_START(insert);
		}

		if (bkey_cmp(insert, k) < 0 &&
		    bkey_cmp(&START_KEY(insert), &START_KEY(k)) > 0) {
			/*
			 * We overlapped in the middle of an existing key: that
			 * means we have to split the old key. But we have to do
			 * slightly different things depending on whether the
			 * old key has been written out yet.
			 */

			struct bkey *top;

			subtract_dirty(k, KEY_START(insert), KEY_SIZE(insert));

			if (bkey_written(b, k)) {
				/*
				 * We insert a new key to cover the top of the
				 * old key, and the old key is modified in place
				 * to represent the bottom split.
				 *
				 * It's completely arbitrary whether the new key
				 * is the top or the bottom, but it has to match
				 * up with what btree_sort_fixup() does - it
				 * doesn't check for this kind of overlap, it
				 * depends on us inserting a new key for the top
				 * here.
				 */
				top = bch_bset_search(b, &b->sets[b->nsets],
						      insert);
				shift_keys(b, top, k);
			} else {
				BKEY_PADDED(key) temp;
				bkey_copy(&temp.key, k);
				shift_keys(b, k, &temp.key);
				top = bkey_next(k);
			}

			bch_cut_front(insert, top);
			bch_cut_back(&START_KEY(insert), k);
			bch_bset_fix_invalidated_key(b, k);
			return false;
		}

		if (bkey_cmp(insert, k) < 0) {
			bch_cut_front(insert, k);
		} else {
			if (bkey_written(b, k) &&
			    bkey_cmp(&START_KEY(insert), &START_KEY(k)) <= 0) {
				/*
				 * Completely overwrote, so we don't have to
				 * invalidate the binary search tree
				 */
				bch_cut_front(k, k);
			} else {
				__bch_cut_back(&START_KEY(insert), k);
				bch_bset_fix_invalidated_key(b, k);
			}
		}

		subtract_dirty(k, old_offset, old_size - KEY_SIZE(k));
	}

check_failed:
	if (op->type == BTREE_REPLACE) {
		if (!sectors_found) {
			op->insert_collision = true;
			return true;
		} else if (sectors_found < KEY_SIZE(insert)) {
			SET_KEY_OFFSET(insert, KEY_OFFSET(insert) -
				       (KEY_SIZE(insert) - sectors_found));
			SET_KEY_SIZE(insert, sectors_found);
		}
	}

	return false;
}

static bool btree_insert_key(struct btree *b, struct btree_op *op,
			     struct bkey *k)
{
	struct bset *i = b->sets[b->nsets].data;
	struct bkey *m, *prev;
	unsigned status = BTREE_INSERT_STATUS_INSERT;

	BUG_ON(bkey_cmp(k, &b->key) > 0);
	BUG_ON(b->level && !KEY_PTRS(k));
	BUG_ON(!b->level && !KEY_OFFSET(k));

	if (!b->level) {
		struct btree_iter iter;
		struct bkey search = KEY(KEY_INODE(k), KEY_START(k), 0);

		/*
		 * bset_search() returns the first key that is strictly greater
		 * than the search key - but for back merging, we want to find
		 * the first key that is greater than or equal to KEY_START(k) -
		 * unless KEY_START(k) is 0.
		 */
		if (KEY_OFFSET(&search))
			SET_KEY_OFFSET(&search, KEY_OFFSET(&search) - 1);

		prev = NULL;
		m = bch_btree_iter_init(b, &iter, &search);

		if (fix_overlapping_extents(b, k, &iter, op))
			return false;

		while (m != end(i) &&
		       bkey_cmp(k, &START_KEY(m)) > 0)
			prev = m, m = bkey_next(m);

		if (key_merging_disabled(b->c))
			goto insert;

		/* prev is in the tree, if we merge we're done */
		status = BTREE_INSERT_STATUS_BACK_MERGE;
		if (prev &&
		    bch_bkey_try_merge(b, prev, k))
			goto merged;

		status = BTREE_INSERT_STATUS_OVERWROTE;
		if (m != end(i) &&
		    KEY_PTRS(m) == KEY_PTRS(k) && !KEY_SIZE(m))
			goto copy;

		status = BTREE_INSERT_STATUS_FRONT_MERGE;
		if (m != end(i) &&
		    bch_bkey_try_merge(b, k, m))
			goto copy;
	} else
		m = bch_bset_search(b, &b->sets[b->nsets], k);

insert:	shift_keys(b, m, k);
copy:	bkey_copy(m, k);
merged:
	if (KEY_DIRTY(k))
		bcache_dev_sectors_dirty_add(b->c, KEY_INODE(k),
					     KEY_START(k), KEY_SIZE(k));

	bch_check_keys(b, "%u for %s", status, op_type(op));

	if (b->level && !KEY_OFFSET(k))
		btree_current_write(b)->prio_blocked++;

	trace_bcache_btree_insert_key(b, k, op->type, status);

	return true;
}

static bool bch_btree_insert_keys(struct btree *b, struct btree_op *op)
{
	bool ret = false;
	struct bkey *k;
	unsigned oldsize = bch_count_data(b);

	while ((k = bch_keylist_pop(&op->keys))) {
		bkey_put(b->c, k, b->level);
		ret |= btree_insert_key(b, op, k);
	}

	BUG_ON(bch_count_data(b) < oldsize);
	return ret;
}

bool bch_btree_insert_check_key(struct btree *b, struct btree_op *op,
				   struct bio *bio)
{
	bool ret = false;
	uint64_t btree_ptr = b->key.ptr[0];
	unsigned long seq = b->seq;
	BKEY_PADDED(k) tmp;

	rw_unlock(false, b);
	rw_lock(true, b, b->level);

	if (b->key.ptr[0] != btree_ptr ||
	    b->seq != seq + 1 ||
	    should_split(b))
		goto out;

	op->replace = KEY(op->inode, bio_end_sector(bio), bio_sectors(bio));

	SET_KEY_PTRS(&op->replace, 1);
	get_random_bytes(&op->replace.ptr[0], sizeof(uint64_t));

	SET_PTR_DEV(&op->replace, 0, PTR_CHECK_DEV);

	bkey_copy(&tmp.k, &op->replace);

	BUG_ON(op->type != BTREE_INSERT);
	BUG_ON(!btree_insert_key(b, op, &tmp.k));
	ret = true;
out:
	downgrade_write(&b->lock);
	return ret;
}

static int btree_split(struct btree *b, struct btree_op *op)
{
	bool split, root = b == b->c->root;
	struct btree *n1, *n2 = NULL, *n3 = NULL;
	uint64_t start_time = local_clock();

	if (b->level)
		set_closure_blocking(&op->cl);

	n1 = btree_node_alloc_replacement(b, &op->cl);
	if (IS_ERR(n1))
		goto err;

	split = set_blocks(n1->sets[0].data, n1->c) > (btree_blocks(b) * 4) / 5;

	if (split) {
		unsigned keys = 0;

		trace_bcache_btree_node_split(b, n1->sets[0].data->keys);

		n2 = bch_btree_node_alloc(b->c, b->level, &op->cl);
		if (IS_ERR(n2))
			goto err_free1;

		if (root) {
			n3 = bch_btree_node_alloc(b->c, b->level + 1, &op->cl);
			if (IS_ERR(n3))
				goto err_free2;
		}

		bch_btree_insert_keys(n1, op);

		/* Has to be a linear search because we don't have an auxiliary
		 * search tree yet
		 */

		while (keys < (n1->sets[0].data->keys * 3) / 5)
			keys += bkey_u64s(node(n1->sets[0].data, keys));

		bkey_copy_key(&n1->key, node(n1->sets[0].data, keys));
		keys += bkey_u64s(node(n1->sets[0].data, keys));

		n2->sets[0].data->keys = n1->sets[0].data->keys - keys;
		n1->sets[0].data->keys = keys;

		memcpy(n2->sets[0].data->start,
		       end(n1->sets[0].data),
		       n2->sets[0].data->keys * sizeof(uint64_t));

		bkey_copy_key(&n2->key, &b->key);

		bch_keylist_add(&op->keys, &n2->key);
		bch_btree_node_write(n2, &op->cl);
		rw_unlock(true, n2);
	} else {
		trace_bcache_btree_node_compact(b, n1->sets[0].data->keys);

		bch_btree_insert_keys(n1, op);
	}

	bch_keylist_add(&op->keys, &n1->key);
	bch_btree_node_write(n1, &op->cl);

	if (n3) {
		bkey_copy_key(&n3->key, &MAX_KEY);
		bch_btree_insert_keys(n3, op);
		bch_btree_node_write(n3, &op->cl);

		closure_sync(&op->cl);
		bch_btree_set_root(n3);
		rw_unlock(true, n3);
	} else if (root) {
		op->keys.top = op->keys.bottom;
		closure_sync(&op->cl);
		bch_btree_set_root(n1);
	} else {
		unsigned i;

		bkey_copy(op->keys.top, &b->key);
		bkey_copy_key(op->keys.top, &ZERO_KEY);

		for (i = 0; i < KEY_PTRS(&b->key); i++) {
			uint8_t g = PTR_BUCKET(b->c, &b->key, i)->gen + 1;

			SET_PTR_GEN(op->keys.top, i, g);
		}

		bch_keylist_push(&op->keys);
		closure_sync(&op->cl);
		atomic_inc(&b->c->prio_blocked);
	}

	rw_unlock(true, n1);
	btree_node_free(b, op);

	bch_time_stats_update(&b->c->btree_split_time, start_time);

	return 0;
err_free2:
	__bkey_put(n2->c, &n2->key);
	btree_node_free(n2, op);
	rw_unlock(true, n2);
err_free1:
	__bkey_put(n1->c, &n1->key);
	btree_node_free(n1, op);
	rw_unlock(true, n1);
err:
	if (n3 == ERR_PTR(-EAGAIN) ||
	    n2 == ERR_PTR(-EAGAIN) ||
	    n1 == ERR_PTR(-EAGAIN))
		return -EAGAIN;

	pr_warn("couldn't split");
	return -ENOMEM;
}

static int bch_btree_insert_recurse(struct btree *b, struct btree_op *op,
				    struct keylist *stack_keys)
{
	if (b->level) {
		int ret;
		struct bkey *insert = op->keys.bottom;
		struct bkey *k = bch_next_recurse_key(b, &START_KEY(insert));

		if (!k) {
			btree_bug(b, "no key to recurse on at level %i/%i",
				  b->level, b->c->root->level);

			op->keys.top = op->keys.bottom;
			return -EIO;
		}

		if (bkey_cmp(insert, k) > 0) {
			unsigned i;

			if (op->type == BTREE_REPLACE) {
				__bkey_put(b->c, insert);
				op->keys.top = op->keys.bottom;
				op->insert_collision = true;
				return 0;
			}

			for (i = 0; i < KEY_PTRS(insert); i++)
				atomic_inc(&PTR_BUCKET(b->c, insert, i)->pin);

			bkey_copy(stack_keys->top, insert);

			bch_cut_back(k, insert);
			bch_cut_front(k, stack_keys->top);

			bch_keylist_push(stack_keys);
		}

		ret = btree(insert_recurse, k, b, op, stack_keys);
		if (ret)
			return ret;
	}

	if (!bch_keylist_empty(&op->keys)) {
		if (should_split(b)) {
			if (op->lock <= b->c->root->level) {
				BUG_ON(b->level);
				op->lock = b->c->root->level + 1;
				return -EINTR;
			}
			return btree_split(b, op);
		}

		BUG_ON(write_block(b) != b->sets[b->nsets].data);

		if (bch_btree_insert_keys(b, op)) {
			if (!b->level)
				bch_btree_leaf_dirty(b, op);
			else
				bch_btree_node_write(b, &op->cl);
		}
	}

	return 0;
}

int bch_btree_insert(struct btree_op *op, struct cache_set *c)
{
	int ret = 0;
	struct keylist stack_keys;

	/*
	 * Don't want to block with the btree locked unless we have to,
	 * otherwise we get deadlocks with try_harder and between split/gc
	 */
	clear_closure_blocking(&op->cl);

	BUG_ON(bch_keylist_empty(&op->keys));
	bch_keylist_copy(&stack_keys, &op->keys);
	bch_keylist_init(&op->keys);

	while (!bch_keylist_empty(&stack_keys) ||
	       !bch_keylist_empty(&op->keys)) {
		if (bch_keylist_empty(&op->keys)) {
			bch_keylist_add(&op->keys,
					bch_keylist_pop(&stack_keys));
			op->lock = 0;
		}

		ret = btree_root(insert_recurse, c, op, &stack_keys);

		if (ret == -EAGAIN) {
			ret = 0;
			closure_sync(&op->cl);
		} else if (ret) {
			struct bkey *k;

			pr_err("error %i trying to insert key for %s",
			       ret, op_type(op));

			while ((k = bch_keylist_pop(&stack_keys) ?:
				    bch_keylist_pop(&op->keys)))
				bkey_put(c, k, 0);
		}
	}

	bch_keylist_free(&stack_keys);

	if (op->journal)
		atomic_dec_bug(op->journal);
	op->journal = NULL;
	return ret;
}

void bch_btree_set_root(struct btree *b)
{
	unsigned i;
	struct closure cl;

	closure_init_stack(&cl);

	trace_bcache_btree_set_root(b);

	BUG_ON(!b->written);

	for (i = 0; i < KEY_PTRS(&b->key); i++)
		BUG_ON(PTR_BUCKET(b->c, &b->key, i)->prio != BTREE_PRIO);

	mutex_lock(&b->c->bucket_lock);
	list_del_init(&b->list);
	mutex_unlock(&b->c->bucket_lock);

	b->c->root = b;
	__bkey_put(b->c, &b->key);

	bch_journal_meta(b->c, &cl);
	closure_sync(&cl);
}

/* Cache lookup */

static int submit_partial_cache_miss(struct btree *b, struct btree_op *op,
				     struct bkey *k)
{
	struct search *s = container_of(op, struct search, op);
	struct bio *bio = &s->bio.bio;
	int ret = 0;

	while (!ret &&
	       !op->lookup_done) {
		unsigned sectors = INT_MAX;

		if (KEY_INODE(k) == op->inode) {
			if (KEY_START(k) <= bio->bi_sector)
				break;

			sectors = min_t(uint64_t, sectors,
					KEY_START(k) - bio->bi_sector);
		}

		ret = s->d->cache_miss(b, s, bio, sectors);
	}

	return ret;
}

/*
 * Read from a single key, handling the initial cache miss if the key starts in
 * the middle of the bio
 */
static int submit_partial_cache_hit(struct btree *b, struct btree_op *op,
				    struct bkey *k)
{
	struct search *s = container_of(op, struct search, op);
	struct bio *bio = &s->bio.bio;
	unsigned ptr;
	struct bio *n;

	int ret = submit_partial_cache_miss(b, op, k);
	if (ret || op->lookup_done)
		return ret;

	/* XXX: figure out best pointer - for multiple cache devices */
	ptr = 0;

	PTR_BUCKET(b->c, k, ptr)->prio = INITIAL_PRIO;

	while (!op->lookup_done &&
	       KEY_INODE(k) == op->inode &&
	       bio->bi_sector < KEY_OFFSET(k)) {
		struct bkey *bio_key;
		sector_t sector = PTR_OFFSET(k, ptr) +
			(bio->bi_sector - KEY_START(k));
		unsigned sectors = min_t(uint64_t, INT_MAX,
					 KEY_OFFSET(k) - bio->bi_sector);

		n = bch_bio_split(bio, sectors, GFP_NOIO, s->d->bio_split);
		if (n == bio)
			op->lookup_done = true;

		bio_key = &container_of(n, struct bbio, bio)->key;

		/*
		 * The bucket we're reading from might be reused while our bio
		 * is in flight, and we could then end up reading the wrong
		 * data.
		 *
		 * We guard against this by checking (in cache_read_endio()) if
		 * the pointer is stale again; if so, we treat it as an error
		 * and reread from the backing device (but we don't pass that
		 * error up anywhere).
		 */

		bch_bkey_copy_single_ptr(bio_key, k, ptr);
		SET_PTR_OFFSET(bio_key, 0, sector);

		n->bi_end_io	= bch_cache_read_endio;
		n->bi_private	= &s->cl;

		__bch_submit_bbio(n, b->c);
	}

	return 0;
}

int bch_btree_search_recurse(struct btree *b, struct btree_op *op)
{
	struct search *s = container_of(op, struct search, op);
	struct bio *bio = &s->bio.bio;

	int ret = 0;
	struct bkey *k;
	struct btree_iter iter;
	bch_btree_iter_init(b, &iter, &KEY(op->inode, bio->bi_sector, 0));

	do {
		k = bch_btree_iter_next_filter(&iter, b, bch_ptr_bad);
		if (!k) {
			/*
			 * b->key would be exactly what we want, except that
			 * pointers to btree nodes have nonzero size - we
			 * wouldn't go far enough
			 */

			ret = submit_partial_cache_miss(b, op,
					&KEY(KEY_INODE(&b->key),
					     KEY_OFFSET(&b->key), 0));
			break;
		}

		ret = b->level
			? btree(search_recurse, k, b, op)
			: submit_partial_cache_hit(b, op, k);
	} while (!ret &&
		 !op->lookup_done);

	return ret;
}

/* Keybuf code */

static inline int keybuf_cmp(struct keybuf_key *l, struct keybuf_key *r)
{
	/* Overlapping keys compare equal */
	if (bkey_cmp(&l->key, &START_KEY(&r->key)) <= 0)
		return -1;
	if (bkey_cmp(&START_KEY(&l->key), &r->key) >= 0)
		return 1;
	return 0;
}

static inline int keybuf_nonoverlapping_cmp(struct keybuf_key *l,
					    struct keybuf_key *r)
{
	return clamp_t(int64_t, bkey_cmp(&l->key, &r->key), -1, 1);
}

static int bch_btree_refill_keybuf(struct btree *b, struct btree_op *op,
				   struct keybuf *buf, struct bkey *end,
				   keybuf_pred_fn *pred)
{
	struct btree_iter iter;
	bch_btree_iter_init(b, &iter, &buf->last_scanned);

	while (!array_freelist_empty(&buf->freelist)) {
		struct bkey *k = bch_btree_iter_next_filter(&iter, b,
							    bch_ptr_bad);

		if (!b->level) {
			if (!k) {
				buf->last_scanned = b->key;
				break;
			}

			buf->last_scanned = *k;
			if (bkey_cmp(&buf->last_scanned, end) >= 0)
				break;

			if (pred(buf, k)) {
				struct keybuf_key *w;

				spin_lock(&buf->lock);

				w = array_alloc(&buf->freelist);

				w->private = NULL;
				bkey_copy(&w->key, k);

				if (RB_INSERT(&buf->keys, w, node, keybuf_cmp))
					array_free(&buf->freelist, w);

				spin_unlock(&buf->lock);
			}
		} else {
			if (!k)
				break;

			btree(refill_keybuf, k, b, op, buf, end, pred);
			/*
			 * Might get an error here, but can't really do anything
			 * and it'll get logged elsewhere. Just read what we
			 * can.
			 */

			if (bkey_cmp(&buf->last_scanned, end) >= 0)
				break;

			cond_resched();
		}
	}

	return 0;
}

void bch_refill_keybuf(struct cache_set *c, struct keybuf *buf,
		       struct bkey *end, keybuf_pred_fn *pred)
{
	struct bkey start = buf->last_scanned;
	struct btree_op op;
	bch_btree_op_init_stack(&op);

	cond_resched();

	btree_root(refill_keybuf, c, &op, buf, end, pred);
	closure_sync(&op.cl);

	pr_debug("found %s keys from %llu:%llu to %llu:%llu",
		 RB_EMPTY_ROOT(&buf->keys) ? "no" :
		 array_freelist_empty(&buf->freelist) ? "some" : "a few",
		 KEY_INODE(&start), KEY_OFFSET(&start),
		 KEY_INODE(&buf->last_scanned), KEY_OFFSET(&buf->last_scanned));

	spin_lock(&buf->lock);

	if (!RB_EMPTY_ROOT(&buf->keys)) {
		struct keybuf_key *w;
		w = RB_FIRST(&buf->keys, struct keybuf_key, node);
		buf->start	= START_KEY(&w->key);

		w = RB_LAST(&buf->keys, struct keybuf_key, node);
		buf->end	= w->key;
	} else {
		buf->start	= MAX_KEY;
		buf->end	= MAX_KEY;
	}

	spin_unlock(&buf->lock);
}

static void __bch_keybuf_del(struct keybuf *buf, struct keybuf_key *w)
{
	rb_erase(&w->node, &buf->keys);
	array_free(&buf->freelist, w);
}

void bch_keybuf_del(struct keybuf *buf, struct keybuf_key *w)
{
	spin_lock(&buf->lock);
	__bch_keybuf_del(buf, w);
	spin_unlock(&buf->lock);
}

bool bch_keybuf_check_overlapping(struct keybuf *buf, struct bkey *start,
				  struct bkey *end)
{
	bool ret = false;
	struct keybuf_key *p, *w, s;
	s.key = *start;

	if (bkey_cmp(end, &buf->start) <= 0 ||
	    bkey_cmp(start, &buf->end) >= 0)
		return false;

	spin_lock(&buf->lock);
	w = RB_GREATER(&buf->keys, s, node, keybuf_nonoverlapping_cmp);

	while (w && bkey_cmp(&START_KEY(&w->key), end) < 0) {
		p = w;
		w = RB_NEXT(w, node);

		if (p->private)
			ret = true;
		else
			__bch_keybuf_del(buf, p);
	}

	spin_unlock(&buf->lock);
	return ret;
}

struct keybuf_key *bch_keybuf_next(struct keybuf *buf)
{
	struct keybuf_key *w;
	spin_lock(&buf->lock);

	w = RB_FIRST(&buf->keys, struct keybuf_key, node);

	while (w && w->private)
		w = RB_NEXT(w, node);

	if (w)
		w->private = ERR_PTR(-EINTR);

	spin_unlock(&buf->lock);
	return w;
}

struct keybuf_key *bch_keybuf_next_rescan(struct cache_set *c,
					     struct keybuf *buf,
					     struct bkey *end,
					     keybuf_pred_fn *pred)
{
	struct keybuf_key *ret;

	while (1) {
		ret = bch_keybuf_next(buf);
		if (ret)
			break;

		if (bkey_cmp(&buf->last_scanned, end) >= 0) {
			pr_debug("scan finished");
			break;
		}

		bch_refill_keybuf(c, buf, end, pred);
	}

	return ret;
}

void bch_keybuf_init(struct keybuf *buf)
{
	buf->last_scanned	= MAX_KEY;
	buf->keys		= RB_ROOT;

	spin_lock_init(&buf->lock);
	array_allocator_init(&buf->freelist);
}

void bch_btree_exit(void)
{
	if (btree_io_wq)
		destroy_workqueue(btree_io_wq);
	if (bch_gc_wq)
		destroy_workqueue(bch_gc_wq);
}

int __init bch_btree_init(void)
{
	if (!(bch_gc_wq = create_singlethread_workqueue("bch_btree_gc")) ||
	    !(btree_io_wq = create_singlethread_workqueue("bch_btree_io")))
		return -ENOMEM;

	return 0;
}