summaryrefslogtreecommitdiff
path: root/drivers/block/nbd.c
blob: 08696f5f00bb293c087a7725fd96113ef9ca105c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
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
/*
 * Network block device - make block devices work over TCP
 *
 * Note that you can not swap over this thing, yet. Seems to work but
 * deadlocks sometimes - you can not swap over TCP in general.
 * 
 * Copyright 1997-2000, 2008 Pavel Machek <pavel@ucw.cz>
 * Parts copyright 2001 Steven Whitehouse <steve@chygwyn.com>
 *
 * This file is released under GPLv2 or later.
 *
 * (part of code stolen from loop.c)
 */

#include <linux/major.h>

#include <linux/blkdev.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/sched/mm.h>
#include <linux/fs.h>
#include <linux/bio.h>
#include <linux/stat.h>
#include <linux/errno.h>
#include <linux/file.h>
#include <linux/ioctl.h>
#include <linux/mutex.h>
#include <linux/compiler.h>
#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <linux/net.h>
#include <linux/kthread.h>
#include <linux/types.h>
#include <linux/debugfs.h>
#include <linux/blk-mq.h>

#include <linux/uaccess.h>
#include <asm/types.h>

#include <linux/nbd.h>
#include <linux/nbd-netlink.h>
#include <net/genetlink.h>

static DEFINE_IDR(nbd_index_idr);
static DEFINE_MUTEX(nbd_index_mutex);
static int nbd_total_devices = 0;

struct nbd_sock {
	struct socket *sock;
	struct mutex tx_lock;
	struct request *pending;
	int sent;
	bool dead;
	int fallback_index;
	int cookie;
};

struct recv_thread_args {
	struct work_struct work;
	struct nbd_device *nbd;
	int index;
};

struct link_dead_args {
	struct work_struct work;
	int index;
};

#define NBD_TIMEDOUT			0
#define NBD_DISCONNECT_REQUESTED	1
#define NBD_DISCONNECTED		2
#define NBD_HAS_PID_FILE		3
#define NBD_HAS_CONFIG_REF		4
#define NBD_BOUND			5
#define NBD_DESTROY_ON_DISCONNECT	6
#define NBD_DISCONNECT_ON_CLOSE 	7

struct nbd_config {
	u32 flags;
	unsigned long runtime_flags;
	u64 dead_conn_timeout;

	struct nbd_sock **socks;
	int num_connections;
	atomic_t live_connections;
	wait_queue_head_t conn_wait;

	atomic_t recv_threads;
	wait_queue_head_t recv_wq;
	loff_t blksize;
	loff_t bytesize;
#if IS_ENABLED(CONFIG_DEBUG_FS)
	struct dentry *dbg_dir;
#endif
};

struct nbd_device {
	struct blk_mq_tag_set tag_set;

	int index;
	refcount_t config_refs;
	refcount_t refs;
	struct nbd_config *config;
	struct mutex config_lock;
	struct gendisk *disk;

	struct list_head list;
	struct task_struct *task_recv;
	struct task_struct *task_setup;
};

#define NBD_CMD_REQUEUED	1

struct nbd_cmd {
	struct nbd_device *nbd;
	struct mutex lock;
	int index;
	int cookie;
	blk_status_t status;
	unsigned long flags;
	u32 cmd_cookie;
};

#if IS_ENABLED(CONFIG_DEBUG_FS)
static struct dentry *nbd_dbg_dir;
#endif

#define nbd_name(nbd) ((nbd)->disk->disk_name)

#define NBD_MAGIC 0x68797548

static unsigned int nbds_max = 16;
static int max_part = 16;
static struct workqueue_struct *recv_workqueue;
static int part_shift;

static int nbd_dev_dbg_init(struct nbd_device *nbd);
static void nbd_dev_dbg_close(struct nbd_device *nbd);
static void nbd_config_put(struct nbd_device *nbd);
static void nbd_connect_reply(struct genl_info *info, int index);
static int nbd_genl_status(struct sk_buff *skb, struct genl_info *info);
static void nbd_dead_link_work(struct work_struct *work);
static void nbd_disconnect_and_put(struct nbd_device *nbd);

static inline struct device *nbd_to_dev(struct nbd_device *nbd)
{
	return disk_to_dev(nbd->disk);
}

static void nbd_requeue_cmd(struct nbd_cmd *cmd)
{
	struct request *req = blk_mq_rq_from_pdu(cmd);

	if (!test_and_set_bit(NBD_CMD_REQUEUED, &cmd->flags))
		blk_mq_requeue_request(req, true);
}

#define NBD_COOKIE_BITS 32

static u64 nbd_cmd_handle(struct nbd_cmd *cmd)
{
	struct request *req = blk_mq_rq_from_pdu(cmd);
	u32 tag = blk_mq_unique_tag(req);
	u64 cookie = cmd->cmd_cookie;

	return (cookie << NBD_COOKIE_BITS) | tag;
}

static u32 nbd_handle_to_tag(u64 handle)
{
	return (u32)handle;
}

static u32 nbd_handle_to_cookie(u64 handle)
{
	return (u32)(handle >> NBD_COOKIE_BITS);
}

static const char *nbdcmd_to_ascii(int cmd)
{
	switch (cmd) {
	case  NBD_CMD_READ: return "read";
	case NBD_CMD_WRITE: return "write";
	case  NBD_CMD_DISC: return "disconnect";
	case NBD_CMD_FLUSH: return "flush";
	case  NBD_CMD_TRIM: return "trim/discard";
	}
	return "invalid";
}

static ssize_t pid_show(struct device *dev,
			struct device_attribute *attr, char *buf)
{
	struct gendisk *disk = dev_to_disk(dev);
	struct nbd_device *nbd = (struct nbd_device *)disk->private_data;

	return sprintf(buf, "%d\n", task_pid_nr(nbd->task_recv));
}

static const struct device_attribute pid_attr = {
	.attr = { .name = "pid", .mode = 0444},
	.show = pid_show,
};

static void nbd_dev_remove(struct nbd_device *nbd)
{
	struct gendisk *disk = nbd->disk;
	struct request_queue *q;

	if (disk) {
		q = disk->queue;
		del_gendisk(disk);
		blk_cleanup_queue(q);
		blk_mq_free_tag_set(&nbd->tag_set);
		disk->private_data = NULL;
		put_disk(disk);
	}
	kfree(nbd);
}

static void nbd_put(struct nbd_device *nbd)
{
	if (refcount_dec_and_mutex_lock(&nbd->refs,
					&nbd_index_mutex)) {
		idr_remove(&nbd_index_idr, nbd->index);
		mutex_unlock(&nbd_index_mutex);
		nbd_dev_remove(nbd);
	}
}

static int nbd_disconnected(struct nbd_config *config)
{
	return test_bit(NBD_DISCONNECTED, &config->runtime_flags) ||
		test_bit(NBD_DISCONNECT_REQUESTED, &config->runtime_flags);
}

static void nbd_mark_nsock_dead(struct nbd_device *nbd, struct nbd_sock *nsock,
				int notify)
{
	if (!nsock->dead && notify && !nbd_disconnected(nbd->config)) {
		struct link_dead_args *args;
		args = kmalloc(sizeof(struct link_dead_args), GFP_NOIO);
		if (args) {
			INIT_WORK(&args->work, nbd_dead_link_work);
			args->index = nbd->index;
			queue_work(system_wq, &args->work);
		}
	}
	if (!nsock->dead) {
		kernel_sock_shutdown(nsock->sock, SHUT_RDWR);
		if (atomic_dec_return(&nbd->config->live_connections) == 0) {
			if (test_and_clear_bit(NBD_DISCONNECT_REQUESTED,
					       &nbd->config->runtime_flags)) {
				set_bit(NBD_DISCONNECTED,
					&nbd->config->runtime_flags);
				dev_info(nbd_to_dev(nbd),
					"Disconnected due to user request.\n");
			}
		}
	}
	nsock->dead = true;
	nsock->pending = NULL;
	nsock->sent = 0;
}

static void nbd_size_clear(struct nbd_device *nbd)
{
	if (nbd->config->bytesize) {
		set_capacity(nbd->disk, 0);
		kobject_uevent(&nbd_to_dev(nbd)->kobj, KOBJ_CHANGE);
	}
}

static void nbd_size_update(struct nbd_device *nbd)
{
	struct nbd_config *config = nbd->config;
	struct block_device *bdev = bdget_disk(nbd->disk, 0);

	if (config->flags & NBD_FLAG_SEND_TRIM) {
		nbd->disk->queue->limits.discard_granularity = config->blksize;
		nbd->disk->queue->limits.discard_alignment = config->blksize;
		blk_queue_max_discard_sectors(nbd->disk->queue, UINT_MAX);
	}
	blk_queue_logical_block_size(nbd->disk->queue, config->blksize);
	blk_queue_physical_block_size(nbd->disk->queue, config->blksize);
	set_capacity(nbd->disk, config->bytesize >> 9);
	if (bdev) {
		if (bdev->bd_disk)
			bd_set_size(bdev, config->bytesize);
		else
			bdev->bd_invalidated = 1;
		bdput(bdev);
	}
	kobject_uevent(&nbd_to_dev(nbd)->kobj, KOBJ_CHANGE);
}

static void nbd_size_set(struct nbd_device *nbd, loff_t blocksize,
			 loff_t nr_blocks)
{
	struct nbd_config *config = nbd->config;
	config->blksize = blocksize;
	config->bytesize = blocksize * nr_blocks;
	if (nbd->task_recv != NULL)
		nbd_size_update(nbd);
}

static void nbd_complete_rq(struct request *req)
{
	struct nbd_cmd *cmd = blk_mq_rq_to_pdu(req);

	dev_dbg(nbd_to_dev(cmd->nbd), "request %p: %s\n", req,
		cmd->status ? "failed" : "done");

	blk_mq_end_request(req, cmd->status);
}

/*
 * Forcibly shutdown the socket causing all listeners to error
 */
static void sock_shutdown(struct nbd_device *nbd)
{
	struct nbd_config *config = nbd->config;
	int i;

	if (config->num_connections == 0)
		return;
	if (test_and_set_bit(NBD_DISCONNECTED, &config->runtime_flags))
		return;

	for (i = 0; i < config->num_connections; i++) {
		struct nbd_sock *nsock = config->socks[i];
		mutex_lock(&nsock->tx_lock);
		nbd_mark_nsock_dead(nbd, nsock, 0);
		mutex_unlock(&nsock->tx_lock);
	}
	dev_warn(disk_to_dev(nbd->disk), "shutting down sockets\n");
}

static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req,
						 bool reserved)
{
	struct nbd_cmd *cmd = blk_mq_rq_to_pdu(req);
	struct nbd_device *nbd = cmd->nbd;
	struct nbd_config *config;

	if (!refcount_inc_not_zero(&nbd->config_refs)) {
		cmd->status = BLK_STS_TIMEOUT;
		goto done;
	}
	config = nbd->config;

	if (!mutex_trylock(&cmd->lock))
		return BLK_EH_RESET_TIMER;

	if (config->num_connections > 1) {
		dev_err_ratelimited(nbd_to_dev(nbd),
				    "Connection timed out, retrying (%d/%d alive)\n",
				    atomic_read(&config->live_connections),
				    config->num_connections);
		/*
		 * Hooray we have more connections, requeue this IO, the submit
		 * path will put it on a real connection.
		 */
		if (config->socks && config->num_connections > 1) {
			if (cmd->index < config->num_connections) {
				struct nbd_sock *nsock =
					config->socks[cmd->index];
				mutex_lock(&nsock->tx_lock);
				/* We can have multiple outstanding requests, so
				 * we don't want to mark the nsock dead if we've
				 * already reconnected with a new socket, so
				 * only mark it dead if its the same socket we
				 * were sent out on.
				 */
				if (cmd->cookie == nsock->cookie)
					nbd_mark_nsock_dead(nbd, nsock, 1);
				mutex_unlock(&nsock->tx_lock);
			}
			mutex_unlock(&cmd->lock);
			nbd_requeue_cmd(cmd);
			nbd_config_put(nbd);
			return BLK_EH_DONE;
		}
	} else {
		dev_err_ratelimited(nbd_to_dev(nbd),
				    "Connection timed out\n");
	}
	set_bit(NBD_TIMEDOUT, &config->runtime_flags);
	cmd->status = BLK_STS_IOERR;
	mutex_unlock(&cmd->lock);
	sock_shutdown(nbd);
	nbd_config_put(nbd);
done:
	blk_mq_complete_request(req);
	return BLK_EH_DONE;
}

/*
 *  Send or receive packet.
 */
static int sock_xmit(struct nbd_device *nbd, int index, int send,
		     struct iov_iter *iter, int msg_flags, int *sent)
{
	struct nbd_config *config = nbd->config;
	struct socket *sock = config->socks[index]->sock;
	int result;
	struct msghdr msg;
	unsigned int noreclaim_flag;

	if (unlikely(!sock)) {
		dev_err_ratelimited(disk_to_dev(nbd->disk),
			"Attempted %s on closed socket in sock_xmit\n",
			(send ? "send" : "recv"));
		return -EINVAL;
	}

	msg.msg_iter = *iter;

	noreclaim_flag = memalloc_noreclaim_save();
	do {
		sock->sk->sk_allocation = GFP_NOIO | __GFP_MEMALLOC;
		msg.msg_name = NULL;
		msg.msg_namelen = 0;
		msg.msg_control = NULL;
		msg.msg_controllen = 0;
		msg.msg_flags = msg_flags | MSG_NOSIGNAL;

		if (send)
			result = sock_sendmsg(sock, &msg);
		else
			result = sock_recvmsg(sock, &msg, msg.msg_flags);

		if (result <= 0) {
			if (result == 0)
				result = -EPIPE; /* short read */
			break;
		}
		if (sent)
			*sent += result;
	} while (msg_data_left(&msg));

	memalloc_noreclaim_restore(noreclaim_flag);

	return result;
}

/*
 * Different settings for sk->sk_sndtimeo can result in different return values
 * if there is a signal pending when we enter sendmsg, because reasons?
 */
static inline int was_interrupted(int result)
{
	return result == -ERESTARTSYS || result == -EINTR;
}

/* always call with the tx_lock held */
static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index)
{
	struct request *req = blk_mq_rq_from_pdu(cmd);
	struct nbd_config *config = nbd->config;
	struct nbd_sock *nsock = config->socks[index];
	int result;
	struct nbd_request request = {.magic = htonl(NBD_REQUEST_MAGIC)};
	struct kvec iov = {.iov_base = &request, .iov_len = sizeof(request)};
	struct iov_iter from;
	unsigned long size = blk_rq_bytes(req);
	struct bio *bio;
	u64 handle;
	u32 type;
	u32 nbd_cmd_flags = 0;
	int sent = nsock->sent, skip = 0;

	iov_iter_kvec(&from, WRITE, &iov, 1, sizeof(request));

	switch (req_op(req)) {
	case REQ_OP_DISCARD:
		type = NBD_CMD_TRIM;
		break;
	case REQ_OP_FLUSH:
		type = NBD_CMD_FLUSH;
		break;
	case REQ_OP_WRITE:
		type = NBD_CMD_WRITE;
		break;
	case REQ_OP_READ:
		type = NBD_CMD_READ;
		break;
	default:
		return -EIO;
	}

	if (rq_data_dir(req) == WRITE &&
	    (config->flags & NBD_FLAG_READ_ONLY)) {
		dev_err_ratelimited(disk_to_dev(nbd->disk),
				    "Write on read-only\n");
		return -EIO;
	}

	if (req->cmd_flags & REQ_FUA)
		nbd_cmd_flags |= NBD_CMD_FLAG_FUA;

	/* We did a partial send previously, and we at least sent the whole
	 * request struct, so just go and send the rest of the pages in the
	 * request.
	 */
	if (sent) {
		if (sent >= sizeof(request)) {
			skip = sent - sizeof(request);
			goto send_pages;
		}
		iov_iter_advance(&from, sent);
	} else {
		cmd->cmd_cookie++;
	}
	cmd->index = index;
	cmd->cookie = nsock->cookie;
	request.type = htonl(type | nbd_cmd_flags);
	if (type != NBD_CMD_FLUSH) {
		request.from = cpu_to_be64((u64)blk_rq_pos(req) << 9);
		request.len = htonl(size);
	}
	handle = nbd_cmd_handle(cmd);
	memcpy(request.handle, &handle, sizeof(handle));

	dev_dbg(nbd_to_dev(nbd), "request %p: sending control (%s@%llu,%uB)\n",
		req, nbdcmd_to_ascii(type),
		(unsigned long long)blk_rq_pos(req) << 9, blk_rq_bytes(req));
	result = sock_xmit(nbd, index, 1, &from,
			(type == NBD_CMD_WRITE) ? MSG_MORE : 0, &sent);
	if (result <= 0) {
		if (was_interrupted(result)) {
			/* If we havne't sent anything we can just return BUSY,
			 * however if we have sent something we need to make
			 * sure we only allow this req to be sent until we are
			 * completely done.
			 */
			if (sent) {
				nsock->pending = req;
				nsock->sent = sent;
			}
			set_bit(NBD_CMD_REQUEUED, &cmd->flags);
			return BLK_STS_RESOURCE;
		}
		dev_err_ratelimited(disk_to_dev(nbd->disk),
			"Send control failed (result %d)\n", result);
		return -EAGAIN;
	}
send_pages:
	if (type != NBD_CMD_WRITE)
		goto out;

	bio = req->bio;
	while (bio) {
		struct bio *next = bio->bi_next;
		struct bvec_iter iter;
		struct bio_vec bvec;

		bio_for_each_segment(bvec, bio, iter) {
			bool is_last = !next && bio_iter_last(bvec, iter);
			int flags = is_last ? 0 : MSG_MORE;

			dev_dbg(nbd_to_dev(nbd), "request %p: sending %d bytes data\n",
				req, bvec.bv_len);
			iov_iter_bvec(&from, WRITE, &bvec, 1, bvec.bv_len);
			if (skip) {
				if (skip >= iov_iter_count(&from)) {
					skip -= iov_iter_count(&from);
					continue;
				}
				iov_iter_advance(&from, skip);
				skip = 0;
			}
			result = sock_xmit(nbd, index, 1, &from, flags, &sent);
			if (result <= 0) {
				if (was_interrupted(result)) {
					/* We've already sent the header, we
					 * have no choice but to set pending and
					 * return BUSY.
					 */
					nsock->pending = req;
					nsock->sent = sent;
					set_bit(NBD_CMD_REQUEUED, &cmd->flags);
					return BLK_STS_RESOURCE;
				}
				dev_err(disk_to_dev(nbd->disk),
					"Send data failed (result %d)\n",
					result);
				return -EAGAIN;
			}
			/*
			 * The completion might already have come in,
			 * so break for the last one instead of letting
			 * the iterator do it. This prevents use-after-free
			 * of the bio.
			 */
			if (is_last)
				break;
		}
		bio = next;
	}
out:
	nsock->pending = NULL;
	nsock->sent = 0;
	return 0;
}

/* NULL returned = something went wrong, inform userspace */
static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index)
{
	struct nbd_config *config = nbd->config;
	int result;
	struct nbd_reply reply;
	struct nbd_cmd *cmd;
	struct request *req = NULL;
	u64 handle;
	u16 hwq;
	u32 tag;
	struct kvec iov = {.iov_base = &reply, .iov_len = sizeof(reply)};
	struct iov_iter to;
	int ret = 0;

	reply.magic = 0;
	iov_iter_kvec(&to, READ, &iov, 1, sizeof(reply));
	result = sock_xmit(nbd, index, 0, &to, MSG_WAITALL, NULL);
	if (result <= 0) {
		if (!nbd_disconnected(config))
			dev_err(disk_to_dev(nbd->disk),
				"Receive control failed (result %d)\n", result);
		return ERR_PTR(result);
	}

	if (ntohl(reply.magic) != NBD_REPLY_MAGIC) {
		dev_err(disk_to_dev(nbd->disk), "Wrong magic (0x%lx)\n",
				(unsigned long)ntohl(reply.magic));
		return ERR_PTR(-EPROTO);
	}

	memcpy(&handle, reply.handle, sizeof(handle));
	tag = nbd_handle_to_tag(handle);
	hwq = blk_mq_unique_tag_to_hwq(tag);
	if (hwq < nbd->tag_set.nr_hw_queues)
		req = blk_mq_tag_to_rq(nbd->tag_set.tags[hwq],
				       blk_mq_unique_tag_to_tag(tag));
	if (!req || !blk_mq_request_started(req)) {
		dev_err(disk_to_dev(nbd->disk), "Unexpected reply (%d) %p\n",
			tag, req);
		return ERR_PTR(-ENOENT);
	}
	cmd = blk_mq_rq_to_pdu(req);

	mutex_lock(&cmd->lock);
	if (cmd->cmd_cookie != nbd_handle_to_cookie(handle)) {
		dev_err(disk_to_dev(nbd->disk), "Double reply on req %p, cmd_cookie %u, handle cookie %u\n",
			req, cmd->cmd_cookie, nbd_handle_to_cookie(handle));
		ret = -ENOENT;
		goto out;
	}
	if (test_bit(NBD_CMD_REQUEUED, &cmd->flags)) {
		dev_err(disk_to_dev(nbd->disk), "Raced with timeout on req %p\n",
			req);
		ret = -ENOENT;
		goto out;
	}
	if (ntohl(reply.error)) {
		dev_err(disk_to_dev(nbd->disk), "Other side returned error (%d)\n",
			ntohl(reply.error));
		cmd->status = BLK_STS_IOERR;
		goto out;
	}

	dev_dbg(nbd_to_dev(nbd), "request %p: got reply\n", req);
	if (rq_data_dir(req) != WRITE) {
		struct req_iterator iter;
		struct bio_vec bvec;

		rq_for_each_segment(bvec, req, iter) {
			iov_iter_bvec(&to, READ, &bvec, 1, bvec.bv_len);
			result = sock_xmit(nbd, index, 0, &to, MSG_WAITALL, NULL);
			if (result <= 0) {
				dev_err(disk_to_dev(nbd->disk), "Receive data failed (result %d)\n",
					result);
				/*
				 * If we've disconnected or we only have 1
				 * connection then we need to make sure we
				 * complete this request, otherwise error out
				 * and let the timeout stuff handle resubmitting
				 * this request onto another connection.
				 */
				if (nbd_disconnected(config) ||
				    config->num_connections <= 1) {
					cmd->status = BLK_STS_IOERR;
					goto out;
				}
				ret = -EIO;
				goto out;
			}
			dev_dbg(nbd_to_dev(nbd), "request %p: got %d bytes data\n",
				req, bvec.bv_len);
		}
	}
out:
	mutex_unlock(&cmd->lock);
	return ret ? ERR_PTR(ret) : cmd;
}

static void recv_work(struct work_struct *work)
{
	struct recv_thread_args *args = container_of(work,
						     struct recv_thread_args,
						     work);
	struct nbd_device *nbd = args->nbd;
	struct nbd_config *config = nbd->config;
	struct nbd_cmd *cmd;

	while (1) {
		cmd = nbd_read_stat(nbd, args->index);
		if (IS_ERR(cmd)) {
			struct nbd_sock *nsock = config->socks[args->index];

			mutex_lock(&nsock->tx_lock);
			nbd_mark_nsock_dead(nbd, nsock, 1);
			mutex_unlock(&nsock->tx_lock);
			break;
		}

		blk_mq_complete_request(blk_mq_rq_from_pdu(cmd));
	}
	atomic_dec(&config->recv_threads);
	wake_up(&config->recv_wq);
	nbd_config_put(nbd);
	kfree(args);
}

static bool nbd_clear_req(struct request *req, void *data, bool reserved)
{
	struct nbd_cmd *cmd = blk_mq_rq_to_pdu(req);

	cmd->status = BLK_STS_IOERR;
	blk_mq_complete_request(req);
	return true;
}

static void nbd_clear_que(struct nbd_device *nbd)
{
	blk_mq_quiesce_queue(nbd->disk->queue);
	blk_mq_tagset_busy_iter(&nbd->tag_set, nbd_clear_req, NULL);
	blk_mq_unquiesce_queue(nbd->disk->queue);
	dev_dbg(disk_to_dev(nbd->disk), "queue cleared\n");
}

static int find_fallback(struct nbd_device *nbd, int index)
{
	struct nbd_config *config = nbd->config;
	int new_index = -1;
	struct nbd_sock *nsock = config->socks[index];
	int fallback = nsock->fallback_index;

	if (test_bit(NBD_DISCONNECTED, &config->runtime_flags))
		return new_index;

	if (config->num_connections <= 1) {
		dev_err_ratelimited(disk_to_dev(nbd->disk),
				    "Attempted send on invalid socket\n");
		return new_index;
	}

	if (fallback >= 0 && fallback < config->num_connections &&
	    !config->socks[fallback]->dead)
		return fallback;

	if (nsock->fallback_index < 0 ||
	    nsock->fallback_index >= config->num_connections ||
	    config->socks[nsock->fallback_index]->dead) {
		int i;
		for (i = 0; i < config->num_connections; i++) {
			if (i == index)
				continue;
			if (!config->socks[i]->dead) {
				new_index = i;
				break;
			}
		}
		nsock->fallback_index = new_index;
		if (new_index < 0) {
			dev_err_ratelimited(disk_to_dev(nbd->disk),
					    "Dead connection, failed to find a fallback\n");
			return new_index;
		}
	}
	new_index = nsock->fallback_index;
	return new_index;
}

static int wait_for_reconnect(struct nbd_device *nbd)
{
	struct nbd_config *config = nbd->config;
	if (!config->dead_conn_timeout)
		return 0;
	if (test_bit(NBD_DISCONNECTED, &config->runtime_flags))
		return 0;
	return wait_event_timeout(config->conn_wait,
				  atomic_read(&config->live_connections) > 0,
				  config->dead_conn_timeout) > 0;
}

static int nbd_handle_cmd(struct nbd_cmd *cmd, int index)
{
	struct request *req = blk_mq_rq_from_pdu(cmd);
	struct nbd_device *nbd = cmd->nbd;
	struct nbd_config *config;
	struct nbd_sock *nsock;
	int ret;

	if (!refcount_inc_not_zero(&nbd->config_refs)) {
		dev_err_ratelimited(disk_to_dev(nbd->disk),
				    "Socks array is empty\n");
		blk_mq_start_request(req);
		return -EINVAL;
	}
	config = nbd->config;

	if (index >= config->num_connections) {
		dev_err_ratelimited(disk_to_dev(nbd->disk),
				    "Attempted send on invalid socket\n");
		nbd_config_put(nbd);
		blk_mq_start_request(req);
		return -EINVAL;
	}
	cmd->status = BLK_STS_OK;
again:
	nsock = config->socks[index];
	mutex_lock(&nsock->tx_lock);
	if (nsock->dead) {
		int old_index = index;
		index = find_fallback(nbd, index);
		mutex_unlock(&nsock->tx_lock);
		if (index < 0) {
			if (wait_for_reconnect(nbd)) {
				index = old_index;
				goto again;
			}
			/* All the sockets should already be down at this point,
			 * we just want to make sure that DISCONNECTED is set so
			 * any requests that come in that were queue'ed waiting
			 * for the reconnect timer don't trigger the timer again
			 * and instead just error out.
			 */
			sock_shutdown(nbd);
			nbd_config_put(nbd);
			blk_mq_start_request(req);
			return -EIO;
		}
		goto again;
	}

	/* Handle the case that we have a pending request that was partially
	 * transmitted that _has_ to be serviced first.  We need to call requeue
	 * here so that it gets put _after_ the request that is already on the
	 * dispatch list.
	 */
	blk_mq_start_request(req);
	if (unlikely(nsock->pending && nsock->pending != req)) {
		nbd_requeue_cmd(cmd);
		ret = 0;
		goto out;
	}
	/*
	 * Some failures are related to the link going down, so anything that
	 * returns EAGAIN can be retried on a different socket.
	 */
	ret = nbd_send_cmd(nbd, cmd, index);
	if (ret == -EAGAIN) {
		dev_err_ratelimited(disk_to_dev(nbd->disk),
				    "Request send failed, requeueing\n");
		nbd_mark_nsock_dead(nbd, nsock, 1);
		nbd_requeue_cmd(cmd);
		ret = 0;
	}
out:
	mutex_unlock(&nsock->tx_lock);
	nbd_config_put(nbd);
	return ret;
}

static blk_status_t nbd_queue_rq(struct blk_mq_hw_ctx *hctx,
			const struct blk_mq_queue_data *bd)
{
	struct nbd_cmd *cmd = blk_mq_rq_to_pdu(bd->rq);
	int ret;

	/*
	 * Since we look at the bio's to send the request over the network we
	 * need to make sure the completion work doesn't mark this request done
	 * before we are done doing our send.  This keeps us from dereferencing
	 * freed data if we have particularly fast completions (ie we get the
	 * completion before we exit sock_xmit on the last bvec) or in the case
	 * that the server is misbehaving (or there was an error) before we're
	 * done sending everything over the wire.
	 */
	mutex_lock(&cmd->lock);
	clear_bit(NBD_CMD_REQUEUED, &cmd->flags);

	/* We can be called directly from the user space process, which means we
	 * could possibly have signals pending so our sendmsg will fail.  In
	 * this case we need to return that we are busy, otherwise error out as
	 * appropriate.
	 */
	ret = nbd_handle_cmd(cmd, hctx->queue_num);
	if (ret < 0)
		ret = BLK_STS_IOERR;
	else if (!ret)
		ret = BLK_STS_OK;
	mutex_unlock(&cmd->lock);

	return ret;
}

static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,
			  bool netlink)
{
	struct nbd_config *config = nbd->config;
	struct socket *sock;
	struct nbd_sock **socks;
	struct nbd_sock *nsock;
	int err;

	sock = sockfd_lookup(arg, &err);
	if (!sock)
		return err;

	if (!netlink && !nbd->task_setup &&
	    !test_bit(NBD_BOUND, &config->runtime_flags))
		nbd->task_setup = current;

	if (!netlink &&
	    (nbd->task_setup != current ||
	     test_bit(NBD_BOUND, &config->runtime_flags))) {
		dev_err(disk_to_dev(nbd->disk),
			"Device being setup by another task");
		sockfd_put(sock);
		return -EBUSY;
	}

	socks = krealloc(config->socks, (config->num_connections + 1) *
			 sizeof(struct nbd_sock *), GFP_KERNEL);
	if (!socks) {
		sockfd_put(sock);
		return -ENOMEM;
	}
	nsock = kzalloc(sizeof(struct nbd_sock), GFP_KERNEL);
	if (!nsock) {
		sockfd_put(sock);
		return -ENOMEM;
	}

	config->socks = socks;

	nsock->fallback_index = -1;
	nsock->dead = false;
	mutex_init(&nsock->tx_lock);
	nsock->sock = sock;
	nsock->pending = NULL;
	nsock->sent = 0;
	nsock->cookie = 0;
	socks[config->num_connections++] = nsock;
	atomic_inc(&config->live_connections);

	return 0;
}

static int nbd_reconnect_socket(struct nbd_device *nbd, unsigned long arg)
{
	struct nbd_config *config = nbd->config;
	struct socket *sock, *old;
	struct recv_thread_args *args;
	int i;
	int err;

	sock = sockfd_lookup(arg, &err);
	if (!sock)
		return err;

	args = kzalloc(sizeof(*args), GFP_KERNEL);
	if (!args) {
		sockfd_put(sock);
		return -ENOMEM;
	}

	for (i = 0; i < config->num_connections; i++) {
		struct nbd_sock *nsock = config->socks[i];

		if (!nsock->dead)
			continue;

		mutex_lock(&nsock->tx_lock);
		if (!nsock->dead) {
			mutex_unlock(&nsock->tx_lock);
			continue;
		}
		sk_set_memalloc(sock->sk);
		if (nbd->tag_set.timeout)
			sock->sk->sk_sndtimeo = nbd->tag_set.timeout;
		atomic_inc(&config->recv_threads);
		refcount_inc(&nbd->config_refs);
		old = nsock->sock;
		nsock->fallback_index = -1;
		nsock->sock = sock;
		nsock->dead = false;
		INIT_WORK(&args->work, recv_work);
		args->index = i;
		args->nbd = nbd;
		nsock->cookie++;
		mutex_unlock(&nsock->tx_lock);
		sockfd_put(old);

		clear_bit(NBD_DISCONNECTED, &config->runtime_flags);

		/* We take the tx_mutex in an error path in the recv_work, so we
		 * need to queue_work outside of the tx_mutex.
		 */
		queue_work(recv_workqueue, &args->work);

		atomic_inc(&config->live_connections);
		wake_up(&config->conn_wait);
		return 0;
	}
	sockfd_put(sock);
	kfree(args);
	return -ENOSPC;
}

static void nbd_bdev_reset(struct block_device *bdev)
{
	if (bdev->bd_openers > 1)
		return;
	bd_set_size(bdev, 0);
}

static void nbd_parse_flags(struct nbd_device *nbd)
{
	struct nbd_config *config = nbd->config;
	if (config->flags & NBD_FLAG_READ_ONLY)
		set_disk_ro(nbd->disk, true);
	else
		set_disk_ro(nbd->disk, false);
	if (config->flags & NBD_FLAG_SEND_TRIM)
		blk_queue_flag_set(QUEUE_FLAG_DISCARD, nbd->disk->queue);
	if (config->flags & NBD_FLAG_SEND_FLUSH) {
		if (config->flags & NBD_FLAG_SEND_FUA)
			blk_queue_write_cache(nbd->disk->queue, true, true);
		else
			blk_queue_write_cache(nbd->disk->queue, true, false);
	}
	else
		blk_queue_write_cache(nbd->disk->queue, false, false);
}

static void send_disconnects(struct nbd_device *nbd)
{
	struct nbd_config *config = nbd->config;
	struct nbd_request request = {
		.magic = htonl(NBD_REQUEST_MAGIC),
		.type = htonl(NBD_CMD_DISC),
	};
	struct kvec iov = {.iov_base = &request, .iov_len = sizeof(request)};
	struct iov_iter from;
	int i, ret;

	for (i = 0; i < config->num_connections; i++) {
		struct nbd_sock *nsock = config->socks[i];

		iov_iter_kvec(&from, WRITE, &iov, 1, sizeof(request));
		mutex_lock(&nsock->tx_lock);
		ret = sock_xmit(nbd, i, 1, &from, 0, NULL);
		if (ret <= 0)
			dev_err(disk_to_dev(nbd->disk),
				"Send disconnect failed %d\n", ret);
		mutex_unlock(&nsock->tx_lock);
	}
}

static int nbd_disconnect(struct nbd_device *nbd)
{
	struct nbd_config *config = nbd->config;

	dev_info(disk_to_dev(nbd->disk), "NBD_DISCONNECT\n");
	set_bit(NBD_DISCONNECT_REQUESTED, &config->runtime_flags);
	send_disconnects(nbd);
	return 0;
}

static void nbd_clear_sock(struct nbd_device *nbd)
{
	sock_shutdown(nbd);
	nbd_clear_que(nbd);
	nbd->task_setup = NULL;
}

static void nbd_config_put(struct nbd_device *nbd)
{
	if (refcount_dec_and_mutex_lock(&nbd->config_refs,
					&nbd->config_lock)) {
		struct nbd_config *config = nbd->config;
		nbd_dev_dbg_close(nbd);
		nbd_size_clear(nbd);
		if (test_and_clear_bit(NBD_HAS_PID_FILE,
				       &config->runtime_flags))
			device_remove_file(disk_to_dev(nbd->disk), &pid_attr);
		nbd->task_recv = NULL;
		nbd_clear_sock(nbd);
		if (config->num_connections) {
			int i;
			for (i = 0; i < config->num_connections; i++) {
				sockfd_put(config->socks[i]->sock);
				kfree(config->socks[i]);
			}
			kfree(config->socks);
		}
		kfree(nbd->config);
		nbd->config = NULL;

		nbd->tag_set.timeout = 0;
		nbd->disk->queue->limits.discard_granularity = 0;
		nbd->disk->queue->limits.discard_alignment = 0;
		blk_queue_max_discard_sectors(nbd->disk->queue, UINT_MAX);
		blk_queue_flag_clear(QUEUE_FLAG_DISCARD, nbd->disk->queue);

		mutex_unlock(&nbd->config_lock);
		nbd_put(nbd);
		module_put(THIS_MODULE);
	}
}

static int nbd_start_device(struct nbd_device *nbd)
{
	struct nbd_config *config = nbd->config;
	int num_connections = config->num_connections;
	int error = 0, i;

	if (nbd->task_recv)
		return -EBUSY;
	if (!config->socks)
		return -EINVAL;
	if (num_connections > 1 &&
	    !(config->flags & NBD_FLAG_CAN_MULTI_CONN)) {
		dev_err(disk_to_dev(nbd->disk), "server does not support multiple connections per device.\n");
		return -EINVAL;
	}

	blk_mq_update_nr_hw_queues(&nbd->tag_set, config->num_connections);
	nbd->task_recv = current;

	nbd_parse_flags(nbd);

	error = device_create_file(disk_to_dev(nbd->disk), &pid_attr);
	if (error) {
		dev_err(disk_to_dev(nbd->disk), "device_create_file failed!\n");
		return error;
	}
	set_bit(NBD_HAS_PID_FILE, &config->runtime_flags);

	nbd_dev_dbg_init(nbd);
	for (i = 0; i < num_connections; i++) {
		struct recv_thread_args *args;

		args = kzalloc(sizeof(*args), GFP_KERNEL);
		if (!args) {
			sock_shutdown(nbd);
			return -ENOMEM;
		}
		sk_set_memalloc(config->socks[i]->sock->sk);
		if (nbd->tag_set.timeout)
			config->socks[i]->sock->sk->sk_sndtimeo =
				nbd->tag_set.timeout;
		atomic_inc(&config->recv_threads);
		refcount_inc(&nbd->config_refs);
		INIT_WORK(&args->work, recv_work);
		args->nbd = nbd;
		args->index = i;
		queue_work(recv_workqueue, &args->work);
	}
	nbd_size_update(nbd);
	return error;
}

static int nbd_start_device_ioctl(struct nbd_device *nbd, struct block_device *bdev)
{
	struct nbd_config *config = nbd->config;
	int ret;

	ret = nbd_start_device(nbd);
	if (ret)
		return ret;

	if (max_part)
		bdev->bd_invalidated = 1;
	mutex_unlock(&nbd->config_lock);
	ret = wait_event_interruptible(config->recv_wq,
					 atomic_read(&config->recv_threads) == 0);
	if (ret)
		sock_shutdown(nbd);
	mutex_lock(&nbd->config_lock);
	nbd_bdev_reset(bdev);
	/* user requested, ignore socket errors */
	if (test_bit(NBD_DISCONNECT_REQUESTED, &config->runtime_flags))
		ret = 0;
	if (test_bit(NBD_TIMEDOUT, &config->runtime_flags))
		ret = -ETIMEDOUT;
	return ret;
}

static void nbd_clear_sock_ioctl(struct nbd_device *nbd,
				 struct block_device *bdev)
{
	sock_shutdown(nbd);
	kill_bdev(bdev);
	nbd_bdev_reset(bdev);
	if (test_and_clear_bit(NBD_HAS_CONFIG_REF,
			       &nbd->config->runtime_flags))
		nbd_config_put(nbd);
}

/* Must be called with config_lock held */
static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
		       unsigned int cmd, unsigned long arg)
{
	struct nbd_config *config = nbd->config;

	switch (cmd) {
	case NBD_DISCONNECT:
		return nbd_disconnect(nbd);
	case NBD_CLEAR_SOCK:
		nbd_clear_sock_ioctl(nbd, bdev);
		return 0;
	case NBD_SET_SOCK:
		return nbd_add_socket(nbd, arg, false);
	case NBD_SET_BLKSIZE:
		if (!arg || !is_power_of_2(arg) || arg < 512 ||
		    arg > PAGE_SIZE)
			return -EINVAL;
		nbd_size_set(nbd, arg,
			     div_s64(config->bytesize, arg));
		return 0;
	case NBD_SET_SIZE:
		nbd_size_set(nbd, config->blksize,
			     div_s64(arg, config->blksize));
		return 0;
	case NBD_SET_SIZE_BLOCKS:
		nbd_size_set(nbd, config->blksize, arg);
		return 0;
	case NBD_SET_TIMEOUT:
		if (arg) {
			nbd->tag_set.timeout = arg * HZ;
			blk_queue_rq_timeout(nbd->disk->queue, arg * HZ);
		}
		return 0;

	case NBD_SET_FLAGS:
		config->flags = arg;
		return 0;
	case NBD_DO_IT:
		return nbd_start_device_ioctl(nbd, bdev);
	case NBD_CLEAR_QUE:
		/*
		 * This is for compatibility only.  The queue is always cleared
		 * by NBD_DO_IT or NBD_CLEAR_SOCK.
		 */
		return 0;
	case NBD_PRINT_DEBUG:
		/*
		 * For compatibility only, we no longer keep a list of
		 * outstanding requests.
		 */
		return 0;
	}
	return -ENOTTY;
}

static int nbd_ioctl(struct block_device *bdev, fmode_t mode,
		     unsigned int cmd, unsigned long arg)
{
	struct nbd_device *nbd = bdev->bd_disk->private_data;
	struct nbd_config *config = nbd->config;
	int error = -EINVAL;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	/* The block layer will pass back some non-nbd ioctls in case we have
	 * special handling for them, but we don't so just return an error.
	 */
	if (_IOC_TYPE(cmd) != 0xab)
		return -EINVAL;

	mutex_lock(&nbd->config_lock);

	/* Don't allow ioctl operations on a nbd device that was created with
	 * netlink, unless it's DISCONNECT or CLEAR_SOCK, which are fine.
	 */
	if (!test_bit(NBD_BOUND, &config->runtime_flags) ||
	    (cmd == NBD_DISCONNECT || cmd == NBD_CLEAR_SOCK))
		error = __nbd_ioctl(bdev, nbd, cmd, arg);
	else
		dev_err(nbd_to_dev(nbd), "Cannot use ioctl interface on a netlink controlled device.\n");
	mutex_unlock(&nbd->config_lock);
	return error;
}

static struct nbd_config *nbd_alloc_config(void)
{
	struct nbd_config *config;

	config = kzalloc(sizeof(struct nbd_config), GFP_NOFS);
	if (!config)
		return NULL;
	atomic_set(&config->recv_threads, 0);
	init_waitqueue_head(&config->recv_wq);
	init_waitqueue_head(&config->conn_wait);
	config->blksize = 1024;
	atomic_set(&config->live_connections, 0);
	try_module_get(THIS_MODULE);
	return config;
}

static int nbd_open(struct block_device *bdev, fmode_t mode)
{
	struct nbd_device *nbd;
	int ret = 0;

	mutex_lock(&nbd_index_mutex);
	nbd = bdev->bd_disk->private_data;
	if (!nbd) {
		ret = -ENXIO;
		goto out;
	}
	if (!refcount_inc_not_zero(&nbd->refs)) {
		ret = -ENXIO;
		goto out;
	}
	if (!refcount_inc_not_zero(&nbd->config_refs)) {
		struct nbd_config *config;

		mutex_lock(&nbd->config_lock);
		if (refcount_inc_not_zero(&nbd->config_refs)) {
			mutex_unlock(&nbd->config_lock);
			goto out;
		}
		config = nbd->config = nbd_alloc_config();
		if (!config) {
			ret = -ENOMEM;
			mutex_unlock(&nbd->config_lock);
			goto out;
		}
		refcount_set(&nbd->config_refs, 1);
		refcount_inc(&nbd->refs);
		mutex_unlock(&nbd->config_lock);
		bdev->bd_invalidated = 1;
	} else if (nbd_disconnected(nbd->config)) {
		bdev->bd_invalidated = 1;
	}
out:
	mutex_unlock(&nbd_index_mutex);
	return ret;
}

static void nbd_release(struct gendisk *disk, fmode_t mode)
{
	struct nbd_device *nbd = disk->private_data;
	struct block_device *bdev = bdget_disk(disk, 0);

	if (test_bit(NBD_DISCONNECT_ON_CLOSE, &nbd->config->runtime_flags) &&
			bdev->bd_openers == 0)
		nbd_disconnect_and_put(nbd);

	nbd_config_put(nbd);
	nbd_put(nbd);
}

static const struct block_device_operations nbd_fops =
{
	.owner =	THIS_MODULE,
	.open =		nbd_open,
	.release =	nbd_release,
	.ioctl =	nbd_ioctl,
	.compat_ioctl =	nbd_ioctl,
};

#if IS_ENABLED(CONFIG_DEBUG_FS)

static int nbd_dbg_tasks_show(struct seq_file *s, void *unused)
{
	struct nbd_device *nbd = s->private;

	if (nbd->task_recv)
		seq_printf(s, "recv: %d\n", task_pid_nr(nbd->task_recv));

	return 0;
}

static int nbd_dbg_tasks_open(struct inode *inode, struct file *file)
{
	return single_open(file, nbd_dbg_tasks_show, inode->i_private);
}

static const struct file_operations nbd_dbg_tasks_ops = {
	.open = nbd_dbg_tasks_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
};

static int nbd_dbg_flags_show(struct seq_file *s, void *unused)
{
	struct nbd_device *nbd = s->private;
	u32 flags = nbd->config->flags;

	seq_printf(s, "Hex: 0x%08x\n\n", flags);

	seq_puts(s, "Known flags:\n");

	if (flags & NBD_FLAG_HAS_FLAGS)
		seq_puts(s, "NBD_FLAG_HAS_FLAGS\n");
	if (flags & NBD_FLAG_READ_ONLY)
		seq_puts(s, "NBD_FLAG_READ_ONLY\n");
	if (flags & NBD_FLAG_SEND_FLUSH)
		seq_puts(s, "NBD_FLAG_SEND_FLUSH\n");
	if (flags & NBD_FLAG_SEND_FUA)
		seq_puts(s, "NBD_FLAG_SEND_FUA\n");
	if (flags & NBD_FLAG_SEND_TRIM)
		seq_puts(s, "NBD_FLAG_SEND_TRIM\n");

	return 0;
}

static int nbd_dbg_flags_open(struct inode *inode, struct file *file)
{
	return single_open(file, nbd_dbg_flags_show, inode->i_private);
}

static const struct file_operations nbd_dbg_flags_ops = {
	.open = nbd_dbg_flags_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
};

static int nbd_dev_dbg_init(struct nbd_device *nbd)
{
	struct dentry *dir;
	struct nbd_config *config = nbd->config;

	if (!nbd_dbg_dir)
		return -EIO;

	dir = debugfs_create_dir(nbd_name(nbd), nbd_dbg_dir);
	if (!dir) {
		dev_err(nbd_to_dev(nbd), "Failed to create debugfs dir for '%s'\n",
			nbd_name(nbd));
		return -EIO;
	}
	config->dbg_dir = dir;

	debugfs_create_file("tasks", 0444, dir, nbd, &nbd_dbg_tasks_ops);
	debugfs_create_u64("size_bytes", 0444, dir, &config->bytesize);
	debugfs_create_u32("timeout", 0444, dir, &nbd->tag_set.timeout);
	debugfs_create_u64("blocksize", 0444, dir, &config->blksize);
	debugfs_create_file("flags", 0444, dir, nbd, &nbd_dbg_flags_ops);

	return 0;
}

static void nbd_dev_dbg_close(struct nbd_device *nbd)
{
	debugfs_remove_recursive(nbd->config->dbg_dir);
}

static int nbd_dbg_init(void)
{
	struct dentry *dbg_dir;

	dbg_dir = debugfs_create_dir("nbd", NULL);
	if (!dbg_dir)
		return -EIO;

	nbd_dbg_dir = dbg_dir;

	return 0;
}

static void nbd_dbg_close(void)
{
	debugfs_remove_recursive(nbd_dbg_dir);
}

#else  /* IS_ENABLED(CONFIG_DEBUG_FS) */

static int nbd_dev_dbg_init(struct nbd_device *nbd)
{
	return 0;
}

static void nbd_dev_dbg_close(struct nbd_device *nbd)
{
}

static int nbd_dbg_init(void)
{
	return 0;
}

static void nbd_dbg_close(void)
{
}

#endif

static int nbd_init_request(struct blk_mq_tag_set *set, struct request *rq,
			    unsigned int hctx_idx, unsigned int numa_node)
{
	struct nbd_cmd *cmd = blk_mq_rq_to_pdu(rq);
	cmd->nbd = set->driver_data;
	cmd->flags = 0;
	mutex_init(&cmd->lock);
	return 0;
}

static const struct blk_mq_ops nbd_mq_ops = {
	.queue_rq	= nbd_queue_rq,
	.complete	= nbd_complete_rq,
	.init_request	= nbd_init_request,
	.timeout	= nbd_xmit_timeout,
};

static int nbd_dev_add(int index)
{
	struct nbd_device *nbd;
	struct gendisk *disk;
	struct request_queue *q;
	int err = -ENOMEM;

	nbd = kzalloc(sizeof(struct nbd_device), GFP_KERNEL);
	if (!nbd)
		goto out;

	disk = alloc_disk(1 << part_shift);
	if (!disk)
		goto out_free_nbd;

	if (index >= 0) {
		err = idr_alloc(&nbd_index_idr, nbd, index, index + 1,
				GFP_KERNEL);
		if (err == -ENOSPC)
			err = -EEXIST;
	} else {
		err = idr_alloc(&nbd_index_idr, nbd, 0, 0, GFP_KERNEL);
		if (err >= 0)
			index = err;
	}
	if (err < 0)
		goto out_free_disk;

	nbd->index = index;
	nbd->disk = disk;
	nbd->tag_set.ops = &nbd_mq_ops;
	nbd->tag_set.nr_hw_queues = 1;
	nbd->tag_set.queue_depth = 128;
	nbd->tag_set.numa_node = NUMA_NO_NODE;
	nbd->tag_set.cmd_size = sizeof(struct nbd_cmd);
	nbd->tag_set.flags = BLK_MQ_F_SHOULD_MERGE |
		BLK_MQ_F_SG_MERGE | BLK_MQ_F_BLOCKING;
	nbd->tag_set.driver_data = nbd;

	err = blk_mq_alloc_tag_set(&nbd->tag_set);
	if (err)
		goto out_free_idr;

	q = blk_mq_init_queue(&nbd->tag_set);
	if (IS_ERR(q)) {
		err = PTR_ERR(q);
		goto out_free_tags;
	}
	disk->queue = q;

	/*
	 * Tell the block layer that we are not a rotational device
	 */
	blk_queue_flag_set(QUEUE_FLAG_NONROT, disk->queue);
	blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, disk->queue);
	disk->queue->limits.discard_granularity = 0;
	disk->queue->limits.discard_alignment = 0;
	blk_queue_max_discard_sectors(disk->queue, 0);
	blk_queue_max_segment_size(disk->queue, UINT_MAX);
	blk_queue_max_segments(disk->queue, USHRT_MAX);
	blk_queue_max_hw_sectors(disk->queue, 65536);
	disk->queue->limits.max_sectors = 256;

	mutex_init(&nbd->config_lock);
	refcount_set(&nbd->config_refs, 0);
	refcount_set(&nbd->refs, 1);
	INIT_LIST_HEAD(&nbd->list);
	disk->major = NBD_MAJOR;
	disk->first_minor = index << part_shift;
	disk->fops = &nbd_fops;
	disk->private_data = nbd;
	sprintf(disk->disk_name, "nbd%d", index);
	add_disk(disk);
	nbd_total_devices++;
	return index;

out_free_tags:
	blk_mq_free_tag_set(&nbd->tag_set);
out_free_idr:
	idr_remove(&nbd_index_idr, index);
out_free_disk:
	put_disk(disk);
out_free_nbd:
	kfree(nbd);
out:
	return err;
}

static int find_free_cb(int id, void *ptr, void *data)
{
	struct nbd_device *nbd = ptr;
	struct nbd_device **found = data;

	if (!refcount_read(&nbd->config_refs)) {
		*found = nbd;
		return 1;
	}
	return 0;
}

/* Netlink interface. */
static const struct nla_policy nbd_attr_policy[NBD_ATTR_MAX + 1] = {
	[NBD_ATTR_INDEX]		=	{ .type = NLA_U32 },
	[NBD_ATTR_SIZE_BYTES]		=	{ .type = NLA_U64 },
	[NBD_ATTR_BLOCK_SIZE_BYTES]	=	{ .type = NLA_U64 },
	[NBD_ATTR_TIMEOUT]		=	{ .type = NLA_U64 },
	[NBD_ATTR_SERVER_FLAGS]		=	{ .type = NLA_U64 },
	[NBD_ATTR_CLIENT_FLAGS]		=	{ .type = NLA_U64 },
	[NBD_ATTR_SOCKETS]		=	{ .type = NLA_NESTED},
	[NBD_ATTR_DEAD_CONN_TIMEOUT]	=	{ .type = NLA_U64 },
	[NBD_ATTR_DEVICE_LIST]		=	{ .type = NLA_NESTED},
};

static const struct nla_policy nbd_sock_policy[NBD_SOCK_MAX + 1] = {
	[NBD_SOCK_FD]			=	{ .type = NLA_U32 },
};

/* We don't use this right now since we don't parse the incoming list, but we
 * still want it here so userspace knows what to expect.
 */
static const struct nla_policy __attribute__((unused))
nbd_device_policy[NBD_DEVICE_ATTR_MAX + 1] = {
	[NBD_DEVICE_INDEX]		=	{ .type = NLA_U32 },
	[NBD_DEVICE_CONNECTED]		=	{ .type = NLA_U8 },
};

static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info)
{
	struct nbd_device *nbd = NULL;
	struct nbd_config *config;
	int index = -1;
	int ret;
	bool put_dev = false;

	if (!netlink_capable(skb, CAP_SYS_ADMIN))
		return -EPERM;

	if (info->attrs[NBD_ATTR_INDEX])
		index = nla_get_u32(info->attrs[NBD_ATTR_INDEX]);
	if (!info->attrs[NBD_ATTR_SOCKETS]) {
		printk(KERN_ERR "nbd: must specify at least one socket\n");
		return -EINVAL;
	}
	if (!info->attrs[NBD_ATTR_SIZE_BYTES]) {
		printk(KERN_ERR "nbd: must specify a size in bytes for the device\n");
		return -EINVAL;
	}
again:
	mutex_lock(&nbd_index_mutex);
	if (index == -1) {
		ret = idr_for_each(&nbd_index_idr, &find_free_cb, &nbd);
		if (ret == 0) {
			int new_index;
			new_index = nbd_dev_add(-1);
			if (new_index < 0) {
				mutex_unlock(&nbd_index_mutex);
				printk(KERN_ERR "nbd: failed to add new device\n");
				return new_index;
			}
			nbd = idr_find(&nbd_index_idr, new_index);
		}
	} else {
		nbd = idr_find(&nbd_index_idr, index);
		if (!nbd) {
			ret = nbd_dev_add(index);
			if (ret < 0) {
				mutex_unlock(&nbd_index_mutex);
				printk(KERN_ERR "nbd: failed to add new device\n");
				return ret;
			}
			nbd = idr_find(&nbd_index_idr, index);
		}
	}
	if (!nbd) {
		printk(KERN_ERR "nbd: couldn't find device at index %d\n",
		       index);
		mutex_unlock(&nbd_index_mutex);
		return -EINVAL;
	}
	if (!refcount_inc_not_zero(&nbd->refs)) {
		mutex_unlock(&nbd_index_mutex);
		if (index == -1)
			goto again;
		printk(KERN_ERR "nbd: device at index %d is going down\n",
		       index);
		return -EINVAL;
	}
	mutex_unlock(&nbd_index_mutex);

	mutex_lock(&nbd->config_lock);
	if (refcount_read(&nbd->config_refs)) {
		mutex_unlock(&nbd->config_lock);
		nbd_put(nbd);
		if (index == -1)
			goto again;
		printk(KERN_ERR "nbd: nbd%d already in use\n", index);
		return -EBUSY;
	}
	if (WARN_ON(nbd->config)) {
		mutex_unlock(&nbd->config_lock);
		nbd_put(nbd);
		return -EINVAL;
	}
	config = nbd->config = nbd_alloc_config();
	if (!nbd->config) {
		mutex_unlock(&nbd->config_lock);
		nbd_put(nbd);
		printk(KERN_ERR "nbd: couldn't allocate config\n");
		return -ENOMEM;
	}
	refcount_set(&nbd->config_refs, 1);
	set_bit(NBD_BOUND, &config->runtime_flags);

	if (info->attrs[NBD_ATTR_SIZE_BYTES]) {
		u64 bytes = nla_get_u64(info->attrs[NBD_ATTR_SIZE_BYTES]);
		nbd_size_set(nbd, config->blksize,
			     div64_u64(bytes, config->blksize));
	}
	if (info->attrs[NBD_ATTR_BLOCK_SIZE_BYTES]) {
		u64 bsize =
			nla_get_u64(info->attrs[NBD_ATTR_BLOCK_SIZE_BYTES]);
		nbd_size_set(nbd, bsize, div64_u64(config->bytesize, bsize));
	}
	if (info->attrs[NBD_ATTR_TIMEOUT]) {
		u64 timeout = nla_get_u64(info->attrs[NBD_ATTR_TIMEOUT]);
		nbd->tag_set.timeout = timeout * HZ;
		blk_queue_rq_timeout(nbd->disk->queue, timeout * HZ);
	}
	if (info->attrs[NBD_ATTR_DEAD_CONN_TIMEOUT]) {
		config->dead_conn_timeout =
			nla_get_u64(info->attrs[NBD_ATTR_DEAD_CONN_TIMEOUT]);
		config->dead_conn_timeout *= HZ;
	}
	if (info->attrs[NBD_ATTR_SERVER_FLAGS])
		config->flags =
			nla_get_u64(info->attrs[NBD_ATTR_SERVER_FLAGS]);
	if (info->attrs[NBD_ATTR_CLIENT_FLAGS]) {
		u64 flags = nla_get_u64(info->attrs[NBD_ATTR_CLIENT_FLAGS]);
		if (flags & NBD_CFLAG_DESTROY_ON_DISCONNECT) {
			set_bit(NBD_DESTROY_ON_DISCONNECT,
				&config->runtime_flags);
			put_dev = true;
		}
		if (flags & NBD_CFLAG_DISCONNECT_ON_CLOSE) {
			set_bit(NBD_DISCONNECT_ON_CLOSE,
				&config->runtime_flags);
		}
	}

	if (info->attrs[NBD_ATTR_SOCKETS]) {
		struct nlattr *attr;
		int rem, fd;

		nla_for_each_nested(attr, info->attrs[NBD_ATTR_SOCKETS],
				    rem) {
			struct nlattr *socks[NBD_SOCK_MAX+1];

			if (nla_type(attr) != NBD_SOCK_ITEM) {
				printk(KERN_ERR "nbd: socks must be embedded in a SOCK_ITEM attr\n");
				ret = -EINVAL;
				goto out;
			}
			ret = nla_parse_nested(socks, NBD_SOCK_MAX, attr,
					       nbd_sock_policy, info->extack);
			if (ret != 0) {
				printk(KERN_ERR "nbd: error processing sock list\n");
				ret = -EINVAL;
				goto out;
			}
			if (!socks[NBD_SOCK_FD])
				continue;
			fd = (int)nla_get_u32(socks[NBD_SOCK_FD]);
			ret = nbd_add_socket(nbd, fd, true);
			if (ret)
				goto out;
		}
	}
	ret = nbd_start_device(nbd);
out:
	mutex_unlock(&nbd->config_lock);
	if (!ret) {
		set_bit(NBD_HAS_CONFIG_REF, &config->runtime_flags);
		refcount_inc(&nbd->config_refs);
		nbd_connect_reply(info, nbd->index);
	}
	nbd_config_put(nbd);
	if (put_dev)
		nbd_put(nbd);
	return ret;
}

static void nbd_disconnect_and_put(struct nbd_device *nbd)
{
	mutex_lock(&nbd->config_lock);
	nbd_disconnect(nbd);
	nbd_clear_sock(nbd);
	mutex_unlock(&nbd->config_lock);
	if (test_and_clear_bit(NBD_HAS_CONFIG_REF,
			       &nbd->config->runtime_flags))
		nbd_config_put(nbd);
}

static int nbd_genl_disconnect(struct sk_buff *skb, struct genl_info *info)
{
	struct nbd_device *nbd;
	int index;

	if (!netlink_capable(skb, CAP_SYS_ADMIN))
		return -EPERM;

	if (!info->attrs[NBD_ATTR_INDEX]) {
		printk(KERN_ERR "nbd: must specify an index to disconnect\n");
		return -EINVAL;
	}
	index = nla_get_u32(info->attrs[NBD_ATTR_INDEX]);
	mutex_lock(&nbd_index_mutex);
	nbd = idr_find(&nbd_index_idr, index);
	if (!nbd) {
		mutex_unlock(&nbd_index_mutex);
		printk(KERN_ERR "nbd: couldn't find device at index %d\n",
		       index);
		return -EINVAL;
	}
	if (!refcount_inc_not_zero(&nbd->refs)) {
		mutex_unlock(&nbd_index_mutex);
		printk(KERN_ERR "nbd: device at index %d is going down\n",
		       index);
		return -EINVAL;
	}
	mutex_unlock(&nbd_index_mutex);
	if (!refcount_inc_not_zero(&nbd->config_refs)) {
		nbd_put(nbd);
		return 0;
	}
	nbd_disconnect_and_put(nbd);
	nbd_config_put(nbd);
	nbd_put(nbd);
	return 0;
}

static int nbd_genl_reconfigure(struct sk_buff *skb, struct genl_info *info)
{
	struct nbd_device *nbd = NULL;
	struct nbd_config *config;
	int index;
	int ret = 0;
	bool put_dev = false;

	if (!netlink_capable(skb, CAP_SYS_ADMIN))
		return -EPERM;

	if (!info->attrs[NBD_ATTR_INDEX]) {
		printk(KERN_ERR "nbd: must specify a device to reconfigure\n");
		return -EINVAL;
	}
	index = nla_get_u32(info->attrs[NBD_ATTR_INDEX]);
	mutex_lock(&nbd_index_mutex);
	nbd = idr_find(&nbd_index_idr, index);
	if (!nbd) {
		mutex_unlock(&nbd_index_mutex);
		printk(KERN_ERR "nbd: couldn't find a device at index %d\n",
		       index);
		return -EINVAL;
	}
	if (!refcount_inc_not_zero(&nbd->refs)) {
		mutex_unlock(&nbd_index_mutex);
		printk(KERN_ERR "nbd: device at index %d is going down\n",
		       index);
		return -EINVAL;
	}
	mutex_unlock(&nbd_index_mutex);

	if (!refcount_inc_not_zero(&nbd->config_refs)) {
		dev_err(nbd_to_dev(nbd),
			"not configured, cannot reconfigure\n");
		nbd_put(nbd);
		return -EINVAL;
	}

	mutex_lock(&nbd->config_lock);
	config = nbd->config;
	if (!test_bit(NBD_BOUND, &config->runtime_flags) ||
	    !nbd->task_recv) {
		dev_err(nbd_to_dev(nbd),
			"not configured, cannot reconfigure\n");
		ret = -EINVAL;
		goto out;
	}

	if (info->attrs[NBD_ATTR_TIMEOUT]) {
		u64 timeout = nla_get_u64(info->attrs[NBD_ATTR_TIMEOUT]);
		nbd->tag_set.timeout = timeout * HZ;
		blk_queue_rq_timeout(nbd->disk->queue, timeout * HZ);
	}
	if (info->attrs[NBD_ATTR_DEAD_CONN_TIMEOUT]) {
		config->dead_conn_timeout =
			nla_get_u64(info->attrs[NBD_ATTR_DEAD_CONN_TIMEOUT]);
		config->dead_conn_timeout *= HZ;
	}
	if (info->attrs[NBD_ATTR_CLIENT_FLAGS]) {
		u64 flags = nla_get_u64(info->attrs[NBD_ATTR_CLIENT_FLAGS]);
		if (flags & NBD_CFLAG_DESTROY_ON_DISCONNECT) {
			if (!test_and_set_bit(NBD_DESTROY_ON_DISCONNECT,
					      &config->runtime_flags))
				put_dev = true;
		} else {
			if (test_and_clear_bit(NBD_DESTROY_ON_DISCONNECT,
					       &config->runtime_flags))
				refcount_inc(&nbd->refs);
		}

		if (flags & NBD_CFLAG_DISCONNECT_ON_CLOSE) {
			set_bit(NBD_DISCONNECT_ON_CLOSE,
					&config->runtime_flags);
		} else {
			clear_bit(NBD_DISCONNECT_ON_CLOSE,
					&config->runtime_flags);
		}
	}

	if (info->attrs[NBD_ATTR_SOCKETS]) {
		struct nlattr *attr;
		int rem, fd;

		nla_for_each_nested(attr, info->attrs[NBD_ATTR_SOCKETS],
				    rem) {
			struct nlattr *socks[NBD_SOCK_MAX+1];

			if (nla_type(attr) != NBD_SOCK_ITEM) {
				printk(KERN_ERR "nbd: socks must be embedded in a SOCK_ITEM attr\n");
				ret = -EINVAL;
				goto out;
			}
			ret = nla_parse_nested(socks, NBD_SOCK_MAX, attr,
					       nbd_sock_policy, info->extack);
			if (ret != 0) {
				printk(KERN_ERR "nbd: error processing sock list\n");
				ret = -EINVAL;
				goto out;
			}
			if (!socks[NBD_SOCK_FD])
				continue;
			fd = (int)nla_get_u32(socks[NBD_SOCK_FD]);
			ret = nbd_reconnect_socket(nbd, fd);
			if (ret) {
				if (ret == -ENOSPC)
					ret = 0;
				goto out;
			}
			dev_info(nbd_to_dev(nbd), "reconnected socket\n");
		}
	}
out:
	mutex_unlock(&nbd->config_lock);
	nbd_config_put(nbd);
	nbd_put(nbd);
	if (put_dev)
		nbd_put(nbd);
	return ret;
}

static const struct genl_ops nbd_connect_genl_ops[] = {
	{
		.cmd	= NBD_CMD_CONNECT,
		.policy	= nbd_attr_policy,
		.doit	= nbd_genl_connect,
	},
	{
		.cmd	= NBD_CMD_DISCONNECT,
		.policy	= nbd_attr_policy,
		.doit	= nbd_genl_disconnect,
	},
	{
		.cmd	= NBD_CMD_RECONFIGURE,
		.policy	= nbd_attr_policy,
		.doit	= nbd_genl_reconfigure,
	},
	{
		.cmd	= NBD_CMD_STATUS,
		.policy	= nbd_attr_policy,
		.doit	= nbd_genl_status,
	},
};

static const struct genl_multicast_group nbd_mcast_grps[] = {
	{ .name = NBD_GENL_MCAST_GROUP_NAME, },
};

static struct genl_family nbd_genl_family __ro_after_init = {
	.hdrsize	= 0,
	.name		= NBD_GENL_FAMILY_NAME,
	.version	= NBD_GENL_VERSION,
	.module		= THIS_MODULE,
	.ops		= nbd_connect_genl_ops,
	.n_ops		= ARRAY_SIZE(nbd_connect_genl_ops),
	.maxattr	= NBD_ATTR_MAX,
	.mcgrps		= nbd_mcast_grps,
	.n_mcgrps	= ARRAY_SIZE(nbd_mcast_grps),
};

static int populate_nbd_status(struct nbd_device *nbd, struct sk_buff *reply)
{
	struct nlattr *dev_opt;
	u8 connected = 0;
	int ret;

	/* This is a little racey, but for status it's ok.  The
	 * reason we don't take a ref here is because we can't
	 * take a ref in the index == -1 case as we would need
	 * to put under the nbd_index_mutex, which could
	 * deadlock if we are configured to remove ourselves
	 * once we're disconnected.
	 */
	if (refcount_read(&nbd->config_refs))
		connected = 1;
	dev_opt = nla_nest_start(reply, NBD_DEVICE_ITEM);
	if (!dev_opt)
		return -EMSGSIZE;
	ret = nla_put_u32(reply, NBD_DEVICE_INDEX, nbd->index);
	if (ret)
		return -EMSGSIZE;
	ret = nla_put_u8(reply, NBD_DEVICE_CONNECTED,
			 connected);
	if (ret)
		return -EMSGSIZE;
	nla_nest_end(reply, dev_opt);
	return 0;
}

static int status_cb(int id, void *ptr, void *data)
{
	struct nbd_device *nbd = ptr;
	return populate_nbd_status(nbd, (struct sk_buff *)data);
}

static int nbd_genl_status(struct sk_buff *skb, struct genl_info *info)
{
	struct nlattr *dev_list;
	struct sk_buff *reply;
	void *reply_head;
	size_t msg_size;
	int index = -1;
	int ret = -ENOMEM;

	if (info->attrs[NBD_ATTR_INDEX])
		index = nla_get_u32(info->attrs[NBD_ATTR_INDEX]);

	mutex_lock(&nbd_index_mutex);

	msg_size = nla_total_size(nla_attr_size(sizeof(u32)) +
				  nla_attr_size(sizeof(u8)));
	msg_size *= (index == -1) ? nbd_total_devices : 1;

	reply = genlmsg_new(msg_size, GFP_KERNEL);
	if (!reply)
		goto out;
	reply_head = genlmsg_put_reply(reply, info, &nbd_genl_family, 0,
				       NBD_CMD_STATUS);
	if (!reply_head) {
		nlmsg_free(reply);
		goto out;
	}

	dev_list = nla_nest_start(reply, NBD_ATTR_DEVICE_LIST);
	if (index == -1) {
		ret = idr_for_each(&nbd_index_idr, &status_cb, reply);
		if (ret) {
			nlmsg_free(reply);
			goto out;
		}
	} else {
		struct nbd_device *nbd;
		nbd = idr_find(&nbd_index_idr, index);
		if (nbd) {
			ret = populate_nbd_status(nbd, reply);
			if (ret) {
				nlmsg_free(reply);
				goto out;
			}
		}
	}
	nla_nest_end(reply, dev_list);
	genlmsg_end(reply, reply_head);
	genlmsg_reply(reply, info);
	ret = 0;
out:
	mutex_unlock(&nbd_index_mutex);
	return ret;
}

static void nbd_connect_reply(struct genl_info *info, int index)
{
	struct sk_buff *skb;
	void *msg_head;
	int ret;

	skb = genlmsg_new(nla_total_size(sizeof(u32)), GFP_KERNEL);
	if (!skb)
		return;
	msg_head = genlmsg_put_reply(skb, info, &nbd_genl_family, 0,
				     NBD_CMD_CONNECT);
	if (!msg_head) {
		nlmsg_free(skb);
		return;
	}
	ret = nla_put_u32(skb, NBD_ATTR_INDEX, index);
	if (ret) {
		nlmsg_free(skb);
		return;
	}
	genlmsg_end(skb, msg_head);
	genlmsg_reply(skb, info);
}

static void nbd_mcast_index(int index)
{
	struct sk_buff *skb;
	void *msg_head;
	int ret;

	skb = genlmsg_new(nla_total_size(sizeof(u32)), GFP_KERNEL);
	if (!skb)
		return;
	msg_head = genlmsg_put(skb, 0, 0, &nbd_genl_family, 0,
				     NBD_CMD_LINK_DEAD);
	if (!msg_head) {
		nlmsg_free(skb);
		return;
	}
	ret = nla_put_u32(skb, NBD_ATTR_INDEX, index);
	if (ret) {
		nlmsg_free(skb);
		return;
	}
	genlmsg_end(skb, msg_head);
	genlmsg_multicast(&nbd_genl_family, skb, 0, 0, GFP_KERNEL);
}

static void nbd_dead_link_work(struct work_struct *work)
{
	struct link_dead_args *args = container_of(work, struct link_dead_args,
						   work);
	nbd_mcast_index(args->index);
	kfree(args);
}

static int __init nbd_init(void)
{
	int i;

	BUILD_BUG_ON(sizeof(struct nbd_request) != 28);

	if (max_part < 0) {
		printk(KERN_ERR "nbd: max_part must be >= 0\n");
		return -EINVAL;
	}

	part_shift = 0;
	if (max_part > 0) {
		part_shift = fls(max_part);

		/*
		 * Adjust max_part according to part_shift as it is exported
		 * to user space so that user can know the max number of
		 * partition kernel should be able to manage.
		 *
		 * Note that -1 is required because partition 0 is reserved
		 * for the whole disk.
		 */
		max_part = (1UL << part_shift) - 1;
	}

	if ((1UL << part_shift) > DISK_MAX_PARTS)
		return -EINVAL;

	if (nbds_max > 1UL << (MINORBITS - part_shift))
		return -EINVAL;
	recv_workqueue = alloc_workqueue("knbd-recv",
					 WQ_MEM_RECLAIM | WQ_HIGHPRI |
					 WQ_UNBOUND, 0);
	if (!recv_workqueue)
		return -ENOMEM;

	if (register_blkdev(NBD_MAJOR, "nbd")) {
		destroy_workqueue(recv_workqueue);
		return -EIO;
	}

	if (genl_register_family(&nbd_genl_family)) {
		unregister_blkdev(NBD_MAJOR, "nbd");
		destroy_workqueue(recv_workqueue);
		return -EINVAL;
	}
	nbd_dbg_init();

	mutex_lock(&nbd_index_mutex);
	for (i = 0; i < nbds_max; i++)
		nbd_dev_add(i);
	mutex_unlock(&nbd_index_mutex);
	return 0;
}

static int nbd_exit_cb(int id, void *ptr, void *data)
{
	struct list_head *list = (struct list_head *)data;
	struct nbd_device *nbd = ptr;

	list_add_tail(&nbd->list, list);
	return 0;
}

static void __exit nbd_cleanup(void)
{
	struct nbd_device *nbd;
	LIST_HEAD(del_list);

	nbd_dbg_close();

	mutex_lock(&nbd_index_mutex);
	idr_for_each(&nbd_index_idr, &nbd_exit_cb, &del_list);
	mutex_unlock(&nbd_index_mutex);

	while (!list_empty(&del_list)) {
		nbd = list_first_entry(&del_list, struct nbd_device, list);
		list_del_init(&nbd->list);
		if (refcount_read(&nbd->refs) != 1)
			printk(KERN_ERR "nbd: possibly leaking a device\n");
		nbd_put(nbd);
	}

	idr_destroy(&nbd_index_idr);
	genl_unregister_family(&nbd_genl_family);
	destroy_workqueue(recv_workqueue);
	unregister_blkdev(NBD_MAJOR, "nbd");
}

module_init(nbd_init);
module_exit(nbd_cleanup);

MODULE_DESCRIPTION("Network Block Device");
MODULE_LICENSE("GPL");

module_param(nbds_max, int, 0444);
MODULE_PARM_DESC(nbds_max, "number of network block devices to initialize (default: 16)");
module_param(max_part, int, 0444);
MODULE_PARM_DESC(max_part, "number of partitions per device (default: 16)");