aboutsummaryrefslogtreecommitdiff
path: root/drivers/block/drbd/drbd_worker.c
blob: d348260301f11505d9e9edbd378808350da6d03e (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
/*
   drbd_worker.c

   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.

   Copyright (C) 2001-2008, LINBIT Information Technologies GmbH.
   Copyright (C) 1999-2008, Philipp Reisner <philipp.reisner@linbit.com>.
   Copyright (C) 2002-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.

   drbd is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   drbd is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with drbd; see the file COPYING.  If not, write to
   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.

 */

#include <linux/module.h>
#include <linux/drbd.h>
#include <linux/sched.h>
#include <linux/wait.h>
#include <linux/mm.h>
#include <linux/memcontrol.h>
#include <linux/mm_inline.h>
#include <linux/slab.h>
#include <linux/random.h>
#include <linux/string.h>
#include <linux/scatterlist.h>

#include "drbd_int.h"
#include "drbd_req.h"

static int w_make_ov_request(struct drbd_work *w, int cancel);


/* endio handlers:
 *   drbd_md_io_complete (defined here)
 *   drbd_request_endio (defined here)
 *   drbd_peer_request_endio (defined here)
 *   bm_async_io_complete (defined in drbd_bitmap.c)
 *
 * For all these callbacks, note the following:
 * The callbacks will be called in irq context by the IDE drivers,
 * and in Softirqs/Tasklets/BH context by the SCSI drivers.
 * Try to get the locking right :)
 *
 */


/* About the global_state_lock
   Each state transition on an device holds a read lock. In case we have
   to evaluate the resync after dependencies, we grab a write lock, because
   we need stable states on all devices for that.  */
rwlock_t global_state_lock;

/* used for synchronous meta data and bitmap IO
 * submitted by drbd_md_sync_page_io()
 */
void drbd_md_io_complete(struct bio *bio, int error)
{
	struct drbd_md_io *md_io;
	struct drbd_conf *mdev;

	md_io = (struct drbd_md_io *)bio->bi_private;
	mdev = container_of(md_io, struct drbd_conf, md_io);

	md_io->error = error;

	/* We grabbed an extra reference in _drbd_md_sync_page_io() to be able
	 * to timeout on the lower level device, and eventually detach from it.
	 * If this io completion runs after that timeout expired, this
	 * drbd_md_put_buffer() may allow us to finally try and re-attach.
	 * During normal operation, this only puts that extra reference
	 * down to 1 again.
	 * Make sure we first drop the reference, and only then signal
	 * completion, or we may (in drbd_al_read_log()) cycle so fast into the
	 * next drbd_md_sync_page_io(), that we trigger the
	 * ASSERT(atomic_read(&mdev->md_io_in_use) == 1) there.
	 */
	drbd_md_put_buffer(mdev);
	md_io->done = 1;
	wake_up(&mdev->misc_wait);
	bio_put(bio);
	put_ldev(mdev);
}

/* reads on behalf of the partner,
 * "submitted" by the receiver
 */
void drbd_endio_read_sec_final(struct drbd_peer_request *peer_req) __releases(local)
{
	unsigned long flags = 0;
	struct drbd_conf *mdev = peer_req->w.mdev;

	spin_lock_irqsave(&mdev->tconn->req_lock, flags);
	mdev->read_cnt += peer_req->i.size >> 9;
	list_del(&peer_req->w.list);
	if (list_empty(&mdev->read_ee))
		wake_up(&mdev->ee_wait);
	if (test_bit(__EE_WAS_ERROR, &peer_req->flags))
		__drbd_chk_io_error(mdev, DRBD_IO_ERROR);
	spin_unlock_irqrestore(&mdev->tconn->req_lock, flags);

	drbd_queue_work(&mdev->tconn->sender_work, &peer_req->w);
	put_ldev(mdev);
}

/* writes on behalf of the partner, or resync writes,
 * "submitted" by the receiver, final stage.  */
static void drbd_endio_write_sec_final(struct drbd_peer_request *peer_req) __releases(local)
{
	unsigned long flags = 0;
	struct drbd_conf *mdev = peer_req->w.mdev;
	struct drbd_interval i;
	int do_wake;
	u64 block_id;
	int do_al_complete_io;

	/* after we moved peer_req to done_ee,
	 * we may no longer access it,
	 * it may be freed/reused already!
	 * (as soon as we release the req_lock) */
	i = peer_req->i;
	do_al_complete_io = peer_req->flags & EE_CALL_AL_COMPLETE_IO;
	block_id = peer_req->block_id;

	spin_lock_irqsave(&mdev->tconn->req_lock, flags);
	mdev->writ_cnt += peer_req->i.size >> 9;
	list_move_tail(&peer_req->w.list, &mdev->done_ee);

	/*
	 * Do not remove from the write_requests tree here: we did not send the
	 * Ack yet and did not wake possibly waiting conflicting requests.
	 * Removed from the tree from "drbd_process_done_ee" within the
	 * appropriate w.cb (e_end_block/e_end_resync_block) or from
	 * _drbd_clear_done_ee.
	 */

	do_wake = list_empty(block_id == ID_SYNCER ? &mdev->sync_ee : &mdev->active_ee);

	if (test_bit(__EE_WAS_ERROR, &peer_req->flags))
		__drbd_chk_io_error(mdev, DRBD_IO_ERROR);
	spin_unlock_irqrestore(&mdev->tconn->req_lock, flags);

	if (block_id == ID_SYNCER)
		drbd_rs_complete_io(mdev, i.sector);

	if (do_wake)
		wake_up(&mdev->ee_wait);

	if (do_al_complete_io)
		drbd_al_complete_io(mdev, &i);

	wake_asender(mdev->tconn);
	put_ldev(mdev);
}

/* writes on behalf of the partner, or resync writes,
 * "submitted" by the receiver.
 */
void drbd_peer_request_endio(struct bio *bio, int error)
{
	struct drbd_peer_request *peer_req = bio->bi_private;
	struct drbd_conf *mdev = peer_req->w.mdev;
	int uptodate = bio_flagged(bio, BIO_UPTODATE);
	int is_write = bio_data_dir(bio) == WRITE;

	if (error && __ratelimit(&drbd_ratelimit_state))
		dev_warn(DEV, "%s: error=%d s=%llus\n",
				is_write ? "write" : "read", error,
				(unsigned long long)peer_req->i.sector);
	if (!error && !uptodate) {
		if (__ratelimit(&drbd_ratelimit_state))
			dev_warn(DEV, "%s: setting error to -EIO s=%llus\n",
					is_write ? "write" : "read",
					(unsigned long long)peer_req->i.sector);
		/* strange behavior of some lower level drivers...
		 * fail the request by clearing the uptodate flag,
		 * but do not return any error?! */
		error = -EIO;
	}

	if (error)
		set_bit(__EE_WAS_ERROR, &peer_req->flags);

	bio_put(bio); /* no need for the bio anymore */
	if (atomic_dec_and_test(&peer_req->pending_bios)) {
		if (is_write)
			drbd_endio_write_sec_final(peer_req);
		else
			drbd_endio_read_sec_final(peer_req);
	}
}

/* read, readA or write requests on R_PRIMARY coming from drbd_make_request
 */
void drbd_request_endio(struct bio *bio, int error)
{
	unsigned long flags;
	struct drbd_request *req = bio->bi_private;
	struct drbd_conf *mdev = req->w.mdev;
	struct bio_and_error m;
	enum drbd_req_event what;
	int uptodate = bio_flagged(bio, BIO_UPTODATE);

	if (!error && !uptodate) {
		dev_warn(DEV, "p %s: setting error to -EIO\n",
			 bio_data_dir(bio) == WRITE ? "write" : "read");
		/* strange behavior of some lower level drivers...
		 * fail the request by clearing the uptodate flag,
		 * but do not return any error?! */
		error = -EIO;
	}


	/* If this request was aborted locally before,
	 * but now was completed "successfully",
	 * chances are that this caused arbitrary data corruption.
	 *
	 * "aborting" requests, or force-detaching the disk, is intended for
	 * completely blocked/hung local backing devices which do no longer
	 * complete requests at all, not even do error completions.  In this
	 * situation, usually a hard-reset and failover is the only way out.
	 *
	 * By "aborting", basically faking a local error-completion,
	 * we allow for a more graceful swichover by cleanly migrating services.
	 * Still the affected node has to be rebooted "soon".
	 *
	 * By completing these requests, we allow the upper layers to re-use
	 * the associated data pages.
	 *
	 * If later the local backing device "recovers", and now DMAs some data
	 * from disk into the original request pages, in the best case it will
	 * just put random data into unused pages; but typically it will corrupt
	 * meanwhile completely unrelated data, causing all sorts of damage.
	 *
	 * Which means delayed successful completion,
	 * especially for READ requests,
	 * is a reason to panic().
	 *
	 * We assume that a delayed *error* completion is OK,
	 * though we still will complain noisily about it.
	 */
	if (unlikely(req->rq_state & RQ_LOCAL_ABORTED)) {
		if (__ratelimit(&drbd_ratelimit_state))
			dev_emerg(DEV, "delayed completion of aborted local request; disk-timeout may be too aggressive\n");

		if (!error)
			panic("possible random memory corruption caused by delayed completion of aborted local request\n");
	}

	/* to avoid recursion in __req_mod */
	if (unlikely(error)) {
		what = (bio_data_dir(bio) == WRITE)
			? WRITE_COMPLETED_WITH_ERROR
			: (bio_rw(bio) == READ)
			  ? READ_COMPLETED_WITH_ERROR
			  : READ_AHEAD_COMPLETED_WITH_ERROR;
	} else
		what = COMPLETED_OK;

	bio_put(req->private_bio);
	req->private_bio = ERR_PTR(error);

	/* not req_mod(), we need irqsave here! */
	spin_lock_irqsave(&mdev->tconn->req_lock, flags);
	__req_mod(req, what, &m);
	spin_unlock_irqrestore(&mdev->tconn->req_lock, flags);
	put_ldev(mdev);

	if (m.bio)
		complete_master_bio(mdev, &m);
}

void drbd_csum_ee(struct drbd_conf *mdev, struct crypto_hash *tfm,
		  struct drbd_peer_request *peer_req, void *digest)
{
	struct hash_desc desc;
	struct scatterlist sg;
	struct page *page = peer_req->pages;
	struct page *tmp;
	unsigned len;

	desc.tfm = tfm;
	desc.flags = 0;

	sg_init_table(&sg, 1);
	crypto_hash_init(&desc);

	while ((tmp = page_chain_next(page))) {
		/* all but the last page will be fully used */
		sg_set_page(&sg, page, PAGE_SIZE, 0);
		crypto_hash_update(&desc, &sg, sg.length);
		page = tmp;
	}
	/* and now the last, possibly only partially used page */
	len = peer_req->i.size & (PAGE_SIZE - 1);
	sg_set_page(&sg, page, len ?: PAGE_SIZE, 0);
	crypto_hash_update(&desc, &sg, sg.length);
	crypto_hash_final(&desc, digest);
}

void drbd_csum_bio(struct drbd_conf *mdev, struct crypto_hash *tfm, struct bio *bio, void *digest)
{
	struct hash_desc desc;
	struct scatterlist sg;
	struct bio_vec *bvec;
	int i;

	desc.tfm = tfm;
	desc.flags = 0;

	sg_init_table(&sg, 1);
	crypto_hash_init(&desc);

	bio_for_each_segment(bvec, bio, i) {
		sg_set_page(&sg, bvec->bv_page, bvec->bv_len, bvec->bv_offset);
		crypto_hash_update(&desc, &sg, sg.length);
	}
	crypto_hash_final(&desc, digest);
}

/* MAYBE merge common code with w_e_end_ov_req */
static int w_e_send_csum(struct drbd_work *w, int cancel)
{
	struct drbd_peer_request *peer_req = container_of(w, struct drbd_peer_request, w);
	struct drbd_conf *mdev = w->mdev;
	int digest_size;
	void *digest;
	int err = 0;

	if (unlikely(cancel))
		goto out;

	if (unlikely((peer_req->flags & EE_WAS_ERROR) != 0))
		goto out;

	digest_size = crypto_hash_digestsize(mdev->tconn->csums_tfm);
	digest = kmalloc(digest_size, GFP_NOIO);
	if (digest) {
		sector_t sector = peer_req->i.sector;
		unsigned int size = peer_req->i.size;
		drbd_csum_ee(mdev, mdev->tconn->csums_tfm, peer_req, digest);
		/* Free peer_req and pages before send.
		 * In case we block on congestion, we could otherwise run into
		 * some distributed deadlock, if the other side blocks on
		 * congestion as well, because our receiver blocks in
		 * drbd_alloc_pages due to pp_in_use > max_buffers. */
		drbd_free_peer_req(mdev, peer_req);
		peer_req = NULL;
		inc_rs_pending(mdev);
		err = drbd_send_drequest_csum(mdev, sector, size,
					      digest, digest_size,
					      P_CSUM_RS_REQUEST);
		kfree(digest);
	} else {
		dev_err(DEV, "kmalloc() of digest failed.\n");
		err = -ENOMEM;
	}

out:
	if (peer_req)
		drbd_free_peer_req(mdev, peer_req);

	if (unlikely(err))
		dev_err(DEV, "drbd_send_drequest(..., csum) failed\n");
	return err;
}

#define GFP_TRY	(__GFP_HIGHMEM | __GFP_NOWARN)

static int read_for_csum(struct drbd_conf *mdev, sector_t sector, int size)
{
	struct drbd_peer_request *peer_req;

	if (!get_ldev(mdev))
		return -EIO;

	if (drbd_rs_should_slow_down(mdev, sector))
		goto defer;

	/* GFP_TRY, because if there is no memory available right now, this may
	 * be rescheduled for later. It is "only" background resync, after all. */
	peer_req = drbd_alloc_peer_req(mdev, ID_SYNCER /* unused */, sector,
				       size, GFP_TRY);
	if (!peer_req)
		goto defer;

	peer_req->w.cb = w_e_send_csum;
	spin_lock_irq(&mdev->tconn->req_lock);
	list_add(&peer_req->w.list, &mdev->read_ee);
	spin_unlock_irq(&mdev->tconn->req_lock);

	atomic_add(size >> 9, &mdev->rs_sect_ev);
	if (drbd_submit_peer_request(mdev, peer_req, READ, DRBD_FAULT_RS_RD) == 0)
		return 0;

	/* If it failed because of ENOMEM, retry should help.  If it failed
	 * because bio_add_page failed (probably broken lower level driver),
	 * retry may or may not help.
	 * If it does not, you may need to force disconnect. */
	spin_lock_irq(&mdev->tconn->req_lock);
	list_del(&peer_req->w.list);
	spin_unlock_irq(&mdev->tconn->req_lock);

	drbd_free_peer_req(mdev, peer_req);
defer:
	put_ldev(mdev);
	return -EAGAIN;
}

int w_resync_timer(struct drbd_work *w, int cancel)
{
	struct drbd_conf *mdev = w->mdev;
	switch (mdev->state.conn) {
	case C_VERIFY_S:
		w_make_ov_request(w, cancel);
		break;
	case C_SYNC_TARGET:
		w_make_resync_request(w, cancel);
		break;
	}

	return 0;
}

void resync_timer_fn(unsigned long data)
{
	struct drbd_conf *mdev = (struct drbd_conf *) data;

	if (list_empty(&mdev->resync_work.list))
		drbd_queue_work(&mdev->tconn->sender_work, &mdev->resync_work);
}

static void fifo_set(struct fifo_buffer *fb, int value)
{
	int i;

	for (i = 0; i < fb->size; i++)
		fb->values[i] = value;
}

static int fifo_push(struct fifo_buffer *fb, int value)
{
	int ov;

	ov = fb->values[fb->head_index];
	fb->values[fb->head_index++] = value;

	if (fb->head_index >= fb->size)
		fb->head_index = 0;

	return ov;
}

static void fifo_add_val(struct fifo_buffer *fb, int value)
{
	int i;

	for (i = 0; i < fb->size; i++)
		fb->values[i] += value;
}

struct fifo_buffer *fifo_alloc(int fifo_size)
{
	struct fifo_buffer *fb;

	fb = kzalloc(sizeof(struct fifo_buffer) + sizeof(int) * fifo_size, GFP_NOIO);
	if (!fb)
		return NULL;

	fb->head_index = 0;
	fb->size = fifo_size;
	fb->total = 0;

	return fb;
}

static int drbd_rs_controller(struct drbd_conf *mdev)
{
	struct disk_conf *dc;
	unsigned int sect_in;  /* Number of sectors that came in since the last turn */
	unsigned int want;     /* The number of sectors we want in the proxy */
	int req_sect; /* Number of sectors to request in this turn */
	int correction; /* Number of sectors more we need in the proxy*/
	int cps; /* correction per invocation of drbd_rs_controller() */
	int steps; /* Number of time steps to plan ahead */
	int curr_corr;
	int max_sect;
	struct fifo_buffer *plan;

	sect_in = atomic_xchg(&mdev->rs_sect_in, 0); /* Number of sectors that came in */
	mdev->rs_in_flight -= sect_in;

	dc = rcu_dereference(mdev->ldev->disk_conf);
	plan = rcu_dereference(mdev->rs_plan_s);

	steps = plan->size; /* (dc->c_plan_ahead * 10 * SLEEP_TIME) / HZ; */

	if (mdev->rs_in_flight + sect_in == 0) { /* At start of resync */
		want = ((dc->resync_rate * 2 * SLEEP_TIME) / HZ) * steps;
	} else { /* normal path */
		want = dc->c_fill_target ? dc->c_fill_target :
			sect_in * dc->c_delay_target * HZ / (SLEEP_TIME * 10);
	}

	correction = want - mdev->rs_in_flight - plan->total;

	/* Plan ahead */
	cps = correction / steps;
	fifo_add_val(plan, cps);
	plan->total += cps * steps;

	/* What we do in this step */
	curr_corr = fifo_push(plan, 0);
	plan->total -= curr_corr;

	req_sect = sect_in + curr_corr;
	if (req_sect < 0)
		req_sect = 0;

	max_sect = (dc->c_max_rate * 2 * SLEEP_TIME) / HZ;
	if (req_sect > max_sect)
		req_sect = max_sect;

	/*
	dev_warn(DEV, "si=%u if=%d wa=%u co=%d st=%d cps=%d pl=%d cc=%d rs=%d\n",
		 sect_in, mdev->rs_in_flight, want, correction,
		 steps, cps, mdev->rs_planed, curr_corr, req_sect);
	*/

	return req_sect;
}

static int drbd_rs_number_requests(struct drbd_conf *mdev)
{
	int number;

	rcu_read_lock();
	if (rcu_dereference(mdev->rs_plan_s)->size) {
		number = drbd_rs_controller(mdev) >> (BM_BLOCK_SHIFT - 9);
		mdev->c_sync_rate = number * HZ * (BM_BLOCK_SIZE / 1024) / SLEEP_TIME;
	} else {
		mdev->c_sync_rate = rcu_dereference(mdev->ldev->disk_conf)->resync_rate;
		number = SLEEP_TIME * mdev->c_sync_rate  / ((BM_BLOCK_SIZE / 1024) * HZ);
	}
	rcu_read_unlock();

	/* ignore the amount of pending requests, the resync controller should
	 * throttle down to incoming reply rate soon enough anyways. */
	return number;
}

int w_make_resync_request(struct drbd_work *w, int cancel)
{
	struct drbd_conf *mdev = w->mdev;
	unsigned long bit;
	sector_t sector;
	const sector_t capacity = drbd_get_capacity(mdev->this_bdev);
	int max_bio_size;
	int number, rollback_i, size;
	int align, queued, sndbuf;
	int i = 0;

	if (unlikely(cancel))
		return 0;

	if (mdev->rs_total == 0) {
		/* empty resync? */
		drbd_resync_finished(mdev);
		return 0;
	}

	if (!get_ldev(mdev)) {
		/* Since we only need to access mdev->rsync a
		   get_ldev_if_state(mdev,D_FAILED) would be sufficient, but
		   to continue resync with a broken disk makes no sense at
		   all */
		dev_err(DEV, "Disk broke down during resync!\n");
		return 0;
	}

	max_bio_size = queue_max_hw_sectors(mdev->rq_queue) << 9;
	number = drbd_rs_number_requests(mdev);
	if (number == 0)
		goto requeue;

	for (i = 0; i < number; i++) {
		/* Stop generating RS requests, when half of the send buffer is filled */
		mutex_lock(&mdev->tconn->data.mutex);
		if (mdev->tconn->data.socket) {
			queued = mdev->tconn->data.socket->sk->sk_wmem_queued;
			sndbuf = mdev->tconn->data.socket->sk->sk_sndbuf;
		} else {
			queued = 1;
			sndbuf = 0;
		}
		mutex_unlock(&mdev->tconn->data.mutex);
		if (queued > sndbuf / 2)
			goto requeue;

next_sector:
		size = BM_BLOCK_SIZE;
		bit  = drbd_bm_find_next(mdev, mdev->bm_resync_fo);

		if (bit == DRBD_END_OF_BITMAP) {
			mdev->bm_resync_fo = drbd_bm_bits(mdev);
			put_ldev(mdev);
			return 0;
		}

		sector = BM_BIT_TO_SECT(bit);

		if (drbd_rs_should_slow_down(mdev, sector) ||
		    drbd_try_rs_begin_io(mdev, sector)) {
			mdev->bm_resync_fo = bit;
			goto requeue;
		}
		mdev->bm_resync_fo = bit + 1;

		if (unlikely(drbd_bm_test_bit(mdev, bit) == 0)) {
			drbd_rs_complete_io(mdev, sector);
			goto next_sector;
		}

#if DRBD_MAX_BIO_SIZE > BM_BLOCK_SIZE
		/* try to find some adjacent bits.
		 * we stop if we have already the maximum req size.
		 *
		 * Additionally always align bigger requests, in order to
		 * be prepared for all stripe sizes of software RAIDs.
		 */
		align = 1;
		rollback_i = i;
		for (;;) {
			if (size + BM_BLOCK_SIZE > max_bio_size)
				break;

			/* Be always aligned */
			if (sector & ((1<<(align+3))-1))
				break;

			/* do not cross extent boundaries */
			if (((bit+1) & BM_BLOCKS_PER_BM_EXT_MASK) == 0)
				break;
			/* now, is it actually dirty, after all?
			 * caution, drbd_bm_test_bit is tri-state for some
			 * obscure reason; ( b == 0 ) would get the out-of-band
			 * only accidentally right because of the "oddly sized"
			 * adjustment below */
			if (drbd_bm_test_bit(mdev, bit+1) != 1)
				break;
			bit++;
			size += BM_BLOCK_SIZE;
			if ((BM_BLOCK_SIZE << align) <= size)
				align++;
			i++;
		}
		/* if we merged some,
		 * reset the offset to start the next drbd_bm_find_next from */
		if (size > BM_BLOCK_SIZE)
			mdev->bm_resync_fo = bit + 1;
#endif

		/* adjust very last sectors, in case we are oddly sized */
		if (sector + (size>>9) > capacity)
			size = (capacity-sector)<<9;
		if (mdev->tconn->agreed_pro_version >= 89 && mdev->tconn->csums_tfm) {
			switch (read_for_csum(mdev, sector, size)) {
			case -EIO: /* Disk failure */
				put_ldev(mdev);
				return -EIO;
			case -EAGAIN: /* allocation failed, or ldev busy */
				drbd_rs_complete_io(mdev, sector);
				mdev->bm_resync_fo = BM_SECT_TO_BIT(sector);
				i = rollback_i;
				goto requeue;
			case 0:
				/* everything ok */
				break;
			default:
				BUG();
			}
		} else {
			int err;

			inc_rs_pending(mdev);
			err = drbd_send_drequest(mdev, P_RS_DATA_REQUEST,
						 sector, size, ID_SYNCER);
			if (err) {
				dev_err(DEV, "drbd_send_drequest() failed, aborting...\n");
				dec_rs_pending(mdev);
				put_ldev(mdev);
				return err;
			}
		}
	}

	if (mdev->bm_resync_fo >= drbd_bm_bits(mdev)) {
		/* last syncer _request_ was sent,
		 * but the P_RS_DATA_REPLY not yet received.  sync will end (and
		 * next sync group will resume), as soon as we receive the last
		 * resync data block, and the last bit is cleared.
		 * until then resync "work" is "inactive" ...
		 */
		put_ldev(mdev);
		return 0;
	}

 requeue:
	mdev->rs_in_flight += (i << (BM_BLOCK_SHIFT - 9));
	mod_timer(&mdev->resync_timer, jiffies + SLEEP_TIME);
	put_ldev(mdev);
	return 0;
}

static int w_make_ov_request(struct drbd_work *w, int cancel)
{
	struct drbd_conf *mdev = w->mdev;
	int number, i, size;
	sector_t sector;
	const sector_t capacity = drbd_get_capacity(mdev->this_bdev);
	bool stop_sector_reached = false;

	if (unlikely(cancel))
		return 1;

	number = drbd_rs_number_requests(mdev);

	sector = mdev->ov_position;
	for (i = 0; i < number; i++) {
		if (sector >= capacity)
			return 1;

		/* We check for "finished" only in the reply path:
		 * w_e_end_ov_reply().
		 * We need to send at least one request out. */
		stop_sector_reached = i > 0
			&& verify_can_do_stop_sector(mdev)
			&& sector >= mdev->ov_stop_sector;
		if (stop_sector_reached)
			break;

		size = BM_BLOCK_SIZE;

		if (drbd_rs_should_slow_down(mdev, sector) ||
		    drbd_try_rs_begin_io(mdev, sector)) {
			mdev->ov_position = sector;
			goto requeue;
		}

		if (sector + (size>>9) > capacity)
			size = (capacity-sector)<<9;

		inc_rs_pending(mdev);
		if (drbd_send_ov_request(mdev, sector, size)) {
			dec_rs_pending(mdev);
			return 0;
		}
		sector += BM_SECT_PER_BIT;
	}
	mdev->ov_position = sector;

 requeue:
	mdev->rs_in_flight += (i << (BM_BLOCK_SHIFT - 9));
	if (i == 0 || !stop_sector_reached)
		mod_timer(&mdev->resync_timer, jiffies + SLEEP_TIME);
	return 1;
}

int w_ov_finished(struct drbd_work *w, int cancel)
{
	struct drbd_conf *mdev = w->mdev;
	kfree(w);
	ov_out_of_sync_print(mdev);
	drbd_resync_finished(mdev);

	return 0;
}

static int w_resync_finished(struct drbd_work *w, int cancel)
{
	struct drbd_conf *mdev = w->mdev;
	kfree(w);

	drbd_resync_finished(mdev);

	return 0;
}

static void ping_peer(struct drbd_conf *mdev)
{
	struct drbd_tconn *tconn = mdev->tconn;

	clear_bit(GOT_PING_ACK, &tconn->flags);
	request_ping(tconn);
	wait_event(tconn->ping_wait,
		   test_bit(GOT_PING_ACK, &tconn->flags) || mdev->state.conn < C_CONNECTED);
}

int drbd_resync_finished(struct drbd_conf *mdev)
{
	unsigned long db, dt, dbdt;
	unsigned long n_oos;
	union drbd_state os, ns;
	struct drbd_work *w;
	char *khelper_cmd = NULL;
	int verify_done = 0;

	/* Remove all elements from the resync LRU. Since future actions
	 * might set bits in the (main) bitmap, then the entries in the
	 * resync LRU would be wrong. */
	if (drbd_rs_del_all(mdev)) {
		/* In case this is not possible now, most probably because
		 * there are P_RS_DATA_REPLY Packets lingering on the worker's
		 * queue (or even the read operations for those packets
		 * is not finished by now).   Retry in 100ms. */

		schedule_timeout_interruptible(HZ / 10);
		w = kmalloc(sizeof(struct drbd_work), GFP_ATOMIC);
		if (w) {
			w->cb = w_resync_finished;
			w->mdev = mdev;
			drbd_queue_work(&mdev->tconn->sender_work, w);
			return 1;
		}
		dev_err(DEV, "Warn failed to drbd_rs_del_all() and to kmalloc(w).\n");
	}

	dt = (jiffies - mdev->rs_start - mdev->rs_paused) / HZ;
	if (dt <= 0)
		dt = 1;
	
	db = mdev->rs_total;
	/* adjust for verify start and stop sectors, respective reached position */
	if (mdev->state.conn == C_VERIFY_S || mdev->state.conn == C_VERIFY_T)
		db -= mdev->ov_left;

	dbdt = Bit2KB(db/dt);
	mdev->rs_paused /= HZ;

	if (!get_ldev(mdev))
		goto out;

	ping_peer(mdev);

	spin_lock_irq(&mdev->tconn->req_lock);
	os = drbd_read_state(mdev);

	verify_done = (os.conn == C_VERIFY_S || os.conn == C_VERIFY_T);

	/* This protects us against multiple calls (that can happen in the presence
	   of application IO), and against connectivity loss just before we arrive here. */
	if (os.conn <= C_CONNECTED)
		goto out_unlock;

	ns = os;
	ns.conn = C_CONNECTED;

	dev_info(DEV, "%s done (total %lu sec; paused %lu sec; %lu K/sec)\n",
	     verify_done ? "Online verify" : "Resync",
	     dt + mdev->rs_paused, mdev->rs_paused, dbdt);

	n_oos = drbd_bm_total_weight(mdev);

	if (os.conn == C_VERIFY_S || os.conn == C_VERIFY_T) {
		if (n_oos) {
			dev_alert(DEV, "Online verify found %lu %dk block out of sync!\n",
			      n_oos, Bit2KB(1));
			khelper_cmd = "out-of-sync";
		}
	} else {
		D_ASSERT((n_oos - mdev->rs_failed) == 0);

		if (os.conn == C_SYNC_TARGET || os.conn == C_PAUSED_SYNC_T)
			khelper_cmd = "after-resync-target";

		if (mdev->tconn->csums_tfm && mdev->rs_total) {
			const unsigned long s = mdev->rs_same_csum;
			const unsigned long t = mdev->rs_total;
			const int ratio =
				(t == 0)     ? 0 :
			(t < 100000) ? ((s*100)/t) : (s/(t/100));
			dev_info(DEV, "%u %% had equal checksums, eliminated: %luK; "
			     "transferred %luK total %luK\n",
			     ratio,
			     Bit2KB(mdev->rs_same_csum),
			     Bit2KB(mdev->rs_total - mdev->rs_same_csum),
			     Bit2KB(mdev->rs_total));
		}
	}

	if (mdev->rs_failed) {
		dev_info(DEV, "            %lu failed blocks\n", mdev->rs_failed);

		if (os.conn == C_SYNC_TARGET || os.conn == C_PAUSED_SYNC_T) {
			ns.disk = D_INCONSISTENT;
			ns.pdsk = D_UP_TO_DATE;
		} else {
			ns.disk = D_UP_TO_DATE;
			ns.pdsk = D_INCONSISTENT;
		}
	} else {
		ns.disk = D_UP_TO_DATE;
		ns.pdsk = D_UP_TO_DATE;

		if (os.conn == C_SYNC_TARGET || os.conn == C_PAUSED_SYNC_T) {
			if (mdev->p_uuid) {
				int i;
				for (i = UI_BITMAP ; i <= UI_HISTORY_END ; i++)
					_drbd_uuid_set(mdev, i, mdev->p_uuid[i]);
				drbd_uuid_set(mdev, UI_BITMAP, mdev->ldev->md.uuid[UI_CURRENT]);
				_drbd_uuid_set(mdev, UI_CURRENT, mdev->p_uuid[UI_CURRENT]);
			} else {
				dev_err(DEV, "mdev->p_uuid is NULL! BUG\n");
			}
		}

		if (!(os.conn == C_VERIFY_S || os.conn == C_VERIFY_T)) {
			/* for verify runs, we don't update uuids here,
			 * so there would be nothing to report. */
			drbd_uuid_set_bm(mdev, 0UL);
			drbd_print_uuids(mdev, "updated UUIDs");
			if (mdev->p_uuid) {
				/* Now the two UUID sets are equal, update what we
				 * know of the peer. */
				int i;
				for (i = UI_CURRENT ; i <= UI_HISTORY_END ; i++)
					mdev->p_uuid[i] = mdev->ldev->md.uuid[i];
			}
		}
	}

	_drbd_set_state(mdev, ns, CS_VERBOSE, NULL);
out_unlock:
	spin_unlock_irq(&mdev->tconn->req_lock);
	put_ldev(mdev);
out:
	mdev->rs_total  = 0;
	mdev->rs_failed = 0;
	mdev->rs_paused = 0;

	/* reset start sector, if we reached end of device */
	if (verify_done && mdev->ov_left == 0)
		mdev->ov_start_sector = 0;

	drbd_md_sync(mdev);

	if (khelper_cmd)
		drbd_khelper(mdev, khelper_cmd);

	return 1;
}

/* helper */
static void move_to_net_ee_or_free(struct drbd_conf *mdev, struct drbd_peer_request *peer_req)
{
	if (drbd_peer_req_has_active_page(peer_req)) {
		/* This might happen if sendpage() has not finished */
		int i = (peer_req->i.size + PAGE_SIZE -1) >> PAGE_SHIFT;
		atomic_add(i, &mdev->pp_in_use_by_net);
		atomic_sub(i, &mdev->pp_in_use);
		spin_lock_irq(&mdev->tconn->req_lock);
		list_add_tail(&peer_req->w.list, &mdev->net_ee);
		spin_unlock_irq(&mdev->tconn->req_lock);
		wake_up(&drbd_pp_wait);
	} else
		drbd_free_peer_req(mdev, peer_req);
}

/**
 * w_e_end_data_req() - Worker callback, to send a P_DATA_REPLY packet in response to a P_DATA_REQUEST
 * @mdev:	DRBD device.
 * @w:		work object.
 * @cancel:	The connection will be closed anyways
 */
int w_e_end_data_req(struct drbd_work *w, int cancel)
{
	struct drbd_peer_request *peer_req = container_of(w, struct drbd_peer_request, w);
	struct drbd_conf *mdev = w->mdev;
	int err;

	if (unlikely(cancel)) {
		drbd_free_peer_req(mdev, peer_req);
		dec_unacked(mdev);
		return 0;
	}

	if (likely((peer_req->flags & EE_WAS_ERROR) == 0)) {
		err = drbd_send_block(mdev, P_DATA_REPLY, peer_req);
	} else {
		if (__ratelimit(&drbd_ratelimit_state))
			dev_err(DEV, "Sending NegDReply. sector=%llus.\n",
			    (unsigned long long)peer_req->i.sector);

		err = drbd_send_ack(mdev, P_NEG_DREPLY, peer_req);
	}

	dec_unacked(mdev);

	move_to_net_ee_or_free(mdev, peer_req);

	if (unlikely(err))
		dev_err(DEV, "drbd_send_block() failed\n");
	return err;
}

/**
 * w_e_end_rsdata_req() - Worker callback to send a P_RS_DATA_REPLY packet in response to a P_RS_DATA_REQUEST
 * @mdev:	DRBD device.
 * @w:		work object.
 * @cancel:	The connection will be closed anyways
 */
int w_e_end_rsdata_req(struct drbd_work *w, int cancel)
{
	struct drbd_peer_request *peer_req = container_of(w, struct drbd_peer_request, w);
	struct drbd_conf *mdev = w->mdev;
	int err;

	if (unlikely(cancel)) {
		drbd_free_peer_req(mdev, peer_req);
		dec_unacked(mdev);
		return 0;
	}

	if (get_ldev_if_state(mdev, D_FAILED)) {
		drbd_rs_complete_io(mdev, peer_req->i.sector);
		put_ldev(mdev);
	}

	if (mdev->state.conn == C_AHEAD) {
		err = drbd_send_ack(mdev, P_RS_CANCEL, peer_req);
	} else if (likely((peer_req->flags & EE_WAS_ERROR) == 0)) {
		if (likely(mdev->state.pdsk >= D_INCONSISTENT)) {
			inc_rs_pending(mdev);
			err = drbd_send_block(mdev, P_RS_DATA_REPLY, peer_req);
		} else {
			if (__ratelimit(&drbd_ratelimit_state))
				dev_err(DEV, "Not sending RSDataReply, "
				    "partner DISKLESS!\n");
			err = 0;
		}
	} else {
		if (__ratelimit(&drbd_ratelimit_state))
			dev_err(DEV, "Sending NegRSDReply. sector %llus.\n",
			    (unsigned long long)peer_req->i.sector);

		err = drbd_send_ack(mdev, P_NEG_RS_DREPLY, peer_req);

		/* update resync data with failure */
		drbd_rs_failed_io(mdev, peer_req->i.sector, peer_req->i.size);
	}

	dec_unacked(mdev);

	move_to_net_ee_or_free(mdev, peer_req);

	if (unlikely(err))
		dev_err(DEV, "drbd_send_block() failed\n");
	return err;
}

int w_e_end_csum_rs_req(struct drbd_work *w, int cancel)
{
	struct drbd_peer_request *peer_req = container_of(w, struct drbd_peer_request, w);
	struct drbd_conf *mdev = w->mdev;
	struct digest_info *di;
	int digest_size;
	void *digest = NULL;
	int err, eq = 0;

	if (unlikely(cancel)) {
		drbd_free_peer_req(mdev, peer_req);
		dec_unacked(mdev);
		return 0;
	}

	if (get_ldev(mdev)) {
		drbd_rs_complete_io(mdev, peer_req->i.sector);
		put_ldev(mdev);
	}

	di = peer_req->digest;

	if (likely((peer_req->flags & EE_WAS_ERROR) == 0)) {
		/* quick hack to try to avoid a race against reconfiguration.
		 * a real fix would be much more involved,
		 * introducing more locking mechanisms */
		if (mdev->tconn->csums_tfm) {
			digest_size = crypto_hash_digestsize(mdev->tconn->csums_tfm);
			D_ASSERT(digest_size == di->digest_size);
			digest = kmalloc(digest_size, GFP_NOIO);
		}
		if (digest) {
			drbd_csum_ee(mdev, mdev->tconn->csums_tfm, peer_req, digest);
			eq = !memcmp(digest, di->digest, digest_size);
			kfree(digest);
		}

		if (eq) {
			drbd_set_in_sync(mdev, peer_req->i.sector, peer_req->i.size);
			/* rs_same_csums unit is BM_BLOCK_SIZE */
			mdev->rs_same_csum += peer_req->i.size >> BM_BLOCK_SHIFT;
			err = drbd_send_ack(mdev, P_RS_IS_IN_SYNC, peer_req);
		} else {
			inc_rs_pending(mdev);
			peer_req->block_id = ID_SYNCER; /* By setting block_id, digest pointer becomes invalid! */
			peer_req->flags &= ~EE_HAS_DIGEST; /* This peer request no longer has a digest pointer */
			kfree(di);
			err = drbd_send_block(mdev, P_RS_DATA_REPLY, peer_req);
		}
	} else {
		err = drbd_send_ack(mdev, P_NEG_RS_DREPLY, peer_req);
		if (__ratelimit(&drbd_ratelimit_state))
			dev_err(DEV, "Sending NegDReply. I guess it gets messy.\n");
	}

	dec_unacked(mdev);
	move_to_net_ee_or_free(mdev, peer_req);

	if (unlikely(err))
		dev_err(DEV, "drbd_send_block/ack() failed\n");
	return err;
}

int w_e_end_ov_req(struct drbd_work *w, int cancel)
{
	struct drbd_peer_request *peer_req = container_of(w, struct drbd_peer_request, w);
	struct drbd_conf *mdev = w->mdev;
	sector_t sector = peer_req->i.sector;
	unsigned int size = peer_req->i.size;
	int digest_size;
	void *digest;
	int err = 0;

	if (unlikely(cancel))
		goto out;

	digest_size = crypto_hash_digestsize(mdev->tconn->verify_tfm);
	digest = kmalloc(digest_size, GFP_NOIO);
	if (!digest) {
		err = 1;	/* terminate the connection in case the allocation failed */
		goto out;
	}

	if (likely(!(peer_req->flags & EE_WAS_ERROR)))
		drbd_csum_ee(mdev, mdev->tconn->verify_tfm, peer_req, digest);
	else
		memset(digest, 0, digest_size);

	/* Free e and pages before send.
	 * In case we block on congestion, we could otherwise run into
	 * some distributed deadlock, if the other side blocks on
	 * congestion as well, because our receiver blocks in
	 * drbd_alloc_pages due to pp_in_use > max_buffers. */
	drbd_free_peer_req(mdev, peer_req);
	peer_req = NULL;
	inc_rs_pending(mdev);
	err = drbd_send_drequest_csum(mdev, sector, size, digest, digest_size, P_OV_REPLY);
	if (err)
		dec_rs_pending(mdev);
	kfree(digest);

out:
	if (peer_req)
		drbd_free_peer_req(mdev, peer_req);
	dec_unacked(mdev);
	return err;
}

void drbd_ov_out_of_sync_found(struct drbd_conf *mdev, sector_t sector, int size)
{
	if (mdev->ov_last_oos_start + mdev->ov_last_oos_size == sector) {
		mdev->ov_last_oos_size += size>>9;
	} else {
		mdev->ov_last_oos_start = sector;
		mdev->ov_last_oos_size = size>>9;
	}
	drbd_set_out_of_sync(mdev, sector, size);
}

int w_e_end_ov_reply(struct drbd_work *w, int cancel)
{
	struct drbd_peer_request *peer_req = container_of(w, struct drbd_peer_request, w);
	struct drbd_conf *mdev = w->mdev;
	struct digest_info *di;
	void *digest;
	sector_t sector = peer_req->i.sector;
	unsigned int size = peer_req->i.size;
	int digest_size;
	int err, eq = 0;
	bool stop_sector_reached = false;

	if (unlikely(cancel)) {
		drbd_free_peer_req(mdev, peer_req);
		dec_unacked(mdev);
		return 0;
	}

	/* after "cancel", because after drbd_disconnect/drbd_rs_cancel_all
	 * the resync lru has been cleaned up already */
	if (get_ldev(mdev)) {
		drbd_rs_complete_io(mdev, peer_req->i.sector);
		put_ldev(mdev);
	}

	di = peer_req->digest;

	if (likely((peer_req->flags & EE_WAS_ERROR) == 0)) {
		digest_size = crypto_hash_digestsize(mdev->tconn->verify_tfm);
		digest = kmalloc(digest_size, GFP_NOIO);
		if (digest) {
			drbd_csum_ee(mdev, mdev->tconn->verify_tfm, peer_req, digest);

			D_ASSERT(digest_size == di->digest_size);
			eq = !memcmp(digest, di->digest, digest_size);
			kfree(digest);
		}
	}

	/* Free peer_req and pages before send.
	 * In case we block on congestion, we could otherwise run into
	 * some distributed deadlock, if the other side blocks on
	 * congestion as well, because our receiver blocks in
	 * drbd_alloc_pages due to pp_in_use > max_buffers. */
	drbd_free_peer_req(mdev, peer_req);
	if (!eq)
		drbd_ov_out_of_sync_found(mdev, sector, size);
	else
		ov_out_of_sync_print(mdev);

	err = drbd_send_ack_ex(mdev, P_OV_RESULT, sector, size,
			       eq ? ID_IN_SYNC : ID_OUT_OF_SYNC);

	dec_unacked(mdev);

	--mdev->ov_left;

	/* let's advance progress step marks only for every other megabyte */
	if ((mdev->ov_left & 0x200) == 0x200)
		drbd_advance_rs_marks(mdev, mdev->ov_left);

	stop_sector_reached = verify_can_do_stop_sector(mdev) &&
		(sector + (size>>9)) >= mdev->ov_stop_sector;

	if (mdev->ov_left == 0 || stop_sector_reached) {
		ov_out_of_sync_print(mdev);
		drbd_resync_finished(mdev);
	}

	return err;
}

int w_prev_work_done(struct drbd_work *w, int cancel)
{
	struct drbd_wq_barrier *b = container_of(w, struct drbd_wq_barrier, w);

	complete(&b->done);
	return 0;
}

/* FIXME
 * We need to track the number of pending barrier acks,
 * and to be able to wait for them.
 * See also comment in drbd_adm_attach before drbd_suspend_io.
 */
int drbd_send_barrier(struct drbd_tconn *tconn)
{
	struct p_barrier *p;
	struct drbd_socket *sock;

	sock = &tconn->data;
	p = conn_prepare_command(tconn, sock);
	if (!p)
		return -EIO;
	p->barrier = tconn->send.current_epoch_nr;
	p->pad = 0;
	tconn->send.current_epoch_writes = 0;

	return conn_send_command(tconn, sock, P_BARRIER, sizeof(*p), NULL, 0);
}

int w_send_write_hint(struct drbd_work *w, int cancel)
{
	struct drbd_conf *mdev = w->mdev;
	struct drbd_socket *sock;

	if (cancel)
		return 0;
	sock = &mdev->tconn->data;
	if (!drbd_prepare_command(mdev, sock))
		return -EIO;
	return drbd_send_command(mdev, sock, P_UNPLUG_REMOTE, 0, NULL, 0);
}

static void re_init_if_first_write(struct drbd_tconn *tconn, unsigned int epoch)
{
	if (!tconn->send.seen_any_write_yet) {
		tconn->send.seen_any_write_yet = true;
		tconn->send.current_epoch_nr = epoch;
		tconn->send.current_epoch_writes = 0;
	}
}

static void maybe_send_barrier(struct drbd_tconn *tconn, unsigned int epoch)
{
	/* re-init if first write on this connection */
	if (!tconn->send.seen_any_write_yet)
		return;
	if (tconn->send.current_epoch_nr != epoch) {
		if (tconn->send.current_epoch_writes)
			drbd_send_barrier(tconn);
		tconn->send.current_epoch_nr = epoch;
	}
}

int w_send_out_of_sync(struct drbd_work *w, int cancel)
{
	struct drbd_request *req = container_of(w, struct drbd_request, w);
	struct drbd_conf *mdev = w->mdev;
	struct drbd_tconn *tconn = mdev->tconn;
	int err;

	if (unlikely(cancel)) {
		req_mod(req, SEND_CANCELED);
		return 0;
	}

	/* this time, no tconn->send.current_epoch_writes++;
	 * If it was sent, it was the closing barrier for the last
	 * replicated epoch, before we went into AHEAD mode.
	 * No more barriers will be sent, until we leave AHEAD mode again. */
	maybe_send_barrier(tconn, req->epoch);

	err = drbd_send_out_of_sync(mdev, req);
	req_mod(req, OOS_HANDED_TO_NETWORK);

	return err;
}

/**
 * w_send_dblock() - Worker callback to send a P_DATA packet in order to mirror a write request
 * @mdev:	DRBD device.
 * @w:		work object.
 * @cancel:	The connection will be closed anyways
 */
int w_send_dblock(struct drbd_work *w, int cancel)
{
	struct drbd_request *req = container_of(w, struct drbd_request, w);
	struct drbd_conf *mdev = w->mdev;
	struct drbd_tconn *tconn = mdev->tconn;
	int err;

	if (unlikely(cancel)) {
		req_mod(req, SEND_CANCELED);
		return 0;
	}

	re_init_if_first_write(tconn, req->epoch);
	maybe_send_barrier(tconn, req->epoch);
	tconn->send.current_epoch_writes++;

	err = drbd_send_dblock(mdev, req);
	req_mod(req, err ? SEND_FAILED : HANDED_OVER_TO_NETWORK);

	return err;
}

/**
 * w_send_read_req() - Worker callback to send a read request (P_DATA_REQUEST) packet
 * @mdev:	DRBD device.
 * @w:		work object.
 * @cancel:	The connection will be closed anyways
 */
int w_send_read_req(struct drbd_work *w, int cancel)
{
	struct drbd_request *req = container_of(w, struct drbd_request, w);
	struct drbd_conf *mdev = w->mdev;
	struct drbd_tconn *tconn = mdev->tconn;
	int err;

	if (unlikely(cancel)) {
		req_mod(req, SEND_CANCELED);
		return 0;
	}

	/* Even read requests may close a write epoch,
	 * if there was any yet. */
	maybe_send_barrier(tconn, req->epoch);

	err = drbd_send_drequest(mdev, P_DATA_REQUEST, req->i.sector, req->i.size,
				 (unsigned long)req);

	req_mod(req, err ? SEND_FAILED : HANDED_OVER_TO_NETWORK);

	return err;
}

int w_restart_disk_io(struct drbd_work *w, int cancel)
{
	struct drbd_request *req = container_of(w, struct drbd_request, w);
	struct drbd_conf *mdev = w->mdev;

	if (bio_data_dir(req->master_bio) == WRITE && req->rq_state & RQ_IN_ACT_LOG)
		drbd_al_begin_io(mdev, &req->i);

	drbd_req_make_private_bio(req, req->master_bio);
	req->private_bio->bi_bdev = mdev->ldev->backing_bdev;
	generic_make_request(req->private_bio);

	return 0;
}

static int _drbd_may_sync_now(struct drbd_conf *mdev)
{
	struct drbd_conf *odev = mdev;
	int resync_after;

	while (1) {
		if (!odev->ldev)
			return 1;
		rcu_read_lock();
		resync_after = rcu_dereference(odev->ldev->disk_conf)->resync_after;
		rcu_read_unlock();
		if (resync_after == -1)
			return 1;
		odev = minor_to_mdev(resync_after);
		if (!expect(odev))
			return 1;
		if ((odev->state.conn >= C_SYNC_SOURCE &&
		     odev->state.conn <= C_PAUSED_SYNC_T) ||
		    odev->state.aftr_isp || odev->state.peer_isp ||
		    odev->state.user_isp)
			return 0;
	}
}

/**
 * _drbd_pause_after() - Pause resync on all devices that may not resync now
 * @mdev:	DRBD device.
 *
 * Called from process context only (admin command and after_state_ch).
 */
static int _drbd_pause_after(struct drbd_conf *mdev)
{
	struct drbd_conf *odev;
	int i, rv = 0;

	rcu_read_lock();
	idr_for_each_entry(&minors, odev, i) {
		if (odev->state.conn == C_STANDALONE && odev->state.disk == D_DISKLESS)
			continue;
		if (!_drbd_may_sync_now(odev))
			rv |= (__drbd_set_state(_NS(odev, aftr_isp, 1), CS_HARD, NULL)
			       != SS_NOTHING_TO_DO);
	}
	rcu_read_unlock();

	return rv;
}

/**
 * _drbd_resume_next() - Resume resync on all devices that may resync now
 * @mdev:	DRBD device.
 *
 * Called from process context only (admin command and worker).
 */
static int _drbd_resume_next(struct drbd_conf *mdev)
{
	struct drbd_conf *odev;
	int i, rv = 0;

	rcu_read_lock();
	idr_for_each_entry(&minors, odev, i) {
		if (odev->state.conn == C_STANDALONE && odev->state.disk == D_DISKLESS)
			continue;
		if (odev->state.aftr_isp) {
			if (_drbd_may_sync_now(odev))
				rv |= (__drbd_set_state(_NS(odev, aftr_isp, 0),
							CS_HARD, NULL)
				       != SS_NOTHING_TO_DO) ;
		}
	}
	rcu_read_unlock();
	return rv;
}

void resume_next_sg(struct drbd_conf *mdev)
{
	write_lock_irq(&global_state_lock);
	_drbd_resume_next(mdev);
	write_unlock_irq(&global_state_lock);
}

void suspend_other_sg(struct drbd_conf *mdev)
{
	write_lock_irq(&global_state_lock);
	_drbd_pause_after(mdev);
	write_unlock_irq(&global_state_lock);
}

/* caller must hold global_state_lock */
enum drbd_ret_code drbd_resync_after_valid(struct drbd_conf *mdev, int o_minor)
{
	struct drbd_conf *odev;
	int resync_after;

	if (o_minor == -1)
		return NO_ERROR;
	if (o_minor < -1 || minor_to_mdev(o_minor) == NULL)
		return ERR_RESYNC_AFTER;

	/* check for loops */
	odev = minor_to_mdev(o_minor);
	while (1) {
		if (odev == mdev)
			return ERR_RESYNC_AFTER_CYCLE;

		rcu_read_lock();
		resync_after = rcu_dereference(odev->ldev->disk_conf)->resync_after;
		rcu_read_unlock();
		/* dependency chain ends here, no cycles. */
		if (resync_after == -1)
			return NO_ERROR;

		/* follow the dependency chain */
		odev = minor_to_mdev(resync_after);
	}
}

/* caller must hold global_state_lock */
void drbd_resync_after_changed(struct drbd_conf *mdev)
{
	int changes;

	do {
		changes  = _drbd_pause_after(mdev);
		changes |= _drbd_resume_next(mdev);
	} while (changes);
}

void drbd_rs_controller_reset(struct drbd_conf *mdev)
{
	struct fifo_buffer *plan;

	atomic_set(&mdev->rs_sect_in, 0);
	atomic_set(&mdev->rs_sect_ev, 0);
	mdev->rs_in_flight = 0;

	/* Updating the RCU protected object in place is necessary since
	   this function gets called from atomic context.
	   It is valid since all other updates also lead to an completely
	   empty fifo */
	rcu_read_lock();
	plan = rcu_dereference(mdev->rs_plan_s);
	plan->total = 0;
	fifo_set(plan, 0);
	rcu_read_unlock();
}

void start_resync_timer_fn(unsigned long data)
{
	struct drbd_conf *mdev = (struct drbd_conf *) data;

	drbd_queue_work(&mdev->tconn->sender_work, &mdev->start_resync_work);
}

int w_start_resync(struct drbd_work *w, int cancel)
{
	struct drbd_conf *mdev = w->mdev;

	if (atomic_read(&mdev->unacked_cnt) || atomic_read(&mdev->rs_pending_cnt)) {
		dev_warn(DEV, "w_start_resync later...\n");
		mdev->start_resync_timer.expires = jiffies + HZ/10;
		add_timer(&mdev->start_resync_timer);
		return 0;
	}

	drbd_start_resync(mdev, C_SYNC_SOURCE);
	clear_bit(AHEAD_TO_SYNC_SOURCE, &mdev->flags);
	return 0;
}

/**
 * drbd_start_resync() - Start the resync process
 * @mdev:	DRBD device.
 * @side:	Either C_SYNC_SOURCE or C_SYNC_TARGET
 *
 * This function might bring you directly into one of the
 * C_PAUSED_SYNC_* states.
 */
void drbd_start_resync(struct drbd_conf *mdev, enum drbd_conns side)
{
	union drbd_state ns;
	int r;

	if (mdev->state.conn >= C_SYNC_SOURCE && mdev->state.conn < C_AHEAD) {
		dev_err(DEV, "Resync already running!\n");
		return;
	}

	if (!test_bit(B_RS_H_DONE, &mdev->flags)) {
		if (side == C_SYNC_TARGET) {
			/* Since application IO was locked out during C_WF_BITMAP_T and
			   C_WF_SYNC_UUID we are still unmodified. Before going to C_SYNC_TARGET
			   we check that we might make the data inconsistent. */
			r = drbd_khelper(mdev, "before-resync-target");
			r = (r >> 8) & 0xff;
			if (r > 0) {
				dev_info(DEV, "before-resync-target handler returned %d, "
					 "dropping connection.\n", r);
				conn_request_state(mdev->tconn, NS(conn, C_DISCONNECTING), CS_HARD);
				return;
			}
		} else /* C_SYNC_SOURCE */ {
			r = drbd_khelper(mdev, "before-resync-source");
			r = (r >> 8) & 0xff;
			if (r > 0) {
				if (r == 3) {
					dev_info(DEV, "before-resync-source handler returned %d, "
						 "ignoring. Old userland tools?", r);
				} else {
					dev_info(DEV, "before-resync-source handler returned %d, "
						 "dropping connection.\n", r);
					conn_request_state(mdev->tconn, NS(conn, C_DISCONNECTING), CS_HARD);
					return;
				}
			}
		}
	}

	if (current == mdev->tconn->worker.task) {
		/* The worker should not sleep waiting for state_mutex,
		   that can take long */
		if (!mutex_trylock(mdev->state_mutex)) {
			set_bit(B_RS_H_DONE, &mdev->flags);
			mdev->start_resync_timer.expires = jiffies + HZ/5;
			add_timer(&mdev->start_resync_timer);
			return;
		}
	} else {
		mutex_lock(mdev->state_mutex);
	}
	clear_bit(B_RS_H_DONE, &mdev->flags);

	write_lock_irq(&global_state_lock);
	if (!get_ldev_if_state(mdev, D_NEGOTIATING)) {
		write_unlock_irq(&global_state_lock);
		mutex_unlock(mdev->state_mutex);
		return;
	}

	ns = drbd_read_state(mdev);

	ns.aftr_isp = !_drbd_may_sync_now(mdev);

	ns.conn = side;

	if (side == C_SYNC_TARGET)
		ns.disk = D_INCONSISTENT;
	else /* side == C_SYNC_SOURCE */
		ns.pdsk = D_INCONSISTENT;

	r = __drbd_set_state(mdev, ns, CS_VERBOSE, NULL);
	ns = drbd_read_state(mdev);

	if (ns.conn < C_CONNECTED)
		r = SS_UNKNOWN_ERROR;

	if (r == SS_SUCCESS) {
		unsigned long tw = drbd_bm_total_weight(mdev);
		unsigned long now = jiffies;
		int i;

		mdev->rs_failed    = 0;
		mdev->rs_paused    = 0;
		mdev->rs_same_csum = 0;
		mdev->rs_last_events = 0;
		mdev->rs_last_sect_ev = 0;
		mdev->rs_total     = tw;
		mdev->rs_start     = now;
		for (i = 0; i < DRBD_SYNC_MARKS; i++) {
			mdev->rs_mark_left[i] = tw;
			mdev->rs_mark_time[i] = now;
		}
		_drbd_pause_after(mdev);
	}
	write_unlock_irq(&global_state_lock);

	if (r == SS_SUCCESS) {
		dev_info(DEV, "Began resync as %s (will sync %lu KB [%lu bits set]).\n",
		     drbd_conn_str(ns.conn),
		     (unsigned long) mdev->rs_total << (BM_BLOCK_SHIFT-10),
		     (unsigned long) mdev->rs_total);
		if (side == C_SYNC_TARGET)
			mdev->bm_resync_fo = 0;

		/* Since protocol 96, we must serialize drbd_gen_and_send_sync_uuid
		 * with w_send_oos, or the sync target will get confused as to
		 * how much bits to resync.  We cannot do that always, because for an
		 * empty resync and protocol < 95, we need to do it here, as we call
		 * drbd_resync_finished from here in that case.
		 * We drbd_gen_and_send_sync_uuid here for protocol < 96,
		 * and from after_state_ch otherwise. */
		if (side == C_SYNC_SOURCE && mdev->tconn->agreed_pro_version < 96)
			drbd_gen_and_send_sync_uuid(mdev);

		if (mdev->tconn->agreed_pro_version < 95 && mdev->rs_total == 0) {
			/* This still has a race (about when exactly the peers
			 * detect connection loss) that can lead to a full sync
			 * on next handshake. In 8.3.9 we fixed this with explicit
			 * resync-finished notifications, but the fix
			 * introduces a protocol change.  Sleeping for some
			 * time longer than the ping interval + timeout on the
			 * SyncSource, to give the SyncTarget the chance to
			 * detect connection loss, then waiting for a ping
			 * response (implicit in drbd_resync_finished) reduces
			 * the race considerably, but does not solve it. */
			if (side == C_SYNC_SOURCE) {
				struct net_conf *nc;
				int timeo;

				rcu_read_lock();
				nc = rcu_dereference(mdev->tconn->net_conf);
				timeo = nc->ping_int * HZ + nc->ping_timeo * HZ / 9;
				rcu_read_unlock();
				schedule_timeout_interruptible(timeo);
			}
			drbd_resync_finished(mdev);
		}

		drbd_rs_controller_reset(mdev);
		/* ns.conn may already be != mdev->state.conn,
		 * we may have been paused in between, or become paused until
		 * the timer triggers.
		 * No matter, that is handled in resync_timer_fn() */
		if (ns.conn == C_SYNC_TARGET)
			mod_timer(&mdev->resync_timer, jiffies);

		drbd_md_sync(mdev);
	}
	put_ldev(mdev);
	mutex_unlock(mdev->state_mutex);
}

/* If the resource already closed the current epoch, but we did not
 * (because we have not yet seen new requests), we should send the
 * corresponding barrier now.  Must be checked within the same spinlock
 * that is used to check for new requests. */
bool need_to_send_barrier(struct drbd_tconn *connection)
{
	if (!connection->send.seen_any_write_yet)
		return false;

	/* Skip barriers that do not contain any writes.
	 * This may happen during AHEAD mode. */
	if (!connection->send.current_epoch_writes)
		return false;

	/* ->req_lock is held when requests are queued on
	 * connection->sender_work, and put into ->transfer_log.
	 * It is also held when ->current_tle_nr is increased.
	 * So either there are already new requests queued,
	 * and corresponding barriers will be send there.
	 * Or nothing new is queued yet, so the difference will be 1.
	 */
	if (atomic_read(&connection->current_tle_nr) !=
	    connection->send.current_epoch_nr + 1)
		return false;

	return true;
}

bool dequeue_work_batch(struct drbd_work_queue *queue, struct list_head *work_list)
{
	spin_lock_irq(&queue->q_lock);
	list_splice_init(&queue->q, work_list);
	spin_unlock_irq(&queue->q_lock);
	return !list_empty(work_list);
}

bool dequeue_work_item(struct drbd_work_queue *queue, struct list_head *work_list)
{
	spin_lock_irq(&queue->q_lock);
	if (!list_empty(&queue->q))
		list_move(queue->q.next, work_list);
	spin_unlock_irq(&queue->q_lock);
	return !list_empty(work_list);
}

void wait_for_work(struct drbd_tconn *connection, struct list_head *work_list)
{
	DEFINE_WAIT(wait);
	struct net_conf *nc;
	int uncork, cork;

	dequeue_work_item(&connection->sender_work, work_list);
	if (!list_empty(work_list))
		return;

	/* Still nothing to do?
	 * Maybe we still need to close the current epoch,
	 * even if no new requests are queued yet.
	 *
	 * Also, poke TCP, just in case.
	 * Then wait for new work (or signal). */
	rcu_read_lock();
	nc = rcu_dereference(connection->net_conf);
	uncork = nc ? nc->tcp_cork : 0;
	rcu_read_unlock();
	if (uncork) {
		mutex_lock(&connection->data.mutex);
		if (connection->data.socket)
			drbd_tcp_uncork(connection->data.socket);
		mutex_unlock(&connection->data.mutex);
	}

	for (;;) {
		int send_barrier;
		prepare_to_wait(&connection->sender_work.q_wait, &wait, TASK_INTERRUPTIBLE);
		spin_lock_irq(&connection->req_lock);
		spin_lock(&connection->sender_work.q_lock);	/* FIXME get rid of this one? */
		/* dequeue single item only,
		 * we still use drbd_queue_work_front() in some places */
		if (!list_empty(&connection->sender_work.q))
			list_move(connection->sender_work.q.next, work_list);
		spin_unlock(&connection->sender_work.q_lock);	/* FIXME get rid of this one? */
		if (!list_empty(work_list) || signal_pending(current)) {
			spin_unlock_irq(&connection->req_lock);
			break;
		}
		send_barrier = need_to_send_barrier(connection);
		spin_unlock_irq(&connection->req_lock);
		if (send_barrier) {
			drbd_send_barrier(connection);
			connection->send.current_epoch_nr++;
		}
		schedule();
		/* may be woken up for other things but new work, too,
		 * e.g. if the current epoch got closed.
		 * In which case we send the barrier above. */
	}
	finish_wait(&connection->sender_work.q_wait, &wait);

	/* someone may have changed the config while we have been waiting above. */
	rcu_read_lock();
	nc = rcu_dereference(connection->net_conf);
	cork = nc ? nc->tcp_cork : 0;
	rcu_read_unlock();
	mutex_lock(&connection->data.mutex);
	if (connection->data.socket) {
		if (cork)
			drbd_tcp_cork(connection->data.socket);
		else if (!uncork)
			drbd_tcp_uncork(connection->data.socket);
	}
	mutex_unlock(&connection->data.mutex);
}

int drbd_worker(struct drbd_thread *thi)
{
	struct drbd_tconn *tconn = thi->tconn;
	struct drbd_work *w = NULL;
	struct drbd_conf *mdev;
	LIST_HEAD(work_list);
	int vnr;

	while (get_t_state(thi) == RUNNING) {
		drbd_thread_current_set_cpu(thi);

		/* as long as we use drbd_queue_work_front(),
		 * we may only dequeue single work items here, not batches. */
		if (list_empty(&work_list))
			wait_for_work(tconn, &work_list);

		if (signal_pending(current)) {
			flush_signals(current);
			if (get_t_state(thi) == RUNNING) {
				conn_warn(tconn, "Worker got an unexpected signal\n");
				continue;
			}
			break;
		}

		if (get_t_state(thi) != RUNNING)
			break;

		while (!list_empty(&work_list)) {
			w = list_first_entry(&work_list, struct drbd_work, list);
			list_del_init(&w->list);
			if (w->cb(w, tconn->cstate < C_WF_REPORT_PARAMS) == 0)
				continue;
			if (tconn->cstate >= C_WF_REPORT_PARAMS)
				conn_request_state(tconn, NS(conn, C_NETWORK_FAILURE), CS_HARD);
		}
	}

	do {
		while (!list_empty(&work_list)) {
			w = list_first_entry(&work_list, struct drbd_work, list);
			list_del_init(&w->list);
			w->cb(w, 1);
		}
		dequeue_work_batch(&tconn->sender_work, &work_list);
	} while (!list_empty(&work_list));

	rcu_read_lock();
	idr_for_each_entry(&tconn->volumes, mdev, vnr) {
		D_ASSERT(mdev->state.disk == D_DISKLESS && mdev->state.conn == C_STANDALONE);
		kref_get(&mdev->kref);
		rcu_read_unlock();
		drbd_mdev_cleanup(mdev);
		kref_put(&mdev->kref, &drbd_minor_destroy);
		rcu_read_lock();
	}
	rcu_read_unlock();

	return 0;
}