aboutsummaryrefslogtreecommitdiff
path: root/kernel/trace/blktrace.c
blob: e82cb9e930cc2e328830afe163e89af032c77f41 (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
/*
 * Copyright (C) 2006 Jens Axboe <axboe@kernel.dk>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program 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 this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 */
#include <linux/kernel.h>
#include <linux/blkdev.h>
#include <linux/blktrace_api.h>
#include <linux/percpu.h>
#include <linux/init.h>
#include <linux/mutex.h>
#include <linux/debugfs.h>
#include <linux/time.h>
#include <trace/block.h>
#include <linux/uaccess.h>
#include "trace_output.h"

static unsigned int blktrace_seq __read_mostly = 1;

static struct trace_array *blk_tr;
static int __read_mostly  blk_tracer_enabled;

/* Select an alternative, minimalistic output than the original one */
#define TRACE_BLK_OPT_CLASSIC 	0x1

static struct tracer_opt blk_tracer_opts[] = {
	/* Default disable the minimalistic output */
	{ TRACER_OPT(blk_classic, TRACE_BLK_OPT_CLASSIC) },
	{ }
};

static struct tracer_flags blk_tracer_flags = {
	.val  = 0,
	.opts = blk_tracer_opts,
};

/* Global reference count of probes */
static DEFINE_MUTEX(blk_probe_mutex);
static atomic_t blk_probes_ref = ATOMIC_INIT(0);

static int blk_register_tracepoints(void);
static void blk_unregister_tracepoints(void);

/*
 * Send out a notify message.
 */
static void trace_note(struct blk_trace *bt, pid_t pid, int action,
		       const void *data, size_t len)
{
	struct blk_io_trace *t;

	if (!bt->rchan)
		return;

	t = relay_reserve(bt->rchan, sizeof(*t) + len);
	if (t) {
		const int cpu = smp_processor_id();

		t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
		t->time = ktime_to_ns(ktime_get());
		t->device = bt->dev;
		t->action = action;
		t->pid = pid;
		t->cpu = cpu;
		t->pdu_len = len;
		memcpy((void *) t + sizeof(*t), data, len);
	}
}

/*
 * Send out a notify for this process, if we haven't done so since a trace
 * started
 */
static void trace_note_tsk(struct blk_trace *bt, struct task_struct *tsk)
{
	tsk->btrace_seq = blktrace_seq;
	trace_note(bt, tsk->pid, BLK_TN_PROCESS, tsk->comm, sizeof(tsk->comm));
}

static void trace_note_time(struct blk_trace *bt)
{
	struct timespec now;
	unsigned long flags;
	u32 words[2];

	getnstimeofday(&now);
	words[0] = now.tv_sec;
	words[1] = now.tv_nsec;

	local_irq_save(flags);
	trace_note(bt, 0, BLK_TN_TIMESTAMP, words, sizeof(words));
	local_irq_restore(flags);
}

void __trace_note_message(struct blk_trace *bt, const char *fmt, ...)
{
	int n;
	va_list args;
	unsigned long flags;
	char *buf;

	if (blk_tr) {
		va_start(args, fmt);
		ftrace_vprintk(fmt, args);
		va_end(args);
		return;
	}

	if (!bt->msg_data)
		return;

	local_irq_save(flags);
	buf = per_cpu_ptr(bt->msg_data, smp_processor_id());
	va_start(args, fmt);
	n = vscnprintf(buf, BLK_TN_MAX_MSG, fmt, args);
	va_end(args);

	trace_note(bt, 0, BLK_TN_MESSAGE, buf, n);
	local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(__trace_note_message);

static int act_log_check(struct blk_trace *bt, u32 what, sector_t sector,
			 pid_t pid)
{
	if (((bt->act_mask << BLK_TC_SHIFT) & what) == 0)
		return 1;
	if (sector < bt->start_lba || sector > bt->end_lba)
		return 1;
	if (bt->pid && pid != bt->pid)
		return 1;

	return 0;
}

/*
 * Data direction bit lookup
 */
static u32 ddir_act[2] __read_mostly = { BLK_TC_ACT(BLK_TC_READ),
					 BLK_TC_ACT(BLK_TC_WRITE) };

/* The ilog2() calls fall out because they're constant */
#define MASK_TC_BIT(rw, __name) ((rw & (1 << BIO_RW_ ## __name)) << \
	  (ilog2(BLK_TC_ ## __name) + BLK_TC_SHIFT - BIO_RW_ ## __name))

/*
 * The worker for the various blk_add_trace*() types. Fills out a
 * blk_io_trace structure and places it in a per-cpu subbuffer.
 */
static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
		     int rw, u32 what, int error, int pdu_len, void *pdu_data)
{
	struct task_struct *tsk = current;
	struct ring_buffer_event *event = NULL;
	struct blk_io_trace *t;
	unsigned long flags = 0;
	unsigned long *sequence;
	pid_t pid;
	int cpu, pc = 0;

	if (unlikely(bt->trace_state != Blktrace_running ||
		     !blk_tracer_enabled))
		return;

	what |= ddir_act[rw & WRITE];
	what |= MASK_TC_BIT(rw, BARRIER);
	what |= MASK_TC_BIT(rw, SYNCIO);
	what |= MASK_TC_BIT(rw, AHEAD);
	what |= MASK_TC_BIT(rw, META);
	what |= MASK_TC_BIT(rw, DISCARD);

	pid = tsk->pid;
	if (unlikely(act_log_check(bt, what, sector, pid)))
		return;
	cpu = raw_smp_processor_id();

	if (blk_tr) {
		tracing_record_cmdline(current);

		pc = preempt_count();
		event = trace_buffer_lock_reserve(blk_tr, TRACE_BLK,
						  sizeof(*t) + pdu_len,
						  0, pc);
		if (!event)
			return;
		t = ring_buffer_event_data(event);
		goto record_it;
	}

	/*
	 * A word about the locking here - we disable interrupts to reserve
	 * some space in the relay per-cpu buffer, to prevent an irq
	 * from coming in and stepping on our toes.
	 */
	local_irq_save(flags);

	if (unlikely(tsk->btrace_seq != blktrace_seq))
		trace_note_tsk(bt, tsk);

	t = relay_reserve(bt->rchan, sizeof(*t) + pdu_len);
	if (t) {
		sequence = per_cpu_ptr(bt->sequence, cpu);

		t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
		t->sequence = ++(*sequence);
		t->time = ktime_to_ns(ktime_get());
record_it:
		/*
		 * These two are not needed in ftrace as they are in the
		 * generic trace_entry, filled by tracing_generic_entry_update,
		 * but for the trace_event->bin() synthesizer benefit we do it
		 * here too.
		 */
		t->cpu = cpu;
		t->pid = pid;

		t->sector = sector;
		t->bytes = bytes;
		t->action = what;
		t->device = bt->dev;
		t->error = error;
		t->pdu_len = pdu_len;

		if (pdu_len)
			memcpy((void *) t + sizeof(*t), pdu_data, pdu_len);

		if (blk_tr) {
			trace_buffer_unlock_commit(blk_tr, event, 0, pc);
			return;
		}
	}

	local_irq_restore(flags);
}

static struct dentry *blk_tree_root;
static DEFINE_MUTEX(blk_tree_mutex);

static void blk_trace_cleanup(struct blk_trace *bt)
{
	debugfs_remove(bt->msg_file);
	debugfs_remove(bt->dropped_file);
	relay_close(bt->rchan);
	free_percpu(bt->sequence);
	free_percpu(bt->msg_data);
	kfree(bt);
	mutex_lock(&blk_probe_mutex);
	if (atomic_dec_and_test(&blk_probes_ref))
		blk_unregister_tracepoints();
	mutex_unlock(&blk_probe_mutex);
}

int blk_trace_remove(struct request_queue *q)
{
	struct blk_trace *bt;

	bt = xchg(&q->blk_trace, NULL);
	if (!bt)
		return -EINVAL;

	if (bt->trace_state == Blktrace_setup ||
	    bt->trace_state == Blktrace_stopped)
		blk_trace_cleanup(bt);

	return 0;
}
EXPORT_SYMBOL_GPL(blk_trace_remove);

static int blk_dropped_open(struct inode *inode, struct file *filp)
{
	filp->private_data = inode->i_private;

	return 0;
}

static ssize_t blk_dropped_read(struct file *filp, char __user *buffer,
				size_t count, loff_t *ppos)
{
	struct blk_trace *bt = filp->private_data;
	char buf[16];

	snprintf(buf, sizeof(buf), "%u\n", atomic_read(&bt->dropped));

	return simple_read_from_buffer(buffer, count, ppos, buf, strlen(buf));
}

static const struct file_operations blk_dropped_fops = {
	.owner =	THIS_MODULE,
	.open =		blk_dropped_open,
	.read =		blk_dropped_read,
};

static int blk_msg_open(struct inode *inode, struct file *filp)
{
	filp->private_data = inode->i_private;

	return 0;
}

static ssize_t blk_msg_write(struct file *filp, const char __user *buffer,
				size_t count, loff_t *ppos)
{
	char *msg;
	struct blk_trace *bt;

	if (count > BLK_TN_MAX_MSG)
		return -EINVAL;

	msg = kmalloc(count, GFP_KERNEL);
	if (msg == NULL)
		return -ENOMEM;

	if (copy_from_user(msg, buffer, count)) {
		kfree(msg);
		return -EFAULT;
	}

	bt = filp->private_data;
	__trace_note_message(bt, "%s", msg);
	kfree(msg);

	return count;
}

static const struct file_operations blk_msg_fops = {
	.owner =	THIS_MODULE,
	.open =		blk_msg_open,
	.write =	blk_msg_write,
};

/*
 * Keep track of how many times we encountered a full subbuffer, to aid
 * the user space app in telling how many lost events there were.
 */
static int blk_subbuf_start_callback(struct rchan_buf *buf, void *subbuf,
				     void *prev_subbuf, size_t prev_padding)
{
	struct blk_trace *bt;

	if (!relay_buf_full(buf))
		return 1;

	bt = buf->chan->private_data;
	atomic_inc(&bt->dropped);
	return 0;
}

static int blk_remove_buf_file_callback(struct dentry *dentry)
{
	struct dentry *parent = dentry->d_parent;
	debugfs_remove(dentry);

	/*
	* this will fail for all but the last file, but that is ok. what we
	* care about is the top level buts->name directory going away, when
	* the last trace file is gone. Then we don't have to rmdir() that
	* manually on trace stop, so it nicely solves the issue with
	* force killing of running traces.
	*/

	debugfs_remove(parent);
	return 0;
}

static struct dentry *blk_create_buf_file_callback(const char *filename,
						   struct dentry *parent,
						   int mode,
						   struct rchan_buf *buf,
						   int *is_global)
{
	return debugfs_create_file(filename, mode, parent, buf,
					&relay_file_operations);
}

static struct rchan_callbacks blk_relay_callbacks = {
	.subbuf_start		= blk_subbuf_start_callback,
	.create_buf_file	= blk_create_buf_file_callback,
	.remove_buf_file	= blk_remove_buf_file_callback,
};

/*
 * Setup everything required to start tracing
 */
int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
			struct blk_user_trace_setup *buts)
{
	struct blk_trace *old_bt, *bt = NULL;
	struct dentry *dir = NULL;
	int ret, i;

	if (!buts->buf_size || !buts->buf_nr)
		return -EINVAL;

	strncpy(buts->name, name, BLKTRACE_BDEV_SIZE);
	buts->name[BLKTRACE_BDEV_SIZE - 1] = '\0';

	/*
	 * some device names have larger paths - convert the slashes
	 * to underscores for this to work as expected
	 */
	for (i = 0; i < strlen(buts->name); i++)
		if (buts->name[i] == '/')
			buts->name[i] = '_';

	ret = -ENOMEM;
	bt = kzalloc(sizeof(*bt), GFP_KERNEL);
	if (!bt)
		goto err;

	bt->sequence = alloc_percpu(unsigned long);
	if (!bt->sequence)
		goto err;

	bt->msg_data = __alloc_percpu(BLK_TN_MAX_MSG);
	if (!bt->msg_data)
		goto err;

	ret = -ENOENT;

	if (!blk_tree_root) {
		blk_tree_root = debugfs_create_dir("block", NULL);
		if (!blk_tree_root)
			return -ENOMEM;
	}

	dir = debugfs_create_dir(buts->name, blk_tree_root);

	if (!dir)
		goto err;

	bt->dir = dir;
	bt->dev = dev;
	atomic_set(&bt->dropped, 0);

	ret = -EIO;
	bt->dropped_file = debugfs_create_file("dropped", 0444, dir, bt,
					       &blk_dropped_fops);
	if (!bt->dropped_file)
		goto err;

	bt->msg_file = debugfs_create_file("msg", 0222, dir, bt, &blk_msg_fops);
	if (!bt->msg_file)
		goto err;

	bt->rchan = relay_open("trace", dir, buts->buf_size,
				buts->buf_nr, &blk_relay_callbacks, bt);
	if (!bt->rchan)
		goto err;

	bt->act_mask = buts->act_mask;
	if (!bt->act_mask)
		bt->act_mask = (u16) -1;

	bt->start_lba = buts->start_lba;
	bt->end_lba = buts->end_lba;
	if (!bt->end_lba)
		bt->end_lba = -1ULL;

	bt->pid = buts->pid;
	bt->trace_state = Blktrace_setup;

	mutex_lock(&blk_probe_mutex);
	if (atomic_add_return(1, &blk_probes_ref) == 1) {
		ret = blk_register_tracepoints();
		if (ret)
			goto probe_err;
	}
	mutex_unlock(&blk_probe_mutex);

	ret = -EBUSY;
	old_bt = xchg(&q->blk_trace, bt);
	if (old_bt) {
		(void) xchg(&q->blk_trace, old_bt);
		goto err;
	}

	return 0;
probe_err:
	atomic_dec(&blk_probes_ref);
	mutex_unlock(&blk_probe_mutex);
err:
	if (bt) {
		if (bt->msg_file)
			debugfs_remove(bt->msg_file);
		if (bt->dropped_file)
			debugfs_remove(bt->dropped_file);
		free_percpu(bt->sequence);
		free_percpu(bt->msg_data);
		if (bt->rchan)
			relay_close(bt->rchan);
		kfree(bt);
	}
	return ret;
}

int blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
		    char __user *arg)
{
	struct blk_user_trace_setup buts;
	int ret;

	ret = copy_from_user(&buts, arg, sizeof(buts));
	if (ret)
		return -EFAULT;

	ret = do_blk_trace_setup(q, name, dev, &buts);
	if (ret)
		return ret;

	if (copy_to_user(arg, &buts, sizeof(buts)))
		return -EFAULT;

	return 0;
}
EXPORT_SYMBOL_GPL(blk_trace_setup);

int blk_trace_startstop(struct request_queue *q, int start)
{
	int ret;
	struct blk_trace *bt = q->blk_trace;

	if (bt == NULL)
		return -EINVAL;

	/*
	 * For starting a trace, we can transition from a setup or stopped
	 * trace. For stopping a trace, the state must be running
	 */
	ret = -EINVAL;
	if (start) {
		if (bt->trace_state == Blktrace_setup ||
		    bt->trace_state == Blktrace_stopped) {
			blktrace_seq++;
			smp_mb();
			bt->trace_state = Blktrace_running;

			trace_note_time(bt);
			ret = 0;
		}
	} else {
		if (bt->trace_state == Blktrace_running) {
			bt->trace_state = Blktrace_stopped;
			relay_flush(bt->rchan);
			ret = 0;
		}
	}

	return ret;
}
EXPORT_SYMBOL_GPL(blk_trace_startstop);

/**
 * blk_trace_ioctl: - handle the ioctls associated with tracing
 * @bdev:	the block device
 * @cmd: 	the ioctl cmd
 * @arg:	the argument data, if any
 *
 **/
int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
{
	struct request_queue *q;
	int ret, start = 0;
	char b[BDEVNAME_SIZE];

	q = bdev_get_queue(bdev);
	if (!q)
		return -ENXIO;

	mutex_lock(&bdev->bd_mutex);

	switch (cmd) {
	case BLKTRACESETUP:
		bdevname(bdev, b);
		ret = blk_trace_setup(q, b, bdev->bd_dev, arg);
		break;
	case BLKTRACESTART:
		start = 1;
	case BLKTRACESTOP:
		ret = blk_trace_startstop(q, start);
		break;
	case BLKTRACETEARDOWN:
		ret = blk_trace_remove(q);
		break;
	default:
		ret = -ENOTTY;
		break;
	}

	mutex_unlock(&bdev->bd_mutex);
	return ret;
}

/**
 * blk_trace_shutdown: - stop and cleanup trace structures
 * @q:    the request queue associated with the device
 *
 **/
void blk_trace_shutdown(struct request_queue *q)
{
	if (q->blk_trace) {
		blk_trace_startstop(q, 0);
		blk_trace_remove(q);
	}
}

/*
 * blktrace probes
 */

/**
 * blk_add_trace_rq - Add a trace for a request oriented action
 * @q:		queue the io is for
 * @rq:		the source request
 * @what:	the action
 *
 * Description:
 *     Records an action against a request. Will log the bio offset + size.
 *
 **/
static void blk_add_trace_rq(struct request_queue *q, struct request *rq,
				    u32 what)
{
	struct blk_trace *bt = q->blk_trace;
	int rw = rq->cmd_flags & 0x03;

	if (likely(!bt))
		return;

	if (blk_discard_rq(rq))
		rw |= (1 << BIO_RW_DISCARD);

	if (blk_pc_request(rq)) {
		what |= BLK_TC_ACT(BLK_TC_PC);
		__blk_add_trace(bt, 0, rq->data_len, rw, what, rq->errors,
				sizeof(rq->cmd), rq->cmd);
	} else  {
		what |= BLK_TC_ACT(BLK_TC_FS);
		__blk_add_trace(bt, rq->hard_sector, rq->hard_nr_sectors << 9,
				rw, what, rq->errors, 0, NULL);
	}
}

static void blk_add_trace_rq_abort(struct request_queue *q, struct request *rq)
{
	blk_add_trace_rq(q, rq, BLK_TA_ABORT);
}

static void blk_add_trace_rq_insert(struct request_queue *q, struct request *rq)
{
	blk_add_trace_rq(q, rq, BLK_TA_INSERT);
}

static void blk_add_trace_rq_issue(struct request_queue *q, struct request *rq)
{
	blk_add_trace_rq(q, rq, BLK_TA_ISSUE);
}

static void blk_add_trace_rq_requeue(struct request_queue *q,
				     struct request *rq)
{
	blk_add_trace_rq(q, rq, BLK_TA_REQUEUE);
}

static void blk_add_trace_rq_complete(struct request_queue *q,
				      struct request *rq)
{
	blk_add_trace_rq(q, rq, BLK_TA_COMPLETE);
}

/**
 * blk_add_trace_bio - Add a trace for a bio oriented action
 * @q:		queue the io is for
 * @bio:	the source bio
 * @what:	the action
 *
 * Description:
 *     Records an action against a bio. Will log the bio offset + size.
 *
 **/
static void blk_add_trace_bio(struct request_queue *q, struct bio *bio,
				     u32 what)
{
	struct blk_trace *bt = q->blk_trace;

	if (likely(!bt))
		return;

	__blk_add_trace(bt, bio->bi_sector, bio->bi_size, bio->bi_rw, what,
			!bio_flagged(bio, BIO_UPTODATE), 0, NULL);
}

static void blk_add_trace_bio_bounce(struct request_queue *q, struct bio *bio)
{
	blk_add_trace_bio(q, bio, BLK_TA_BOUNCE);
}

static void blk_add_trace_bio_complete(struct request_queue *q, struct bio *bio)
{
	blk_add_trace_bio(q, bio, BLK_TA_COMPLETE);
}

static void blk_add_trace_bio_backmerge(struct request_queue *q,
					struct bio *bio)
{
	blk_add_trace_bio(q, bio, BLK_TA_BACKMERGE);
}

static void blk_add_trace_bio_frontmerge(struct request_queue *q,
					 struct bio *bio)
{
	blk_add_trace_bio(q, bio, BLK_TA_FRONTMERGE);
}

static void blk_add_trace_bio_queue(struct request_queue *q, struct bio *bio)
{
	blk_add_trace_bio(q, bio, BLK_TA_QUEUE);
}

static void blk_add_trace_getrq(struct request_queue *q,
				struct bio *bio, int rw)
{
	if (bio)
		blk_add_trace_bio(q, bio, BLK_TA_GETRQ);
	else {
		struct blk_trace *bt = q->blk_trace;

		if (bt)
			__blk_add_trace(bt, 0, 0, rw, BLK_TA_GETRQ, 0, 0, NULL);
	}
}


static void blk_add_trace_sleeprq(struct request_queue *q,
				  struct bio *bio, int rw)
{
	if (bio)
		blk_add_trace_bio(q, bio, BLK_TA_SLEEPRQ);
	else {
		struct blk_trace *bt = q->blk_trace;

		if (bt)
			__blk_add_trace(bt, 0, 0, rw, BLK_TA_SLEEPRQ,
					0, 0, NULL);
	}
}

static void blk_add_trace_plug(struct request_queue *q)
{
	struct blk_trace *bt = q->blk_trace;

	if (bt)
		__blk_add_trace(bt, 0, 0, 0, BLK_TA_PLUG, 0, 0, NULL);
}

static void blk_add_trace_unplug_io(struct request_queue *q)
{
	struct blk_trace *bt = q->blk_trace;

	if (bt) {
		unsigned int pdu = q->rq.count[READ] + q->rq.count[WRITE];
		__be64 rpdu = cpu_to_be64(pdu);

		__blk_add_trace(bt, 0, 0, 0, BLK_TA_UNPLUG_IO, 0,
				sizeof(rpdu), &rpdu);
	}
}

static void blk_add_trace_unplug_timer(struct request_queue *q)
{
	struct blk_trace *bt = q->blk_trace;

	if (bt) {
		unsigned int pdu = q->rq.count[READ] + q->rq.count[WRITE];
		__be64 rpdu = cpu_to_be64(pdu);

		__blk_add_trace(bt, 0, 0, 0, BLK_TA_UNPLUG_TIMER, 0,
				sizeof(rpdu), &rpdu);
	}
}

static void blk_add_trace_split(struct request_queue *q, struct bio *bio,
				unsigned int pdu)
{
	struct blk_trace *bt = q->blk_trace;

	if (bt) {
		__be64 rpdu = cpu_to_be64(pdu);

		__blk_add_trace(bt, bio->bi_sector, bio->bi_size, bio->bi_rw,
				BLK_TA_SPLIT, !bio_flagged(bio, BIO_UPTODATE),
				sizeof(rpdu), &rpdu);
	}
}

/**
 * blk_add_trace_remap - Add a trace for a remap operation
 * @q:		queue the io is for
 * @bio:	the source bio
 * @dev:	target device
 * @from:	source sector
 * @to:		target sector
 *
 * Description:
 *     Device mapper or raid target sometimes need to split a bio because
 *     it spans a stripe (or similar). Add a trace for that action.
 *
 **/
static void blk_add_trace_remap(struct request_queue *q, struct bio *bio,
				       dev_t dev, sector_t from, sector_t to)
{
	struct blk_trace *bt = q->blk_trace;
	struct blk_io_trace_remap r;

	if (likely(!bt))
		return;

	r.device = cpu_to_be32(dev);
	r.device_from = cpu_to_be32(bio->bi_bdev->bd_dev);
	r.sector = cpu_to_be64(to);

	__blk_add_trace(bt, from, bio->bi_size, bio->bi_rw, BLK_TA_REMAP,
			!bio_flagged(bio, BIO_UPTODATE), sizeof(r), &r);
}

/**
 * blk_add_driver_data - Add binary message with driver-specific data
 * @q:		queue the io is for
 * @rq:		io request
 * @data:	driver-specific data
 * @len:	length of driver-specific data
 *
 * Description:
 *     Some drivers might want to write driver-specific data per request.
 *
 **/
void blk_add_driver_data(struct request_queue *q,
			 struct request *rq,
			 void *data, size_t len)
{
	struct blk_trace *bt = q->blk_trace;

	if (likely(!bt))
		return;

	if (blk_pc_request(rq))
		__blk_add_trace(bt, 0, rq->data_len, 0, BLK_TA_DRV_DATA,
				rq->errors, len, data);
	else
		__blk_add_trace(bt, rq->hard_sector, rq->hard_nr_sectors << 9,
				0, BLK_TA_DRV_DATA, rq->errors, len, data);
}
EXPORT_SYMBOL_GPL(blk_add_driver_data);

static int blk_register_tracepoints(void)
{
	int ret;

	ret = register_trace_block_rq_abort(blk_add_trace_rq_abort);
	WARN_ON(ret);
	ret = register_trace_block_rq_insert(blk_add_trace_rq_insert);
	WARN_ON(ret);
	ret = register_trace_block_rq_issue(blk_add_trace_rq_issue);
	WARN_ON(ret);
	ret = register_trace_block_rq_requeue(blk_add_trace_rq_requeue);
	WARN_ON(ret);
	ret = register_trace_block_rq_complete(blk_add_trace_rq_complete);
	WARN_ON(ret);
	ret = register_trace_block_bio_bounce(blk_add_trace_bio_bounce);
	WARN_ON(ret);
	ret = register_trace_block_bio_complete(blk_add_trace_bio_complete);
	WARN_ON(ret);
	ret = register_trace_block_bio_backmerge(blk_add_trace_bio_backmerge);
	WARN_ON(ret);
	ret = register_trace_block_bio_frontmerge(blk_add_trace_bio_frontmerge);
	WARN_ON(ret);
	ret = register_trace_block_bio_queue(blk_add_trace_bio_queue);
	WARN_ON(ret);
	ret = register_trace_block_getrq(blk_add_trace_getrq);
	WARN_ON(ret);
	ret = register_trace_block_sleeprq(blk_add_trace_sleeprq);
	WARN_ON(ret);
	ret = register_trace_block_plug(blk_add_trace_plug);
	WARN_ON(ret);
	ret = register_trace_block_unplug_timer(blk_add_trace_unplug_timer);
	WARN_ON(ret);
	ret = register_trace_block_unplug_io(blk_add_trace_unplug_io);
	WARN_ON(ret);
	ret = register_trace_block_split(blk_add_trace_split);
	WARN_ON(ret);
	ret = register_trace_block_remap(blk_add_trace_remap);
	WARN_ON(ret);
	return 0;
}

static void blk_unregister_tracepoints(void)
{
	unregister_trace_block_remap(blk_add_trace_remap);
	unregister_trace_block_split(blk_add_trace_split);
	unregister_trace_block_unplug_io(blk_add_trace_unplug_io);
	unregister_trace_block_unplug_timer(blk_add_trace_unplug_timer);
	unregister_trace_block_plug(blk_add_trace_plug);
	unregister_trace_block_sleeprq(blk_add_trace_sleeprq);
	unregister_trace_block_getrq(blk_add_trace_getrq);
	unregister_trace_block_bio_queue(blk_add_trace_bio_queue);
	unregister_trace_block_bio_frontmerge(blk_add_trace_bio_frontmerge);
	unregister_trace_block_bio_backmerge(blk_add_trace_bio_backmerge);
	unregister_trace_block_bio_complete(blk_add_trace_bio_complete);
	unregister_trace_block_bio_bounce(blk_add_trace_bio_bounce);
	unregister_trace_block_rq_complete(blk_add_trace_rq_complete);
	unregister_trace_block_rq_requeue(blk_add_trace_rq_requeue);
	unregister_trace_block_rq_issue(blk_add_trace_rq_issue);
	unregister_trace_block_rq_insert(blk_add_trace_rq_insert);
	unregister_trace_block_rq_abort(blk_add_trace_rq_abort);

	tracepoint_synchronize_unregister();
}

/*
 * struct blk_io_tracer formatting routines
 */

static void fill_rwbs(char *rwbs, const struct blk_io_trace *t)
{
	int i = 0;

	if (t->action & BLK_TC_DISCARD)
		rwbs[i++] = 'D';
	else if (t->action & BLK_TC_WRITE)
		rwbs[i++] = 'W';
	else if (t->bytes)
		rwbs[i++] = 'R';
	else
		rwbs[i++] = 'N';

	if (t->action & BLK_TC_AHEAD)
		rwbs[i++] = 'A';
	if (t->action & BLK_TC_BARRIER)
		rwbs[i++] = 'B';
	if (t->action & BLK_TC_SYNC)
		rwbs[i++] = 'S';
	if (t->action & BLK_TC_META)
		rwbs[i++] = 'M';

	rwbs[i] = '\0';
}

static inline
const struct blk_io_trace *te_blk_io_trace(const struct trace_entry *ent)
{
	return (const struct blk_io_trace *)ent;
}

static inline const void *pdu_start(const struct trace_entry *ent)
{
	return te_blk_io_trace(ent) + 1;
}

static inline u32 t_sec(const struct trace_entry *ent)
{
	return te_blk_io_trace(ent)->bytes >> 9;
}

static inline unsigned long long t_sector(const struct trace_entry *ent)
{
	return te_blk_io_trace(ent)->sector;
}

static inline __u16 t_error(const struct trace_entry *ent)
{
	return te_blk_io_trace(ent)->sector;
}

static __u64 get_pdu_int(const struct trace_entry *ent)
{
	const __u64 *val = pdu_start(ent);
	return be64_to_cpu(*val);
}

static void get_pdu_remap(const struct trace_entry *ent,
			  struct blk_io_trace_remap *r)
{
	const struct blk_io_trace_remap *__r = pdu_start(ent);
	__u64 sector = __r->sector;

	r->device = be32_to_cpu(__r->device);
	r->device_from = be32_to_cpu(__r->device_from);
	r->sector = be64_to_cpu(sector);
}

static int blk_log_action_iter(struct trace_iterator *iter, const char *act)
{
	char rwbs[6];
	unsigned long long ts  = ns2usecs(iter->ts);
	unsigned long usec_rem = do_div(ts, USEC_PER_SEC);
	unsigned secs	       = (unsigned long)ts;
	const struct trace_entry *ent = iter->ent;
	const struct blk_io_trace *t = (const struct blk_io_trace *)ent;

	fill_rwbs(rwbs, t);

	return trace_seq_printf(&iter->seq,
				"%3d,%-3d %2d %5d.%06lu %5u %2s %3s ",
				MAJOR(t->device), MINOR(t->device), iter->cpu,
				secs, usec_rem, ent->pid, act, rwbs);
}

static int blk_log_action_seq(struct trace_seq *s, const struct blk_io_trace *t,
			      const char *act)
{
	char rwbs[6];
	fill_rwbs(rwbs, t);
	return trace_seq_printf(s, "%3d,%-3d %2s %3s ",
				MAJOR(t->device), MINOR(t->device), act, rwbs);
}

static int blk_log_generic(struct trace_seq *s, const struct trace_entry *ent)
{
	const char *cmd = trace_find_cmdline(ent->pid);

	if (t_sec(ent))
		return trace_seq_printf(s, "%llu + %u [%s]\n",
					t_sector(ent), t_sec(ent), cmd);
	return trace_seq_printf(s, "[%s]\n", cmd);
}

static int blk_log_with_error(struct trace_seq *s,
			      const struct trace_entry *ent)
{
	if (t_sec(ent))
		return trace_seq_printf(s, "%llu + %u [%d]\n", t_sector(ent),
					t_sec(ent), t_error(ent));
	return trace_seq_printf(s, "%llu [%d]\n", t_sector(ent), t_error(ent));
}

static int blk_log_remap(struct trace_seq *s, const struct trace_entry *ent)
{
	struct blk_io_trace_remap r = { .device = 0, };

	get_pdu_remap(ent, &r);
	return trace_seq_printf(s, "%llu + %u <- (%d,%d) %llu\n",
			       t_sector(ent),
			       t_sec(ent), MAJOR(r.device), MINOR(r.device),
			       (unsigned long long)r.sector);
}

static int blk_log_plug(struct trace_seq *s, const struct trace_entry *ent)
{
	return trace_seq_printf(s, "[%s]\n", trace_find_cmdline(ent->pid));
}

static int blk_log_unplug(struct trace_seq *s, const struct trace_entry *ent)
{
	return trace_seq_printf(s, "[%s] %llu\n", trace_find_cmdline(ent->pid),
				get_pdu_int(ent));
}

static int blk_log_split(struct trace_seq *s, const struct trace_entry *ent)
{
	return trace_seq_printf(s, "%llu / %llu [%s]\n", t_sector(ent),
				get_pdu_int(ent), trace_find_cmdline(ent->pid));
}

/*
 * struct tracer operations
 */

static void blk_tracer_print_header(struct seq_file *m)
{
	if (!(blk_tracer_flags.val & TRACE_BLK_OPT_CLASSIC))
		return;
	seq_puts(m, "# DEV   CPU TIMESTAMP     PID ACT FLG\n"
		    "#  |     |     |           |   |   |\n");
}

static void blk_tracer_start(struct trace_array *tr)
{
	mutex_lock(&blk_probe_mutex);
	if (atomic_add_return(1, &blk_probes_ref) == 1)
		if (blk_register_tracepoints())
			atomic_dec(&blk_probes_ref);
	mutex_unlock(&blk_probe_mutex);
	trace_flags &= ~TRACE_ITER_CONTEXT_INFO;
}

static int blk_tracer_init(struct trace_array *tr)
{
	blk_tr = tr;
	blk_tracer_start(tr);
	mutex_lock(&blk_probe_mutex);
	blk_tracer_enabled++;
	mutex_unlock(&blk_probe_mutex);
	return 0;
}

static void blk_tracer_stop(struct trace_array *tr)
{
	trace_flags |= TRACE_ITER_CONTEXT_INFO;
	mutex_lock(&blk_probe_mutex);
	if (atomic_dec_and_test(&blk_probes_ref))
		blk_unregister_tracepoints();
	mutex_unlock(&blk_probe_mutex);
}

static void blk_tracer_reset(struct trace_array *tr)
{
	if (!atomic_read(&blk_probes_ref))
		return;

	mutex_lock(&blk_probe_mutex);
	blk_tracer_enabled--;
	WARN_ON(blk_tracer_enabled < 0);
	mutex_unlock(&blk_probe_mutex);

	blk_tracer_stop(tr);
}

static struct {
	const char *act[2];
	int 	   (*print)(struct trace_seq *s, const struct trace_entry *ent);
} what2act[] __read_mostly = {
	[__BLK_TA_QUEUE]	= {{  "Q", "queue" }, 	   blk_log_generic },
	[__BLK_TA_BACKMERGE]	= {{  "M", "backmerge" },  blk_log_generic },
	[__BLK_TA_FRONTMERGE]	= {{  "F", "frontmerge" }, blk_log_generic },
	[__BLK_TA_GETRQ]	= {{  "G", "getrq" },	   blk_log_generic },
	[__BLK_TA_SLEEPRQ]	= {{  "S", "sleeprq" },	   blk_log_generic },
	[__BLK_TA_REQUEUE]	= {{  "R", "requeue" },	   blk_log_with_error },
	[__BLK_TA_ISSUE]	= {{  "D", "issue" },	   blk_log_generic },
	[__BLK_TA_COMPLETE]	= {{  "C", "complete" },   blk_log_with_error },
	[__BLK_TA_PLUG]		= {{  "P", "plug" },	   blk_log_plug },
	[__BLK_TA_UNPLUG_IO]	= {{  "U", "unplug_io" },  blk_log_unplug },
	[__BLK_TA_UNPLUG_TIMER]	= {{ "UT", "unplug_timer" }, blk_log_unplug },
	[__BLK_TA_INSERT]	= {{  "I", "insert" },	   blk_log_generic },
	[__BLK_TA_SPLIT]	= {{  "X", "split" },	   blk_log_split },
	[__BLK_TA_BOUNCE]	= {{  "B", "bounce" },	   blk_log_generic },
	[__BLK_TA_REMAP]	= {{  "A", "remap" },	   blk_log_remap },
};

static enum print_line_t blk_trace_event_print(struct trace_iterator *iter,
					       int flags)
{
	struct trace_seq *s = &iter->seq;
	const struct blk_io_trace *t = (struct blk_io_trace *)iter->ent;
	const u16 what = t->action & ((1 << BLK_TC_SHIFT) - 1);
	int ret;

	if (!trace_print_context(iter))
		return TRACE_TYPE_PARTIAL_LINE;

	if (unlikely(what == 0 || what > ARRAY_SIZE(what2act)))
		ret = trace_seq_printf(s, "Bad pc action %x\n", what);
	else {
		const bool long_act = !!(trace_flags & TRACE_ITER_VERBOSE);
		ret = blk_log_action_seq(s, t, what2act[what].act[long_act]);
		if (ret)
			ret = what2act[what].print(s, iter->ent);
	}

	return ret ? TRACE_TYPE_HANDLED : TRACE_TYPE_PARTIAL_LINE;
}

static int blk_trace_synthesize_old_trace(struct trace_iterator *iter)
{
	struct trace_seq *s = &iter->seq;
	struct blk_io_trace *t = (struct blk_io_trace *)iter->ent;
	const int offset = offsetof(struct blk_io_trace, sector);
	struct blk_io_trace old = {
		.magic	  = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION,
		.time     = ns2usecs(iter->ts),
	};

	if (!trace_seq_putmem(s, &old, offset))
		return 0;
	return trace_seq_putmem(s, &t->sector,
				sizeof(old) - offset + t->pdu_len);
}

static enum print_line_t
blk_trace_event_print_binary(struct trace_iterator *iter, int flags)
{
	return blk_trace_synthesize_old_trace(iter) ?
			TRACE_TYPE_HANDLED : TRACE_TYPE_PARTIAL_LINE;
}

static enum print_line_t blk_tracer_print_line(struct trace_iterator *iter)
{
	const struct blk_io_trace *t;
	u16 what;
	int ret;

	if (!(blk_tracer_flags.val & TRACE_BLK_OPT_CLASSIC))
		return TRACE_TYPE_UNHANDLED;

	t = (const struct blk_io_trace *)iter->ent;
	what = t->action & ((1 << BLK_TC_SHIFT) - 1);

	if (unlikely(what == 0 || what > ARRAY_SIZE(what2act)))
		ret = trace_seq_printf(&iter->seq, "Bad pc action %x\n", what);
	else {
		const bool long_act = !!(trace_flags & TRACE_ITER_VERBOSE);
		ret = blk_log_action_iter(iter, what2act[what].act[long_act]);
		if (ret)
			ret = what2act[what].print(&iter->seq, iter->ent);
	}

	return ret ? TRACE_TYPE_HANDLED : TRACE_TYPE_PARTIAL_LINE;
}

static struct tracer blk_tracer __read_mostly = {
	.name		= "blk",
	.init		= blk_tracer_init,
	.reset		= blk_tracer_reset,
	.start		= blk_tracer_start,
	.stop		= blk_tracer_stop,
	.print_header	= blk_tracer_print_header,
	.print_line	= blk_tracer_print_line,
	.flags		= &blk_tracer_flags,
};

static struct trace_event trace_blk_event = {
	.type	 	= TRACE_BLK,
	.trace		= blk_trace_event_print,
	.latency_trace	= blk_trace_event_print,
	.binary		= blk_trace_event_print_binary,
};

static int __init init_blk_tracer(void)
{
	if (!register_ftrace_event(&trace_blk_event)) {
		pr_warning("Warning: could not register block events\n");
		return 1;
	}

	if (register_tracer(&blk_tracer) != 0) {
		pr_warning("Warning: could not register the block tracer\n");
		unregister_ftrace_event(&trace_blk_event);
		return 1;
	}

	return 0;
}

device_initcall(init_blk_tracer);

static int blk_trace_remove_queue(struct request_queue *q)
{
	struct blk_trace *bt;

	bt = xchg(&q->blk_trace, NULL);
	if (bt == NULL)
		return -EINVAL;

	kfree(bt);
	return 0;
}

/*
 * Setup everything required to start tracing
 */
static int blk_trace_setup_queue(struct request_queue *q, dev_t dev)
{
	struct blk_trace *old_bt, *bt = NULL;
	int ret;

	ret = -ENOMEM;
	bt = kzalloc(sizeof(*bt), GFP_KERNEL);
	if (!bt)
		goto err;

	bt->dev = dev;
	bt->act_mask = (u16)-1;
	bt->end_lba = -1ULL;
	bt->trace_state = Blktrace_running;

	old_bt = xchg(&q->blk_trace, bt);
	if (old_bt != NULL) {
		(void)xchg(&q->blk_trace, old_bt);
		kfree(bt);
		ret = -EBUSY;
	}
	return 0;
err:
	return ret;
}

/*
 * sysfs interface to enable and configure tracing
 */

static ssize_t sysfs_blk_trace_enable_show(struct device *dev,
					   struct device_attribute *attr,
					   char *buf)
{
	struct hd_struct *p = dev_to_part(dev);
	struct block_device *bdev;
	ssize_t ret = -ENXIO;

	lock_kernel();
	bdev = bdget(part_devt(p));
	if (bdev != NULL) {
		struct request_queue *q = bdev_get_queue(bdev);

		if (q != NULL) {
			mutex_lock(&bdev->bd_mutex);
			ret = sprintf(buf, "%u\n", !!q->blk_trace);
			mutex_unlock(&bdev->bd_mutex);
		}

		bdput(bdev);
	}

	unlock_kernel();
	return ret;
}

static ssize_t sysfs_blk_trace_enable_store(struct device *dev,
					    struct device_attribute *attr,
					    const char *buf, size_t count)
{
	struct block_device *bdev;
	struct request_queue *q;
	struct hd_struct *p;
	int value;
	ssize_t ret = -ENXIO;

	if (count == 0 || sscanf(buf, "%d", &value) != 1)
		goto out;

	lock_kernel();
	p = dev_to_part(dev);
	bdev = bdget(part_devt(p));
	if (bdev == NULL)
		goto out_unlock_kernel;

	q = bdev_get_queue(bdev);
	if (q == NULL)
		goto out_bdput;

	mutex_lock(&bdev->bd_mutex);
	if (value)
		ret = blk_trace_setup_queue(q, bdev->bd_dev);
	else
		ret = blk_trace_remove_queue(q);
	mutex_unlock(&bdev->bd_mutex);

	if (ret == 0)
		ret = count;
out_bdput:
	bdput(bdev);
out_unlock_kernel:
	unlock_kernel();
out:
	return ret;
}

static ssize_t sysfs_blk_trace_attr_show(struct device *dev,
					 struct device_attribute *attr,
					 char *buf);
static ssize_t sysfs_blk_trace_attr_store(struct device *dev,
					  struct device_attribute *attr,
					  const char *buf, size_t count);
#define BLK_TRACE_DEVICE_ATTR(_name) \
	DEVICE_ATTR(_name, S_IRUGO | S_IWUSR, \
		    sysfs_blk_trace_attr_show, \
		    sysfs_blk_trace_attr_store)

static DEVICE_ATTR(enable, S_IRUGO | S_IWUSR,
		   sysfs_blk_trace_enable_show, sysfs_blk_trace_enable_store);
static BLK_TRACE_DEVICE_ATTR(act_mask);
static BLK_TRACE_DEVICE_ATTR(pid);
static BLK_TRACE_DEVICE_ATTR(start_lba);
static BLK_TRACE_DEVICE_ATTR(end_lba);

static struct attribute *blk_trace_attrs[] = {
	&dev_attr_enable.attr,
	&dev_attr_act_mask.attr,
	&dev_attr_pid.attr,
	&dev_attr_start_lba.attr,
	&dev_attr_end_lba.attr,
	NULL
};

struct attribute_group blk_trace_attr_group = {
	.name  = "trace",
	.attrs = blk_trace_attrs,
};

static int blk_str2act_mask(const char *str)
{
	int mask = 0;
	char *copy = kstrdup(str, GFP_KERNEL), *s;

	if (copy == NULL)
		return -ENOMEM;

	s = strstrip(copy);

	while (1) {
		char *sep = strchr(s, ',');

		if (sep != NULL)
			*sep = '\0';

		if (strcasecmp(s, "barrier") == 0)
			mask |= BLK_TC_BARRIER;
		else if (strcasecmp(s, "complete") == 0)
			mask |= BLK_TC_COMPLETE;
		else if (strcasecmp(s, "fs") == 0)
			mask |= BLK_TC_FS;
		else if (strcasecmp(s, "issue") == 0)
			mask |= BLK_TC_ISSUE;
		else if (strcasecmp(s, "pc") == 0)
			mask |= BLK_TC_PC;
		else if (strcasecmp(s, "queue") == 0)
			mask |= BLK_TC_QUEUE;
		else if (strcasecmp(s, "read") == 0)
			mask |= BLK_TC_READ;
		else if (strcasecmp(s, "requeue") == 0)
			mask |= BLK_TC_REQUEUE;
		else if (strcasecmp(s, "sync") == 0)
			mask |= BLK_TC_SYNC;
		else if (strcasecmp(s, "write") == 0)
			mask |= BLK_TC_WRITE;

		if (sep == NULL)
			break;

		s = sep + 1;
	}
	kfree(copy);

	return mask;
}

static ssize_t sysfs_blk_trace_attr_show(struct device *dev,
					 struct device_attribute *attr,
					 char *buf)
{
	struct hd_struct *p = dev_to_part(dev);
	struct request_queue *q;
	struct block_device *bdev;
	ssize_t ret = -ENXIO;

	lock_kernel();
	bdev = bdget(part_devt(p));
	if (bdev == NULL)
		goto out_unlock_kernel;

	q = bdev_get_queue(bdev);
	if (q == NULL)
		goto out_bdput;
	mutex_lock(&bdev->bd_mutex);
	if (q->blk_trace == NULL)
		ret = sprintf(buf, "disabled\n");
	else if (attr == &dev_attr_act_mask)
		ret = sprintf(buf, "%#x\n", q->blk_trace->act_mask);
	else if (attr == &dev_attr_pid)
		ret = sprintf(buf, "%u\n", q->blk_trace->pid);
	else if (attr == &dev_attr_start_lba)
		ret = sprintf(buf, "%llu\n", q->blk_trace->start_lba);
	else if (attr == &dev_attr_end_lba)
		ret = sprintf(buf, "%llu\n", q->blk_trace->end_lba);
	mutex_unlock(&bdev->bd_mutex);
out_bdput:
	bdput(bdev);
out_unlock_kernel:
	unlock_kernel();
	return ret;
}

static ssize_t sysfs_blk_trace_attr_store(struct device *dev,
					  struct device_attribute *attr,
					  const char *buf, size_t count)
{
	struct block_device *bdev;
	struct request_queue *q;
	struct hd_struct *p;
	u64 value;
	ssize_t ret = -ENXIO;

	if (count == 0)
		goto out;

	if (attr == &dev_attr_act_mask) {
		if (sscanf(buf, "%llx", &value) != 1) {
			/* Assume it is a list of trace category names */
			value = blk_str2act_mask(buf);
			if (value < 0)
				goto out;
		}
	} else if (sscanf(buf, "%llu", &value) != 1)
		goto out;

	lock_kernel();
	p = dev_to_part(dev);
	bdev = bdget(part_devt(p));
	if (bdev == NULL)
		goto out_unlock_kernel;

	q = bdev_get_queue(bdev);
	if (q == NULL)
		goto out_bdput;

	mutex_lock(&bdev->bd_mutex);
	ret = 0;
	if (q->blk_trace == NULL)
		ret = blk_trace_setup_queue(q, bdev->bd_dev);

	if (ret == 0) {
		if (attr == &dev_attr_act_mask)
			q->blk_trace->act_mask = value;
		else if (attr == &dev_attr_pid)
			q->blk_trace->pid = value;
		else if (attr == &dev_attr_start_lba)
			q->blk_trace->start_lba = value;
		else if (attr == &dev_attr_end_lba)
			q->blk_trace->end_lba = value;
		ret = count;
	}
	mutex_unlock(&bdev->bd_mutex);
out_bdput:
	bdput(bdev);
out_unlock_kernel:
	unlock_kernel();
out:
	return ret;
}