aboutsummaryrefslogtreecommitdiff
path: root/fs/aio.c
blob: aec2b1916d1b27e4bc9411212359801b8ba70386 (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
/*
 *	An async IO implementation for Linux
 *	Written by Benjamin LaHaise <bcrl@kvack.org>
 *
 *	Implements an efficient asynchronous io interface.
 *
 *	Copyright 2000, 2001, 2002 Red Hat, Inc.  All Rights Reserved.
 *
 *	See ../COPYING for licensing terms.
 */
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/time.h>
#include <linux/aio_abi.h>
#include <linux/module.h>
#include <linux/syscalls.h>

#define DEBUG 0

#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/slab.h>
#include <linux/timer.h>
#include <linux/aio.h>
#include <linux/highmem.h>
#include <linux/workqueue.h>
#include <linux/security.h>

#include <asm/kmap_types.h>
#include <asm/uaccess.h>
#include <asm/mmu_context.h>

#if DEBUG > 1
#define dprintk		printk
#else
#define dprintk(x...)	do { ; } while (0)
#endif

/*------ sysctl variables----*/
static DEFINE_SPINLOCK(aio_nr_lock);
unsigned long aio_nr;		/* current system wide number of aio requests */
unsigned long aio_max_nr = 0x10000; /* system wide maximum number of aio requests */
/*----end sysctl variables---*/

static kmem_cache_t	*kiocb_cachep;
static kmem_cache_t	*kioctx_cachep;

static struct workqueue_struct *aio_wq;

/* Used for rare fput completion. */
static void aio_fput_routine(void *);
static DECLARE_WORK(fput_work, aio_fput_routine, NULL);

static DEFINE_SPINLOCK(fput_lock);
static LIST_HEAD(fput_head);

static void aio_kick_handler(void *);
static void aio_queue_work(struct kioctx *);

/* aio_setup
 *	Creates the slab caches used by the aio routines, panic on
 *	failure as this is done early during the boot sequence.
 */
static int __init aio_setup(void)
{
	kiocb_cachep = kmem_cache_create("kiocb", sizeof(struct kiocb),
				0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
	kioctx_cachep = kmem_cache_create("kioctx", sizeof(struct kioctx),
				0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);

	aio_wq = create_workqueue("aio");

	pr_debug("aio_setup: sizeof(struct page) = %d\n", (int)sizeof(struct page));

	return 0;
}

static void aio_free_ring(struct kioctx *ctx)
{
	struct aio_ring_info *info = &ctx->ring_info;
	long i;

	for (i=0; i<info->nr_pages; i++)
		put_page(info->ring_pages[i]);

	if (info->mmap_size) {
		down_write(&ctx->mm->mmap_sem);
		do_munmap(ctx->mm, info->mmap_base, info->mmap_size);
		up_write(&ctx->mm->mmap_sem);
	}

	if (info->ring_pages && info->ring_pages != info->internal_pages)
		kfree(info->ring_pages);
	info->ring_pages = NULL;
	info->nr = 0;
}

static int aio_setup_ring(struct kioctx *ctx)
{
	struct aio_ring *ring;
	struct aio_ring_info *info = &ctx->ring_info;
	unsigned nr_events = ctx->max_reqs;
	unsigned long size;
	int nr_pages;

	/* Compensate for the ring buffer's head/tail overlap entry */
	nr_events += 2;	/* 1 is required, 2 for good luck */

	size = sizeof(struct aio_ring);
	size += sizeof(struct io_event) * nr_events;
	nr_pages = (size + PAGE_SIZE-1) >> PAGE_SHIFT;

	if (nr_pages < 0)
		return -EINVAL;

	nr_events = (PAGE_SIZE * nr_pages - sizeof(struct aio_ring)) / sizeof(struct io_event);

	info->nr = 0;
	info->ring_pages = info->internal_pages;
	if (nr_pages > AIO_RING_PAGES) {
		info->ring_pages = kmalloc(sizeof(struct page *) * nr_pages, GFP_KERNEL);
		if (!info->ring_pages)
			return -ENOMEM;
		memset(info->ring_pages, 0, sizeof(struct page *) * nr_pages);
	}

	info->mmap_size = nr_pages * PAGE_SIZE;
	dprintk("attempting mmap of %lu bytes\n", info->mmap_size);
	down_write(&ctx->mm->mmap_sem);
	info->mmap_base = do_mmap(NULL, 0, info->mmap_size, 
				  PROT_READ|PROT_WRITE, MAP_ANON|MAP_PRIVATE,
				  0);
	if (IS_ERR((void *)info->mmap_base)) {
		up_write(&ctx->mm->mmap_sem);
		printk("mmap err: %ld\n", -info->mmap_base);
		info->mmap_size = 0;
		aio_free_ring(ctx);
		return -EAGAIN;
	}

	dprintk("mmap address: 0x%08lx\n", info->mmap_base);
	info->nr_pages = get_user_pages(current, ctx->mm,
					info->mmap_base, nr_pages, 
					1, 0, info->ring_pages, NULL);
	up_write(&ctx->mm->mmap_sem);

	if (unlikely(info->nr_pages != nr_pages)) {
		aio_free_ring(ctx);
		return -EAGAIN;
	}

	ctx->user_id = info->mmap_base;

	info->nr = nr_events;		/* trusted copy */

	ring = kmap_atomic(info->ring_pages[0], KM_USER0);
	ring->nr = nr_events;	/* user copy */
	ring->id = ctx->user_id;
	ring->head = ring->tail = 0;
	ring->magic = AIO_RING_MAGIC;
	ring->compat_features = AIO_RING_COMPAT_FEATURES;
	ring->incompat_features = AIO_RING_INCOMPAT_FEATURES;
	ring->header_length = sizeof(struct aio_ring);
	kunmap_atomic(ring, KM_USER0);

	return 0;
}


/* aio_ring_event: returns a pointer to the event at the given index from
 * kmap_atomic(, km).  Release the pointer with put_aio_ring_event();
 */
#define AIO_EVENTS_PER_PAGE	(PAGE_SIZE / sizeof(struct io_event))
#define AIO_EVENTS_FIRST_PAGE	((PAGE_SIZE - sizeof(struct aio_ring)) / sizeof(struct io_event))
#define AIO_EVENTS_OFFSET	(AIO_EVENTS_PER_PAGE - AIO_EVENTS_FIRST_PAGE)

#define aio_ring_event(info, nr, km) ({					\
	unsigned pos = (nr) + AIO_EVENTS_OFFSET;			\
	struct io_event *__event;					\
	__event = kmap_atomic(						\
			(info)->ring_pages[pos / AIO_EVENTS_PER_PAGE], km); \
	__event += pos % AIO_EVENTS_PER_PAGE;				\
	__event;							\
})

#define put_aio_ring_event(event, km) do {	\
	struct io_event *__event = (event);	\
	(void)__event;				\
	kunmap_atomic((void *)((unsigned long)__event & PAGE_MASK), km); \
} while(0)

/* ioctx_alloc
 *	Allocates and initializes an ioctx.  Returns an ERR_PTR if it failed.
 */
static struct kioctx *ioctx_alloc(unsigned nr_events)
{
	struct mm_struct *mm;
	struct kioctx *ctx;

	/* Prevent overflows */
	if ((nr_events > (0x10000000U / sizeof(struct io_event))) ||
	    (nr_events > (0x10000000U / sizeof(struct kiocb)))) {
		pr_debug("ENOMEM: nr_events too high\n");
		return ERR_PTR(-EINVAL);
	}

	if ((unsigned long)nr_events > aio_max_nr)
		return ERR_PTR(-EAGAIN);

	ctx = kmem_cache_alloc(kioctx_cachep, GFP_KERNEL);
	if (!ctx)
		return ERR_PTR(-ENOMEM);

	memset(ctx, 0, sizeof(*ctx));
	ctx->max_reqs = nr_events;
	mm = ctx->mm = current->mm;
	atomic_inc(&mm->mm_count);

	atomic_set(&ctx->users, 1);
	spin_lock_init(&ctx->ctx_lock);
	spin_lock_init(&ctx->ring_info.ring_lock);
	init_waitqueue_head(&ctx->wait);

	INIT_LIST_HEAD(&ctx->active_reqs);
	INIT_LIST_HEAD(&ctx->run_list);
	INIT_WORK(&ctx->wq, aio_kick_handler, ctx);

	if (aio_setup_ring(ctx) < 0)
		goto out_freectx;

	/* limit the number of system wide aios */
	spin_lock(&aio_nr_lock);
	if (aio_nr + ctx->max_reqs > aio_max_nr ||
	    aio_nr + ctx->max_reqs < aio_nr)
		ctx->max_reqs = 0;
	else
		aio_nr += ctx->max_reqs;
	spin_unlock(&aio_nr_lock);
	if (ctx->max_reqs == 0)
		goto out_cleanup;

	/* now link into global list.  kludge.  FIXME */
	write_lock(&mm->ioctx_list_lock);
	ctx->next = mm->ioctx_list;
	mm->ioctx_list = ctx;
	write_unlock(&mm->ioctx_list_lock);

	dprintk("aio: allocated ioctx %p[%ld]: mm=%p mask=0x%x\n",
		ctx, ctx->user_id, current->mm, ctx->ring_info.nr);
	return ctx;

out_cleanup:
	__put_ioctx(ctx);
	return ERR_PTR(-EAGAIN);

out_freectx:
	mmdrop(mm);
	kmem_cache_free(kioctx_cachep, ctx);
	ctx = ERR_PTR(-ENOMEM);

	dprintk("aio: error allocating ioctx %p\n", ctx);
	return ctx;
}

/* aio_cancel_all
 *	Cancels all outstanding aio requests on an aio context.  Used 
 *	when the processes owning a context have all exited to encourage 
 *	the rapid destruction of the kioctx.
 */
static void aio_cancel_all(struct kioctx *ctx)
{
	int (*cancel)(struct kiocb *, struct io_event *);
	struct io_event res;
	spin_lock_irq(&ctx->ctx_lock);
	ctx->dead = 1;
	while (!list_empty(&ctx->active_reqs)) {
		struct list_head *pos = ctx->active_reqs.next;
		struct kiocb *iocb = list_kiocb(pos);
		list_del_init(&iocb->ki_list);
		cancel = iocb->ki_cancel;
		kiocbSetCancelled(iocb);
		if (cancel) {
			iocb->ki_users++;
			spin_unlock_irq(&ctx->ctx_lock);
			cancel(iocb, &res);
			spin_lock_irq(&ctx->ctx_lock);
		}
	}
	spin_unlock_irq(&ctx->ctx_lock);
}

static void wait_for_all_aios(struct kioctx *ctx)
{
	struct task_struct *tsk = current;
	DECLARE_WAITQUEUE(wait, tsk);

	if (!ctx->reqs_active)
		return;

	add_wait_queue(&ctx->wait, &wait);
	set_task_state(tsk, TASK_UNINTERRUPTIBLE);
	while (ctx->reqs_active) {
		schedule();
		set_task_state(tsk, TASK_UNINTERRUPTIBLE);
	}
	__set_task_state(tsk, TASK_RUNNING);
	remove_wait_queue(&ctx->wait, &wait);
}

/* wait_on_sync_kiocb:
 *	Waits on the given sync kiocb to complete.
 */
ssize_t fastcall wait_on_sync_kiocb(struct kiocb *iocb)
{
	while (iocb->ki_users) {
		set_current_state(TASK_UNINTERRUPTIBLE);
		if (!iocb->ki_users)
			break;
		schedule();
	}
	__set_current_state(TASK_RUNNING);
	return iocb->ki_user_data;
}

/* exit_aio: called when the last user of mm goes away.  At this point, 
 * there is no way for any new requests to be submited or any of the 
 * io_* syscalls to be called on the context.  However, there may be 
 * outstanding requests which hold references to the context; as they 
 * go away, they will call put_ioctx and release any pinned memory
 * associated with the request (held via struct page * references).
 */
void fastcall exit_aio(struct mm_struct *mm)
{
	struct kioctx *ctx = mm->ioctx_list;
	mm->ioctx_list = NULL;
	while (ctx) {
		struct kioctx *next = ctx->next;
		ctx->next = NULL;
		aio_cancel_all(ctx);

		wait_for_all_aios(ctx);
		/*
		 * this is an overkill, but ensures we don't leave
		 * the ctx on the aio_wq
		 */
		flush_workqueue(aio_wq);

		if (1 != atomic_read(&ctx->users))
			printk(KERN_DEBUG
				"exit_aio:ioctx still alive: %d %d %d\n",
				atomic_read(&ctx->users), ctx->dead,
				ctx->reqs_active);
		put_ioctx(ctx);
		ctx = next;
	}
}

/* __put_ioctx
 *	Called when the last user of an aio context has gone away,
 *	and the struct needs to be freed.
 */
void fastcall __put_ioctx(struct kioctx *ctx)
{
	unsigned nr_events = ctx->max_reqs;

	if (unlikely(ctx->reqs_active))
		BUG();

	cancel_delayed_work(&ctx->wq);
	flush_workqueue(aio_wq);
	aio_free_ring(ctx);
	mmdrop(ctx->mm);
	ctx->mm = NULL;
	pr_debug("__put_ioctx: freeing %p\n", ctx);
	kmem_cache_free(kioctx_cachep, ctx);

	if (nr_events) {
		spin_lock(&aio_nr_lock);
		BUG_ON(aio_nr - nr_events > aio_nr);
		aio_nr -= nr_events;
		spin_unlock(&aio_nr_lock);
	}
}

/* aio_get_req
 *	Allocate a slot for an aio request.  Increments the users count
 * of the kioctx so that the kioctx stays around until all requests are
 * complete.  Returns NULL if no requests are free.
 *
 * Returns with kiocb->users set to 2.  The io submit code path holds
 * an extra reference while submitting the i/o.
 * This prevents races between the aio code path referencing the
 * req (after submitting it) and aio_complete() freeing the req.
 */
static struct kiocb *FASTCALL(__aio_get_req(struct kioctx *ctx));
static struct kiocb fastcall *__aio_get_req(struct kioctx *ctx)
{
	struct kiocb *req = NULL;
	struct aio_ring *ring;
	int okay = 0;

	req = kmem_cache_alloc(kiocb_cachep, GFP_KERNEL);
	if (unlikely(!req))
		return NULL;

	req->ki_flags = 0;
	req->ki_users = 2;
	req->ki_key = 0;
	req->ki_ctx = ctx;
	req->ki_cancel = NULL;
	req->ki_retry = NULL;
	req->ki_dtor = NULL;
	req->private = NULL;
	INIT_LIST_HEAD(&req->ki_run_list);

	/* Check if the completion queue has enough free space to
	 * accept an event from this io.
	 */
	spin_lock_irq(&ctx->ctx_lock);
	ring = kmap_atomic(ctx->ring_info.ring_pages[0], KM_USER0);
	if (ctx->reqs_active < aio_ring_avail(&ctx->ring_info, ring)) {
		list_add(&req->ki_list, &ctx->active_reqs);
		get_ioctx(ctx);
		ctx->reqs_active++;
		okay = 1;
	}
	kunmap_atomic(ring, KM_USER0);
	spin_unlock_irq(&ctx->ctx_lock);

	if (!okay) {
		kmem_cache_free(kiocb_cachep, req);
		req = NULL;
	}

	return req;
}

static inline struct kiocb *aio_get_req(struct kioctx *ctx)
{
	struct kiocb *req;
	/* Handle a potential starvation case -- should be exceedingly rare as 
	 * requests will be stuck on fput_head only if the aio_fput_routine is 
	 * delayed and the requests were the last user of the struct file.
	 */
	req = __aio_get_req(ctx);
	if (unlikely(NULL == req)) {
		aio_fput_routine(NULL);
		req = __aio_get_req(ctx);
	}
	return req;
}

static inline void really_put_req(struct kioctx *ctx, struct kiocb *req)
{
	assert_spin_locked(&ctx->ctx_lock);

	if (req->ki_dtor)
		req->ki_dtor(req);
	kmem_cache_free(kiocb_cachep, req);
	ctx->reqs_active--;

	if (unlikely(!ctx->reqs_active && ctx->dead))
		wake_up(&ctx->wait);
}

static void aio_fput_routine(void *data)
{
	spin_lock_irq(&fput_lock);
	while (likely(!list_empty(&fput_head))) {
		struct kiocb *req = list_kiocb(fput_head.next);
		struct kioctx *ctx = req->ki_ctx;

		list_del(&req->ki_list);
		spin_unlock_irq(&fput_lock);

		/* Complete the fput */
		__fput(req->ki_filp);

		/* Link the iocb into the context's free list */
		spin_lock_irq(&ctx->ctx_lock);
		really_put_req(ctx, req);
		spin_unlock_irq(&ctx->ctx_lock);

		put_ioctx(ctx);
		spin_lock_irq(&fput_lock);
	}
	spin_unlock_irq(&fput_lock);
}

/* __aio_put_req
 *	Returns true if this put was the last user of the request.
 */
static int __aio_put_req(struct kioctx *ctx, struct kiocb *req)
{
	dprintk(KERN_DEBUG "aio_put(%p): f_count=%d\n",
		req, atomic_read(&req->ki_filp->f_count));

	assert_spin_locked(&ctx->ctx_lock);

	req->ki_users --;
	if (unlikely(req->ki_users < 0))
		BUG();
	if (likely(req->ki_users))
		return 0;
	list_del(&req->ki_list);		/* remove from active_reqs */
	req->ki_cancel = NULL;
	req->ki_retry = NULL;

	/* Must be done under the lock to serialise against cancellation.
	 * Call this aio_fput as it duplicates fput via the fput_work.
	 */
	if (unlikely(atomic_dec_and_test(&req->ki_filp->f_count))) {
		get_ioctx(ctx);
		spin_lock(&fput_lock);
		list_add(&req->ki_list, &fput_head);
		spin_unlock(&fput_lock);
		queue_work(aio_wq, &fput_work);
	} else
		really_put_req(ctx, req);
	return 1;
}

/* aio_put_req
 *	Returns true if this put was the last user of the kiocb,
 *	false if the request is still in use.
 */
int fastcall aio_put_req(struct kiocb *req)
{
	struct kioctx *ctx = req->ki_ctx;
	int ret;
	spin_lock_irq(&ctx->ctx_lock);
	ret = __aio_put_req(ctx, req);
	spin_unlock_irq(&ctx->ctx_lock);
	if (ret)
		put_ioctx(ctx);
	return ret;
}

/*	Lookup an ioctx id.  ioctx_list is lockless for reads.
 *	FIXME: this is O(n) and is only suitable for development.
 */
struct kioctx *lookup_ioctx(unsigned long ctx_id)
{
	struct kioctx *ioctx;
	struct mm_struct *mm;

	mm = current->mm;
	read_lock(&mm->ioctx_list_lock);
	for (ioctx = mm->ioctx_list; ioctx; ioctx = ioctx->next)
		if (likely(ioctx->user_id == ctx_id && !ioctx->dead)) {
			get_ioctx(ioctx);
			break;
		}
	read_unlock(&mm->ioctx_list_lock);

	return ioctx;
}

/*
 * use_mm
 *	Makes the calling kernel thread take on the specified
 *	mm context.
 *	Called by the retry thread execute retries within the
 *	iocb issuer's mm context, so that copy_from/to_user
 *	operations work seamlessly for aio.
 *	(Note: this routine is intended to be called only
 *	from a kernel thread context)
 */
static void use_mm(struct mm_struct *mm)
{
	struct mm_struct *active_mm;
	struct task_struct *tsk = current;

	task_lock(tsk);
	tsk->flags |= PF_BORROWED_MM;
	active_mm = tsk->active_mm;
	atomic_inc(&mm->mm_count);
	tsk->mm = mm;
	tsk->active_mm = mm;
	/*
	 * Note that on UML this *requires* PF_BORROWED_MM to be set, otherwise
	 * it won't work. Update it accordingly if you change it here
	 */
	activate_mm(active_mm, mm);
	task_unlock(tsk);

	mmdrop(active_mm);
}

/*
 * unuse_mm
 *	Reverses the effect of use_mm, i.e. releases the
 *	specified mm context which was earlier taken on
 *	by the calling kernel thread
 *	(Note: this routine is intended to be called only
 *	from a kernel thread context)
 *
 * Comments: Called with ctx->ctx_lock held. This nests
 * task_lock instead ctx_lock.
 */
static void unuse_mm(struct mm_struct *mm)
{
	struct task_struct *tsk = current;

	task_lock(tsk);
	tsk->flags &= ~PF_BORROWED_MM;
	tsk->mm = NULL;
	/* active_mm is still 'mm' */
	enter_lazy_tlb(mm, tsk);
	task_unlock(tsk);
}

/*
 * Queue up a kiocb to be retried. Assumes that the kiocb
 * has already been marked as kicked, and places it on
 * the retry run list for the corresponding ioctx, if it
 * isn't already queued. Returns 1 if it actually queued
 * the kiocb (to tell the caller to activate the work
 * queue to process it), or 0, if it found that it was
 * already queued.
 */
static inline int __queue_kicked_iocb(struct kiocb *iocb)
{
	struct kioctx *ctx = iocb->ki_ctx;

	assert_spin_locked(&ctx->ctx_lock);

	if (list_empty(&iocb->ki_run_list)) {
		list_add_tail(&iocb->ki_run_list,
			&ctx->run_list);
		return 1;
	}
	return 0;
}

/* aio_run_iocb
 *	This is the core aio execution routine. It is
 *	invoked both for initial i/o submission and
 *	subsequent retries via the aio_kick_handler.
 *	Expects to be invoked with iocb->ki_ctx->lock
 *	already held. The lock is released and reaquired
 *	as needed during processing.
 *
 * Calls the iocb retry method (already setup for the
 * iocb on initial submission) for operation specific
 * handling, but takes care of most of common retry
 * execution details for a given iocb. The retry method
 * needs to be non-blocking as far as possible, to avoid
 * holding up other iocbs waiting to be serviced by the
 * retry kernel thread.
 *
 * The trickier parts in this code have to do with
 * ensuring that only one retry instance is in progress
 * for a given iocb at any time. Providing that guarantee
 * simplifies the coding of individual aio operations as
 * it avoids various potential races.
 */
static ssize_t aio_run_iocb(struct kiocb *iocb)
{
	struct kioctx	*ctx = iocb->ki_ctx;
	ssize_t (*retry)(struct kiocb *);
	ssize_t ret;

	if (iocb->ki_retried++ > 1024*1024) {
		printk("Maximal retry count.  Bytes done %Zd\n",
			iocb->ki_nbytes - iocb->ki_left);
		return -EAGAIN;
	}

	if (!(iocb->ki_retried & 0xff)) {
		pr_debug("%ld retry: %d of %d\n", iocb->ki_retried,
			iocb->ki_nbytes - iocb->ki_left, iocb->ki_nbytes);
	}

	if (!(retry = iocb->ki_retry)) {
		printk("aio_run_iocb: iocb->ki_retry = NULL\n");
		return 0;
	}

	/*
	 * We don't want the next retry iteration for this
	 * operation to start until this one has returned and
	 * updated the iocb state. However, wait_queue functions
	 * can trigger a kick_iocb from interrupt context in the
	 * meantime, indicating that data is available for the next
	 * iteration. We want to remember that and enable the
	 * next retry iteration _after_ we are through with
	 * this one.
	 *
	 * So, in order to be able to register a "kick", but
	 * prevent it from being queued now, we clear the kick
	 * flag, but make the kick code *think* that the iocb is
	 * still on the run list until we are actually done.
	 * When we are done with this iteration, we check if
	 * the iocb was kicked in the meantime and if so, queue
	 * it up afresh.
	 */

	kiocbClearKicked(iocb);

	/*
	 * This is so that aio_complete knows it doesn't need to
	 * pull the iocb off the run list (We can't just call
	 * INIT_LIST_HEAD because we don't want a kick_iocb to
	 * queue this on the run list yet)
	 */
	iocb->ki_run_list.next = iocb->ki_run_list.prev = NULL;
	spin_unlock_irq(&ctx->ctx_lock);

	/* Quit retrying if the i/o has been cancelled */
	if (kiocbIsCancelled(iocb)) {
		ret = -EINTR;
		aio_complete(iocb, ret, 0);
		/* must not access the iocb after this */
		goto out;
	}

	/*
	 * Now we are all set to call the retry method in async
	 * context. By setting this thread's io_wait context
	 * to point to the wait queue entry inside the currently
	 * running iocb for the duration of the retry, we ensure
	 * that async notification wakeups are queued by the
	 * operation instead of blocking waits, and when notified,
	 * cause the iocb to be kicked for continuation (through
	 * the aio_wake_function callback).
	 */
	BUG_ON(current->io_wait != NULL);
	current->io_wait = &iocb->ki_wait;
	ret = retry(iocb);
	current->io_wait = NULL;

	if (ret != -EIOCBRETRY && ret != -EIOCBQUEUED) {
		BUG_ON(!list_empty(&iocb->ki_wait.task_list));
		aio_complete(iocb, ret, 0);
	}
out:
	spin_lock_irq(&ctx->ctx_lock);

	if (-EIOCBRETRY == ret) {
		/*
		 * OK, now that we are done with this iteration
		 * and know that there is more left to go,
		 * this is where we let go so that a subsequent
		 * "kick" can start the next iteration
		 */

		/* will make __queue_kicked_iocb succeed from here on */
		INIT_LIST_HEAD(&iocb->ki_run_list);
		/* we must queue the next iteration ourselves, if it
		 * has already been kicked */
		if (kiocbIsKicked(iocb)) {
			__queue_kicked_iocb(iocb);

			/*
			 * __queue_kicked_iocb will always return 1 here, because
			 * iocb->ki_run_list is empty at this point so it should
			 * be safe to unconditionally queue the context into the
			 * work queue.
			 */
			aio_queue_work(ctx);
		}
	}
	return ret;
}

/*
 * __aio_run_iocbs:
 * 	Process all pending retries queued on the ioctx
 * 	run list.
 * Assumes it is operating within the aio issuer's mm
 * context.
 */
static int __aio_run_iocbs(struct kioctx *ctx)
{
	struct kiocb *iocb;
	LIST_HEAD(run_list);

	assert_spin_locked(&ctx->ctx_lock);

	list_splice_init(&ctx->run_list, &run_list);
	while (!list_empty(&run_list)) {
		iocb = list_entry(run_list.next, struct kiocb,
			ki_run_list);
		list_del(&iocb->ki_run_list);
		/*
		 * Hold an extra reference while retrying i/o.
		 */
		iocb->ki_users++;       /* grab extra reference */
		aio_run_iocb(iocb);
		if (__aio_put_req(ctx, iocb))  /* drop extra ref */
			put_ioctx(ctx);
 	}
	if (!list_empty(&ctx->run_list))
		return 1;
	return 0;
}

static void aio_queue_work(struct kioctx * ctx)
{
	unsigned long timeout;
	/*
	 * if someone is waiting, get the work started right
	 * away, otherwise, use a longer delay
	 */
	smp_mb();
	if (waitqueue_active(&ctx->wait))
		timeout = 1;
	else
		timeout = HZ/10;
	queue_delayed_work(aio_wq, &ctx->wq, timeout);
}


/*
 * aio_run_iocbs:
 * 	Process all pending retries queued on the ioctx
 * 	run list.
 * Assumes it is operating within the aio issuer's mm
 * context.
 */
static inline void aio_run_iocbs(struct kioctx *ctx)
{
	int requeue;

	spin_lock_irq(&ctx->ctx_lock);

	requeue = __aio_run_iocbs(ctx);
	spin_unlock_irq(&ctx->ctx_lock);
	if (requeue)
		aio_queue_work(ctx);
}

/*
 * just like aio_run_iocbs, but keeps running them until
 * the list stays empty
 */
static inline void aio_run_all_iocbs(struct kioctx *ctx)
{
	spin_lock_irq(&ctx->ctx_lock);
	while (__aio_run_iocbs(ctx))
		;
	spin_unlock_irq(&ctx->ctx_lock);
}

/*
 * aio_kick_handler:
 * 	Work queue handler triggered to process pending
 * 	retries on an ioctx. Takes on the aio issuer's
 *	mm context before running the iocbs, so that
 *	copy_xxx_user operates on the issuer's address
 *      space.
 * Run on aiod's context.
 */
static void aio_kick_handler(void *data)
{
	struct kioctx *ctx = data;
	mm_segment_t oldfs = get_fs();
	int requeue;

	set_fs(USER_DS);
	use_mm(ctx->mm);
	spin_lock_irq(&ctx->ctx_lock);
	requeue =__aio_run_iocbs(ctx);
 	unuse_mm(ctx->mm);
	spin_unlock_irq(&ctx->ctx_lock);
	set_fs(oldfs);
	/*
	 * we're in a worker thread already, don't use queue_delayed_work,
	 */
	if (requeue)
		queue_work(aio_wq, &ctx->wq);
}


/*
 * Called by kick_iocb to queue the kiocb for retry
 * and if required activate the aio work queue to process
 * it
 */
static void try_queue_kicked_iocb(struct kiocb *iocb)
{
 	struct kioctx	*ctx = iocb->ki_ctx;
	unsigned long flags;
	int run = 0;

	/* We're supposed to be the only path putting the iocb back on the run
	 * list.  If we find that the iocb is *back* on a wait queue already
	 * than retry has happened before we could queue the iocb.  This also
	 * means that the retry could have completed and freed our iocb, no
	 * good. */
	BUG_ON((!list_empty(&iocb->ki_wait.task_list)));

	spin_lock_irqsave(&ctx->ctx_lock, flags);
	/* set this inside the lock so that we can't race with aio_run_iocb()
	 * testing it and putting the iocb on the run list under the lock */
	if (!kiocbTryKick(iocb))
		run = __queue_kicked_iocb(iocb);
	spin_unlock_irqrestore(&ctx->ctx_lock, flags);
	if (run)
		aio_queue_work(ctx);
}

/*
 * kick_iocb:
 *      Called typically from a wait queue callback context
 *      (aio_wake_function) to trigger a retry of the iocb.
 *      The retry is usually executed by aio workqueue
 *      threads (See aio_kick_handler).
 */
void fastcall kick_iocb(struct kiocb *iocb)
{
	/* sync iocbs are easy: they can only ever be executing from a 
	 * single context. */
	if (is_sync_kiocb(iocb)) {
		kiocbSetKicked(iocb);
	        wake_up_process(iocb->ki_obj.tsk);
		return;
	}

	try_queue_kicked_iocb(iocb);
}
EXPORT_SYMBOL(kick_iocb);

/* aio_complete
 *	Called when the io request on the given iocb is complete.
 *	Returns true if this is the last user of the request.  The 
 *	only other user of the request can be the cancellation code.
 */
int fastcall aio_complete(struct kiocb *iocb, long res, long res2)
{
	struct kioctx	*ctx = iocb->ki_ctx;
	struct aio_ring_info	*info;
	struct aio_ring	*ring;
	struct io_event	*event;
	unsigned long	flags;
	unsigned long	tail;
	int		ret;

	/*
	 * Special case handling for sync iocbs:
	 *  - events go directly into the iocb for fast handling
	 *  - the sync task with the iocb in its stack holds the single iocb
	 *    ref, no other paths have a way to get another ref
	 *  - the sync task helpfully left a reference to itself in the iocb
	 */
	if (is_sync_kiocb(iocb)) {
		BUG_ON(iocb->ki_users != 1);
		iocb->ki_user_data = res;
		iocb->ki_users = 0;
		wake_up_process(iocb->ki_obj.tsk);
		return 1;
	}

	info = &ctx->ring_info;

	/* add a completion event to the ring buffer.
	 * must be done holding ctx->ctx_lock to prevent
	 * other code from messing with the tail
	 * pointer since we might be called from irq
	 * context.
	 */
	spin_lock_irqsave(&ctx->ctx_lock, flags);

	if (iocb->ki_run_list.prev && !list_empty(&iocb->ki_run_list))
		list_del_init(&iocb->ki_run_list);

	/*
	 * cancelled requests don't get events, userland was given one
	 * when the event got cancelled.
	 */
	if (kiocbIsCancelled(iocb))
		goto put_rq;

	ring = kmap_atomic(info->ring_pages[0], KM_IRQ1);

	tail = info->tail;
	event = aio_ring_event(info, tail, KM_IRQ0);
	if (++tail >= info->nr)
		tail = 0;

	event->obj = (u64)(unsigned long)iocb->ki_obj.user;
	event->data = iocb->ki_user_data;
	event->res = res;
	event->res2 = res2;

	dprintk("aio_complete: %p[%lu]: %p: %p %Lx %lx %lx\n",
		ctx, tail, iocb, iocb->ki_obj.user, iocb->ki_user_data,
		res, res2);

	/* after flagging the request as done, we
	 * must never even look at it again
	 */
	smp_wmb();	/* make event visible before updating tail */

	info->tail = tail;
	ring->tail = tail;

	put_aio_ring_event(event, KM_IRQ0);
	kunmap_atomic(ring, KM_IRQ1);

	pr_debug("added to ring %p at [%lu]\n", iocb, tail);

	pr_debug("%ld retries: %d of %d\n", iocb->ki_retried,
		iocb->ki_nbytes - iocb->ki_left, iocb->ki_nbytes);
put_rq:
	/* everything turned out well, dispose of the aiocb. */
	ret = __aio_put_req(ctx, iocb);

	spin_unlock_irqrestore(&ctx->ctx_lock, flags);

	if (waitqueue_active(&ctx->wait))
		wake_up(&ctx->wait);

	if (ret)
		put_ioctx(ctx);

	return ret;
}

/* aio_read_evt
 *	Pull an event off of the ioctx's event ring.  Returns the number of 
 *	events fetched (0 or 1 ;-)
 *	FIXME: make this use cmpxchg.
 *	TODO: make the ringbuffer user mmap()able (requires FIXME).
 */
static int aio_read_evt(struct kioctx *ioctx, struct io_event *ent)
{
	struct aio_ring_info *info = &ioctx->ring_info;
	struct aio_ring *ring;
	unsigned long head;
	int ret = 0;

	ring = kmap_atomic(info->ring_pages[0], KM_USER0);
	dprintk("in aio_read_evt h%lu t%lu m%lu\n",
		 (unsigned long)ring->head, (unsigned long)ring->tail,
		 (unsigned long)ring->nr);

	if (ring->head == ring->tail)
		goto out;

	spin_lock(&info->ring_lock);

	head = ring->head % info->nr;
	if (head != ring->tail) {
		struct io_event *evp = aio_ring_event(info, head, KM_USER1);
		*ent = *evp;
		head = (head + 1) % info->nr;
		smp_mb(); /* finish reading the event before updatng the head */
		ring->head = head;
		ret = 1;
		put_aio_ring_event(evp, KM_USER1);
	}
	spin_unlock(&info->ring_lock);

out:
	kunmap_atomic(ring, KM_USER0);
	dprintk("leaving aio_read_evt: %d  h%lu t%lu\n", ret,
		 (unsigned long)ring->head, (unsigned long)ring->tail);
	return ret;
}

struct aio_timeout {
	struct timer_list	timer;
	int			timed_out;
	struct task_struct	*p;
};

static void timeout_func(unsigned long data)
{
	struct aio_timeout *to = (struct aio_timeout *)data;

	to->timed_out = 1;
	wake_up_process(to->p);
}

static inline void init_timeout(struct aio_timeout *to)
{
	init_timer(&to->timer);
	to->timer.data = (unsigned long)to;
	to->timer.function = timeout_func;
	to->timed_out = 0;
	to->p = current;
}

static inline void set_timeout(long start_jiffies, struct aio_timeout *to,
			       const struct timespec *ts)
{
	to->timer.expires = start_jiffies + timespec_to_jiffies(ts);
	if (time_after(to->timer.expires, jiffies))
		add_timer(&to->timer);
	else
		to->timed_out = 1;
}

static inline void clear_timeout(struct aio_timeout *to)
{
	del_singleshot_timer_sync(&to->timer);
}

static int read_events(struct kioctx *ctx,
			long min_nr, long nr,
			struct io_event __user *event,
			struct timespec __user *timeout)
{
	long			start_jiffies = jiffies;
	struct task_struct	*tsk = current;
	DECLARE_WAITQUEUE(wait, tsk);
	int			ret;
	int			i = 0;
	struct io_event		ent;
	struct aio_timeout	to;
	int			retry = 0;

	/* needed to zero any padding within an entry (there shouldn't be 
	 * any, but C is fun!
	 */
	memset(&ent, 0, sizeof(ent));
retry:
	ret = 0;
	while (likely(i < nr)) {
		ret = aio_read_evt(ctx, &ent);
		if (unlikely(ret <= 0))
			break;

		dprintk("read event: %Lx %Lx %Lx %Lx\n",
			ent.data, ent.obj, ent.res, ent.res2);

		/* Could we split the check in two? */
		ret = -EFAULT;
		if (unlikely(copy_to_user(event, &ent, sizeof(ent)))) {
			dprintk("aio: lost an event due to EFAULT.\n");
			break;
		}
		ret = 0;

		/* Good, event copied to userland, update counts. */
		event ++;
		i ++;
	}

	if (min_nr <= i)
		return i;
	if (ret)
		return ret;

	/* End fast path */

	/* racey check, but it gets redone */
	if (!retry && unlikely(!list_empty(&ctx->run_list))) {
		retry = 1;
		aio_run_all_iocbs(ctx);
		goto retry;
	}

	init_timeout(&to);
	if (timeout) {
		struct timespec	ts;
		ret = -EFAULT;
		if (unlikely(copy_from_user(&ts, timeout, sizeof(ts))))
			goto out;

		set_timeout(start_jiffies, &to, &ts);
	}

	while (likely(i < nr)) {
		add_wait_queue_exclusive(&ctx->wait, &wait);
		do {
			set_task_state(tsk, TASK_INTERRUPTIBLE);
			ret = aio_read_evt(ctx, &ent);
			if (ret)
				break;
			if (min_nr <= i)
				break;
			ret = 0;
			if (to.timed_out)	/* Only check after read evt */
				break;
			schedule();
			if (signal_pending(tsk)) {
				ret = -EINTR;
				break;
			}
			/*ret = aio_read_evt(ctx, &ent);*/
		} while (1) ;

		set_task_state(tsk, TASK_RUNNING);
		remove_wait_queue(&ctx->wait, &wait);

		if (unlikely(ret <= 0))
			break;

		ret = -EFAULT;
		if (unlikely(copy_to_user(event, &ent, sizeof(ent)))) {
			dprintk("aio: lost an event due to EFAULT.\n");
			break;
		}

		/* Good, event copied to userland, update counts. */
		event ++;
		i ++;
	}

	if (timeout)
		clear_timeout(&to);
out:
	return i ? i : ret;
}

/* Take an ioctx and remove it from the list of ioctx's.  Protects 
 * against races with itself via ->dead.
 */
static void io_destroy(struct kioctx *ioctx)
{
	struct mm_struct *mm = current->mm;
	struct kioctx **tmp;
	int was_dead;

	/* delete the entry from the list is someone else hasn't already */
	write_lock(&mm->ioctx_list_lock);
	was_dead = ioctx->dead;
	ioctx->dead = 1;
	for (tmp = &mm->ioctx_list; *tmp && *tmp != ioctx;
	     tmp = &(*tmp)->next)
		;
	if (*tmp)
		*tmp = ioctx->next;
	write_unlock(&mm->ioctx_list_lock);

	dprintk("aio_release(%p)\n", ioctx);
	if (likely(!was_dead))
		put_ioctx(ioctx);	/* twice for the list */

	aio_cancel_all(ioctx);
	wait_for_all_aios(ioctx);
	put_ioctx(ioctx);	/* once for the lookup */
}

/* sys_io_setup:
 *	Create an aio_context capable of receiving at least nr_events.
 *	ctxp must not point to an aio_context that already exists, and
 *	must be initialized to 0 prior to the call.  On successful
 *	creation of the aio_context, *ctxp is filled in with the resulting 
 *	handle.  May fail with -EINVAL if *ctxp is not initialized,
 *	if the specified nr_events exceeds internal limits.  May fail 
 *	with -EAGAIN if the specified nr_events exceeds the user's limit 
 *	of available events.  May fail with -ENOMEM if insufficient kernel
 *	resources are available.  May fail with -EFAULT if an invalid
 *	pointer is passed for ctxp.  Will fail with -ENOSYS if not
 *	implemented.
 */
asmlinkage long sys_io_setup(unsigned nr_events, aio_context_t __user *ctxp)
{
	struct kioctx *ioctx = NULL;
	unsigned long ctx;
	long ret;

	ret = get_user(ctx, ctxp);
	if (unlikely(ret))
		goto out;

	ret = -EINVAL;
	if (unlikely(ctx || nr_events == 0)) {
		pr_debug("EINVAL: io_setup: ctx %lu nr_events %u\n",
		         ctx, nr_events);
		goto out;
	}

	ioctx = ioctx_alloc(nr_events);
	ret = PTR_ERR(ioctx);
	if (!IS_ERR(ioctx)) {
		ret = put_user(ioctx->user_id, ctxp);
		if (!ret)
			return 0;

		get_ioctx(ioctx); /* io_destroy() expects us to hold a ref */
		io_destroy(ioctx);
	}

out:
	return ret;
}

/* sys_io_destroy:
 *	Destroy the aio_context specified.  May cancel any outstanding 
 *	AIOs and block on completion.  Will fail with -ENOSYS if not
 *	implemented.  May fail with -EFAULT if the context pointed to
 *	is invalid.
 */
asmlinkage long sys_io_destroy(aio_context_t ctx)
{
	struct kioctx *ioctx = lookup_ioctx(ctx);
	if (likely(NULL != ioctx)) {
		io_destroy(ioctx);
		return 0;
	}
	pr_debug("EINVAL: io_destroy: invalid context id\n");
	return -EINVAL;
}

/*
 * aio_p{read,write} are the default  ki_retry methods for
 * IO_CMD_P{READ,WRITE}.  They maintains kiocb retry state around potentially
 * multiple calls to f_op->aio_read().  They loop around partial progress
 * instead of returning -EIOCBRETRY because they don't have the means to call
 * kick_iocb().
 */
static ssize_t aio_pread(struct kiocb *iocb)
{
	struct file *file = iocb->ki_filp;
	struct address_space *mapping = file->f_mapping;
	struct inode *inode = mapping->host;
	ssize_t ret = 0;

	do {
		ret = file->f_op->aio_read(iocb, iocb->ki_buf,
			iocb->ki_left, iocb->ki_pos);
		/*
		 * Can't just depend on iocb->ki_left to determine
		 * whether we are done. This may have been a short read.
		 */
		if (ret > 0) {
			iocb->ki_buf += ret;
			iocb->ki_left -= ret;
		}

		/*
		 * For pipes and sockets we return once we have some data; for
		 * regular files we retry till we complete the entire read or
		 * find that we can't read any more data (e.g short reads).
		 */
	} while (ret > 0 && iocb->ki_left > 0 &&
		 !S_ISFIFO(inode->i_mode) && !S_ISSOCK(inode->i_mode));

	/* This means we must have transferred all that we could */
	/* No need to retry anymore */
	if ((ret == 0) || (iocb->ki_left == 0))
		ret = iocb->ki_nbytes - iocb->ki_left;

	return ret;
}

/* see aio_pread() */
static ssize_t aio_pwrite(struct kiocb *iocb)
{
	struct file *file = iocb->ki_filp;
	ssize_t ret = 0;

	do {
		ret = file->f_op->aio_write(iocb, iocb->ki_buf,
			iocb->ki_left, iocb->ki_pos);
		if (ret > 0) {
			iocb->ki_buf += ret;
			iocb->ki_left -= ret;
		}
	} while (ret > 0 && iocb->ki_left > 0);

	if ((ret == 0) || (iocb->ki_left == 0))
		ret = iocb->ki_nbytes - iocb->ki_left;

	return ret;
}

static ssize_t aio_fdsync(struct kiocb *iocb)
{
	struct file *file = iocb->ki_filp;
	ssize_t ret = -EINVAL;

	if (file->f_op->aio_fsync)
		ret = file->f_op->aio_fsync(iocb, 1);
	return ret;
}

static ssize_t aio_fsync(struct kiocb *iocb)
{
	struct file *file = iocb->ki_filp;
	ssize_t ret = -EINVAL;

	if (file->f_op->aio_fsync)
		ret = file->f_op->aio_fsync(iocb, 0);
	return ret;
}

/*
 * aio_setup_iocb:
 *	Performs the initial checks and aio retry method
 *	setup for the kiocb at the time of io submission.
 */
static ssize_t aio_setup_iocb(struct kiocb *kiocb)
{
	struct file *file = kiocb->ki_filp;
	ssize_t ret = 0;

	switch (kiocb->ki_opcode) {
	case IOCB_CMD_PREAD:
		ret = -EBADF;
		if (unlikely(!(file->f_mode & FMODE_READ)))
			break;
		ret = -EFAULT;
		if (unlikely(!access_ok(VERIFY_WRITE, kiocb->ki_buf,
			kiocb->ki_left)))
			break;
		ret = security_file_permission(file, MAY_READ);
		if (unlikely(ret))
			break;
		ret = -EINVAL;
		if (file->f_op->aio_read)
			kiocb->ki_retry = aio_pread;
		break;
	case IOCB_CMD_PWRITE:
		ret = -EBADF;
		if (unlikely(!(file->f_mode & FMODE_WRITE)))
			break;
		ret = -EFAULT;
		if (unlikely(!access_ok(VERIFY_READ, kiocb->ki_buf,
			kiocb->ki_left)))
			break;
		ret = security_file_permission(file, MAY_WRITE);
		if (unlikely(ret))
			break;
		ret = -EINVAL;
		if (file->f_op->aio_write)
			kiocb->ki_retry = aio_pwrite;
		break;
	case IOCB_CMD_FDSYNC:
		ret = -EINVAL;
		if (file->f_op->aio_fsync)
			kiocb->ki_retry = aio_fdsync;
		break;
	case IOCB_CMD_FSYNC:
		ret = -EINVAL;
		if (file->f_op->aio_fsync)
			kiocb->ki_retry = aio_fsync;
		break;
	default:
		dprintk("EINVAL: io_submit: no operation provided\n");
		ret = -EINVAL;
	}

	if (!kiocb->ki_retry)
		return ret;

	return 0;
}

/*
 * aio_wake_function:
 * 	wait queue callback function for aio notification,
 * 	Simply triggers a retry of the operation via kick_iocb.
 *
 * 	This callback is specified in the wait queue entry in
 *	a kiocb	(current->io_wait points to this wait queue
 *	entry when an aio operation executes; it is used
 * 	instead of a synchronous wait when an i/o blocking
 *	condition is encountered during aio).
 *
 * Note:
 * This routine is executed with the wait queue lock held.
 * Since kick_iocb acquires iocb->ctx->ctx_lock, it nests
 * the ioctx lock inside the wait queue lock. This is safe
 * because this callback isn't used for wait queues which
 * are nested inside ioctx lock (i.e. ctx->wait)
 */
static int aio_wake_function(wait_queue_t *wait, unsigned mode,
			     int sync, void *key)
{
	struct kiocb *iocb = container_of(wait, struct kiocb, ki_wait);

	list_del_init(&wait->task_list);
	kick_iocb(iocb);
	return 1;
}

int fastcall io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
			 struct iocb *iocb)
{
	struct kiocb *req;
	struct file *file;
	ssize_t ret;

	/* enforce forwards compatibility on users */
	if (unlikely(iocb->aio_reserved1 || iocb->aio_reserved2 ||
		     iocb->aio_reserved3)) {
		pr_debug("EINVAL: io_submit: reserve field set\n");
		return -EINVAL;
	}

	/* prevent overflows */
	if (unlikely(
	    (iocb->aio_buf != (unsigned long)iocb->aio_buf) ||
	    (iocb->aio_nbytes != (size_t)iocb->aio_nbytes) ||
	    ((ssize_t)iocb->aio_nbytes < 0)
	   )) {
		pr_debug("EINVAL: io_submit: overflow check\n");
		return -EINVAL;
	}

	file = fget(iocb->aio_fildes);
	if (unlikely(!file))
		return -EBADF;

	req = aio_get_req(ctx);		/* returns with 2 references to req */
	if (unlikely(!req)) {
		fput(file);
		return -EAGAIN;
	}

	req->ki_filp = file;
	ret = put_user(req->ki_key, &user_iocb->aio_key);
	if (unlikely(ret)) {
		dprintk("EFAULT: aio_key\n");
		goto out_put_req;
	}

	req->ki_obj.user = user_iocb;
	req->ki_user_data = iocb->aio_data;
	req->ki_pos = iocb->aio_offset;

	req->ki_buf = (char __user *)(unsigned long)iocb->aio_buf;
	req->ki_left = req->ki_nbytes = iocb->aio_nbytes;
	req->ki_opcode = iocb->aio_lio_opcode;
	init_waitqueue_func_entry(&req->ki_wait, aio_wake_function);
	INIT_LIST_HEAD(&req->ki_wait.task_list);
	req->ki_retried = 0;

	ret = aio_setup_iocb(req);

	if (ret)
		goto out_put_req;

	spin_lock_irq(&ctx->ctx_lock);
	aio_run_iocb(req);
	if (!list_empty(&ctx->run_list)) {
		/* drain the run list */
		while (__aio_run_iocbs(ctx))
			;
	}
	spin_unlock_irq(&ctx->ctx_lock);
	aio_put_req(req);	/* drop extra ref to req */
	return 0;

out_put_req:
	aio_put_req(req);	/* drop extra ref to req */
	aio_put_req(req);	/* drop i/o ref to req */
	return ret;
}

/* sys_io_submit:
 *	Queue the nr iocbs pointed to by iocbpp for processing.  Returns
 *	the number of iocbs queued.  May return -EINVAL if the aio_context
 *	specified by ctx_id is invalid, if nr is < 0, if the iocb at
 *	*iocbpp[0] is not properly initialized, if the operation specified
 *	is invalid for the file descriptor in the iocb.  May fail with
 *	-EFAULT if any of the data structures point to invalid data.  May
 *	fail with -EBADF if the file descriptor specified in the first
 *	iocb is invalid.  May fail with -EAGAIN if insufficient resources
 *	are available to queue any iocbs.  Will return 0 if nr is 0.  Will
 *	fail with -ENOSYS if not implemented.
 */
asmlinkage long sys_io_submit(aio_context_t ctx_id, long nr,
			      struct iocb __user * __user *iocbpp)
{
	struct kioctx *ctx;
	long ret = 0;
	int i;

	if (unlikely(nr < 0))
		return -EINVAL;

	if (unlikely(!access_ok(VERIFY_READ, iocbpp, (nr*sizeof(*iocbpp)))))
		return -EFAULT;

	ctx = lookup_ioctx(ctx_id);
	if (unlikely(!ctx)) {
		pr_debug("EINVAL: io_submit: invalid context id\n");
		return -EINVAL;
	}

	/*
	 * AKPM: should this return a partial result if some of the IOs were
	 * successfully submitted?
	 */
	for (i=0; i<nr; i++) {
		struct iocb __user *user_iocb;
		struct iocb tmp;

		if (unlikely(__get_user(user_iocb, iocbpp + i))) {
			ret = -EFAULT;
			break;
		}

		if (unlikely(copy_from_user(&tmp, user_iocb, sizeof(tmp)))) {
			ret = -EFAULT;
			break;
		}

		ret = io_submit_one(ctx, user_iocb, &tmp);
		if (ret)
			break;
	}

	put_ioctx(ctx);
	return i ? i : ret;
}

/* lookup_kiocb
 *	Finds a given iocb for cancellation.
 */
static struct kiocb *lookup_kiocb(struct kioctx *ctx, struct iocb __user *iocb,
				  u32 key)
{
	struct list_head *pos;

	assert_spin_locked(&ctx->ctx_lock);

	/* TODO: use a hash or array, this sucks. */
	list_for_each(pos, &ctx->active_reqs) {
		struct kiocb *kiocb = list_kiocb(pos);
		if (kiocb->ki_obj.user == iocb && kiocb->ki_key == key)
			return kiocb;
	}
	return NULL;
}

/* sys_io_cancel:
 *	Attempts to cancel an iocb previously passed to io_submit.  If
 *	the operation is successfully cancelled, the resulting event is
 *	copied into the memory pointed to by result without being placed
 *	into the completion queue and 0 is returned.  May fail with
 *	-EFAULT if any of the data structures pointed to are invalid.
 *	May fail with -EINVAL if aio_context specified by ctx_id is
 *	invalid.  May fail with -EAGAIN if the iocb specified was not
 *	cancelled.  Will fail with -ENOSYS if not implemented.
 */
asmlinkage long sys_io_cancel(aio_context_t ctx_id, struct iocb __user *iocb,
			      struct io_event __user *result)
{
	int (*cancel)(struct kiocb *iocb, struct io_event *res);
	struct kioctx *ctx;
	struct kiocb *kiocb;
	u32 key;
	int ret;

	ret = get_user(key, &iocb->aio_key);
	if (unlikely(ret))
		return -EFAULT;

	ctx = lookup_ioctx(ctx_id);
	if (unlikely(!ctx))
		return -EINVAL;

	spin_lock_irq(&ctx->ctx_lock);
	ret = -EAGAIN;
	kiocb = lookup_kiocb(ctx, iocb, key);
	if (kiocb && kiocb->ki_cancel) {
		cancel = kiocb->ki_cancel;
		kiocb->ki_users ++;
		kiocbSetCancelled(kiocb);
	} else
		cancel = NULL;
	spin_unlock_irq(&ctx->ctx_lock);

	if (NULL != cancel) {
		struct io_event tmp;
		pr_debug("calling cancel\n");
		memset(&tmp, 0, sizeof(tmp));
		tmp.obj = (u64)(unsigned long)kiocb->ki_obj.user;
		tmp.data = kiocb->ki_user_data;
		ret = cancel(kiocb, &tmp);
		if (!ret) {
			/* Cancellation succeeded -- copy the result
			 * into the user's buffer.
			 */
			if (copy_to_user(result, &tmp, sizeof(tmp)))
				ret = -EFAULT;
		}
	} else
		ret = -EINVAL;

	put_ioctx(ctx);

	return ret;
}

/* io_getevents:
 *	Attempts to read at least min_nr events and up to nr events from
 *	the completion queue for the aio_context specified by ctx_id.  May
 *	fail with -EINVAL if ctx_id is invalid, if min_nr is out of range,
 *	if nr is out of range, if when is out of range.  May fail with
 *	-EFAULT if any of the memory specified to is invalid.  May return
 *	0 or < min_nr if no events are available and the timeout specified
 *	by when	has elapsed, where when == NULL specifies an infinite
 *	timeout.  Note that the timeout pointed to by when is relative and
 *	will be updated if not NULL and the operation blocks.  Will fail
 *	with -ENOSYS if not implemented.
 */
asmlinkage long sys_io_getevents(aio_context_t ctx_id,
				 long min_nr,
				 long nr,
				 struct io_event __user *events,
				 struct timespec __user *timeout)
{
	struct kioctx *ioctx = lookup_ioctx(ctx_id);
	long ret = -EINVAL;

	if (likely(ioctx)) {
		if (likely(min_nr <= nr && min_nr >= 0 && nr >= 0))
			ret = read_events(ioctx, min_nr, nr, events, timeout);
		put_ioctx(ioctx);
	}

	return ret;
}

__initcall(aio_setup);

EXPORT_SYMBOL(aio_complete);
EXPORT_SYMBOL(aio_put_req);
EXPORT_SYMBOL(wait_on_sync_kiocb);