summaryrefslogtreecommitdiff
path: root/mm/memory-failure.c
blob: 8a7b39486b9d06451fd679cf1b1bdf1cf4f6119a (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
/*
 * Copyright (C) 2008, 2009 Intel Corporation
 * Authors: Andi Kleen, Fengguang Wu
 *
 * This software may be redistributed and/or modified under the terms of
 * the GNU General Public License ("GPL") version 2 only as published by the
 * Free Software Foundation.
 *
 * High level machine check handler. Handles pages reported by the
 * hardware as being corrupted usually due to a multi-bit ECC memory or cache
 * failure.
 * 
 * In addition there is a "soft offline" entry point that allows stop using
 * not-yet-corrupted-by-suspicious pages without killing anything.
 *
 * Handles page cache pages in various states.	The tricky part
 * here is that we can access any page asynchronously in respect to 
 * other VM users, because memory failures could happen anytime and 
 * anywhere. This could violate some of their assumptions. This is why 
 * this code has to be extremely careful. Generally it tries to use 
 * normal locking rules, as in get the standard locks, even if that means 
 * the error handling takes potentially a long time.
 *
 * It can be very tempting to add handling for obscure cases here.
 * In general any code for handling new cases should only be added iff:
 * - You know how to test it.
 * - You have a test that can be added to mce-test
 *   https://git.kernel.org/cgit/utils/cpu/mce/mce-test.git/
 * - The case actually shows up as a frequent (top 10) page state in
 *   tools/vm/page-types when running a real workload.
 * 
 * There are several operations here with exponential complexity because
 * of unsuitable VM data structures. For example the operation to map back 
 * from RMAP chains to processes has to walk the complete process list and 
 * has non linear complexity with the number. But since memory corruptions
 * are rare we hope to get away with this. This avoids impacting the core 
 * VM.
 */
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/page-flags.h>
#include <linux/kernel-page-flags.h>
#include <linux/sched/signal.h>
#include <linux/sched/task.h>
#include <linux/ksm.h>
#include <linux/rmap.h>
#include <linux/export.h>
#include <linux/pagemap.h>
#include <linux/swap.h>
#include <linux/backing-dev.h>
#include <linux/migrate.h>
#include <linux/suspend.h>
#include <linux/slab.h>
#include <linux/swapops.h>
#include <linux/hugetlb.h>
#include <linux/memory_hotplug.h>
#include <linux/mm_inline.h>
#include <linux/kfifo.h>
#include <linux/ratelimit.h>
#include "internal.h"
#include "ras/ras_event.h"

int sysctl_memory_failure_early_kill __read_mostly = 0;

int sysctl_memory_failure_recovery __read_mostly = 1;

atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0);

#if defined(CONFIG_HWPOISON_INJECT) || defined(CONFIG_HWPOISON_INJECT_MODULE)

u32 hwpoison_filter_enable = 0;
u32 hwpoison_filter_dev_major = ~0U;
u32 hwpoison_filter_dev_minor = ~0U;
u64 hwpoison_filter_flags_mask;
u64 hwpoison_filter_flags_value;
EXPORT_SYMBOL_GPL(hwpoison_filter_enable);
EXPORT_SYMBOL_GPL(hwpoison_filter_dev_major);
EXPORT_SYMBOL_GPL(hwpoison_filter_dev_minor);
EXPORT_SYMBOL_GPL(hwpoison_filter_flags_mask);
EXPORT_SYMBOL_GPL(hwpoison_filter_flags_value);

static int hwpoison_filter_dev(struct page *p)
{
	struct address_space *mapping;
	dev_t dev;

	if (hwpoison_filter_dev_major == ~0U &&
	    hwpoison_filter_dev_minor == ~0U)
		return 0;

	/*
	 * page_mapping() does not accept slab pages.
	 */
	if (PageSlab(p))
		return -EINVAL;

	mapping = page_mapping(p);
	if (mapping == NULL || mapping->host == NULL)
		return -EINVAL;

	dev = mapping->host->i_sb->s_dev;
	if (hwpoison_filter_dev_major != ~0U &&
	    hwpoison_filter_dev_major != MAJOR(dev))
		return -EINVAL;
	if (hwpoison_filter_dev_minor != ~0U &&
	    hwpoison_filter_dev_minor != MINOR(dev))
		return -EINVAL;

	return 0;
}

static int hwpoison_filter_flags(struct page *p)
{
	if (!hwpoison_filter_flags_mask)
		return 0;

	if ((stable_page_flags(p) & hwpoison_filter_flags_mask) ==
				    hwpoison_filter_flags_value)
		return 0;
	else
		return -EINVAL;
}

/*
 * This allows stress tests to limit test scope to a collection of tasks
 * by putting them under some memcg. This prevents killing unrelated/important
 * processes such as /sbin/init. Note that the target task may share clean
 * pages with init (eg. libc text), which is harmless. If the target task
 * share _dirty_ pages with another task B, the test scheme must make sure B
 * is also included in the memcg. At last, due to race conditions this filter
 * can only guarantee that the page either belongs to the memcg tasks, or is
 * a freed page.
 */
#ifdef CONFIG_MEMCG
u64 hwpoison_filter_memcg;
EXPORT_SYMBOL_GPL(hwpoison_filter_memcg);
static int hwpoison_filter_task(struct page *p)
{
	if (!hwpoison_filter_memcg)
		return 0;

	if (page_cgroup_ino(p) != hwpoison_filter_memcg)
		return -EINVAL;

	return 0;
}
#else
static int hwpoison_filter_task(struct page *p) { return 0; }
#endif

int hwpoison_filter(struct page *p)
{
	if (!hwpoison_filter_enable)
		return 0;

	if (hwpoison_filter_dev(p))
		return -EINVAL;

	if (hwpoison_filter_flags(p))
		return -EINVAL;

	if (hwpoison_filter_task(p))
		return -EINVAL;

	return 0;
}
#else
int hwpoison_filter(struct page *p)
{
	return 0;
}
#endif

EXPORT_SYMBOL_GPL(hwpoison_filter);

/*
 * Send all the processes who have the page mapped a signal.
 * ``action optional'' if they are not immediately affected by the error
 * ``action required'' if error happened in current execution context
 */
static int kill_proc(struct task_struct *t, unsigned long addr, int trapno,
			unsigned long pfn, struct page *page, int flags)
{
	struct siginfo si;
	int ret;

	pr_err("Memory failure: %#lx: Killing %s:%d due to hardware memory corruption\n",
		pfn, t->comm, t->pid);
	si.si_signo = SIGBUS;
	si.si_errno = 0;
	si.si_addr = (void *)addr;
#ifdef __ARCH_SI_TRAPNO
	si.si_trapno = trapno;
#endif
	si.si_addr_lsb = compound_order(compound_head(page)) + PAGE_SHIFT;

	if ((flags & MF_ACTION_REQUIRED) && t->mm == current->mm) {
		si.si_code = BUS_MCEERR_AR;
		ret = force_sig_info(SIGBUS, &si, current);
	} else {
		/*
		 * Don't use force here, it's convenient if the signal
		 * can be temporarily blocked.
		 * This could cause a loop when the user sets SIGBUS
		 * to SIG_IGN, but hopefully no one will do that?
		 */
		si.si_code = BUS_MCEERR_AO;
		ret = send_sig_info(SIGBUS, &si, t);  /* synchronous? */
	}
	if (ret < 0)
		pr_info("Memory failure: Error sending signal to %s:%d: %d\n",
			t->comm, t->pid, ret);
	return ret;
}

/*
 * When a unknown page type is encountered drain as many buffers as possible
 * in the hope to turn the page into a LRU or free page, which we can handle.
 */
void shake_page(struct page *p, int access)
{
	if (PageHuge(p))
		return;

	if (!PageSlab(p)) {
		lru_add_drain_all();
		if (PageLRU(p))
			return;
		drain_all_pages(page_zone(p));
		if (PageLRU(p) || is_free_buddy_page(p))
			return;
	}

	/*
	 * Only call shrink_node_slabs here (which would also shrink
	 * other caches) if access is not potentially fatal.
	 */
	if (access)
		drop_slab_node(page_to_nid(p));
}
EXPORT_SYMBOL_GPL(shake_page);

/*
 * Kill all processes that have a poisoned page mapped and then isolate
 * the page.
 *
 * General strategy:
 * Find all processes having the page mapped and kill them.
 * But we keep a page reference around so that the page is not
 * actually freed yet.
 * Then stash the page away
 *
 * There's no convenient way to get back to mapped processes
 * from the VMAs. So do a brute-force search over all
 * running processes.
 *
 * Remember that machine checks are not common (or rather
 * if they are common you have other problems), so this shouldn't
 * be a performance issue.
 *
 * Also there are some races possible while we get from the
 * error detection to actually handle it.
 */

struct to_kill {
	struct list_head nd;
	struct task_struct *tsk;
	unsigned long addr;
	char addr_valid;
};

/*
 * Failure handling: if we can't find or can't kill a process there's
 * not much we can do.	We just print a message and ignore otherwise.
 */

/*
 * Schedule a process for later kill.
 * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
 * TBD would GFP_NOIO be enough?
 */
static void add_to_kill(struct task_struct *tsk, struct page *p,
		       struct vm_area_struct *vma,
		       struct list_head *to_kill,
		       struct to_kill **tkc)
{
	struct to_kill *tk;

	if (*tkc) {
		tk = *tkc;
		*tkc = NULL;
	} else {
		tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
		if (!tk) {
			pr_err("Memory failure: Out of memory while machine check handling\n");
			return;
		}
	}
	tk->addr = page_address_in_vma(p, vma);
	tk->addr_valid = 1;

	/*
	 * In theory we don't have to kill when the page was
	 * munmaped. But it could be also a mremap. Since that's
	 * likely very rare kill anyways just out of paranoia, but use
	 * a SIGKILL because the error is not contained anymore.
	 */
	if (tk->addr == -EFAULT) {
		pr_info("Memory failure: Unable to find user space address %lx in %s\n",
			page_to_pfn(p), tsk->comm);
		tk->addr_valid = 0;
	}
	get_task_struct(tsk);
	tk->tsk = tsk;
	list_add_tail(&tk->nd, to_kill);
}

/*
 * Kill the processes that have been collected earlier.
 *
 * Only do anything when DOIT is set, otherwise just free the list
 * (this is used for clean pages which do not need killing)
 * Also when FAIL is set do a force kill because something went
 * wrong earlier.
 */
static void kill_procs(struct list_head *to_kill, int forcekill, int trapno,
			  bool fail, struct page *page, unsigned long pfn,
			  int flags)
{
	struct to_kill *tk, *next;

	list_for_each_entry_safe (tk, next, to_kill, nd) {
		if (forcekill) {
			/*
			 * In case something went wrong with munmapping
			 * make sure the process doesn't catch the
			 * signal and then access the memory. Just kill it.
			 */
			if (fail || tk->addr_valid == 0) {
				pr_err("Memory failure: %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n",
				       pfn, tk->tsk->comm, tk->tsk->pid);
				force_sig(SIGKILL, tk->tsk);
			}

			/*
			 * In theory the process could have mapped
			 * something else on the address in-between. We could
			 * check for that, but we need to tell the
			 * process anyways.
			 */
			else if (kill_proc(tk->tsk, tk->addr, trapno,
					      pfn, page, flags) < 0)
				pr_err("Memory failure: %#lx: Cannot send advisory machine check signal to %s:%d\n",
				       pfn, tk->tsk->comm, tk->tsk->pid);
		}
		put_task_struct(tk->tsk);
		kfree(tk);
	}
}

/*
 * Find a dedicated thread which is supposed to handle SIGBUS(BUS_MCEERR_AO)
 * on behalf of the thread group. Return task_struct of the (first found)
 * dedicated thread if found, and return NULL otherwise.
 *
 * We already hold read_lock(&tasklist_lock) in the caller, so we don't
 * have to call rcu_read_lock/unlock() in this function.
 */
static struct task_struct *find_early_kill_thread(struct task_struct *tsk)
{
	struct task_struct *t;

	for_each_thread(tsk, t)
		if ((t->flags & PF_MCE_PROCESS) && (t->flags & PF_MCE_EARLY))
			return t;
	return NULL;
}

/*
 * Determine whether a given process is "early kill" process which expects
 * to be signaled when some page under the process is hwpoisoned.
 * Return task_struct of the dedicated thread (main thread unless explicitly
 * specified) if the process is "early kill," and otherwise returns NULL.
 */
static struct task_struct *task_early_kill(struct task_struct *tsk,
					   int force_early)
{
	struct task_struct *t;
	if (!tsk->mm)
		return NULL;
	if (force_early)
		return tsk;
	t = find_early_kill_thread(tsk);
	if (t)
		return t;
	if (sysctl_memory_failure_early_kill)
		return tsk;
	return NULL;
}

/*
 * Collect processes when the error hit an anonymous page.
 */
static void collect_procs_anon(struct page *page, struct list_head *to_kill,
			      struct to_kill **tkc, int force_early)
{
	struct vm_area_struct *vma;
	struct task_struct *tsk;
	struct anon_vma *av;
	pgoff_t pgoff;

	av = page_lock_anon_vma_read(page);
	if (av == NULL)	/* Not actually mapped anymore */
		return;

	pgoff = page_to_pgoff(page);
	read_lock(&tasklist_lock);
	for_each_process (tsk) {
		struct anon_vma_chain *vmac;
		struct task_struct *t = task_early_kill(tsk, force_early);

		if (!t)
			continue;
		anon_vma_interval_tree_foreach(vmac, &av->rb_root,
					       pgoff, pgoff) {
			vma = vmac->vma;
			if (!page_mapped_in_vma(page, vma))
				continue;
			if (vma->vm_mm == t->mm)
				add_to_kill(t, page, vma, to_kill, tkc);
		}
	}
	read_unlock(&tasklist_lock);
	page_unlock_anon_vma_read(av);
}

/*
 * Collect processes when the error hit a file mapped page.
 */
static void collect_procs_file(struct page *page, struct list_head *to_kill,
			      struct to_kill **tkc, int force_early)
{
	struct vm_area_struct *vma;
	struct task_struct *tsk;
	struct address_space *mapping = page->mapping;

	i_mmap_lock_read(mapping);
	read_lock(&tasklist_lock);
	for_each_process(tsk) {
		pgoff_t pgoff = page_to_pgoff(page);
		struct task_struct *t = task_early_kill(tsk, force_early);

		if (!t)
			continue;
		vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff,
				      pgoff) {
			/*
			 * Send early kill signal to tasks where a vma covers
			 * the page but the corrupted page is not necessarily
			 * mapped it in its pte.
			 * Assume applications who requested early kill want
			 * to be informed of all such data corruptions.
			 */
			if (vma->vm_mm == t->mm)
				add_to_kill(t, page, vma, to_kill, tkc);
		}
	}
	read_unlock(&tasklist_lock);
	i_mmap_unlock_read(mapping);
}

/*
 * Collect the processes who have the corrupted page mapped to kill.
 * This is done in two steps for locking reasons.
 * First preallocate one tokill structure outside the spin locks,
 * so that we can kill at least one process reasonably reliable.
 */
static void collect_procs(struct page *page, struct list_head *tokill,
				int force_early)
{
	struct to_kill *tk;

	if (!page->mapping)
		return;

	tk = kmalloc(sizeof(struct to_kill), GFP_NOIO);
	if (!tk)
		return;
	if (PageAnon(page))
		collect_procs_anon(page, tokill, &tk, force_early);
	else
		collect_procs_file(page, tokill, &tk, force_early);
	kfree(tk);
}

static const char *action_name[] = {
	[MF_IGNORED] = "Ignored",
	[MF_FAILED] = "Failed",
	[MF_DELAYED] = "Delayed",
	[MF_RECOVERED] = "Recovered",
};

static const char * const action_page_types[] = {
	[MF_MSG_KERNEL]			= "reserved kernel page",
	[MF_MSG_KERNEL_HIGH_ORDER]	= "high-order kernel page",
	[MF_MSG_SLAB]			= "kernel slab page",
	[MF_MSG_DIFFERENT_COMPOUND]	= "different compound page after locking",
	[MF_MSG_POISONED_HUGE]		= "huge page already hardware poisoned",
	[MF_MSG_HUGE]			= "huge page",
	[MF_MSG_FREE_HUGE]		= "free huge page",
	[MF_MSG_UNMAP_FAILED]		= "unmapping failed page",
	[MF_MSG_DIRTY_SWAPCACHE]	= "dirty swapcache page",
	[MF_MSG_CLEAN_SWAPCACHE]	= "clean swapcache page",
	[MF_MSG_DIRTY_MLOCKED_LRU]	= "dirty mlocked LRU page",
	[MF_MSG_CLEAN_MLOCKED_LRU]	= "clean mlocked LRU page",
	[MF_MSG_DIRTY_UNEVICTABLE_LRU]	= "dirty unevictable LRU page",
	[MF_MSG_CLEAN_UNEVICTABLE_LRU]	= "clean unevictable LRU page",
	[MF_MSG_DIRTY_LRU]		= "dirty LRU page",
	[MF_MSG_CLEAN_LRU]		= "clean LRU page",
	[MF_MSG_TRUNCATED_LRU]		= "already truncated LRU page",
	[MF_MSG_BUDDY]			= "free buddy page",
	[MF_MSG_BUDDY_2ND]		= "free buddy page (2nd try)",
	[MF_MSG_UNKNOWN]		= "unknown page",
};

/*
 * XXX: It is possible that a page is isolated from LRU cache,
 * and then kept in swap cache or failed to remove from page cache.
 * The page count will stop it from being freed by unpoison.
 * Stress tests should be aware of this memory leak problem.
 */
static int delete_from_lru_cache(struct page *p)
{
	if (!isolate_lru_page(p)) {
		/*
		 * Clear sensible page flags, so that the buddy system won't
		 * complain when the page is unpoison-and-freed.
		 */
		ClearPageActive(p);
		ClearPageUnevictable(p);

		/*
		 * Poisoned page might never drop its ref count to 0 so we have
		 * to uncharge it manually from its memcg.
		 */
		mem_cgroup_uncharge(p);

		/*
		 * drop the page count elevated by isolate_lru_page()
		 */
		put_page(p);
		return 0;
	}
	return -EIO;
}

/*
 * Error hit kernel page.
 * Do nothing, try to be lucky and not touch this instead. For a few cases we
 * could be more sophisticated.
 */
static int me_kernel(struct page *p, unsigned long pfn)
{
	return MF_IGNORED;
}

/*
 * Page in unknown state. Do nothing.
 */
static int me_unknown(struct page *p, unsigned long pfn)
{
	pr_err("Memory failure: %#lx: Unknown page state\n", pfn);
	return MF_FAILED;
}

/*
 * Clean (or cleaned) page cache page.
 */
static int me_pagecache_clean(struct page *p, unsigned long pfn)
{
	int err;
	int ret = MF_FAILED;
	struct address_space *mapping;

	delete_from_lru_cache(p);

	/*
	 * For anonymous pages we're done the only reference left
	 * should be the one m_f() holds.
	 */
	if (PageAnon(p))
		return MF_RECOVERED;

	/*
	 * Now truncate the page in the page cache. This is really
	 * more like a "temporary hole punch"
	 * Don't do this for block devices when someone else
	 * has a reference, because it could be file system metadata
	 * and that's not safe to truncate.
	 */
	mapping = page_mapping(p);
	if (!mapping) {
		/*
		 * Page has been teared down in the meanwhile
		 */
		return MF_FAILED;
	}

	/*
	 * Truncation is a bit tricky. Enable it per file system for now.
	 *
	 * Open: to take i_mutex or not for this? Right now we don't.
	 */
	if (mapping->a_ops->error_remove_page) {
		err = mapping->a_ops->error_remove_page(mapping, p);
		if (err != 0) {
			pr_info("Memory failure: %#lx: Failed to punch page: %d\n",
				pfn, err);
		} else if (page_has_private(p) &&
				!try_to_release_page(p, GFP_NOIO)) {
			pr_info("Memory failure: %#lx: failed to release buffers\n",
				pfn);
		} else {
			ret = MF_RECOVERED;
		}
	} else {
		/*
		 * If the file system doesn't support it just invalidate
		 * This fails on dirty or anything with private pages
		 */
		if (invalidate_inode_page(p))
			ret = MF_RECOVERED;
		else
			pr_info("Memory failure: %#lx: Failed to invalidate\n",
				pfn);
	}
	return ret;
}

/*
 * Dirty pagecache page
 * Issues: when the error hit a hole page the error is not properly
 * propagated.
 */
static int me_pagecache_dirty(struct page *p, unsigned long pfn)
{
	struct address_space *mapping = page_mapping(p);

	SetPageError(p);
	/* TBD: print more information about the file. */
	if (mapping) {
		/*
		 * IO error will be reported by write(), fsync(), etc.
		 * who check the mapping.
		 * This way the application knows that something went
		 * wrong with its dirty file data.
		 *
		 * There's one open issue:
		 *
		 * The EIO will be only reported on the next IO
		 * operation and then cleared through the IO map.
		 * Normally Linux has two mechanisms to pass IO error
		 * first through the AS_EIO flag in the address space
		 * and then through the PageError flag in the page.
		 * Since we drop pages on memory failure handling the
		 * only mechanism open to use is through AS_AIO.
		 *
		 * This has the disadvantage that it gets cleared on
		 * the first operation that returns an error, while
		 * the PageError bit is more sticky and only cleared
		 * when the page is reread or dropped.  If an
		 * application assumes it will always get error on
		 * fsync, but does other operations on the fd before
		 * and the page is dropped between then the error
		 * will not be properly reported.
		 *
		 * This can already happen even without hwpoisoned
		 * pages: first on metadata IO errors (which only
		 * report through AS_EIO) or when the page is dropped
		 * at the wrong time.
		 *
		 * So right now we assume that the application DTRT on
		 * the first EIO, but we're not worse than other parts
		 * of the kernel.
		 */
		mapping_set_error(mapping, -EIO);
	}

	return me_pagecache_clean(p, pfn);
}

/*
 * Clean and dirty swap cache.
 *
 * Dirty swap cache page is tricky to handle. The page could live both in page
 * cache and swap cache(ie. page is freshly swapped in). So it could be
 * referenced concurrently by 2 types of PTEs:
 * normal PTEs and swap PTEs. We try to handle them consistently by calling
 * try_to_unmap(TTU_IGNORE_HWPOISON) to convert the normal PTEs to swap PTEs,
 * and then
 *      - clear dirty bit to prevent IO
 *      - remove from LRU
 *      - but keep in the swap cache, so that when we return to it on
 *        a later page fault, we know the application is accessing
 *        corrupted data and shall be killed (we installed simple
 *        interception code in do_swap_page to catch it).
 *
 * Clean swap cache pages can be directly isolated. A later page fault will
 * bring in the known good data from disk.
 */
static int me_swapcache_dirty(struct page *p, unsigned long pfn)
{
	ClearPageDirty(p);
	/* Trigger EIO in shmem: */
	ClearPageUptodate(p);

	if (!delete_from_lru_cache(p))
		return MF_DELAYED;
	else
		return MF_FAILED;
}

static int me_swapcache_clean(struct page *p, unsigned long pfn)
{
	delete_from_swap_cache(p);

	if (!delete_from_lru_cache(p))
		return MF_RECOVERED;
	else
		return MF_FAILED;
}

/*
 * Huge pages. Needs work.
 * Issues:
 * - Error on hugepage is contained in hugepage unit (not in raw page unit.)
 *   To narrow down kill region to one page, we need to break up pmd.
 */
static int me_huge_page(struct page *p, unsigned long pfn)
{
	int res = 0;
	struct page *hpage = compound_head(p);

	if (!PageHuge(hpage))
		return MF_DELAYED;

	/*
	 * We can safely recover from error on free or reserved (i.e.
	 * not in-use) hugepage by dequeuing it from freelist.
	 * To check whether a hugepage is in-use or not, we can't use
	 * page->lru because it can be used in other hugepage operations,
	 * such as __unmap_hugepage_range() and gather_surplus_pages().
	 * So instead we use page_mapping() and PageAnon().
	 */
	if (!(page_mapping(hpage) || PageAnon(hpage))) {
		res = dequeue_hwpoisoned_huge_page(hpage);
		if (!res)
			return MF_RECOVERED;
	}
	return MF_DELAYED;
}

/*
 * Various page states we can handle.
 *
 * A page state is defined by its current page->flags bits.
 * The table matches them in order and calls the right handler.
 *
 * This is quite tricky because we can access page at any time
 * in its live cycle, so all accesses have to be extremely careful.
 *
 * This is not complete. More states could be added.
 * For any missing state don't attempt recovery.
 */

#define dirty		(1UL << PG_dirty)
#define sc		((1UL << PG_swapcache) | (1UL << PG_swapbacked))
#define unevict		(1UL << PG_unevictable)
#define mlock		(1UL << PG_mlocked)
#define writeback	(1UL << PG_writeback)
#define lru		(1UL << PG_lru)
#define head		(1UL << PG_head)
#define slab		(1UL << PG_slab)
#define reserved	(1UL << PG_reserved)

static struct page_state {
	unsigned long mask;
	unsigned long res;
	enum mf_action_page_type type;
	int (*action)(struct page *p, unsigned long pfn);
} error_states[] = {
	{ reserved,	reserved,	MF_MSG_KERNEL,	me_kernel },
	/*
	 * free pages are specially detected outside this table:
	 * PG_buddy pages only make a small fraction of all free pages.
	 */

	/*
	 * Could in theory check if slab page is free or if we can drop
	 * currently unused objects without touching them. But just
	 * treat it as standard kernel for now.
	 */
	{ slab,		slab,		MF_MSG_SLAB,	me_kernel },

	{ head,		head,		MF_MSG_HUGE,		me_huge_page },

	{ sc|dirty,	sc|dirty,	MF_MSG_DIRTY_SWAPCACHE,	me_swapcache_dirty },
	{ sc|dirty,	sc,		MF_MSG_CLEAN_SWAPCACHE,	me_swapcache_clean },

	{ mlock|dirty,	mlock|dirty,	MF_MSG_DIRTY_MLOCKED_LRU,	me_pagecache_dirty },
	{ mlock|dirty,	mlock,		MF_MSG_CLEAN_MLOCKED_LRU,	me_pagecache_clean },

	{ unevict|dirty, unevict|dirty,	MF_MSG_DIRTY_UNEVICTABLE_LRU,	me_pagecache_dirty },
	{ unevict|dirty, unevict,	MF_MSG_CLEAN_UNEVICTABLE_LRU,	me_pagecache_clean },

	{ lru|dirty,	lru|dirty,	MF_MSG_DIRTY_LRU,	me_pagecache_dirty },
	{ lru|dirty,	lru,		MF_MSG_CLEAN_LRU,	me_pagecache_clean },

	/*
	 * Catchall entry: must be at end.
	 */
	{ 0,		0,		MF_MSG_UNKNOWN,	me_unknown },
};

#undef dirty
#undef sc
#undef unevict
#undef mlock
#undef writeback
#undef lru
#undef head
#undef slab
#undef reserved

/*
 * "Dirty/Clean" indication is not 100% accurate due to the possibility of
 * setting PG_dirty outside page lock. See also comment above set_page_dirty().
 */
static void action_result(unsigned long pfn, enum mf_action_page_type type,
			  enum mf_result result)
{
	trace_memory_failure_event(pfn, type, result);

	pr_err("Memory failure: %#lx: recovery action for %s: %s\n",
		pfn, action_page_types[type], action_name[result]);
}

static int page_action(struct page_state *ps, struct page *p,
			unsigned long pfn)
{
	int result;
	int count;

	result = ps->action(p, pfn);

	count = page_count(p) - 1;
	if (ps->action == me_swapcache_dirty && result == MF_DELAYED)
		count--;
	if (count != 0) {
		pr_err("Memory failure: %#lx: %s still referenced by %d users\n",
		       pfn, action_page_types[ps->type], count);
		result = MF_FAILED;
	}
	action_result(pfn, ps->type, result);

	/* Could do more checks here if page looks ok */
	/*
	 * Could adjust zone counters here to correct for the missing page.
	 */

	return (result == MF_RECOVERED || result == MF_DELAYED) ? 0 : -EBUSY;
}

/**
 * get_hwpoison_page() - Get refcount for memory error handling:
 * @page:	raw error page (hit by memory error)
 *
 * Return: return 0 if failed to grab the refcount, otherwise true (some
 * non-zero value.)
 */
int get_hwpoison_page(struct page *page)
{
	struct page *head = compound_head(page);

	if (!PageHuge(head) && PageTransHuge(head)) {
		/*
		 * Non anonymous thp exists only in allocation/free time. We
		 * can't handle such a case correctly, so let's give it up.
		 * This should be better than triggering BUG_ON when kernel
		 * tries to touch the "partially handled" page.
		 */
		if (!PageAnon(head)) {
			pr_err("Memory failure: %#lx: non anonymous thp\n",
				page_to_pfn(page));
			return 0;
		}
	}

	if (get_page_unless_zero(head)) {
		if (head == compound_head(page))
			return 1;

		pr_info("Memory failure: %#lx cannot catch tail\n",
			page_to_pfn(page));
		put_page(head);
	}

	return 0;
}
EXPORT_SYMBOL_GPL(get_hwpoison_page);

/*
 * Do all that is necessary to remove user space mappings. Unmap
 * the pages and send SIGBUS to the processes if the data was dirty.
 */
static bool hwpoison_user_mappings(struct page *p, unsigned long pfn,
				  int trapno, int flags, struct page **hpagep)
{
	enum ttu_flags ttu = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
	struct address_space *mapping;
	LIST_HEAD(tokill);
	bool unmap_success;
	int kill = 1, forcekill;
	struct page *hpage = *hpagep;
	bool mlocked = PageMlocked(hpage);

	/*
	 * Here we are interested only in user-mapped pages, so skip any
	 * other types of pages.
	 */
	if (PageReserved(p) || PageSlab(p))
		return true;
	if (!(PageLRU(hpage) || PageHuge(p)))
		return true;

	/*
	 * This check implies we don't kill processes if their pages
	 * are in the swap cache early. Those are always late kills.
	 */
	if (!page_mapped(hpage))
		return true;

	if (PageKsm(p)) {
		pr_err("Memory failure: %#lx: can't handle KSM pages.\n", pfn);
		return false;
	}

	if (PageSwapCache(p)) {
		pr_err("Memory failure: %#lx: keeping poisoned page in swap cache\n",
			pfn);
		ttu |= TTU_IGNORE_HWPOISON;
	}

	/*
	 * Propagate the dirty bit from PTEs to struct page first, because we
	 * need this to decide if we should kill or just drop the page.
	 * XXX: the dirty test could be racy: set_page_dirty() may not always
	 * be called inside page lock (it's recommended but not enforced).
	 */
	mapping = page_mapping(hpage);
	if (!(flags & MF_MUST_KILL) && !PageDirty(hpage) && mapping &&
	    mapping_cap_writeback_dirty(mapping)) {
		if (page_mkclean(hpage)) {
			SetPageDirty(hpage);
		} else {
			kill = 0;
			ttu |= TTU_IGNORE_HWPOISON;
			pr_info("Memory failure: %#lx: corrupted page was clean: dropped without side effects\n",
				pfn);
		}
	}

	/*
	 * First collect all the processes that have the page
	 * mapped in dirty form.  This has to be done before try_to_unmap,
	 * because ttu takes the rmap data structures down.
	 *
	 * Error handling: We ignore errors here because
	 * there's nothing that can be done.
	 */
	if (kill)
		collect_procs(hpage, &tokill, flags & MF_ACTION_REQUIRED);

	unmap_success = try_to_unmap(hpage, ttu);
	if (!unmap_success)
		pr_err("Memory failure: %#lx: failed to unmap page (mapcount=%d)\n",
		       pfn, page_mapcount(hpage));

	/*
	 * try_to_unmap() might put mlocked page in lru cache, so call
	 * shake_page() again to ensure that it's flushed.
	 */
	if (mlocked)
		shake_page(hpage, 0);

	/*
	 * Now that the dirty bit has been propagated to the
	 * struct page and all unmaps done we can decide if
	 * killing is needed or not.  Only kill when the page
	 * was dirty or the process is not restartable,
	 * otherwise the tokill list is merely
	 * freed.  When there was a problem unmapping earlier
	 * use a more force-full uncatchable kill to prevent
	 * any accesses to the poisoned memory.
	 */
	forcekill = PageDirty(hpage) || (flags & MF_MUST_KILL);
	kill_procs(&tokill, forcekill, trapno, !unmap_success, p, pfn, flags);

	return unmap_success;
}

/**
 * memory_failure - Handle memory failure of a page.
 * @pfn: Page Number of the corrupted page
 * @trapno: Trap number reported in the signal to user space.
 * @flags: fine tune action taken
 *
 * This function is called by the low level machine check code
 * of an architecture when it detects hardware memory corruption
 * of a page. It tries its best to recover, which includes
 * dropping pages, killing processes etc.
 *
 * The function is primarily of use for corruptions that
 * happen outside the current execution context (e.g. when
 * detected by a background scrubber)
 *
 * Must run in process context (e.g. a work queue) with interrupts
 * enabled and no spinlocks hold.
 */
int memory_failure(unsigned long pfn, int trapno, int flags)
{
	struct page_state *ps;
	struct page *p;
	struct page *hpage;
	struct page *orig_head;
	int res;
	unsigned long page_flags;

	if (!sysctl_memory_failure_recovery)
		panic("Memory failure from trap %d on page %lx", trapno, pfn);

	if (!pfn_valid(pfn)) {
		pr_err("Memory failure: %#lx: memory outside kernel control\n",
			pfn);
		return -ENXIO;
	}

	p = pfn_to_page(pfn);
	orig_head = hpage = compound_head(p);

	/* tmporary check code, to be updated in later patches */
	if (PageHuge(p)) {
		if (TestSetPageHWPoison(hpage)) {
			pr_err("Memory failure: %#lx: already hardware poisoned\n", pfn);
			return 0;
		}
		goto tmp;
	}
	if (TestSetPageHWPoison(p)) {
		pr_err("Memory failure: %#lx: already hardware poisoned\n",
			pfn);
		return 0;
	}

tmp:
	num_poisoned_pages_inc();

	/*
	 * We need/can do nothing about count=0 pages.
	 * 1) it's a free page, and therefore in safe hand:
	 *    prep_new_page() will be the gate keeper.
	 * 2) it's a free hugepage, which is also safe:
	 *    an affected hugepage will be dequeued from hugepage freelist,
	 *    so there's no concern about reusing it ever after.
	 * 3) it's part of a non-compound high order page.
	 *    Implies some kernel user: cannot stop them from
	 *    R/W the page; let's pray that the page has been
	 *    used and will be freed some time later.
	 * In fact it's dangerous to directly bump up page count from 0,
	 * that may make page_freeze_refs()/page_unfreeze_refs() mismatch.
	 */
	if (!(flags & MF_COUNT_INCREASED) && !get_hwpoison_page(p)) {
		if (is_free_buddy_page(p)) {
			action_result(pfn, MF_MSG_BUDDY, MF_DELAYED);
			return 0;
		} else if (PageHuge(hpage)) {
			/*
			 * Check "filter hit" and "race with other subpage."
			 */
			lock_page(hpage);
			if (PageHWPoison(hpage)) {
				if ((hwpoison_filter(p) && TestClearPageHWPoison(p))
				    || (p != hpage && TestSetPageHWPoison(hpage))) {
					num_poisoned_pages_dec();
					unlock_page(hpage);
					return 0;
				}
			}
			res = dequeue_hwpoisoned_huge_page(hpage);
			action_result(pfn, MF_MSG_FREE_HUGE,
				      res ? MF_IGNORED : MF_DELAYED);
			unlock_page(hpage);
			return res;
		} else {
			action_result(pfn, MF_MSG_KERNEL_HIGH_ORDER, MF_IGNORED);
			return -EBUSY;
		}
	}

	if (!PageHuge(p) && PageTransHuge(hpage)) {
		lock_page(p);
		if (!PageAnon(p) || unlikely(split_huge_page(p))) {
			unlock_page(p);
			if (!PageAnon(p))
				pr_err("Memory failure: %#lx: non anonymous thp\n",
					pfn);
			else
				pr_err("Memory failure: %#lx: thp split failed\n",
					pfn);
			if (TestClearPageHWPoison(p))
				num_poisoned_pages_dec();
			put_hwpoison_page(p);
			return -EBUSY;
		}
		unlock_page(p);
		VM_BUG_ON_PAGE(!page_count(p), p);
		hpage = compound_head(p);
	}

	/*
	 * We ignore non-LRU pages for good reasons.
	 * - PG_locked is only well defined for LRU pages and a few others
	 * - to avoid races with __SetPageLocked()
	 * - to avoid races with __SetPageSlab*() (and more non-atomic ops)
	 * The check (unnecessarily) ignores LRU pages being isolated and
	 * walked by the page reclaim code, however that's not a big loss.
	 */
	shake_page(p, 0);
	/* shake_page could have turned it free. */
	if (!PageLRU(p) && is_free_buddy_page(p)) {
		if (flags & MF_COUNT_INCREASED)
			action_result(pfn, MF_MSG_BUDDY, MF_DELAYED);
		else
			action_result(pfn, MF_MSG_BUDDY_2ND, MF_DELAYED);
		return 0;
	}

	lock_page(hpage);

	/*
	 * The page could have changed compound pages during the locking.
	 * If this happens just bail out.
	 */
	if (PageCompound(p) && compound_head(p) != orig_head) {
		action_result(pfn, MF_MSG_DIFFERENT_COMPOUND, MF_IGNORED);
		res = -EBUSY;
		goto out;
	}

	/*
	 * We use page flags to determine what action should be taken, but
	 * the flags can be modified by the error containment action.  One
	 * example is an mlocked page, where PG_mlocked is cleared by
	 * page_remove_rmap() in try_to_unmap_one(). So to determine page status
	 * correctly, we save a copy of the page flags at this time.
	 */
	if (PageHuge(p))
		page_flags = hpage->flags;
	else
		page_flags = p->flags;

	/*
	 * unpoison always clear PG_hwpoison inside page lock
	 */
	if (!PageHWPoison(p)) {
		pr_err("Memory failure: %#lx: just unpoisoned\n", pfn);
		num_poisoned_pages_dec();
		unlock_page(hpage);
		put_hwpoison_page(hpage);
		return 0;
	}
	if (hwpoison_filter(p)) {
		if (TestClearPageHWPoison(p))
			num_poisoned_pages_dec();
		unlock_page(hpage);
		put_hwpoison_page(hpage);
		return 0;
	}

	if (!PageHuge(p) && !PageTransTail(p) && !PageLRU(p))
		goto identify_page_state;

	/*
	 * For error on the tail page, we should set PG_hwpoison
	 * on the head page to show that the hugepage is hwpoisoned
	 */
	if (PageHuge(p) && PageTail(p) && TestSetPageHWPoison(hpage)) {
		action_result(pfn, MF_MSG_POISONED_HUGE, MF_IGNORED);
		unlock_page(hpage);
		put_hwpoison_page(hpage);
		return 0;
	}

	/*
	 * It's very difficult to mess with pages currently under IO
	 * and in many cases impossible, so we just avoid it here.
	 */
	wait_on_page_writeback(p);

	/*
	 * Now take care of user space mappings.
	 * Abort on fail: __delete_from_page_cache() assumes unmapped page.
	 *
	 * When the raw error page is thp tail page, hpage points to the raw
	 * page after thp split.
	 */
	if (!hwpoison_user_mappings(p, pfn, trapno, flags, &hpage)) {
		action_result(pfn, MF_MSG_UNMAP_FAILED, MF_IGNORED);
		res = -EBUSY;
		goto out;
	}

	/*
	 * Torn down by someone else?
	 */
	if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) {
		action_result(pfn, MF_MSG_TRUNCATED_LRU, MF_IGNORED);
		res = -EBUSY;
		goto out;
	}

identify_page_state:
	res = -EBUSY;
	/*
	 * The first check uses the current page flags which may not have any
	 * relevant information. The second check with the saved page flagss is
	 * carried out only if the first check can't determine the page status.
	 */
	for (ps = error_states;; ps++)
		if ((p->flags & ps->mask) == ps->res)
			break;

	page_flags |= (p->flags & (1UL << PG_dirty));

	if (!ps->mask)
		for (ps = error_states;; ps++)
			if ((page_flags & ps->mask) == ps->res)
				break;
	res = page_action(ps, p, pfn);
out:
	unlock_page(hpage);
	return res;
}
EXPORT_SYMBOL_GPL(memory_failure);

#define MEMORY_FAILURE_FIFO_ORDER	4
#define MEMORY_FAILURE_FIFO_SIZE	(1 << MEMORY_FAILURE_FIFO_ORDER)

struct memory_failure_entry {
	unsigned long pfn;
	int trapno;
	int flags;
};

struct memory_failure_cpu {
	DECLARE_KFIFO(fifo, struct memory_failure_entry,
		      MEMORY_FAILURE_FIFO_SIZE);
	spinlock_t lock;
	struct work_struct work;
};

static DEFINE_PER_CPU(struct memory_failure_cpu, memory_failure_cpu);

/**
 * memory_failure_queue - Schedule handling memory failure of a page.
 * @pfn: Page Number of the corrupted page
 * @trapno: Trap number reported in the signal to user space.
 * @flags: Flags for memory failure handling
 *
 * This function is called by the low level hardware error handler
 * when it detects hardware memory corruption of a page. It schedules
 * the recovering of error page, including dropping pages, killing
 * processes etc.
 *
 * The function is primarily of use for corruptions that
 * happen outside the current execution context (e.g. when
 * detected by a background scrubber)
 *
 * Can run in IRQ context.
 */
void memory_failure_queue(unsigned long pfn, int trapno, int flags)
{
	struct memory_failure_cpu *mf_cpu;
	unsigned long proc_flags;
	struct memory_failure_entry entry = {
		.pfn =		pfn,
		.trapno =	trapno,
		.flags =	flags,
	};

	mf_cpu = &get_cpu_var(memory_failure_cpu);
	spin_lock_irqsave(&mf_cpu->lock, proc_flags);
	if (kfifo_put(&mf_cpu->fifo, entry))
		schedule_work_on(smp_processor_id(), &mf_cpu->work);
	else
		pr_err("Memory failure: buffer overflow when queuing memory failure at %#lx\n",
		       pfn);
	spin_unlock_irqrestore(&mf_cpu->lock, proc_flags);
	put_cpu_var(memory_failure_cpu);
}
EXPORT_SYMBOL_GPL(memory_failure_queue);

static void memory_failure_work_func(struct work_struct *work)
{
	struct memory_failure_cpu *mf_cpu;
	struct memory_failure_entry entry = { 0, };
	unsigned long proc_flags;
	int gotten;

	mf_cpu = this_cpu_ptr(&memory_failure_cpu);
	for (;;) {
		spin_lock_irqsave(&mf_cpu->lock, proc_flags);
		gotten = kfifo_get(&mf_cpu->fifo, &entry);
		spin_unlock_irqrestore(&mf_cpu->lock, proc_flags);
		if (!gotten)
			break;
		if (entry.flags & MF_SOFT_OFFLINE)
			soft_offline_page(pfn_to_page(entry.pfn), entry.flags);
		else
			memory_failure(entry.pfn, entry.trapno, entry.flags);
	}
}

static int __init memory_failure_init(void)
{
	struct memory_failure_cpu *mf_cpu;
	int cpu;

	for_each_possible_cpu(cpu) {
		mf_cpu = &per_cpu(memory_failure_cpu, cpu);
		spin_lock_init(&mf_cpu->lock);
		INIT_KFIFO(mf_cpu->fifo);
		INIT_WORK(&mf_cpu->work, memory_failure_work_func);
	}

	return 0;
}
core_initcall(memory_failure_init);

#define unpoison_pr_info(fmt, pfn, rs)			\
({							\
	if (__ratelimit(rs))				\
		pr_info(fmt, pfn);			\
})

/**
 * unpoison_memory - Unpoison a previously poisoned page
 * @pfn: Page number of the to be unpoisoned page
 *
 * Software-unpoison a page that has been poisoned by
 * memory_failure() earlier.
 *
 * This is only done on the software-level, so it only works
 * for linux injected failures, not real hardware failures
 *
 * Returns 0 for success, otherwise -errno.
 */
int unpoison_memory(unsigned long pfn)
{
	struct page *page;
	struct page *p;
	int freeit = 0;
	static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL,
					DEFAULT_RATELIMIT_BURST);

	if (!pfn_valid(pfn))
		return -ENXIO;

	p = pfn_to_page(pfn);
	page = compound_head(p);

	if (!PageHWPoison(p)) {
		unpoison_pr_info("Unpoison: Page was already unpoisoned %#lx\n",
				 pfn, &unpoison_rs);
		return 0;
	}

	if (page_count(page) > 1) {
		unpoison_pr_info("Unpoison: Someone grabs the hwpoison page %#lx\n",
				 pfn, &unpoison_rs);
		return 0;
	}

	if (page_mapped(page)) {
		unpoison_pr_info("Unpoison: Someone maps the hwpoison page %#lx\n",
				 pfn, &unpoison_rs);
		return 0;
	}

	if (page_mapping(page)) {
		unpoison_pr_info("Unpoison: the hwpoison page has non-NULL mapping %#lx\n",
				 pfn, &unpoison_rs);
		return 0;
	}

	/*
	 * unpoison_memory() can encounter thp only when the thp is being
	 * worked by memory_failure() and the page lock is not held yet.
	 * In such case, we yield to memory_failure() and make unpoison fail.
	 */
	if (!PageHuge(page) && PageTransHuge(page)) {
		unpoison_pr_info("Unpoison: Memory failure is now running on %#lx\n",
				 pfn, &unpoison_rs);
		return 0;
	}

	if (!get_hwpoison_page(p)) {
		/*
		 * Since HWPoisoned hugepage should have non-zero refcount,
		 * race between memory failure and unpoison seems to happen.
		 * In such case unpoison fails and memory failure runs
		 * to the end.
		 */
		if (PageHuge(page)) {
			unpoison_pr_info("Unpoison: Memory failure is now running on free hugepage %#lx\n",
					 pfn, &unpoison_rs);
			return 0;
		}
		if (TestClearPageHWPoison(p))
			num_poisoned_pages_dec();
		unpoison_pr_info("Unpoison: Software-unpoisoned free page %#lx\n",
				 pfn, &unpoison_rs);
		return 0;
	}

	lock_page(page);
	/*
	 * This test is racy because PG_hwpoison is set outside of page lock.
	 * That's acceptable because that won't trigger kernel panic. Instead,
	 * the PG_hwpoison page will be caught and isolated on the entrance to
	 * the free buddy page pool.
	 */
	if (TestClearPageHWPoison(page)) {
		unpoison_pr_info("Unpoison: Software-unpoisoned page %#lx\n",
				 pfn, &unpoison_rs);
		num_poisoned_pages_dec();
		freeit = 1;
	}
	unlock_page(page);

	put_hwpoison_page(page);
	if (freeit && !(pfn == my_zero_pfn(0) && page_count(p) == 1))
		put_hwpoison_page(page);

	return 0;
}
EXPORT_SYMBOL(unpoison_memory);

static struct page *new_page(struct page *p, unsigned long private, int **x)
{
	int nid = page_to_nid(p);
	if (PageHuge(p)) {
		struct hstate *hstate = page_hstate(compound_head(p));

		if (hstate_is_gigantic(hstate))
			return alloc_huge_page_node(hstate, NUMA_NO_NODE);

		return alloc_huge_page_node(hstate, nid);
	} else {
		return __alloc_pages_node(nid, GFP_HIGHUSER_MOVABLE, 0);
	}
}

/*
 * Safely get reference count of an arbitrary page.
 * Returns 0 for a free page, -EIO for a zero refcount page
 * that is not free, and 1 for any other page type.
 * For 1 the page is returned with increased page count, otherwise not.
 */
static int __get_any_page(struct page *p, unsigned long pfn, int flags)
{
	int ret;

	if (flags & MF_COUNT_INCREASED)
		return 1;

	/*
	 * When the target page is a free hugepage, just remove it
	 * from free hugepage list.
	 */
	if (!get_hwpoison_page(p)) {
		if (PageHuge(p)) {
			pr_info("%s: %#lx free huge page\n", __func__, pfn);
			ret = 0;
		} else if (is_free_buddy_page(p)) {
			pr_info("%s: %#lx free buddy page\n", __func__, pfn);
			ret = 0;
		} else {
			pr_info("%s: %#lx: unknown zero refcount page type %lx\n",
				__func__, pfn, p->flags);
			ret = -EIO;
		}
	} else {
		/* Not a free page */
		ret = 1;
	}
	return ret;
}

static int get_any_page(struct page *page, unsigned long pfn, int flags)
{
	int ret = __get_any_page(page, pfn, flags);

	if (ret == 1 && !PageHuge(page) &&
	    !PageLRU(page) && !__PageMovable(page)) {
		/*
		 * Try to free it.
		 */
		put_hwpoison_page(page);
		shake_page(page, 1);

		/*
		 * Did it turn free?
		 */
		ret = __get_any_page(page, pfn, 0);
		if (ret == 1 && !PageLRU(page)) {
			/* Drop page reference which is from __get_any_page() */
			put_hwpoison_page(page);
			pr_info("soft_offline: %#lx: unknown non LRU page type %lx (%pGp)\n",
				pfn, page->flags, &page->flags);
			return -EIO;
		}
	}
	return ret;
}

static int soft_offline_huge_page(struct page *page, int flags)
{
	int ret;
	unsigned long pfn = page_to_pfn(page);
	struct page *hpage = compound_head(page);
	LIST_HEAD(pagelist);

	/*
	 * This double-check of PageHWPoison is to avoid the race with
	 * memory_failure(). See also comment in __soft_offline_page().
	 */
	lock_page(hpage);
	if (PageHWPoison(hpage)) {
		unlock_page(hpage);
		put_hwpoison_page(hpage);
		pr_info("soft offline: %#lx hugepage already poisoned\n", pfn);
		return -EBUSY;
	}
	unlock_page(hpage);

	ret = isolate_huge_page(hpage, &pagelist);
	/*
	 * get_any_page() and isolate_huge_page() takes a refcount each,
	 * so need to drop one here.
	 */
	put_hwpoison_page(hpage);
	if (!ret) {
		pr_info("soft offline: %#lx hugepage failed to isolate\n", pfn);
		return -EBUSY;
	}

	ret = migrate_pages(&pagelist, new_page, NULL, MPOL_MF_MOVE_ALL,
				MIGRATE_SYNC, MR_MEMORY_FAILURE);
	if (ret) {
		pr_info("soft offline: %#lx: migration failed %d, type %lx (%pGp)\n",
			pfn, ret, page->flags, &page->flags);
		if (!list_empty(&pagelist))
			putback_movable_pages(&pagelist);
		if (ret > 0)
			ret = -EIO;
	} else {
		if (PageHuge(page))
			dissolve_free_huge_page(page);
	}
	return ret;
}

static int __soft_offline_page(struct page *page, int flags)
{
	int ret;
	unsigned long pfn = page_to_pfn(page);

	/*
	 * Check PageHWPoison again inside page lock because PageHWPoison
	 * is set by memory_failure() outside page lock. Note that
	 * memory_failure() also double-checks PageHWPoison inside page lock,
	 * so there's no race between soft_offline_page() and memory_failure().
	 */
	lock_page(page);
	wait_on_page_writeback(page);
	if (PageHWPoison(page)) {
		unlock_page(page);
		put_hwpoison_page(page);
		pr_info("soft offline: %#lx page already poisoned\n", pfn);
		return -EBUSY;
	}
	/*
	 * Try to invalidate first. This should work for
	 * non dirty unmapped page cache pages.
	 */
	ret = invalidate_inode_page(page);
	unlock_page(page);
	/*
	 * RED-PEN would be better to keep it isolated here, but we
	 * would need to fix isolation locking first.
	 */
	if (ret == 1) {
		put_hwpoison_page(page);
		pr_info("soft_offline: %#lx: invalidated\n", pfn);
		SetPageHWPoison(page);
		num_poisoned_pages_inc();
		return 0;
	}

	/*
	 * Simple invalidation didn't work.
	 * Try to migrate to a new page instead. migrate.c
	 * handles a large number of cases for us.
	 */
	if (PageLRU(page))
		ret = isolate_lru_page(page);
	else
		ret = isolate_movable_page(page, ISOLATE_UNEVICTABLE);
	/*
	 * Drop page reference which is came from get_any_page()
	 * successful isolate_lru_page() already took another one.
	 */
	put_hwpoison_page(page);
	if (!ret) {
		LIST_HEAD(pagelist);
		/*
		 * After isolated lru page, the PageLRU will be cleared,
		 * so use !__PageMovable instead for LRU page's mapping
		 * cannot have PAGE_MAPPING_MOVABLE.
		 */
		if (!__PageMovable(page))
			inc_node_page_state(page, NR_ISOLATED_ANON +
						page_is_file_cache(page));
		list_add(&page->lru, &pagelist);
		ret = migrate_pages(&pagelist, new_page, NULL, MPOL_MF_MOVE_ALL,
					MIGRATE_SYNC, MR_MEMORY_FAILURE);
		if (ret) {
			if (!list_empty(&pagelist))
				putback_movable_pages(&pagelist);

			pr_info("soft offline: %#lx: migration failed %d, type %lx (%pGp)\n",
				pfn, ret, page->flags, &page->flags);
			if (ret > 0)
				ret = -EIO;
		}
	} else {
		pr_info("soft offline: %#lx: isolation failed: %d, page count %d, type %lx (%pGp)\n",
			pfn, ret, page_count(page), page->flags, &page->flags);
	}
	return ret;
}

static int soft_offline_in_use_page(struct page *page, int flags)
{
	int ret;
	struct page *hpage = compound_head(page);

	if (!PageHuge(page) && PageTransHuge(hpage)) {
		lock_page(hpage);
		if (!PageAnon(hpage) || unlikely(split_huge_page(hpage))) {
			unlock_page(hpage);
			if (!PageAnon(hpage))
				pr_info("soft offline: %#lx: non anonymous thp\n", page_to_pfn(page));
			else
				pr_info("soft offline: %#lx: thp split failed\n", page_to_pfn(page));
			put_hwpoison_page(hpage);
			return -EBUSY;
		}
		unlock_page(hpage);
		get_hwpoison_page(page);
		put_hwpoison_page(hpage);
	}

	if (PageHuge(page))
		ret = soft_offline_huge_page(page, flags);
	else
		ret = __soft_offline_page(page, flags);

	return ret;
}

static void soft_offline_free_page(struct page *page)
{
	struct page *head = compound_head(page);

	if (!TestSetPageHWPoison(head)) {
		num_poisoned_pages_inc();
		if (PageHuge(head))
			dissolve_free_huge_page(page);
	}
}

/**
 * soft_offline_page - Soft offline a page.
 * @page: page to offline
 * @flags: flags. Same as memory_failure().
 *
 * Returns 0 on success, otherwise negated errno.
 *
 * Soft offline a page, by migration or invalidation,
 * without killing anything. This is for the case when
 * a page is not corrupted yet (so it's still valid to access),
 * but has had a number of corrected errors and is better taken
 * out.
 *
 * The actual policy on when to do that is maintained by
 * user space.
 *
 * This should never impact any application or cause data loss,
 * however it might take some time.
 *
 * This is not a 100% solution for all memory, but tries to be
 * ``good enough'' for the majority of memory.
 */
int soft_offline_page(struct page *page, int flags)
{
	int ret;
	unsigned long pfn = page_to_pfn(page);

	if (PageHWPoison(page)) {
		pr_info("soft offline: %#lx page already poisoned\n", pfn);
		if (flags & MF_COUNT_INCREASED)
			put_hwpoison_page(page);
		return -EBUSY;
	}

	get_online_mems();
	ret = get_any_page(page, pfn, flags);
	put_online_mems();

	if (ret > 0)
		ret = soft_offline_in_use_page(page, flags);
	else if (ret == 0)
		soft_offline_free_page(page);

	return ret;
}