summaryrefslogtreecommitdiffstats
path: root/drivers/mtd/ubi/scan.c
blob: 3c631863bf40b5b3b5db70e28f4e6b3937e4be49 (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
/*
 * Copyright (c) International Business Machines Corp., 2006
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
 * the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 * Author: Artem Bityutskiy (Битюцкий Артём)
 */

/*
 * UBI scanning sub-system.
 *
 * This sub-system is responsible for scanning the flash media, checking UBI
 * headers and providing complete information about the UBI flash image.
 *
 * The scanning information is represented by a &struct ubi_scan_info' object.
 * Information about found volumes is represented by &struct ubi_scan_volume
 * objects which are kept in volume RB-tree with root at the @volumes field.
 * The RB-tree is indexed by the volume ID.
 *
 * Scanned logical eraseblocks are represented by &struct ubi_scan_leb objects.
 * These objects are kept in per-volume RB-trees with the root at the
 * corresponding &struct ubi_scan_volume object. To put it differently, we keep
 * an RB-tree of per-volume objects and each of these objects is the root of
 * RB-tree of per-eraseblock objects.
 *
 * Corrupted physical eraseblocks are put to the @corr list, free physical
 * eraseblocks are put to the @free list and the physical eraseblock to be
 * erased are put to the @erase list.
 *
 * UBI tries to distinguish between 2 types of corruptions.
 * 1. Corruptions caused by power cuts. These are harmless and expected
 *    corruptions and UBI tries to handle them gracefully, without printing too
 *    many warnings and error messages. The idea is that we do not lose
 *    important data in these case - we may lose only the data which was being
 *    written to the media just before the power cut happened, and the upper
 *    layers (e.g., UBIFS) are supposed to handle these situations. UBI puts
 *    these PEBs to the head of the @erase list and they are scheduled for
 *    erasure.
 *
 * 2. Unexpected corruptions which are not caused by power cuts. During
 *    scanning, such PEBs are put to the @corr list and UBI preserves them.
 *    Obviously, this lessens the amount of available PEBs, and if at some
 *    point UBI runs out of free PEBs, it switches to R/O mode. UBI also loudly
 *    informs about such PEBs every time the MTD device is attached.
 *
 * However, it is difficult to reliably distinguish between these types of
 * corruptions and UBI's strategy is as follows. UBI assumes (2.) if the VID
 * header is corrupted and the data area does not contain all 0xFFs, and there
 * were not bit-flips or integrity errors while reading the data area. Otherwise
 * UBI assumes (1.). The assumptions are:
 *   o if the data area contains only 0xFFs, there is no data, and it is safe
 *     to just erase this PEB.
 *   o if the data area has bit-flips and data integrity errors (ECC errors on
 *     NAND), it is probably a PEB which was being erased when power cut
 *     happened.
 */

#include <linux/err.h>
#include <linux/slab.h>
#include <linux/crc32.h>
#include <linux/math64.h>
#include <linux/random.h>
#include "ubi.h"

#ifdef CONFIG_MTD_UBI_DEBUG_PARANOID
static int paranoid_check_si(struct ubi_device *ubi, struct ubi_scan_info *si);
#else
#define paranoid_check_si(ubi, si) 0
#endif

/* Temporary variables used during scanning */
static struct ubi_ec_hdr *ech;
static struct ubi_vid_hdr *vidh;

/**
 * add_to_list - add physical eraseblock to a list.
 * @si: scanning information
 * @pnum: physical eraseblock number to add
 * @ec: erase counter of the physical eraseblock
 * @to_head: if not zero, add to the head of the list
 * @list: the list to add to
 *
 * This function adds physical eraseblock @pnum to free, erase, or alien lists.
 * If @to_head is not zero, PEB will be added to the head of the list, which
 * basically means it will be processed first later. E.g., we add corrupted
 * PEBs (corrupted due to power cuts) to the head of the erase list to make
 * sure we erase them first and get rid of corruptions ASAP. This function
 * returns zero in case of success and a negative error code in case of
 * failure.
 */
static int add_to_list(struct ubi_scan_info *si, int pnum, int ec, int to_head,
		       struct list_head *list)
{
	struct ubi_scan_leb *seb;

	if (list == &si->free) {
		dbg_bld("add to free: PEB %d, EC %d", pnum, ec);
	} else if (list == &si->erase) {
		dbg_bld("add to erase: PEB %d, EC %d", pnum, ec);
	} else if (list == &si->alien) {
		dbg_bld("add to alien: PEB %d, EC %d", pnum, ec);
		si->alien_peb_count += 1;
	} else
		BUG();

	seb = kmalloc(sizeof(struct ubi_scan_leb), GFP_KERNEL);
	if (!seb)
		return -ENOMEM;

	seb->pnum = pnum;
	seb->ec = ec;
	if (to_head)
		list_add(&seb->u.list, list);
	else
		list_add_tail(&seb->u.list, list);
	return 0;
}

/**
 * add_corrupted - add a corrupted physical eraseblock.
 * @si: scanning information
 * @pnum: physical eraseblock number to add
 * @ec: erase counter of the physical eraseblock
 *
 * This function adds corrupted physical eraseblock @pnum to the 'corr' list.
 * The corruption was presumably not caused by a power cut. Returns zero in
 * case of success and a negative error code in case of failure.
 */
static int add_corrupted(struct ubi_scan_info *si, int pnum, int ec)
{
	struct ubi_scan_leb *seb;

	dbg_bld("add to corrupted: PEB %d, EC %d", pnum, ec);

	seb = kmalloc(sizeof(struct ubi_scan_leb), GFP_KERNEL);
	if (!seb)
		return -ENOMEM;

	si->corr_peb_count += 1;
	seb->pnum = pnum;
	seb->ec = ec;
	list_add(&seb->u.list, &si->corr);
	return 0;
}

/**
 * validate_vid_hdr - check volume identifier header.
 * @vid_hdr: the volume identifier header to check
 * @sv: information about the volume this logical eraseblock belongs to
 * @pnum: physical eraseblock number the VID header came from
 *
 * This function checks that data stored in @vid_hdr is consistent. Returns
 * non-zero if an inconsistency was found and zero if not.
 *
 * Note, UBI does sanity check of everything it reads from the flash media.
 * Most of the checks are done in the I/O sub-system. Here we check that the
 * information in the VID header is consistent to the information in other VID
 * headers of the same volume.
 */
static int validate_vid_hdr(const struct ubi_vid_hdr *vid_hdr,
			    const struct ubi_scan_volume *sv, int pnum)
{
	int vol_type = vid_hdr->vol_type;
	int vol_id = be32_to_cpu(vid_hdr->vol_id);
	int used_ebs = be32_to_cpu(vid_hdr->used_ebs);
	int data_pad = be32_to_cpu(vid_hdr->data_pad);

	if (sv->leb_count != 0) {
		int sv_vol_type;

		/*
		 * This is not the first logical eraseblock belonging to this
		 * volume. Ensure that the data in its VID header is consistent
		 * to the data in previous logical eraseblock headers.
		 */

		if (vol_id != sv->vol_id) {
			dbg_err("inconsistent vol_id");
			goto bad;
		}

		if (sv->vol_type == UBI_STATIC_VOLUME)
			sv_vol_type = UBI_VID_STATIC;
		else
			sv_vol_type = UBI_VID_DYNAMIC;

		if (vol_type != sv_vol_type) {
			dbg_err("inconsistent vol_type");
			goto bad;
		}

		if (used_ebs != sv->used_ebs) {
			dbg_err("inconsistent used_ebs");
			goto bad;
		}

		if (data_pad != sv->data_pad) {
			dbg_err("inconsistent data_pad");
			goto bad;
		}
	}

	return 0;

bad:
	ubi_err("inconsistent VID header at PEB %d", pnum);
	ubi_dbg_dump_vid_hdr(vid_hdr);
	ubi_dbg_dump_sv(sv);
	return -EINVAL;
}

/**
 * add_volume - add volume to the scanning information.
 * @si: scanning information
 * @vol_id: ID of the volume to add
 * @pnum: physical eraseblock number
 * @vid_hdr: volume identifier header
 *
 * If the volume corresponding to the @vid_hdr logical eraseblock is already
 * present in the scanning information, this function does nothing. Otherwise
 * it adds corresponding volume to the scanning information. Returns a pointer
 * to the scanning volume object in case of success and a negative error code
 * in case of failure.
 */
static struct ubi_scan_volume *add_volume(struct ubi_scan_info *si, int vol_id,
					  int pnum,
					  const struct ubi_vid_hdr *vid_hdr)
{
	struct ubi_scan_volume *sv;
	struct rb_node **p = &si->volumes.rb_node, *parent = NULL;

	ubi_assert(vol_id == be32_to_cpu(vid_hdr->vol_id));

	/* Walk the volume RB-tree to look if this volume is already present */
	while (*p) {
		parent = *p;
		sv = rb_entry(parent, struct ubi_scan_volume, rb);

		if (vol_id == sv->vol_id)
			return sv;

		if (vol_id > sv->vol_id)
			p = &(*p)->rb_left;
		else
			p = &(*p)->rb_right;
	}

	/* The volume is absent - add it */
	sv = kmalloc(sizeof(struct ubi_scan_volume), GFP_KERNEL);
	if (!sv)
		return ERR_PTR(-ENOMEM);

	sv->highest_lnum = sv->leb_count = 0;
	sv->vol_id = vol_id;
	sv->root = RB_ROOT;
	sv->used_ebs = be32_to_cpu(vid_hdr->used_ebs);
	sv->data_pad = be32_to_cpu(vid_hdr->data_pad);
	sv->compat = vid_hdr->compat;
	sv->vol_type = vid_hdr->vol_type == UBI_VID_DYNAMIC ? UBI_DYNAMIC_VOLUME
							    : UBI_STATIC_VOLUME;
	if (vol_id > si->highest_vol_id)
		si->highest_vol_id = vol_id;

	rb_link_node(&sv->rb, parent, p);
	rb_insert_color(&sv->rb, &si->volumes);
	si->vols_found += 1;
	dbg_bld("added volume %d", vol_id);
	return sv;
}

/**
 * compare_lebs - find out which logical eraseblock is newer.
 * @ubi: UBI device description object
 * @seb: first logical eraseblock to compare
 * @pnum: physical eraseblock number of the second logical eraseblock to
 * compare
 * @vid_hdr: volume identifier header of the second logical eraseblock
 *
 * This function compares 2 copies of a LEB and informs which one is newer. In
 * case of success this function returns a positive value, in case of failure, a
 * negative error code is returned. The success return codes use the following
 * bits:
 *     o bit 0 is cleared: the first PEB (described by @seb) is newer than the
 *       second PEB (described by @pnum and @vid_hdr);
 *     o bit 0 is set: the second PEB is newer;
 *     o bit 1 is cleared: no bit-flips were detected in the newer LEB;
 *     o bit 1 is set: bit-flips were detected in the newer LEB;
 *     o bit 2 is cleared: the older LEB is not corrupted;
 *     o bit 2 is set: the older LEB is corrupted.
 */
static int compare_lebs(struct ubi_device *ubi, const struct ubi_scan_leb *seb,
			int pnum, const struct ubi_vid_hdr *vid_hdr)
{
	void *buf;
	int len, err, second_is_newer, bitflips = 0, corrupted = 0;
	uint32_t data_crc, crc;
	struct ubi_vid_hdr *vh = NULL;
	unsigned long long sqnum2 = be64_to_cpu(vid_hdr->sqnum);

	if (sqnum2 == seb->sqnum) {
		/*
		 * This must be a really ancient UBI image which has been
		 * created before sequence numbers support has been added. At
		 * that times we used 32-bit LEB versions stored in logical
		 * eraseblocks. That was before UBI got into mainline. We do not
		 * support these images anymore. Well, those images still work,
		 * but only if no unclean reboots happened.
		 */
		ubi_err("unsupported on-flash UBI format\n");
		return -EINVAL;
	}

	/* Obviously the LEB with lower sequence counter is older */
	second_is_newer = !!(sqnum2 > seb->sqnum);

	/*
	 * Now we know which copy is newer. If the copy flag of the PEB with
	 * newer version is not set, then we just return, otherwise we have to
	 * check data CRC. For the second PEB we already have the VID header,
	 * for the first one - we'll need to re-read it from flash.
	 *
	 * Note: this may be optimized so that we wouldn't read twice.
	 */

	if (second_is_newer) {
		if (!vid_hdr->copy_flag) {
			/* It is not a copy, so it is newer */
			dbg_bld("second PEB %d is newer, copy_flag is unset",
				pnum);
			return 1;
		}
	} else {
		if (!seb->copy_flag) {
			/* It is not a copy, so it is newer */
			dbg_bld("first PEB %d is newer, copy_flag is unset",
				pnum);
			return bitflips << 1;
		}

		vh = ubi_zalloc_vid_hdr(ubi, GFP_KERNEL);
		if (!vh)
			return -ENOMEM;

		pnum = seb->pnum;
		err = ubi_io_read_vid_hdr(ubi, pnum, vh, 0);
		if (err) {
			if (err == UBI_IO_BITFLIPS)
				bitflips = 1;
			else {
				dbg_err("VID of PEB %d header is bad, but it "
					"was OK earlier, err %d", pnum, err);
				if (err > 0)
					err = -EIO;

				goto out_free_vidh;
			}
		}

		vid_hdr = vh;
	}

	/* Read the data of the copy and check the CRC */

	len = be32_to_cpu(vid_hdr->data_size);
	buf = vmalloc(len);
	if (!buf) {
		err = -ENOMEM;
		goto out_free_vidh;
	}

	err = ubi_io_read_data(ubi, buf, pnum, 0, len);
	if (err && err != UBI_IO_BITFLIPS && err != -EBADMSG)
		goto out_free_buf;

	data_crc = be32_to_cpu(vid_hdr->data_crc);
	crc = crc32(UBI_CRC32_INIT, buf, len);
	if (crc != data_crc) {
		dbg_bld("PEB %d CRC error: calculated %#08x, must be %#08x",
			pnum, crc, data_crc);
		corrupted = 1;
		bitflips = 0;
		second_is_newer = !second_is_newer;
	} else {
		dbg_bld("PEB %d CRC is OK", pnum);
		bitflips = !!err;
	}

	vfree(buf);
	ubi_free_vid_hdr(ubi, vh);

	if (second_is_newer)
		dbg_bld("second PEB %d is newer, copy_flag is set", pnum);
	else
		dbg_bld("first PEB %d is newer, copy_flag is set", pnum);

	return second_is_newer | (bitflips << 1) | (corrupted << 2);

out_free_buf:
	vfree(buf);
out_free_vidh:
	ubi_free_vid_hdr(ubi, vh);
	return err;
}

/**
 * ubi_scan_add_used - add physical eraseblock to the scanning information.
 * @ubi: UBI device description object
 * @si: scanning information
 * @pnum: the physical eraseblock number
 * @ec: erase counter
 * @vid_hdr: the volume identifier header
 * @bitflips: if bit-flips were detected when this physical eraseblock was read
 *
 * This function adds information about a used physical eraseblock to the
 * 'used' tree of the corresponding volume. The function is rather complex
 * because it has to handle cases when this is not the first physical
 * eraseblock belonging to the same logical eraseblock, and the newer one has
 * to be picked, while the older one has to be dropped. This function returns
 * zero in case of success and a negative error code in case of failure.
 */
int ubi_scan_add_used(struct ubi_device *ubi, struct ubi_scan_info *si,
		      int pnum, int ec, const struct ubi_vid_hdr *vid_hdr,
		      int bitflips)
{
	int err, vol_id, lnum;
	unsigned long long sqnum;
	struct ubi_scan_volume *sv;
	struct ubi_scan_leb *seb;
	struct rb_node **p, *parent = NULL;

	vol_id = be32_to_cpu(vid_hdr->vol_id);
	lnum = be32_to_cpu(vid_hdr->lnum);
	sqnum = be64_to_cpu(vid_hdr->sqnum);

	dbg_bld("PEB %d, LEB %d:%d, EC %d, sqnum %llu, bitflips %d",
		pnum, vol_id, lnum, ec, sqnum, bitflips);

	sv = add_volume(si, vol_id, pnum, vid_hdr);
	if (IS_ERR(sv))
		return PTR_ERR(sv);

	if (si->max_sqnum < sqnum)
		si->max_sqnum = sqnum;

	/*
	 * Walk the RB-tree of logical eraseblocks of volume @vol_id to look
	 * if this is the first instance of this logical eraseblock or not.
	 */
	p = &sv->root.rb_node;
	while (*p) {
		int cmp_res;

		parent = *p;
		seb = rb_entry(parent, struct ubi_scan_leb, u.rb);
		if (lnum != seb->lnum) {
			if (lnum < seb->lnum)
				p = &(*p)->rb_left;
			else
				p = &(*p)->rb_right;
			continue;
		}

		/*
		 * There is already a physical eraseblock describing the same
		 * logical eraseblock present.
		 */

		dbg_bld("this LEB already exists: PEB %d, sqnum %llu, "
			"EC %d", seb->pnum, seb->sqnum, seb->ec);

		/*
		 * Make sure that the logical eraseblocks have different
		 * sequence numbers. Otherwise the image is bad.
		 *
		 * However, if the sequence number is zero, we assume it must
		 * be an ancient UBI image from the era when UBI did not have
		 * sequence numbers. We still can attach these images, unless
		 * there is a need to distinguish between old and new
		 * eraseblocks, in which case we'll refuse the image in
		 * 'compare_lebs()'. In other words, we attach old clean
		 * images, but refuse attaching old images with duplicated
		 * logical eraseblocks because there was an unclean reboot.
		 */
		if (seb->sqnum == sqnum && sqnum != 0) {
			ubi_err("two LEBs with same sequence number %llu",
				sqnum);
			ubi_dbg_dump_seb(seb, 0);
			ubi_dbg_dump_vid_hdr(vid_hdr);
			return -EINVAL;
		}

		/*
		 * Now we have to drop the older one and preserve the newer
		 * one.
		 */
		cmp_res = compare_lebs(ubi, seb, pnum, vid_hdr);
		if (cmp_res < 0)
			return cmp_res;

		if (cmp_res & 1) {
			/*
			 * This logical eraseblock is newer than the one
			 * found earlier.
			 */
			err = validate_vid_hdr(vid_hdr, sv, pnum);
			if (err)
				return err;

			err = add_to_list(si, seb->pnum, seb->ec, cmp_res & 4,
					  &si->erase);
			if (err)
				return err;

			seb->ec = ec;
			seb->pnum = pnum;
			seb->scrub = ((cmp_res & 2) || bitflips);
			seb->copy_flag = vid_hdr->copy_flag;
			seb->sqnum = sqnum;

			if (sv->highest_lnum == lnum)
				sv->last_data_size =
					be32_to_cpu(vid_hdr->data_size);

			return 0;
		} else {
			/*
			 * This logical eraseblock is older than the one found
			 * previously.
			 */
			return add_to_list(si, pnum, ec, cmp_res & 4,
					   &si->erase);
		}
	}

	/*
	 * We've met this logical eraseblock for the first time, add it to the
	 * scanning information.
	 */

	err = validate_vid_hdr(vid_hdr, sv, pnum);
	if (err)
		return err;

	seb = kmalloc(sizeof(struct ubi_scan_leb), GFP_KERNEL);
	if (!seb)
		return -ENOMEM;

	seb->ec = ec;
	seb->pnum = pnum;
	seb->lnum = lnum;
	seb->scrub = bitflips;
	seb->copy_flag = vid_hdr->copy_flag;
	seb->sqnum = sqnum;

	if (sv->highest_lnum <= lnum) {
		sv->highest_lnum = lnum;
		sv->last_data_size = be32_to_cpu(vid_hdr->data_size);
	}

	sv->leb_count += 1;
	rb_link_node(&seb->u.rb, parent, p);
	rb_insert_color(&seb->u.rb, &sv->root);
	return 0;
}

/**
 * ubi_scan_find_sv - find volume in the scanning information.
 * @si: scanning information
 * @vol_id: the requested volume ID
 *
 * This function returns a pointer to the volume description or %NULL if there
 * are no data about this volume in the scanning information.
 */
struct ubi_scan_volume *ubi_scan_find_sv(const struct ubi_scan_info *si,
					 int vol_id)
{
	struct ubi_scan_volume *sv;
	struct rb_node *p = si->volumes.rb_node;

	while (p) {
		sv = rb_entry(p, struct ubi_scan_volume, rb);

		if (vol_id == sv->vol_id)
			return sv;

		if (vol_id > sv->vol_id)
			p = p->rb_left;
		else
			p = p->rb_right;
	}

	return NULL;
}

/**
 * ubi_scan_find_seb - find LEB in the volume scanning information.
 * @sv: a pointer to the volume scanning information
 * @lnum: the requested logical eraseblock
 *
 * This function returns a pointer to the scanning logical eraseblock or %NULL
 * if there are no data about it in the scanning volume information.
 */
struct ubi_scan_leb *ubi_scan_find_seb(const struct ubi_scan_volume *sv,
				       int lnum)
{
	struct ubi_scan_leb *seb;
	struct rb_node *p = sv->root.rb_node;

	while (p) {
		seb = rb_entry(p, struct ubi_scan_leb, u.rb);

		if (lnum == seb->lnum)
			return seb;

		if (lnum > seb->lnum)
			p = p->rb_left;
		else
			p = p->rb_right;
	}

	return NULL;
}

/**
 * ubi_scan_rm_volume - delete scanning information about a volume.
 * @si: scanning information
 * @sv: the volume scanning information to delete
 */
void ubi_scan_rm_volume(struct ubi_scan_info *si, struct ubi_scan_volume *sv)
{
	struct rb_node *rb;
	struct ubi_scan_leb *seb;

	dbg_bld("remove scanning information about volume %d", sv->vol_id);

	while ((rb = rb_first(&sv->root))) {
		seb = rb_entry(rb, struct ubi_scan_leb, u.rb);
		rb_erase(&seb->u.rb, &sv->root);
		list_add_tail(&seb->u.list, &si->erase);
	}

	rb_erase(&sv->rb, &si->volumes);
	kfree(sv);
	si->vols_found -= 1;
}

/**
 * ubi_scan_erase_peb - erase a physical eraseblock.
 * @ubi: UBI device description object
 * @si: scanning information
 * @pnum: physical eraseblock number to erase;
 * @ec: erase counter value to write (%UBI_SCAN_UNKNOWN_EC if it is unknown)
 *
 * This function erases physical eraseblock 'pnum', and writes the erase
 * counter header to it. This function should only be used on UBI device
 * initialization stages, when the EBA sub-system had not been yet initialized.
 * This function returns zero in case of success and a negative error code in
 * case of failure.
 */
int ubi_scan_erase_peb(struct ubi_device *ubi, const struct ubi_scan_info *si,
		       int pnum, int ec)
{
	int err;
	struct ubi_ec_hdr *ec_hdr;

	if ((long long)ec >= UBI_MAX_ERASECOUNTER) {
		/*
		 * Erase counter overflow. Upgrade UBI and use 64-bit
		 * erase counters internally.
		 */
		ubi_err("erase counter overflow at PEB %d, EC %d", pnum, ec);
		return -EINVAL;
	}

	ec_hdr = kzalloc(ubi->ec_hdr_alsize, GFP_KERNEL);
	if (!ec_hdr)
		return -ENOMEM;

	ec_hdr->ec = cpu_to_be64(ec);

	err = ubi_io_sync_erase(ubi, pnum, 0);
	if (err < 0)
		goto out_free;

	err = ubi_io_write_ec_hdr(ubi, pnum, ec_hdr);

out_free:
	kfree(ec_hdr);
	return err;
}

/**
 * ubi_scan_get_free_peb - get a free physical eraseblock.
 * @ubi: UBI device description object
 * @si: scanning information
 *
 * This function returns a free physical eraseblock. It is supposed to be
 * called on the UBI initialization stages when the wear-leveling sub-system is
 * not initialized yet. This function picks a physical eraseblocks from one of
 * the lists, writes the EC header if it is needed, and removes it from the
 * list.
 *
 * This function returns scanning physical eraseblock information in case of
 * success and an error code in case of failure.
 */
struct ubi_scan_leb *ubi_scan_get_free_peb(struct ubi_device *ubi,
					   struct ubi_scan_info *si)
{
	int err = 0;
	struct ubi_scan_leb *seb, *tmp_seb;

	if (!list_empty(&si->free)) {
		seb = list_entry(si->free.next, struct ubi_scan_leb, u.list);
		list_del(&seb->u.list);
		dbg_bld("return free PEB %d, EC %d", seb->pnum, seb->ec);
		return seb;
	}

	/*
	 * We try to erase the first physical eraseblock from the erase list
	 * and pick it if we succeed, or try to erase the next one if not. And
	 * so forth. We don't want to take care about bad eraseblocks here -
	 * they'll be handled later.
	 */
	list_for_each_entry_safe(seb, tmp_seb, &si->erase, u.list) {
		if (seb->ec == UBI_SCAN_UNKNOWN_EC)
			seb->ec = si->mean_ec;

		err = ubi_scan_erase_peb(ubi, si, seb->pnum, seb->ec+1);
		if (err)
			continue;

		seb->ec += 1;
		list_del(&seb->u.list);
		dbg_bld("return PEB %d, EC %d", seb->pnum, seb->ec);
		return seb;
	}

	ubi_err("no free eraseblocks");
	return ERR_PTR(-ENOSPC);
}

/**
 * check_corruption - check the data area of PEB.
 * @ubi: UBI device description object
 * @vid_hrd: the (corrupted) VID header of this PEB
 * @pnum: the physical eraseblock number to check
 *
 * This is a helper function which is used to distinguish between VID header
 * corruptions caused by power cuts and other reasons. If the PEB contains only
 * 0xFF bytes in the data area, the VID header is most probably corrupted
 * because of a power cut (%0 is returned in this case). Otherwise, it was
 * probably corrupted for some other reasons (%1 is returned in this case). A
 * negative error code is returned if a read error occurred.
 *
 * If the corruption reason was a power cut, UBI can safely erase this PEB.
 * Otherwise, it should preserve it to avoid possibly destroying important
 * information.
 */
static int check_corruption(struct ubi_device *ubi, struct ubi_vid_hdr *vid_hdr,
			    int pnum)
{
	int err;

	mutex_lock(&ubi->buf_mutex);
	memset(ubi->peb_buf1, 0x00, ubi->leb_size);

	err = ubi_io_read(ubi, ubi->peb_buf1, pnum, ubi->leb_start,
			  ubi->leb_size);
	if (err == UBI_IO_BITFLIPS || err == -EBADMSG) {
		/*
		 * Bit-flips or integrity errors while reading the data area.
		 * It is difficult to say for sure what type of corruption is
		 * this, but presumably a power cut happened while this PEB was
		 * erased, so it became unstable and corrupted, and should be
		 * erased.
		 */
		return 0;
	}

	if (err)
		return err;

	if (ubi_check_pattern(ubi->peb_buf1, 0xFF, ubi->leb_size)) {
		mutex_unlock(&ubi->buf_mutex);
		return 0;
	}

	ubi_err("PEB %d contains corrupted VID header, and the data does not "
		"contain all 0xFF, this may be a non-UBI PEB or a severe VID "
		"header corruption which requires manual inspection", pnum);
	ubi_dbg_dump_vid_hdr(vid_hdr);
	dbg_msg("hexdump of PEB %d offset %d, length %d",
		pnum, ubi->leb_start, ubi->leb_size);
	ubi_dbg_print_hex_dump(KERN_DEBUG, "", DUMP_PREFIX_OFFSET, 32, 1,
			       ubi->peb_buf1, ubi->leb_size, 1);
	mutex_unlock(&ubi->buf_mutex);
	return 1;
}

/**
 * process_eb - read, check UBI headers, and add them to scanning information.
 * @ubi: UBI device description object
 * @si: scanning information
 * @pnum: the physical eraseblock number
 *
 * This function returns a zero if the physical eraseblock was successfully
 * handled and a negative error code in case of failure.
 */
static int process_eb(struct ubi_device *ubi, struct ubi_scan_info *si,
		      int pnum)
{
	long long uninitialized_var(ec);
	int err, bitflips = 0, vol_id, ec_err = 0;

	dbg_bld("scan PEB %d", pnum);

	/* Skip bad physical eraseblocks */
	err = ubi_io_is_bad(ubi, pnum);
	if (err < 0)
		return err;
	else if (err) {
		/*
		 * FIXME: this is actually duty of the I/O sub-system to
		 * initialize this, but MTD does not provide enough
		 * information.
		 */
		si->bad_peb_count += 1;
		return 0;
	}

	err = ubi_io_read_ec_hdr(ubi, pnum, ech, 0);
	if (err < 0)
		return err;
	switch (err) {
	case 0:
		break;
	case UBI_IO_BITFLIPS:
		bitflips = 1;
		break;
	case UBI_IO_FF:
		si->empty_peb_count += 1;
		return add_to_list(si, pnum, UBI_SCAN_UNKNOWN_EC, 0,
				   &si->erase);
	case UBI_IO_FF_BITFLIPS:
		si->empty_peb_count += 1;
		return add_to_list(si, pnum, UBI_SCAN_UNKNOWN_EC, 1,
				   &si->erase);
	case UBI_IO_BAD_HDR_EBADMSG:
	case UBI_IO_BAD_HDR:
		/*
		 * We have to also look at the VID header, possibly it is not
		 * corrupted. Set %bitflips flag in order to make this PEB be
		 * moved and EC be re-created.
		 */
		ec_err = err;
		ec = UBI_SCAN_UNKNOWN_EC;
		bitflips = 1;
		break;
	default:
		ubi_err("'ubi_io_read_ec_hdr()' returned unknown code %d", err);
		return -EINVAL;
	}

	if (!ec_err) {
		int image_seq;

		/* Make sure UBI version is OK */
		if (ech->version != UBI_VERSION) {
			ubi_err("this UBI version is %d, image version is %d",
				UBI_VERSION, (int)ech->version);
			return -EINVAL;
		}

		ec = be64_to_cpu(ech->ec);
		if (ec > UBI_MAX_ERASECOUNTER) {
			/*
			 * Erase counter overflow. The EC headers have 64 bits
			 * reserved, but we anyway make use of only 31 bit
			 * values, as this seems to be enough for any existing
			 * flash. Upgrade UBI and use 64-bit erase counters
			 * internally.
			 */
			ubi_err("erase counter overflow, max is %d",
				UBI_MAX_ERASECOUNTER);
			ubi_dbg_dump_ec_hdr(ech);
			return -EINVAL;
		}

		/*
		 * Make sure that all PEBs have the same image sequence number.
		 * This allows us to detect situations when users flash UBI
		 * images incorrectly, so that the flash has the new UBI image
		 * and leftovers from the old one. This feature was added
		 * relatively recently, and the sequence number was always
		 * zero, because old UBI implementations always set it to zero.
		 * For this reasons, we do not panic if some PEBs have zero
		 * sequence number, while other PEBs have non-zero sequence
		 * number.
		 */
		image_seq = be32_to_cpu(ech->image_seq);
		if (!ubi->image_seq && image_seq)
			ubi->image_seq = image_seq;
		if (ubi->image_seq && image_seq &&
		    ubi->image_seq != image_seq) {
			ubi_err("bad image sequence number %d in PEB %d, "
				"expected %d", image_seq, pnum, ubi->image_seq);
			ubi_dbg_dump_ec_hdr(ech);
			return -EINVAL;
		}
	}

	/* OK, we've done with the EC header, let's look at the VID header */

	err = ubi_io_read_vid_hdr(ubi, pnum, vidh, 0);
	if (err < 0)
		return err;
	switch (err) {
	case 0:
		break;
	case UBI_IO_BITFLIPS:
		bitflips = 1;
		break;
	case UBI_IO_BAD_HDR_EBADMSG:
		if (ec_err == UBI_IO_BAD_HDR_EBADMSG)
			/*
			 * Both EC and VID headers are corrupted and were read
			 * with data integrity error, probably this is a bad
			 * PEB, bit it is not marked as bad yet. This may also
			 * be a result of power cut during erasure.
			 */
			si->maybe_bad_peb_count += 1;
	case UBI_IO_BAD_HDR:
		if (ec_err)
			/*
			 * Both headers are corrupted. There is a possibility
			 * that this a valid UBI PEB which has corresponding
			 * LEB, but the headers are corrupted. However, it is
			 * impossible to distinguish it from a PEB which just
			 * contains garbage because of a power cut during erase
			 * operation. So we just schedule this PEB for erasure.
			 */
			err = 0;
		else
			/*
			 * The EC was OK, but the VID header is corrupted. We
			 * have to check what is in the data area.
			 */
			err = check_corruption(ubi, vidh, pnum);

		if (err < 0)
			return err;
		else if (!err)
			/* This corruption is caused by a power cut */
			err = add_to_list(si, pnum, ec, 1, &si->erase);
		else
			/* This is an unexpected corruption */
			err = add_corrupted(si, pnum, ec);
		if (err)
			return err;
		goto adjust_mean_ec;
	case UBI_IO_FF_BITFLIPS:
		err = add_to_list(si, pnum, ec, 1, &si->erase);
		if (err)
			return err;
		goto adjust_mean_ec;
	case UBI_IO_FF:
		if (ec_err)
			err = add_to_list(si, pnum, ec, 1, &si->erase);
		else
			err = add_to_list(si, pnum, ec, 0, &si->free);
		if (err)
			return err;
		goto adjust_mean_ec;
	default:
		ubi_err("'ubi_io_read_vid_hdr()' returned unknown code %d",
			err);
		return -EINVAL;
	}

	vol_id = be32_to_cpu(vidh->vol_id);
	if (vol_id > UBI_MAX_VOLUMES && vol_id != UBI_LAYOUT_VOLUME_ID) {
		int lnum = be32_to_cpu(vidh->lnum);

		/* Unsupported internal volume */
		switch (vidh->compat) {
		case UBI_COMPAT_DELETE:
			ubi_msg("\"delete\" compatible internal volume %d:%d"
				" found, will remove it", vol_id, lnum);
			err = add_to_list(si, pnum, ec, 1, &si->erase);
			if (err)
				return err;
			return 0;

		case UBI_COMPAT_RO:
			ubi_msg("read-only compatible internal volume %d:%d"
				" found, switch to read-only mode",
				vol_id, lnum);
			ubi->ro_mode = 1;
			break;

		case UBI_COMPAT_PRESERVE:
			ubi_msg("\"preserve\" compatible internal volume %d:%d"
				" found", vol_id, lnum);
			err = add_to_list(si, pnum, ec, 0, &si->alien);
			if (err)
				return err;
			return 0;

		case UBI_COMPAT_REJECT:
			ubi_err("incompatible internal volume %d:%d found",
				vol_id, lnum);
			return -EINVAL;
		}
	}

	if (ec_err)
		ubi_warn("valid VID header but corrupted EC header at PEB %d",
			 pnum);
	err = ubi_scan_add_used(ubi, si, pnum, ec, vidh, bitflips);
	if (err)
		return err;

adjust_mean_ec:
	if (!ec_err) {
		si->ec_sum += ec;
		si->ec_count += 1;
		if (ec > si->max_ec)
			si->max_ec = ec;
		if (ec < si->min_ec)
			si->min_ec = ec;
	}

	return 0;
}

/**
 * check_what_we_have - check what PEB were found by scanning.
 * @ubi: UBI device description object
 * @si: scanning information
 *
 * This is a helper function which takes a look what PEBs were found by
 * scanning, and decides whether the flash is empty and should be formatted and
 * whether there are too many corrupted PEBs and we should not attach this
 * MTD device. Returns zero if we should proceed with attaching the MTD device,
 * and %-EINVAL if we should not.
 */
static int check_what_we_have(struct ubi_device *ubi, struct ubi_scan_info *si)
{
	struct ubi_scan_leb *seb;
	int max_corr, peb_count;

	peb_count = ubi->peb_count - si->bad_peb_count - si->alien_peb_count;
	max_corr = peb_count / 20 ?: 8;

	/*
	 * Few corrupted PEBs is not a problem and may be just a result of
	 * unclean reboots. However, many of them may indicate some problems
	 * with the flash HW or driver.
	 */
	if (si->corr_peb_count) {
		ubi_err("%d PEBs are corrupted and preserved",
			si->corr_peb_count);
		printk(KERN_ERR "Corrupted PEBs are:");
		list_for_each_entry(seb, &si->corr, u.list)
			printk(KERN_CONT " %d", seb->pnum);
		printk(KERN_CONT "\n");

		/*
		 * If too many PEBs are corrupted, we refuse attaching,
		 * otherwise, only print a warning.
		 */
		if (si->corr_peb_count >= max_corr) {
			ubi_err("too many corrupted PEBs, refusing this device");
			return -EINVAL;
		}
	}

	if (si->empty_peb_count + si->maybe_bad_peb_count == peb_count) {
		/*
		 * All PEBs are empty, or almost all - a couple PEBs look like
		 * they may be bad PEBs which were not marked as bad yet.
		 *
		 * This piece of code basically tries to distinguish between
		 * the following situations:
		 *
		 * 1. Flash is empty, but there are few bad PEBs, which are not
		 *    marked as bad so far, and which were read with error. We
		 *    want to go ahead and format this flash. While formatting,
		 *    the faulty PEBs will probably be marked as bad.
		 *
		 * 2. Flash contains non-UBI data and we do not want to format
		 *    it and destroy possibly important information.
		 */
		if (si->maybe_bad_peb_count <= 2) {
			si->is_empty = 1;
			ubi_msg("empty MTD device detected");
			get_random_bytes(&ubi->image_seq,
					 sizeof(ubi->image_seq));
		} else {
			ubi_err("MTD device is not UBI-formatted and possibly "
				"contains non-UBI data - refusing it");
			return -EINVAL;
		}

	}

	return 0;
}

/**
 * ubi_scan - scan an MTD device.
 * @ubi: UBI device description object
 *
 * This function does full scanning of an MTD device and returns complete
 * information about it. In case of failure, an error code is returned.
 */
struct ubi_scan_info *ubi_scan(struct ubi_device *ubi)
{
	int err, pnum;
	struct rb_node *rb1, *rb2;
	struct ubi_scan_volume *sv;
	struct ubi_scan_leb *seb;
	struct ubi_scan_info *si;

	si = kzalloc(sizeof(struct ubi_scan_info), GFP_KERNEL);
	if (!si)
		return ERR_PTR(-ENOMEM);

	INIT_LIST_HEAD(&si->corr);
	INIT_LIST_HEAD(&si->free);
	INIT_LIST_HEAD(&si->erase);
	INIT_LIST_HEAD(&si->alien);
	si->volumes = RB_ROOT;

	err = -ENOMEM;
	ech = kzalloc(ubi->ec_hdr_alsize, GFP_KERNEL);
	if (!ech)
		goto out_si;

	vidh = ubi_zalloc_vid_hdr(ubi, GFP_KERNEL);
	if (!vidh)
		goto out_ech;

	for (pnum = 0; pnum < ubi->peb_count; pnum++) {
		cond_resched();

		dbg_gen("process PEB %d", pnum);
		err = process_eb(ubi, si, pnum);
		if (err < 0)
			goto out_vidh;
	}

	dbg_msg("scanning is finished");

	/* Calculate mean erase counter */
	if (si->ec_count)
		si->mean_ec = div_u64(si->ec_sum, si->ec_count);

	err = check_what_we_have(ubi, si);
	if (err)
		goto out_vidh;

	/*
	 * In case of unknown erase counter we use the mean erase counter
	 * value.
	 */
	ubi_rb_for_each_entry(rb1, sv, &si->volumes, rb) {
		ubi_rb_for_each_entry(rb2, seb, &sv->root, u.rb)
			if (seb->ec == UBI_SCAN_UNKNOWN_EC)
				seb->ec = si->mean_ec;
	}

	list_for_each_entry(seb, &si->free, u.list) {
		if (seb->ec == UBI_SCAN_UNKNOWN_EC)
			seb->ec = si->mean_ec;
	}

	list_for_each_entry(seb, &si->corr, u.list)
		if (seb->ec == UBI_SCAN_UNKNOWN_EC)
			seb->ec = si->mean_ec;

	list_for_each_entry(seb, &si->erase, u.list)
		if (seb->ec == UBI_SCAN_UNKNOWN_EC)
			seb->ec = si->mean_ec;

	err = paranoid_check_si(ubi, si);
	if (err)
		goto out_vidh;

	ubi_free_vid_hdr(ubi, vidh);
	kfree(ech);

	return si;

out_vidh:
	ubi_free_vid_hdr(ubi, vidh);
out_ech:
	kfree(ech);
out_si:
	ubi_scan_destroy_si(si);
	return ERR_PTR(err);
}

/**
 * destroy_sv - free the scanning volume information
 * @sv: scanning volume information
 *
 * This function destroys the volume RB-tree (@sv->root) and the scanning
 * volume information.
 */
static void destroy_sv(struct ubi_scan_volume *sv)
{
	struct ubi_scan_leb *seb;
	struct rb_node *this = sv->root.rb_node;

	while (this) {
		if (this->rb_left)
			this = this->rb_left;
		else if (this->rb_right)
			this = this->rb_right;
		else {
			seb = rb_entry(this, struct ubi_scan_leb, u.rb);
			this = rb_parent(this);
			if (this) {
				if (this->rb_left == &seb->u.rb)
					this->rb_left = NULL;
				else
					this->rb_right = NULL;
			}

			kfree(seb);
		}
	}
	kfree(sv);
}

/**
 * ubi_scan_destroy_si - destroy scanning information.
 * @si: scanning information
 */
void ubi_scan_destroy_si(struct ubi_scan_info *si)
{
	struct ubi_scan_leb *seb, *seb_tmp;
	struct ubi_scan_volume *sv;
	struct rb_node *rb;

	list_for_each_entry_safe(seb, seb_tmp, &si->alien, u.list) {
		list_del(&seb->u.list);
		kfree(seb);
	}
	list_for_each_entry_safe(seb, seb_tmp, &si->erase, u.list) {
		list_del(&seb->u.list);
		kfree(seb);
	}
	list_for_each_entry_safe(seb, seb_tmp, &si->corr, u.list) {
		list_del(&seb->u.list);
		kfree(seb);
	}
	list_for_each_entry_safe(seb, seb_tmp, &si->free, u.list) {
		list_del(&seb->u.list);
		kfree(seb);
	}

	/* Destroy the volume RB-tree */
	rb = si->volumes.rb_node;
	while (rb) {
		if (rb->rb_left)
			rb = rb->rb_left;
		else if (rb->rb_right)
			rb = rb->rb_right;
		else {
			sv = rb_entry(rb, struct ubi_scan_volume, rb);

			rb = rb_parent(rb);
			if (rb) {
				if (rb->rb_left == &sv->rb)
					rb->rb_left = NULL;
				else
					rb->rb_right = NULL;
			}

			destroy_sv(sv);
		}
	}

	kfree(si);
}

#ifdef CONFIG_MTD_UBI_DEBUG_PARANOID

/**
 * paranoid_check_si - check the scanning information.
 * @ubi: UBI device description object
 * @si: scanning information
 *
 * This function returns zero if the scanning information is all right, and a
 * negative error code if not or if an error occurred.
 */
static int paranoid_check_si(struct ubi_device *ubi, struct ubi_scan_info *si)
{
	int pnum, err, vols_found = 0;
	struct rb_node *rb1, *rb2;
	struct ubi_scan_volume *sv;
	struct ubi_scan_leb *seb, *last_seb;
	uint8_t *buf;

	/*
	 * At first, check that scanning information is OK.
	 */
	ubi_rb_for_each_entry(rb1, sv, &si->volumes, rb) {
		int leb_count = 0;

		cond_resched();

		vols_found += 1;

		if (si->is_empty) {
			ubi_err("bad is_empty flag");
			goto bad_sv;
		}

		if (sv->vol_id < 0 || sv->highest_lnum < 0 ||
		    sv->leb_count < 0 || sv->vol_type < 0 || sv->used_ebs < 0 ||
		    sv->data_pad < 0 || sv->last_data_size < 0) {
			ubi_err("negative values");
			goto bad_sv;
		}

		if (sv->vol_id >= UBI_MAX_VOLUMES &&
		    sv->vol_id < UBI_INTERNAL_VOL_START) {
			ubi_err("bad vol_id");
			goto bad_sv;
		}

		if (sv->vol_id > si->highest_vol_id) {
			ubi_err("highest_vol_id is %d, but vol_id %d is there",
				si->highest_vol_id, sv->vol_id);
			goto out;
		}

		if (sv->vol_type != UBI_DYNAMIC_VOLUME &&
		    sv->vol_type != UBI_STATIC_VOLUME) {
			ubi_err("bad vol_type");
			goto bad_sv;
		}

		if (sv->data_pad > ubi->leb_size / 2) {
			ubi_err("bad data_pad");
			goto bad_sv;
		}

		last_seb = NULL;
		ubi_rb_for_each_entry(rb2, seb, &sv->root, u.rb) {
			cond_resched();

			last_seb = seb;
			leb_count += 1;

			if (seb->pnum < 0 || seb->ec < 0) {
				ubi_err("negative values");
				goto bad_seb;
			}

			if (seb->ec < si->min_ec) {
				ubi_err("bad si->min_ec (%d), %d found",
					si->min_ec, seb->ec);
				goto bad_seb;
			}

			if (seb->ec > si->max_ec) {
				ubi_err("bad si->max_ec (%d), %d found",
					si->max_ec, seb->ec);
				goto bad_seb;
			}

			if (seb->pnum >= ubi->peb_count) {
				ubi_err("too high PEB number %d, total PEBs %d",
					seb->pnum, ubi->peb_count);
				goto bad_seb;
			}

			if (sv->vol_type == UBI_STATIC_VOLUME) {
				if (seb->lnum >= sv->used_ebs) {
					ubi_err("bad lnum or used_ebs");
					goto bad_seb;
				}
			} else {
				if (sv->used_ebs != 0) {
					ubi_err("non-zero used_ebs");
					goto bad_seb;
				}
			}

			if (seb->lnum > sv->highest_lnum) {
				ubi_err("incorrect highest_lnum or lnum");
				goto bad_seb;
			}
		}

		if (sv->leb_count != leb_count) {
			ubi_err("bad leb_count, %d objects in the tree",
				leb_count);
			goto bad_sv;
		}

		if (!last_seb)
			continue;

		seb = last_seb;

		if (seb->lnum != sv->highest_lnum) {
			ubi_err("bad highest_lnum");
			goto bad_seb;
		}
	}

	if (vols_found != si->vols_found) {
		ubi_err("bad si->vols_found %d, should be %d",
			si->vols_found, vols_found);
		goto out;
	}

	/* Check that scanning information is correct */
	ubi_rb_for_each_entry(rb1, sv, &si->volumes, rb) {
		last_seb = NULL;
		ubi_rb_for_each_entry(rb2, seb, &sv->root, u.rb) {
			int vol_type;

			cond_resched();

			last_seb = seb;

			err = ubi_io_read_vid_hdr(ubi, seb->pnum, vidh, 1);
			if (err && err != UBI_IO_BITFLIPS) {
				ubi_err("VID header is not OK (%d)", err);
				if (err > 0)
					err = -EIO;
				return err;
			}

			vol_type = vidh->vol_type == UBI_VID_DYNAMIC ?
				   UBI_DYNAMIC_VOLUME : UBI_STATIC_VOLUME;
			if (sv->vol_type != vol_type) {
				ubi_err("bad vol_type");
				goto bad_vid_hdr;
			}

			if (seb->sqnum != be64_to_cpu(vidh->sqnum)) {
				ubi_err("bad sqnum %llu", seb->sqnum);
				goto bad_vid_hdr;
			}

			if (sv->vol_id != be32_to_cpu(vidh->vol_id)) {
				ubi_err("bad vol_id %d", sv->vol_id);
				goto bad_vid_hdr;
			}

			if (sv->compat != vidh->compat) {
				ubi_err("bad compat %d", vidh->compat);
				goto bad_vid_hdr;
			}

			if (seb->lnum != be32_to_cpu(vidh->lnum)) {
				ubi_err("bad lnum %d", seb->lnum);
				goto bad_vid_hdr;
			}

			if (sv->used_ebs != be32_to_cpu(vidh->used_ebs)) {
				ubi_err("bad used_ebs %d", sv->used_ebs);
				goto bad_vid_hdr;
			}

			if (sv->data_pad != be32_to_cpu(vidh->data_pad)) {
				ubi_err("bad data_pad %d", sv->data_pad);
				goto bad_vid_hdr;
			}
		}

		if (!last_seb)
			continue;

		if (sv->highest_lnum != be32_to_cpu(vidh->lnum)) {
			ubi_err("bad highest_lnum %d", sv->highest_lnum);
			goto bad_vid_hdr;
		}

		if (sv->last_data_size != be32_to_cpu(vidh->data_size)) {
			ubi_err("bad last_data_size %d", sv->last_data_size);
			goto bad_vid_hdr;
		}
	}

	/*
	 * Make sure that all the physical eraseblocks are in one of the lists
	 * or trees.
	 */
	buf = kzalloc(ubi->peb_count, GFP_KERNEL);
	if (!buf)
		return -ENOMEM;

	for (pnum = 0; pnum < ubi->peb_count; pnum++) {
		err = ubi_io_is_bad(ubi, pnum);
		if (err < 0) {
			kfree(buf);
			return err;
		} else if (err)
			buf[pnum] = 1;
	}

	ubi_rb_for_each_entry(rb1, sv, &si->volumes, rb)
		ubi_rb_for_each_entry(rb2, seb, &sv->root, u.rb)
			buf[seb->pnum] = 1;

	list_for_each_entry(seb, &si->free, u.list)
		buf[seb->pnum] = 1;

	list_for_each_entry(seb, &si->corr, u.list)
		buf[seb->pnum] = 1;

	list_for_each_entry(seb, &si->erase, u.list)
		buf[seb->pnum] = 1;

	list_for_each_entry(seb, &si->alien, u.list)
		buf[seb->pnum] = 1;

	err = 0;
	for (pnum = 0; pnum < ubi->peb_count; pnum++)
		if (!buf[pnum]) {
			ubi_err("PEB %d is not referred", pnum);
			err = 1;
		}

	kfree(buf);
	if (err)
		goto out;
	return 0;

bad_seb:
	ubi_err("bad scanning information about LEB %d", seb->lnum);
	ubi_dbg_dump_seb(seb, 0);
	ubi_dbg_dump_sv(sv);
	goto out;

bad_sv:
	ubi_err("bad scanning information about volume %d", sv->vol_id);
	ubi_dbg_dump_sv(sv);
	goto out;

bad_vid_hdr:
	ubi_err("bad scanning information about volume %d", sv->vol_id);
	ubi_dbg_dump_sv(sv);
	ubi_dbg_dump_vid_hdr(vidh);

out:
	ubi_dbg_dump_stack();
	return -EINVAL;
}

#endif /* CONFIG_MTD_UBI_DEBUG_PARANOID */