aboutsummaryrefslogtreecommitdiff
path: root/drivers/mtd/mtdswap.c
blob: fd7885327611d75d68a25e788fa7a44950109513 (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
/*
 * Swap block device support for MTDs
 * Turns an MTD device into a swap device with block wear leveling
 *
 * Copyright © 2007,2011 Nokia Corporation. All rights reserved.
 *
 * Authors: Jarkko Lavinen <jarkko.lavinen@nokia.com>
 *
 * Based on Richard Purdie's earlier implementation in 2007. Background
 * support and lock-less operation written by Adrian Hunter.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/blktrans.h>
#include <linux/rbtree.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/genhd.h>
#include <linux/swap.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
#include <linux/device.h>
#include <linux/math64.h>

#define MTDSWAP_PREFIX "mtdswap"

/*
 * The number of free eraseblocks when GC should stop
 */
#define CLEAN_BLOCK_THRESHOLD	20

/*
 * Number of free eraseblocks below which GC can also collect low frag
 * blocks.
 */
#define LOW_FRAG_GC_TRESHOLD	5

/*
 * Wear level cost amortization. We want to do wear leveling on the background
 * without disturbing gc too much. This is made by defining max GC frequency.
 * Frequency value 6 means 1/6 of the GC passes will pick an erase block based
 * on the biggest wear difference rather than the biggest dirtiness.
 *
 * The lower freq2 should be chosen so that it makes sure the maximum erase
 * difference will decrease even if a malicious application is deliberately
 * trying to make erase differences large.
 */
#define MAX_ERASE_DIFF		4000
#define COLLECT_NONDIRTY_BASE	MAX_ERASE_DIFF
#define COLLECT_NONDIRTY_FREQ1	6
#define COLLECT_NONDIRTY_FREQ2	4

#define PAGE_UNDEF		UINT_MAX
#define BLOCK_UNDEF		UINT_MAX
#define BLOCK_ERROR		(UINT_MAX - 1)
#define BLOCK_MAX		(UINT_MAX - 2)

#define EBLOCK_BAD		(1 << 0)
#define EBLOCK_NOMAGIC		(1 << 1)
#define EBLOCK_BITFLIP		(1 << 2)
#define EBLOCK_FAILED		(1 << 3)
#define EBLOCK_READERR		(1 << 4)
#define EBLOCK_IDX_SHIFT	5

struct swap_eb {
	struct rb_node rb;
	struct rb_root *root;

	unsigned int flags;
	unsigned int active_count;
	unsigned int erase_count;
	unsigned int pad;		/* speeds up pointer decremtnt */
};

#define MTDSWAP_ECNT_MIN(rbroot) (rb_entry(rb_first(rbroot), struct swap_eb, \
				rb)->erase_count)
#define MTDSWAP_ECNT_MAX(rbroot) (rb_entry(rb_last(rbroot), struct swap_eb, \
				rb)->erase_count)

struct mtdswap_tree {
	struct rb_root root;
	unsigned int count;
};

enum {
	MTDSWAP_CLEAN,
	MTDSWAP_USED,
	MTDSWAP_LOWFRAG,
	MTDSWAP_HIFRAG,
	MTDSWAP_DIRTY,
	MTDSWAP_BITFLIP,
	MTDSWAP_FAILING,
	MTDSWAP_TREE_CNT,
};

struct mtdswap_dev {
	struct mtd_blktrans_dev *mbd_dev;
	struct mtd_info *mtd;
	struct device *dev;

	unsigned int *page_data;
	unsigned int *revmap;

	unsigned int eblks;
	unsigned int spare_eblks;
	unsigned int pages_per_eblk;
	unsigned int max_erase_count;
	struct swap_eb *eb_data;

	struct mtdswap_tree trees[MTDSWAP_TREE_CNT];

	unsigned long long sect_read_count;
	unsigned long long sect_write_count;
	unsigned long long mtd_write_count;
	unsigned long long mtd_read_count;
	unsigned long long discard_count;
	unsigned long long discard_page_count;

	unsigned int curr_write_pos;
	struct swap_eb *curr_write;

	char *page_buf;
	char *oob_buf;

	struct dentry *debugfs_root;
};

struct mtdswap_oobdata {
	__le16 magic;
	__le32 count;
} __attribute__((packed));

#define MTDSWAP_MAGIC_CLEAN	0x2095
#define MTDSWAP_MAGIC_DIRTY	(MTDSWAP_MAGIC_CLEAN + 1)
#define MTDSWAP_TYPE_CLEAN	0
#define MTDSWAP_TYPE_DIRTY	1
#define MTDSWAP_OOBSIZE		sizeof(struct mtdswap_oobdata)

#define MTDSWAP_ERASE_RETRIES	3 /* Before marking erase block bad */
#define MTDSWAP_IO_RETRIES	3

enum {
	MTDSWAP_SCANNED_CLEAN,
	MTDSWAP_SCANNED_DIRTY,
	MTDSWAP_SCANNED_BITFLIP,
	MTDSWAP_SCANNED_BAD,
};

/*
 * In the worst case mtdswap_writesect() has allocated the last clean
 * page from the current block and is then pre-empted by the GC
 * thread. The thread can consume a full erase block when moving a
 * block.
 */
#define MIN_SPARE_EBLOCKS	2
#define MIN_ERASE_BLOCKS	(MIN_SPARE_EBLOCKS + 1)

#define TREE_ROOT(d, name) (&d->trees[MTDSWAP_ ## name].root)
#define TREE_EMPTY(d, name) (TREE_ROOT(d, name)->rb_node == NULL)
#define TREE_NONEMPTY(d, name) (!TREE_EMPTY(d, name))
#define TREE_COUNT(d, name) (d->trees[MTDSWAP_ ## name].count)

#define MTDSWAP_MBD_TO_MTDSWAP(dev) ((struct mtdswap_dev *)dev->priv)

static char partitions[128] = "";
module_param_string(partitions, partitions, sizeof(partitions), 0444);
MODULE_PARM_DESC(partitions, "MTD partition numbers to use as swap "
		"partitions=\"1,3,5\"");

static unsigned int spare_eblocks = 10;
module_param(spare_eblocks, uint, 0444);
MODULE_PARM_DESC(spare_eblocks, "Percentage of spare erase blocks for "
		"garbage collection (default 10%)");

static bool header; /* false */
module_param(header, bool, 0444);
MODULE_PARM_DESC(header,
		"Include builtin swap header (default 0, without header)");

static int mtdswap_gc(struct mtdswap_dev *d, unsigned int background);

static loff_t mtdswap_eb_offset(struct mtdswap_dev *d, struct swap_eb *eb)
{
	return (loff_t)(eb - d->eb_data) * d->mtd->erasesize;
}

static void mtdswap_eb_detach(struct mtdswap_dev *d, struct swap_eb *eb)
{
	unsigned int oldidx;
	struct mtdswap_tree *tp;

	if (eb->root) {
		tp = container_of(eb->root, struct mtdswap_tree, root);
		oldidx = tp - &d->trees[0];

		d->trees[oldidx].count--;
		rb_erase(&eb->rb, eb->root);
	}
}

static void __mtdswap_rb_add(struct rb_root *root, struct swap_eb *eb)
{
	struct rb_node **p, *parent = NULL;
	struct swap_eb *cur;

	p = &root->rb_node;
	while (*p) {
		parent = *p;
		cur = rb_entry(parent, struct swap_eb, rb);
		if (eb->erase_count > cur->erase_count)
			p = &(*p)->rb_right;
		else
			p = &(*p)->rb_left;
	}

	rb_link_node(&eb->rb, parent, p);
	rb_insert_color(&eb->rb, root);
}

static void mtdswap_rb_add(struct mtdswap_dev *d, struct swap_eb *eb, int idx)
{
	struct rb_root *root;

	if (eb->root == &d->trees[idx].root)
		return;

	mtdswap_eb_detach(d, eb);
	root = &d->trees[idx].root;
	__mtdswap_rb_add(root, eb);
	eb->root = root;
	d->trees[idx].count++;
}

static struct rb_node *mtdswap_rb_index(struct rb_root *root, unsigned int idx)
{
	struct rb_node *p;
	unsigned int i;

	p = rb_first(root);
	i = 0;
	while (i < idx && p) {
		p = rb_next(p);
		i++;
	}

	return p;
}

static int mtdswap_handle_badblock(struct mtdswap_dev *d, struct swap_eb *eb)
{
	int ret;
	loff_t offset;

	d->spare_eblks--;
	eb->flags |= EBLOCK_BAD;
	mtdswap_eb_detach(d, eb);
	eb->root = NULL;

	/* badblocks not supported */
	if (!d->mtd->block_markbad)
		return 1;

	offset = mtdswap_eb_offset(d, eb);
	dev_warn(d->dev, "Marking bad block at %08llx\n", offset);
	ret = d->mtd->block_markbad(d->mtd, offset);

	if (ret) {
		dev_warn(d->dev, "Mark block bad failed for block at %08llx "
			"error %d\n", offset, ret);
		return ret;
	}

	return 1;

}

static int mtdswap_handle_write_error(struct mtdswap_dev *d, struct swap_eb *eb)
{
	unsigned int marked = eb->flags & EBLOCK_FAILED;
	struct swap_eb *curr_write = d->curr_write;

	eb->flags |= EBLOCK_FAILED;
	if (curr_write == eb) {
		d->curr_write = NULL;

		if (!marked && d->curr_write_pos != 0) {
			mtdswap_rb_add(d, eb, MTDSWAP_FAILING);
			return 0;
		}
	}

	return mtdswap_handle_badblock(d, eb);
}

static int mtdswap_read_oob(struct mtdswap_dev *d, loff_t from,
			struct mtd_oob_ops *ops)
{
	int ret = d->mtd->read_oob(d->mtd, from, ops);

	if (ret == -EUCLEAN)
		return ret;

	if (ret) {
		dev_warn(d->dev, "Read OOB failed %d for block at %08llx\n",
			ret, from);
		return ret;
	}

	if (ops->oobretlen < ops->ooblen) {
		dev_warn(d->dev, "Read OOB return short read (%zd bytes not "
			"%zd) for block at %08llx\n",
			ops->oobretlen, ops->ooblen, from);
		return -EIO;
	}

	return 0;
}

static int mtdswap_read_markers(struct mtdswap_dev *d, struct swap_eb *eb)
{
	struct mtdswap_oobdata *data, *data2;
	int ret;
	loff_t offset;
	struct mtd_oob_ops ops;

	offset = mtdswap_eb_offset(d, eb);

	/* Check first if the block is bad. */
	if (d->mtd->block_isbad && d->mtd->block_isbad(d->mtd, offset))
		return MTDSWAP_SCANNED_BAD;

	ops.ooblen = 2 * d->mtd->ecclayout->oobavail;
	ops.oobbuf = d->oob_buf;
	ops.ooboffs = 0;
	ops.datbuf = NULL;
	ops.mode = MTD_OOB_AUTO;

	ret = mtdswap_read_oob(d, offset, &ops);

	if (ret && ret != -EUCLEAN)
		return ret;

	data = (struct mtdswap_oobdata *)d->oob_buf;
	data2 = (struct mtdswap_oobdata *)
		(d->oob_buf + d->mtd->ecclayout->oobavail);

	if (le16_to_cpu(data->magic) == MTDSWAP_MAGIC_CLEAN) {
		eb->erase_count = le32_to_cpu(data->count);
		if (ret == -EUCLEAN)
			ret = MTDSWAP_SCANNED_BITFLIP;
		else {
			if (le16_to_cpu(data2->magic) == MTDSWAP_MAGIC_DIRTY)
				ret = MTDSWAP_SCANNED_DIRTY;
			else
				ret = MTDSWAP_SCANNED_CLEAN;
		}
	} else {
		eb->flags |= EBLOCK_NOMAGIC;
		ret = MTDSWAP_SCANNED_DIRTY;
	}

	return ret;
}

static int mtdswap_write_marker(struct mtdswap_dev *d, struct swap_eb *eb,
				u16 marker)
{
	struct mtdswap_oobdata n;
	int ret;
	loff_t offset;
	struct mtd_oob_ops ops;

	ops.ooboffs = 0;
	ops.oobbuf = (uint8_t *)&n;
	ops.mode = MTD_OOB_AUTO;
	ops.datbuf = NULL;

	if (marker == MTDSWAP_TYPE_CLEAN) {
		n.magic = cpu_to_le16(MTDSWAP_MAGIC_CLEAN);
		n.count = cpu_to_le32(eb->erase_count);
		ops.ooblen = MTDSWAP_OOBSIZE;
		offset = mtdswap_eb_offset(d, eb);
	} else {
		n.magic = cpu_to_le16(MTDSWAP_MAGIC_DIRTY);
		ops.ooblen = sizeof(n.magic);
		offset = mtdswap_eb_offset(d, eb) + d->mtd->writesize;
	}

	ret = d->mtd->write_oob(d->mtd, offset , &ops);

	if (ret) {
		dev_warn(d->dev, "Write OOB failed for block at %08llx "
			"error %d\n", offset, ret);
		if (ret == -EIO || ret == -EBADMSG)
			mtdswap_handle_write_error(d, eb);
		return ret;
	}

	if (ops.oobretlen != ops.ooblen) {
		dev_warn(d->dev, "Short OOB write for block at %08llx: "
			"%zd not %zd\n",
			offset, ops.oobretlen, ops.ooblen);
		return ret;
	}

	return 0;
}

/*
 * Are there any erase blocks without MAGIC_CLEAN header, presumably
 * because power was cut off after erase but before header write? We
 * need to guestimate the erase count.
 */
static void mtdswap_check_counts(struct mtdswap_dev *d)
{
	struct rb_root hist_root = RB_ROOT;
	struct rb_node *medrb;
	struct swap_eb *eb;
	unsigned int i, cnt, median;

	cnt = 0;
	for (i = 0; i < d->eblks; i++) {
		eb = d->eb_data + i;

		if (eb->flags & (EBLOCK_NOMAGIC | EBLOCK_BAD | EBLOCK_READERR))
			continue;

		__mtdswap_rb_add(&hist_root, eb);
		cnt++;
	}

	if (cnt == 0)
		return;

	medrb = mtdswap_rb_index(&hist_root, cnt / 2);
	median = rb_entry(medrb, struct swap_eb, rb)->erase_count;

	d->max_erase_count = MTDSWAP_ECNT_MAX(&hist_root);

	for (i = 0; i < d->eblks; i++) {
		eb = d->eb_data + i;

		if (eb->flags & (EBLOCK_NOMAGIC | EBLOCK_READERR))
			eb->erase_count = median;

		if (eb->flags & (EBLOCK_NOMAGIC | EBLOCK_BAD | EBLOCK_READERR))
			continue;

		rb_erase(&eb->rb, &hist_root);
	}
}

static void mtdswap_scan_eblks(struct mtdswap_dev *d)
{
	int status;
	unsigned int i, idx;
	struct swap_eb *eb;

	for (i = 0; i < d->eblks; i++) {
		eb = d->eb_data + i;

		status = mtdswap_read_markers(d, eb);
		if (status < 0)
			eb->flags |= EBLOCK_READERR;
		else if (status == MTDSWAP_SCANNED_BAD) {
			eb->flags |= EBLOCK_BAD;
			continue;
		}

		switch (status) {
		case MTDSWAP_SCANNED_CLEAN:
			idx = MTDSWAP_CLEAN;
			break;
		case MTDSWAP_SCANNED_DIRTY:
		case MTDSWAP_SCANNED_BITFLIP:
			idx = MTDSWAP_DIRTY;
			break;
		default:
			idx = MTDSWAP_FAILING;
		}

		eb->flags |= (idx << EBLOCK_IDX_SHIFT);
	}

	mtdswap_check_counts(d);

	for (i = 0; i < d->eblks; i++) {
		eb = d->eb_data + i;

		if (eb->flags & EBLOCK_BAD)
			continue;

		idx = eb->flags >> EBLOCK_IDX_SHIFT;
		mtdswap_rb_add(d, eb, idx);
	}
}

/*
 * Place eblk into a tree corresponding to its number of active blocks
 * it contains.
 */
static void mtdswap_store_eb(struct mtdswap_dev *d, struct swap_eb *eb)
{
	unsigned int weight = eb->active_count;
	unsigned int maxweight = d->pages_per_eblk;

	if (eb == d->curr_write)
		return;

	if (eb->flags & EBLOCK_BITFLIP)
		mtdswap_rb_add(d, eb, MTDSWAP_BITFLIP);
	else if (eb->flags & (EBLOCK_READERR | EBLOCK_FAILED))
		mtdswap_rb_add(d, eb, MTDSWAP_FAILING);
	if (weight == maxweight)
		mtdswap_rb_add(d, eb, MTDSWAP_USED);
	else if (weight == 0)
		mtdswap_rb_add(d, eb, MTDSWAP_DIRTY);
	else if (weight > (maxweight/2))
		mtdswap_rb_add(d, eb, MTDSWAP_LOWFRAG);
	else
		mtdswap_rb_add(d, eb, MTDSWAP_HIFRAG);
}


static void mtdswap_erase_callback(struct erase_info *done)
{
	wait_queue_head_t *wait_q = (wait_queue_head_t *)done->priv;
	wake_up(wait_q);
}

static int mtdswap_erase_block(struct mtdswap_dev *d, struct swap_eb *eb)
{
	struct mtd_info *mtd = d->mtd;
	struct erase_info erase;
	wait_queue_head_t wq;
	unsigned int retries = 0;
	int ret;

	eb->erase_count++;
	if (eb->erase_count > d->max_erase_count)
		d->max_erase_count = eb->erase_count;

retry:
	init_waitqueue_head(&wq);
	memset(&erase, 0, sizeof(struct erase_info));

	erase.mtd	= mtd;
	erase.callback	= mtdswap_erase_callback;
	erase.addr	= mtdswap_eb_offset(d, eb);
	erase.len	= mtd->erasesize;
	erase.priv	= (u_long)&wq;

	ret = mtd->erase(mtd, &erase);
	if (ret) {
		if (retries++ < MTDSWAP_ERASE_RETRIES) {
			dev_warn(d->dev,
				"erase of erase block %#llx on %s failed",
				erase.addr, mtd->name);
			yield();
			goto retry;
		}

		dev_err(d->dev, "Cannot erase erase block %#llx on %s\n",
			erase.addr, mtd->name);

		mtdswap_handle_badblock(d, eb);
		return -EIO;
	}

	ret = wait_event_interruptible(wq, erase.state == MTD_ERASE_DONE ||
					   erase.state == MTD_ERASE_FAILED);
	if (ret) {
		dev_err(d->dev, "Interrupted erase block %#llx erassure on %s",
			erase.addr, mtd->name);
		return -EINTR;
	}

	if (erase.state == MTD_ERASE_FAILED) {
		if (retries++ < MTDSWAP_ERASE_RETRIES) {
			dev_warn(d->dev,
				"erase of erase block %#llx on %s failed",
				erase.addr, mtd->name);
			yield();
			goto retry;
		}

		mtdswap_handle_badblock(d, eb);
		return -EIO;
	}

	return 0;
}

static int mtdswap_map_free_block(struct mtdswap_dev *d, unsigned int page,
				unsigned int *block)
{
	int ret;
	struct swap_eb *old_eb = d->curr_write;
	struct rb_root *clean_root;
	struct swap_eb *eb;

	if (old_eb == NULL || d->curr_write_pos >= d->pages_per_eblk) {
		do {
			if (TREE_EMPTY(d, CLEAN))
				return -ENOSPC;

			clean_root = TREE_ROOT(d, CLEAN);
			eb = rb_entry(rb_first(clean_root), struct swap_eb, rb);
			rb_erase(&eb->rb, clean_root);
			eb->root = NULL;
			TREE_COUNT(d, CLEAN)--;

			ret = mtdswap_write_marker(d, eb, MTDSWAP_TYPE_DIRTY);
		} while (ret == -EIO || ret == -EBADMSG);

		if (ret)
			return ret;

		d->curr_write_pos = 0;
		d->curr_write = eb;
		if (old_eb)
			mtdswap_store_eb(d, old_eb);
	}

	*block = (d->curr_write - d->eb_data) * d->pages_per_eblk +
		d->curr_write_pos;

	d->curr_write->active_count++;
	d->revmap[*block] = page;
	d->curr_write_pos++;

	return 0;
}

static unsigned int mtdswap_free_page_cnt(struct mtdswap_dev *d)
{
	return TREE_COUNT(d, CLEAN) * d->pages_per_eblk +
		d->pages_per_eblk - d->curr_write_pos;
}

static unsigned int mtdswap_enough_free_pages(struct mtdswap_dev *d)
{
	return mtdswap_free_page_cnt(d) > d->pages_per_eblk;
}

static int mtdswap_write_block(struct mtdswap_dev *d, char *buf,
			unsigned int page, unsigned int *bp, int gc_context)
{
	struct mtd_info *mtd = d->mtd;
	struct swap_eb *eb;
	size_t retlen;
	loff_t writepos;
	int ret;

retry:
	if (!gc_context)
		while (!mtdswap_enough_free_pages(d))
			if (mtdswap_gc(d, 0) > 0)
				return -ENOSPC;

	ret = mtdswap_map_free_block(d, page, bp);
	eb = d->eb_data + (*bp / d->pages_per_eblk);

	if (ret == -EIO || ret == -EBADMSG) {
		d->curr_write = NULL;
		eb->active_count--;
		d->revmap[*bp] = PAGE_UNDEF;
		goto retry;
	}

	if (ret < 0)
		return ret;

	writepos = (loff_t)*bp << PAGE_SHIFT;
	ret =  mtd->write(mtd, writepos, PAGE_SIZE, &retlen, buf);
	if (ret == -EIO || ret == -EBADMSG) {
		d->curr_write_pos--;
		eb->active_count--;
		d->revmap[*bp] = PAGE_UNDEF;
		mtdswap_handle_write_error(d, eb);
		goto retry;
	}

	if (ret < 0) {
		dev_err(d->dev, "Write to MTD device failed: %d (%zd written)",
			ret, retlen);
		goto err;
	}

	if (retlen != PAGE_SIZE) {
		dev_err(d->dev, "Short write to MTD device: %zd written",
			retlen);
		ret = -EIO;
		goto err;
	}

	return ret;

err:
	d->curr_write_pos--;
	eb->active_count--;
	d->revmap[*bp] = PAGE_UNDEF;

	return ret;
}

static int mtdswap_move_block(struct mtdswap_dev *d, unsigned int oldblock,
		unsigned int *newblock)
{
	struct mtd_info *mtd = d->mtd;
	struct swap_eb *eb, *oldeb;
	int ret;
	size_t retlen;
	unsigned int page, retries;
	loff_t readpos;

	page = d->revmap[oldblock];
	readpos = (loff_t) oldblock << PAGE_SHIFT;
	retries = 0;

retry:
	ret = mtd->read(mtd, readpos, PAGE_SIZE, &retlen, d->page_buf);

	if (ret < 0 && ret != -EUCLEAN) {
		oldeb = d->eb_data + oldblock / d->pages_per_eblk;
		oldeb->flags |= EBLOCK_READERR;

		dev_err(d->dev, "Read Error: %d (block %u)\n", ret,
			oldblock);
		retries++;
		if (retries < MTDSWAP_IO_RETRIES)
			goto retry;

		goto read_error;
	}

	if (retlen != PAGE_SIZE) {
		dev_err(d->dev, "Short read: %zd (block %u)\n", retlen,
		       oldblock);
		ret = -EIO;
		goto read_error;
	}

	ret = mtdswap_write_block(d, d->page_buf, page, newblock, 1);
	if (ret < 0) {
		d->page_data[page] = BLOCK_ERROR;
		dev_err(d->dev, "Write error: %d\n", ret);
		return ret;
	}

	eb = d->eb_data + *newblock / d->pages_per_eblk;
	d->page_data[page] = *newblock;
	d->revmap[oldblock] = PAGE_UNDEF;
	eb = d->eb_data + oldblock / d->pages_per_eblk;
	eb->active_count--;

	return 0;

read_error:
	d->page_data[page] = BLOCK_ERROR;
	d->revmap[oldblock] = PAGE_UNDEF;
	return ret;
}

static int mtdswap_gc_eblock(struct mtdswap_dev *d, struct swap_eb *eb)
{
	unsigned int i, block, eblk_base, newblock;
	int ret, errcode;

	errcode = 0;
	eblk_base = (eb - d->eb_data) * d->pages_per_eblk;

	for (i = 0; i < d->pages_per_eblk; i++) {
		if (d->spare_eblks < MIN_SPARE_EBLOCKS)
			return -ENOSPC;

		block = eblk_base + i;
		if (d->revmap[block] == PAGE_UNDEF)
			continue;

		ret = mtdswap_move_block(d, block, &newblock);
		if (ret < 0 && !errcode)
			errcode = ret;
	}

	return errcode;
}

static int __mtdswap_choose_gc_tree(struct mtdswap_dev *d)
{
	int idx, stopat;

	if (TREE_COUNT(d, CLEAN) < LOW_FRAG_GC_TRESHOLD)
		stopat = MTDSWAP_LOWFRAG;
	else
		stopat = MTDSWAP_HIFRAG;

	for (idx = MTDSWAP_BITFLIP; idx >= stopat; idx--)
		if (d->trees[idx].root.rb_node != NULL)
			return idx;

	return -1;
}

static int mtdswap_wlfreq(unsigned int maxdiff)
{
	unsigned int h, x, y, dist, base;

	/*
	 * Calculate linear ramp down from f1 to f2 when maxdiff goes from
	 * MAX_ERASE_DIFF to MAX_ERASE_DIFF + COLLECT_NONDIRTY_BASE.  Similar
	 * to triangle with height f1 - f1 and width COLLECT_NONDIRTY_BASE.
	 */

	dist = maxdiff - MAX_ERASE_DIFF;
	if (dist > COLLECT_NONDIRTY_BASE)
		dist = COLLECT_NONDIRTY_BASE;

	/*
	 * Modelling the slop as right angular triangle with base
	 * COLLECT_NONDIRTY_BASE and height freq1 - freq2. The ratio y/x is
	 * equal to the ratio h/base.
	 */
	h = COLLECT_NONDIRTY_FREQ1 - COLLECT_NONDIRTY_FREQ2;
	base = COLLECT_NONDIRTY_BASE;

	x = dist - base;
	y = (x * h + base / 2) / base;

	return COLLECT_NONDIRTY_FREQ2 + y;
}

static int mtdswap_choose_wl_tree(struct mtdswap_dev *d)
{
	static unsigned int pick_cnt;
	unsigned int i, idx = -1, wear, max;
	struct rb_root *root;

	max = 0;
	for (i = 0; i <= MTDSWAP_DIRTY; i++) {
		root = &d->trees[i].root;
		if (root->rb_node == NULL)
			continue;

		wear = d->max_erase_count - MTDSWAP_ECNT_MIN(root);
		if (wear > max) {
			max = wear;
			idx = i;
		}
	}

	if (max > MAX_ERASE_DIFF && pick_cnt >= mtdswap_wlfreq(max) - 1) {
		pick_cnt = 0;
		return idx;
	}

	pick_cnt++;
	return -1;
}

static int mtdswap_choose_gc_tree(struct mtdswap_dev *d,
				unsigned int background)
{
	int idx;

	if (TREE_NONEMPTY(d, FAILING) &&
		(background || (TREE_EMPTY(d, CLEAN) && TREE_EMPTY(d, DIRTY))))
		return MTDSWAP_FAILING;

	idx = mtdswap_choose_wl_tree(d);
	if (idx >= MTDSWAP_CLEAN)
		return idx;

	return __mtdswap_choose_gc_tree(d);
}

static struct swap_eb *mtdswap_pick_gc_eblk(struct mtdswap_dev *d,
					unsigned int background)
{
	struct rb_root *rp = NULL;
	struct swap_eb *eb = NULL;
	int idx;

	if (background && TREE_COUNT(d, CLEAN) > CLEAN_BLOCK_THRESHOLD &&
		TREE_EMPTY(d, DIRTY) && TREE_EMPTY(d, FAILING))
		return NULL;

	idx = mtdswap_choose_gc_tree(d, background);
	if (idx < 0)
		return NULL;

	rp = &d->trees[idx].root;
	eb = rb_entry(rb_first(rp), struct swap_eb, rb);

	rb_erase(&eb->rb, rp);
	eb->root = NULL;
	d->trees[idx].count--;
	return eb;
}

static unsigned int mtdswap_test_patt(unsigned int i)
{
	return i % 2 ? 0x55555555 : 0xAAAAAAAA;
}

static unsigned int mtdswap_eblk_passes(struct mtdswap_dev *d,
					struct swap_eb *eb)
{
	struct mtd_info *mtd = d->mtd;
	unsigned int test, i, j, patt, mtd_pages;
	loff_t base, pos;
	unsigned int *p1 = (unsigned int *)d->page_buf;
	unsigned char *p2 = (unsigned char *)d->oob_buf;
	struct mtd_oob_ops ops;
	int ret;

	ops.mode = MTD_OOB_AUTO;
	ops.len = mtd->writesize;
	ops.ooblen = mtd->ecclayout->oobavail;
	ops.ooboffs = 0;
	ops.datbuf = d->page_buf;
	ops.oobbuf = d->oob_buf;
	base = mtdswap_eb_offset(d, eb);
	mtd_pages = d->pages_per_eblk * PAGE_SIZE / mtd->writesize;

	for (test = 0; test < 2; test++) {
		pos = base;
		for (i = 0; i < mtd_pages; i++) {
			patt = mtdswap_test_patt(test + i);
			memset(d->page_buf, patt, mtd->writesize);
			memset(d->oob_buf, patt, mtd->ecclayout->oobavail);
			ret = mtd->write_oob(mtd, pos, &ops);
			if (ret)
				goto error;

			pos += mtd->writesize;
		}

		pos = base;
		for (i = 0; i < mtd_pages; i++) {
			ret = mtd->read_oob(mtd, pos, &ops);
			if (ret)
				goto error;

			patt = mtdswap_test_patt(test + i);
			for (j = 0; j < mtd->writesize/sizeof(int); j++)
				if (p1[j] != patt)
					goto error;

			for (j = 0; j < mtd->ecclayout->oobavail; j++)
				if (p2[j] != (unsigned char)patt)
					goto error;

			pos += mtd->writesize;
		}

		ret = mtdswap_erase_block(d, eb);
		if (ret)
			goto error;
	}

	eb->flags &= ~EBLOCK_READERR;
	return 1;

error:
	mtdswap_handle_badblock(d, eb);
	return 0;
}

static int mtdswap_gc(struct mtdswap_dev *d, unsigned int background)
{
	struct swap_eb *eb;
	int ret;

	if (d->spare_eblks < MIN_SPARE_EBLOCKS)
		return 1;

	eb = mtdswap_pick_gc_eblk(d, background);
	if (!eb)
		return 1;

	ret = mtdswap_gc_eblock(d, eb);
	if (ret == -ENOSPC)
		return 1;

	if (eb->flags & EBLOCK_FAILED) {
		mtdswap_handle_badblock(d, eb);
		return 0;
	}

	eb->flags &= ~EBLOCK_BITFLIP;
	ret = mtdswap_erase_block(d, eb);
	if ((eb->flags & EBLOCK_READERR) &&
		(ret || !mtdswap_eblk_passes(d, eb)))
		return 0;

	if (ret == 0)
		ret = mtdswap_write_marker(d, eb, MTDSWAP_TYPE_CLEAN);

	if (ret == 0)
		mtdswap_rb_add(d, eb, MTDSWAP_CLEAN);
	else if (ret != -EIO && ret != -EBADMSG)
		mtdswap_rb_add(d, eb, MTDSWAP_DIRTY);

	return 0;
}

static void mtdswap_background(struct mtd_blktrans_dev *dev)
{
	struct mtdswap_dev *d = MTDSWAP_MBD_TO_MTDSWAP(dev);
	int ret;

	while (1) {
		ret = mtdswap_gc(d, 1);
		if (ret || mtd_blktrans_cease_background(dev))
			return;
	}
}

static void mtdswap_cleanup(struct mtdswap_dev *d)
{
	vfree(d->eb_data);
	vfree(d->revmap);
	vfree(d->page_data);
	kfree(d->oob_buf);
	kfree(d->page_buf);
}

static int mtdswap_flush(struct mtd_blktrans_dev *dev)
{
	struct mtdswap_dev *d = MTDSWAP_MBD_TO_MTDSWAP(dev);

	if (d->mtd->sync)
		d->mtd->sync(d->mtd);
	return 0;
}

static unsigned int mtdswap_badblocks(struct mtd_info *mtd, uint64_t size)
{
	loff_t offset;
	unsigned int badcnt;

	badcnt = 0;

	if (mtd->block_isbad)
		for (offset = 0; offset < size; offset += mtd->erasesize)
			if (mtd->block_isbad(mtd, offset))
				badcnt++;

	return badcnt;
}

static int mtdswap_writesect(struct mtd_blktrans_dev *dev,
			unsigned long page, char *buf)
{
	struct mtdswap_dev *d = MTDSWAP_MBD_TO_MTDSWAP(dev);
	unsigned int newblock, mapped;
	struct swap_eb *eb;
	int ret;

	d->sect_write_count++;

	if (d->spare_eblks < MIN_SPARE_EBLOCKS)
		return -ENOSPC;

	if (header) {
		/* Ignore writes to the header page */
		if (unlikely(page == 0))
			return 0;

		page--;
	}

	mapped = d->page_data[page];
	if (mapped <= BLOCK_MAX) {
		eb = d->eb_data + (mapped / d->pages_per_eblk);
		eb->active_count--;
		mtdswap_store_eb(d, eb);
		d->page_data[page] = BLOCK_UNDEF;
		d->revmap[mapped] = PAGE_UNDEF;
	}

	ret = mtdswap_write_block(d, buf, page, &newblock, 0);
	d->mtd_write_count++;

	if (ret < 0)
		return ret;

	eb = d->eb_data + (newblock / d->pages_per_eblk);
	d->page_data[page] = newblock;

	return 0;
}

/* Provide a dummy swap header for the kernel */
static int mtdswap_auto_header(struct mtdswap_dev *d, char *buf)
{
	union swap_header *hd = (union swap_header *)(buf);

	memset(buf, 0, PAGE_SIZE - 10);

	hd->info.version = 1;
	hd->info.last_page = d->mbd_dev->size - 1;
	hd->info.nr_badpages = 0;

	memcpy(buf + PAGE_SIZE - 10, "SWAPSPACE2", 10);

	return 0;
}

static int mtdswap_readsect(struct mtd_blktrans_dev *dev,
			unsigned long page, char *buf)
{
	struct mtdswap_dev *d = MTDSWAP_MBD_TO_MTDSWAP(dev);
	struct mtd_info *mtd = d->mtd;
	unsigned int realblock, retries;
	loff_t readpos;
	struct swap_eb *eb;
	size_t retlen;
	int ret;

	d->sect_read_count++;

	if (header) {
		if (unlikely(page == 0))
			return mtdswap_auto_header(d, buf);

		page--;
	}

	realblock = d->page_data[page];
	if (realblock > BLOCK_MAX) {
		memset(buf, 0x0, PAGE_SIZE);
		if (realblock == BLOCK_UNDEF)
			return 0;
		else
			return -EIO;
	}

	eb = d->eb_data + (realblock / d->pages_per_eblk);
	BUG_ON(d->revmap[realblock] == PAGE_UNDEF);

	readpos = (loff_t)realblock << PAGE_SHIFT;
	retries = 0;

retry:
	ret = mtd->read(mtd, readpos, PAGE_SIZE, &retlen, buf);

	d->mtd_read_count++;
	if (ret == -EUCLEAN) {
		eb->flags |= EBLOCK_BITFLIP;
		mtdswap_rb_add(d, eb, MTDSWAP_BITFLIP);
		ret = 0;
	}

	if (ret < 0) {
		dev_err(d->dev, "Read error %d\n", ret);
		eb->flags |= EBLOCK_READERR;
		mtdswap_rb_add(d, eb, MTDSWAP_FAILING);
		retries++;
		if (retries < MTDSWAP_IO_RETRIES)
			goto retry;

		return ret;
	}

	if (retlen != PAGE_SIZE) {
		dev_err(d->dev, "Short read %zd\n", retlen);
		return -EIO;
	}

	return 0;
}

static int mtdswap_discard(struct mtd_blktrans_dev *dev, unsigned long first,
			unsigned nr_pages)
{
	struct mtdswap_dev *d = MTDSWAP_MBD_TO_MTDSWAP(dev);
	unsigned long page;
	struct swap_eb *eb;
	unsigned int mapped;

	d->discard_count++;

	for (page = first; page < first + nr_pages; page++) {
		mapped = d->page_data[page];
		if (mapped <= BLOCK_MAX) {
			eb = d->eb_data + (mapped / d->pages_per_eblk);
			eb->active_count--;
			mtdswap_store_eb(d, eb);
			d->page_data[page] = BLOCK_UNDEF;
			d->revmap[mapped] = PAGE_UNDEF;
			d->discard_page_count++;
		} else if (mapped == BLOCK_ERROR) {
			d->page_data[page] = BLOCK_UNDEF;
			d->discard_page_count++;
		}
	}

	return 0;
}

static int mtdswap_show(struct seq_file *s, void *data)
{
	struct mtdswap_dev *d = (struct mtdswap_dev *) s->private;
	unsigned long sum;
	unsigned int count[MTDSWAP_TREE_CNT];
	unsigned int min[MTDSWAP_TREE_CNT];
	unsigned int max[MTDSWAP_TREE_CNT];
	unsigned int i, cw = 0, cwp = 0, cwecount = 0, bb_cnt, mapped, pages;
	uint64_t use_size;
	char *name[] = {"clean", "used", "low", "high", "dirty", "bitflip",
			"failing"};

	mutex_lock(&d->mbd_dev->lock);

	for (i = 0; i < MTDSWAP_TREE_CNT; i++) {
		struct rb_root *root = &d->trees[i].root;

		if (root->rb_node) {
			count[i] = d->trees[i].count;
			min[i] = rb_entry(rb_first(root), struct swap_eb,
					rb)->erase_count;
			max[i] = rb_entry(rb_last(root), struct swap_eb,
					rb)->erase_count;
		} else
			count[i] = 0;
	}

	if (d->curr_write) {
		cw = 1;
		cwp = d->curr_write_pos;
		cwecount = d->curr_write->erase_count;
	}

	sum = 0;
	for (i = 0; i < d->eblks; i++)
		sum += d->eb_data[i].erase_count;

	use_size = (uint64_t)d->eblks * d->mtd->erasesize;
	bb_cnt = mtdswap_badblocks(d->mtd, use_size);

	mapped = 0;
	pages = d->mbd_dev->size;
	for (i = 0; i < pages; i++)
		if (d->page_data[i] != BLOCK_UNDEF)
			mapped++;

	mutex_unlock(&d->mbd_dev->lock);

	for (i = 0; i < MTDSWAP_TREE_CNT; i++) {
		if (!count[i])
			continue;

		if (min[i] != max[i])
			seq_printf(s, "%s:\t%5d erase blocks, erased min %d, "
				"max %d times\n",
				name[i], count[i], min[i], max[i]);
		else
			seq_printf(s, "%s:\t%5d erase blocks, all erased %d "
				"times\n", name[i], count[i], min[i]);
	}

	if (bb_cnt)
		seq_printf(s, "bad:\t%5u erase blocks\n", bb_cnt);

	if (cw)
		seq_printf(s, "current erase block: %u pages used, %u free, "
			"erased %u times\n",
			cwp, d->pages_per_eblk - cwp, cwecount);

	seq_printf(s, "total erasures: %lu\n", sum);

	seq_printf(s, "\n");

	seq_printf(s, "mtdswap_readsect count: %llu\n", d->sect_read_count);
	seq_printf(s, "mtdswap_writesect count: %llu\n", d->sect_write_count);
	seq_printf(s, "mtdswap_discard count: %llu\n", d->discard_count);
	seq_printf(s, "mtd read count: %llu\n", d->mtd_read_count);
	seq_printf(s, "mtd write count: %llu\n", d->mtd_write_count);
	seq_printf(s, "discarded pages count: %llu\n", d->discard_page_count);

	seq_printf(s, "\n");
	seq_printf(s, "total pages: %u\n", pages);
	seq_printf(s, "pages mapped: %u\n", mapped);

	return 0;
}

static int mtdswap_open(struct inode *inode, struct file *file)
{
	return single_open(file, mtdswap_show, inode->i_private);
}

static const struct file_operations mtdswap_fops = {
	.open		= mtdswap_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= single_release,
};

static int mtdswap_add_debugfs(struct mtdswap_dev *d)
{
	struct gendisk *gd = d->mbd_dev->disk;
	struct device *dev = disk_to_dev(gd);

	struct dentry *root;
	struct dentry *dent;

	root = debugfs_create_dir(gd->disk_name, NULL);
	if (IS_ERR(root))
		return 0;

	if (!root) {
		dev_err(dev, "failed to initialize debugfs\n");
		return -1;
	}

	d->debugfs_root = root;

	dent = debugfs_create_file("stats", S_IRUSR, root, d,
				&mtdswap_fops);
	if (!dent) {
		dev_err(d->dev, "debugfs_create_file failed\n");
		debugfs_remove_recursive(root);
		d->debugfs_root = NULL;
		return -1;
	}

	return 0;
}

static int mtdswap_init(struct mtdswap_dev *d, unsigned int eblocks,
			unsigned int spare_cnt)
{
	struct mtd_info *mtd = d->mbd_dev->mtd;
	unsigned int i, eblk_bytes, pages, blocks;
	int ret = -ENOMEM;

	d->mtd = mtd;
	d->eblks = eblocks;
	d->spare_eblks = spare_cnt;
	d->pages_per_eblk = mtd->erasesize >> PAGE_SHIFT;

	pages = d->mbd_dev->size;
	blocks = eblocks * d->pages_per_eblk;

	for (i = 0; i < MTDSWAP_TREE_CNT; i++)
		d->trees[i].root = RB_ROOT;

	d->page_data = vmalloc(sizeof(int)*pages);
	if (!d->page_data)
		goto page_data_fail;

	d->revmap = vmalloc(sizeof(int)*blocks);
	if (!d->revmap)
		goto revmap_fail;

	eblk_bytes = sizeof(struct swap_eb)*d->eblks;
	d->eb_data = vmalloc(eblk_bytes);
	if (!d->eb_data)
		goto eb_data_fail;

	memset(d->eb_data, 0, eblk_bytes);
	for (i = 0; i < pages; i++)
		d->page_data[i] = BLOCK_UNDEF;

	for (i = 0; i < blocks; i++)
		d->revmap[i] = PAGE_UNDEF;

	d->page_buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
	if (!d->page_buf)
		goto page_buf_fail;

	d->oob_buf = kmalloc(2 * mtd->ecclayout->oobavail, GFP_KERNEL);
	if (!d->oob_buf)
		goto oob_buf_fail;

	mtdswap_scan_eblks(d);

	return 0;

oob_buf_fail:
	kfree(d->page_buf);
page_buf_fail:
	vfree(d->eb_data);
eb_data_fail:
	vfree(d->revmap);
revmap_fail:
	vfree(d->page_data);
page_data_fail:
	printk(KERN_ERR "%s: init failed (%d)\n", MTDSWAP_PREFIX, ret);
	return ret;
}

static void mtdswap_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
{
	struct mtdswap_dev *d;
	struct mtd_blktrans_dev *mbd_dev;
	char *parts;
	char *this_opt;
	unsigned long part;
	unsigned int eblocks, eavailable, bad_blocks, spare_cnt;
	uint64_t swap_size, use_size, size_limit;
	struct nand_ecclayout *oinfo;
	int ret;

	parts = &partitions[0];
	if (!*parts)
		return;

	while ((this_opt = strsep(&parts, ",")) != NULL) {
		if (strict_strtoul(this_opt, 0, &part) < 0)
			return;

		if (mtd->index == part)
			break;
	}

	if (mtd->index != part)
		return;

	if (mtd->erasesize < PAGE_SIZE || mtd->erasesize % PAGE_SIZE) {
		printk(KERN_ERR "%s: Erase size %u not multiple of PAGE_SIZE "
			"%lu\n", MTDSWAP_PREFIX, mtd->erasesize, PAGE_SIZE);
		return;
	}

	if (PAGE_SIZE % mtd->writesize || mtd->writesize > PAGE_SIZE) {
		printk(KERN_ERR "%s: PAGE_SIZE %lu not multiple of write size"
			" %u\n", MTDSWAP_PREFIX, PAGE_SIZE, mtd->writesize);
		return;
	}

	oinfo = mtd->ecclayout;
	if (!oinfo) {
		printk(KERN_ERR "%s: mtd%d does not have OOB\n",
			MTDSWAP_PREFIX, mtd->index);
		return;
	}

	if (!mtd->oobsize || oinfo->oobavail < MTDSWAP_OOBSIZE) {
		printk(KERN_ERR "%s: Not enough free bytes in OOB, "
			"%d available, %zu needed.\n",
			MTDSWAP_PREFIX, oinfo->oobavail, MTDSWAP_OOBSIZE);
		return;
	}

	if (spare_eblocks > 100)
		spare_eblocks = 100;

	use_size = mtd->size;
	size_limit = (uint64_t) BLOCK_MAX * PAGE_SIZE;

	if (mtd->size > size_limit) {
		printk(KERN_WARNING "%s: Device too large. Limiting size to "
			"%llu bytes\n", MTDSWAP_PREFIX, size_limit);
		use_size = size_limit;
	}

	eblocks = mtd_div_by_eb(use_size, mtd);
	use_size = eblocks * mtd->erasesize;
	bad_blocks = mtdswap_badblocks(mtd, use_size);
	eavailable = eblocks - bad_blocks;

	if (eavailable < MIN_ERASE_BLOCKS) {
		printk(KERN_ERR "%s: Not enough erase blocks. %u available, "
			"%d needed\n", MTDSWAP_PREFIX, eavailable,
			MIN_ERASE_BLOCKS);
		return;
	}

	spare_cnt = div_u64((uint64_t)eavailable * spare_eblocks, 100);

	if (spare_cnt < MIN_SPARE_EBLOCKS)
		spare_cnt = MIN_SPARE_EBLOCKS;

	if (spare_cnt > eavailable - 1)
		spare_cnt = eavailable - 1;

	swap_size = (uint64_t)(eavailable - spare_cnt) * mtd->erasesize +
		(header ? PAGE_SIZE : 0);

	printk(KERN_INFO "%s: Enabling MTD swap on device %lu, size %llu KB, "
		"%u spare, %u bad blocks\n",
		MTDSWAP_PREFIX, part, swap_size / 1024, spare_cnt, bad_blocks);

	d = kzalloc(sizeof(struct mtdswap_dev), GFP_KERNEL);
	if (!d)
		return;

	mbd_dev = kzalloc(sizeof(struct mtd_blktrans_dev), GFP_KERNEL);
	if (!mbd_dev) {
		kfree(d);
		return;
	}

	d->mbd_dev = mbd_dev;
	mbd_dev->priv = d;

	mbd_dev->mtd = mtd;
	mbd_dev->devnum = mtd->index;
	mbd_dev->size = swap_size >> PAGE_SHIFT;
	mbd_dev->tr = tr;

	if (!(mtd->flags & MTD_WRITEABLE))
		mbd_dev->readonly = 1;

	if (mtdswap_init(d, eblocks, spare_cnt) < 0)
		goto init_failed;

	if (add_mtd_blktrans_dev(mbd_dev) < 0)
		goto cleanup;

	d->dev = disk_to_dev(mbd_dev->disk);

	ret = mtdswap_add_debugfs(d);
	if (ret < 0)
		goto debugfs_failed;

	return;

debugfs_failed:
	del_mtd_blktrans_dev(mbd_dev);

cleanup:
	mtdswap_cleanup(d);

init_failed:
	kfree(mbd_dev);
	kfree(d);
}

static void mtdswap_remove_dev(struct mtd_blktrans_dev *dev)
{
	struct mtdswap_dev *d = MTDSWAP_MBD_TO_MTDSWAP(dev);

	debugfs_remove_recursive(d->debugfs_root);
	del_mtd_blktrans_dev(dev);
	mtdswap_cleanup(d);
	kfree(d);
}

static struct mtd_blktrans_ops mtdswap_ops = {
	.name		= "mtdswap",
	.major		= 0,
	.part_bits	= 0,
	.blksize	= PAGE_SIZE,
	.flush		= mtdswap_flush,
	.readsect	= mtdswap_readsect,
	.writesect	= mtdswap_writesect,
	.discard	= mtdswap_discard,
	.background	= mtdswap_background,
	.add_mtd	= mtdswap_add_mtd,
	.remove_dev	= mtdswap_remove_dev,
	.owner		= THIS_MODULE,
};

static int __init mtdswap_modinit(void)
{
	return register_mtd_blktrans(&mtdswap_ops);
}

static void __exit mtdswap_modexit(void)
{
	deregister_mtd_blktrans(&mtdswap_ops);
}

module_init(mtdswap_modinit);
module_exit(mtdswap_modexit);


MODULE_LICENSE("GPL");
MODULE_AUTHOR("Jarkko Lavinen <jarkko.lavinen@nokia.com>");
MODULE_DESCRIPTION("Block device access to an MTD suitable for using as "
		"swap space");