Linux Audio

Check our new training course

Embedded Linux Audio

Check our new training course
with Creative Commons CC-BY-SA
lecture materials

Bootlin logo

Elixir Cross Referencer

Loading...
   1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (c) International Business Machines Corp., 2006
 *
 * Authors: Artem Bityutskiy (Битюцкий Артём), Thomas Gleixner
 */

/*
 * UBI wear-leveling sub-system.
 *
 * This sub-system is responsible for wear-leveling. It works in terms of
 * physical eraseblocks and erase counters and knows nothing about logical
 * eraseblocks, volumes, etc. From this sub-system's perspective all physical
 * eraseblocks are of two types - used and free. Used physical eraseblocks are
 * those that were "get" by the 'ubi_wl_get_peb()' function, and free physical
 * eraseblocks are those that were put by the 'ubi_wl_put_peb()' function.
 *
 * Physical eraseblocks returned by 'ubi_wl_get_peb()' have only erase counter
 * header. The rest of the physical eraseblock contains only %0xFF bytes.
 *
 * When physical eraseblocks are returned to the WL sub-system by means of the
 * 'ubi_wl_put_peb()' function, they are scheduled for erasure. The erasure is
 * done asynchronously in context of the per-UBI device background thread,
 * which is also managed by the WL sub-system.
 *
 * The wear-leveling is ensured by means of moving the contents of used
 * physical eraseblocks with low erase counter to free physical eraseblocks
 * with high erase counter.
 *
 * If the WL sub-system fails to erase a physical eraseblock, it marks it as
 * bad.
 *
 * This sub-system is also responsible for scrubbing. If a bit-flip is detected
 * in a physical eraseblock, it has to be moved. Technically this is the same
 * as moving it for wear-leveling reasons.
 *
 * As it was said, for the UBI sub-system all physical eraseblocks are either
 * "free" or "used". Free eraseblock are kept in the @wl->free RB-tree, while
 * used eraseblocks are kept in @wl->used, @wl->erroneous, or @wl->scrub
 * RB-trees, as well as (temporarily) in the @wl->pq queue.
 *
 * When the WL sub-system returns a physical eraseblock, the physical
 * eraseblock is protected from being moved for some "time". For this reason,
 * the physical eraseblock is not directly moved from the @wl->free tree to the
 * @wl->used tree. There is a protection queue in between where this
 * physical eraseblock is temporarily stored (@wl->pq).
 *
 * All this protection stuff is needed because:
 *  o we don't want to move physical eraseblocks just after we have given them
 *    to the user; instead, we first want to let users fill them up with data;
 *
 *  o there is a chance that the user will put the physical eraseblock very
 *    soon, so it makes sense not to move it for some time, but wait.
 *
 * Physical eraseblocks stay protected only for limited time. But the "time" is
 * measured in erase cycles in this case. This is implemented with help of the
 * protection queue. Eraseblocks are put to the tail of this queue when they
 * are returned by the 'ubi_wl_get_peb()', and eraseblocks are removed from the
 * head of the queue on each erase operation (for any eraseblock). So the
 * length of the queue defines how may (global) erase cycles PEBs are protected.
 *
 * To put it differently, each physical eraseblock has 2 main states: free and
 * used. The former state corresponds to the @wl->free tree. The latter state
 * is split up on several sub-states:
 * o the WL movement is allowed (@wl->used tree);
 * o the WL movement is disallowed (@wl->erroneous) because the PEB is
 *   erroneous - e.g., there was a read error;
 * o the WL movement is temporarily prohibited (@wl->pq queue);
 * o scrubbing is needed (@wl->scrub tree).
 *
 * Depending on the sub-state, wear-leveling entries of the used physical
 * eraseblocks may be kept in one of those structures.
 *
 * Note, in this implementation, we keep a small in-RAM object for each physical
 * eraseblock. This is surely not a scalable solution. But it appears to be good
 * enough for moderately large flashes and it is simple. In future, one may
 * re-work this sub-system and make it more scalable.
 *
 * At the moment this sub-system does not utilize the sequence number, which
 * was introduced relatively recently. But it would be wise to do this because
 * the sequence number of a logical eraseblock characterizes how old is it. For
 * example, when we move a PEB with low erase counter, and we need to pick the
 * target PEB, we pick a PEB with the highest EC if our PEB is "old" and we
 * pick target PEB with an average EC if our PEB is not very "old". This is a
 * room for future re-works of the WL sub-system.
 */

#include <linux/slab.h>
#include <linux/crc32.h>
#include <linux/freezer.h>
#include <linux/kthread.h>
#include "ubi.h"
#include "wl.h"

/* Number of physical eraseblocks reserved for wear-leveling purposes */
#define WL_RESERVED_PEBS 1

/*
 * Maximum difference between two erase counters. If this threshold is
 * exceeded, the WL sub-system starts moving data from used physical
 * eraseblocks with low erase counter to free physical eraseblocks with high
 * erase counter.
 */
#define UBI_WL_THRESHOLD CONFIG_MTD_UBI_WL_THRESHOLD

/*
 * When a physical eraseblock is moved, the WL sub-system has to pick the target
 * physical eraseblock to move to. The simplest way would be just to pick the
 * one with the highest erase counter. But in certain workloads this could lead
 * to an unlimited wear of one or few physical eraseblock. Indeed, imagine a
 * situation when the picked physical eraseblock is constantly erased after the
 * data is written to it. So, we have a constant which limits the highest erase
 * counter of the free physical eraseblock to pick. Namely, the WL sub-system
 * does not pick eraseblocks with erase counter greater than the lowest erase
 * counter plus %WL_FREE_MAX_DIFF.
 */
#define WL_FREE_MAX_DIFF (2*UBI_WL_THRESHOLD)

/*
 * Maximum number of consecutive background thread failures which is enough to
 * switch to read-only mode.
 */
#define WL_MAX_FAILURES 32

static int self_check_ec(struct ubi_device *ubi, int pnum, int ec);
static int self_check_in_wl_tree(const struct ubi_device *ubi,
				 struct ubi_wl_entry *e, struct rb_root *root);
static int self_check_in_pq(const struct ubi_device *ubi,
			    struct ubi_wl_entry *e);

/**
 * wl_tree_add - add a wear-leveling entry to a WL RB-tree.
 * @e: the wear-leveling entry to add
 * @root: the root of the tree
 *
 * Note, we use (erase counter, physical eraseblock number) pairs as keys in
 * the @ubi->used and @ubi->free RB-trees.
 */
static void wl_tree_add(struct ubi_wl_entry *e, struct rb_root *root)
{
	struct rb_node **p, *parent = NULL;

	p = &root->rb_node;
	while (*p) {
		struct ubi_wl_entry *e1;

		parent = *p;
		e1 = rb_entry(parent, struct ubi_wl_entry, u.rb);

		if (e->ec < e1->ec)
			p = &(*p)->rb_left;
		else if (e->ec > e1->ec)
			p = &(*p)->rb_right;
		else {
			ubi_assert(e->pnum != e1->pnum);
			if (e->pnum < e1->pnum)
				p = &(*p)->rb_left;
			else
				p = &(*p)->rb_right;
		}
	}

	rb_link_node(&e->u.rb, parent, p);
	rb_insert_color(&e->u.rb, root);
}

/**
 * wl_entry_destroy - destroy a wear-leveling entry.
 * @ubi: UBI device description object
 * @e: the wear-leveling entry to add
 *
 * This function destroys a wear leveling entry and removes
 * the reference from the lookup table.
 */
static void wl_entry_destroy(struct ubi_device *ubi, struct ubi_wl_entry *e)
{
	ubi->lookuptbl[e->pnum] = NULL;
	kmem_cache_free(ubi_wl_entry_slab, e);
}

/**
 * do_work - do one pending work.
 * @ubi: UBI device description object
 * @executed: whether there is one work is executed
 *
 * This function returns zero in case of success and a negative error code in
 * case of failure. If @executed is not NULL and there is one work executed,
 * @executed is set as %1, otherwise @executed is set as %0.
 */
static int do_work(struct ubi_device *ubi, int *executed)
{
	int err;
	struct ubi_work *wrk;

	cond_resched();

	/*
	 * @ubi->work_sem is used to synchronize with the workers. Workers take
	 * it in read mode, so many of them may be doing works at a time. But
	 * the queue flush code has to be sure the whole queue of works is
	 * done, and it takes the mutex in write mode.
	 */
	down_read(&ubi->work_sem);
	spin_lock(&ubi->wl_lock);
	if (list_empty(&ubi->works)) {
		spin_unlock(&ubi->wl_lock);
		up_read(&ubi->work_sem);
		if (executed)
			*executed = 0;
		return 0;
	}

	if (executed)
		*executed = 1;
	wrk = list_entry(ubi->works.next, struct ubi_work, list);
	list_del(&wrk->list);
	ubi->works_count -= 1;
	ubi_assert(ubi->works_count >= 0);
	spin_unlock(&ubi->wl_lock);

	/*
	 * Call the worker function. Do not touch the work structure
	 * after this call as it will have been freed or reused by that
	 * time by the worker function.
	 */
	err = wrk->func(ubi, wrk, 0);
	if (err)
		ubi_err(ubi, "work failed with error code %d", err);
	up_read(&ubi->work_sem);

	return err;
}

/**
 * in_wl_tree - check if wear-leveling entry is present in a WL RB-tree.
 * @e: the wear-leveling entry to check
 * @root: the root of the tree
 *
 * This function returns non-zero if @e is in the @root RB-tree and zero if it
 * is not.
 */
static int in_wl_tree(struct ubi_wl_entry *e, struct rb_root *root)
{
	struct rb_node *p;

	p = root->rb_node;
	while (p) {
		struct ubi_wl_entry *e1;

		e1 = rb_entry(p, struct ubi_wl_entry, u.rb);

		if (e->pnum == e1->pnum) {
			ubi_assert(e == e1);
			return 1;
		}

		if (e->ec < e1->ec)
			p = p->rb_left;
		else if (e->ec > e1->ec)
			p = p->rb_right;
		else {
			ubi_assert(e->pnum != e1->pnum);
			if (e->pnum < e1->pnum)
				p = p->rb_left;
			else
				p = p->rb_right;
		}
	}

	return 0;
}

/**
 * in_pq - check if a wear-leveling entry is present in the protection queue.
 * @ubi: UBI device description object
 * @e: the wear-leveling entry to check
 *
 * This function returns non-zero if @e is in the protection queue and zero
 * if it is not.
 */
static inline int in_pq(const struct ubi_device *ubi, struct ubi_wl_entry *e)
{
	struct ubi_wl_entry *p;
	int i;

	for (i = 0; i < UBI_PROT_QUEUE_LEN; ++i)
		list_for_each_entry(p, &ubi->pq[i], u.list)
			if (p == e)
				return 1;

	return 0;
}

/**
 * prot_queue_add - add physical eraseblock to the protection queue.
 * @ubi: UBI device description object
 * @e: the physical eraseblock to add
 *
 * This function adds @e to the tail of the protection queue @ubi->pq, where
 * @e will stay for %UBI_PROT_QUEUE_LEN erase operations and will be
 * temporarily protected from the wear-leveling worker. Note, @wl->lock has to
 * be locked.
 */
static void prot_queue_add(struct ubi_device *ubi, struct ubi_wl_entry *e)
{
	int pq_tail = ubi->pq_head - 1;

	if (pq_tail < 0)
		pq_tail = UBI_PROT_QUEUE_LEN - 1;
	ubi_assert(pq_tail >= 0 && pq_tail < UBI_PROT_QUEUE_LEN);
	list_add_tail(&e->u.list, &ubi->pq[pq_tail]);
	dbg_wl("added PEB %d EC %d to the protection queue", e->pnum, e->ec);
}

/**
 * find_wl_entry - find wear-leveling entry closest to certain erase counter.
 * @ubi: UBI device description object
 * @root: the RB-tree where to look for
 * @diff: maximum possible difference from the smallest erase counter
 * @pick_max: pick PEB even its erase counter beyonds 'min_ec + @diff'
 *
 * This function looks for a wear leveling entry with erase counter closest to
 * min + @diff, where min is the smallest erase counter.
 */
static struct ubi_wl_entry *find_wl_entry(struct ubi_device *ubi,
					  struct rb_root *root, int diff,
					  int pick_max)
{
	struct rb_node *p;
	struct ubi_wl_entry *e;
	int max;

	e = rb_entry(rb_first(root), struct ubi_wl_entry, u.rb);
	max = e->ec + diff;

	p = root->rb_node;
	while (p) {
		struct ubi_wl_entry *e1;

		e1 = rb_entry(p, struct ubi_wl_entry, u.rb);
		if (e1->ec >= max) {
			if (pick_max)
				e = e1;
			p = p->rb_left;
		} else {
			p = p->rb_right;
			e = e1;
		}
	}

	return e;
}

/**
 * find_mean_wl_entry - find wear-leveling entry with medium erase counter.
 * @ubi: UBI device description object
 * @root: the RB-tree where to look for
 *
 * This function looks for a wear leveling entry with medium erase counter,
 * but not greater or equivalent than the lowest erase counter plus
 * %WL_FREE_MAX_DIFF/2.
 */
static struct ubi_wl_entry *find_mean_wl_entry(struct ubi_device *ubi,
					       struct rb_root *root)
{
	struct ubi_wl_entry *e, *first, *last;

	first = rb_entry(rb_first(root), struct ubi_wl_entry, u.rb);
	last = rb_entry(rb_last(root), struct ubi_wl_entry, u.rb);

	if (last->ec - first->ec < WL_FREE_MAX_DIFF) {
		e = rb_entry(root->rb_node, struct ubi_wl_entry, u.rb);

		/*
		 * If no fastmap has been written and fm_anchor is not
		 * reserved and this WL entry can be used as anchor PEB
		 * hold it back and return the second best WL entry such
		 * that fastmap can use the anchor PEB later.
		 */
		e = may_reserve_for_fm(ubi, e, root);
	} else
		e = find_wl_entry(ubi, root, WL_FREE_MAX_DIFF/2, 0);

	return e;
}

/**
 * wl_get_wle - get a mean wl entry to be used by ubi_wl_get_peb() or
 * refill_wl_user_pool().
 * @ubi: UBI device description object
 *
 * This function returns a wear leveling entry in case of success and
 * NULL in case of failure.
 */
static struct ubi_wl_entry *wl_get_wle(struct ubi_device *ubi)
{
	struct ubi_wl_entry *e;

	e = find_mean_wl_entry(ubi, &ubi->free);
	if (!e) {
		ubi_err(ubi, "no free eraseblocks");
		return NULL;
	}

	self_check_in_wl_tree(ubi, e, &ubi->free);

	/*
	 * Move the physical eraseblock to the protection queue where it will
	 * be protected from being moved for some time.
	 */
	rb_erase(&e->u.rb, &ubi->free);
	ubi->free_count--;
	dbg_wl("PEB %d EC %d", e->pnum, e->ec);

	return e;
}

/**
 * prot_queue_del - remove a physical eraseblock from the protection queue.
 * @ubi: UBI device description object
 * @pnum: the physical eraseblock to remove
 *
 * This function deletes PEB @pnum from the protection queue and returns zero
 * in case of success and %-ENODEV if the PEB was not found.
 */
static int prot_queue_del(struct ubi_device *ubi, int pnum)
{
	struct ubi_wl_entry *e;

	e = ubi->lookuptbl[pnum];
	if (!e)
		return -ENODEV;

	if (self_check_in_pq(ubi, e))
		return -ENODEV;

	list_del(&e->u.list);
	dbg_wl("deleted PEB %d from the protection queue", e->pnum);
	return 0;
}

/**
 * ubi_sync_erase - synchronously erase a physical eraseblock.
 * @ubi: UBI device description object
 * @e: the physical eraseblock to erase
 * @torture: if the physical eraseblock has to be tortured
 *
 * This function returns zero in case of success and a negative error code in
 * case of failure.
 */
int ubi_sync_erase(struct ubi_device *ubi, struct ubi_wl_entry *e, int torture)
{
	int err;
	struct ubi_ec_hdr *ec_hdr;
	unsigned long long ec = e->ec;

	dbg_wl("erase PEB %d, old EC %llu", e->pnum, ec);

	err = self_check_ec(ubi, e->pnum, e->ec);
	if (err)
		return -EINVAL;

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

	err = ubi_io_sync_erase(ubi, e->pnum, torture);
	if (err < 0)
		goto out_free;

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

	dbg_wl("erased PEB %d, new EC %llu", e->pnum, ec);

	ec_hdr->ec = cpu_to_be64(ec);

	err = ubi_io_write_ec_hdr(ubi, e->pnum, ec_hdr);
	if (err)
		goto out_free;

	e->ec = ec;
	spin_lock(&ubi->wl_lock);
	if (e->ec > ubi->max_ec)
		ubi->max_ec = e->ec;
	spin_unlock(&ubi->wl_lock);

out_free:
	kfree(ec_hdr);
	return err;
}

/**
 * serve_prot_queue - check if it is time to stop protecting PEBs.
 * @ubi: UBI device description object
 *
 * This function is called after each erase operation and removes PEBs from the
 * tail of the protection queue. These PEBs have been protected for long enough
 * and should be moved to the used tree.
 */
static void serve_prot_queue(struct ubi_device *ubi)
{
	struct ubi_wl_entry *e, *tmp;
	int count;

	/*
	 * There may be several protected physical eraseblock to remove,
	 * process them all.
	 */
repeat:
	count = 0;
	spin_lock(&ubi->wl_lock);
	list_for_each_entry_safe(e, tmp, &ubi->pq[ubi->pq_head], u.list) {
		dbg_wl("PEB %d EC %d protection over, move to used tree",
			e->pnum, e->ec);

		list_del(&e->u.list);
		wl_tree_add(e, &ubi->used);
		if (count++ > 32) {
			/*
			 * Let's be nice and avoid holding the spinlock for
			 * too long.
			 */
			spin_unlock(&ubi->wl_lock);
			cond_resched();
			goto repeat;
		}
	}

	ubi->pq_head += 1;
	if (ubi->pq_head == UBI_PROT_QUEUE_LEN)
		ubi->pq_head = 0;
	ubi_assert(ubi->pq_head >= 0 && ubi->pq_head < UBI_PROT_QUEUE_LEN);
	spin_unlock(&ubi->wl_lock);
}

/**
 * __schedule_ubi_work - schedule a work.
 * @ubi: UBI device description object
 * @wrk: the work to schedule
 *
 * This function adds a work defined by @wrk to the tail of the pending works
 * list. Can only be used if ubi->work_sem is already held in read mode!
 */
static void __schedule_ubi_work(struct ubi_device *ubi, struct ubi_work *wrk)
{
	spin_lock(&ubi->wl_lock);
	list_add_tail(&wrk->list, &ubi->works);
	ubi_assert(ubi->works_count >= 0);
	ubi->works_count += 1;
	if (ubi->thread_enabled && !ubi_dbg_is_bgt_disabled(ubi))
		wake_up_process(ubi->bgt_thread);
	spin_unlock(&ubi->wl_lock);
}

/**
 * schedule_ubi_work - schedule a work.
 * @ubi: UBI device description object
 * @wrk: the work to schedule
 *
 * This function adds a work defined by @wrk to the tail of the pending works
 * list.
 */
static void schedule_ubi_work(struct ubi_device *ubi, struct ubi_work *wrk)
{
	down_read(&ubi->work_sem);
	__schedule_ubi_work(ubi, wrk);
	up_read(&ubi->work_sem);
}

static int erase_worker(struct ubi_device *ubi, struct ubi_work *wl_wrk,
			int shutdown);

/**
 * schedule_erase - schedule an erase work.
 * @ubi: UBI device description object
 * @e: the WL entry of the physical eraseblock to erase
 * @vol_id: the volume ID that last used this PEB
 * @lnum: the last used logical eraseblock number for the PEB
 * @torture: if the physical eraseblock has to be tortured
 * @nested: denotes whether the work_sem is already held
 *
 * This function returns zero in case of success and a %-ENOMEM in case of
 * failure.
 */
static int schedule_erase(struct ubi_device *ubi, struct ubi_wl_entry *e,
			  int vol_id, int lnum, int torture, bool nested)
{
	struct ubi_work *wl_wrk;

	ubi_assert(e);

	dbg_wl("schedule erasure of PEB %d, EC %d, torture %d",
	       e->pnum, e->ec, torture);

	wl_wrk = kmalloc(sizeof(struct ubi_work), GFP_NOFS);
	if (!wl_wrk)
		return -ENOMEM;

	wl_wrk->func = &erase_worker;
	wl_wrk->e = e;
	wl_wrk->vol_id = vol_id;
	wl_wrk->lnum = lnum;
	wl_wrk->torture = torture;

	if (nested)
		__schedule_ubi_work(ubi, wl_wrk);
	else
		schedule_ubi_work(ubi, wl_wrk);
	return 0;
}

static int __erase_worker(struct ubi_device *ubi, struct ubi_work *wl_wrk);
/**
 * do_sync_erase - run the erase worker synchronously.
 * @ubi: UBI device description object
 * @e: the WL entry of the physical eraseblock to erase
 * @vol_id: the volume ID that last used this PEB
 * @lnum: the last used logical eraseblock number for the PEB
 * @torture: if the physical eraseblock has to be tortured
 *
 */
static int do_sync_erase(struct ubi_device *ubi, struct ubi_wl_entry *e,
			 int vol_id, int lnum, int torture)
{
	struct ubi_work wl_wrk;

	dbg_wl("sync erase of PEB %i", e->pnum);

	wl_wrk.e = e;
	wl_wrk.vol_id = vol_id;
	wl_wrk.lnum = lnum;
	wl_wrk.torture = torture;

	return __erase_worker(ubi, &wl_wrk);
}

static int ensure_wear_leveling(struct ubi_device *ubi, int nested);
/**
 * wear_leveling_worker - wear-leveling worker function.
 * @ubi: UBI device description object
 * @wrk: the work object
 * @shutdown: non-zero if the worker has to free memory and exit
 * because the WL-subsystem is shutting down
 *
 * This function copies a more worn out physical eraseblock to a less worn out
 * one. Returns zero in case of success and a negative error code in case of
 * failure.
 */
static int wear_leveling_worker(struct ubi_device *ubi, struct ubi_work *wrk,
				int shutdown)
{
	int err, scrubbing = 0, torture = 0, protect = 0, erroneous = 0;
	int erase = 0, keep = 0, vol_id = -1, lnum = -1;
	struct ubi_wl_entry *e1, *e2;
	struct ubi_vid_io_buf *vidb;
	struct ubi_vid_hdr *vid_hdr;
	int dst_leb_clean = 0;

	kfree(wrk);
	if (shutdown)
		return 0;

	vidb = ubi_alloc_vid_buf(ubi, GFP_NOFS);
	if (!vidb)
		return -ENOMEM;

	vid_hdr = ubi_get_vid_hdr(vidb);

	down_read(&ubi->fm_eba_sem);
	mutex_lock(&ubi->move_mutex);
	spin_lock(&ubi->wl_lock);
	ubi_assert(!ubi->move_from && !ubi->move_to);
	ubi_assert(!ubi->move_to_put);

#ifdef CONFIG_MTD_UBI_FASTMAP
	if (!next_peb_for_wl(ubi) ||
#else
	if (!ubi->free.rb_node ||
#endif
	    (!ubi->used.rb_node && !ubi->scrub.rb_node)) {
		/*
		 * No free physical eraseblocks? Well, they must be waiting in
		 * the queue to be erased. Cancel movement - it will be
		 * triggered again when a free physical eraseblock appears.
		 *
		 * No used physical eraseblocks? They must be temporarily
		 * protected from being moved. They will be moved to the
		 * @ubi->used tree later and the wear-leveling will be
		 * triggered again.
		 */
		dbg_wl("cancel WL, a list is empty: free %d, used %d",
		       !ubi->free.rb_node, !ubi->used.rb_node);
		goto out_cancel;
	}

#ifdef CONFIG_MTD_UBI_FASTMAP
	e1 = find_anchor_wl_entry(&ubi->used);
	if (e1 && ubi->fm_anchor &&
	    (ubi->fm_anchor->ec - e1->ec >= UBI_WL_THRESHOLD)) {
		ubi->fm_do_produce_anchor = 1;
		/*
		 * fm_anchor is no longer considered a good anchor.
		 * NULL assignment also prevents multiple wear level checks
		 * of this PEB.
		 */
		wl_tree_add(ubi->fm_anchor, &ubi->free);
		ubi->fm_anchor = NULL;
		ubi->free_count++;
	}

	if (ubi->fm_do_produce_anchor) {
		if (!e1)
			goto out_cancel;
		e2 = get_peb_for_wl(ubi);
		if (!e2)
			goto out_cancel;

		self_check_in_wl_tree(ubi, e1, &ubi->used);
		rb_erase(&e1->u.rb, &ubi->used);
		dbg_wl("anchor-move PEB %d to PEB %d", e1->pnum, e2->pnum);
		ubi->fm_do_produce_anchor = 0;
	} else if (!ubi->scrub.rb_node) {
#else
	if (!ubi->scrub.rb_node) {
#endif
		/*
		 * Now pick the least worn-out used physical eraseblock and a
		 * highly worn-out free physical eraseblock. If the erase
		 * counters differ much enough, start wear-leveling.
		 */
		e1 = rb_entry(rb_first(&ubi->used), struct ubi_wl_entry, u.rb);
		e2 = get_peb_for_wl(ubi);
		if (!e2)
			goto out_cancel;

		if (!(e2->ec - e1->ec >= UBI_WL_THRESHOLD)) {
			dbg_wl("no WL needed: min used EC %d, max free EC %d",
			       e1->ec, e2->ec);

			/* Give the unused PEB back */
			wl_tree_add(e2, &ubi->free);
			ubi->free_count++;
			goto out_cancel;
		}
		self_check_in_wl_tree(ubi, e1, &ubi->used);
		rb_erase(&e1->u.rb, &ubi->used);
		dbg_wl("move PEB %d EC %d to PEB %d EC %d",
		       e1->pnum, e1->ec, e2->pnum, e2->ec);
	} else {
		/* Perform scrubbing */
		scrubbing = 1;
		e1 = rb_entry(rb_first(&ubi->scrub), struct ubi_wl_entry, u.rb);
		e2 = get_peb_for_wl(ubi);
		if (!e2)
			goto out_cancel;

		self_check_in_wl_tree(ubi, e1, &ubi->scrub);
		rb_erase(&e1->u.rb, &ubi->scrub);
		dbg_wl("scrub PEB %d to PEB %d", e1->pnum, e2->pnum);
	}

	ubi->move_from = e1;
	ubi->move_to = e2;
	spin_unlock(&ubi->wl_lock);

	/*
	 * Now we are going to copy physical eraseblock @e1->pnum to @e2->pnum.
	 * We so far do not know which logical eraseblock our physical
	 * eraseblock (@e1) belongs to. We have to read the volume identifier
	 * header first.
	 *
	 * Note, we are protected from this PEB being unmapped and erased. The
	 * 'ubi_wl_put_peb()' would wait for moving to be finished if the PEB
	 * which is being moved was unmapped.
	 */

	err = ubi_io_read_vid_hdr(ubi, e1->pnum, vidb, 0);
	if (err && err != UBI_IO_BITFLIPS) {
		dst_leb_clean = 1;
		if (err == UBI_IO_FF) {
			/*
			 * We are trying to move PEB without a VID header. UBI
			 * always write VID headers shortly after the PEB was
			 * given, so we have a situation when it has not yet
			 * had a chance to write it, because it was preempted.
			 * So add this PEB to the protection queue so far,
			 * because presumably more data will be written there
			 * (including the missing VID header), and then we'll
			 * move it.
			 */
			dbg_wl("PEB %d has no VID header", e1->pnum);
			protect = 1;
			goto out_not_moved;
		} else if (err == UBI_IO_FF_BITFLIPS) {
			/*
			 * The same situation as %UBI_IO_FF, but bit-flips were
			 * detected. It is better to schedule this PEB for
			 * scrubbing.
			 */
			dbg_wl("PEB %d has no VID header but has bit-flips",
			       e1->pnum);
			scrubbing = 1;
			goto out_not_moved;
		} else if (ubi->fast_attach && err == UBI_IO_BAD_HDR_EBADMSG) {
			/*
			 * While a full scan would detect interrupted erasures
			 * at attach time we can face them here when attached from
			 * Fastmap.
			 */
			dbg_wl("PEB %d has ECC errors, maybe from an interrupted erasure",
			       e1->pnum);
			erase = 1;
			goto out_not_moved;
		}

		ubi_err(ubi, "error %d while reading VID header from PEB %d",
			err, e1->pnum);
		goto out_error;
	}

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

	err = ubi_eba_copy_leb(ubi, e1->pnum, e2->pnum, vidb);
	if (err) {
		if (err == MOVE_CANCEL_RACE) {
			/*
			 * The LEB has not been moved because the volume is
			 * being deleted or the PEB has been put meanwhile. We
			 * should prevent this PEB from being selected for
			 * wear-leveling movement again, so put it to the
			 * protection queue.
			 */
			protect = 1;
			dst_leb_clean = 1;
			goto out_not_moved;
		}
		if (err == MOVE_RETRY) {
			scrubbing = 1;
			dst_leb_clean = 1;
			goto out_not_moved;
		}
		if (err == MOVE_TARGET_BITFLIPS || err == MOVE_TARGET_WR_ERR ||
		    err == MOVE_TARGET_RD_ERR) {
			/*
			 * Target PEB had bit-flips or write error - torture it.
			 */
			torture = 1;
			keep = 1;
			goto out_not_moved;
		}

		if (err == MOVE_SOURCE_RD_ERR) {
			/*
			 * An error happened while reading the source PEB. Do
			 * not switch to R/O mode in this case, and give the
			 * upper layers a possibility to recover from this,
			 * e.g. by unmapping corresponding LEB. Instead, just
			 * put this PEB to the @ubi->erroneous list to prevent
			 * UBI from trying to move it over and over again.
			 */
			if (ubi->erroneous_peb_count > ubi->max_erroneous) {
				ubi_err(ubi, "too many erroneous eraseblocks (%d)",
					ubi->erroneous_peb_count);
				goto out_error;
			}
			dst_leb_clean = 1;
			erroneous = 1;
			goto out_not_moved;
		}

		if (err < 0)
			goto out_error;

		ubi_assert(0);
	}

	/* The PEB has been successfully moved */
	if (scrubbing)
		ubi_msg(ubi, "scrubbed PEB %d (LEB %d:%d), data moved to PEB %d",
			e1->pnum, vol_id, lnum, e2->pnum);
	ubi_free_vid_buf(vidb);

	spin_lock(&ubi->wl_lock);
	if (!ubi->move_to_put) {
		wl_tree_add(e2, &ubi->used);
		e2 = NULL;
	}
	ubi->move_from = ubi->move_to = NULL;
	ubi->move_to_put = ubi->wl_scheduled = 0;
	spin_unlock(&ubi->wl_lock);

	err = do_sync_erase(ubi, e1, vol_id, lnum, 0);
	if (err) {
		if (e2) {
			spin_lock(&ubi->wl_lock);
			wl_entry_destroy(ubi, e2);
			spin_unlock(&ubi->wl_lock);
		}
		goto out_ro;
	}

	if (e2) {
		/*
		 * Well, the target PEB was put meanwhile, schedule it for
		 * erasure.
		 */
		dbg_wl("PEB %d (LEB %d:%d) was put meanwhile, erase",
		       e2->pnum, vol_id, lnum);
		err = do_sync_erase(ubi, e2, vol_id, lnum, 0);
		if (err)
			goto out_ro;
	}

	dbg_wl("done");
	mutex_unlock(&ubi->move_mutex);
	up_read(&ubi->fm_eba_sem);
	return 0;

	/*
	 * For some reasons the LEB was not moved, might be an error, might be
	 * something else. @e1 was not changed, so return it back. @e2 might
	 * have been changed, schedule it for erasure.
	 */
out_not_moved:
	if (vol_id != -1)
		dbg_wl("cancel moving PEB %d (LEB %d:%d) to PEB %d (%d)",
		       e1->pnum, vol_id, lnum, e2->pnum, err);
	else
		dbg_wl("cancel moving PEB %d to PEB %d (%d)",
		       e1->pnum, e2->pnum, err);
	spin_lock(&ubi->wl_lock);
	if (protect)
		prot_queue_add(ubi, e1);
	else if (erroneous) {
		wl_tree_add(e1, &ubi->erroneous);
		ubi->erroneous_peb_count += 1;
	} else if (scrubbing)
		wl_tree_add(e1, &ubi->scrub);
	else if (keep)
		wl_tree_add(e1, &ubi->used);
	if (dst_leb_clean) {
		wl_tree_add(e2, &ubi->free);
		ubi->free_count++;
	}

	ubi_assert(!ubi->move_to_put);
	ubi->move_from = ubi->move_to = NULL;
	ubi->wl_scheduled = 0;
	spin_unlock(&ubi->wl_lock);

	ubi_free_vid_buf(vidb);
	if (dst_leb_clean) {
		ensure_wear_leveling(ubi, 1);
	} else {
		err = do_sync_erase(ubi, e2, vol_id, lnum, torture);
		if (err)
			goto out_ro;
	}

	if (erase) {
		err = do_sync_erase(ubi, e1, vol_id, lnum, 1);
		if (err)
			goto out_ro;
	}

	mutex_unlock(&ubi->move_mutex);
	up_read(&ubi->fm_eba_sem);
	return 0;

out_error:
	if (vol_id != -1)
		ubi_err(ubi, "error %d while moving PEB %d to PEB %d",
			err, e1->pnum, e2->pnum);
	else
		ubi_err(ubi, "error %d while moving PEB %d (LEB %d:%d) to PEB %d",
			err, e1->pnum, vol_id, lnum, e2->pnum);
	spin_lock(&ubi->wl_lock);
	ubi->move_from = ubi->move_to = NULL;
	ubi->move_to_put = ubi->wl_scheduled = 0;
	wl_entry_destroy(ubi, e1);
	wl_entry_destroy(ubi, e2);
	spin_unlock(&ubi->wl_lock);

	ubi_free_vid_buf(vidb);

out_ro:
	ubi_ro_mode(ubi);
	mutex_unlock(&ubi->move_mutex);
	up_read(&ubi->fm_eba_sem);
	ubi_assert(err != 0);
	return err < 0 ? err : -EIO;

out_cancel:
	ubi->wl_scheduled = 0;
	spin_unlock(&ubi->wl_lock);
	mutex_unlock(&ubi->move_mutex);
	up_read(&ubi->fm_eba_sem);
	ubi_free_vid_buf(vidb);
	return 0;
}

/**
 * ensure_wear_leveling - schedule wear-leveling if it is needed.
 * @ubi: UBI device description object
 * @nested: set to non-zero if this function is called from UBI worker
 *
 * This function checks if it is time to start wear-leveling and schedules it
 * if yes. This function returns zero in case of success and a negative error
 * code in case of failure.
 */
static int ensure_wear_leveling(struct ubi_device *ubi, int nested)
{
	int err = 0;
	struct ubi_work *wrk;

	spin_lock(&ubi->wl_lock);
	if (ubi->wl_scheduled)
		/* Wear-leveling is already in the work queue */
		goto out_unlock;

	/*
	 * If the ubi->scrub tree is not empty, scrubbing is needed, and the
	 * WL worker has to be scheduled anyway.
	 */
	if (!ubi->scrub.rb_node) {
#ifdef CONFIG_MTD_UBI_FASTMAP
		if (!need_wear_leveling(ubi))
			goto out_unlock;
#else
		struct ubi_wl_entry *e1;
		struct ubi_wl_entry *e2;

		if (!ubi->used.rb_node || !ubi->free.rb_node)
			/* No physical eraseblocks - no deal */
			goto out_unlock;

		/*
		 * We schedule wear-leveling only if the difference between the
		 * lowest erase counter of used physical eraseblocks and a high
		 * erase counter of free physical eraseblocks is greater than
		 * %UBI_WL_THRESHOLD.
		 */
		e1 = rb_entry(rb_first(&ubi->used), struct ubi_wl_entry, u.rb);
		e2 = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF, 0);

		if (!(e2->ec - e1->ec >= UBI_WL_THRESHOLD))
			goto out_unlock;
#endif
		dbg_wl("schedule wear-leveling");
	} else
		dbg_wl("schedule scrubbing");

	ubi->wl_scheduled = 1;
	spin_unlock(&ubi->wl_lock);

	wrk = kmalloc(sizeof(struct ubi_work), GFP_NOFS);
	if (!wrk) {
		err = -ENOMEM;
		goto out_cancel;
	}

	wrk->func = &wear_leveling_worker;
	if (nested)
		__schedule_ubi_work(ubi, wrk);
	else
		schedule_ubi_work(ubi, wrk);
	return err;

out_cancel:
	spin_lock(&ubi->wl_lock);
	ubi->wl_scheduled = 0;
out_unlock:
	spin_unlock(&ubi->wl_lock);
	return err;
}

/**
 * __erase_worker - physical eraseblock erase worker function.
 * @ubi: UBI device description object
 * @wl_wrk: the work object
 *
 * This function erases a physical eraseblock and perform torture testing if
 * needed. It also takes care about marking the physical eraseblock bad if
 * needed. Returns zero in case of success and a negative error code in case of
 * failure.
 */
static int __erase_worker(struct ubi_device *ubi, struct ubi_work *wl_wrk)
{
	struct ubi_wl_entry *e = wl_wrk->e;
	int pnum = e->pnum;
	int vol_id = wl_wrk->vol_id;
	int lnum = wl_wrk->lnum;
	int err, available_consumed = 0;

	dbg_wl("erase PEB %d EC %d LEB %d:%d",
	       pnum, e->ec, wl_wrk->vol_id, wl_wrk->lnum);

	err = ubi_sync_erase(ubi, e, wl_wrk->torture);
	if (!err) {
		spin_lock(&ubi->wl_lock);

		if (!ubi->fm_disabled && !ubi->fm_anchor &&
		    e->pnum < UBI_FM_MAX_START) {
			/*
			 * Abort anchor production, if needed it will be
			 * enabled again in the wear leveling started below.
			 */
			ubi->fm_anchor = e;
			ubi->fm_do_produce_anchor = 0;
		} else {
			wl_tree_add(e, &ubi->free);
			ubi->free_count++;
		}

		spin_unlock(&ubi->wl_lock);

		/*
		 * One more erase operation has happened, take care about
		 * protected physical eraseblocks.
		 */
		serve_prot_queue(ubi);

		/* And take care about wear-leveling */
		err = ensure_wear_leveling(ubi, 1);
		return err;
	}

	ubi_err(ubi, "failed to erase PEB %d, error %d", pnum, err);

	if (err == -EINTR || err == -ENOMEM || err == -EAGAIN ||
	    err == -EBUSY) {
		int err1;

		/* Re-schedule the LEB for erasure */
		err1 = schedule_erase(ubi, e, vol_id, lnum, 0, true);
		if (err1) {
			spin_lock(&ubi->wl_lock);
			wl_entry_destroy(ubi, e);
			spin_unlock(&ubi->wl_lock);
			err = err1;
			goto out_ro;
		}
		return err;
	}

	spin_lock(&ubi->wl_lock);
	wl_entry_destroy(ubi, e);
	spin_unlock(&ubi->wl_lock);
	if (err != -EIO)
		/*
		 * If this is not %-EIO, we have no idea what to do. Scheduling
		 * this physical eraseblock for erasure again would cause
		 * errors again and again. Well, lets switch to R/O mode.
		 */
		goto out_ro;

	/* It is %-EIO, the PEB went bad */

	if (!ubi->bad_allowed) {
		ubi_err(ubi, "bad physical eraseblock %d detected", pnum);
		goto out_ro;
	}

	spin_lock(&ubi->volumes_lock);
	if (ubi->beb_rsvd_pebs == 0) {
		if (ubi->avail_pebs == 0) {
			spin_unlock(&ubi->volumes_lock);
			ubi_err(ubi, "no reserved/available physical eraseblocks");
			goto out_ro;
		}
		ubi->avail_pebs -= 1;
		available_consumed = 1;
	}
	spin_unlock(&ubi->volumes_lock);

	ubi_msg(ubi, "mark PEB %d as bad", pnum);
	err = ubi_io_mark_bad(ubi, pnum);
	if (err)
		goto out_ro;

	spin_lock(&ubi->volumes_lock);
	if (ubi->beb_rsvd_pebs > 0) {
		if (available_consumed) {
			/*
			 * The amount of reserved PEBs increased since we last
			 * checked.
			 */
			ubi->avail_pebs += 1;
			available_consumed = 0;
		}
		ubi->beb_rsvd_pebs -= 1;
	}
	ubi->bad_peb_count += 1;
	ubi->good_peb_count -= 1;
	ubi_calculate_reserved(ubi);
	if (available_consumed)
		ubi_warn(ubi, "no PEBs in the reserved pool, used an available PEB");
	else if (ubi->beb_rsvd_pebs)
		ubi_msg(ubi, "%d PEBs left in the reserve",
			ubi->beb_rsvd_pebs);
	else
		ubi_warn(ubi, "last PEB from the reserve was used");
	spin_unlock(&ubi->volumes_lock);

	return err;

out_ro:
	if (available_consumed) {
		spin_lock(&ubi->volumes_lock);
		ubi->avail_pebs += 1;
		spin_unlock(&ubi->volumes_lock);
	}
	ubi_ro_mode(ubi);
	return err;
}

static int erase_worker(struct ubi_device *ubi, struct ubi_work *wl_wrk,
			  int shutdown)
{
	int ret;

	if (shutdown) {
		struct ubi_wl_entry *e = wl_wrk->e;

		dbg_wl("cancel erasure of PEB %d EC %d", e->pnum, e->ec);
		kfree(wl_wrk);
		wl_entry_destroy(ubi, e);
		return 0;
	}

	ret = __erase_worker(ubi, wl_wrk);
	kfree(wl_wrk);
	return ret;
}

/**
 * ubi_wl_put_peb - return a PEB to the wear-leveling sub-system.
 * @ubi: UBI device description object
 * @vol_id: the volume ID that last used this PEB
 * @lnum: the last used logical eraseblock number for the PEB
 * @pnum: physical eraseblock to return
 * @torture: if this physical eraseblock has to be tortured
 *
 * This function is called to return physical eraseblock @pnum to the pool of
 * free physical eraseblocks. The @torture flag has to be set if an I/O error
 * occurred to this @pnum and it has to be tested. This function returns zero
 * in case of success, and a negative error code in case of failure.
 */
int ubi_wl_put_peb(struct ubi_device *ubi, int vol_id, int lnum,
		   int pnum, int torture)
{
	int err;
	struct ubi_wl_entry *e;

	dbg_wl("PEB %d", pnum);
	ubi_assert(pnum >= 0);
	ubi_assert(pnum < ubi->peb_count);

	down_read(&ubi->fm_protect);

retry:
	spin_lock(&ubi->wl_lock);
	e = ubi->lookuptbl[pnum];
	if (!e) {
		/*
		 * This wl entry has been removed for some errors by other
		 * process (eg. wear leveling worker), corresponding process
		 * (except __erase_worker, which cannot concurrent with
		 * ubi_wl_put_peb) will set ubi ro_mode at the same time,
		 * just ignore this wl entry.
		 */
		spin_unlock(&ubi->wl_lock);
		up_read(&ubi->fm_protect);
		return 0;
	}
	if (e == ubi->move_from) {
		/*
		 * User is putting the physical eraseblock which was selected to
		 * be moved. It will be scheduled for erasure in the
		 * wear-leveling worker.
		 */
		dbg_wl("PEB %d is being moved, wait", pnum);
		spin_unlock(&ubi->wl_lock);

		/* Wait for the WL worker by taking the @ubi->move_mutex */
		mutex_lock(&ubi->move_mutex);
		mutex_unlock(&ubi->move_mutex);
		goto retry;
	} else if (e == ubi->move_to) {
		/*
		 * User is putting the physical eraseblock which was selected
		 * as the target the data is moved to. It may happen if the EBA
		 * sub-system already re-mapped the LEB in 'ubi_eba_copy_leb()'
		 * but the WL sub-system has not put the PEB to the "used" tree
		 * yet, but it is about to do this. So we just set a flag which
		 * will tell the WL worker that the PEB is not needed anymore
		 * and should be scheduled for erasure.
		 */
		dbg_wl("PEB %d is the target of data moving", pnum);
		ubi_assert(!ubi->move_to_put);
		ubi->move_to_put = 1;
		spin_unlock(&ubi->wl_lock);
		up_read(&ubi->fm_protect);
		return 0;
	} else {
		if (in_wl_tree(e, &ubi->used)) {
			self_check_in_wl_tree(ubi, e, &ubi->used);
			rb_erase(&e->u.rb, &ubi->used);
		} else if (in_wl_tree(e, &ubi->scrub)) {
			self_check_in_wl_tree(ubi, e, &ubi->scrub);
			rb_erase(&e->u.rb, &ubi->scrub);
		} else if (in_wl_tree(e, &ubi->erroneous)) {
			self_check_in_wl_tree(ubi, e, &ubi->erroneous);
			rb_erase(&e->u.rb, &ubi->erroneous);
			ubi->erroneous_peb_count -= 1;
			ubi_assert(ubi->erroneous_peb_count >= 0);
			/* Erroneous PEBs should be tortured */
			torture = 1;
		} else {
			err = prot_queue_del(ubi, e->pnum);
			if (err) {
				ubi_err(ubi, "PEB %d not found", pnum);
				ubi_ro_mode(ubi);
				spin_unlock(&ubi->wl_lock);
				up_read(&ubi->fm_protect);
				return err;
			}
		}
	}
	spin_unlock(&ubi->wl_lock);

	err = schedule_erase(ubi, e, vol_id, lnum, torture, false);
	if (err) {
		spin_lock(&ubi->wl_lock);
		wl_tree_add(e, &ubi->used);
		spin_unlock(&ubi->wl_lock);
	}

	up_read(&ubi->fm_protect);
	return err;
}

/**
 * ubi_wl_scrub_peb - schedule a physical eraseblock for scrubbing.
 * @ubi: UBI device description object
 * @pnum: the physical eraseblock to schedule
 *
 * If a bit-flip in a physical eraseblock is detected, this physical eraseblock
 * needs scrubbing. This function schedules a physical eraseblock for
 * scrubbing which is done in background. This function returns zero in case of
 * success and a negative error code in case of failure.
 */
int ubi_wl_scrub_peb(struct ubi_device *ubi, int pnum)
{
	struct ubi_wl_entry *e;

	ubi_msg(ubi, "schedule PEB %d for scrubbing", pnum);

retry:
	spin_lock(&ubi->wl_lock);
	e = ubi->lookuptbl[pnum];
	if (e == ubi->move_from || in_wl_tree(e, &ubi->scrub) ||
				   in_wl_tree(e, &ubi->erroneous)) {
		spin_unlock(&ubi->wl_lock);
		return 0;
	}

	if (e == ubi->move_to) {
		/*
		 * This physical eraseblock was used to move data to. The data
		 * was moved but the PEB was not yet inserted to the proper
		 * tree. We should just wait a little and let the WL worker
		 * proceed.
		 */
		spin_unlock(&ubi->wl_lock);
		dbg_wl("the PEB %d is not in proper tree, retry", pnum);
		yield();
		goto retry;
	}

	if (in_wl_tree(e, &ubi->used)) {
		self_check_in_wl_tree(ubi, e, &ubi->used);
		rb_erase(&e->u.rb, &ubi->used);
	} else {
		int err;

		err = prot_queue_del(ubi, e->pnum);
		if (err) {
			ubi_err(ubi, "PEB %d not found", pnum);
			ubi_ro_mode(ubi);
			spin_unlock(&ubi->wl_lock);
			return err;
		}
	}

	wl_tree_add(e, &ubi->scrub);
	spin_unlock(&ubi->wl_lock);

	/*
	 * Technically scrubbing is the same as wear-leveling, so it is done
	 * by the WL worker.
	 */
	return ensure_wear_leveling(ubi, 0);
}

/**
 * ubi_wl_flush - flush all pending works.
 * @ubi: UBI device description object
 * @vol_id: the volume id to flush for
 * @lnum: the logical eraseblock number to flush for
 *
 * This function executes all pending works for a particular volume id /
 * logical eraseblock number pair. If either value is set to %UBI_ALL, then it
 * acts as a wildcard for all of the corresponding volume numbers or logical
 * eraseblock numbers. It returns zero in case of success and a negative error
 * code in case of failure.
 */
int ubi_wl_flush(struct ubi_device *ubi, int vol_id, int lnum)
{
	int err = 0;
	int found = 1;

	/*
	 * Erase while the pending works queue is not empty, but not more than
	 * the number of currently pending works.
	 */
	dbg_wl("flush pending work for LEB %d:%d (%d pending works)",
	       vol_id, lnum, ubi->works_count);

	while (found) {
		struct ubi_work *wrk, *tmp;
		found = 0;

		down_read(&ubi->work_sem);
		spin_lock(&ubi->wl_lock);
		list_for_each_entry_safe(wrk, tmp, &ubi->works, list) {
			if ((vol_id == UBI_ALL || wrk->vol_id == vol_id) &&
			    (lnum == UBI_ALL || wrk->lnum == lnum)) {
				list_del(&wrk->list);
				ubi->works_count -= 1;
				ubi_assert(ubi->works_count >= 0);
				spin_unlock(&ubi->wl_lock);

				err = wrk->func(ubi, wrk, 0);
				if (err) {
					up_read(&ubi->work_sem);
					return err;
				}

				spin_lock(&ubi->wl_lock);
				found = 1;
				break;
			}
		}
		spin_unlock(&ubi->wl_lock);
		up_read(&ubi->work_sem);
	}

	/*
	 * Make sure all the works which have been done in parallel are
	 * finished.
	 */
	down_write(&ubi->work_sem);
	up_write(&ubi->work_sem);

	return err;
}

static bool scrub_possible(struct ubi_device *ubi, struct ubi_wl_entry *e)
{
	if (in_wl_tree(e, &ubi->scrub))
		return false;
	else if (in_wl_tree(e, &ubi->erroneous))
		return false;
	else if (ubi->move_from == e)
		return false;
	else if (ubi->move_to == e)
		return false;

	return true;
}

/**
 * ubi_bitflip_check - Check an eraseblock for bitflips and scrub it if needed.
 * @ubi: UBI device description object
 * @pnum: the physical eraseblock to schedule
 * @force: don't read the block, assume bitflips happened and take action.
 *
 * This function reads the given eraseblock and checks if bitflips occured.
 * In case of bitflips, the eraseblock is scheduled for scrubbing.
 * If scrubbing is forced with @force, the eraseblock is not read,
 * but scheduled for scrubbing right away.
 *
 * Returns:
 * %EINVAL, PEB is out of range
 * %ENOENT, PEB is no longer used by UBI
 * %EBUSY, PEB cannot be checked now or a check is currently running on it
 * %EAGAIN, bit flips happened but scrubbing is currently not possible
 * %EUCLEAN, bit flips happened and PEB is scheduled for scrubbing
 * %0, no bit flips detected
 */
int ubi_bitflip_check(struct ubi_device *ubi, int pnum, int force)
{
	int err = 0;
	struct ubi_wl_entry *e;

	if (pnum < 0 || pnum >= ubi->peb_count) {
		err = -EINVAL;
		goto out;
	}

	/*
	 * Pause all parallel work, otherwise it can happen that the
	 * erase worker frees a wl entry under us.
	 */
	down_write(&ubi->work_sem);

	/*
	 * Make sure that the wl entry does not change state while
	 * inspecting it.
	 */
	spin_lock(&ubi->wl_lock);
	e = ubi->lookuptbl[pnum];
	if (!e) {
		spin_unlock(&ubi->wl_lock);
		err = -ENOENT;
		goto out_resume;
	}

	/*
	 * Does it make sense to check this PEB?
	 */
	if (!scrub_possible(ubi, e)) {
		spin_unlock(&ubi->wl_lock);
		err = -EBUSY;
		goto out_resume;
	}
	spin_unlock(&ubi->wl_lock);

	if (!force) {
		mutex_lock(&ubi->buf_mutex);
		err = ubi_io_read(ubi, ubi->peb_buf, pnum, 0, ubi->peb_size);
		mutex_unlock(&ubi->buf_mutex);
	}

	if (force || err == UBI_IO_BITFLIPS) {
		/*
		 * Okay, bit flip happened, let's figure out what we can do.
		 */
		spin_lock(&ubi->wl_lock);

		/*
		 * Recheck. We released wl_lock, UBI might have killed the
		 * wl entry under us.
		 */
		e = ubi->lookuptbl[pnum];
		if (!e) {
			spin_unlock(&ubi->wl_lock);
			err = -ENOENT;
			goto out_resume;
		}

		/*
		 * Need to re-check state
		 */
		if (!scrub_possible(ubi, e)) {
			spin_unlock(&ubi->wl_lock);
			err = -EBUSY;
			goto out_resume;
		}

		if (in_pq(ubi, e)) {
			prot_queue_del(ubi, e->pnum);
			wl_tree_add(e, &ubi->scrub);
			spin_unlock(&ubi->wl_lock);

			err = ensure_wear_leveling(ubi, 1);
		} else if (in_wl_tree(e, &ubi->used)) {
			rb_erase(&e->u.rb, &ubi->used);
			wl_tree_add(e, &ubi->scrub);
			spin_unlock(&ubi->wl_lock);

			err = ensure_wear_leveling(ubi, 1);
		} else if (in_wl_tree(e, &ubi->free)) {
			rb_erase(&e->u.rb, &ubi->free);
			ubi->free_count--;
			spin_unlock(&ubi->wl_lock);

			/*
			 * This PEB is empty we can schedule it for
			 * erasure right away. No wear leveling needed.
			 */
			err = schedule_erase(ubi, e, UBI_UNKNOWN, UBI_UNKNOWN,
					     force ? 0 : 1, true);
		} else {
			spin_unlock(&ubi->wl_lock);
			err = -EAGAIN;
		}

		if (!err && !force)
			err = -EUCLEAN;
	} else {
		err = 0;
	}

out_resume:
	up_write(&ubi->work_sem);
out:

	return err;
}

/**
 * tree_destroy - destroy an RB-tree.
 * @ubi: UBI device description object
 * @root: the root of the tree to destroy
 */
static void tree_destroy(struct ubi_device *ubi, struct rb_root *root)
{
	struct rb_node *rb;
	struct ubi_wl_entry *e;

	rb = root->rb_node;
	while (rb) {
		if (rb->rb_left)
			rb = rb->rb_left;
		else if (rb->rb_right)
			rb = rb->rb_right;
		else {
			e = rb_entry(rb, struct ubi_wl_entry, u.rb);

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

			wl_entry_destroy(ubi, e);
		}
	}
}

/**
 * ubi_thread - UBI background thread.
 * @u: the UBI device description object pointer
 */
int ubi_thread(void *u)
{
	int failures = 0;
	struct ubi_device *ubi = u;

	ubi_msg(ubi, "background thread \"%s\" started, PID %d",
		ubi->bgt_name, task_pid_nr(current));

	set_freezable();
	for (;;) {
		int err;

		if (kthread_should_stop())
			break;

		if (try_to_freeze())
			continue;

		spin_lock(&ubi->wl_lock);
		if (list_empty(&ubi->works) || ubi->ro_mode ||
		    !ubi->thread_enabled || ubi_dbg_is_bgt_disabled(ubi)) {
			set_current_state(TASK_INTERRUPTIBLE);
			spin_unlock(&ubi->wl_lock);

			/*
			 * Check kthread_should_stop() after we set the task
			 * state to guarantee that we either see the stop bit
			 * and exit or the task state is reset to runnable such
			 * that it's not scheduled out indefinitely and detects
			 * the stop bit at kthread_should_stop().
			 */
			if (kthread_should_stop()) {
				set_current_state(TASK_RUNNING);
				break;
			}

			schedule();
			continue;
		}
		spin_unlock(&ubi->wl_lock);

		err = do_work(ubi, NULL);
		if (err) {
			ubi_err(ubi, "%s: work failed with error code %d",
				ubi->bgt_name, err);
			if (failures++ > WL_MAX_FAILURES) {
				/*
				 * Too many failures, disable the thread and
				 * switch to read-only mode.
				 */
				ubi_msg(ubi, "%s: %d consecutive failures",
					ubi->bgt_name, WL_MAX_FAILURES);
				ubi_ro_mode(ubi);
				ubi->thread_enabled = 0;
				continue;
			}
		} else
			failures = 0;

		cond_resched();
	}

	dbg_wl("background thread \"%s\" is killed", ubi->bgt_name);
	ubi->thread_enabled = 0;
	return 0;
}

/**
 * shutdown_work - shutdown all pending works.
 * @ubi: UBI device description object
 */
static void shutdown_work(struct ubi_device *ubi)
{
	while (!list_empty(&ubi->works)) {
		struct ubi_work *wrk;

		wrk = list_entry(ubi->works.next, struct ubi_work, list);
		list_del(&wrk->list);
		wrk->func(ubi, wrk, 1);
		ubi->works_count -= 1;
		ubi_assert(ubi->works_count >= 0);
	}
}

/**
 * erase_aeb - erase a PEB given in UBI attach info PEB
 * @ubi: UBI device description object
 * @aeb: UBI attach info PEB
 * @sync: If true, erase synchronously. Otherwise schedule for erasure
 */
static int erase_aeb(struct ubi_device *ubi, struct ubi_ainf_peb *aeb, bool sync)
{
	struct ubi_wl_entry *e;
	int err;

	e = kmem_cache_alloc(ubi_wl_entry_slab, GFP_KERNEL);
	if (!e)
		return -ENOMEM;

	e->pnum = aeb->pnum;
	e->ec = aeb->ec;
	ubi->lookuptbl[e->pnum] = e;

	if (sync) {
		err = ubi_sync_erase(ubi, e, false);
		if (err)
			goto out_free;

		wl_tree_add(e, &ubi->free);
		ubi->free_count++;
	} else {
		err = schedule_erase(ubi, e, aeb->vol_id, aeb->lnum, 0, false);
		if (err)
			goto out_free;
	}

	return 0;

out_free:
	wl_entry_destroy(ubi, e);

	return err;
}

/**
 * ubi_wl_init - initialize the WL sub-system using attaching information.
 * @ubi: UBI device description object
 * @ai: attaching information
 *
 * This function returns zero in case of success, and a negative error code in
 * case of failure.
 */
int ubi_wl_init(struct ubi_device *ubi, struct ubi_attach_info *ai)
{
	int err, i, reserved_pebs, found_pebs = 0;
	struct rb_node *rb1, *rb2;
	struct ubi_ainf_volume *av;
	struct ubi_ainf_peb *aeb, *tmp;
	struct ubi_wl_entry *e;

	ubi->used = ubi->erroneous = ubi->free = ubi->scrub = RB_ROOT;
	spin_lock_init(&ubi->wl_lock);
	mutex_init(&ubi->move_mutex);
	init_rwsem(&ubi->work_sem);
	ubi->max_ec = ai->max_ec;
	INIT_LIST_HEAD(&ubi->works);

	sprintf(ubi->bgt_name, UBI_BGT_NAME_PATTERN, ubi->ubi_num);

	err = -ENOMEM;
	ubi->lookuptbl = kcalloc(ubi->peb_count, sizeof(void *), GFP_KERNEL);
	if (!ubi->lookuptbl)
		return err;

	for (i = 0; i < UBI_PROT_QUEUE_LEN; i++)
		INIT_LIST_HEAD(&ubi->pq[i]);
	ubi->pq_head = 0;

	ubi->free_count = 0;
	list_for_each_entry_safe(aeb, tmp, &ai->erase, u.list) {
		cond_resched();

		err = erase_aeb(ubi, aeb, false);
		if (err)
			goto out_free;

		found_pebs++;
	}

	list_for_each_entry(aeb, &ai->free, u.list) {
		cond_resched();

		e = kmem_cache_alloc(ubi_wl_entry_slab, GFP_KERNEL);
		if (!e) {
			err = -ENOMEM;
			goto out_free;
		}

		e->pnum = aeb->pnum;
		e->ec = aeb->ec;
		ubi_assert(e->ec >= 0);

		wl_tree_add(e, &ubi->free);
		ubi->free_count++;

		ubi->lookuptbl[e->pnum] = e;

		found_pebs++;
	}

	ubi_rb_for_each_entry(rb1, av, &ai->volumes, rb) {
		ubi_rb_for_each_entry(rb2, aeb, &av->root, u.rb) {
			cond_resched();

			e = kmem_cache_alloc(ubi_wl_entry_slab, GFP_KERNEL);
			if (!e) {
				err = -ENOMEM;
				goto out_free;
			}

			e->pnum = aeb->pnum;
			e->ec = aeb->ec;
			ubi->lookuptbl[e->pnum] = e;

			if (!aeb->scrub) {
				dbg_wl("add PEB %d EC %d to the used tree",
				       e->pnum, e->ec);
				wl_tree_add(e, &ubi->used);
			} else {
				dbg_wl("add PEB %d EC %d to the scrub tree",
				       e->pnum, e->ec);
				wl_tree_add(e, &ubi->scrub);
			}

			found_pebs++;
		}
	}

	list_for_each_entry(aeb, &ai->fastmap, u.list) {
		cond_resched();

		e = ubi_find_fm_block(ubi, aeb->pnum);

		if (e) {
			ubi_assert(!ubi->lookuptbl[e->pnum]);
			ubi->lookuptbl[e->pnum] = e;
		} else {
			bool sync = false;

			/*
			 * Usually old Fastmap PEBs are scheduled for erasure
			 * and we don't have to care about them but if we face
			 * an power cut before scheduling them we need to
			 * take care of them here.
			 */
			if (ubi->lookuptbl[aeb->pnum])
				continue;

			/*
			 * The fastmap update code might not find a free PEB for
			 * writing the fastmap anchor to and then reuses the
			 * current fastmap anchor PEB. When this PEB gets erased
			 * and a power cut happens before it is written again we
			 * must make sure that the fastmap attach code doesn't
			 * find any outdated fastmap anchors, hence we erase the
			 * outdated fastmap anchor PEBs synchronously here.
			 */
			if (aeb->vol_id == UBI_FM_SB_VOLUME_ID)
				sync = true;

			err = erase_aeb(ubi, aeb, sync);
			if (err)
				goto out_free;
		}

		found_pebs++;
	}

	dbg_wl("found %i PEBs", found_pebs);

	ubi_assert(ubi->good_peb_count == found_pebs);

	reserved_pebs = WL_RESERVED_PEBS;
	ubi_fastmap_init(ubi, &reserved_pebs);

	if (ubi->avail_pebs < reserved_pebs) {
		ubi_err(ubi, "no enough physical eraseblocks (%d, need %d)",
			ubi->avail_pebs, reserved_pebs);
		if (ubi->corr_peb_count)
			ubi_err(ubi, "%d PEBs are corrupted and not used",
				ubi->corr_peb_count);
		err = -ENOSPC;
		goto out_free;
	}
	ubi->avail_pebs -= reserved_pebs;
	ubi->rsvd_pebs += reserved_pebs;

	/* Schedule wear-leveling if needed */
	err = ensure_wear_leveling(ubi, 0);
	if (err)
		goto out_free;

#ifdef CONFIG_MTD_UBI_FASTMAP
	if (!ubi->ro_mode && !ubi->fm_disabled)
		ubi_ensure_anchor_pebs(ubi);
#endif
	return 0;

out_free:
	shutdown_work(ubi);
	tree_destroy(ubi, &ubi->used);
	tree_destroy(ubi, &ubi->free);
	tree_destroy(ubi, &ubi->scrub);
	kfree(ubi->lookuptbl);
	return err;
}

/**
 * protection_queue_destroy - destroy the protection queue.
 * @ubi: UBI device description object
 */
static void protection_queue_destroy(struct ubi_device *ubi)
{
	int i;
	struct ubi_wl_entry *e, *tmp;

	for (i = 0; i < UBI_PROT_QUEUE_LEN; ++i) {
		list_for_each_entry_safe(e, tmp, &ubi->pq[i], u.list) {
			list_del(&e->u.list);
			wl_entry_destroy(ubi, e);
		}
	}
}

/**
 * ubi_wl_close - close the wear-leveling sub-system.
 * @ubi: UBI device description object
 */
void ubi_wl_close(struct ubi_device *ubi)
{
	dbg_wl("close the WL sub-system");
	ubi_fastmap_close(ubi);
	shutdown_work(ubi);
	protection_queue_destroy(ubi);
	tree_destroy(ubi, &ubi->used);
	tree_destroy(ubi, &ubi->erroneous);
	tree_destroy(ubi, &ubi->free);
	tree_destroy(ubi, &ubi->scrub);
	kfree(ubi->lookuptbl);
}

/**
 * self_check_ec - make sure that the erase counter of a PEB is correct.
 * @ubi: UBI device description object
 * @pnum: the physical eraseblock number to check
 * @ec: the erase counter to check
 *
 * This function returns zero if the erase counter of physical eraseblock @pnum
 * is equivalent to @ec, and a negative error code if not or if an error
 * occurred.
 */
static int self_check_ec(struct ubi_device *ubi, int pnum, int ec)
{
	int err;
	long long read_ec;
	struct ubi_ec_hdr *ec_hdr;

	if (!ubi_dbg_chk_gen(ubi))
		return 0;

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

	err = ubi_io_read_ec_hdr(ubi, pnum, ec_hdr, 0);
	if (err && err != UBI_IO_BITFLIPS) {
		/* The header does not have to exist */
		err = 0;
		goto out_free;
	}

	read_ec = be64_to_cpu(ec_hdr->ec);
	if (ec != read_ec && read_ec - ec > 1) {
		ubi_err(ubi, "self-check failed for PEB %d", pnum);
		ubi_err(ubi, "read EC is %lld, should be %d", read_ec, ec);
		dump_stack();
		err = 1;
	} else
		err = 0;

out_free:
	kfree(ec_hdr);
	return err;
}

/**
 * self_check_in_wl_tree - check that wear-leveling entry is in WL RB-tree.
 * @ubi: UBI device description object
 * @e: the wear-leveling entry to check
 * @root: the root of the tree
 *
 * This function returns zero if @e is in the @root RB-tree and %-EINVAL if it
 * is not.
 */
static int self_check_in_wl_tree(const struct ubi_device *ubi,
				 struct ubi_wl_entry *e, struct rb_root *root)
{
	if (!ubi_dbg_chk_gen(ubi))
		return 0;

	if (in_wl_tree(e, root))
		return 0;

	ubi_err(ubi, "self-check failed for PEB %d, EC %d, RB-tree %p ",
		e->pnum, e->ec, root);
	dump_stack();
	return -EINVAL;
}

/**
 * self_check_in_pq - check if wear-leveling entry is in the protection
 *                        queue.
 * @ubi: UBI device description object
 * @e: the wear-leveling entry to check
 *
 * This function returns zero if @e is in @ubi->pq and %-EINVAL if it is not.
 */
static int self_check_in_pq(const struct ubi_device *ubi,
			    struct ubi_wl_entry *e)
{
	if (!ubi_dbg_chk_gen(ubi))
		return 0;

	if (in_pq(ubi, e))
		return 0;

	ubi_err(ubi, "self-check failed for PEB %d, EC %d, Protect queue",
		e->pnum, e->ec);
	dump_stack();
	return -EINVAL;
}
#ifndef CONFIG_MTD_UBI_FASTMAP
static struct ubi_wl_entry *get_peb_for_wl(struct ubi_device *ubi)
{
	struct ubi_wl_entry *e;

	e = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF, 0);
	self_check_in_wl_tree(ubi, e, &ubi->free);
	ubi->free_count--;
	ubi_assert(ubi->free_count >= 0);
	rb_erase(&e->u.rb, &ubi->free);

	return e;
}

/**
 * produce_free_peb - produce a free physical eraseblock.
 * @ubi: UBI device description object
 *
 * This function tries to make a free PEB by means of synchronous execution of
 * pending works. This may be needed if, for example the background thread is
 * disabled. Returns zero in case of success and a negative error code in case
 * of failure.
 */
static int produce_free_peb(struct ubi_device *ubi)
{
	int err;

	while (!ubi->free.rb_node && ubi->works_count) {
		spin_unlock(&ubi->wl_lock);

		dbg_wl("do one work synchronously");
		err = do_work(ubi, NULL);

		spin_lock(&ubi->wl_lock);
		if (err)
			return err;
	}

	return 0;
}

/**
 * ubi_wl_get_peb - get a physical eraseblock.
 * @ubi: UBI device description object
 *
 * This function returns a physical eraseblock in case of success and a
 * negative error code in case of failure.
 * Returns with ubi->fm_eba_sem held in read mode!
 */
int ubi_wl_get_peb(struct ubi_device *ubi)
{
	int err;
	struct ubi_wl_entry *e;

retry:
	down_read(&ubi->fm_eba_sem);
	spin_lock(&ubi->wl_lock);
	if (!ubi->free.rb_node) {
		if (ubi->works_count == 0) {
			ubi_err(ubi, "no free eraseblocks");
			ubi_assert(list_empty(&ubi->works));
			spin_unlock(&ubi->wl_lock);
			return -ENOSPC;
		}

		err = produce_free_peb(ubi);
		if (err < 0) {
			spin_unlock(&ubi->wl_lock);
			return err;
		}
		spin_unlock(&ubi->wl_lock);
		up_read(&ubi->fm_eba_sem);
		goto retry;

	}
	e = wl_get_wle(ubi);
	prot_queue_add(ubi, e);
	spin_unlock(&ubi->wl_lock);

	err = ubi_self_check_all_ff(ubi, e->pnum, ubi->vid_hdr_aloffset,
				    ubi->peb_size - ubi->vid_hdr_aloffset);
	if (err) {
		ubi_err(ubi, "new PEB %d does not contain all 0xFF bytes", e->pnum);
		return err;
	}

	return e->pnum;
}
#else
#include "fastmap-wl.c"
#endif