aboutsummaryrefslogtreecommitdiffstats
path: root/fs/ntfs/mft.c
blob: 326e7475a22a40d1323be1786ffa089ffb3182e7 (plain) (blame)
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
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
/**
 * mft.c - NTFS kernel mft record operations. Part of the Linux-NTFS project.
 *
 * Copyright (c) 2001-2011 Anton Altaparmakov and Tuxera Inc.
 * Copyright (c) 2002 Richard Russon
 *
 * This program/include file is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as published
 * by the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program/include file 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 (in the main directory of the Linux-NTFS
 * distribution in the file COPYING); if not, write to the Free Software
 * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/buffer_head.h>
#include <linux/slab.h>
#include <linux/swap.h>

#include "attrib.h"
#include "aops.h"
#include "bitmap.h"
#include "debug.h"
#include "dir.h"
#include "lcnalloc.h"
#include "malloc.h"
#include "mft.h"
#include "ntfs.h"

/**
 * map_mft_record_page - map the page in which a specific mft record resides
 * @ni:		ntfs inode whose mft record page to map
 *
 * This maps the page in which the mft record of the ntfs inode @ni is situated
 * and returns a pointer to the mft record within the mapped page.
 *
 * Return value needs to be checked with IS_ERR() and if that is true PTR_ERR()
 * contains the negative error code returned.
 */
static inline MFT_RECORD *map_mft_record_page(ntfs_inode *ni)
{
	loff_t i_size;
	ntfs_volume *vol = ni->vol;
	struct inode *mft_vi = vol->mft_ino;
	struct page *page;
	unsigned long index, end_index;
	unsigned ofs;

	BUG_ON(ni->page);
	/*
	 * The index into the page cache and the offset within the page cache
	 * page of the wanted mft record. FIXME: We need to check for
	 * overflowing the unsigned long, but I don't think we would ever get
	 * here if the volume was that big...
	 */
	index = (u64)ni->mft_no << vol->mft_record_size_bits >>
			PAGE_CACHE_SHIFT;
	ofs = (ni->mft_no << vol->mft_record_size_bits) & ~PAGE_CACHE_MASK;

	i_size = i_size_read(mft_vi);
	/* The maximum valid index into the page cache for $MFT's data. */
	end_index = i_size >> PAGE_CACHE_SHIFT;

	/* If the wanted index is out of bounds the mft record doesn't exist. */
	if (unlikely(index >= end_index)) {
		if (index > end_index || (i_size & ~PAGE_CACHE_MASK) < ofs +
				vol->mft_record_size) {
			page = ERR_PTR(-ENOENT);
			ntfs_error(vol->sb, "Attemt to read mft record 0x%lx, "
					"which is beyond the end of the mft.  "
					"This is probably a bug in the ntfs "
					"driver.", ni->mft_no);
			goto err_out;
		}
	}
	/* Read, map, and pin the page. */
	page = ntfs_map_page(mft_vi->i_mapping, index);
	if (likely(!IS_ERR(page))) {
		/* Catch multi sector transfer fixup errors. */
		if (likely(ntfs_is_mft_recordp((le32*)(page_address(page) +
				ofs)))) {
			ni->page = page;
			ni->page_ofs = ofs;
			return page_address(page) + ofs;
		}
		ntfs_error(vol->sb, "Mft record 0x%lx is corrupt.  "
				"Run chkdsk.", ni->mft_no);
		ntfs_unmap_page(page);
		page = ERR_PTR(-EIO);
		NVolSetErrors(vol);
	}
err_out:
	ni->page = NULL;
	ni->page_ofs = 0;
	return (void*)page;
}

/**
 * map_mft_record - map, pin and lock an mft record
 * @ni:		ntfs inode whose MFT record to map
 *
 * First, take the mrec_lock mutex.  We might now be sleeping, while waiting
 * for the mutex if it was already locked by someone else.
 *
 * The page of the record is mapped using map_mft_record_page() before being
 * returned to the caller.
 *
 * This in turn uses ntfs_map_page() to get the page containing the wanted mft
 * record (it in turn calls read_cache_page() which reads it in from disk if
 * necessary, increments the use count on the page so that it cannot disappear
 * under us and returns a reference to the page cache page).
 *
 * If read_cache_page() invokes ntfs_readpage() to load the page from disk, it
 * sets PG_locked and clears PG_uptodate on the page. Once I/O has completed
 * and the post-read mst fixups on each mft record in the page have been
 * performed, the page gets PG_uptodate set and PG_locked cleared (this is done
 * in our asynchronous I/O completion handler end_buffer_read_mft_async()).
 * ntfs_map_page() waits for PG_locked to become clear and checks if
 * PG_uptodate is set and returns an error code if not. This provides
 * sufficient protection against races when reading/using the page.
 *
 * However there is the write mapping to think about. Doing the above described
 * checking here will be fine, because when initiating the write we will set
 * PG_locked and clear PG_uptodate making sure nobody is touching the page
 * contents. Doing the locking this way means that the commit to disk code in
 * the page cache code paths is automatically sufficiently locked with us as
 * we will not touch a page that has been locked or is not uptodate. The only
 * locking problem then is them locking the page while we are accessing it.
 *
 * So that code will end up having to own the mrec_lock of all mft
 * records/inodes present in the page before I/O can proceed. In that case we
 * wouldn't need to bother with PG_locked and PG_uptodate as nobody will be
 * accessing anything without owning the mrec_lock mutex.  But we do need to
 * use them because of the read_cache_page() invocation and the code becomes so
 * much simpler this way that it is well worth it.
 *
 * The mft record is now ours and we return a pointer to it. You need to check
 * the returned pointer with IS_ERR() and if that is true, PTR_ERR() will return
 * the error code.
 *
 * NOTE: Caller is responsible for setting the mft record dirty before calling
 * unmap_mft_record(). This is obviously only necessary if the caller really
 * modified the mft record...
 * Q: Do we want to recycle one of the VFS inode state bits instead?
 * A: No, the inode ones mean we want to change the mft record, not we want to
 * write it out.
 */
MFT_RECORD *map_mft_record(ntfs_inode *ni)
{
	MFT_RECORD *m;

	ntfs_debug("Entering for mft_no 0x%lx.", ni->mft_no);

	/* Make sure the ntfs inode doesn't go away. */
	atomic_inc(&ni->count);

	/* Serialize access to this mft record. */
	mutex_lock(&ni->mrec_lock);

	m = map_mft_record_page(ni);
	if (likely(!IS_ERR(m)))
		return m;

	mutex_unlock(&ni->mrec_lock);
	atomic_dec(&ni->count);
	ntfs_error(ni->vol->sb, "Failed with error code %lu.", -PTR_ERR(m));
	return m;
}

/**
 * unmap_mft_record_page - unmap the page in which a specific mft record resides
 * @ni:		ntfs inode whose mft record page to unmap
 *
 * This unmaps the page in which the mft record of the ntfs inode @ni is
 * situated and returns. This is a NOOP if highmem is not configured.
 *
 * The unmap happens via ntfs_unmap_page() which in turn decrements the use
 * count on the page thus releasing it from the pinned state.
 *
 * We do not actually unmap the page from memory of course, as that will be
 * done by the page cache code itself when memory pressure increases or
 * whatever.
 */
static inline void unmap_mft_record_page(ntfs_inode *ni)
{
	BUG_ON(!ni->page);

	// TODO: If dirty, blah...
	ntfs_unmap_page(ni->page);
	ni->page = NULL;
	ni->page_ofs = 0;
	return;
}

/**
 * unmap_mft_record - release a mapped mft record
 * @ni:		ntfs inode whose MFT record to unmap
 *
 * We release the page mapping and the mrec_lock mutex which unmaps the mft
 * record and releases it for others to get hold of. We also release the ntfs
 * inode by decrementing the ntfs inode reference count.
 *
 * NOTE: If caller has modified the mft record, it is imperative to set the mft
 * record dirty BEFORE calling unmap_mft_record().
 */
void unmap_mft_record(ntfs_inode *ni)
{
	struct page *page = ni->page;

	BUG_ON(!page);

	ntfs_debug("Entering for mft_no 0x%lx.", ni->mft_no);

	unmap_mft_record_page(ni);
	mutex_unlock(&ni->mrec_lock);
	atomic_dec(&ni->count);
	/*
	 * If pure ntfs_inode, i.e. no vfs inode attached, we leave it to
	 * ntfs_clear_extent_inode() in the extent inode case, and to the
	 * caller in the non-extent, yet pure ntfs inode case, to do the actual
	 * tear down of all structures and freeing of all allocated memory.
	 */
	return;
}

/**
 * map_extent_mft_record - load an extent inode and attach it to its base
 * @base_ni:	base ntfs inode
 * @mref:	mft reference of the extent inode to load
 * @ntfs_ino:	on successful return, pointer to the ntfs_inode structure
 *
 * Load the extent mft record @mref and attach it to its base inode @base_ni.
 * Return the mapped extent mft record if IS_ERR(result) is false.  Otherwise
 * PTR_ERR(result) gives the negative error code.
 *
 * On successful return, @ntfs_ino contains a pointer to the ntfs_inode
 * structure of the mapped extent inode.
 */
MFT_RECORD *map_extent_mft_record(ntfs_inode *base_ni, MFT_REF mref,
		ntfs_inode **ntfs_ino)
{
	MFT_RECORD *m;
	ntfs_inode *ni = NULL;
	ntfs_inode **extent_nis = NULL;
	int i;
	unsigned long mft_no = MREF(mref);
	u16 seq_no = MSEQNO(mref);
	bool destroy_ni = false;

	ntfs_debug("Mapping extent mft record 0x%lx (base mft record 0x%lx).",
			mft_no, base_ni->mft_no);
	/* Make sure the base ntfs inode doesn't go away. */
	atomic_inc(&base_ni->count);
	/*
	 * Check if this extent inode has already been added to the base inode,
	 * in which case just return it. If not found, add it to the base
	 * inode before returning it.
	 */
	mutex_lock(&base_ni->extent_lock);
	if (base_ni->nr_extents > 0) {
		extent_nis = base_ni->ext.extent_ntfs_inos;
		for (i = 0; i < base_ni->nr_extents; i++) {
			if (mft_no != extent_nis[i]->mft_no)
				continue;
			ni = extent_nis[i];
			/* Make sure the ntfs inode doesn't go away. */
			atomic_inc(&ni->count);
			break;
		}
	}
	if (likely(ni != NULL)) {
		mutex_unlock(&base_ni->extent_lock);
		atomic_dec(&base_ni->count);
		/* We found the record; just have to map and return it. */
		m = map_mft_record(ni);
		/* map_mft_record() has incremented this on success. */
		atomic_dec(&ni->count);
		if (likely(!IS_ERR(m))) {
			/* Verify the sequence number. */
			if (likely(le16_to_cpu(m->sequence_number) == seq_no)) {
				ntfs_debug("Done 1.");
				*ntfs_ino = ni;
				return m;
			}
			unmap_mft_record(ni);
			ntfs_error(base_ni->vol->sb, "Found stale extent mft "
					"reference! Corrupt filesystem. "
					"Run chkdsk.");
			return ERR_PTR(-EIO);
		}
map_err_out:
		ntfs_error(base_ni->vol->sb, "Failed to map extent "
				"mft record, error code %ld.", -PTR_ERR(m));
		return m;
	}
	/* Record wasn't there. Get a new ntfs inode and initialize it. */
	ni = ntfs_new_extent_inode(base_ni->vol->sb, mft_no);
	if (unlikely(!ni)) {
		mutex_unlock(&base_ni->extent_lock);
		atomic_dec(&base_ni->count);
		return ERR_PTR(-ENOMEM);
	}
	ni->vol = base_ni->vol;
	ni->seq_no = seq_no;
	ni->nr_extents = -1;
	ni->ext.base_ntfs_ino = base_ni;
	/* Now map the record. */
	m = map_mft_record(ni);
	if (IS_ERR(m)) {
		mutex_unlock(&base_ni->extent_lock);
		atomic_dec(&base_ni->count);
		ntfs_clear_extent_inode(ni);
		goto map_err_out;
	}
	/* Verify the sequence number if it is present. */
	if (seq_no && (le16_to_cpu(m->sequence_number) != seq_no)) {
		ntfs_error(base_ni->vol->sb, "Found stale extent mft "
				"reference! Corrupt filesystem. Run chkdsk.");
		destroy_ni = true;
		m = ERR_PTR(-EIO);
		goto unm_err_out;
	}
	/* Attach extent inode to base inode, reallocating memory if needed. */
	if (!(base_ni->nr_extents & 3)) {
		ntfs_inode **tmp;
		int new_size = (base_ni->nr_extents + 4) * sizeof(ntfs_inode *);

		tmp = kmalloc(new_size, GFP_NOFS);
		if (unlikely(!tmp)) {
			ntfs_error(base_ni->vol->sb, "Failed to allocate "
					"internal buffer.");
			destroy_ni = true;
			m = ERR_PTR(-ENOMEM);
			goto unm_err_out;
		}
		if (base_ni->nr_extents) {
			BUG_ON(!base_ni->ext.extent_ntfs_inos);
			memcpy(tmp, base_ni->ext.extent_ntfs_inos, new_size -
					4 * sizeof(ntfs_inode *));
			kfree(base_ni->ext.extent_ntfs_inos);
		}
		base_ni->ext.extent_ntfs_inos = tmp;
	}
	base_ni->ext.extent_ntfs_inos[base_ni->nr_extents++] = ni;
	mutex_unlock(&base_ni->extent_lock);
	atomic_dec(&base_ni->count);
	ntfs_debug("Done 2.");
	*ntfs_ino = ni;
	return m;
unm_err_out:
	unmap_mft_record(ni);
	mutex_unlock(&base_ni->extent_lock);
	atomic_dec(&base_ni->count);
	/*
	 * If the extent inode was not attached to the base inode we need to
	 * release it or we will leak memory.
	 */
	if (destroy_ni)
		ntfs_clear_extent_inode(ni);
	return m;
}

#ifdef NTFS_RW

/**
 * __mark_mft_record_dirty - set the mft record and the page containing it dirty
 * @ni:		ntfs inode describing the mapped mft record
 *
 * Internal function.  Users should call mark_mft_record_dirty() instead.
 *
 * Set the mapped (extent) mft record of the (base or extent) ntfs inode @ni,
 * as well as the page containing the mft record, dirty.  Also, mark the base
 * vfs inode dirty.  This ensures that any changes to the mft record are
 * written out to disk.
 *
 * NOTE:  We only set I_DIRTY_SYNC and I_DIRTY_DATASYNC (and not I_DIRTY_PAGES)
 * on the base vfs inode, because even though file data may have been modified,
 * it is dirty in the inode meta data rather than the data page cache of the
 * inode, and thus there are no data pages that need writing out.  Therefore, a
 * full mark_inode_dirty() is overkill.  A mark_inode_dirty_sync(), on the
 * other hand, is not sufficient, because ->write_inode needs to be called even
 * in case of fdatasync. This needs to happen or the file data would not
 * necessarily hit the device synchronously, even though the vfs inode has the
 * O_SYNC flag set.  Also, I_DIRTY_DATASYNC simply "feels" better than just
 * I_DIRTY_SYNC, since the file data has not actually hit the block device yet,
 * which is not what I_DIRTY_SYNC on its own would suggest.
 */
void __mark_mft_record_dirty(ntfs_inode *ni)
{
	ntfs_inode *base_ni;

	ntfs_debug("Entering for inode 0x%lx.", ni->mft_no);
	BUG_ON(NInoAttr(ni));
	mark_ntfs_record_dirty(ni->page, ni->page_ofs);
	/* Determine the base vfs inode and mark it dirty, too. */
	mutex_lock(&ni->extent_lock);
	if (likely(ni->nr_extents >= 0))
		base_ni = ni;
	else
		base_ni = ni->ext.base_ntfs_ino;
	mutex_unlock(&ni->extent_lock);
	__mark_inode_dirty(VFS_I(base_ni), I_DIRTY_SYNC | I_DIRTY_DATASYNC);
}

static const char *ntfs_please_email = "Please email "
		"linux-ntfs-dev@lists.sourceforge.net and say that you saw "
		"this message.  Thank you.";

/**
 * ntfs_sync_mft_mirror_umount - synchronise an mft record to the mft mirror
 * @vol:	ntfs volume on which the mft record to synchronize resides
 * @mft_no:	mft record number of mft record to synchronize
 * @m:		mapped, mst protected (extent) mft record to synchronize
 *
 * Write the mapped, mst protected (extent) mft record @m with mft record
 * number @mft_no to the mft mirror ($MFTMirr) of the ntfs volume @vol,
 * bypassing the page cache and the $MFTMirr inode itself.
 *
 * This function is only for use at umount time when the mft mirror inode has
 * already been disposed off.  We BUG() if we are called while the mft mirror
 * inode is still attached to the volume.
 *
 * On success return 0.  On error return -errno.
 *
 * NOTE:  This function is not implemented yet as I am not convinced it can
 * actually be triggered considering the sequence of commits we do in super.c::
 * ntfs_put_super().  But just in case we provide this place holder as the
 * alternative would be either to BUG() or to get a NULL pointer dereference
 * and Oops.
 */
static int ntfs_sync_mft_mirror_umount(ntfs_volume *vol,
		const unsigned long mft_no, MFT_RECORD *m)
{
	BUG_ON(vol->mftmirr_ino);
	ntfs_error(vol->sb, "Umount time mft mirror syncing is not "
			"implemented yet.  %s", ntfs_please_email);
	return -EOPNOTSUPP;
}

/**
 * ntfs_sync_mft_mirror - synchronize an mft record to the mft mirror
 * @vol:	ntfs volume on which the mft record to synchronize resides
 * @mft_no:	mft record number of mft record to synchronize
 * @m:		mapped, mst protected (extent) mft record to synchronize
 * @sync:	if true, wait for i/o completion
 *
 * Write the mapped, mst protected (extent) mft record @m with mft record
 * number @mft_no to the mft mirror ($MFTMirr) of the ntfs volume @vol.
 *
 * On success return 0.  On error return -errno and set the volume errors flag
 * in the ntfs volume @vol.
 *
 * NOTE:  We always perform synchronous i/o and ignore the @sync parameter.
 *
 * TODO:  If @sync is false, want to do truly asynchronous i/o, i.e. just
 * schedule i/o via ->writepage or do it via kntfsd or whatever.
 */
int ntfs_sync_mft_mirror(ntfs_volume *vol, const unsigned long mft_no,
		MFT_RECORD *m, int sync)
{
	struct page *page;
	unsigned int blocksize = vol->sb->s_blocksize;
	int max_bhs = vol->mft_record_size / blocksize;
	struct buffer_head *bhs[max_bhs];
	struct buffer_head *bh, *head;
	u8 *kmirr;
	runlist_element *rl;
	unsigned int block_start, block_end, m_start, m_end, page_ofs;
	int i_bhs, nr_bhs, err = 0;
	unsigned char blocksize_bits = vol->sb->s_blocksize_bits;

	ntfs_debug("Entering for inode 0x%lx.", mft_no);
	BUG_ON(!max_bhs);
	if (unlikely(!vol->mftmirr_ino)) {
		/* This could happen during umount... */
		err = ntfs_sync_mft_mirror_umount(vol, mft_no, m);
		if (likely(!err))
			return err;
		goto err_out;
	}
	/* Get the page containing the mirror copy of the mft record @m. */
	page = ntfs_map_page(vol->mftmirr_ino->i_mapping, mft_no >>
			(PAGE_CACHE_SHIFT - vol->mft_record_size_bits));
	if (IS_ERR(page)) {
		ntfs_error(vol->sb, "Failed to map mft mirror page.");
		err = PTR_ERR(page);
		goto err_out;
	}
	lock_page(page);
	BUG_ON(!PageUptodate(page));
	ClearPageUptodate(page);
	/* Offset of the mft mirror record inside the page. */
	page_ofs = (mft_no << vol->mft_record_size_bits) & ~PAGE_CACHE_MASK;
	/* The address in the page of the mirror copy of the mft record @m. */
	kmirr = page_address(page) + page_ofs;
	/* Copy the mst protected mft record to the mirror. */
	memcpy(kmirr, m, vol->mft_record_size);
	/* Create uptodate buffers if not present. */
	if (unlikely(!page_has_buffers(page))) {
		struct buffer_head *tail;

		bh = head = alloc_page_buffers(page, blocksize, 1);
		do {
			set_buffer_uptodate(bh);
			tail = bh;
			bh = bh->b_this_page;
		} while (bh);
		tail->b_this_page = head;
		attach_page_buffers(page, head);
	}
	bh = head = page_buffers(page);
	BUG_ON(!bh);
	rl = NULL;
	nr_bhs = 0;
	block_start = 0;
	m_start = kmirr - (u8*)page_address(page);
	m_end = m_start + vol->mft_record_size;
	do {
		block_end = block_start + blocksize;
		/* If the buffer is outside the mft record, skip it. */
		if (block_end <= m_start)
			continue;
		if (unlikely(block_start >= m_end))
			break;
		/* Need to map the buffer if it is not mapped already. */
		if (unlikely(!buffer_mapped(bh))) {
			VCN vcn;
			LCN lcn;
			unsigned int vcn_ofs;

			bh->b_bdev = vol->sb->s_bdev;
			/* Obtain the vcn and offset of the current block. */
			vcn = ((VCN)mft_no << vol->mft_record_size_bits) +
					(block_start - m_start);
			vcn_ofs = vcn & vol->cluster_size_mask;
			vcn >>= vol->cluster_size_bits;
			if (!rl) {
				down_read(&NTFS_I(vol->mftmirr_ino)->
						runlist.lock);
				rl = NTFS_I(vol->mftmirr_ino)->runlist.rl;
				/*
				 * $MFTMirr always has the whole of its runlist
				 * in memory.
				 */
				BUG_ON(!rl);
			}
			/* Seek to element containing target vcn. */
			while (rl->length && rl[1].vcn <= vcn)
				rl++;
			lcn = ntfs_rl_vcn_to_lcn(rl, vcn);
			/* For $MFTMirr, only lcn >= 0 is a successful remap. */
			if (likely(lcn >= 0)) {
				/* Setup buffer head to correct block. */
				bh->b_blocknr = ((lcn <<
						vol->cluster_size_bits) +
						vcn_ofs) >> blocksize_bits;
				set_buffer_mapped(bh);
			} else {
				bh->b_blocknr = -1;
				ntfs_error(vol->sb, "Cannot write mft mirror "
						"record 0x%lx because its "
						"location on disk could not "
						"be determined (error code "
						"%lli).", mft_no,
						(long long)lcn);
				err = -EIO;
			}
		}
		BUG_ON(!buffer_uptodate(bh));
		BUG_ON(!nr_bhs && (m_start != block_start));
		BUG_ON(nr_bhs >= max_bhs);
		bhs[nr_bhs++] = bh;
		BUG_ON((nr_bhs >= max_bhs) && (m_end != block_end));
	} while (block_start = block_end, (bh = bh->b_this_page) != head);
	if (unlikely(rl))
		up_read(&NTFS_I(vol->mftmirr_ino)->runlist.lock);
	if (likely(!err)) {
		/* Lock buffers and start synchronous write i/o on them. */
		for (i_bhs = 0; i_bhs < nr_bhs; i_bhs++) {
			struct buffer_head *tbh = bhs[i_bhs];

			if (!trylock_buffer(tbh))
				BUG();
			BUG_ON(!buffer_uptodate(tbh));
			clear_buffer_dirty(tbh);
			get_bh(tbh);
			tbh->b_end_io = end_buffer_write_sync;
			submit_bh(WRITE, tbh);
		}
		/* Wait on i/o completion of buffers. */
		for (i_bhs = 0; i_bhs < nr_bhs; i_bhs++) {
			struct buffer_head *tbh = bhs[i_bhs];

			wait_on_buffer(tbh);
			if (unlikely(!buffer_uptodate(tbh))) {
				err = -EIO;
				/*
				 * Set the buffer uptodate so the page and
				 * buffer states do not become out of sync.
				 */
				set_buffer_uptodate(tbh);
			}
		}
	} else /* if (unlikely(err)) */ {
		/* Clean the buffers. */
		for (i_bhs = 0; i_bhs < nr_bhs; i_bhs++)
			clear_buffer_dirty(bhs[i_bhs]);
	}
	/* Current state: all buffers are clean, unlocked, and uptodate. */
	/* Remove the mst protection fixups again. */
	post_write_mst_fixup((NTFS_RECORD*)kmirr);
	flush_dcache_page(page);
	SetPageUptodate(page);
	unlock_page(page);
	ntfs_unmap_page(page);
	if (likely(!err)) {
		ntfs_debug("Done.");
	} else {
		ntfs_error(vol->sb, "I/O error while writing mft mirror "
				"record 0x%lx!", mft_no);
err_out:
		ntfs_error(vol->sb, "Failed to synchronize $MFTMirr (error "
				"code %i).  Volume will be left marked dirty "
				"on umount.  Run ntfsfix on the partition "
				"after umounting to correct this.", -err);
		NVolSetErrors(vol);
	}
	return err;
}

/**
 * write_mft_record_nolock - write out a mapped (extent) mft record
 * @ni:		ntfs inode describing the mapped (extent) mft record
 * @m:		mapped (extent) mft record to write
 * @sync:	if true, wait for i/o completion
 *
 * Write the mapped (extent) mft record @m described by the (regular or extent)
 * ntfs inode @ni to backing store.  If the mft record @m has a counterpart in
 * the mft mirror, that is also updated.
 *
 * We only write the mft record if the ntfs inode @ni is dirty and the first
 * buffer belonging to its mft record is dirty, too.  We ignore the dirty state
 * of subsequent buffers because we could have raced with
 * fs/ntfs/aops.c::mark_ntfs_record_dirty().
 *
 * On success, clean the mft record and return 0.  On error, leave the mft
 * record dirty and return -errno.
 *
 * NOTE:  We always perform synchronous i/o and ignore the @sync parameter.
 * However, if the mft record has a counterpart in the mft mirror and @sync is
 * true, we write the mft record, wait for i/o completion, and only then write
 * the mft mirror copy.  This ensures that if the system crashes either the mft
 * or the mft mirror will contain a self-consistent mft record @m.  If @sync is
 * false on the other hand, we start i/o on both and then wait for completion
 * on them.  This provides a speedup but no longer guarantees that you will end
 * up with a self-consistent mft record in the case of a crash but if you asked
 * for asynchronous writing you probably do not care about that anyway.
 *
 * TODO:  If @sync is false, want to do truly asynchronous i/o, i.e. just
 * schedule i/o via ->writepage or do it via kntfsd or whatever.
 */
int write_mft_record_nolock(ntfs_inode *ni, MFT_RECORD *m, int sync)
{
	ntfs_volume *vol = ni->vol;
	struct page *page = ni->page;
	unsigned int blocksize = vol->sb->s_blocksize;
	unsigned char blocksize_bits = vol->sb->s_blocksize_bits;
	int max_bhs = vol->mft_record_size / blocksize;
	struct buffer_head *bhs[max_bhs];
	struct buffer_head *bh, *head;
	runlist_element *rl;
	unsigned int block_start, block_end, m_start, m_end;
	int i_bhs, nr_bhs, err = 0;

	ntfs_debug("Entering for inode 0x%lx.", ni->mft_no);
	BUG_ON(NInoAttr(ni));
	BUG_ON(!max_bhs);
	BUG_ON(!PageLocked(page));
	/*
	 * If the ntfs_inode is clean no need to do anything.  If it is dirty,
	 * mark it as clean now so that it can be redirtied later on if needed.
	 * There is no danger of races since the caller is holding the locks
	 * for the mft record @m and the page it is in.
	 */
	if (!NInoTestClearDirty(ni))
		goto done;
	bh = head = page_buffers(page);
	BUG_ON(!bh);
	rl = NULL;
	nr_bhs = 0;
	block_start = 0;
	m_start = ni->page_ofs;
	m_end = m_start + vol->mft_record_size;
	do {
		block_end = block_start + blocksize;
		/* If the buffer is outside the mft record, skip it. */
		if (block_end <= m_start)
			continue;
		if (unlikely(block_start >= m_end))
			break;
		/*
		 * If this block is not the first one in the record, we ignore
		 * the buffer's dirty state because we could have raced with a
		 * parallel mark_ntfs_record_dirty().
		 */
		if (block_start == m_start) {
			/* This block is the first one in the record. */
			if (!buffer_dirty(bh)) {
				BUG_ON(nr_bhs);
				/* Clean records are not written out. */
				break;
			}
		}
		/* Need to map the buffer if it is not mapped already. */
		if (unlikely(!buffer_mapped(bh))) {
			VCN vcn;
			LCN lcn;
			unsigned int vcn_ofs;

			bh->b_bdev = vol->sb->s_bdev;
			/* Obtain the vcn and offset of the current block. */
			vcn = ((VCN)ni->mft_no << vol->mft_record_size_bits) +
					(block_start - m_start);
			vcn_ofs = vcn & vol->cluster_size_mask;
			vcn >>= vol->cluster_size_bits;
			if (!rl) {
				down_read(&NTFS_I(vol->mft_ino)->runlist.lock);
				rl = NTFS_I(vol->mft_ino)->runlist.rl;
				BUG_ON(!rl);
			}
			/* Seek to element containing target vcn. */
			while (rl->length && rl[1].vcn <= vcn)
				rl++;
			lcn = ntfs_rl_vcn_to_lcn(rl, vcn);
			/* For $MFT, only lcn >= 0 is a successful remap. */
			if (likely(lcn >= 0)) {
				/* Setup buffer head to correct block. */
				bh->b_blocknr = ((lcn <<
						vol->cluster_size_bits) +
						vcn_ofs) >> blocksize_bits;
				set_buffer_mapped(bh);
			} else {
				bh->b_blocknr = -1;
				ntfs_error(vol->sb, "Cannot write mft record "
						"0x%lx because its location "
						"on disk could not be "
						"determined (error code %lli).",
						ni->mft_no, (long long)lcn);
				err = -EIO;
			}
		}
		BUG_ON(!buffer_uptodate(bh));
		BUG_ON(!nr_bhs && (m_start != block_start));
		BUG_ON(nr_bhs >= max_bhs);
		bhs[nr_bhs++] = bh;
		BUG_ON((nr_bhs >= max_bhs) && (m_end != block_end));
	} while (block_start = block_end, (bh = bh->b_this_page) != head);
	if (unlikely(rl))
		up_read(&NTFS_I(vol->mft_ino)->runlist.lock);
	if (!nr_bhs)
		goto done;
	if (unlikely(err))
		goto cleanup_out;
	/* Apply the mst protection fixups. */
	err = pre_write_mst_fixup((NTFS_RECORD*)m, vol->mft_record_size);
	if (err) {
		ntfs_error(vol->sb, "Failed to apply mst fixups!");
		goto cleanup_out;
	}
	flush_dcache_mft_record_page(ni);
	/* Lock buffers and start synchronous write i/o on them. */
	for (i_bhs = 0; i_bhs < nr_bhs; i_bhs++) {
		struct buffer_head *tbh = bhs[i_bhs];

		if (!trylock_buffer(tbh))
			BUG();
		BUG_ON(!buffer_uptodate(tbh));
		clear_buffer_dirty(tbh);
		get_bh(tbh);
		tbh->b_end_io = end_buffer_write_sync;
		submit_bh(WRITE, tbh);
	}
	/* Synchronize the mft mirror now if not @sync. */
	if (!sync && ni->mft_no < vol->mftmirr_size)
		ntfs_sync_mft_mirror(vol, ni->mft_no, m, sync);
	/* Wait on i/o completion of buffers. */
	for (i_bhs = 0; i_bhs < nr_bhs; i_bhs++) {
		struct buffer_head *tbh = bhs[i_bhs];

		wait_on_buffer(tbh);
		if (unlikely(!buffer_uptodate(tbh))) {
			err = -EIO;
			/*
			 * Set the buffer uptodate so the page and buffer
			 * states do not become out of sync.
			 */
			if (PageUptodate(page))
				set_buffer_uptodate(tbh);
		}
	}
	/* If @sync, now synchronize the mft mirror. */
	if (sync && ni->mft_no < vol->mftmirr_size)
		ntfs_sync_mft_mirror(vol, ni->mft_no, m, sync);
	/* Remove the mst protection fixups again. */
	post_write_mst_fixup((NTFS_RECORD*)m);
	flush_dcache_mft_record_page(ni);
	if (unlikely(err)) {
		/* I/O error during writing.  This is really bad! */
		ntfs_error(vol->sb, "I/O error while writing mft record "
				"0x%lx!  Marking base inode as bad.  You "
				"should unmount the volume and run chkdsk.",
				ni->mft_no);
		goto err_out;
	}
done:
	ntfs_debug("Done.");
	return 0;
cleanup_out:
	/* Clean the buffers. */
	for (i_bhs = 0; i_bhs < nr_bhs; i_bhs++)
		clear_buffer_dirty(bhs[i_bhs]);
err_out:
	/*
	 * Current state: all buffers are clean, unlocked, and uptodate.
	 * The caller should mark the base inode as bad so that no more i/o
	 * happens.  ->clear_inode() will still be invoked so all extent inodes
	 * and other allocated memory will be freed.
	 */
	if (err == -ENOMEM) {
		ntfs_error(vol->sb, "Not enough memory to write mft record.  "
				"Redirtying so the write is retried later.");
		mark_mft_record_dirty(ni);
		err = 0;
	} else
		NVolSetErrors(vol);
	return err;
}

/**
 * ntfs_may_write_mft_record - check if an mft record may be written out
 * @vol:	[IN]  ntfs volume on which the mft record to check resides
 * @mft_no:	[IN]  mft record number of the mft record to check
 * @m:		[IN]  mapped mft record to check
 * @locked_ni:	[OUT] caller has to unlock this ntfs inode if one is returned
 *
 * Check if the mapped (base or extent) mft record @m with mft record number
 * @mft_no belonging to the ntfs volume @vol may be written out.  If necessary
 * and possible the ntfs inode of the mft record is locked and the base vfs
 * inode is pinned.  The locked ntfs inode is then returned in @locked_ni.  The
 * caller is responsible for unlocking the ntfs inode and unpinning the base
 * vfs inode.
 *
 * Return 'true' if the mft record may be written out and 'false' if not.
 *
 * The caller has locked the page and cleared the uptodate flag on it which
 * means that we can safely write out any dirty mft records that do not have
 * their inodes in icache as determined by ilookup5() as anyone
 * opening/creating such an inode would block when attempting to map the mft
 * record in read_cache_page() until we are finished with the write out.
 *
 * Here is a description of the tests we perform:
 *
 * If the inode is found in icache we know the mft record must be a base mft
 * record.  If it is dirty, we do not write it and return 'false' as the vfs
 * inode write paths will result in the access times being updated which would
 * cause the base mft record to be redirtied and written out again.  (We know
 * the access time update will modify the base mft record because Windows
 * chkdsk complains if the standard information attribute is not in the base
 * mft record.)
 *
 * If the inode is in icache and not dirty, we attempt to lock the mft record
 * and if we find the lock was already taken, it is not safe to write the mft
 * record and we return 'false'.
 *
 * If we manage to obtain the lock we have exclusive access to the mft record,
 * which also allows us safe writeout of the mft record.  We then set
 * @locked_ni to the locked ntfs inode and return 'true'.
 *
 * Note we cannot just lock the mft record and sleep while waiting for the lock
 * because this would deadlock due to lock reversal (normally the mft record is
 * locked before the page is locked but we already have the page locked here
 * when we try to lock the mft record).
 *
 * If the inode is not in icache we need to perform further checks.
 *
 * If the mft record is not a FILE record or it is a base mft record, we can
 * safely write it and return 'true'.
 *
 * We now know the mft record is an extent mft record.  We check if the inode
 * corresponding to its base mft record is in icache and obtain a reference to
 * it if it is.  If it is not, we can safely write it and return 'true'.
 *
 * We now have the base inode for the extent mft record.  We check if it has an
 * ntfs inode for the extent mft record attached and if not it is safe to write
 * the extent mft record and we return 'true'.
 *
 * The ntfs inode for the extent mft record is attached to the base inode so we
 * attempt to lock the extent mft record and if we find the lock was already
 * taken, it is not safe to write the extent mft record and we return 'false'.
 *
 * If we manage to obtain the lock we have exclusive access to the extent mft
 * record, which also allows us safe writeout of the extent mft record.  We
 * set the ntfs inode of the extent mft record clean and then set @locked_ni to
 * the now locked ntfs inode and return 'true'.
 *
 * Note, the reason for actually writing dirty mft records here and not just
 * relying on the vfs inode dirty code paths is that we can have mft records
 * modified without them ever having actual inodes in memory.  Also we can have
 * dirty mft records with clean ntfs inodes in memory.  None of the described
 * cases would result in the dirty mft records being written out if we only
 * relied on the vfs inode dirty code paths.  And these cases can really occur
 * during allocation of new mft records and in particular when the
 * initialized_size of the $MFT/$DATA attribute is extended and the new space
 * is initialized using ntfs_mft_record_format().  The clean inode can then
 * appear if the mft record is reused for a new inode before it got written
 * out.
 */
bool ntfs_may_write_mft_record(ntfs_volume *vol, const unsigned long mft_no,
		const MFT_RECORD *m, ntfs_inode **locked_ni)
{
	struct super_block *sb = vol->sb;
	struct inode *mft_vi = vol->mft_ino;
	struct inode *vi;
	ntfs_inode *ni, *eni, **extent_nis;
	int i;
	ntfs_attr na;

	ntfs_debug("Entering for inode 0x%lx.", mft_no);
	/*
	 * Normally we do not return a locked inode so set @locked_ni to NULL.
	 */
	BUG_ON(!locked_ni);
	*locked_ni = NULL;
	/*
	 * Check if the inode corresponding to this mft record is in the VFS
	 * inode cache and obtain a reference to it if it is.
	 */
	ntfs_debug("Looking for inode 0x%lx in icache.", mft_no);
	na.mft_no = mft_no;
	na.name = NULL;
	na.name_len = 0;
	na.type = AT_UNUSED;
	/*
	 * Optimize inode 0, i.e. $MFT itself, since we have it in memory and
	 * we get here for it rather often.
	 */
	if (!mft_no) {
		/* Balance the below iput(). */
		vi = igrab(mft_vi);
		BUG_ON(vi != mft_vi);
	} else {
		/*
		 * Have to use ilookup5_nowait() since ilookup5() waits for the
		 * inode lock which causes ntfs to deadlock when a concurrent
		 * inode write via the inode dirty code paths and the page
		 * dirty code path of the inode dirty code path when writing
		 * $MFT occurs.
		 */
		vi = ilookup5_nowait(sb, mft_no, (test_t)ntfs_test_inode, &na);
	}
	if (vi) {
		ntfs_debug("Base inode 0x%lx is in icache.", mft_no);
		/* The inode is in icache. */
		ni = NTFS_I(vi);
		/* Take a reference to the ntfs inode. */
		atomic_inc(&ni->count);
		/* If the inode is dirty, do not write this record. */
		if (NInoDirty(ni)) {
			ntfs_debug("Inode 0x%lx is dirty, do not write it.",
					mft_no);
			atomic_dec(&ni->count);
			iput(vi);
			return false;
		}
		ntfs_debug("Inode 0x%lx is not dirty.", mft_no);
		/* The inode is not dirty, try to take the mft record lock. */
		if (unlikely(!mutex_trylock(&ni->mrec_lock))) {
			ntfs_debug("Mft record 0x%lx is already locked, do "
					"not write it.", mft_no);
			atomic_dec(&ni->count);
			iput(vi);
			return false;
		}
		ntfs_debug("Managed to lock mft record 0x%lx, write it.",
				mft_no);
		/*
		 * The write has to occur while we hold the mft record lock so
		 * return the locked ntfs inode.
		 */
		*locked_ni = ni;
		return true;
	}
	ntfs_debug("Inode 0x%lx is not in icache.", mft_no);
	/* The inode is not in icache. */
	/* Write the record if it is not a mft record (type "FILE"). */
	if (!ntfs_is_mft_record(m->magic)) {
		ntfs_debug("Mft record 0x%lx is not a FILE record, write it.",
				mft_no);
		return true;
	}
	/* Write the mft record if it is a base inode. */
	if (!m->base_mft_record) {
		ntfs_debug("Mft record 0x%lx is a base record, write it.",
				mft_no);
		return true;
	}
	/*
	 * This is an extent mft record.  Check if the inode corresponding to
	 * its base mft record is in icache and obtain a reference to it if it
	 * is.
	 */
	na.mft_no = MREF_LE(m->base_mft_record);
	ntfs_debug("Mft record 0x%lx is an extent record.  Looking for base "
			"inode 0x%lx in icache.", mft_no, na.mft_no);
	if (!na.mft_no) {
		/* Balance the below iput(). */
		vi = igrab(mft_vi);
		BUG_ON(vi != mft_vi);
	} else
		vi = ilookup5_nowait(sb, na.mft_no, (test_t)ntfs_test_inode,
				&na);
	if (!vi) {
		/*
		 * The base inode is not in icache, write this extent mft
		 * record.
		 */
		ntfs_debug("Base inode 0x%lx is not in icache, write the "
				"extent record.", na.mft_no);
		return true;
	}
	ntfs_debug("Base inode 0x%lx is in icache.", na.mft_no);
	/*
	 * The base inode is in icache.  Check if it has the extent inode
	 * corresponding to this extent mft record attached.
	 */
	ni = NTFS_I(vi);
	mutex_lock(&ni->extent_lock);
	if (ni->nr_extents <= 0) {
		/*
		 * The base inode has no attached extent inodes, write this
		 * extent mft record.
		 */
		mutex_unlock(&ni->extent_lock);
		iput(vi);
		ntfs_debug("Base inode 0x%lx has no attached extent inodes, "
				"write the extent record.", na.mft_no);
		return true;
	}
	/* Iterate over the attached extent inodes. */
	extent_nis = ni->ext.extent_ntfs_inos;
	for (eni = NULL, i = 0; i < ni->nr_extents; ++i) {
		if (mft_no == extent_nis[i]->mft_no) {
			/*
			 * Found the extent inode corresponding to this extent
			 * mft record.
			 */
			eni = extent_nis[i];
			break;
		}
	}
	/*
	 * If the extent inode was not attached to the base inode, write this
	 * extent mft record.
	 */
	if (!eni) {
		mutex_unlock(&ni->extent_lock);
		iput(vi);
		ntfs_debug("Extent inode 0x%lx is not attached to its base "
				"inode 0x%lx, write the extent record.",
				mft_no, na.mft_no);
		return true;
	}
	ntfs_debug("Extent inode 0x%lx is attached to its base inode 0x%lx.",
			mft_no, na.mft_no);
	/* Take a reference to the extent ntfs inode. */
	atomic_inc(&eni->count);
	mutex_unlock(&ni->extent_lock);
	/*
	 * Found the extent inode coresponding to this extent mft record.
	 * Try to take the mft record lock.
	 */
	if (unlikely(!mutex_trylock(&eni->mrec_lock))) {
		atomic_dec(&eni->count);
		iput(vi);
		ntfs_debug("Extent mft record 0x%lx is already locked, do "
				"not write it.", mft_no);
		return false;
	}
	ntfs_debug("Managed to lock extent mft record 0x%lx, write it.",
			mft_no);
	if (NInoTestClearDirty(eni))
		ntfs_debug("Extent inode 0x%lx is dirty, marking it clean.",
				mft_no);
	/*
	 * The write has to occur while we hold the mft record lock so return
	 * the locked extent ntfs inode.
	 */
	*locked_ni = eni;
	return true;
}

static const char *es = "  Leaving inconsistent metadata.  Unmount and run "
		"chkdsk.";

/**
 * ntfs_mft_bitmap_find_and_alloc_free_rec_nolock - see name
 * @vol:	volume on which to search for a free mft record
 * @base_ni:	open base inode if allocating an extent mft record or NULL
 *
 * Search for a free mft record in the mft bitmap attribute on the ntfs volume
 * @vol.
 *
 * If @base_ni is NULL start the search at the default allocator position.
 *
 * If @base_ni is not NULL start the search at the mft record after the base
 * mft record @base_ni.
 *
 * Return the free mft record on success and -errno on error.  An error code of
 * -ENOSPC means that there are no free mft records in the currently
 * initialized mft bitmap.
 *
 * Locking: Caller must hold vol->mftbmp_lock for writing.
 */
static int ntfs_mft_bitmap_find_and_alloc_free_rec_nolock(ntfs_volume *vol,
		ntfs_inode *base_ni)
{
	s64 pass_end, ll, data_pos, pass_start, ofs, bit;
	unsigned long flags;
	struct address_space *mftbmp_mapping;
	u8 *buf, *byte;
	struct page *page;
	unsigned int page_ofs, size;
	u8 pass, b;

	ntfs_debug("Searching for free mft record in the currently "
			"initialized mft bitmap.");
	mftbmp_mapping = vol->mftbmp_ino->i_mapping;
	/*
	 * Set the end of the pass making sure we do not overflow the mft
	 * bitmap.
	 */
	read_lock_irqsave(&NTFS_I(vol->mft_ino)->size_lock, flags);
	pass_end = NTFS_I(vol->mft_ino)->allocated_size >>
			vol->mft_record_size_bits;
	read_unlock_irqrestore(&NTFS_I(vol->mft_ino)->size_lock, flags);
	read_lock_irqsave(&NTFS_I(vol->mftbmp_ino)->size_lock, flags);
	ll = NTFS_I(vol->mftbmp_ino)->initialized_size << 3;
	read_unlock_irqrestore(&NTFS_I(vol->mftbmp_ino)->size_lock, flags);
	if (pass_end > ll)
		pass_end = ll;
	pass = 1;
	if (!base_ni)
		data_pos = vol->mft_data_pos;
	else
		data_pos = base_ni->mft_no + 1;
	if (data_pos < 24)
		data_pos = 24;
	if (data_pos >= pass_end) {
		data_pos = 24;
		pass = 2;
		/* This happens on a freshly formatted volume. */
		if (data_pos >= pass_end)
			return -ENOSPC;
	}
	pass_start = data_pos;
	ntfs_debug("Starting bitmap search: pass %u, pass_start 0x%llx, "
			"pass_end 0x%llx, data_pos 0x%llx.", pass,
			(long long)pass_start, (long long)pass_end,
			(long long)data_pos);
	/* Loop until a free mft record is found. */
	for (; pass <= 2;) {
		/* Cap size to pass_end. */
		ofs = data_pos >> 3;
		page_ofs = ofs & ~PAGE_CACHE_MASK;
		size = PAGE_CACHE_SIZE - page_ofs;
		ll = ((pass_end + 7) >> 3) - ofs;
		if (size > ll)
			size = ll;
		size <<= 3;
		/*
		 * If we are still within the active pass, search the next page
		 * for a zero bit.
		 */
		if (size) {
			page = ntfs_map_page(mftbmp_mapping,
					ofs >> PAGE_CACHE_SHIFT);
			if (IS_ERR(page)) {
				ntfs_error(vol->sb, "Failed to read mft "
						"bitmap, aborting.");
				return PTR_ERR(page);
			}
			buf = (u8*)page_address(page) + page_ofs;
			bit = data_pos & 7;
			data_pos &= ~7ull;
			ntfs_debug("Before inner for loop: size 0x%x, "
					"data_pos 0x%llx, bit 0x%llx", size,
					(long long)data_pos, (long long)bit);
			for (; bit < size && data_pos + bit < pass_end;
					bit &= ~7ull, bit += 8) {
				byte = buf + (bit >> 3);
				if (*byte == 0xff)
					continue;
				b = ffz((unsigned long)*byte);
				if (b < 8 && b >= (bit & 7)) {
					ll = data_pos + (bit & ~7ull) + b;
					if (unlikely(ll > (1ll << 32))) {
						ntfs_unmap_page(page);
						return -ENOSPC;
					}
					*byte |= 1 << b;
					flush_dcache_page(page);
					set_page_dirty(page);
					ntfs_unmap_page(page);
					ntfs_debug("Done.  (Found and "
							"allocated mft record "
							"0x%llx.)",
							(long long)ll);
					return ll;
				}
			}
			ntfs_debug("After inner for loop: size 0x%x, "
					"data_pos 0x%llx, bit 0x%llx", size,
					(long long)data_pos, (long long)bit);
			data_pos += size;
			ntfs_unmap_page(page);
			/*
			 * If the end of the pass has not been reached yet,
			 * continue searching the mft bitmap for a zero bit.
			 */
			if (data_pos < pass_end)
				continue;
		}
		/* Do the next pass. */
		if (++pass == 2) {
			/*
			 * Starting the second pass, in which we scan the first
			 * part of the zone which we omitted earlier.
			 */
			pass_end = pass_start;
			data_pos = pass_start = 24;
			ntfs_debug("pass %i, pass_start 0x%llx, pass_end "
					"0x%llx.", pass, (long long)pass_start,
					(long long)pass_end);
			if (data_pos >= pass_end)
				break;
		}
	}
	/* No free mft records in currently initialized mft bitmap. */
	ntfs_debug("Done.  (No free mft records left in currently initialized "
			"mft bitmap.)");
	return -ENOSPC;
}

/**
 * ntfs_mft_bitmap_extend_allocation_nolock - extend mft bitmap by a cluster
 * @vol:	volume on which to extend the mft bitmap attribute
 *
 * Extend the mft bitmap attribute on the ntfs volume @vol by one cluster.
 *
 * Note: Only changes allocated_size, i.e. does not touch initialized_size or
 * data_size.
 *
 * Return 0 on success and -errno on error.
 *
 * Locking: - Caller must hold vol->mftbmp_lock for writing.
 *	    - This function takes NTFS_I(vol->mftbmp_ino)->runlist.lock for
 *	      writing and releases it before returning.
 *	    - This function takes vol->lcnbmp_lock for writing and releases it
 *	      before returning.
 */
static int ntfs_mft_bitmap_extend_allocation_nolock(ntfs_volume *vol)
{
	LCN lcn;
	s64 ll;
	unsigned long flags;
	struct page *page;
	ntfs_inode *mft_ni, *mftbmp_ni;
	runlist_element *rl, *rl2 = NULL;
	ntfs_attr_search_ctx *ctx = NULL;
	MFT_RECORD *mrec;
	ATTR_RECORD *a = NULL;
	int ret, mp_size;
	u32 old_alen = 0;
	u8 *b, tb;
	struct {
		u8 added_cluster:1;
		u8 added_run:1;
		u8 mp_rebuilt:1;
	} status = { 0, 0, 0 };

	ntfs_debug("Extending mft bitmap allocation.");
	mft_ni = NTFS_I(vol->mft_ino);
	mftbmp_ni = NTFS_I(vol->mftbmp_ino);
	/*
	 * Determine the last lcn of the mft bitmap.  The allocated size of the
	 * mft bitmap cannot be zero so we are ok to do this.
	 */
	down_write(&mftbmp_ni->runlist.lock);
	read_lock_irqsave(&mftbmp_ni->size_lock, flags);
	ll = mftbmp_ni->allocated_size;
	read_unlock_irqrestore(&mftbmp_ni->size_lock, flags);
	rl = ntfs_attr_find_vcn_nolock(mftbmp_ni,
			(ll - 1) >> vol->cluster_size_bits, NULL);
	if (unlikely(IS_ERR(rl) || !rl->length || rl->lcn < 0)) {
		up_write(&mftbmp_ni->runlist.lock);
		ntfs_error(vol->sb, "Failed to determine last allocated "
				"cluster of mft bitmap attribute.");
		if (!IS_ERR(rl))
			ret = -EIO;
		else
			ret = PTR_ERR(rl);
		return ret;
	}
	lcn = rl->lcn + rl->length;
	ntfs_debug("Last lcn of mft bitmap attribute is 0x%llx.",
			(long long)lcn);
	/*
	 * Attempt to get the cluster following the last allocated cluster by
	 * hand as it may be in the MFT zone so the allocator would not give it
	 * to us.
	 */
	ll = lcn >> 3;
	page = ntfs_map_page(vol->lcnbmp_ino->i_mapping,
			ll >> PAGE_CACHE_SHIFT);
	if (IS_ERR(page)) {
		up_write(&mftbmp_ni->runlist.lock);
		ntfs_error(vol->sb, "Failed to read from lcn bitmap.");
		return PTR_ERR(page);
	}
	b = (u8*)page_address(page) + (ll & ~PAGE_CACHE_MASK);
	tb = 1 << (lcn & 7ull);
	down_write(&vol->lcnbmp_lock);
	if (*b != 0xff && !(*b & tb)) {
		/* Next cluster is free, allocate it. */
		*b |= tb;
		flush_dcache_page(page);
		set_page_dirty(page);
		up_write(&vol->lcnbmp_lock);
		ntfs_unmap_page(page);
		/* Update the mft bitmap runlist. */
		rl->length++;
		rl[1].vcn++;
		status.added_cluster = 1;
		ntfs_debug("Appending one cluster to mft bitmap.");
	} else {
		up_write(&vol->lcnbmp_lock);
		ntfs_unmap_page(page);
		/* Allocate a cluster from the DATA_ZONE. */
		rl2 = ntfs_cluster_alloc(vol, rl[1].vcn, 1, lcn, DATA_ZONE,
				true);
		if (IS_ERR(rl2)) {
			up_write(&mftbmp_ni->runlist.lock);
			ntfs_error(vol->sb, "Failed to allocate a cluster for "
					"the mft bitmap.");
			return PTR_ERR(rl2);
		}
		rl = ntfs_runlists_merge(mftbmp_ni->runlist.rl, rl2);
		if (IS_ERR(rl)) {
			up_write(&mftbmp_ni->runlist.lock);
			ntfs_error(vol->sb, "Failed to merge runlists for mft "
					"bitmap.");
			if (ntfs_cluster_free_from_rl(vol, rl2)) {
				ntfs_error(vol->sb, "Failed to dealocate "
						"allocated cluster.%s", es);
				NVolSetErrors(vol);
			}
			ntfs_free(rl2);
			return PTR_ERR(rl);
		}
		mftbmp_ni->runlist.rl = rl;
		status.added_run = 1;
		ntfs_debug("Adding one run to mft bitmap.");
		/* Find the last run in the new runlist. */
		for (; rl[1].length; rl++)
			;
	}
	/*
	 * Update the attribute record as well.  Note: @rl is the last
	 * (non-terminator) runlist element of mft bitmap.
	 */
	mrec = map_mft_record(mft_ni);
	if (IS_ERR(mrec)) {
		ntfs_error(vol->sb, "Failed to map mft record.");
		ret = PTR_ERR(mrec);
		goto undo_alloc;
	}
	ctx = ntfs_attr_get_search_ctx(mft_ni, mrec);
	if (unlikely(!ctx)) {
		ntfs_error(vol->sb, "Failed to get search context.");
		ret = -ENOMEM;
		goto undo_alloc;
	}
	ret = ntfs_attr_lookup(mftbmp_ni->type, mftbmp_ni->name,
			mftbmp_ni->name_len, CASE_SENSITIVE, rl[1].vcn, NULL,
			0, ctx);
	if (unlikely(ret)) {
		ntfs_error(vol->sb, "Failed to find last attribute extent of "
				"mft bitmap attribute.");
		if (ret == -ENOENT)
			ret = -EIO;
		goto undo_alloc;
	}
	a = ctx->attr;
	ll = sle64_to_cpu(a->data.non_resident.lowest_vcn);
	/* Search back for the previous last allocated cluster of mft bitmap. */
	for (rl2 = rl; rl2 > mftbmp_ni->runlist.rl; rl2--) {
		if (ll >= rl2->vcn)
			break;
	}
	BUG_ON(ll < rl2->vcn);
	BUG_ON(ll >= rl2->vcn + rl2->length);
	/* Get the size for the new mapping pairs array for this extent. */
	mp_size = ntfs_get_size_for_mapping_pairs(vol, rl2, ll, -1);
	if (unlikely(mp_size <= 0)) {
		ntfs_error(vol->sb, "Get size for mapping pairs failed for "
				"mft bitmap attribute extent.");
		ret = mp_size;
		if (!ret)
			ret = -EIO;
		goto undo_alloc;
	}
	/* Expand the attribute record if necessary. */
	old_alen = le32_to_cpu(a->length);
	ret = ntfs_attr_record_resize(ctx->mrec, a, mp_size +
			le16_to_cpu(a->data.non_resident.mapping_pairs_offset));
	if (unlikely(ret)) {
		if (ret != -ENOSPC) {
			ntfs_error(vol->sb, "Failed to resize attribute "
					"record for mft bitmap attribute.");
			goto undo_alloc;
		}
		// TODO: Deal with this by moving this extent to a new mft
		// record or by starting a new extent in a new mft record or by
		// moving other attributes out of this mft record.
		// Note: It will need to be a special mft record and if none of
		// those are available it gets rather complicated...
		ntfs_error(vol->sb, "Not enough space in this mft record to "
				"accomodate extended mft bitmap attribute "
				"extent.  Cannot handle this yet.");
		ret = -EOPNOTSUPP;
		goto undo_alloc;
	}
	status.mp_rebuilt = 1;
	/* Generate the mapping pairs array directly into the attr record. */
	ret = ntfs_mapping_pairs_build(vol, (u8*)a +
			le16_to_cpu(a->data.non_resident.mapping_pairs_offset),
			mp_size, rl2, ll, -1, NULL);
	if (unlikely(ret)) {
		ntfs_error(vol->sb, "Failed to build mapping pairs array for "
				"mft bitmap attribute.");
		goto undo_alloc;
	}
	/* Update the highest_vcn. */
	a->data.non_resident.highest_vcn = cpu_to_sle64(rl[1].vcn - 1);
	/*
	 * We now have extended the mft bitmap allocated_size by one cluster.
	 * Reflect this in the ntfs_inode structure and the attribute record.
	 */
	if (a->data.non_resident.lowest_vcn) {
		/*
		 * We are not in the first attribute extent, switch to it, but
		 * first ensure the changes will make it to disk later.
		 */
		flush_dcache_mft_record_page(ctx->ntfs_ino);
		mark_mft_record_dirty(ctx->ntfs_ino);
		ntfs_attr_reinit_search_ctx(ctx);
		ret = ntfs_attr_lookup(mftbmp_ni->type, mftbmp_ni->name,
				mftbmp_ni->name_len, CASE_SENSITIVE, 0, NULL,
				0, ctx);
		if (unlikely(ret)) {
			ntfs_error(vol->sb, "Failed to find first attribute "
					"extent of mft bitmap attribute.");
			goto restore_undo_alloc;
		}
		a = ctx->attr;
	}
	write_lock_irqsave(&mftbmp_ni->size_lock, flags);
	mftbmp_ni->allocated_size += vol->cluster_size;
	a->data.non_resident.allocated_size =
			cpu_to_sle64(mftbmp_ni->allocated_size);
	write_unlock_irqrestore(&mftbmp_ni->size_lock, flags);
	/* Ensure the changes make it to disk. */
	flush_dcache_mft_record_page(ctx->ntfs_ino);
	mark_mft_record_dirty(ctx->ntfs_ino);
	ntfs_attr_put_search_ctx(ctx);
	unmap_mft_record(mft_ni);
	up_write(&mftbmp_ni->runlist.lock);
	ntfs_debug("Done.");
	return 0;
restore_undo_alloc:
	ntfs_attr_reinit_search_ctx(ctx);
	if (ntfs_attr_lookup(mftbmp_ni->type, mftbmp_ni->name,
			mftbmp_ni->name_len, CASE_SENSITIVE, rl[1].vcn, NULL,
			0, ctx)) {
		ntfs_error(vol->sb, "Failed to find last attribute extent of "
				"mft bitmap attribute.%s", es);
		write_lock_irqsave(&mftbmp_ni->size_lock, flags);
		mftbmp_ni->allocated_size += vol->cluster_size;
		write_unlock_irqrestore(&mftbmp_ni->size_lock, flags);
		ntfs_attr_put_search_ctx(ctx);
		unmap_mft_record(mft_ni);
		up_write(&mftbmp_ni->runlist.lock);
		/*
		 * The only thing that is now wrong is ->allocated_size of the
		 * base attribute extent which chkdsk should be able to fix.
		 */
		NVolSetErrors(vol);
		return ret;
	}
	a = ctx->attr;
	a->data.non_resident.highest_vcn = cpu_to_sle64(rl[1].vcn - 2);
undo_alloc:
	if (status.added_cluster) {
		/* Truncate the last run in the runlist by one cluster. */
		rl->length--;
		rl[1].vcn--;
	} else if (status.added_run) {
		lcn = rl->lcn;
		/* Remove the last run from the runlist. */
		rl->lcn = rl[1].lcn;
		rl->length = 0;
	}
	/* Deallocate the cluster. */
	down_write(&vol->lcnbmp_lock);
	if (ntfs_bitmap_clear_bit(vol->lcnbmp_ino, lcn)) {
		ntfs_error(vol->sb, "Failed to free allocated cluster.%s", es);
		NVolSetErrors(vol);
	}
	up_write(&vol->lcnbmp_lock);
	if (status.mp_rebuilt) {
		if (ntfs_mapping_pairs_build(vol, (u8*)a + le16_to_cpu(
				a->data.non_resident.mapping_pairs_offset),
				old_alen - le16_to_cpu(
				a->data.non_resident.mapping_pairs_offset),
				rl2, ll, -1, NULL)) {
			ntfs_error(vol->sb, "Failed to restore mapping pairs "
					"array.%s", es);
			NVolSetErrors(vol);
		}
		if (ntfs_attr_record_resize(ctx->mrec, a, old_alen)) {
			ntfs_error(vol->sb, "Failed to restore attribute "
					"record.%s", es);
			NVolSetErrors(vol);
		}
		flush_dcache_mft_record_page(ctx->ntfs_ino);
		mark_mft_record_dirty(ctx->ntfs_ino);
	}
	if (ctx)
		ntfs_attr_put_search_ctx(ctx);
	if (!IS_ERR(mrec))
		unmap_mft_record(mft_ni);
	up_write(&mftbmp_ni->runlist.lock);
	return ret;
}

/**
 * ntfs_mft_bitmap_extend_initialized_nolock - extend mftbmp initialized data
 * @vol:	volume on which to extend the mft bitmap attribute
 *
 * Extend the initialized portion of the mft bitmap attribute on the ntfs
 * volume @vol by 8 bytes.
 *
 * Note:  Only changes initialized_size and data_size, i.e. requires that
 * allocated_size is big enough to fit the new initialized_size.
 *
 * Return 0 on success and -error on error.
 *
 * Locking: Caller must hold vol->mftbmp_lock for writing.
 */
static int ntfs_mft_bitmap_extend_initialized_nolock(ntfs_volume *vol)
{
	s64 old_data_size, old_initialized_size;
	unsigned long flags;
	struct inode *mftbmp_vi;
	ntfs_inode *mft_ni, *mftbmp_ni;
	ntfs_attr_search_ctx *ctx;
	MFT_RECORD *mrec;
	ATTR_RECORD *a;
	int ret;

	ntfs_debug("Extending mft bitmap initiailized (and data) size.");
	mft_ni = NTFS_I(vol->mft_ino);
	mftbmp_vi = vol->mftbmp_ino;
	mftbmp_ni = NTFS_I(mftbmp_vi);
	/* Get the attribute record. */
	mrec = map_mft_record(mft_ni);
	if (IS_ERR(mrec)) {
		ntfs_error(vol->sb, "Failed to map mft record.");
		return PTR_ERR(mrec);
	}
	ctx = ntfs_attr_get_search_ctx(mft_ni, mrec);
	if (unlikely(!ctx)) {
		ntfs_error(vol->sb, "Failed to get search context.");
		ret = -ENOMEM;
		goto unm_err_out;
	}
	ret = ntfs_attr_lookup(mftbmp_ni->type, mftbmp_ni->name,
			mftbmp_ni->name_len, CASE_SENSITIVE, 0, NULL, 0, ctx);
	if (unlikely(ret)) {
		ntfs_error(vol->sb, "Failed to find first attribute extent of "
				"mft bitmap attribute.");
		if (ret == -ENOENT)
			ret = -EIO;
		goto put_err_out;
	}
	a = ctx->attr;
	write_lock_irqsave(&mftbmp_ni->size_lock, flags);
	old_data_size = i_size_read(mftbmp_vi);
	old_initialized_size = mftbmp_ni->initialized_size;
	/*
	 * We can simply update the initialized_size before filling the space
	 * with zeroes because the caller is holding the mft bitmap lock for
	 * writing which ensures that no one else is trying to access the data.
	 */
	mftbmp_ni->initialized_size += 8;
	a->data.non_resident.initialized_size =
			cpu_to_sle64(mftbmp_ni->initialized_size);
	if (mftbmp_ni->initialized_size > old_data_size) {
		i_size_write(mftbmp_vi, mftbmp_ni->initialized_size);
		a->data.non_resident.data_size =
				cpu_to_sle64(mftbmp_ni->initialized_size);
	}
	write_unlock_irqrestore(&mftbmp_ni->size_lock, flags);
	/* Ensure the changes make it to disk. */
	flush_dcache_mft_record_page(ctx->ntfs_ino);
	mark_mft_record_dirty(ctx->ntfs_ino);
	ntfs_attr_put_search_ctx(ctx);
	unmap_mft_record(mft_ni);
	/* Initialize the mft bitmap attribute value with zeroes. */
	ret = ntfs_attr_set(mftbmp_ni, old_initialized_size, 8, 0);
	if (likely(!ret)) {
		ntfs_debug("Done.  (Wrote eight initialized bytes to mft "
				"bitmap.");
		return 0;
	}
	ntfs_error(vol->sb, "Failed to write to mft bitmap.");
	/* Try to recover from the error. */
	mrec = map_mft_record(mft_ni);
	if (IS_ERR(mrec)) {
		ntfs_error(vol->sb, "Failed to map mft record.%s", es);
		NVolSetErrors(vol);
		return ret;
	}
	ctx = ntfs_attr_get_search_ctx(mft_ni, mrec);
	if (unlikely(!ctx)) {
		ntfs_error(vol->sb, "Failed to get search context.%s", es);
		NVolSetErrors(vol);
		goto unm_err_out;
	}
	if (ntfs_attr_lookup(mftbmp_ni->type, mftbmp_ni->name,
			mftbmp_ni->name_len, CASE_SENSITIVE, 0, NULL, 0, ctx)) {
		ntfs_error(vol->sb, "Failed to find first attribute extent of "
				"mft bitmap attribute.%s", es);
		NVolSetErrors(vol);
put_err_out:
		ntfs_attr_put_search_ctx(ctx);
unm_err_out:
		unmap_mft_record(mft_ni);
		goto err_out;
	}
	a = ctx->attr;
	write_lock_irqsave(&mftbmp_ni->size_lock, flags);
	mftbmp_ni->initialized_size = old_initialized_size;
	a->data.non_resident.initialized_size =
			cpu_to_sle64(old_initialized_size);
	if (i_size_read(mftbmp_vi) != old_data_size) {
		i_size_write(mftbmp_vi, old_data_size);
		a->data.non_resident.data_size = cpu_to_sle64(old_data_size);
	}
	write_unlock_irqrestore(&mftbmp_ni->size_lock, flags);
	flush_dcache_mft_record_page(ctx->ntfs_ino);
	mark_mft_record_dirty(ctx->ntfs_ino);
	ntfs_attr_put_search_ctx(ctx);
	unmap_mft_record(mft_ni);
#ifdef DEBUG
	read_lock_irqsave(&mftbmp_ni->size_lock, flags);
	ntfs_debug("Restored status of mftbmp: allocated_size 0x%llx, "
			"data_size 0x%llx, initialized_size 0x%llx.",
			(long long)mftbmp_ni->allocated_size,
			(long long)i_size_read(mftbmp_vi),
			(long long)mftbmp_ni->initialized_size);
	read_unlock_irqrestore(&mftbmp_ni->size_lock, flags);
#endif /* DEBUG */
err_out:
	return ret;
}

/**
 * ntfs_mft_data_extend_allocation_nolock - extend mft data attribute
 * @vol:	volume on which to extend the mft data attribute
 *
 * Extend the mft data attribute on the ntfs volume @vol by 16 mft records
 * worth of clusters or if not enough space for this by one mft record worth
 * of clusters.
 *
 * Note:  Only changes allocated_size, i.e. does not touch initialized_size or
 * data_size.
 *
 * Return 0 on success and -errno on error.
 *
 * Locking: - Caller must hold vol->mftbmp_lock for writing.
 *	    - This function takes NTFS_I(vol->mft_ino)->runlist.lock for
 *	      writing and releases it before returning.
 *	    - This function calls functions which take vol->lcnbmp_lock for
 *	      writing and release it before returning.
 */
static int ntfs_mft_data_extend_allocation_nolock(ntfs_volume *vol)
{
	LCN lcn;
	VCN old_last_vcn;
	s64 min_nr, nr, ll;
	unsigned long flags;
	ntfs_inode *mft_ni;
	runlist_element *rl, *rl2;
	ntfs_attr_search_ctx *ctx = NULL;
	MFT_RECORD *mrec;
	ATTR_RECORD *a = NULL;
	int ret, mp_size;
	u32 old_alen = 0;
	bool mp_rebuilt = false;

	ntfs_debug("Extending mft data allocation.");
	mft_ni = NTFS_I(vol->mft_ino);
	/*
	 * Determine the preferred allocation location, i.e. the last lcn of
	 * the mft data attribute.  The allocated size of the mft data
	 * attribute cannot be zero so we are ok to do this.
	 */
	down_write(&mft_ni->runlist.lock);
	read_lock_irqsave(&mft_ni->size_lock, flags);
	ll = mft_ni->allocated_size;
	read_unlock_irqrestore(&mft_ni->size_lock, flags);
	rl = ntfs_attr_find_vcn_nolock(mft_ni,
			(ll - 1) >> vol->cluster_size_bits, NULL);
	if (unlikely(IS_ERR(rl) || !rl->length || rl->lcn < 0)) {
		up_write(&mft_ni->runlist.lock);
		ntfs_error(vol->sb, "Failed to determine last allocated "
				"cluster of mft data attribute.");
		if (!IS_ERR(rl))
			ret = -EIO;
		else
			ret = PTR_ERR(rl);
		return ret;
	}
	lcn = rl->lcn + rl->length;
	ntfs_debug("Last lcn of mft data attribute is 0x%llx.", (long long)lcn);
	/* Minimum allocation is one mft record worth of clusters. */
	min_nr = vol->mft_record_size >> vol->cluster_size_bits;
	if (!min_nr)
		min_nr = 1;
	/* Want to allocate 16 mft records worth of clusters. */
	nr = vol->mft_record_size << 4 >> vol->cluster_size_bits;
	if (!nr)
		nr = min_nr;
	/* Ensure we do not go above 2^32-1 mft records. */
	read_lock_irqsave(&mft_ni->size_lock, flags);
	ll = mft_ni->allocated_size;
	read_unlock_irqrestore(&mft_ni->size_lock, flags);
	if (unlikely((ll + (nr << vol->cluster_size_bits)) >>
			vol->mft_record_size_bits >= (1ll << 32))) {
		nr = min_nr;
		if (unlikely((ll + (nr << vol->cluster_size_bits)) >>
				vol->mft_record_size_bits >= (1ll << 32))) {
			ntfs_warning(vol->sb, "Cannot allocate mft record "
					"because the maximum number of inodes "
					"(2^32) has already been reached.");
			up_write(&mft_ni->runlist.lock);
			return -ENOSPC;
		}
	}
	ntfs_debug("Trying mft data allocation with %s cluster count %lli.",
			nr > min_nr ? "default" : "minimal", (long long)nr);
	old_last_vcn = rl[1].vcn;
	do {
		rl2 = ntfs_cluster_alloc(vol, old_last_vcn, nr, lcn, MFT_ZONE,
				true);
		if (likely(!IS_ERR(rl2)))
			break;
		if (PTR_ERR(rl2) != -ENOSPC || nr == min_nr) {
			ntfs_error(vol->sb, "Failed to allocate the minimal "
					"number of clusters (%lli) for the "
					"mft data attribute.", (long long)nr);
			up_write(&mft_ni->runlist.lock);
			return PTR_ERR(rl2);
		}
		/*
		 * There is not enough space to do the allocation, but there
		 * might be enough space to do a minimal allocation so try that
		 * before failing.
		 */
		nr = min_nr;
		ntfs_debug("Retrying mft data allocation with minimal cluster "
				"count %lli.", (long long)nr);
	} while (1);
	rl = ntfs_runlists_merge(mft_ni->runlist.rl, rl2);
	if (IS_ERR(rl)) {
		up_write(&mft_ni->runlist.lock);
		ntfs_error(vol->sb, "Failed to merge runlists for mft data "
				"attribute.");
		if (ntfs_cluster_free_from_rl(vol, rl2)) {
			ntfs_error(vol->sb, "Failed to dealocate clusters "
					"from the mft data attribute.%s", es);
			NVolSetErrors(vol);
		}
		ntfs_free(rl2);
		return PTR_ERR(rl);
	}
	mft_ni->runlist.rl = rl;
	ntfs_debug("Allocated %lli clusters.", (long long)nr);
	/* Find the last run in the new runlist. */
	for (; rl[1].length; rl++)
		;
	/* Update the attribute record as well. */
	mrec = map_mft_record(mft_ni);
	if (IS_ERR(mrec)) {
		ntfs_error(vol->sb, "Failed to map mft record.");
		ret = PTR_ERR(mrec);
		goto undo_alloc;
	}
	ctx = ntfs_attr_get_search_ctx(mft_ni, mrec);
	if (unlikely(!ctx)) {
		ntfs_error(vol->sb, "Failed to get search context.");
		ret = -ENOMEM;
		goto undo_alloc;
	}
	ret = ntfs_attr_lookup(mft_ni->type, mft_ni->name, mft_ni->name_len,
			CASE_SENSITIVE, rl[1].vcn, NULL, 0, ctx);
	if (unlikely(ret)) {
		ntfs_error(vol->sb, "Failed to find last attribute extent of "
				"mft data attribute.");
		if (ret == -ENOENT)
			ret = -EIO;
		goto undo_alloc;
	}
	a = ctx->attr;
	ll = sle64_to_cpu(a->data.non_resident.lowest_vcn);
	/* Search back for the previous last allocated cluster of mft bitmap. */
	for (rl2 = rl; rl2 > mft_ni->runlist.rl; rl2--) {
		if (ll >= rl2->vcn)
			break;
	}
	BUG_ON(ll < rl2->vcn);
	BUG_ON(ll >= rl2->vcn + rl2->length);
	/* Get the size for the new mapping pairs array for this extent. */
	mp_size = ntfs_get_size_for_mapping_pairs(vol, rl2, ll, -1);
	if (unlikely(mp_size <= 0)) {
		ntfs_error(vol->sb, "Get size for mapping pairs failed for "
				"mft data attribute extent.");
		ret = mp_size;
		if (!ret)
			ret = -EIO;
		goto undo_alloc;
	}
	/* Expand the attribute record if necessary. */
	old_alen = le32_to_cpu(a->length);
	ret = ntfs_attr_record_resize(ctx->mrec, a, mp_size +
			le16_to_cpu(a->data.non_resident.mapping_pairs_offset));
	if (unlikely(ret)) {
		if (ret != -ENOSPC) {
			ntfs_error(vol->sb, "Failed to resize attribute "
					"record for mft data attribute.");
			goto undo_alloc;
		}
		// TODO: Deal with this by moving this extent to a new mft
		// record or by starting a new extent in a new mft record or by
		// moving other attributes out of this mft record.
		// Note: Use the special reserved mft records and ensure that
		// this extent is not required to find the mft record in
		// question.  If no free special records left we would need to
		// move an existing record away, insert ours in its place, and
		// then place the moved record into the newly allocated space
		// and we would then need to update all references to this mft
		// record appropriately.  This is rather complicated...
		ntfs_error(vol->sb, "Not enough space in this mft record to "
				"accomodate extended mft data attribute "
				"extent.  Cannot handle this yet.");
		ret = -EOPNOTSUPP;
		goto undo_alloc;
	}
	mp_rebuilt = true;
	/* Generate the mapping pairs array directly into the attr record. */
	ret = ntfs_mapping_pairs_build(vol, (u8*)a +
			le16_to_cpu(a->data.non_resident.mapping_pairs_offset),
			mp_size, rl2, ll, -1, NULL);
	if (unlikely(ret)) {
		ntfs_error(vol->sb, "Failed to build mapping pairs array of "
				"mft data attribute.");
		goto undo_alloc;
	}
	/* Update the highest_vcn. */
	a->data.non_resident.highest_vcn = cpu_to_sle64(rl[1].vcn - 1);
	/*
	 * We now have extended the mft data allocated_size by nr clusters.
	 * Reflect this in the ntfs_inode structure and the attribute record.
	 * @rl is the last (non-terminator) runlist element of mft data
	 * attribute.
	 */
	if (a->data.non_resident.lowest_vcn) {
		/*
		 * We are not in the first attribute extent, switch to it, but
		 * first ensure the changes will make it to disk later.
		 */
		flush_dcache_mft_record_page(ctx->ntfs_ino);
		mark_mft_record_dirty(ctx->ntfs_ino);
		ntfs_attr_reinit_search_ctx(ctx);
		ret = ntfs_attr_lookup(mft_ni->type, mft_ni->name,
				mft_ni->name_len, CASE_SENSITIVE, 0, NULL, 0,
				ctx);
		if (unlikely(ret)) {
			ntfs_error(vol->sb, "Failed to find first attribute "
					"extent of mft data attribute.");
			goto restore_undo_alloc;
		}
		a = ctx->attr;
	}
	write_lock_irqsave(&mft_ni->size_lock, flags);
	mft_ni->allocated_size += nr << vol->cluster_size_bits;
	a->data.non_resident.allocated_size =
			cpu_to_sle64(mft_ni->allocated_size);
	write_unlock_irqrestore(&mft_ni->size_lock, flags);
	/* Ensure the changes make it to disk. */
	flush_dcache_mft_record_page(ctx->ntfs_ino);
	mark_mft_record_dirty(ctx->ntfs_ino);
	ntfs_attr_put_search_ctx(ctx);
	unmap_mft_record(mft_ni);
	up_write(&mft_ni->runlist.lock);
	ntfs_debug("Done.");
	return 0;
restore_undo_alloc:
	ntfs_attr_reinit_search_ctx(ctx);
	if (ntfs_attr_lookup(mft_ni->type, mft_ni->name, mft_ni->name_len,
			CASE_SENSITIVE, rl[1].vcn, NULL, 0, ctx)) {
		ntfs_error(vol->sb, "Failed to find last attribute extent of "
				"mft data attribute.%s", es);
		write_lock_irqsave(&mft_ni->size_lock, flags);
		mft_ni->allocated_size += nr << vol->cluster_size_bits;
		write_unlock_irqrestore(&mft_ni->size_lock, flags);
		ntfs_attr_put_search_ctx(ctx);
		unmap_mft_record(mft_ni);
		up_write(&mft_ni->runlist.lock);
		/*
		 * The only thing that is now wrong is ->allocated_size of the
		 * base attribute extent which chkdsk should be able to fix.
		 */
		NVolSetErrors(vol);
		return ret;
	}
	ctx->attr->data.non_resident.highest_vcn =
			cpu_to_sle64(old_last_vcn - 1);
undo_alloc:
	if (ntfs_cluster_free(mft_ni, old_last_vcn, -1, ctx) < 0) {
		ntfs_error(vol->sb, "Failed to free clusters from mft data "
				"attribute.%s", es);
		NVolSetErrors(vol);
	}
	a = ctx->attr;
	if (ntfs_rl_truncate_nolock(vol, &mft_ni->runlist, old_last_vcn)) {
		ntfs_error(vol->sb, "Failed to truncate mft data attribute "
				"runlist.%s", es);
		NVolSetErrors(vol);
	}
	if (mp_rebuilt && !IS_ERR(ctx->mrec)) {
		if (ntfs_mapping_pairs_build(vol, (u8*)a + le16_to_cpu(
				a->data.non_resident.mapping_pairs_offset),
				old_alen - le16_to_cpu(
				a->data.non_resident.mapping_pairs_offset),
				rl2, ll, -1, NULL)) {
			ntfs_error(vol->sb, "Failed to restore mapping pairs "
					"array.%s", es);
			NVolSetErrors(vol);
		}
		if (ntfs_attr_record_resize(ctx->mrec, a, old_alen)) {
			ntfs_error(vol->sb, "Failed to restore attribute "
					"record.%s", es);
			NVolSetErrors(vol);
		}
		flush_dcache_mft_record_page(ctx->ntfs_ino);
		mark_mft_record_dirty(ctx->ntfs_ino);
	} else if (IS_ERR(ctx->mrec)) {
		ntfs_error(vol->sb, "Failed to restore attribute search "
				"context.%s", es);
		NVolSetErrors(vol);
	}
	if (ctx)
		ntfs_attr_put_search_ctx(ctx);
	if (!IS_ERR(mrec))
		unmap_mft_record(mft_ni);
	up_write(&mft_ni->runlist.lock);
	return ret;
}

/**
 * ntfs_mft_record_layout - layout an mft record into a memory buffer
 * @vol:	volume to which the mft record will belong
 * @mft_no:	mft reference specifying the mft record number
 * @m:		destination buffer of size >= @vol->mft_record_size bytes
 *
 * Layout an empty, unused mft record with the mft record number @mft_no into
 * the buffer @m.  The volume @vol is needed because the mft record structure
 * was modified in NTFS 3.1 so we need to know which volume version this mft
 * record will be used on.
 *
 * Return 0 on success and -errno on error.
 */
static int ntfs_mft_record_layout(const ntfs_volume *vol, const s64 mft_no,
		MFT_RECORD *m)
{
	ATTR_RECORD *a;

	ntfs_debug("Entering for mft record 0x%llx.", (long long)mft_no);
	if (mft_no >= (1ll << 32)) {
		ntfs_error(vol->sb, "Mft record number 0x%llx exceeds "
				"maximum of 2^32.", (long long)mft_no);
		return -ERANGE;
	}
	/* Start by clearing the whole mft record to gives us a clean slate. */
	memset(m, 0, vol->mft_record_size);
	/* Aligned to 2-byte boundary. */
	if (vol->major_ver < 3 || (vol->major_ver == 3 && !vol->minor_ver))
		m->usa_ofs = cpu_to_le16((sizeof(MFT_RECORD_OLD) + 1) & ~1);
	else {
		m->usa_ofs = cpu_to_le16((sizeof(MFT_RECORD) + 1) & ~1);
		/*
		 * Set the NTFS 3.1+ specific fields while we know that the
		 * volume version is 3.1+.
		 */
		m->reserved = 0;
		m->mft_record_number = cpu_to_le32((u32)mft_no);
	}
	m->magic = magic_FILE;
	if (vol->mft_record_size >= NTFS_BLOCK_SIZE)
		m->usa_count = cpu_to_le16(vol->mft_record_size /
				NTFS_BLOCK_SIZE + 1);
	else {
		m->usa_count = cpu_to_le16(1);
		ntfs_warning(vol->sb, "Sector size is bigger than mft record "
				"size.  Setting usa_count to 1.  If chkdsk "
				"reports this as corruption, please email "
				"linux-ntfs-dev@lists.sourceforge.net stating "
				"that you saw this message and that the "
				"modified filesystem created was corrupt.  "
				"Thank you.");
	}
	/* Set the update sequence number to 1. */
	*(le16*)((u8*)m + le16_to_cpu(m->usa_ofs)) = cpu_to_le16(1);
	m->lsn = 0;
	m->sequence_number = cpu_to_le16(1);
	m->link_count = 0;
	/*
	 * Place the attributes straight after the update sequence array,
	 * aligned to 8-byte boundary.
	 */
	m->attrs_offset = cpu_to_le16((le16_to_cpu(m->usa_ofs) +
			(le16_to_cpu(m->usa_count) << 1) + 7) & ~7);
	m->flags = 0;
	/*
	 * Using attrs_offset plus eight bytes (for the termination attribute).
	 * attrs_offset is already aligned to 8-byte boundary, so no need to
	 * align again.
	 */
	m->bytes_in_use = cpu_to_le32(le16_to_cpu(m->attrs_offset) + 8);
	m->bytes_allocated = cpu_to_le32(vol->mft_record_size);
	m->base_mft_record = 0;
	m->next_attr_instance = 0;
	/* Add the termination attribute. */
	a = (ATTR_RECORD*)((u8*)m + le16_to_cpu(m->attrs_offset));
	a->type = AT_END;
	a->length = 0;
	ntfs_debug("Done.");
	return 0;
}

/**
 * ntfs_mft_record_format - format an mft record on an ntfs volume
 * @vol:	volume on which to format the mft record
 * @mft_no:	mft record number to format
 *
 * Format the mft record @mft_no in $MFT/$DATA, i.e. lay out an empty, unused
 * mft record into the appropriate place of the mft data attribute.  This is
 * used when extending the mft data attribute.
 *
 * Return 0 on success and -errno on error.
 */
static int ntfs_mft_record_format(const ntfs_volume *vol, const s64 mft_no)
{
	loff_t i_size;
	struct inode *mft_vi = vol->mft_ino;
	struct page *page;
	MFT_RECORD *m;
	pgoff_t index, end_index;
	unsigned int ofs;
	int err;

	ntfs_debug("Entering for mft record 0x%llx.", (long long)mft_no);
	/*
	 * The index into the page cache and the offset within the page cache
	 * page of the wanted mft record.
	 */
	index = mft_no << vol->mft_record_size_bits >> PAGE_CACHE_SHIFT;
	ofs = (mft_no << vol->mft_record_size_bits) & ~PAGE_CACHE_MASK;
	/* The maximum valid index into the page cache for $MFT's data. */
	i_size = i_size_read(mft_vi);
	end_index = i_size >> PAGE_CACHE_SHIFT;
	if (unlikely(index >= end_index)) {
		if (unlikely(index > end_index || ofs + vol->mft_record_size >=
				(i_size & ~PAGE_CACHE_MASK))) {
			ntfs_error(vol->sb, "Tried to format non-existing mft "
					"record 0x%llx.", (long long)mft_no);
			return -ENOENT;
		}
	}
	/* Read, map, and pin the page containing the mft record. */
	page = ntfs_map_page(mft_vi->i_mapping, index);
	if (IS_ERR(page)) {
		ntfs_error(vol->sb, "Failed to map page containing mft record "
				"to format 0x%llx.", (long long)mft_no);
		return PTR_ERR(page);
	}
	lock_page(page);
	BUG_ON(!PageUptodate(page));
	ClearPageUptodate(page);
	m = (MFT_RECORD*)((u8*)page_address(page) + ofs);
	err = ntfs_mft_record_layout(vol, mft_no, m);
	if (unlikely(err)) {
		ntfs_error(vol->sb, "Failed to layout mft record 0x%llx.",
				(long long)mft_no);
		SetPageUptodate(page);
		unlock_page(page);
		ntfs_unmap_page(page);
		return err;
	}
	flush_dcache_page(page);
	SetPageUptodate(page);
	unlock_page(page);
	/*
	 * Make sure the mft record is written out to disk.  We could use
	 * ilookup5() to check if an inode is in icache and so on but this is
	 * unnecessary as ntfs_writepage() will write the dirty record anyway.
	 */
	mark_ntfs_record_dirty(page, ofs);
	ntfs_unmap_page(page);
	ntfs_debug("Done.");
	return 0;
}

/**
 * ntfs_mft_record_alloc - allocate an mft record on an ntfs volume
 * @vol:	[IN]  volume on which to allocate the mft record
 * @mode:	[IN]  mode if want a file or directory, i.e. base inode or 0
 * @base_ni:	[IN]  open base inode if allocating an extent mft record or NULL
 * @mrec:	[OUT] on successful return this is the mapped mft record
 *
 * Allocate an mft record in $MFT/$DATA of an open ntfs volume @vol.
 *
 * If @base_ni is NULL make the mft record a base mft record, i.e. a file or
 * direvctory inode, and allocate it at the default allocator position.  In
 * this case @mode is the file mode as given to us by the caller.  We in
 * particular use @mode to distinguish whether a file or a directory is being
 * created (S_IFDIR(mode) and S_IFREG(mode), respectively).
 *
 * If @base_ni is not NULL make the allocated mft record an extent record,
 * allocate it starting at the mft record after the base mft record and attach
 * the allocated and opened ntfs inode to the base inode @base_ni.  In this
 * case @mode must be 0 as it is meaningless for extent inodes.
 *
 * You need to check the return value with IS_ERR().  If false, the function
 * was successful and the return value is the now opened ntfs inode of the
 * allocated mft record.  *@mrec is then set to the allocated, mapped, pinned,
 * and locked mft record.  If IS_ERR() is true, the function failed and the
 * error code is obtained from PTR_ERR(return value).  *@mrec is undefined in
 * this case.
 *
 * Allocation strategy:
 *
 * To find a free mft record, we scan the mft bitmap for a zero bit.  To
 * optimize this we start scanning at the place specified by @base_ni or if
 * @base_ni is NULL we start where we last stopped and we perform wrap around
 * when we reach the end.  Note, we do not try to allocate mft records below
 * number 24 because numbers 0 to 15 are the defined system files anyway and 16
 * to 24 are special in that they are used for storing extension mft records
 * for the $DATA attribute of $MFT.  This is required to avoid the possibility
 * of creating a runlist with a circular dependency which once written to disk
 * can never be read in again.  Windows will only use records 16 to 24 for
 * normal files if the volume is completely out of space.  We never use them
 * which means that when the volume is really out of space we cannot create any
 * more files while Windows can still create up to 8 small files.  We can start
 * doing this at some later time, it does not matter much for now.
 *
 * When scanning the mft bitmap, we only search up to the last allocated mft
 * record.  If there are no free records left in the range 24 to number of
 * allocated mft records, then we extend the $MFT/$DATA attribute in order to
 * create free mft records.  We extend the allocated size of $MFT/$DATA by 16
 * records at a time or one cluster, if cluster size is above 16kiB.  If there
 * is not sufficient space to do this, we try to extend by a single mft record
 * or one cluster, if cluster size is above the mft record size.
 *
 * No matter how many mft records we allocate, we initialize only the first
 * allocated mft record, incrementing mft data size and initialized size
 * accordingly, open an ntfs_inode for it and return it to the caller, unless
 * there are less than 24 mft records, in which case we allocate and initialize
 * mft records until we reach record 24 which we consider as the first free mft
 * record for use by normal files.
 *
 * If during any stage we overflow the initialized data in the mft bitmap, we
 * extend the initialized size (and data size) by 8 bytes, allocating another
 * cluster if required.  The bitmap data size has to be at least equal to the
 * number of mft records in the mft, but it can be bigger, in which case the
 * superflous bits are padded with zeroes.
 *
 * Thus, when we return successfully (IS_ERR() is false), we will have:
 *	- initialized / extended the mft bitmap if necessary,
 *	- initialized / extended the mft data if necessary,
 *	- set the bit corresponding to the mft record being allocated in the
 *	  mft bitmap,
 *	- opened an ntfs_inode for the allocated mft record, and we will have
 *	- returned the ntfs_inode as well as the allocated mapped, pinned, and
 *	  locked mft record.
 *
 * On error, the volume will be left in a consistent state and no record will
 * be allocated.  If rolling back a partial operation fails, we may leave some
 * inconsistent metadata in which case we set NVolErrors() so the volume is
 * left dirty when unmounted.
 *
 * Note, this function cannot make use of most of the normal functions, like
 * for example for attribute resizing, etc, because when the run list overflows
 * the base mft record and an attribute list is used, it is very important that
 * the extension mft records used to store the $DATA attribute of $MFT can be
 * reached without having to read the information contained inside them, as
 * this would make it impossible to find them in the first place after the
 * volume is unmounted.  $MFT/$BITMAP probably does not need to follow this
 * rule because the bitmap is not essential for finding the mft records, but on
 * the other hand, handling the bitmap in this special way would make life
 * easier because otherwise there might be circular invocations of functions
 * when reading the bitmap.
 */
ntfs_inode *ntfs_mft_record_alloc(ntfs_volume *vol, const int mode,
		ntfs_inode *base_ni, MFT_RECORD **mrec)
{
	s64 ll, bit, old_data_initialized, old_data_size;
	unsigned long flags;
	struct inode *vi;
	struct page *page;
	ntfs_inode *mft_ni, *mftbmp_ni, *ni;
	ntfs_attr_search_ctx *ctx;
	MFT_RECORD *m;
	ATTR_RECORD *a;
	pgoff_t index;
	unsigned int ofs;
	int err;
	le16 seq_no, usn;
	bool record_formatted = false;

	if (base_ni) {
		ntfs_debug("Entering (allocating an extent mft record for "
				"base mft record 0x%llx).",
				(long long)base_ni->mft_no);
		/* @mode and @base_ni are mutually exclusive. */
		BUG_ON(mode);
	} else
		ntfs_debug("Entering (allocating a base mft record).");
	if (mode) {
		/* @mode and @base_ni are mutually exclusive. */
		BUG_ON(base_ni);
		/* We only support creation of normal files and directories. */
		if (!S_ISREG(mode) && !S_ISDIR(mode))
			return ERR_PTR(-EOPNOTSUPP);
	}
	BUG_ON(!mrec);
	mft_ni = NTFS_I(vol->mft_ino);
	mftbmp_ni = NTFS_I(vol->mftbmp_ino);
	down_write(&vol->mftbmp_lock);
	bit = ntfs_mft_bitmap_find_and_alloc_free_rec_nolock(vol, base_ni);
	if (bit >= 0) {
		ntfs_debug("Found and allocated free record (#1), bit 0x%llx.",
				(long long)bit);
		goto have_alloc_rec;
	}
	if (bit != -ENOSPC) {
		up_write(&vol->mftbmp_lock);
		return ERR_PTR(bit);
	}
	/*
	 * No free mft records left.  If the mft bitmap already covers more
	 * than the currently used mft records, the next records are all free,
	 * so we can simply allocate the first unused mft record.
	 * Note: We also have to make sure that the mft bitmap at least covers
	 * the first 24 mft records as they are special and whilst they may not
	 * be in use, we do not allocate from them.
	 */
	read_lock_irqsave(&mft_ni->size_lock, flags);
	ll = mft_ni->initialized_size >> vol->mft_record_size_bits;
	read_unlock_irqrestore(&mft_ni->size_lock, flags);
	read_lock_irqsave(&mftbmp_ni->size_lock, flags);
	old_data_initialized = mftbmp_ni->initialized_size;
	read_unlock_irqrestore(&mftbmp_ni->size_lock, flags);
	if (old_data_initialized << 3 > ll && old_data_initialized > 3) {
		bit = ll;
		if (bit < 24)
			bit = 24;
		if (unlikely(bit >= (1ll << 32)))
			goto max_err_out;
		ntfs_debug("Found free record (#2), bit 0x%llx.",
				(long long)bit);
		goto found_free_rec;
	}
	/*
	 * The mft bitmap needs to be expanded until it covers the first unused
	 * mft record that we can allocate.
	 * Note: The smallest mft record we allocate is mft record 24.
	 */
	bit = old_data_initialized << 3;
	if (unlikely(bit >= (1ll << 32)))
		goto max_err_out;
	read_lock_irqsave(&mftbmp_ni->size_lock, flags);
	old_data_size = mftbmp_ni->allocated_size;
	ntfs_debug("Status of mftbmp before extension: allocated_size 0x%llx, "
			"data_size 0x%llx, initialized_size 0x%llx.",
			(long long)old_data_size,
			(long long)i_size_read(vol->mftbmp_ino),
			(long long)old_data_initialized);
	read_unlock_irqrestore(&mftbmp_ni->size_lock, flags);
	if (old_data_initialized + 8 > old_data_size) {
		/* Need to extend bitmap by one more cluster. */
		ntfs_debug("mftbmp: initialized_size + 8 > allocated_size.");
		err = ntfs_mft_bitmap_extend_allocation_nolock(vol);
		if (unlikely(err)) {
			up_write(&vol->mftbmp_lock);
			goto err_out;
		}
#ifdef DEBUG
		read_lock_irqsave(&mftbmp_ni->size_lock, flags);
		ntfs_debug("Status of mftbmp after allocation extension: "
				"allocated_size 0x%llx, data_size 0x%llx, "
				"initialized_size 0x%llx.",
				(long long)mftbmp_ni->allocated_size,
				(long long)i_size_read(vol->mftbmp_ino),
				(long long)mftbmp_ni->initialized_size);
		read_unlock_irqrestore(&mftbmp_ni->size_lock, flags);
#endif /* DEBUG */
	}
	/*
	 * We now have sufficient allocated space, extend the initialized_size
	 * as well as the data_size if necessary and fill the new space with
	 * zeroes.
	 */
	err = ntfs_mft_bitmap_extend_initialized_nolock(vol);
	if (unlikely(err)) {
		up_write(&vol->mftbmp_lock);
		goto err_out;
	}
#ifdef DEBUG
	read_lock_irqsave(&mftbmp_ni->size_lock, flags);
	ntfs_debug("Status of mftbmp after initialized extention: "
			"allocated_size 0x%llx, data_size 0x%llx, "
			"initialized_size 0x%llx.",
			(long long)mftbmp_ni->allocated_size,
			(long long)i_size_read(vol->mftbmp_ino),
			(long long)mftbmp_ni->initialized_size);
	read_unlock_irqrestore(&mftbmp_ni->size_lock, flags);
#endif /* DEBUG */
	ntfs_debug("Found free record (#3), bit 0x%llx.", (long long)bit);
found_free_rec:
	/* @bit is the found free mft record, allocate it in the mft bitmap. */
	ntfs_debug("At found_free_rec.");
	err = ntfs_bitmap_set_bit(vol->mftbmp_ino, bit);
	if (unlikely(err)) {
		ntfs_error(vol->sb, "Failed to allocate bit in mft bitmap.");
		up_write(&vol->mftbmp_lock);
		goto err_out;
	}
	ntfs_debug("Set bit 0x%llx in mft bitmap.", (long long)bit);
have_alloc_rec:
	/*
	 * The mft bitmap is now uptodate.  Deal with mft data attribute now.
	 * Note, we keep hold of the mft bitmap lock for writing until all
	 * modifications to the mft data attribute are complete, too, as they
	 * will impact decisions for mft bitmap and mft record allocation done
	 * by a parallel allocation and if the lock is not maintained a
	 * parallel allocation could allocate the same mft record as this one.
	 */
	ll = (bit + 1) << vol->mft_record_size_bits;
	read_lock_irqsave(&mft_ni->size_lock, flags);
	old_data_initialized = mft_ni->initialized_size;
	read_unlock_irqrestore(&mft_ni->size_lock, flags);
	if (ll <= old_data_initialized) {
		ntfs_debug("Allocated mft record already initialized.");
		goto mft_rec_already_initialized;
	}
	ntfs_debug("Initializing allocated mft record.");
	/*
	 * The mft record is outside the initialized data.  Extend the mft data
	 * attribute until it covers the allocated record.  The loop is only
	 * actually traversed more than once when a freshly formatted volume is
	 * first written to so it optimizes away nicely in the common case.
	 */
	read_lock_irqsave(&mft_ni->size_lock, flags);
	ntfs_debug("Status of mft data before extension: "
			"allocated_size 0x%llx, data_size 0x%llx, "
			"initialized_size 0x%llx.",
			(long long)mft_ni->allocated_size,
			(long long)i_size_read(vol->mft_ino),
			(long long)mft_ni->initialized_size);
	while (ll > mft_ni->allocated_size) {
		read_unlock_irqrestore(&mft_ni->size_lock, flags);
		err = ntfs_mft_data_extend_allocation_nolock(vol);
		if (unlikely(err)) {
			ntfs_error(vol->sb, "Failed to extend mft data "
					"allocation.");
			goto undo_mftbmp_alloc_nolock;
		}
		read_lock_irqsave(&mft_ni->size_lock, flags);
		ntfs_debug("Status of mft data after allocation extension: "
				"allocated_size 0x%llx, data_size 0x%llx, "
				"initialized_size 0x%llx.",
				(long long)mft_ni->allocated_size,
				(long long)i_size_read(vol->mft_ino),
				(long long)mft_ni->initialized_size);
	}
	read_unlock_irqrestore(&mft_ni->size_lock, flags);
	/*
	 * Extend mft data initialized size (and data size of course) to reach
	 * the allocated mft record, formatting the mft records allong the way.
	 * Note: We only modify the ntfs_inode structure as that is all that is
	 * needed by ntfs_mft_record_format().  We will update the attribute
	 * record itself in one fell swoop later on.
	 */
	write_lock_irqsave(&mft_ni->size_lock, flags);
	old_data_initialized = mft_ni->initialized_size;
	old_data_size = vol->mft_ino->i_size;
	while (ll > mft_ni->initialized_size) {
		s64 new_initialized_size, mft_no;
		
		new_initialized_size = mft_ni->initialized_size +
				vol->mft_record_size;
		mft_no = mft_ni->initialized_size >> vol->mft_record_size_bits;
		if (new_initialized_size > i_size_read(vol->mft_ino))
			i_size_write(vol->mft_ino, new_initialized_size);
		write_unlock_irqrestore(&mft_ni->size_lock, flags);
		ntfs_debug("Initializing mft record 0x%llx.",
				(long long)mft_no);
		err = ntfs_mft_record_format(vol, mft_no);
		if (unlikely(err)) {
			ntfs_error(vol->sb, "Failed to format mft record.");
			goto undo_data_init;
		}
		write_lock_irqsave(&mft_ni->size_lock, flags);
		mft_ni->initialized_size = new_initialized_size;
	}
	write_unlock_irqrestore(&mft_ni->size_lock, flags);
	record_formatted = true;
	/* Update the mft data attribute record to reflect the new sizes. */
	m = map_mft_record(mft_ni);
	if (IS_ERR(m)) {
		ntfs_error(vol->sb, "Failed to map mft record.");
		err = PTR_ERR(m);
		goto undo_data_init;
	}
	ctx = ntfs_attr_get_search_ctx(mft_ni, m);
	if (unlikely(!ctx)) {
		ntfs_error(vol->sb, "Failed to get search context.");
		err = -ENOMEM;
		unmap_mft_record(mft_ni);
		goto undo_data_init;
	}
	err = ntfs_attr_lookup(mft_ni->type, mft_ni->name, mft_ni->name_len,
			CASE_SENSITIVE, 0, NULL, 0, ctx);
	if (unlikely(err)) {
		ntfs_error(vol->sb, "Failed to find first attribute extent of "
				"mft data attribute.");
		ntfs_attr_put_search_ctx(ctx);
		unmap_mft_record(mft_ni);
		goto undo_data_init;
	}
	a = ctx->attr;
	read_lock_irqsave(&mft_ni->size_lock, flags);
	a->data.non_resident.initialized_size =
			cpu_to_sle64(mft_ni->initialized_size);
	a->data.non_resident.data_size =
			cpu_to_sle64(i_size_read(vol->mft_ino));
	read_unlock_irqrestore(&mft_ni->size_lock, flags);
	/* Ensure the changes make it to disk. */
	flush_dcache_mft_record_page(ctx->ntfs_ino);
	mark_mft_record_dirty(ctx->ntfs_ino);
	ntfs_attr_put_search_ctx(ctx);
	unmap_mft_record(mft_ni);
	read_lock_irqsave(&mft_ni->size_lock, flags);
	ntfs_debug("Status of mft data after mft record initialization: "
			"allocated_size 0x%llx, data_size 0x%llx, "
			"initialized_size 0x%llx.",
			(long long)mft_ni->allocated_size,
			(long long)i_size_read(vol->mft_ino),
			(long long)mft_ni->initialized_size);
	BUG_ON(i_size_read(vol->mft_ino) > mft_ni->allocated_size);
	BUG_ON(mft_ni->initialized_size > i_size_read(vol->mft_ino));
	read_unlock_irqrestore(&mft_ni->size_lock, flags);
mft_rec_already_initialized:
	/*
	 * We can finally drop the mft bitmap lock as the mft data attribute
	 * has been fully updated.  The only disparity left is that the
	 * allocated mft record still needs to be marked as in use to match the
	 * set bit in the mft bitmap but this is actually not a problem since
	 * this mft record is not referenced from anywhere yet and the fact
	 * that it is allocated in the mft bitmap means that no-one will try to
	 * allocate it either.
	 */
	up_write(&vol->mftbmp_lock);
	/*
	 * We now have allocated and initialized the mft record.  Calculate the
	 * index of and the offset within the page cache page the record is in.
	 */
	index = bit << vol->mft_record_size_bits >> PAGE_CACHE_SHIFT;
	ofs = (bit << vol->mft_record_size_bits) & ~PAGE_CACHE_MASK;
	/* Read, map, and pin the page containing the mft record. */
	page = ntfs_map_page(vol->mft_ino->i_mapping, index);
	if (IS_ERR(page)) {
		ntfs_error(vol->sb, "Failed to map page containing allocated "
				"mft record 0x%llx.", (long long)bit);
		err = PTR_ERR(page);
		goto undo_mftbmp_alloc;
	}
	lock_page(page);
	BUG_ON(!PageUptodate(page));
	ClearPageUptodate(page);
	m = (MFT_RECORD*)((u8*)page_address(page) + ofs);
	/* If we just formatted the mft record no need to do it again. */
	if (!record_formatted) {
		/* Sanity check that the mft record is really not in use. */
		if (ntfs_is_file_record(m->magic) &&
				(m->flags & MFT_RECORD_IN_USE)) {
			ntfs_error(vol->sb, "Mft record 0x%llx was marked "
					"free in mft bitmap but is marked "
					"used itself.  Corrupt filesystem.  "
					"Unmount and run chkdsk.",
					(long long)bit);
			err = -EIO;
			SetPageUptodate(page);
			unlock_page(page);
			ntfs_unmap_page(page);
			NVolSetErrors(vol);
			goto undo_mftbmp_alloc;
		}
		/*
		 * We need to (re-)format the mft record, preserving the
		 * sequence number if it is not zero as well as the update
		 * sequence number if it is not zero or -1 (0xffff).  This
		 * means we do not need to care whether or not something went
		 * wrong with the previous mft record.
		 */
		seq_no = m->sequence_number;
		usn = *(le16*)((u8*)m + le16_to_cpu(m->usa_ofs));
		err = ntfs_mft_record_layout(vol, bit, m);
		if (unlikely(err)) {
			ntfs_error(vol->sb, "Failed to layout allocated mft "
					"record 0x%llx.", (long long)bit);
			SetPageUptodate(page);
			unlock_page(page);
			ntfs_unmap_page(page);
			goto undo_mftbmp_alloc;
		}
		if (seq_no)
			m->sequence_number = seq_no;
		if (usn && le16_to_cpu(usn) != 0xffff)
			*(le16*)((u8*)m + le16_to_cpu(m->usa_ofs)) = usn;
	}
	/* Set the mft record itself in use. */
	m->flags |= MFT_RECORD_IN_USE;
	if (S_ISDIR(mode))
		m->flags |= MFT_RECORD_IS_DIRECTORY;
	flush_dcache_page(page);
	SetPageUptodate(page);
	if (base_ni) {
		MFT_RECORD *m_tmp;

		/*
		 * Setup the base mft record in the extent mft record.  This
		 * completes initialization of the allocated extent mft record
		 * and we can simply use it with map_extent_mft_record().
		 */
		m->base_mft_record = MK_LE_MREF(base_ni->mft_no,
				base_ni->seq_no);
		/*
		 * Allocate an extent inode structure for the new mft record,
		 * attach it to the base inode @base_ni and map, pin, and lock
		 * its, i.e. the allocated, mft record.
		 */
		m_tmp = map_extent_mft_record(base_ni, bit, &ni);
		if (IS_ERR(m_tmp)) {
			ntfs_error(vol->sb, "Failed to map allocated extent "
					"mft record 0x%llx.", (long long)bit);
			err = PTR_ERR(m_tmp);
			/* Set the mft record itself not in use. */
			m->flags &= cpu_to_le16(
					~le16_to_cpu(MFT_RECORD_IN_USE));
			flush_dcache_page(page);
			/* Make sure the mft record is written out to disk. */
			mark_ntfs_record_dirty(page, ofs);
			unlock_page(page);
			ntfs_unmap_page(page);
			goto undo_mftbmp_alloc;
		}
		BUG_ON(m != m_tmp);
		/*
		 * Make sure the allocated mft record is written out to disk.
		 * No need to set the inode dirty because the caller is going
		 * to do that anyway after finishing with the new extent mft
		 * record (e.g. at a minimum a new attribute will be added to
		 * the mft record.
		 */
		mark_ntfs_record_dirty(page, ofs);
		unlock_page(page);
		/*
		 * Need to unmap the page since map_extent_mft_record() mapped
		 * it as well so we have it mapped twice at the moment.
		 */
		ntfs_unmap_page(page);
	} else {
		/*
		 * Allocate a new VFS inode and set it up.  NOTE: @vi->i_nlink
		 * is set to 1 but the mft record->link_count is 0.  The caller
		 * needs to bear this in mind.
		 */
		vi = new_inode(vol->sb);
		if (unlikely(!vi)) {
			err = -ENOMEM;
			/* Set the mft record itself not in use. */
			m->flags &= cpu_to_le16(
					~le16_to_cpu(MFT_RECORD_IN_USE));
			flush_dcache_page(page);
			/* Make sure the mft record is written out to disk. */
			mark_ntfs_record_dirty(page, ofs);
			unlock_page(page);
			ntfs_unmap_page(page);
			goto undo_mftbmp_alloc;
		}
		vi->i_ino = bit;
		/*
		 * This is for checking whether an inode has changed w.r.t. a
		 * file so that the file can be updated if necessary (compare
		 * with f_version).
		 */
		vi->i_version = 1;

		/* The owner and group come from the ntfs volume. */
		vi->i_uid = vol->uid;
		vi->i_gid = vol->gid;

		/* Initialize the ntfs specific part of @vi. */
		ntfs_init_big_inode(vi);
		ni = NTFS_I(vi);
		/*
		 * Set the appropriate mode, attribute type, and name.  For
		 * directories, also setup the index values to the defaults.
		 */
		if (S_ISDIR(mode)) {
			vi->i_mode = S_IFDIR | S_IRWXUGO;
			vi->i_mode &= ~vol->dmask;

			NInoSetMstProtected(ni);
			ni->type = AT_INDEX_ALLOCATION;
			ni->name = I30;
			ni->name_len = 4;

			ni->itype.index.block_size = 4096;
			ni->itype.index.block_size_bits = ntfs_ffs(4096) - 1;
			ni->itype.index.collation_rule = COLLATION_FILE_NAME;
			if (vol->cluster_size <= ni->itype.index.block_size) {
				ni->itype.index.vcn_size = vol->cluster_size;
				ni->itype.index.vcn_size_bits =
						vol->cluster_size_bits;
			} else {
				ni->itype.index.vcn_size = vol->sector_size;
				ni->itype.index.vcn_size_bits =
						vol->sector_size_bits;
			}
		} else {
			vi->i_mode = S_IFREG | S_IRWXUGO;
			vi->i_mode &= ~vol->fmask;

			ni->type = AT_DATA;
			ni->name = NULL;
			ni->name_len = 0;
		}
		if (IS_RDONLY(vi))
			vi->i_mode &= ~S_IWUGO;

		/* Set the inode times to the current time. */
		vi->i_atime = vi->i_mtime = vi->i_ctime =
			current_fs_time(vi->i_sb);
		/*
		 * Set the file size to 0, the ntfs inode sizes are set to 0 by
		 * the call to ntfs_init_big_inode() below.
		 */
		vi->i_size = 0;
		vi->i_blocks = 0;

		/* Set the sequence number. */
		vi->i_generation = ni->seq_no = le16_to_cpu(m->sequence_number);
		/*
		 * Manually map, pin, and lock the mft record as we already
		 * have its page mapped and it is very easy to do.
		 */
		atomic_inc(&ni->count);
		mutex_lock(&ni->mrec_lock);
		ni->page = page;
		ni->page_ofs = ofs;
		/*
		 * Make sure the allocated mft record is written out to disk.
		 * NOTE: We do not set the ntfs inode dirty because this would
		 * fail in ntfs_write_inode() because the inode does not have a
		 * standard information attribute yet.  Also, there is no need
		 * to set the inode dirty because the caller is going to do
		 * that anyway after finishing with the new mft record (e.g. at
		 * a minimum some new attributes will be added to the mft
		 * record.
		 */
		mark_ntfs_record_dirty(page, ofs);
		unlock_page(page);

		/* Add the inode to the inode hash for the superblock. */
		insert_inode_hash(vi);

		/* Update the default mft allocation position. */
		vol->mft_data_pos = bit + 1;
	}
	/*
	 * Return the opened, allocated inode of the allocated mft record as
	 * well as the mapped, pinned, and locked mft record.
	 */
	ntfs_debug("Returning opened, allocated %sinode 0x%llx.",
			base_ni ? "extent " : "", (long long)bit);
	*mrec = m;
	return ni;
undo_data_init:
	write_lock_irqsave(&mft_ni->size_lock, flags);
	mft_ni->initialized_size = old_data_initialized;
	i_size_write(vol->mft_ino, old_data_size);
	write_unlock_irqrestore(&mft_ni->size_lock, flags);
	goto undo_mftbmp_alloc_nolock;
undo_mftbmp_alloc:
	down_write(&vol->mftbmp_lock);
undo_mftbmp_alloc_nolock:
	if (ntfs_bitmap_clear_bit(vol->mftbmp_ino, bit)) {
		ntfs_error(vol->sb, "Failed to clear bit in mft bitmap.%s", es);
		NVolSetErrors(vol);
	}
	up_write(&vol->mftbmp_lock);
err_out:
	return ERR_PTR(err);
max_err_out:
	ntfs_warning(vol->sb, "Cannot allocate mft record because the maximum "
			"number of inodes (2^32) has already been reached.");
	up_write(&vol->mftbmp_lock);
	return ERR_PTR(-ENOSPC);
}

/**
 * ntfs_extent_mft_record_free - free an extent mft record on an ntfs volume
 * @ni:		ntfs inode of the mapped extent mft record to free
 * @m:		mapped extent mft record of the ntfs inode @ni
 *
 * Free the mapped extent mft record @m of the extent ntfs inode @ni.
 *
 * Note that this function unmaps the mft record and closes and destroys @ni
 * internally and hence you cannot use either @ni nor @m any more after this
 * function returns success.
 *
 * On success return 0 and on error return -errno.  @ni and @m are still valid
 * in this case and have not been freed.
 *
 * For some errors an error message is displayed and the success code 0 is
 * returned and the volume is then left dirty on umount.  This makes sense in
 * case we could not rollback the changes that were already done since the
 * caller no longer wants to reference this mft record so it does not matter to
 * the caller if something is wrong with it as long as it is properly detached
 * from the base inode.
 */
int ntfs_extent_mft_record_free(ntfs_inode *ni, MFT_RECORD *m)
{
	unsigned long mft_no = ni->mft_no;
	ntfs_volume *vol = ni->vol;
	ntfs_inode *base_ni;
	ntfs_inode **extent_nis;
	int i, err;
	le16 old_seq_no;
	u16 seq_no;
	
	BUG_ON(NInoAttr(ni));
	BUG_ON(ni->nr_extents != -1);

	mutex_lock(&ni->extent_lock);
	base_ni = ni->ext.base_ntfs_ino;
	mutex_unlock(&ni->extent_lock);

	BUG_ON(base_ni->nr_extents <= 0);

	ntfs_debug("Entering for extent inode 0x%lx, base inode 0x%lx.\n",
			mft_no, base_ni->mft_no);

	mutex_lock(&base_ni->extent_lock);

	/* Make sure we are holding the only reference to the extent inode. */
	if (atomic_read(&ni->count) > 2) {
		ntfs_error(vol->sb, "Tried to free busy extent inode 0x%lx, "
				"not freeing.", base_ni->mft_no);
		mutex_unlock(&base_ni->extent_lock);
		return -EBUSY;
	}

	/* Dissociate the ntfs inode from the base inode. */
	extent_nis = base_ni->ext.extent_ntfs_inos;
	err = -ENOENT;
	for (i = 0; i < base_ni->nr_extents; i++) {
		if (ni != extent_nis[i])
			continue;
		extent_nis += i;
		base_ni->nr_extents--;
		memmove(extent_nis, extent_nis + 1, (base_ni->nr_extents - i) *
				sizeof(ntfs_inode*));
		err = 0;
		break;
	}

	mutex_unlock(&base_ni->extent_lock);

	if (unlikely(err)) {
		ntfs_error(vol->sb, "Extent inode 0x%lx is not attached to "
				"its base inode 0x%lx.", mft_no,
				base_ni->mft_no);
		BUG();
	}

	/*
	 * The extent inode is no longer attached to the base inode so no one
	 * can get a reference to it any more.
	 */

	/* Mark the mft record as not in use. */
	m->flags &= ~MFT_RECORD_IN_USE;

	/* Increment the sequence number, skipping zero, if it is not zero. */
	old_seq_no = m->sequence_number;
	seq_no = le16_to_cpu(old_seq_no);
	if (seq_no == 0xffff)
		seq_no = 1;
	else if (seq_no)
		seq_no++;
	m->sequence_number = cpu_to_le16(seq_no);

	/*
	 * Set the ntfs inode dirty and write it out.  We do not need to worry
	 * about the base inode here since whatever caused the extent mft
	 * record to be freed is guaranteed to do it already.
	 */
	NInoSetDirty(ni);
	err = write_mft_record(ni, m, 0);
	if (unlikely(err)) {
		ntfs_error(vol->sb, "Failed to write mft record 0x%lx, not "
				"freeing.", mft_no);
		goto rollback;
	}
rollback_error:
	/* Unmap and throw away the now freed extent inode. */
	unmap_extent_mft_record(ni);
	ntfs_clear_extent_inode(ni);

	/* Clear the bit in the $MFT/$BITMAP corresponding to this record. */
	down_write(&vol->mftbmp_lock);
	err = ntfs_bitmap_clear_bit(vol->mftbmp_ino, mft_no);
	up_write(&vol->mftbmp_lock);
	if (unlikely(err)) {
		/*
		 * The extent inode is gone but we failed to deallocate it in
		 * the mft bitmap.  Just emit a warning and leave the volume
		 * dirty on umount.
		 */
		ntfs_error(vol->sb, "Failed to clear bit in mft bitmap.%s", es);
		NVolSetErrors(vol);
	}
	return 0;
rollback:
	/* Rollback what we did... */
	mutex_lock(&base_ni->extent_lock);
	extent_nis = base_ni->ext.extent_ntfs_inos;
	if (!(base_ni->nr_extents & 3)) {
		int new_size = (base_ni->nr_extents + 4) * sizeof(ntfs_inode*);

		extent_nis = kmalloc(new_size, GFP_NOFS);
		if (unlikely(!extent_nis)) {
			ntfs_error(vol->sb, "Failed to allocate internal "
					"buffer during rollback.%s", es);
			mutex_unlock(&base_ni->extent_lock);
			NVolSetErrors(vol);
			goto rollback_error;
		}
		if (base_ni->nr_extents) {
			BUG_ON(!base_ni->ext.extent_ntfs_inos);
			memcpy(extent_nis, base_ni->ext.extent_ntfs_inos,
					new_size - 4 * sizeof(ntfs_inode*));
			kfree(base_ni->ext.extent_ntfs_inos);
		}
		base_ni->ext.extent_ntfs_inos = extent_nis;
	}
	m->flags |= MFT_RECORD_IN_USE;
	m->sequence_number = old_seq_no;
	extent_nis[base_ni->nr_extents++] = ni;
	mutex_unlock(&base_ni->extent_lock);
	mark_mft_record_dirty(ni);
	return err;
}
#endif /* NTFS_RW */