summaryrefslogtreecommitdiff
path: root/fs/ntfs/file.c
blob: b6fa457d8d01ff3b925de46164edbbcdf8e00d2a (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
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
/*
 * file.c - NTFS kernel file operations.  Part of the Linux-NTFS project.
 *
 * Copyright (c) 2001-2011 Anton Altaparmakov and Tuxera Inc.
 *
 * 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/gfp.h>
#include <linux/pagemap.h>
#include <linux/pagevec.h>
#include <linux/sched.h>
#include <linux/swap.h>
#include <linux/uio.h>
#include <linux/writeback.h>
#include <linux/aio.h>

#include <asm/page.h>
#include <asm/uaccess.h>

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

/**
 * ntfs_file_open - called when an inode is about to be opened
 * @vi:		inode to be opened
 * @filp:	file structure describing the inode
 *
 * Limit file size to the page cache limit on architectures where unsigned long
 * is 32-bits. This is the most we can do for now without overflowing the page
 * cache page index. Doing it this way means we don't run into problems because
 * of existing too large files. It would be better to allow the user to read
 * the beginning of the file but I doubt very much anyone is going to hit this
 * check on a 32-bit architecture, so there is no point in adding the extra
 * complexity required to support this.
 *
 * On 64-bit architectures, the check is hopefully optimized away by the
 * compiler.
 *
 * After the check passes, just call generic_file_open() to do its work.
 */
static int ntfs_file_open(struct inode *vi, struct file *filp)
{
	if (sizeof(unsigned long) < 8) {
		if (i_size_read(vi) > MAX_LFS_FILESIZE)
			return -EOVERFLOW;
	}
	return generic_file_open(vi, filp);
}

#ifdef NTFS_RW

/**
 * ntfs_attr_extend_initialized - extend the initialized size of an attribute
 * @ni:			ntfs inode of the attribute to extend
 * @new_init_size:	requested new initialized size in bytes
 * @cached_page:	store any allocated but unused page here
 * @lru_pvec:		lru-buffering pagevec of the caller
 *
 * Extend the initialized size of an attribute described by the ntfs inode @ni
 * to @new_init_size bytes.  This involves zeroing any non-sparse space between
 * the old initialized size and @new_init_size both in the page cache and on
 * disk (if relevant complete pages are already uptodate in the page cache then
 * these are simply marked dirty).
 *
 * As a side-effect, the file size (vfs inode->i_size) may be incremented as,
 * in the resident attribute case, it is tied to the initialized size and, in
 * the non-resident attribute case, it may not fall below the initialized size.
 *
 * Note that if the attribute is resident, we do not need to touch the page
 * cache at all.  This is because if the page cache page is not uptodate we
 * bring it uptodate later, when doing the write to the mft record since we
 * then already have the page mapped.  And if the page is uptodate, the
 * non-initialized region will already have been zeroed when the page was
 * brought uptodate and the region may in fact already have been overwritten
 * with new data via mmap() based writes, so we cannot just zero it.  And since
 * POSIX specifies that the behaviour of resizing a file whilst it is mmap()ped
 * is unspecified, we choose not to do zeroing and thus we do not need to touch
 * the page at all.  For a more detailed explanation see ntfs_truncate() in
 * fs/ntfs/inode.c.
 *
 * Return 0 on success and -errno on error.  In the case that an error is
 * encountered it is possible that the initialized size will already have been
 * incremented some way towards @new_init_size but it is guaranteed that if
 * this is the case, the necessary zeroing will also have happened and that all
 * metadata is self-consistent.
 *
 * Locking: i_mutex on the vfs inode corrseponsind to the ntfs inode @ni must be
 *	    held by the caller.
 */
static int ntfs_attr_extend_initialized(ntfs_inode *ni, const s64 new_init_size)
{
	s64 old_init_size;
	loff_t old_i_size;
	pgoff_t index, end_index;
	unsigned long flags;
	struct inode *vi = VFS_I(ni);
	ntfs_inode *base_ni;
	MFT_RECORD *m = NULL;
	ATTR_RECORD *a;
	ntfs_attr_search_ctx *ctx = NULL;
	struct address_space *mapping;
	struct page *page = NULL;
	u8 *kattr;
	int err;
	u32 attr_len;

	read_lock_irqsave(&ni->size_lock, flags);
	old_init_size = ni->initialized_size;
	old_i_size = i_size_read(vi);
	BUG_ON(new_init_size > ni->allocated_size);
	read_unlock_irqrestore(&ni->size_lock, flags);
	ntfs_debug("Entering for i_ino 0x%lx, attribute type 0x%x, "
			"old_initialized_size 0x%llx, "
			"new_initialized_size 0x%llx, i_size 0x%llx.",
			vi->i_ino, (unsigned)le32_to_cpu(ni->type),
			(unsigned long long)old_init_size,
			(unsigned long long)new_init_size, old_i_size);
	if (!NInoAttr(ni))
		base_ni = ni;
	else
		base_ni = ni->ext.base_ntfs_ino;
	/* Use goto to reduce indentation and we need the label below anyway. */
	if (NInoNonResident(ni))
		goto do_non_resident_extend;
	BUG_ON(old_init_size != old_i_size);
	m = map_mft_record(base_ni);
	if (IS_ERR(m)) {
		err = PTR_ERR(m);
		m = NULL;
		goto err_out;
	}
	ctx = ntfs_attr_get_search_ctx(base_ni, m);
	if (unlikely(!ctx)) {
		err = -ENOMEM;
		goto err_out;
	}
	err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
			CASE_SENSITIVE, 0, NULL, 0, ctx);
	if (unlikely(err)) {
		if (err == -ENOENT)
			err = -EIO;
		goto err_out;
	}
	m = ctx->mrec;
	a = ctx->attr;
	BUG_ON(a->non_resident);
	/* The total length of the attribute value. */
	attr_len = le32_to_cpu(a->data.resident.value_length);
	BUG_ON(old_i_size != (loff_t)attr_len);
	/*
	 * Do the zeroing in the mft record and update the attribute size in
	 * the mft record.
	 */
	kattr = (u8*)a + le16_to_cpu(a->data.resident.value_offset);
	memset(kattr + attr_len, 0, new_init_size - attr_len);
	a->data.resident.value_length = cpu_to_le32((u32)new_init_size);
	/* Finally, update the sizes in the vfs and ntfs inodes. */
	write_lock_irqsave(&ni->size_lock, flags);
	i_size_write(vi, new_init_size);
	ni->initialized_size = new_init_size;
	write_unlock_irqrestore(&ni->size_lock, flags);
	goto done;
do_non_resident_extend:
	/*
	 * If the new initialized size @new_init_size exceeds the current file
	 * size (vfs inode->i_size), we need to extend the file size to the
	 * new initialized size.
	 */
	if (new_init_size > old_i_size) {
		m = map_mft_record(base_ni);
		if (IS_ERR(m)) {
			err = PTR_ERR(m);
			m = NULL;
			goto err_out;
		}
		ctx = ntfs_attr_get_search_ctx(base_ni, m);
		if (unlikely(!ctx)) {
			err = -ENOMEM;
			goto err_out;
		}
		err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
				CASE_SENSITIVE, 0, NULL, 0, ctx);
		if (unlikely(err)) {
			if (err == -ENOENT)
				err = -EIO;
			goto err_out;
		}
		m = ctx->mrec;
		a = ctx->attr;
		BUG_ON(!a->non_resident);
		BUG_ON(old_i_size != (loff_t)
				sle64_to_cpu(a->data.non_resident.data_size));
		a->data.non_resident.data_size = cpu_to_sle64(new_init_size);
		flush_dcache_mft_record_page(ctx->ntfs_ino);
		mark_mft_record_dirty(ctx->ntfs_ino);
		/* Update the file size in the vfs inode. */
		i_size_write(vi, new_init_size);
		ntfs_attr_put_search_ctx(ctx);
		ctx = NULL;
		unmap_mft_record(base_ni);
		m = NULL;
	}
	mapping = vi->i_mapping;
	index = old_init_size >> PAGE_CACHE_SHIFT;
	end_index = (new_init_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
	do {
		/*
		 * Read the page.  If the page is not present, this will zero
		 * the uninitialized regions for us.
		 */
		page = read_mapping_page(mapping, index, NULL);
		if (IS_ERR(page)) {
			err = PTR_ERR(page);
			goto init_err_out;
		}
		if (unlikely(PageError(page))) {
			page_cache_release(page);
			err = -EIO;
			goto init_err_out;
		}
		/*
		 * Update the initialized size in the ntfs inode.  This is
		 * enough to make ntfs_writepage() work.
		 */
		write_lock_irqsave(&ni->size_lock, flags);
		ni->initialized_size = (s64)(index + 1) << PAGE_CACHE_SHIFT;
		if (ni->initialized_size > new_init_size)
			ni->initialized_size = new_init_size;
		write_unlock_irqrestore(&ni->size_lock, flags);
		/* Set the page dirty so it gets written out. */
		set_page_dirty(page);
		page_cache_release(page);
		/*
		 * Play nice with the vm and the rest of the system.  This is
		 * very much needed as we can potentially be modifying the
		 * initialised size from a very small value to a really huge
		 * value, e.g.
		 *	f = open(somefile, O_TRUNC);
		 *	truncate(f, 10GiB);
		 *	seek(f, 10GiB);
		 *	write(f, 1);
		 * And this would mean we would be marking dirty hundreds of
		 * thousands of pages or as in the above example more than
		 * two and a half million pages!
		 *
		 * TODO: For sparse pages could optimize this workload by using
		 * the FsMisc / MiscFs page bit as a "PageIsSparse" bit.  This
		 * would be set in readpage for sparse pages and here we would
		 * not need to mark dirty any pages which have this bit set.
		 * The only caveat is that we have to clear the bit everywhere
		 * where we allocate any clusters that lie in the page or that
		 * contain the page.
		 *
		 * TODO: An even greater optimization would be for us to only
		 * call readpage() on pages which are not in sparse regions as
		 * determined from the runlist.  This would greatly reduce the
		 * number of pages we read and make dirty in the case of sparse
		 * files.
		 */
		balance_dirty_pages_ratelimited(mapping);
		cond_resched();
	} while (++index < end_index);
	read_lock_irqsave(&ni->size_lock, flags);
	BUG_ON(ni->initialized_size != new_init_size);
	read_unlock_irqrestore(&ni->size_lock, flags);
	/* Now bring in sync the initialized_size in the mft record. */
	m = map_mft_record(base_ni);
	if (IS_ERR(m)) {
		err = PTR_ERR(m);
		m = NULL;
		goto init_err_out;
	}
	ctx = ntfs_attr_get_search_ctx(base_ni, m);
	if (unlikely(!ctx)) {
		err = -ENOMEM;
		goto init_err_out;
	}
	err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
			CASE_SENSITIVE, 0, NULL, 0, ctx);
	if (unlikely(err)) {
		if (err == -ENOENT)
			err = -EIO;
		goto init_err_out;
	}
	m = ctx->mrec;
	a = ctx->attr;
	BUG_ON(!a->non_resident);
	a->data.non_resident.initialized_size = cpu_to_sle64(new_init_size);
done:
	flush_dcache_mft_record_page(ctx->ntfs_ino);
	mark_mft_record_dirty(ctx->ntfs_ino);
	if (ctx)
		ntfs_attr_put_search_ctx(ctx);
	if (m)
		unmap_mft_record(base_ni);
	ntfs_debug("Done, initialized_size 0x%llx, i_size 0x%llx.",
			(unsigned long long)new_init_size, i_size_read(vi));
	return 0;
init_err_out:
	write_lock_irqsave(&ni->size_lock, flags);
	ni->initialized_size = old_init_size;
	write_unlock_irqrestore(&ni->size_lock, flags);
err_out:
	if (ctx)
		ntfs_attr_put_search_ctx(ctx);
	if (m)
		unmap_mft_record(base_ni);
	ntfs_debug("Failed.  Returning error code %i.", err);
	return err;
}

/**
 * ntfs_fault_in_pages_readable -
 *
 * Fault a number of userspace pages into pagetables.
 *
 * Unlike include/linux/pagemap.h::fault_in_pages_readable(), this one copes
 * with more than two userspace pages as well as handling the single page case
 * elegantly.
 *
 * If you find this difficult to understand, then think of the while loop being
 * the following code, except that we do without the integer variable ret:
 *
 *	do {
 *		ret = __get_user(c, uaddr);
 *		uaddr += PAGE_SIZE;
 *	} while (!ret && uaddr < end);
 *
 * Note, the final __get_user() may well run out-of-bounds of the user buffer,
 * but _not_ out-of-bounds of the page the user buffer belongs to, and since
 * this is only a read and not a write, and since it is still in the same page,
 * it should not matter and this makes the code much simpler.
 */
static inline void ntfs_fault_in_pages_readable(const char __user *uaddr,
		int bytes)
{
	const char __user *end;
	volatile char c;

	/* Set @end to the first byte outside the last page we care about. */
	end = (const char __user*)PAGE_ALIGN((unsigned long)uaddr + bytes);

	while (!__get_user(c, uaddr) && (uaddr += PAGE_SIZE, uaddr < end))
		;
}

/**
 * ntfs_fault_in_pages_readable_iovec -
 *
 * Same as ntfs_fault_in_pages_readable() but operates on an array of iovecs.
 */
static inline void ntfs_fault_in_pages_readable_iovec(const struct iovec *iov,
		size_t iov_ofs, int bytes)
{
	do {
		const char __user *buf;
		unsigned len;

		buf = iov->iov_base + iov_ofs;
		len = iov->iov_len - iov_ofs;
		if (len > bytes)
			len = bytes;
		ntfs_fault_in_pages_readable(buf, len);
		bytes -= len;
		iov++;
		iov_ofs = 0;
	} while (bytes);
}

/**
 * __ntfs_grab_cache_pages - obtain a number of locked pages
 * @mapping:	address space mapping from which to obtain page cache pages
 * @index:	starting index in @mapping at which to begin obtaining pages
 * @nr_pages:	number of page cache pages to obtain
 * @pages:	array of pages in which to return the obtained page cache pages
 * @cached_page: allocated but as yet unused page
 * @lru_pvec:	lru-buffering pagevec of caller
 *
 * Obtain @nr_pages locked page cache pages from the mapping @mapping and
 * starting at index @index.
 *
 * If a page is newly created, add it to lru list
 *
 * Note, the page locks are obtained in ascending page index order.
 */
static inline int __ntfs_grab_cache_pages(struct address_space *mapping,
		pgoff_t index, const unsigned nr_pages, struct page **pages,
		struct page **cached_page)
{
	int err, nr;

	BUG_ON(!nr_pages);
	err = nr = 0;
	do {
		pages[nr] = find_lock_page(mapping, index);
		if (!pages[nr]) {
			if (!*cached_page) {
				*cached_page = page_cache_alloc(mapping);
				if (unlikely(!*cached_page)) {
					err = -ENOMEM;
					goto err_out;
				}
			}
			err = add_to_page_cache_lru(*cached_page, mapping, index,
					GFP_KERNEL);
			if (unlikely(err)) {
				if (err == -EEXIST)
					continue;
				goto err_out;
			}
			pages[nr] = *cached_page;
			*cached_page = NULL;
		}
		index++;
		nr++;
	} while (nr < nr_pages);
out:
	return err;
err_out:
	while (nr > 0) {
		unlock_page(pages[--nr]);
		page_cache_release(pages[nr]);
	}
	goto out;
}

static inline int ntfs_submit_bh_for_read(struct buffer_head *bh)
{
	lock_buffer(bh);
	get_bh(bh);
	bh->b_end_io = end_buffer_read_sync;
	return submit_bh(READ, bh);
}

/**
 * ntfs_prepare_pages_for_non_resident_write - prepare pages for receiving data
 * @pages:	array of destination pages
 * @nr_pages:	number of pages in @pages
 * @pos:	byte position in file at which the write begins
 * @bytes:	number of bytes to be written
 *
 * This is called for non-resident attributes from ntfs_file_buffered_write()
 * with i_mutex held on the inode (@pages[0]->mapping->host).  There are
 * @nr_pages pages in @pages which are locked but not kmap()ped.  The source
 * data has not yet been copied into the @pages.
 * 
 * Need to fill any holes with actual clusters, allocate buffers if necessary,
 * ensure all the buffers are mapped, and bring uptodate any buffers that are
 * only partially being written to.
 *
 * If @nr_pages is greater than one, we are guaranteed that the cluster size is
 * greater than PAGE_CACHE_SIZE, that all pages in @pages are entirely inside
 * the same cluster and that they are the entirety of that cluster, and that
 * the cluster is sparse, i.e. we need to allocate a cluster to fill the hole.
 *
 * i_size is not to be modified yet.
 *
 * Return 0 on success or -errno on error.
 */
static int ntfs_prepare_pages_for_non_resident_write(struct page **pages,
		unsigned nr_pages, s64 pos, size_t bytes)
{
	VCN vcn, highest_vcn = 0, cpos, cend, bh_cpos, bh_cend;
	LCN lcn;
	s64 bh_pos, vcn_len, end, initialized_size;
	sector_t lcn_block;
	struct page *page;
	struct inode *vi;
	ntfs_inode *ni, *base_ni = NULL;
	ntfs_volume *vol;
	runlist_element *rl, *rl2;
	struct buffer_head *bh, *head, *wait[2], **wait_bh = wait;
	ntfs_attr_search_ctx *ctx = NULL;
	MFT_RECORD *m = NULL;
	ATTR_RECORD *a = NULL;
	unsigned long flags;
	u32 attr_rec_len = 0;
	unsigned blocksize, u;
	int err, mp_size;
	bool rl_write_locked, was_hole, is_retry;
	unsigned char blocksize_bits;
	struct {
		u8 runlist_merged:1;
		u8 mft_attr_mapped:1;
		u8 mp_rebuilt:1;
		u8 attr_switched:1;
	} status = { 0, 0, 0, 0 };

	BUG_ON(!nr_pages);
	BUG_ON(!pages);
	BUG_ON(!*pages);
	vi = pages[0]->mapping->host;
	ni = NTFS_I(vi);
	vol = ni->vol;
	ntfs_debug("Entering for inode 0x%lx, attribute type 0x%x, start page "
			"index 0x%lx, nr_pages 0x%x, pos 0x%llx, bytes 0x%zx.",
			vi->i_ino, ni->type, pages[0]->index, nr_pages,
			(long long)pos, bytes);
	blocksize = vol->sb->s_blocksize;
	blocksize_bits = vol->sb->s_blocksize_bits;
	u = 0;
	do {
		page = pages[u];
		BUG_ON(!page);
		/*
		 * create_empty_buffers() will create uptodate/dirty buffers if
		 * the page is uptodate/dirty.
		 */
		if (!page_has_buffers(page)) {
			create_empty_buffers(page, blocksize, 0);
			if (unlikely(!page_has_buffers(page)))
				return -ENOMEM;
		}
	} while (++u < nr_pages);
	rl_write_locked = false;
	rl = NULL;
	err = 0;
	vcn = lcn = -1;
	vcn_len = 0;
	lcn_block = -1;
	was_hole = false;
	cpos = pos >> vol->cluster_size_bits;
	end = pos + bytes;
	cend = (end + vol->cluster_size - 1) >> vol->cluster_size_bits;
	/*
	 * Loop over each page and for each page over each buffer.  Use goto to
	 * reduce indentation.
	 */
	u = 0;
do_next_page:
	page = pages[u];
	bh_pos = (s64)page->index << PAGE_CACHE_SHIFT;
	bh = head = page_buffers(page);
	do {
		VCN cdelta;
		s64 bh_end;
		unsigned bh_cofs;

		/* Clear buffer_new on all buffers to reinitialise state. */
		if (buffer_new(bh))
			clear_buffer_new(bh);
		bh_end = bh_pos + blocksize;
		bh_cpos = bh_pos >> vol->cluster_size_bits;
		bh_cofs = bh_pos & vol->cluster_size_mask;
		if (buffer_mapped(bh)) {
			/*
			 * The buffer is already mapped.  If it is uptodate,
			 * ignore it.
			 */
			if (buffer_uptodate(bh))
				continue;
			/*
			 * The buffer is not uptodate.  If the page is uptodate
			 * set the buffer uptodate and otherwise ignore it.
			 */
			if (PageUptodate(page)) {
				set_buffer_uptodate(bh);
				continue;
			}
			/*
			 * Neither the page nor the buffer are uptodate.  If
			 * the buffer is only partially being written to, we
			 * need to read it in before the write, i.e. now.
			 */
			if ((bh_pos < pos && bh_end > pos) ||
					(bh_pos < end && bh_end > end)) {
				/*
				 * If the buffer is fully or partially within
				 * the initialized size, do an actual read.
				 * Otherwise, simply zero the buffer.
				 */
				read_lock_irqsave(&ni->size_lock, flags);
				initialized_size = ni->initialized_size;
				read_unlock_irqrestore(&ni->size_lock, flags);
				if (bh_pos < initialized_size) {
					ntfs_submit_bh_for_read(bh);
					*wait_bh++ = bh;
				} else {
					zero_user(page, bh_offset(bh),
							blocksize);
					set_buffer_uptodate(bh);
				}
			}
			continue;
		}
		/* Unmapped buffer.  Need to map it. */
		bh->b_bdev = vol->sb->s_bdev;
		/*
		 * If the current buffer is in the same clusters as the map
		 * cache, there is no need to check the runlist again.  The
		 * map cache is made up of @vcn, which is the first cached file
		 * cluster, @vcn_len which is the number of cached file
		 * clusters, @lcn is the device cluster corresponding to @vcn,
		 * and @lcn_block is the block number corresponding to @lcn.
		 */
		cdelta = bh_cpos - vcn;
		if (likely(!cdelta || (cdelta > 0 && cdelta < vcn_len))) {
map_buffer_cached:
			BUG_ON(lcn < 0);
			bh->b_blocknr = lcn_block +
					(cdelta << (vol->cluster_size_bits -
					blocksize_bits)) +
					(bh_cofs >> blocksize_bits);
			set_buffer_mapped(bh);
			/*
			 * If the page is uptodate so is the buffer.  If the
			 * buffer is fully outside the write, we ignore it if
			 * it was already allocated and we mark it dirty so it
			 * gets written out if we allocated it.  On the other
			 * hand, if we allocated the buffer but we are not
			 * marking it dirty we set buffer_new so we can do
			 * error recovery.
			 */
			if (PageUptodate(page)) {
				if (!buffer_uptodate(bh))
					set_buffer_uptodate(bh);
				if (unlikely(was_hole)) {
					/* We allocated the buffer. */
					unmap_underlying_metadata(bh->b_bdev,
							bh->b_blocknr);
					if (bh_end <= pos || bh_pos >= end)
						mark_buffer_dirty(bh);
					else
						set_buffer_new(bh);
				}
				continue;
			}
			/* Page is _not_ uptodate. */
			if (likely(!was_hole)) {
				/*
				 * Buffer was already allocated.  If it is not
				 * uptodate and is only partially being written
				 * to, we need to read it in before the write,
				 * i.e. now.
				 */
				if (!buffer_uptodate(bh) && bh_pos < end &&
						bh_end > pos &&
						(bh_pos < pos ||
						bh_end > end)) {
					/*
					 * If the buffer is fully or partially
					 * within the initialized size, do an
					 * actual read.  Otherwise, simply zero
					 * the buffer.
					 */
					read_lock_irqsave(&ni->size_lock,
							flags);
					initialized_size = ni->initialized_size;
					read_unlock_irqrestore(&ni->size_lock,
							flags);
					if (bh_pos < initialized_size) {
						ntfs_submit_bh_for_read(bh);
						*wait_bh++ = bh;
					} else {
						zero_user(page, bh_offset(bh),
								blocksize);
						set_buffer_uptodate(bh);
					}
				}
				continue;
			}
			/* We allocated the buffer. */
			unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
			/*
			 * If the buffer is fully outside the write, zero it,
			 * set it uptodate, and mark it dirty so it gets
			 * written out.  If it is partially being written to,
			 * zero region surrounding the write but leave it to
			 * commit write to do anything else.  Finally, if the
			 * buffer is fully being overwritten, do nothing.
			 */
			if (bh_end <= pos || bh_pos >= end) {
				if (!buffer_uptodate(bh)) {
					zero_user(page, bh_offset(bh),
							blocksize);
					set_buffer_uptodate(bh);
				}
				mark_buffer_dirty(bh);
				continue;
			}
			set_buffer_new(bh);
			if (!buffer_uptodate(bh) &&
					(bh_pos < pos || bh_end > end)) {
				u8 *kaddr;
				unsigned pofs;
					
				kaddr = kmap_atomic(page);
				if (bh_pos < pos) {
					pofs = bh_pos & ~PAGE_CACHE_MASK;
					memset(kaddr + pofs, 0, pos - bh_pos);
				}
				if (bh_end > end) {
					pofs = end & ~PAGE_CACHE_MASK;
					memset(kaddr + pofs, 0, bh_end - end);
				}
				kunmap_atomic(kaddr);
				flush_dcache_page(page);
			}
			continue;
		}
		/*
		 * Slow path: this is the first buffer in the cluster.  If it
		 * is outside allocated size and is not uptodate, zero it and
		 * set it uptodate.
		 */
		read_lock_irqsave(&ni->size_lock, flags);
		initialized_size = ni->allocated_size;
		read_unlock_irqrestore(&ni->size_lock, flags);
		if (bh_pos > initialized_size) {
			if (PageUptodate(page)) {
				if (!buffer_uptodate(bh))
					set_buffer_uptodate(bh);
			} else if (!buffer_uptodate(bh)) {
				zero_user(page, bh_offset(bh), blocksize);
				set_buffer_uptodate(bh);
			}
			continue;
		}
		is_retry = false;
		if (!rl) {
			down_read(&ni->runlist.lock);
retry_remap:
			rl = ni->runlist.rl;
		}
		if (likely(rl != NULL)) {
			/* Seek to element containing target cluster. */
			while (rl->length && rl[1].vcn <= bh_cpos)
				rl++;
			lcn = ntfs_rl_vcn_to_lcn(rl, bh_cpos);
			if (likely(lcn >= 0)) {
				/*
				 * Successful remap, setup the map cache and
				 * use that to deal with the buffer.
				 */
				was_hole = false;
				vcn = bh_cpos;
				vcn_len = rl[1].vcn - vcn;
				lcn_block = lcn << (vol->cluster_size_bits -
						blocksize_bits);
				cdelta = 0;
				/*
				 * If the number of remaining clusters touched
				 * by the write is smaller or equal to the
				 * number of cached clusters, unlock the
				 * runlist as the map cache will be used from
				 * now on.
				 */
				if (likely(vcn + vcn_len >= cend)) {
					if (rl_write_locked) {
						up_write(&ni->runlist.lock);
						rl_write_locked = false;
					} else
						up_read(&ni->runlist.lock);
					rl = NULL;
				}
				goto map_buffer_cached;
			}
		} else
			lcn = LCN_RL_NOT_MAPPED;
		/*
		 * If it is not a hole and not out of bounds, the runlist is
		 * probably unmapped so try to map it now.
		 */
		if (unlikely(lcn != LCN_HOLE && lcn != LCN_ENOENT)) {
			if (likely(!is_retry && lcn == LCN_RL_NOT_MAPPED)) {
				/* Attempt to map runlist. */
				if (!rl_write_locked) {
					/*
					 * We need the runlist locked for
					 * writing, so if it is locked for
					 * reading relock it now and retry in
					 * case it changed whilst we dropped
					 * the lock.
					 */
					up_read(&ni->runlist.lock);
					down_write(&ni->runlist.lock);
					rl_write_locked = true;
					goto retry_remap;
				}
				err = ntfs_map_runlist_nolock(ni, bh_cpos,
						NULL);
				if (likely(!err)) {
					is_retry = true;
					goto retry_remap;
				}
				/*
				 * If @vcn is out of bounds, pretend @lcn is
				 * LCN_ENOENT.  As long as the buffer is out
				 * of bounds this will work fine.
				 */
				if (err == -ENOENT) {
					lcn = LCN_ENOENT;
					err = 0;
					goto rl_not_mapped_enoent;
				}
			} else
				err = -EIO;
			/* Failed to map the buffer, even after retrying. */
			bh->b_blocknr = -1;
			ntfs_error(vol->sb, "Failed to write to inode 0x%lx, "
					"attribute type 0x%x, vcn 0x%llx, "
					"vcn offset 0x%x, because its "
					"location on disk could not be "
					"determined%s (error code %i).",
					ni->mft_no, ni->type,
					(unsigned long long)bh_cpos,
					(unsigned)bh_pos &
					vol->cluster_size_mask,
					is_retry ? " even after retrying" : "",
					err);
			break;
		}
rl_not_mapped_enoent:
		/*
		 * The buffer is in a hole or out of bounds.  We need to fill
		 * the hole, unless the buffer is in a cluster which is not
		 * touched by the write, in which case we just leave the buffer
		 * unmapped.  This can only happen when the cluster size is
		 * less than the page cache size.
		 */
		if (unlikely(vol->cluster_size < PAGE_CACHE_SIZE)) {
			bh_cend = (bh_end + vol->cluster_size - 1) >>
					vol->cluster_size_bits;
			if ((bh_cend <= cpos || bh_cpos >= cend)) {
				bh->b_blocknr = -1;
				/*
				 * If the buffer is uptodate we skip it.  If it
				 * is not but the page is uptodate, we can set
				 * the buffer uptodate.  If the page is not
				 * uptodate, we can clear the buffer and set it
				 * uptodate.  Whether this is worthwhile is
				 * debatable and this could be removed.
				 */
				if (PageUptodate(page)) {
					if (!buffer_uptodate(bh))
						set_buffer_uptodate(bh);
				} else if (!buffer_uptodate(bh)) {
					zero_user(page, bh_offset(bh),
						blocksize);
					set_buffer_uptodate(bh);
				}
				continue;
			}
		}
		/*
		 * Out of bounds buffer is invalid if it was not really out of
		 * bounds.
		 */
		BUG_ON(lcn != LCN_HOLE);
		/*
		 * We need the runlist locked for writing, so if it is locked
		 * for reading relock it now and retry in case it changed
		 * whilst we dropped the lock.
		 */
		BUG_ON(!rl);
		if (!rl_write_locked) {
			up_read(&ni->runlist.lock);
			down_write(&ni->runlist.lock);
			rl_write_locked = true;
			goto retry_remap;
		}
		/* Find the previous last allocated cluster. */
		BUG_ON(rl->lcn != LCN_HOLE);
		lcn = -1;
		rl2 = rl;
		while (--rl2 >= ni->runlist.rl) {
			if (rl2->lcn >= 0) {
				lcn = rl2->lcn + rl2->length;
				break;
			}
		}
		rl2 = ntfs_cluster_alloc(vol, bh_cpos, 1, lcn, DATA_ZONE,
				false);
		if (IS_ERR(rl2)) {
			err = PTR_ERR(rl2);
			ntfs_debug("Failed to allocate cluster, error code %i.",
					err);
			break;
		}
		lcn = rl2->lcn;
		rl = ntfs_runlists_merge(ni->runlist.rl, rl2);
		if (IS_ERR(rl)) {
			err = PTR_ERR(rl);
			if (err != -ENOMEM)
				err = -EIO;
			if (ntfs_cluster_free_from_rl(vol, rl2)) {
				ntfs_error(vol->sb, "Failed to release "
						"allocated cluster in error "
						"code path.  Run chkdsk to "
						"recover the lost cluster.");
				NVolSetErrors(vol);
			}
			ntfs_free(rl2);
			break;
		}
		ni->runlist.rl = rl;
		status.runlist_merged = 1;
		ntfs_debug("Allocated cluster, lcn 0x%llx.",
				(unsigned long long)lcn);
		/* Map and lock the mft record and get the attribute record. */
		if (!NInoAttr(ni))
			base_ni = ni;
		else
			base_ni = ni->ext.base_ntfs_ino;
		m = map_mft_record(base_ni);
		if (IS_ERR(m)) {
			err = PTR_ERR(m);
			break;
		}
		ctx = ntfs_attr_get_search_ctx(base_ni, m);
		if (unlikely(!ctx)) {
			err = -ENOMEM;
			unmap_mft_record(base_ni);
			break;
		}
		status.mft_attr_mapped = 1;
		err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
				CASE_SENSITIVE, bh_cpos, NULL, 0, ctx);
		if (unlikely(err)) {
			if (err == -ENOENT)
				err = -EIO;
			break;
		}
		m = ctx->mrec;
		a = ctx->attr;
		/*
		 * Find the runlist element with which the attribute extent
		 * starts.  Note, we cannot use the _attr_ version because we
		 * have mapped the mft record.  That is ok because we know the
		 * runlist fragment must be mapped already to have ever gotten
		 * here, so we can just use the _rl_ version.
		 */
		vcn = sle64_to_cpu(a->data.non_resident.lowest_vcn);
		rl2 = ntfs_rl_find_vcn_nolock(rl, vcn);
		BUG_ON(!rl2);
		BUG_ON(!rl2->length);
		BUG_ON(rl2->lcn < LCN_HOLE);
		highest_vcn = sle64_to_cpu(a->data.non_resident.highest_vcn);
		/*
		 * If @highest_vcn is zero, calculate the real highest_vcn
		 * (which can really be zero).
		 */
		if (!highest_vcn)
			highest_vcn = (sle64_to_cpu(
					a->data.non_resident.allocated_size) >>
					vol->cluster_size_bits) - 1;
		/*
		 * Determine the size of the mapping pairs array for the new
		 * extent, i.e. the old extent with the hole filled.
		 */
		mp_size = ntfs_get_size_for_mapping_pairs(vol, rl2, vcn,
				highest_vcn);
		if (unlikely(mp_size <= 0)) {
			if (!(err = mp_size))
				err = -EIO;
			ntfs_debug("Failed to get size for mapping pairs "
					"array, error code %i.", err);
			break;
		}
		/*
		 * Resize the attribute record to fit the new mapping pairs
		 * array.
		 */
		attr_rec_len = le32_to_cpu(a->length);
		err = ntfs_attr_record_resize(m, a, mp_size + le16_to_cpu(
				a->data.non_resident.mapping_pairs_offset));
		if (unlikely(err)) {
			BUG_ON(err != -ENOSPC);
			// TODO: Deal with this by using the current attribute
			// and fill it with as much of the mapping pairs
			// array as possible.  Then loop over each attribute
			// extent rewriting the mapping pairs arrays as we go
			// along and if when we reach the end we have not
			// enough space, try to resize the last attribute
			// extent and if even that fails, add a new attribute
			// extent.
			// We could also try to resize at each step in the hope
			// that we will not need to rewrite every single extent.
			// Note, we may need to decompress some extents to fill
			// the runlist as we are walking the extents...
			ntfs_error(vol->sb, "Not enough space in the mft "
					"record for the extended attribute "
					"record.  This case is not "
					"implemented yet.");
			err = -EOPNOTSUPP;
			break ;
		}
		status.mp_rebuilt = 1;
		/*
		 * Generate the mapping pairs array directly into the attribute
		 * record.
		 */
		err = ntfs_mapping_pairs_build(vol, (u8*)a + le16_to_cpu(
				a->data.non_resident.mapping_pairs_offset),
				mp_size, rl2, vcn, highest_vcn, NULL);
		if (unlikely(err)) {
			ntfs_error(vol->sb, "Cannot fill hole in inode 0x%lx, "
					"attribute type 0x%x, because building "
					"the mapping pairs failed with error "
					"code %i.", vi->i_ino,
					(unsigned)le32_to_cpu(ni->type), err);
			err = -EIO;
			break;
		}
		/* Update the highest_vcn but only if it was not set. */
		if (unlikely(!a->data.non_resident.highest_vcn))
			a->data.non_resident.highest_vcn =
					cpu_to_sle64(highest_vcn);
		/*
		 * If the attribute is sparse/compressed, update the compressed
		 * size in the ntfs_inode structure and the attribute record.
		 */
		if (likely(NInoSparse(ni) || NInoCompressed(ni))) {
			/*
			 * If we are not in the first attribute extent, switch
			 * to it, but first ensure the changes will make it to
			 * disk later.
			 */
			if (a->data.non_resident.lowest_vcn) {
				flush_dcache_mft_record_page(ctx->ntfs_ino);
				mark_mft_record_dirty(ctx->ntfs_ino);
				ntfs_attr_reinit_search_ctx(ctx);
				err = ntfs_attr_lookup(ni->type, ni->name,
						ni->name_len, CASE_SENSITIVE,
						0, NULL, 0, ctx);
				if (unlikely(err)) {
					status.attr_switched = 1;
					break;
				}
				/* @m is not used any more so do not set it. */
				a = ctx->attr;
			}
			write_lock_irqsave(&ni->size_lock, flags);
			ni->itype.compressed.size += vol->cluster_size;
			a->data.non_resident.compressed_size =
					cpu_to_sle64(ni->itype.compressed.size);
			write_unlock_irqrestore(&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(base_ni);
		/* Successfully filled the hole. */
		status.runlist_merged = 0;
		status.mft_attr_mapped = 0;
		status.mp_rebuilt = 0;
		/* Setup the map cache and use that to deal with the buffer. */
		was_hole = true;
		vcn = bh_cpos;
		vcn_len = 1;
		lcn_block = lcn << (vol->cluster_size_bits - blocksize_bits);
		cdelta = 0;
		/*
		 * If the number of remaining clusters in the @pages is smaller
		 * or equal to the number of cached clusters, unlock the
		 * runlist as the map cache will be used from now on.
		 */
		if (likely(vcn + vcn_len >= cend)) {
			up_write(&ni->runlist.lock);
			rl_write_locked = false;
			rl = NULL;
		}
		goto map_buffer_cached;
	} while (bh_pos += blocksize, (bh = bh->b_this_page) != head);
	/* If there are no errors, do the next page. */
	if (likely(!err && ++u < nr_pages))
		goto do_next_page;
	/* If there are no errors, release the runlist lock if we took it. */
	if (likely(!err)) {
		if (unlikely(rl_write_locked)) {
			up_write(&ni->runlist.lock);
			rl_write_locked = false;
		} else if (unlikely(rl))
			up_read(&ni->runlist.lock);
		rl = NULL;
	}
	/* If we issued read requests, let them complete. */
	read_lock_irqsave(&ni->size_lock, flags);
	initialized_size = ni->initialized_size;
	read_unlock_irqrestore(&ni->size_lock, flags);
	while (wait_bh > wait) {
		bh = *--wait_bh;
		wait_on_buffer(bh);
		if (likely(buffer_uptodate(bh))) {
			page = bh->b_page;
			bh_pos = ((s64)page->index << PAGE_CACHE_SHIFT) +
					bh_offset(bh);
			/*
			 * If the buffer overflows the initialized size, need
			 * to zero the overflowing region.
			 */
			if (unlikely(bh_pos + blocksize > initialized_size)) {
				int ofs = 0;

				if (likely(bh_pos < initialized_size))
					ofs = initialized_size - bh_pos;
				zero_user_segment(page, bh_offset(bh) + ofs,
						blocksize);
			}
		} else /* if (unlikely(!buffer_uptodate(bh))) */
			err = -EIO;
	}
	if (likely(!err)) {
		/* Clear buffer_new on all buffers. */
		u = 0;
		do {
			bh = head = page_buffers(pages[u]);
			do {
				if (buffer_new(bh))
					clear_buffer_new(bh);
			} while ((bh = bh->b_this_page) != head);
		} while (++u < nr_pages);
		ntfs_debug("Done.");
		return err;
	}
	if (status.attr_switched) {
		/* Get back to the attribute extent we modified. */
		ntfs_attr_reinit_search_ctx(ctx);
		if (ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
				CASE_SENSITIVE, bh_cpos, NULL, 0, ctx)) {
			ntfs_error(vol->sb, "Failed to find required "
					"attribute extent of attribute in "
					"error code path.  Run chkdsk to "
					"recover.");
			write_lock_irqsave(&ni->size_lock, flags);
			ni->itype.compressed.size += vol->cluster_size;
			write_unlock_irqrestore(&ni->size_lock, flags);
			flush_dcache_mft_record_page(ctx->ntfs_ino);
			mark_mft_record_dirty(ctx->ntfs_ino);
			/*
			 * The only thing that is now wrong is the compressed
			 * size of the base attribute extent which chkdsk
			 * should be able to fix.
			 */
			NVolSetErrors(vol);
		} else {
			m = ctx->mrec;
			a = ctx->attr;
			status.attr_switched = 0;
		}
	}
	/*
	 * If the runlist has been modified, need to restore it by punching a
	 * hole into it and we then need to deallocate the on-disk cluster as
	 * well.  Note, we only modify the runlist if we are able to generate a
	 * new mapping pairs array, i.e. only when the mapped attribute extent
	 * is not switched.
	 */
	if (status.runlist_merged && !status.attr_switched) {
		BUG_ON(!rl_write_locked);
		/* Make the file cluster we allocated sparse in the runlist. */
		if (ntfs_rl_punch_nolock(vol, &ni->runlist, bh_cpos, 1)) {
			ntfs_error(vol->sb, "Failed to punch hole into "
					"attribute runlist in error code "
					"path.  Run chkdsk to recover the "
					"lost cluster.");
			NVolSetErrors(vol);
		} else /* if (success) */ {
			status.runlist_merged = 0;
			/*
			 * Deallocate the on-disk cluster we allocated but only
			 * if we succeeded in punching its vcn out of the
			 * runlist.
			 */
			down_write(&vol->lcnbmp_lock);
			if (ntfs_bitmap_clear_bit(vol->lcnbmp_ino, lcn)) {
				ntfs_error(vol->sb, "Failed to release "
						"allocated cluster in error "
						"code path.  Run chkdsk to "
						"recover the lost cluster.");
				NVolSetErrors(vol);
			}
			up_write(&vol->lcnbmp_lock);
		}
	}
	/*
	 * Resize the attribute record to its old size and rebuild the mapping
	 * pairs array.  Note, we only can do this if the runlist has been
	 * restored to its old state which also implies that the mapped
	 * attribute extent is not switched.
	 */
	if (status.mp_rebuilt && !status.runlist_merged) {
		if (ntfs_attr_record_resize(m, a, attr_rec_len)) {
			ntfs_error(vol->sb, "Failed to restore attribute "
					"record in error code path.  Run "
					"chkdsk to recover.");
			NVolSetErrors(vol);
		} else /* if (success) */ {
			if (ntfs_mapping_pairs_build(vol, (u8*)a +
					le16_to_cpu(a->data.non_resident.
					mapping_pairs_offset), attr_rec_len -
					le16_to_cpu(a->data.non_resident.
					mapping_pairs_offset), ni->runlist.rl,
					vcn, highest_vcn, NULL)) {
				ntfs_error(vol->sb, "Failed to restore "
						"mapping pairs array in error "
						"code path.  Run chkdsk to "
						"recover.");
				NVolSetErrors(vol);
			}
			flush_dcache_mft_record_page(ctx->ntfs_ino);
			mark_mft_record_dirty(ctx->ntfs_ino);
		}
	}
	/* Release the mft record and the attribute. */
	if (status.mft_attr_mapped) {
		ntfs_attr_put_search_ctx(ctx);
		unmap_mft_record(base_ni);
	}
	/* Release the runlist lock. */
	if (rl_write_locked)
		up_write(&ni->runlist.lock);
	else if (rl)
		up_read(&ni->runlist.lock);
	/*
	 * Zero out any newly allocated blocks to avoid exposing stale data.
	 * If BH_New is set, we know that the block was newly allocated above
	 * and that it has not been fully zeroed and marked dirty yet.
	 */
	nr_pages = u;
	u = 0;
	end = bh_cpos << vol->cluster_size_bits;
	do {
		page = pages[u];
		bh = head = page_buffers(page);
		do {
			if (u == nr_pages &&
					((s64)page->index << PAGE_CACHE_SHIFT) +
					bh_offset(bh) >= end)
				break;
			if (!buffer_new(bh))
				continue;
			clear_buffer_new(bh);
			if (!buffer_uptodate(bh)) {
				if (PageUptodate(page))
					set_buffer_uptodate(bh);
				else {
					zero_user(page, bh_offset(bh),
							blocksize);
					set_buffer_uptodate(bh);
				}
			}
			mark_buffer_dirty(bh);
		} while ((bh = bh->b_this_page) != head);
	} while (++u <= nr_pages);
	ntfs_error(vol->sb, "Failed.  Returning error code %i.", err);
	return err;
}

/*
 * Copy as much as we can into the pages and return the number of bytes which
 * were successfully copied.  If a fault is encountered then clear the pages
 * out to (ofs + bytes) and return the number of bytes which were copied.
 */
static inline size_t ntfs_copy_from_user(struct page **pages,
		unsigned nr_pages, unsigned ofs, const char __user *buf,
		size_t bytes)
{
	struct page **last_page = pages + nr_pages;
	char *addr;
	size_t total = 0;
	unsigned len;
	int left;

	do {
		len = PAGE_CACHE_SIZE - ofs;
		if (len > bytes)
			len = bytes;
		addr = kmap_atomic(*pages);
		left = __copy_from_user_inatomic(addr + ofs, buf, len);
		kunmap_atomic(addr);
		if (unlikely(left)) {
			/* Do it the slow way. */
			addr = kmap(*pages);
			left = __copy_from_user(addr + ofs, buf, len);
			kunmap(*pages);
			if (unlikely(left))
				goto err_out;
		}
		total += len;
		bytes -= len;
		if (!bytes)
			break;
		buf += len;
		ofs = 0;
	} while (++pages < last_page);
out:
	return total;
err_out:
	total += len - left;
	/* Zero the rest of the target like __copy_from_user(). */
	while (++pages < last_page) {
		bytes -= len;
		if (!bytes)
			break;
		len = PAGE_CACHE_SIZE;
		if (len > bytes)
			len = bytes;
		zero_user(*pages, 0, len);
	}
	goto out;
}

static size_t __ntfs_copy_from_user_iovec_inatomic(char *vaddr,
		const struct iovec *iov, size_t iov_ofs, size_t bytes)
{
	size_t total = 0;

	while (1) {
		const char __user *buf = iov->iov_base + iov_ofs;
		unsigned len;
		size_t left;

		len = iov->iov_len - iov_ofs;
		if (len > bytes)
			len = bytes;
		left = __copy_from_user_inatomic(vaddr, buf, len);
		total += len;
		bytes -= len;
		vaddr += len;
		if (unlikely(left)) {
			total -= left;
			break;
		}
		if (!bytes)
			break;
		iov++;
		iov_ofs = 0;
	}
	return total;
}

static inline void ntfs_set_next_iovec(const struct iovec **iovp,
		size_t *iov_ofsp, size_t bytes)
{
	const struct iovec *iov = *iovp;
	size_t iov_ofs = *iov_ofsp;

	while (bytes) {
		unsigned len;

		len = iov->iov_len - iov_ofs;
		if (len > bytes)
			len = bytes;
		bytes -= len;
		iov_ofs += len;
		if (iov->iov_len == iov_ofs) {
			iov++;
			iov_ofs = 0;
		}
	}
	*iovp = iov;
	*iov_ofsp = iov_ofs;
}

/*
 * This has the same side-effects and return value as ntfs_copy_from_user().
 * The difference is that on a fault we need to memset the remainder of the
 * pages (out to offset + bytes), to emulate ntfs_copy_from_user()'s
 * single-segment behaviour.
 *
 * We call the same helper (__ntfs_copy_from_user_iovec_inatomic()) both when
 * atomic and when not atomic.  This is ok because it calls
 * __copy_from_user_inatomic() and it is ok to call this when non-atomic.  In
 * fact, the only difference between __copy_from_user_inatomic() and
 * __copy_from_user() is that the latter calls might_sleep() and the former
 * should not zero the tail of the buffer on error.  And on many architectures
 * __copy_from_user_inatomic() is just defined to __copy_from_user() so it
 * makes no difference at all on those architectures.
 */
static inline size_t ntfs_copy_from_user_iovec(struct page **pages,
		unsigned nr_pages, unsigned ofs, const struct iovec **iov,
		size_t *iov_ofs, size_t bytes)
{
	struct page **last_page = pages + nr_pages;
	char *addr;
	size_t copied, len, total = 0;

	do {
		len = PAGE_CACHE_SIZE - ofs;
		if (len > bytes)
			len = bytes;
		addr = kmap_atomic(*pages);
		copied = __ntfs_copy_from_user_iovec_inatomic(addr + ofs,
				*iov, *iov_ofs, len);
		kunmap_atomic(addr);
		if (unlikely(copied != len)) {
			/* Do it the slow way. */
			addr = kmap(*pages);
			copied = __ntfs_copy_from_user_iovec_inatomic(addr +
					ofs, *iov, *iov_ofs, len);
			if (unlikely(copied != len))
				goto err_out;
			kunmap(*pages);
		}
		total += len;
		ntfs_set_next_iovec(iov, iov_ofs, len);
		bytes -= len;
		if (!bytes)
			break;
		ofs = 0;
	} while (++pages < last_page);
out:
	return total;
err_out:
	BUG_ON(copied > len);
	/* Zero the rest of the target like __copy_from_user(). */
	memset(addr + ofs + copied, 0, len - copied);
	kunmap(*pages);
	total += copied;
	ntfs_set_next_iovec(iov, iov_ofs, copied);
	while (++pages < last_page) {
		bytes -= len;
		if (!bytes)
			break;
		len = PAGE_CACHE_SIZE;
		if (len > bytes)
			len = bytes;
		zero_user(*pages, 0, len);
	}
	goto out;
}

static inline void ntfs_flush_dcache_pages(struct page **pages,
		unsigned nr_pages)
{
	BUG_ON(!nr_pages);
	/*
	 * Warning: Do not do the decrement at the same time as the call to
	 * flush_dcache_page() because it is a NULL macro on i386 and hence the
	 * decrement never happens so the loop never terminates.
	 */
	do {
		--nr_pages;
		flush_dcache_page(pages[nr_pages]);
	} while (nr_pages > 0);
}

/**
 * ntfs_commit_pages_after_non_resident_write - commit the received data
 * @pages:	array of destination pages
 * @nr_pages:	number of pages in @pages
 * @pos:	byte position in file at which the write begins
 * @bytes:	number of bytes to be written
 *
 * See description of ntfs_commit_pages_after_write(), below.
 */
static inline int ntfs_commit_pages_after_non_resident_write(
		struct page **pages, const unsigned nr_pages,
		s64 pos, size_t bytes)
{
	s64 end, initialized_size;
	struct inode *vi;
	ntfs_inode *ni, *base_ni;
	struct buffer_head *bh, *head;
	ntfs_attr_search_ctx *ctx;
	MFT_RECORD *m;
	ATTR_RECORD *a;
	unsigned long flags;
	unsigned blocksize, u;
	int err;

	vi = pages[0]->mapping->host;
	ni = NTFS_I(vi);
	blocksize = vi->i_sb->s_blocksize;
	end = pos + bytes;
	u = 0;
	do {
		s64 bh_pos;
		struct page *page;
		bool partial;

		page = pages[u];
		bh_pos = (s64)page->index << PAGE_CACHE_SHIFT;
		bh = head = page_buffers(page);
		partial = false;
		do {
			s64 bh_end;

			bh_end = bh_pos + blocksize;
			if (bh_end <= pos || bh_pos >= end) {
				if (!buffer_uptodate(bh))
					partial = true;
			} else {
				set_buffer_uptodate(bh);
				mark_buffer_dirty(bh);
			}
		} while (bh_pos += blocksize, (bh = bh->b_this_page) != head);
		/*
		 * If all buffers are now uptodate but the page is not, set the
		 * page uptodate.
		 */
		if (!partial && !PageUptodate(page))
			SetPageUptodate(page);
	} while (++u < nr_pages);
	/*
	 * Finally, if we do not need to update initialized_size or i_size we
	 * are finished.
	 */
	read_lock_irqsave(&ni->size_lock, flags);
	initialized_size = ni->initialized_size;
	read_unlock_irqrestore(&ni->size_lock, flags);
	if (end <= initialized_size) {
		ntfs_debug("Done.");
		return 0;
	}
	/*
	 * Update initialized_size/i_size as appropriate, both in the inode and
	 * the mft record.
	 */
	if (!NInoAttr(ni))
		base_ni = ni;
	else
		base_ni = ni->ext.base_ntfs_ino;
	/* Map, pin, and lock the mft record. */
	m = map_mft_record(base_ni);
	if (IS_ERR(m)) {
		err = PTR_ERR(m);
		m = NULL;
		ctx = NULL;
		goto err_out;
	}
	BUG_ON(!NInoNonResident(ni));
	ctx = ntfs_attr_get_search_ctx(base_ni, m);
	if (unlikely(!ctx)) {
		err = -ENOMEM;
		goto err_out;
	}
	err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
			CASE_SENSITIVE, 0, NULL, 0, ctx);
	if (unlikely(err)) {
		if (err == -ENOENT)
			err = -EIO;
		goto err_out;
	}
	a = ctx->attr;
	BUG_ON(!a->non_resident);
	write_lock_irqsave(&ni->size_lock, flags);
	BUG_ON(end > ni->allocated_size);
	ni->initialized_size = end;
	a->data.non_resident.initialized_size = cpu_to_sle64(end);
	if (end > i_size_read(vi)) {
		i_size_write(vi, end);
		a->data.non_resident.data_size =
				a->data.non_resident.initialized_size;
	}
	write_unlock_irqrestore(&ni->size_lock, flags);
	/* Mark the mft record dirty, so it gets written back. */
	flush_dcache_mft_record_page(ctx->ntfs_ino);
	mark_mft_record_dirty(ctx->ntfs_ino);
	ntfs_attr_put_search_ctx(ctx);
	unmap_mft_record(base_ni);
	ntfs_debug("Done.");
	return 0;
err_out:
	if (ctx)
		ntfs_attr_put_search_ctx(ctx);
	if (m)
		unmap_mft_record(base_ni);
	ntfs_error(vi->i_sb, "Failed to update initialized_size/i_size (error "
			"code %i).", err);
	if (err != -ENOMEM)
		NVolSetErrors(ni->vol);
	return err;
}

/**
 * ntfs_commit_pages_after_write - commit the received data
 * @pages:	array of destination pages
 * @nr_pages:	number of pages in @pages
 * @pos:	byte position in file at which the write begins
 * @bytes:	number of bytes to be written
 *
 * This is called from ntfs_file_buffered_write() with i_mutex held on the inode
 * (@pages[0]->mapping->host).  There are @nr_pages pages in @pages which are
 * locked but not kmap()ped.  The source data has already been copied into the
 * @page.  ntfs_prepare_pages_for_non_resident_write() has been called before
 * the data was copied (for non-resident attributes only) and it returned
 * success.
 *
 * Need to set uptodate and mark dirty all buffers within the boundary of the
 * write.  If all buffers in a page are uptodate we set the page uptodate, too.
 *
 * Setting the buffers dirty ensures that they get written out later when
 * ntfs_writepage() is invoked by the VM.
 *
 * Finally, we need to update i_size and initialized_size as appropriate both
 * in the inode and the mft record.
 *
 * This is modelled after fs/buffer.c::generic_commit_write(), which marks
 * buffers uptodate and dirty, sets the page uptodate if all buffers in the
 * page are uptodate, and updates i_size if the end of io is beyond i_size.  In
 * that case, it also marks the inode dirty.
 *
 * If things have gone as outlined in
 * ntfs_prepare_pages_for_non_resident_write(), we do not need to do any page
 * content modifications here for non-resident attributes.  For resident
 * attributes we need to do the uptodate bringing here which we combine with
 * the copying into the mft record which means we save one atomic kmap.
 *
 * Return 0 on success or -errno on error.
 */
static int ntfs_commit_pages_after_write(struct page **pages,
		const unsigned nr_pages, s64 pos, size_t bytes)
{
	s64 end, initialized_size;
	loff_t i_size;
	struct inode *vi;
	ntfs_inode *ni, *base_ni;
	struct page *page;
	ntfs_attr_search_ctx *ctx;
	MFT_RECORD *m;
	ATTR_RECORD *a;
	char *kattr, *kaddr;
	unsigned long flags;
	u32 attr_len;
	int err;

	BUG_ON(!nr_pages);
	BUG_ON(!pages);
	page = pages[0];
	BUG_ON(!page);
	vi = page->mapping->host;
	ni = NTFS_I(vi);
	ntfs_debug("Entering for inode 0x%lx, attribute type 0x%x, start page "
			"index 0x%lx, nr_pages 0x%x, pos 0x%llx, bytes 0x%zx.",
			vi->i_ino, ni->type, page->index, nr_pages,
			(long long)pos, bytes);
	if (NInoNonResident(ni))
		return ntfs_commit_pages_after_non_resident_write(pages,
				nr_pages, pos, bytes);
	BUG_ON(nr_pages > 1);
	/*
	 * Attribute is resident, implying it is not compressed, encrypted, or
	 * sparse.
	 */
	if (!NInoAttr(ni))
		base_ni = ni;
	else
		base_ni = ni->ext.base_ntfs_ino;
	BUG_ON(NInoNonResident(ni));
	/* Map, pin, and lock the mft record. */
	m = map_mft_record(base_ni);
	if (IS_ERR(m)) {
		err = PTR_ERR(m);
		m = NULL;
		ctx = NULL;
		goto err_out;
	}
	ctx = ntfs_attr_get_search_ctx(base_ni, m);
	if (unlikely(!ctx)) {
		err = -ENOMEM;
		goto err_out;
	}
	err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
			CASE_SENSITIVE, 0, NULL, 0, ctx);
	if (unlikely(err)) {
		if (err == -ENOENT)
			err = -EIO;
		goto err_out;
	}
	a = ctx->attr;
	BUG_ON(a->non_resident);
	/* The total length of the attribute value. */
	attr_len = le32_to_cpu(a->data.resident.value_length);
	i_size = i_size_read(vi);
	BUG_ON(attr_len != i_size);
	BUG_ON(pos > attr_len);
	end = pos + bytes;
	BUG_ON(end > le32_to_cpu(a->length) -
			le16_to_cpu(a->data.resident.value_offset));
	kattr = (u8*)a + le16_to_cpu(a->data.resident.value_offset);
	kaddr = kmap_atomic(page);
	/* Copy the received data from the page to the mft record. */
	memcpy(kattr + pos, kaddr + pos, bytes);
	/* Update the attribute length if necessary. */
	if (end > attr_len) {
		attr_len = end;
		a->data.resident.value_length = cpu_to_le32(attr_len);
	}
	/*
	 * If the page is not uptodate, bring the out of bounds area(s)
	 * uptodate by copying data from the mft record to the page.
	 */
	if (!PageUptodate(page)) {
		if (pos > 0)
			memcpy(kaddr, kattr, pos);
		if (end < attr_len)
			memcpy(kaddr + end, kattr + end, attr_len - end);
		/* Zero the region outside the end of the attribute value. */
		memset(kaddr + attr_len, 0, PAGE_CACHE_SIZE - attr_len);
		flush_dcache_page(page);
		SetPageUptodate(page);
	}
	kunmap_atomic(kaddr);
	/* Update initialized_size/i_size if necessary. */
	read_lock_irqsave(&ni->size_lock, flags);
	initialized_size = ni->initialized_size;
	BUG_ON(end > ni->allocated_size);
	read_unlock_irqrestore(&ni->size_lock, flags);
	BUG_ON(initialized_size != i_size);
	if (end > initialized_size) {
		write_lock_irqsave(&ni->size_lock, flags);
		ni->initialized_size = end;
		i_size_write(vi, end);
		write_unlock_irqrestore(&ni->size_lock, flags);
	}
	/* Mark the mft record dirty, so it gets written back. */
	flush_dcache_mft_record_page(ctx->ntfs_ino);
	mark_mft_record_dirty(ctx->ntfs_ino);
	ntfs_attr_put_search_ctx(ctx);
	unmap_mft_record(base_ni);
	ntfs_debug("Done.");
	return 0;
err_out:
	if (err == -ENOMEM) {
		ntfs_warning(vi->i_sb, "Error allocating memory required to "
				"commit the write.");
		if (PageUptodate(page)) {
			ntfs_warning(vi->i_sb, "Page is uptodate, setting "
					"dirty so the write will be retried "
					"later on by the VM.");
			/*
			 * Put the page on mapping->dirty_pages, but leave its
			 * buffers' dirty state as-is.
			 */
			__set_page_dirty_nobuffers(page);
			err = 0;
		} else
			ntfs_error(vi->i_sb, "Page is not uptodate.  Written "
					"data has been lost.");
	} else {
		ntfs_error(vi->i_sb, "Resident attribute commit write failed "
				"with error %i.", err);
		NVolSetErrors(ni->vol);
	}
	if (ctx)
		ntfs_attr_put_search_ctx(ctx);
	if (m)
		unmap_mft_record(base_ni);
	return err;
}

static void ntfs_write_failed(struct address_space *mapping, loff_t to)
{
	struct inode *inode = mapping->host;

	if (to > inode->i_size) {
		truncate_pagecache(inode, inode->i_size);
		ntfs_truncate_vfs(inode);
	}
}

/**
 * ntfs_file_buffered_write -
 *
 * Locking: The vfs is holding ->i_mutex on the inode.
 */
static ssize_t ntfs_file_buffered_write(struct kiocb *iocb,
		const struct iovec *iov, unsigned long nr_segs,
		loff_t pos, loff_t *ppos, size_t count)
{
	struct file *file = iocb->ki_filp;
	struct address_space *mapping = file->f_mapping;
	struct inode *vi = mapping->host;
	ntfs_inode *ni = NTFS_I(vi);
	ntfs_volume *vol = ni->vol;
	struct page *pages[NTFS_MAX_PAGES_PER_CLUSTER];
	struct page *cached_page = NULL;
	char __user *buf = NULL;
	s64 end, ll;
	VCN last_vcn;
	LCN lcn;
	unsigned long flags;
	size_t bytes, iov_ofs = 0;	/* Offset in the current iovec. */
	ssize_t status, written;
	unsigned nr_pages;
	int err;

	ntfs_debug("Entering for i_ino 0x%lx, attribute type 0x%x, "
			"pos 0x%llx, count 0x%lx.",
			vi->i_ino, (unsigned)le32_to_cpu(ni->type),
			(unsigned long long)pos, (unsigned long)count);
	if (unlikely(!count))
		return 0;
	BUG_ON(NInoMstProtected(ni));
	/*
	 * If the attribute is not an index root and it is encrypted or
	 * compressed, we cannot write to it yet.  Note we need to check for
	 * AT_INDEX_ALLOCATION since this is the type of both directory and
	 * index inodes.
	 */
	if (ni->type != AT_INDEX_ALLOCATION) {
		/* If file is encrypted, deny access, just like NT4. */
		if (NInoEncrypted(ni)) {
			/*
			 * Reminder for later: Encrypted files are _always_
			 * non-resident so that the content can always be
			 * encrypted.
			 */
			ntfs_debug("Denying write access to encrypted file.");
			return -EACCES;
		}
		if (NInoCompressed(ni)) {
			/* Only unnamed $DATA attribute can be compressed. */
			BUG_ON(ni->type != AT_DATA);
			BUG_ON(ni->name_len);
			/*
			 * Reminder for later: If resident, the data is not
			 * actually compressed.  Only on the switch to non-
			 * resident does compression kick in.  This is in
			 * contrast to encrypted files (see above).
			 */
			ntfs_error(vi->i_sb, "Writing to compressed files is "
					"not implemented yet.  Sorry.");
			return -EOPNOTSUPP;
		}
	}
	/*
	 * If a previous ntfs_truncate() failed, repeat it and abort if it
	 * fails again.
	 */
	if (unlikely(NInoTruncateFailed(ni))) {
		inode_dio_wait(vi);
		err = ntfs_truncate(vi);
		if (err || NInoTruncateFailed(ni)) {
			if (!err)
				err = -EIO;
			ntfs_error(vol->sb, "Cannot perform write to inode "
					"0x%lx, attribute type 0x%x, because "
					"ntfs_truncate() failed (error code "
					"%i).", vi->i_ino,
					(unsigned)le32_to_cpu(ni->type), err);
			return err;
		}
	}
	/* The first byte after the write. */
	end = pos + count;
	/*
	 * If the write goes beyond the allocated size, extend the allocation
	 * to cover the whole of the write, rounded up to the nearest cluster.
	 */
	read_lock_irqsave(&ni->size_lock, flags);
	ll = ni->allocated_size;
	read_unlock_irqrestore(&ni->size_lock, flags);
	if (end > ll) {
		/* Extend the allocation without changing the data size. */
		ll = ntfs_attr_extend_allocation(ni, end, -1, pos);
		if (likely(ll >= 0)) {
			BUG_ON(pos >= ll);
			/* If the extension was partial truncate the write. */
			if (end > ll) {
				ntfs_debug("Truncating write to inode 0x%lx, "
						"attribute type 0x%x, because "
						"the allocation was only "
						"partially extended.",
						vi->i_ino, (unsigned)
						le32_to_cpu(ni->type));
				end = ll;
				count = ll - pos;
			}
		} else {
			err = ll;
			read_lock_irqsave(&ni->size_lock, flags);
			ll = ni->allocated_size;
			read_unlock_irqrestore(&ni->size_lock, flags);
			/* Perform a partial write if possible or fail. */
			if (pos < ll) {
				ntfs_debug("Truncating write to inode 0x%lx, "
						"attribute type 0x%x, because "
						"extending the allocation "
						"failed (error code %i).",
						vi->i_ino, (unsigned)
						le32_to_cpu(ni->type), err);
				end = ll;
				count = ll - pos;
			} else {
				ntfs_error(vol->sb, "Cannot perform write to "
						"inode 0x%lx, attribute type "
						"0x%x, because extending the "
						"allocation failed (error "
						"code %i).", vi->i_ino,
						(unsigned)
						le32_to_cpu(ni->type), err);
				return err;
			}
		}
	}
	written = 0;
	/*
	 * If the write starts beyond the initialized size, extend it up to the
	 * beginning of the write and initialize all non-sparse space between
	 * the old initialized size and the new one.  This automatically also
	 * increments the vfs inode->i_size to keep it above or equal to the
	 * initialized_size.
	 */
	read_lock_irqsave(&ni->size_lock, flags);
	ll = ni->initialized_size;
	read_unlock_irqrestore(&ni->size_lock, flags);
	if (pos > ll) {
		err = ntfs_attr_extend_initialized(ni, pos);
		if (err < 0) {
			ntfs_error(vol->sb, "Cannot perform write to inode "
					"0x%lx, attribute type 0x%x, because "
					"extending the initialized size "
					"failed (error code %i).", vi->i_ino,
					(unsigned)le32_to_cpu(ni->type), err);
			status = err;
			goto err_out;
		}
	}
	/*
	 * Determine the number of pages per cluster for non-resident
	 * attributes.
	 */
	nr_pages = 1;
	if (vol->cluster_size > PAGE_CACHE_SIZE && NInoNonResident(ni))
		nr_pages = vol->cluster_size >> PAGE_CACHE_SHIFT;
	/* Finally, perform the actual write. */
	last_vcn = -1;
	if (likely(nr_segs == 1))
		buf = iov->iov_base;
	do {
		VCN vcn;
		pgoff_t idx, start_idx;
		unsigned ofs, do_pages, u;
		size_t copied;

		start_idx = idx = pos >> PAGE_CACHE_SHIFT;
		ofs = pos & ~PAGE_CACHE_MASK;
		bytes = PAGE_CACHE_SIZE - ofs;
		do_pages = 1;
		if (nr_pages > 1) {
			vcn = pos >> vol->cluster_size_bits;
			if (vcn != last_vcn) {
				last_vcn = vcn;
				/*
				 * Get the lcn of the vcn the write is in.  If
				 * it is a hole, need to lock down all pages in
				 * the cluster.
				 */
				down_read(&ni->runlist.lock);
				lcn = ntfs_attr_vcn_to_lcn_nolock(ni, pos >>
						vol->cluster_size_bits, false);
				up_read(&ni->runlist.lock);
				if (unlikely(lcn < LCN_HOLE)) {
					status = -EIO;
					if (lcn == LCN_ENOMEM)
						status = -ENOMEM;
					else
						ntfs_error(vol->sb, "Cannot "
							"perform write to "
							"inode 0x%lx, "
							"attribute type 0x%x, "
							"because the attribute "
							"is corrupt.",
							vi->i_ino, (unsigned)
							le32_to_cpu(ni->type));
					break;
				}
				if (lcn == LCN_HOLE) {
					start_idx = (pos & ~(s64)
							vol->cluster_size_mask)
							>> PAGE_CACHE_SHIFT;
					bytes = vol->cluster_size - (pos &
							vol->cluster_size_mask);
					do_pages = nr_pages;
				}
			}
		}
		if (bytes > count)
			bytes = count;
		/*
		 * Bring in the user page(s) that we will copy from _first_.
		 * Otherwise there is a nasty deadlock on copying from the same
		 * page(s) as we are writing to, without it/them being marked
		 * up-to-date.  Note, at present there is nothing to stop the
		 * pages being swapped out between us bringing them into memory
		 * and doing the actual copying.
		 */
		if (likely(nr_segs == 1))
			ntfs_fault_in_pages_readable(buf, bytes);
		else
			ntfs_fault_in_pages_readable_iovec(iov, iov_ofs, bytes);
		/* Get and lock @do_pages starting at index @start_idx. */
		status = __ntfs_grab_cache_pages(mapping, start_idx, do_pages,
				pages, &cached_page);
		if (unlikely(status))
			break;
		/*
		 * For non-resident attributes, we need to fill any holes with
		 * actual clusters and ensure all bufferes are mapped.  We also
		 * need to bring uptodate any buffers that are only partially
		 * being written to.
		 */
		if (NInoNonResident(ni)) {
			status = ntfs_prepare_pages_for_non_resident_write(
					pages, do_pages, pos, bytes);
			if (unlikely(status)) {
				loff_t i_size;

				do {
					unlock_page(pages[--do_pages]);
					page_cache_release(pages[do_pages]);
				} while (do_pages);
				/*
				 * The write preparation may have instantiated
				 * allocated space outside i_size.  Trim this
				 * off again.  We can ignore any errors in this
				 * case as we will just be waisting a bit of
				 * allocated space, which is not a disaster.
				 */
				i_size = i_size_read(vi);
				if (pos + bytes > i_size) {
					ntfs_write_failed(mapping, pos + bytes);
				}
				break;
			}
		}
		u = (pos >> PAGE_CACHE_SHIFT) - pages[0]->index;
		if (likely(nr_segs == 1)) {
			copied = ntfs_copy_from_user(pages + u, do_pages - u,
					ofs, buf, bytes);
			buf += copied;
		} else
			copied = ntfs_copy_from_user_iovec(pages + u,
					do_pages - u, ofs, &iov, &iov_ofs,
					bytes);
		ntfs_flush_dcache_pages(pages + u, do_pages - u);
		status = ntfs_commit_pages_after_write(pages, do_pages, pos,
				bytes);
		if (likely(!status)) {
			written += copied;
			count -= copied;
			pos += copied;
			if (unlikely(copied != bytes))
				status = -EFAULT;
		}
		do {
			unlock_page(pages[--do_pages]);
			mark_page_accessed(pages[do_pages]);
			page_cache_release(pages[do_pages]);
		} while (do_pages);
		if (unlikely(status))
			break;
		balance_dirty_pages_ratelimited(mapping);
		cond_resched();
	} while (count);
err_out:
	*ppos = pos;
	if (cached_page)
		page_cache_release(cached_page);
	ntfs_debug("Done.  Returning %s (written 0x%lx, status %li).",
			written ? "written" : "status", (unsigned long)written,
			(long)status);
	return written ? written : status;
}

/**
 * ntfs_file_aio_write_nolock -
 */
static ssize_t ntfs_file_aio_write_nolock(struct kiocb *iocb,
		const struct iovec *iov, unsigned long nr_segs, loff_t *ppos)
{
	struct file *file = iocb->ki_filp;
	struct address_space *mapping = file->f_mapping;
	struct inode *inode = mapping->host;
	loff_t pos;
	size_t count;		/* after file limit checks */
	ssize_t written, err;

	count = iov_length(iov, nr_segs);
	pos = *ppos;
	/* We can write back this queue in page reclaim. */
	current->backing_dev_info = mapping->backing_dev_info;
	written = 0;
	err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
	if (err)
		goto out;
	if (!count)
		goto out;
	err = file_remove_suid(file);
	if (err)
		goto out;
	err = file_update_time(file);
	if (err)
		goto out;
	written = ntfs_file_buffered_write(iocb, iov, nr_segs, pos, ppos,
			count);
out:
	current->backing_dev_info = NULL;
	return written ? written : err;
}

/**
 * ntfs_file_aio_write -
 */
static ssize_t ntfs_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
		unsigned long nr_segs, loff_t pos)
{
	struct file *file = iocb->ki_filp;
	struct address_space *mapping = file->f_mapping;
	struct inode *inode = mapping->host;
	ssize_t ret;

	BUG_ON(iocb->ki_pos != pos);

	mutex_lock(&inode->i_mutex);
	ret = ntfs_file_aio_write_nolock(iocb, iov, nr_segs, &iocb->ki_pos);
	mutex_unlock(&inode->i_mutex);
	if (ret > 0) {
		int err = generic_write_sync(file, iocb->ki_pos - ret, ret);
		if (err < 0)
			ret = err;
	}
	return ret;
}

/**
 * ntfs_file_fsync - sync a file to disk
 * @filp:	file to be synced
 * @datasync:	if non-zero only flush user data and not metadata
 *
 * Data integrity sync of a file to disk.  Used for fsync, fdatasync, and msync
 * system calls.  This function is inspired by fs/buffer.c::file_fsync().
 *
 * If @datasync is false, write the mft record and all associated extent mft
 * records as well as the $DATA attribute and then sync the block device.
 *
 * If @datasync is true and the attribute is non-resident, we skip the writing
 * of the mft record and all associated extent mft records (this might still
 * happen due to the write_inode_now() call).
 *
 * Also, if @datasync is true, we do not wait on the inode to be written out
 * but we always wait on the page cache pages to be written out.
 *
 * Locking: Caller must hold i_mutex on the inode.
 *
 * TODO: We should probably also write all attribute/index inodes associated
 * with this inode but since we have no simple way of getting to them we ignore
 * this problem for now.
 */
static int ntfs_file_fsync(struct file *filp, loff_t start, loff_t end,
			   int datasync)
{
	struct inode *vi = filp->f_mapping->host;
	int err, ret = 0;

	ntfs_debug("Entering for inode 0x%lx.", vi->i_ino);

	err = filemap_write_and_wait_range(vi->i_mapping, start, end);
	if (err)
		return err;
	mutex_lock(&vi->i_mutex);

	BUG_ON(S_ISDIR(vi->i_mode));
	if (!datasync || !NInoNonResident(NTFS_I(vi)))
		ret = __ntfs_write_inode(vi, 1);
	write_inode_now(vi, !datasync);
	/*
	 * NOTE: If we were to use mapping->private_list (see ext2 and
	 * fs/buffer.c) for dirty blocks then we could optimize the below to be
	 * sync_mapping_buffers(vi->i_mapping).
	 */
	err = sync_blockdev(vi->i_sb->s_bdev);
	if (unlikely(err && !ret))
		ret = err;
	if (likely(!ret))
		ntfs_debug("Done.");
	else
		ntfs_warning(vi->i_sb, "Failed to f%ssync inode 0x%lx.  Error "
				"%u.", datasync ? "data" : "", vi->i_ino, -ret);
	mutex_unlock(&vi->i_mutex);
	return ret;
}

#endif /* NTFS_RW */

const struct file_operations ntfs_file_ops = {
	.llseek		= generic_file_llseek,	 /* Seek inside file. */
	.read		= do_sync_read,		 /* Read from file. */
	.aio_read	= generic_file_aio_read, /* Async read from file. */
#ifdef NTFS_RW
	.write		= do_sync_write,	 /* Write to file. */
	.aio_write	= ntfs_file_aio_write,	 /* Async write to file. */
	/*.release	= ,*/			 /* Last file is closed.  See
						    fs/ext2/file.c::
						    ext2_release_file() for
						    how to use this to discard
						    preallocated space for
						    write opened files. */
	.fsync		= ntfs_file_fsync,	 /* Sync a file to disk. */
	/*.aio_fsync	= ,*/			 /* Sync all outstanding async
						    i/o operations on a
						    kiocb. */
#endif /* NTFS_RW */
	/*.ioctl	= ,*/			 /* Perform function on the
						    mounted filesystem. */
	.mmap		= generic_file_mmap,	 /* Mmap file. */
	.open		= ntfs_file_open,	 /* Open file. */
	.splice_read	= generic_file_splice_read /* Zero-copy data send with
						    the data source being on
						    the ntfs partition.  We do
						    not need to care about the
						    data destination. */
	/*.sendpage	= ,*/			 /* Zero-copy data send with
						    the data destination being
						    on the ntfs partition.  We
						    do not need to care about
						    the data source. */
};

const struct inode_operations ntfs_file_inode_ops = {
#ifdef NTFS_RW
	.setattr	= ntfs_setattr,
#endif /* NTFS_RW */
};

const struct file_operations ntfs_empty_file_ops = {};

const struct inode_operations ntfs_empty_inode_ops = {};