aboutsummaryrefslogtreecommitdiff
path: root/fs/locks.c
blob: 909eab8fb1d09ba157f578a4817fefb7d0937c36 (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
2244
2245
2246
/*
 *  linux/fs/locks.c
 *
 *  Provide support for fcntl()'s F_GETLK, F_SETLK, and F_SETLKW calls.
 *  Doug Evans (dje@spiff.uucp), August 07, 1992
 *
 *  Deadlock detection added.
 *  FIXME: one thing isn't handled yet:
 *	- mandatory locks (requires lots of changes elsewhere)
 *  Kelly Carmichael (kelly@[142.24.8.65]), September 17, 1994.
 *
 *  Miscellaneous edits, and a total rewrite of posix_lock_file() code.
 *  Kai Petzke (wpp@marie.physik.tu-berlin.de), 1994
 *  
 *  Converted file_lock_table to a linked list from an array, which eliminates
 *  the limits on how many active file locks are open.
 *  Chad Page (pageone@netcom.com), November 27, 1994
 * 
 *  Removed dependency on file descriptors. dup()'ed file descriptors now
 *  get the same locks as the original file descriptors, and a close() on
 *  any file descriptor removes ALL the locks on the file for the current
 *  process. Since locks still depend on the process id, locks are inherited
 *  after an exec() but not after a fork(). This agrees with POSIX, and both
 *  BSD and SVR4 practice.
 *  Andy Walker (andy@lysaker.kvaerner.no), February 14, 1995
 *
 *  Scrapped free list which is redundant now that we allocate locks
 *  dynamically with kmalloc()/kfree().
 *  Andy Walker (andy@lysaker.kvaerner.no), February 21, 1995
 *
 *  Implemented two lock personalities - FL_FLOCK and FL_POSIX.
 *
 *  FL_POSIX locks are created with calls to fcntl() and lockf() through the
 *  fcntl() system call. They have the semantics described above.
 *
 *  FL_FLOCK locks are created with calls to flock(), through the flock()
 *  system call, which is new. Old C libraries implement flock() via fcntl()
 *  and will continue to use the old, broken implementation.
 *
 *  FL_FLOCK locks follow the 4.4 BSD flock() semantics. They are associated
 *  with a file pointer (filp). As a result they can be shared by a parent
 *  process and its children after a fork(). They are removed when the last
 *  file descriptor referring to the file pointer is closed (unless explicitly
 *  unlocked). 
 *
 *  FL_FLOCK locks never deadlock, an existing lock is always removed before
 *  upgrading from shared to exclusive (or vice versa). When this happens
 *  any processes blocked by the current lock are woken up and allowed to
 *  run before the new lock is applied.
 *  Andy Walker (andy@lysaker.kvaerner.no), June 09, 1995
 *
 *  Removed some race conditions in flock_lock_file(), marked other possible
 *  races. Just grep for FIXME to see them. 
 *  Dmitry Gorodchanin (pgmdsg@ibi.com), February 09, 1996.
 *
 *  Addressed Dmitry's concerns. Deadlock checking no longer recursive.
 *  Lock allocation changed to GFP_ATOMIC as we can't afford to sleep
 *  once we've checked for blocking and deadlocking.
 *  Andy Walker (andy@lysaker.kvaerner.no), April 03, 1996.
 *
 *  Initial implementation of mandatory locks. SunOS turned out to be
 *  a rotten model, so I implemented the "obvious" semantics.
 *  See 'Documentation/mandatory.txt' for details.
 *  Andy Walker (andy@lysaker.kvaerner.no), April 06, 1996.
 *
 *  Don't allow mandatory locks on mmap()'ed files. Added simple functions to
 *  check if a file has mandatory locks, used by mmap(), open() and creat() to
 *  see if system call should be rejected. Ref. HP-UX/SunOS/Solaris Reference
 *  Manual, Section 2.
 *  Andy Walker (andy@lysaker.kvaerner.no), April 09, 1996.
 *
 *  Tidied up block list handling. Added '/proc/locks' interface.
 *  Andy Walker (andy@lysaker.kvaerner.no), April 24, 1996.
 *
 *  Fixed deadlock condition for pathological code that mixes calls to
 *  flock() and fcntl().
 *  Andy Walker (andy@lysaker.kvaerner.no), April 29, 1996.
 *
 *  Allow only one type of locking scheme (FL_POSIX or FL_FLOCK) to be in use
 *  for a given file at a time. Changed the CONFIG_LOCK_MANDATORY scheme to
 *  guarantee sensible behaviour in the case where file system modules might
 *  be compiled with different options than the kernel itself.
 *  Andy Walker (andy@lysaker.kvaerner.no), May 15, 1996.
 *
 *  Added a couple of missing wake_up() calls. Thanks to Thomas Meckel
 *  (Thomas.Meckel@mni.fh-giessen.de) for spotting this.
 *  Andy Walker (andy@lysaker.kvaerner.no), May 15, 1996.
 *
 *  Changed FL_POSIX locks to use the block list in the same way as FL_FLOCK
 *  locks. Changed process synchronisation to avoid dereferencing locks that
 *  have already been freed.
 *  Andy Walker (andy@lysaker.kvaerner.no), Sep 21, 1996.
 *
 *  Made the block list a circular list to minimise searching in the list.
 *  Andy Walker (andy@lysaker.kvaerner.no), Sep 25, 1996.
 *
 *  Made mandatory locking a mount option. Default is not to allow mandatory
 *  locking.
 *  Andy Walker (andy@lysaker.kvaerner.no), Oct 04, 1996.
 *
 *  Some adaptations for NFS support.
 *  Olaf Kirch (okir@monad.swb.de), Dec 1996,
 *
 *  Fixed /proc/locks interface so that we can't overrun the buffer we are handed.
 *  Andy Walker (andy@lysaker.kvaerner.no), May 12, 1997.
 *
 *  Use slab allocator instead of kmalloc/kfree.
 *  Use generic list implementation from <linux/list.h>.
 *  Sped up posix_locks_deadlock by only considering blocked locks.
 *  Matthew Wilcox <willy@debian.org>, March, 2000.
 *
 *  Leases and LOCK_MAND
 *  Matthew Wilcox <willy@debian.org>, June, 2000.
 *  Stephen Rothwell <sfr@canb.auug.org.au>, June, 2000.
 */

#include <linux/capability.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/security.h>
#include <linux/slab.h>
#include <linux/smp_lock.h>
#include <linux/syscalls.h>
#include <linux/time.h>
#include <linux/rcupdate.h>

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

#define IS_POSIX(fl)	(fl->fl_flags & FL_POSIX)
#define IS_FLOCK(fl)	(fl->fl_flags & FL_FLOCK)
#define IS_LEASE(fl)	(fl->fl_flags & FL_LEASE)

int leases_enable = 1;
int lease_break_time = 45;

#define for_each_lock(inode, lockp) \
	for (lockp = &inode->i_flock; *lockp != NULL; lockp = &(*lockp)->fl_next)

LIST_HEAD(file_lock_list);

EXPORT_SYMBOL(file_lock_list);

static LIST_HEAD(blocked_list);

static kmem_cache_t *filelock_cache;

/* Allocate an empty lock structure. */
static struct file_lock *locks_alloc_lock(void)
{
	return kmem_cache_alloc(filelock_cache, SLAB_KERNEL);
}

/* Free a lock which is not in use. */
static void locks_free_lock(struct file_lock *fl)
{
	if (fl == NULL) {
		BUG();
		return;
	}
	if (waitqueue_active(&fl->fl_wait))
		panic("Attempting to free lock with active wait queue");

	if (!list_empty(&fl->fl_block))
		panic("Attempting to free lock with active block list");

	if (!list_empty(&fl->fl_link))
		panic("Attempting to free lock on active lock list");

	if (fl->fl_ops) {
		if (fl->fl_ops->fl_release_private)
			fl->fl_ops->fl_release_private(fl);
		fl->fl_ops = NULL;
	}

	if (fl->fl_lmops) {
		if (fl->fl_lmops->fl_release_private)
			fl->fl_lmops->fl_release_private(fl);
		fl->fl_lmops = NULL;
	}

	kmem_cache_free(filelock_cache, fl);
}

void locks_init_lock(struct file_lock *fl)
{
	INIT_LIST_HEAD(&fl->fl_link);
	INIT_LIST_HEAD(&fl->fl_block);
	init_waitqueue_head(&fl->fl_wait);
	fl->fl_next = NULL;
	fl->fl_fasync = NULL;
	fl->fl_owner = NULL;
	fl->fl_pid = 0;
	fl->fl_file = NULL;
	fl->fl_flags = 0;
	fl->fl_type = 0;
	fl->fl_start = fl->fl_end = 0;
	fl->fl_ops = NULL;
	fl->fl_lmops = NULL;
}

EXPORT_SYMBOL(locks_init_lock);

/*
 * Initialises the fields of the file lock which are invariant for
 * free file_locks.
 */
static void init_once(void *foo, kmem_cache_t *cache, unsigned long flags)
{
	struct file_lock *lock = (struct file_lock *) foo;

	if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) !=
					SLAB_CTOR_CONSTRUCTOR)
		return;

	locks_init_lock(lock);
}

/*
 * Initialize a new lock from an existing file_lock structure.
 */
void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
{
	new->fl_owner = fl->fl_owner;
	new->fl_pid = fl->fl_pid;
	new->fl_file = fl->fl_file;
	new->fl_flags = fl->fl_flags;
	new->fl_type = fl->fl_type;
	new->fl_start = fl->fl_start;
	new->fl_end = fl->fl_end;
	new->fl_ops = fl->fl_ops;
	new->fl_lmops = fl->fl_lmops;
	if (fl->fl_ops && fl->fl_ops->fl_copy_lock)
		fl->fl_ops->fl_copy_lock(new, fl);
	if (fl->fl_lmops && fl->fl_lmops->fl_copy_lock)
		fl->fl_lmops->fl_copy_lock(new, fl);
}

EXPORT_SYMBOL(locks_copy_lock);

static inline int flock_translate_cmd(int cmd) {
	if (cmd & LOCK_MAND)
		return cmd & (LOCK_MAND | LOCK_RW);
	switch (cmd) {
	case LOCK_SH:
		return F_RDLCK;
	case LOCK_EX:
		return F_WRLCK;
	case LOCK_UN:
		return F_UNLCK;
	}
	return -EINVAL;
}

/* Fill in a file_lock structure with an appropriate FLOCK lock. */
static int flock_make_lock(struct file *filp, struct file_lock **lock,
		unsigned int cmd)
{
	struct file_lock *fl;
	int type = flock_translate_cmd(cmd);
	if (type < 0)
		return type;
	
	fl = locks_alloc_lock();
	if (fl == NULL)
		return -ENOMEM;

	fl->fl_file = filp;
	fl->fl_pid = current->tgid;
	fl->fl_flags = FL_FLOCK;
	fl->fl_type = type;
	fl->fl_end = OFFSET_MAX;
	
	*lock = fl;
	return 0;
}

static int assign_type(struct file_lock *fl, int type)
{
	switch (type) {
	case F_RDLCK:
	case F_WRLCK:
	case F_UNLCK:
		fl->fl_type = type;
		break;
	default:
		return -EINVAL;
	}
	return 0;
}

/* Verify a "struct flock" and copy it to a "struct file_lock" as a POSIX
 * style lock.
 */
static int flock_to_posix_lock(struct file *filp, struct file_lock *fl,
			       struct flock *l)
{
	off_t start, end;

	switch (l->l_whence) {
	case 0: /*SEEK_SET*/
		start = 0;
		break;
	case 1: /*SEEK_CUR*/
		start = filp->f_pos;
		break;
	case 2: /*SEEK_END*/
		start = i_size_read(filp->f_dentry->d_inode);
		break;
	default:
		return -EINVAL;
	}

	/* POSIX-1996 leaves the case l->l_len < 0 undefined;
	   POSIX-2001 defines it. */
	start += l->l_start;
	if (start < 0)
		return -EINVAL;
	fl->fl_end = OFFSET_MAX;
	if (l->l_len > 0) {
		end = start + l->l_len - 1;
		fl->fl_end = end;
	} else if (l->l_len < 0) {
		end = start - 1;
		fl->fl_end = end;
		start += l->l_len;
		if (start < 0)
			return -EINVAL;
	}
	fl->fl_start = start;	/* we record the absolute position */
	if (fl->fl_end < fl->fl_start)
		return -EOVERFLOW;
	
	fl->fl_owner = current->files;
	fl->fl_pid = current->tgid;
	fl->fl_file = filp;
	fl->fl_flags = FL_POSIX;
	fl->fl_ops = NULL;
	fl->fl_lmops = NULL;

	return assign_type(fl, l->l_type);
}

#if BITS_PER_LONG == 32
static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
				 struct flock64 *l)
{
	loff_t start;

	switch (l->l_whence) {
	case 0: /*SEEK_SET*/
		start = 0;
		break;
	case 1: /*SEEK_CUR*/
		start = filp->f_pos;
		break;
	case 2: /*SEEK_END*/
		start = i_size_read(filp->f_dentry->d_inode);
		break;
	default:
		return -EINVAL;
	}

	start += l->l_start;
	if (start < 0)
		return -EINVAL;
	fl->fl_end = OFFSET_MAX;
	if (l->l_len > 0) {
		fl->fl_end = start + l->l_len - 1;
	} else if (l->l_len < 0) {
		fl->fl_end = start - 1;
		start += l->l_len;
		if (start < 0)
			return -EINVAL;
	}
	fl->fl_start = start;	/* we record the absolute position */
	if (fl->fl_end < fl->fl_start)
		return -EOVERFLOW;
	
	fl->fl_owner = current->files;
	fl->fl_pid = current->tgid;
	fl->fl_file = filp;
	fl->fl_flags = FL_POSIX;
	fl->fl_ops = NULL;
	fl->fl_lmops = NULL;

	switch (l->l_type) {
	case F_RDLCK:
	case F_WRLCK:
	case F_UNLCK:
		fl->fl_type = l->l_type;
		break;
	default:
		return -EINVAL;
	}

	return (0);
}
#endif

/* default lease lock manager operations */
static void lease_break_callback(struct file_lock *fl)
{
	kill_fasync(&fl->fl_fasync, SIGIO, POLL_MSG);
}

static void lease_release_private_callback(struct file_lock *fl)
{
	if (!fl->fl_file)
		return;

	f_delown(fl->fl_file);
	fl->fl_file->f_owner.signum = 0;
}

static int lease_mylease_callback(struct file_lock *fl, struct file_lock *try)
{
	return fl->fl_file == try->fl_file;
}

static struct lock_manager_operations lease_manager_ops = {
	.fl_break = lease_break_callback,
	.fl_release_private = lease_release_private_callback,
	.fl_mylease = lease_mylease_callback,
	.fl_change = lease_modify,
};

/*
 * Initialize a lease, use the default lock manager operations
 */
static int lease_init(struct file *filp, int type, struct file_lock *fl)
 {
	fl->fl_owner = current->files;
	fl->fl_pid = current->tgid;

	fl->fl_file = filp;
	fl->fl_flags = FL_LEASE;
	if (assign_type(fl, type) != 0) {
		locks_free_lock(fl);
		return -EINVAL;
	}
	fl->fl_start = 0;
	fl->fl_end = OFFSET_MAX;
	fl->fl_ops = NULL;
	fl->fl_lmops = &lease_manager_ops;
	return 0;
}

/* Allocate a file_lock initialised to this type of lease */
static int lease_alloc(struct file *filp, int type, struct file_lock **flp)
{
	struct file_lock *fl = locks_alloc_lock();
	int error;

	if (fl == NULL)
		return -ENOMEM;

	error = lease_init(filp, type, fl);
	if (error)
		return error;
	*flp = fl;
	return 0;
}

/* Check if two locks overlap each other.
 */
static inline int locks_overlap(struct file_lock *fl1, struct file_lock *fl2)
{
	return ((fl1->fl_end >= fl2->fl_start) &&
		(fl2->fl_end >= fl1->fl_start));
}

/*
 * Check whether two locks have the same owner.
 */
static int posix_same_owner(struct file_lock *fl1, struct file_lock *fl2)
{
	if (fl1->fl_lmops && fl1->fl_lmops->fl_compare_owner)
		return fl2->fl_lmops == fl1->fl_lmops &&
			fl1->fl_lmops->fl_compare_owner(fl1, fl2);
	return fl1->fl_owner == fl2->fl_owner;
}

/* Remove waiter from blocker's block list.
 * When blocker ends up pointing to itself then the list is empty.
 */
static void __locks_delete_block(struct file_lock *waiter)
{
	list_del_init(&waiter->fl_block);
	list_del_init(&waiter->fl_link);
	waiter->fl_next = NULL;
}

/*
 */
static void locks_delete_block(struct file_lock *waiter)
{
	lock_kernel();
	__locks_delete_block(waiter);
	unlock_kernel();
}

/* Insert waiter into blocker's block list.
 * We use a circular list so that processes can be easily woken up in
 * the order they blocked. The documentation doesn't require this but
 * it seems like the reasonable thing to do.
 */
static void locks_insert_block(struct file_lock *blocker, 
			       struct file_lock *waiter)
{
	if (!list_empty(&waiter->fl_block)) {
		printk(KERN_ERR "locks_insert_block: removing duplicated lock "
			"(pid=%d %Ld-%Ld type=%d)\n", waiter->fl_pid,
			waiter->fl_start, waiter->fl_end, waiter->fl_type);
		__locks_delete_block(waiter);
	}
	list_add_tail(&waiter->fl_block, &blocker->fl_block);
	waiter->fl_next = blocker;
	if (IS_POSIX(blocker))
		list_add(&waiter->fl_link, &blocked_list);
}

/* Wake up processes blocked waiting for blocker.
 * If told to wait then schedule the processes until the block list
 * is empty, otherwise empty the block list ourselves.
 */
static void locks_wake_up_blocks(struct file_lock *blocker)
{
	while (!list_empty(&blocker->fl_block)) {
		struct file_lock *waiter = list_entry(blocker->fl_block.next,
				struct file_lock, fl_block);
		__locks_delete_block(waiter);
		if (waiter->fl_lmops && waiter->fl_lmops->fl_notify)
			waiter->fl_lmops->fl_notify(waiter);
		else
			wake_up(&waiter->fl_wait);
	}
}

/* Insert file lock fl into an inode's lock list at the position indicated
 * by pos. At the same time add the lock to the global file lock list.
 */
static void locks_insert_lock(struct file_lock **pos, struct file_lock *fl)
{
	list_add(&fl->fl_link, &file_lock_list);

	/* insert into file's list */
	fl->fl_next = *pos;
	*pos = fl;

	if (fl->fl_ops && fl->fl_ops->fl_insert)
		fl->fl_ops->fl_insert(fl);
}

/*
 * Delete a lock and then free it.
 * Wake up processes that are blocked waiting for this lock,
 * notify the FS that the lock has been cleared and
 * finally free the lock.
 */
static void locks_delete_lock(struct file_lock **thisfl_p)
{
	struct file_lock *fl = *thisfl_p;

	*thisfl_p = fl->fl_next;
	fl->fl_next = NULL;
	list_del_init(&fl->fl_link);

	fasync_helper(0, fl->fl_file, 0, &fl->fl_fasync);
	if (fl->fl_fasync != NULL) {
		printk(KERN_ERR "locks_delete_lock: fasync == %p\n", fl->fl_fasync);
		fl->fl_fasync = NULL;
	}

	if (fl->fl_ops && fl->fl_ops->fl_remove)
		fl->fl_ops->fl_remove(fl);

	locks_wake_up_blocks(fl);
	locks_free_lock(fl);
}

/* Determine if lock sys_fl blocks lock caller_fl. Common functionality
 * checks for shared/exclusive status of overlapping locks.
 */
static int locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
{
	if (sys_fl->fl_type == F_WRLCK)
		return 1;
	if (caller_fl->fl_type == F_WRLCK)
		return 1;
	return 0;
}

/* Determine if lock sys_fl blocks lock caller_fl. POSIX specific
 * checking before calling the locks_conflict().
 */
static int posix_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
{
	/* POSIX locks owned by the same process do not conflict with
	 * each other.
	 */
	if (!IS_POSIX(sys_fl) || posix_same_owner(caller_fl, sys_fl))
		return (0);

	/* Check whether they overlap */
	if (!locks_overlap(caller_fl, sys_fl))
		return 0;

	return (locks_conflict(caller_fl, sys_fl));
}

/* Determine if lock sys_fl blocks lock caller_fl. FLOCK specific
 * checking before calling the locks_conflict().
 */
static int flock_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
{
	/* FLOCK locks referring to the same filp do not conflict with
	 * each other.
	 */
	if (!IS_FLOCK(sys_fl) || (caller_fl->fl_file == sys_fl->fl_file))
		return (0);
	if ((caller_fl->fl_type & LOCK_MAND) || (sys_fl->fl_type & LOCK_MAND))
		return 0;

	return (locks_conflict(caller_fl, sys_fl));
}

static int interruptible_sleep_on_locked(wait_queue_head_t *fl_wait, int timeout)
{
	int result = 0;
	DECLARE_WAITQUEUE(wait, current);

	__set_current_state(TASK_INTERRUPTIBLE);
	add_wait_queue(fl_wait, &wait);
	if (timeout == 0)
		schedule();
	else
		result = schedule_timeout(timeout);
	if (signal_pending(current))
		result = -ERESTARTSYS;
	remove_wait_queue(fl_wait, &wait);
	__set_current_state(TASK_RUNNING);
	return result;
}

static int locks_block_on_timeout(struct file_lock *blocker, struct file_lock *waiter, int time)
{
	int result;
	locks_insert_block(blocker, waiter);
	result = interruptible_sleep_on_locked(&waiter->fl_wait, time);
	__locks_delete_block(waiter);
	return result;
}

struct file_lock *
posix_test_lock(struct file *filp, struct file_lock *fl)
{
	struct file_lock *cfl;

	lock_kernel();
	for (cfl = filp->f_dentry->d_inode->i_flock; cfl; cfl = cfl->fl_next) {
		if (!IS_POSIX(cfl))
			continue;
		if (posix_locks_conflict(cfl, fl))
			break;
	}
	unlock_kernel();

	return (cfl);
}

EXPORT_SYMBOL(posix_test_lock);

/* This function tests for deadlock condition before putting a process to
 * sleep. The detection scheme is no longer recursive. Recursive was neat,
 * but dangerous - we risked stack corruption if the lock data was bad, or
 * if the recursion was too deep for any other reason.
 *
 * We rely on the fact that a task can only be on one lock's wait queue
 * at a time. When we find blocked_task on a wait queue we can re-search
 * with blocked_task equal to that queue's owner, until either blocked_task
 * isn't found, or blocked_task is found on a queue owned by my_task.
 *
 * Note: the above assumption may not be true when handling lock requests
 * from a broken NFS client. But broken NFS clients have a lot more to
 * worry about than proper deadlock detection anyway... --okir
 */
int posix_locks_deadlock(struct file_lock *caller_fl,
				struct file_lock *block_fl)
{
	struct list_head *tmp;

next_task:
	if (posix_same_owner(caller_fl, block_fl))
		return 1;
	list_for_each(tmp, &blocked_list) {
		struct file_lock *fl = list_entry(tmp, struct file_lock, fl_link);
		if (posix_same_owner(fl, block_fl)) {
			fl = fl->fl_next;
			block_fl = fl;
			goto next_task;
		}
	}
	return 0;
}

EXPORT_SYMBOL(posix_locks_deadlock);

/* Try to create a FLOCK lock on filp. We always insert new FLOCK locks
 * at the head of the list, but that's secret knowledge known only to
 * flock_lock_file and posix_lock_file.
 */
static int flock_lock_file(struct file *filp, struct file_lock *new_fl)
{
	struct file_lock **before;
	struct inode * inode = filp->f_dentry->d_inode;
	int error = 0;
	int found = 0;

	lock_kernel();
	for_each_lock(inode, before) {
		struct file_lock *fl = *before;
		if (IS_POSIX(fl))
			break;
		if (IS_LEASE(fl))
			continue;
		if (filp != fl->fl_file)
			continue;
		if (new_fl->fl_type == fl->fl_type)
			goto out;
		found = 1;
		locks_delete_lock(before);
		break;
	}
	unlock_kernel();

	if (new_fl->fl_type == F_UNLCK)
		return 0;

	/*
	 * If a higher-priority process was blocked on the old file lock,
	 * give it the opportunity to lock the file.
	 */
	if (found)
		cond_resched();

	lock_kernel();
	for_each_lock(inode, before) {
		struct file_lock *fl = *before;
		if (IS_POSIX(fl))
			break;
		if (IS_LEASE(fl))
			continue;
		if (!flock_locks_conflict(new_fl, fl))
			continue;
		error = -EAGAIN;
		if (new_fl->fl_flags & FL_SLEEP) {
			locks_insert_block(fl, new_fl);
		}
		goto out;
	}
	locks_insert_lock(&inode->i_flock, new_fl);
	error = 0;

out:
	unlock_kernel();
	return error;
}

EXPORT_SYMBOL(posix_lock_file);

static int __posix_lock_file(struct inode *inode, struct file_lock *request)
{
	struct file_lock *fl;
	struct file_lock *new_fl, *new_fl2;
	struct file_lock *left = NULL;
	struct file_lock *right = NULL;
	struct file_lock **before;
	int error, added = 0;

	/*
	 * We may need two file_lock structures for this operation,
	 * so we get them in advance to avoid races.
	 */
	new_fl = locks_alloc_lock();
	new_fl2 = locks_alloc_lock();

	lock_kernel();
	if (request->fl_type != F_UNLCK) {
		for_each_lock(inode, before) {
			struct file_lock *fl = *before;
			if (!IS_POSIX(fl))
				continue;
			if (!posix_locks_conflict(request, fl))
				continue;
			error = -EAGAIN;
			if (!(request->fl_flags & FL_SLEEP))
				goto out;
			error = -EDEADLK;
			if (posix_locks_deadlock(request, fl))
				goto out;
			error = -EAGAIN;
			locks_insert_block(fl, request);
			goto out;
  		}
  	}

	/* If we're just looking for a conflict, we're done. */
	error = 0;
	if (request->fl_flags & FL_ACCESS)
		goto out;

	error = -ENOLCK; /* "no luck" */
	if (!(new_fl && new_fl2))
		goto out;

	/*
	 * We've allocated the new locks in advance, so there are no
	 * errors possible (and no blocking operations) from here on.
	 * 
	 * Find the first old lock with the same owner as the new lock.
	 */
	
	before = &inode->i_flock;

	/* First skip locks owned by other processes.  */
	while ((fl = *before) && (!IS_POSIX(fl) ||
				  !posix_same_owner(request, fl))) {
		before = &fl->fl_next;
	}

	/* Process locks with this owner.  */
	while ((fl = *before) && posix_same_owner(request, fl)) {
		/* Detect adjacent or overlapping regions (if same lock type)
		 */
		if (request->fl_type == fl->fl_type) {
			/* In all comparisons of start vs end, use
			 * "start - 1" rather than "end + 1". If end
			 * is OFFSET_MAX, end + 1 will become negative.
			 */
			if (fl->fl_end < request->fl_start - 1)
				goto next_lock;
			/* If the next lock in the list has entirely bigger
			 * addresses than the new one, insert the lock here.
			 */
			if (fl->fl_start - 1 > request->fl_end)
				break;

			/* If we come here, the new and old lock are of the
			 * same type and adjacent or overlapping. Make one
			 * lock yielding from the lower start address of both
			 * locks to the higher end address.
			 */
			if (fl->fl_start > request->fl_start)
				fl->fl_start = request->fl_start;
			else
				request->fl_start = fl->fl_start;
			if (fl->fl_end < request->fl_end)
				fl->fl_end = request->fl_end;
			else
				request->fl_end = fl->fl_end;
			if (added) {
				locks_delete_lock(before);
				continue;
			}
			request = fl;
			added = 1;
		}
		else {
			/* Processing for different lock types is a bit
			 * more complex.
			 */
			if (fl->fl_end < request->fl_start)
				goto next_lock;
			if (fl->fl_start > request->fl_end)
				break;
			if (request->fl_type == F_UNLCK)
				added = 1;
			if (fl->fl_start < request->fl_start)
				left = fl;
			/* If the next lock in the list has a higher end
			 * address than the new one, insert the new one here.
			 */
			if (fl->fl_end > request->fl_end) {
				right = fl;
				break;
			}
			if (fl->fl_start >= request->fl_start) {
				/* The new lock completely replaces an old
				 * one (This may happen several times).
				 */
				if (added) {
					locks_delete_lock(before);
					continue;
				}
				/* Replace the old lock with the new one.
				 * Wake up anybody waiting for the old one,
				 * as the change in lock type might satisfy
				 * their needs.
				 */
				locks_wake_up_blocks(fl);
				fl->fl_start = request->fl_start;
				fl->fl_end = request->fl_end;
				fl->fl_type = request->fl_type;
				fl->fl_u = request->fl_u;
				request = fl;
				added = 1;
			}
		}
		/* Go on to next lock.
		 */
	next_lock:
		before = &fl->fl_next;
	}

	error = 0;
	if (!added) {
		if (request->fl_type == F_UNLCK)
			goto out;
		locks_copy_lock(new_fl, request);
		locks_insert_lock(before, new_fl);
		new_fl = NULL;
	}
	if (right) {
		if (left == right) {
			/* The new lock breaks the old one in two pieces,
			 * so we have to use the second new lock.
			 */
			left = new_fl2;
			new_fl2 = NULL;
			locks_copy_lock(left, right);
			locks_insert_lock(before, left);
		}
		right->fl_start = request->fl_end + 1;
		locks_wake_up_blocks(right);
	}
	if (left) {
		left->fl_end = request->fl_start - 1;
		locks_wake_up_blocks(left);
	}
 out:
	unlock_kernel();
	/*
	 * Free any unused locks.
	 */
	if (new_fl)
		locks_free_lock(new_fl);
	if (new_fl2)
		locks_free_lock(new_fl2);
	return error;
}

/**
 * posix_lock_file - Apply a POSIX-style lock to a file
 * @filp: The file to apply the lock to
 * @fl: The lock to be applied
 *
 * Add a POSIX style lock to a file.
 * We merge adjacent & overlapping locks whenever possible.
 * POSIX locks are sorted by owner task, then by starting address
 */
int posix_lock_file(struct file *filp, struct file_lock *fl)
{
	return __posix_lock_file(filp->f_dentry->d_inode, fl);
}

/**
 * posix_lock_file_wait - Apply a POSIX-style lock to a file
 * @filp: The file to apply the lock to
 * @fl: The lock to be applied
 *
 * Add a POSIX style lock to a file.
 * We merge adjacent & overlapping locks whenever possible.
 * POSIX locks are sorted by owner task, then by starting address
 */
int posix_lock_file_wait(struct file *filp, struct file_lock *fl)
{
	int error;
	might_sleep ();
	for (;;) {
		error = __posix_lock_file(filp->f_dentry->d_inode, fl);
		if ((error != -EAGAIN) || !(fl->fl_flags & FL_SLEEP))
			break;
		error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
		if (!error)
			continue;

		locks_delete_block(fl);
		break;
	}
	return error;
}
EXPORT_SYMBOL(posix_lock_file_wait);

/**
 * locks_mandatory_locked - Check for an active lock
 * @inode: the file to check
 *
 * Searches the inode's list of locks to find any POSIX locks which conflict.
 * This function is called from locks_verify_locked() only.
 */
int locks_mandatory_locked(struct inode *inode)
{
	fl_owner_t owner = current->files;
	struct file_lock *fl;

	/*
	 * Search the lock list for this inode for any POSIX locks.
	 */
	lock_kernel();
	for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
		if (!IS_POSIX(fl))
			continue;
		if (fl->fl_owner != owner)
			break;
	}
	unlock_kernel();
	return fl ? -EAGAIN : 0;
}

/**
 * locks_mandatory_area - Check for a conflicting lock
 * @read_write: %FLOCK_VERIFY_WRITE for exclusive access, %FLOCK_VERIFY_READ
 *		for shared
 * @inode:      the file to check
 * @filp:       how the file was opened (if it was)
 * @offset:     start of area to check
 * @count:      length of area to check
 *
 * Searches the inode's list of locks to find any POSIX locks which conflict.
 * This function is called from rw_verify_area() and
 * locks_verify_truncate().
 */
int locks_mandatory_area(int read_write, struct inode *inode,
			 struct file *filp, loff_t offset,
			 size_t count)
{
	struct file_lock fl;
	int error;

	locks_init_lock(&fl);
	fl.fl_owner = current->files;
	fl.fl_pid = current->tgid;
	fl.fl_file = filp;
	fl.fl_flags = FL_POSIX | FL_ACCESS;
	if (filp && !(filp->f_flags & O_NONBLOCK))
		fl.fl_flags |= FL_SLEEP;
	fl.fl_type = (read_write == FLOCK_VERIFY_WRITE) ? F_WRLCK : F_RDLCK;
	fl.fl_start = offset;
	fl.fl_end = offset + count - 1;

	for (;;) {
		error = __posix_lock_file(inode, &fl);
		if (error != -EAGAIN)
			break;
		if (!(fl.fl_flags & FL_SLEEP))
			break;
		error = wait_event_interruptible(fl.fl_wait, !fl.fl_next);
		if (!error) {
			/*
			 * If we've been sleeping someone might have
			 * changed the permissions behind our back.
			 */
			if ((inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID)
				continue;
		}

		locks_delete_block(&fl);
		break;
	}

	return error;
}

EXPORT_SYMBOL(locks_mandatory_area);

/* We already had a lease on this file; just change its type */
int lease_modify(struct file_lock **before, int arg)
{
	struct file_lock *fl = *before;
	int error = assign_type(fl, arg);

	if (error)
		return error;
	locks_wake_up_blocks(fl);
	if (arg == F_UNLCK)
		locks_delete_lock(before);
	return 0;
}

EXPORT_SYMBOL(lease_modify);

static void time_out_leases(struct inode *inode)
{
	struct file_lock **before;
	struct file_lock *fl;

	before = &inode->i_flock;
	while ((fl = *before) && IS_LEASE(fl) && (fl->fl_type & F_INPROGRESS)) {
		if ((fl->fl_break_time == 0)
				|| time_before(jiffies, fl->fl_break_time)) {
			before = &fl->fl_next;
			continue;
		}
		lease_modify(before, fl->fl_type & ~F_INPROGRESS);
		if (fl == *before)	/* lease_modify may have freed fl */
			before = &fl->fl_next;
	}
}

/**
 *	__break_lease	-	revoke all outstanding leases on file
 *	@inode: the inode of the file to return
 *	@mode: the open mode (read or write)
 *
 *	break_lease (inlined for speed) has checked there already
 *	is a lease on this file.  Leases are broken on a call to open()
 *	or truncate().  This function can sleep unless you
 *	specified %O_NONBLOCK to your open().
 */
int __break_lease(struct inode *inode, unsigned int mode)
{
	int error = 0, future;
	struct file_lock *new_fl, *flock;
	struct file_lock *fl;
	int alloc_err;
	unsigned long break_time;
	int i_have_this_lease = 0;

	alloc_err = lease_alloc(NULL, mode & FMODE_WRITE ? F_WRLCK : F_RDLCK,
			&new_fl);

	lock_kernel();

	time_out_leases(inode);

	flock = inode->i_flock;
	if ((flock == NULL) || !IS_LEASE(flock))
		goto out;

	for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next)
		if (fl->fl_owner == current->files)
			i_have_this_lease = 1;

	if (mode & FMODE_WRITE) {
		/* If we want write access, we have to revoke any lease. */
		future = F_UNLCK | F_INPROGRESS;
	} else if (flock->fl_type & F_INPROGRESS) {
		/* If the lease is already being broken, we just leave it */
		future = flock->fl_type;
	} else if (flock->fl_type & F_WRLCK) {
		/* Downgrade the exclusive lease to a read-only lease. */
		future = F_RDLCK | F_INPROGRESS;
	} else {
		/* the existing lease was read-only, so we can read too. */
		goto out;
	}

	if (alloc_err && !i_have_this_lease && ((mode & O_NONBLOCK) == 0)) {
		error = alloc_err;
		goto out;
	}

	break_time = 0;
	if (lease_break_time > 0) {
		break_time = jiffies + lease_break_time * HZ;
		if (break_time == 0)
			break_time++;	/* so that 0 means no break time */
	}

	for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next) {
		if (fl->fl_type != future) {
			fl->fl_type = future;
			fl->fl_break_time = break_time;
			/* lease must have lmops break callback */
			fl->fl_lmops->fl_break(fl);
		}
	}

	if (i_have_this_lease || (mode & O_NONBLOCK)) {
		error = -EWOULDBLOCK;
		goto out;
	}

restart:
	break_time = flock->fl_break_time;
	if (break_time != 0) {
		break_time -= jiffies;
		if (break_time == 0)
			break_time++;
	}
	error = locks_block_on_timeout(flock, new_fl, break_time);
	if (error >= 0) {
		if (error == 0)
			time_out_leases(inode);
		/* Wait for the next lease that has not been broken yet */
		for (flock = inode->i_flock; flock && IS_LEASE(flock);
				flock = flock->fl_next) {
			if (flock->fl_type & F_INPROGRESS)
				goto restart;
		}
		error = 0;
	}

out:
	unlock_kernel();
	if (!alloc_err)
		locks_free_lock(new_fl);
	return error;
}

EXPORT_SYMBOL(__break_lease);

/**
 *	lease_get_mtime
 *	@inode: the inode
 *      @time:  pointer to a timespec which will contain the last modified time
 *
 * This is to force NFS clients to flush their caches for files with
 * exclusive leases.  The justification is that if someone has an
 * exclusive lease, then they could be modifiying it.
 */
void lease_get_mtime(struct inode *inode, struct timespec *time)
{
	struct file_lock *flock = inode->i_flock;
	if (flock && IS_LEASE(flock) && (flock->fl_type & F_WRLCK))
		*time = current_fs_time(inode->i_sb);
	else
		*time = inode->i_mtime;
}

EXPORT_SYMBOL(lease_get_mtime);

/**
 *	fcntl_getlease - Enquire what lease is currently active
 *	@filp: the file
 *
 *	The value returned by this function will be one of
 *	(if no lease break is pending):
 *
 *	%F_RDLCK to indicate a shared lease is held.
 *
 *	%F_WRLCK to indicate an exclusive lease is held.
 *
 *	%F_UNLCK to indicate no lease is held.
 *
 *	(if a lease break is pending):
 *
 *	%F_RDLCK to indicate an exclusive lease needs to be
 *		changed to a shared lease (or removed).
 *
 *	%F_UNLCK to indicate the lease needs to be removed.
 *
 *	XXX: sfr & willy disagree over whether F_INPROGRESS
 *	should be returned to userspace.
 */
int fcntl_getlease(struct file *filp)
{
	struct file_lock *fl;
	int type = F_UNLCK;

	lock_kernel();
	time_out_leases(filp->f_dentry->d_inode);
	for (fl = filp->f_dentry->d_inode->i_flock; fl && IS_LEASE(fl);
			fl = fl->fl_next) {
		if (fl->fl_file == filp) {
			type = fl->fl_type & ~F_INPROGRESS;
			break;
		}
	}
	unlock_kernel();
	return type;
}

/**
 *	__setlease	-	sets a lease on an open file
 *	@filp: file pointer
 *	@arg: type of lease to obtain
 *	@flp: input - file_lock to use, output - file_lock inserted
 *
 *	The (input) flp->fl_lmops->fl_break function is required
 *	by break_lease().
 *
 *	Called with kernel lock held.
 */
static int __setlease(struct file *filp, long arg, struct file_lock **flp)
{
	struct file_lock *fl, **before, **my_before = NULL, *lease;
	struct dentry *dentry = filp->f_dentry;
	struct inode *inode = dentry->d_inode;
	int error, rdlease_count = 0, wrlease_count = 0;

	time_out_leases(inode);

	error = -EINVAL;
	if (!flp || !(*flp) || !(*flp)->fl_lmops || !(*flp)->fl_lmops->fl_break)
		goto out;

	lease = *flp;

	error = -EAGAIN;
	if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0))
		goto out;
	if ((arg == F_WRLCK)
	    && ((atomic_read(&dentry->d_count) > 1)
		|| (atomic_read(&inode->i_count) > 1)))
		goto out;

	/*
	 * At this point, we know that if there is an exclusive
	 * lease on this file, then we hold it on this filp
	 * (otherwise our open of this file would have blocked).
	 * And if we are trying to acquire an exclusive lease,
	 * then the file is not open by anyone (including us)
	 * except for this filp.
	 */
	for (before = &inode->i_flock;
			((fl = *before) != NULL) && IS_LEASE(fl);
			before = &fl->fl_next) {
		if (lease->fl_lmops->fl_mylease(fl, lease))
			my_before = before;
		else if (fl->fl_type == (F_INPROGRESS | F_UNLCK))
			/*
			 * Someone is in the process of opening this
			 * file for writing so we may not take an
			 * exclusive lease on it.
			 */
			wrlease_count++;
		else
			rdlease_count++;
	}

	if ((arg == F_RDLCK && (wrlease_count > 0)) ||
	    (arg == F_WRLCK && ((rdlease_count + wrlease_count) > 0)))
		goto out;

	if (my_before != NULL) {
		error = lease->fl_lmops->fl_change(my_before, arg);
		goto out;
	}

	error = 0;
	if (arg == F_UNLCK)
		goto out;

	error = -EINVAL;
	if (!leases_enable)
		goto out;

	error = lease_alloc(filp, arg, &fl);
	if (error)
		goto out;

	locks_copy_lock(fl, lease);

	locks_insert_lock(before, fl);

	*flp = fl;
out:
	return error;
}

 /**
 *	setlease        -       sets a lease on an open file
 *	@filp: file pointer
 *	@arg: type of lease to obtain
 *	@lease: file_lock to use
 *
 *	Call this to establish a lease on the file.
 *	The fl_lmops fl_break function is required by break_lease
 */

int setlease(struct file *filp, long arg, struct file_lock **lease)
{
	struct dentry *dentry = filp->f_dentry;
	struct inode *inode = dentry->d_inode;
	int error;

	if ((current->fsuid != inode->i_uid) && !capable(CAP_LEASE))
		return -EACCES;
	if (!S_ISREG(inode->i_mode))
		return -EINVAL;
	error = security_file_lock(filp, arg);
	if (error)
		return error;

	lock_kernel();
	error = __setlease(filp, arg, lease);
	unlock_kernel();

	return error;
}

EXPORT_SYMBOL(setlease);

/**
 *	fcntl_setlease	-	sets a lease on an open file
 *	@fd: open file descriptor
 *	@filp: file pointer
 *	@arg: type of lease to obtain
 *
 *	Call this fcntl to establish a lease on the file.
 *	Note that you also need to call %F_SETSIG to
 *	receive a signal when the lease is broken.
 */
int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
{
	struct file_lock fl, *flp = &fl;
	struct dentry *dentry = filp->f_dentry;
	struct inode *inode = dentry->d_inode;
	int error;

	if ((current->fsuid != inode->i_uid) && !capable(CAP_LEASE))
		return -EACCES;
	if (!S_ISREG(inode->i_mode))
		return -EINVAL;
	error = security_file_lock(filp, arg);
	if (error)
		return error;

	locks_init_lock(&fl);
	error = lease_init(filp, arg, &fl);
	if (error)
		return error;

	lock_kernel();

	error = __setlease(filp, arg, &flp);
	if (error || arg == F_UNLCK)
		goto out_unlock;

	error = fasync_helper(fd, filp, 1, &flp->fl_fasync);
	if (error < 0) {
		/* remove lease just inserted by __setlease */
		flp->fl_type = F_UNLCK | F_INPROGRESS;
		flp->fl_break_time = jiffies- 10;
		time_out_leases(inode);
		goto out_unlock;
	}

	error = f_setown(filp, current->pid, 0);
out_unlock:
	unlock_kernel();
	return error;
}

/**
 * flock_lock_file_wait - Apply a FLOCK-style lock to a file
 * @filp: The file to apply the lock to
 * @fl: The lock to be applied
 *
 * Add a FLOCK style lock to a file.
 */
int flock_lock_file_wait(struct file *filp, struct file_lock *fl)
{
	int error;
	might_sleep();
	for (;;) {
		error = flock_lock_file(filp, fl);
		if ((error != -EAGAIN) || !(fl->fl_flags & FL_SLEEP))
			break;
		error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
		if (!error)
			continue;

		locks_delete_block(fl);
		break;
	}
	return error;
}

EXPORT_SYMBOL(flock_lock_file_wait);

/**
 *	sys_flock: - flock() system call.
 *	@fd: the file descriptor to lock.
 *	@cmd: the type of lock to apply.
 *
 *	Apply a %FL_FLOCK style lock to an open file descriptor.
 *	The @cmd can be one of
 *
 *	%LOCK_SH -- a shared lock.
 *
 *	%LOCK_EX -- an exclusive lock.
 *
 *	%LOCK_UN -- remove an existing lock.
 *
 *	%LOCK_MAND -- a `mandatory' flock.  This exists to emulate Windows Share Modes.
 *
 *	%LOCK_MAND can be combined with %LOCK_READ or %LOCK_WRITE to allow other
 *	processes read and write access respectively.
 */
asmlinkage long sys_flock(unsigned int fd, unsigned int cmd)
{
	struct file *filp;
	struct file_lock *lock;
	int can_sleep, unlock;
	int error;

	error = -EBADF;
	filp = fget(fd);
	if (!filp)
		goto out;

	can_sleep = !(cmd & LOCK_NB);
	cmd &= ~LOCK_NB;
	unlock = (cmd == LOCK_UN);

	if (!unlock && !(cmd & LOCK_MAND) && !(filp->f_mode & 3))
		goto out_putf;

	error = flock_make_lock(filp, &lock, cmd);
	if (error)
		goto out_putf;
	if (can_sleep)
		lock->fl_flags |= FL_SLEEP;

	error = security_file_lock(filp, cmd);
	if (error)
		goto out_free;

	if (filp->f_op && filp->f_op->flock)
		error = filp->f_op->flock(filp,
					  (can_sleep) ? F_SETLKW : F_SETLK,
					  lock);
	else
		error = flock_lock_file_wait(filp, lock);

 out_free:
	if (list_empty(&lock->fl_link)) {
		locks_free_lock(lock);
	}

 out_putf:
	fput(filp);
 out:
	return error;
}

/* Report the first existing lock that would conflict with l.
 * This implements the F_GETLK command of fcntl().
 */
int fcntl_getlk(struct file *filp, struct flock __user *l)
{
	struct file_lock *fl, file_lock;
	struct flock flock;
	int error;

	error = -EFAULT;
	if (copy_from_user(&flock, l, sizeof(flock)))
		goto out;
	error = -EINVAL;
	if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
		goto out;

	error = flock_to_posix_lock(filp, &file_lock, &flock);
	if (error)
		goto out;

	if (filp->f_op && filp->f_op->lock) {
		error = filp->f_op->lock(filp, F_GETLK, &file_lock);
		if (file_lock.fl_ops && file_lock.fl_ops->fl_release_private)
			file_lock.fl_ops->fl_release_private(&file_lock);
		if (error < 0)
			goto out;
		else
		  fl = (file_lock.fl_type == F_UNLCK ? NULL : &file_lock);
	} else {
		fl = posix_test_lock(filp, &file_lock);
	}
 
	flock.l_type = F_UNLCK;
	if (fl != NULL) {
		flock.l_pid = fl->fl_pid;
#if BITS_PER_LONG == 32
		/*
		 * Make sure we can represent the posix lock via
		 * legacy 32bit flock.
		 */
		error = -EOVERFLOW;
		if (fl->fl_start > OFFT_OFFSET_MAX)
			goto out;
		if ((fl->fl_end != OFFSET_MAX)
		    && (fl->fl_end > OFFT_OFFSET_MAX))
			goto out;
#endif
		flock.l_start = fl->fl_start;
		flock.l_len = fl->fl_end == OFFSET_MAX ? 0 :
			fl->fl_end - fl->fl_start + 1;
		flock.l_whence = 0;
		flock.l_type = fl->fl_type;
	}
	error = -EFAULT;
	if (!copy_to_user(l, &flock, sizeof(flock)))
		error = 0;
out:
	return error;
}

/* Apply the lock described by l to an open file descriptor.
 * This implements both the F_SETLK and F_SETLKW commands of fcntl().
 */
int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
		struct flock __user *l)
{
	struct file_lock *file_lock = locks_alloc_lock();
	struct flock flock;
	struct inode *inode;
	int error;

	if (file_lock == NULL)
		return -ENOLCK;

	/*
	 * This might block, so we do it before checking the inode.
	 */
	error = -EFAULT;
	if (copy_from_user(&flock, l, sizeof(flock)))
		goto out;

	inode = filp->f_dentry->d_inode;

	/* Don't allow mandatory locks on files that may be memory mapped
	 * and shared.
	 */
	if (IS_MANDLOCK(inode) &&
	    (inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID &&
	    mapping_writably_mapped(filp->f_mapping)) {
		error = -EAGAIN;
		goto out;
	}

again:
	error = flock_to_posix_lock(filp, file_lock, &flock);
	if (error)
		goto out;
	if (cmd == F_SETLKW) {
		file_lock->fl_flags |= FL_SLEEP;
	}
	
	error = -EBADF;
	switch (flock.l_type) {
	case F_RDLCK:
		if (!(filp->f_mode & FMODE_READ))
			goto out;
		break;
	case F_WRLCK:
		if (!(filp->f_mode & FMODE_WRITE))
			goto out;
		break;
	case F_UNLCK:
		break;
	default:
		error = -EINVAL;
		goto out;
	}

	error = security_file_lock(filp, file_lock->fl_type);
	if (error)
		goto out;

	if (filp->f_op && filp->f_op->lock != NULL)
		error = filp->f_op->lock(filp, cmd, file_lock);
	else {
		for (;;) {
			error = __posix_lock_file(inode, file_lock);
			if ((error != -EAGAIN) || (cmd == F_SETLK))
				break;
			error = wait_event_interruptible(file_lock->fl_wait,
					!file_lock->fl_next);
			if (!error)
				continue;

			locks_delete_block(file_lock);
			break;
		}
	}

	/*
	 * Attempt to detect a close/fcntl race and recover by
	 * releasing the lock that was just acquired.
	 */
	if (!error && fcheck(fd) != filp && flock.l_type != F_UNLCK) {
		flock.l_type = F_UNLCK;
		goto again;
	}

out:
	locks_free_lock(file_lock);
	return error;
}

#if BITS_PER_LONG == 32
/* Report the first existing lock that would conflict with l.
 * This implements the F_GETLK command of fcntl().
 */
int fcntl_getlk64(struct file *filp, struct flock64 __user *l)
{
	struct file_lock *fl, file_lock;
	struct flock64 flock;
	int error;

	error = -EFAULT;
	if (copy_from_user(&flock, l, sizeof(flock)))
		goto out;
	error = -EINVAL;
	if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
		goto out;

	error = flock64_to_posix_lock(filp, &file_lock, &flock);
	if (error)
		goto out;

	if (filp->f_op && filp->f_op->lock) {
		error = filp->f_op->lock(filp, F_GETLK, &file_lock);
		if (file_lock.fl_ops && file_lock.fl_ops->fl_release_private)
			file_lock.fl_ops->fl_release_private(&file_lock);
		if (error < 0)
			goto out;
		else
		  fl = (file_lock.fl_type == F_UNLCK ? NULL : &file_lock);
	} else {
		fl = posix_test_lock(filp, &file_lock);
	}
 
	flock.l_type = F_UNLCK;
	if (fl != NULL) {
		flock.l_pid = fl->fl_pid;
		flock.l_start = fl->fl_start;
		flock.l_len = fl->fl_end == OFFSET_MAX ? 0 :
			fl->fl_end - fl->fl_start + 1;
		flock.l_whence = 0;
		flock.l_type = fl->fl_type;
	}
	error = -EFAULT;
	if (!copy_to_user(l, &flock, sizeof(flock)))
		error = 0;
  
out:
	return error;
}

/* Apply the lock described by l to an open file descriptor.
 * This implements both the F_SETLK and F_SETLKW commands of fcntl().
 */
int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
		struct flock64 __user *l)
{
	struct file_lock *file_lock = locks_alloc_lock();
	struct flock64 flock;
	struct inode *inode;
	int error;

	if (file_lock == NULL)
		return -ENOLCK;

	/*
	 * This might block, so we do it before checking the inode.
	 */
	error = -EFAULT;
	if (copy_from_user(&flock, l, sizeof(flock)))
		goto out;

	inode = filp->f_dentry->d_inode;

	/* Don't allow mandatory locks on files that may be memory mapped
	 * and shared.
	 */
	if (IS_MANDLOCK(inode) &&
	    (inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID &&
	    mapping_writably_mapped(filp->f_mapping)) {
		error = -EAGAIN;
		goto out;
	}

again:
	error = flock64_to_posix_lock(filp, file_lock, &flock);
	if (error)
		goto out;
	if (cmd == F_SETLKW64) {
		file_lock->fl_flags |= FL_SLEEP;
	}
	
	error = -EBADF;
	switch (flock.l_type) {
	case F_RDLCK:
		if (!(filp->f_mode & FMODE_READ))
			goto out;
		break;
	case F_WRLCK:
		if (!(filp->f_mode & FMODE_WRITE))
			goto out;
		break;
	case F_UNLCK:
		break;
	default:
		error = -EINVAL;
		goto out;
	}

	error = security_file_lock(filp, file_lock->fl_type);
	if (error)
		goto out;

	if (filp->f_op && filp->f_op->lock != NULL)
		error = filp->f_op->lock(filp, cmd, file_lock);
	else {
		for (;;) {
			error = __posix_lock_file(inode, file_lock);
			if ((error != -EAGAIN) || (cmd == F_SETLK64))
				break;
			error = wait_event_interruptible(file_lock->fl_wait,
					!file_lock->fl_next);
			if (!error)
				continue;

			locks_delete_block(file_lock);
			break;
		}
	}

	/*
	 * Attempt to detect a close/fcntl race and recover by
	 * releasing the lock that was just acquired.
	 */
	if (!error && fcheck(fd) != filp && flock.l_type != F_UNLCK) {
		flock.l_type = F_UNLCK;
		goto again;
	}

out:
	locks_free_lock(file_lock);
	return error;
}
#endif /* BITS_PER_LONG == 32 */

/*
 * This function is called when the file is being removed
 * from the task's fd array.  POSIX locks belonging to this task
 * are deleted at this time.
 */
void locks_remove_posix(struct file *filp, fl_owner_t owner)
{
	struct file_lock lock, **before;

	/*
	 * If there are no locks held on this file, we don't need to call
	 * posix_lock_file().  Another process could be setting a lock on this
	 * file at the same time, but we wouldn't remove that lock anyway.
	 */
	before = &filp->f_dentry->d_inode->i_flock;
	if (*before == NULL)
		return;

	lock.fl_type = F_UNLCK;
	lock.fl_flags = FL_POSIX;
	lock.fl_start = 0;
	lock.fl_end = OFFSET_MAX;
	lock.fl_owner = owner;
	lock.fl_pid = current->tgid;
	lock.fl_file = filp;
	lock.fl_ops = NULL;
	lock.fl_lmops = NULL;

	if (filp->f_op && filp->f_op->lock != NULL) {
		filp->f_op->lock(filp, F_SETLK, &lock);
		goto out;
	}

	/* Can't use posix_lock_file here; we need to remove it no matter
	 * which pid we have.
	 */
	lock_kernel();
	while (*before != NULL) {
		struct file_lock *fl = *before;
		if (IS_POSIX(fl) && posix_same_owner(fl, &lock)) {
			locks_delete_lock(before);
			continue;
		}
		before = &fl->fl_next;
	}
	unlock_kernel();
out:
	if (lock.fl_ops && lock.fl_ops->fl_release_private)
		lock.fl_ops->fl_release_private(&lock);
}

EXPORT_SYMBOL(locks_remove_posix);

/*
 * This function is called on the last close of an open file.
 */
void locks_remove_flock(struct file *filp)
{
	struct inode * inode = filp->f_dentry->d_inode; 
	struct file_lock *fl;
	struct file_lock **before;

	if (!inode->i_flock)
		return;

	if (filp->f_op && filp->f_op->flock) {
		struct file_lock fl = {
			.fl_pid = current->tgid,
			.fl_file = filp,
			.fl_flags = FL_FLOCK,
			.fl_type = F_UNLCK,
			.fl_end = OFFSET_MAX,
		};
		filp->f_op->flock(filp, F_SETLKW, &fl);
		if (fl.fl_ops && fl.fl_ops->fl_release_private)
			fl.fl_ops->fl_release_private(&fl);
	}

	lock_kernel();
	before = &inode->i_flock;

	while ((fl = *before) != NULL) {
		if (fl->fl_file == filp) {
			if (IS_FLOCK(fl)) {
				locks_delete_lock(before);
				continue;
			}
			if (IS_LEASE(fl)) {
				lease_modify(before, F_UNLCK);
				continue;
			}
			/* What? */
			BUG();
 		}
		before = &fl->fl_next;
	}
	unlock_kernel();
}

/**
 *	posix_block_lock - blocks waiting for a file lock
 *	@blocker: the lock which is blocking
 *	@waiter: the lock which conflicts and has to wait
 *
 * lockd needs to block waiting for locks.
 */
void
posix_block_lock(struct file_lock *blocker, struct file_lock *waiter)
{
	locks_insert_block(blocker, waiter);
}

EXPORT_SYMBOL(posix_block_lock);

/**
 *	posix_unblock_lock - stop waiting for a file lock
 *      @filp:   how the file was opened
 *	@waiter: the lock which was waiting
 *
 *	lockd needs to block waiting for locks.
 */
int
posix_unblock_lock(struct file *filp, struct file_lock *waiter)
{
	int status = 0;

	lock_kernel();
	if (waiter->fl_next)
		__locks_delete_block(waiter);
	else
		status = -ENOENT;
	unlock_kernel();
	return status;
}

EXPORT_SYMBOL(posix_unblock_lock);

static void lock_get_status(char* out, struct file_lock *fl, int id, char *pfx)
{
	struct inode *inode = NULL;

	if (fl->fl_file != NULL)
		inode = fl->fl_file->f_dentry->d_inode;

	out += sprintf(out, "%d:%s ", id, pfx);
	if (IS_POSIX(fl)) {
		out += sprintf(out, "%6s %s ",
			     (fl->fl_flags & FL_ACCESS) ? "ACCESS" : "POSIX ",
			     (inode == NULL) ? "*NOINODE*" :
			     (IS_MANDLOCK(inode) &&
			      (inode->i_mode & (S_IXGRP | S_ISGID)) == S_ISGID) ?
			     "MANDATORY" : "ADVISORY ");
	} else if (IS_FLOCK(fl)) {
		if (fl->fl_type & LOCK_MAND) {
			out += sprintf(out, "FLOCK  MSNFS     ");
		} else {
			out += sprintf(out, "FLOCK  ADVISORY  ");
		}
	} else if (IS_LEASE(fl)) {
		out += sprintf(out, "LEASE  ");
		if (fl->fl_type & F_INPROGRESS)
			out += sprintf(out, "BREAKING  ");
		else if (fl->fl_file)
			out += sprintf(out, "ACTIVE    ");
		else
			out += sprintf(out, "BREAKER   ");
	} else {
		out += sprintf(out, "UNKNOWN UNKNOWN  ");
	}
	if (fl->fl_type & LOCK_MAND) {
		out += sprintf(out, "%s ",
			       (fl->fl_type & LOCK_READ)
			       ? (fl->fl_type & LOCK_WRITE) ? "RW   " : "READ "
			       : (fl->fl_type & LOCK_WRITE) ? "WRITE" : "NONE ");
	} else {
		out += sprintf(out, "%s ",
			       (fl->fl_type & F_INPROGRESS)
			       ? (fl->fl_type & F_UNLCK) ? "UNLCK" : "READ "
			       : (fl->fl_type & F_WRLCK) ? "WRITE" : "READ ");
	}
	if (inode) {
#ifdef WE_CAN_BREAK_LSLK_NOW
		out += sprintf(out, "%d %s:%ld ", fl->fl_pid,
				inode->i_sb->s_id, inode->i_ino);
#else
		/* userspace relies on this representation of dev_t ;-( */
		out += sprintf(out, "%d %02x:%02x:%ld ", fl->fl_pid,
				MAJOR(inode->i_sb->s_dev),
				MINOR(inode->i_sb->s_dev), inode->i_ino);
#endif
	} else {
		out += sprintf(out, "%d <none>:0 ", fl->fl_pid);
	}
	if (IS_POSIX(fl)) {
		if (fl->fl_end == OFFSET_MAX)
			out += sprintf(out, "%Ld EOF\n", fl->fl_start);
		else
			out += sprintf(out, "%Ld %Ld\n", fl->fl_start,
					fl->fl_end);
	} else {
		out += sprintf(out, "0 EOF\n");
	}
}

static void move_lock_status(char **p, off_t* pos, off_t offset)
{
	int len;
	len = strlen(*p);
	if(*pos >= offset) {
		/* the complete line is valid */
		*p += len;
		*pos += len;
		return;
	}
	if(*pos+len > offset) {
		/* use the second part of the line */
		int i = offset-*pos;
		memmove(*p,*p+i,len-i);
		*p += len-i;
		*pos += len;
		return;
	}
	/* discard the complete line */
	*pos += len;
}

/**
 *	get_locks_status	-	reports lock usage in /proc/locks
 *	@buffer: address in userspace to write into
 *	@start: ?
 *	@offset: how far we are through the buffer
 *	@length: how much to read
 */

int get_locks_status(char *buffer, char **start, off_t offset, int length)
{
	struct list_head *tmp;
	char *q = buffer;
	off_t pos = 0;
	int i = 0;

	lock_kernel();
	list_for_each(tmp, &file_lock_list) {
		struct list_head *btmp;
		struct file_lock *fl = list_entry(tmp, struct file_lock, fl_link);
		lock_get_status(q, fl, ++i, "");
		move_lock_status(&q, &pos, offset);

		if(pos >= offset+length)
			goto done;

		list_for_each(btmp, &fl->fl_block) {
			struct file_lock *bfl = list_entry(btmp,
					struct file_lock, fl_block);
			lock_get_status(q, bfl, i, " ->");
			move_lock_status(&q, &pos, offset);

			if(pos >= offset+length)
				goto done;
		}
	}
done:
	unlock_kernel();
	*start = buffer;
	if(q-buffer < length)
		return (q-buffer);
	return length;
}

/**
 *	lock_may_read - checks that the region is free of locks
 *	@inode: the inode that is being read
 *	@start: the first byte to read
 *	@len: the number of bytes to read
 *
 *	Emulates Windows locking requirements.  Whole-file
 *	mandatory locks (share modes) can prohibit a read and
 *	byte-range POSIX locks can prohibit a read if they overlap.
 *
 *	N.B. this function is only ever called
 *	from knfsd and ownership of locks is never checked.
 */
int lock_may_read(struct inode *inode, loff_t start, unsigned long len)
{
	struct file_lock *fl;
	int result = 1;
	lock_kernel();
	for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
		if (IS_POSIX(fl)) {
			if (fl->fl_type == F_RDLCK)
				continue;
			if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
				continue;
		} else if (IS_FLOCK(fl)) {
			if (!(fl->fl_type & LOCK_MAND))
				continue;
			if (fl->fl_type & LOCK_READ)
				continue;
		} else
			continue;
		result = 0;
		break;
	}
	unlock_kernel();
	return result;
}

EXPORT_SYMBOL(lock_may_read);

/**
 *	lock_may_write - checks that the region is free of locks
 *	@inode: the inode that is being written
 *	@start: the first byte to write
 *	@len: the number of bytes to write
 *
 *	Emulates Windows locking requirements.  Whole-file
 *	mandatory locks (share modes) can prohibit a write and
 *	byte-range POSIX locks can prohibit a write if they overlap.
 *
 *	N.B. this function is only ever called
 *	from knfsd and ownership of locks is never checked.
 */
int lock_may_write(struct inode *inode, loff_t start, unsigned long len)
{
	struct file_lock *fl;
	int result = 1;
	lock_kernel();
	for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
		if (IS_POSIX(fl)) {
			if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
				continue;
		} else if (IS_FLOCK(fl)) {
			if (!(fl->fl_type & LOCK_MAND))
				continue;
			if (fl->fl_type & LOCK_WRITE)
				continue;
		} else
			continue;
		result = 0;
		break;
	}
	unlock_kernel();
	return result;
}

EXPORT_SYMBOL(lock_may_write);

static inline void __steal_locks(struct file *file, fl_owner_t from)
{
	struct inode *inode = file->f_dentry->d_inode;
	struct file_lock *fl = inode->i_flock;

	while (fl) {
		if (fl->fl_file == file && fl->fl_owner == from)
			fl->fl_owner = current->files;
		fl = fl->fl_next;
	}
}

/* When getting ready for executing a binary, we make sure that current
 * has a files_struct on its own. Before dropping the old files_struct,
 * we take over ownership of all locks for all file descriptors we own.
 * Note that we may accidentally steal a lock for a file that a sibling
 * has created since the unshare_files() call.
 */
void steal_locks(fl_owner_t from)
{
	struct files_struct *files = current->files;
	int i, j;
	struct fdtable *fdt;

	if (from == files)
		return;

	lock_kernel();
	j = 0;
	rcu_read_lock();
	fdt = files_fdtable(files);
	for (;;) {
		unsigned long set;
		i = j * __NFDBITS;
		if (i >= fdt->max_fdset || i >= fdt->max_fds)
			break;
		set = fdt->open_fds->fds_bits[j++];
		while (set) {
			if (set & 1) {
				struct file *file = fdt->fd[i];
				if (file)
					__steal_locks(file, from);
			}
			i++;
			set >>= 1;
		}
	}
	rcu_read_unlock();
	unlock_kernel();
}
EXPORT_SYMBOL(steal_locks);

static int __init filelock_init(void)
{
	filelock_cache = kmem_cache_create("file_lock_cache",
			sizeof(struct file_lock), 0, SLAB_PANIC,
			init_once, NULL);
	return 0;
}

core_initcall(filelock_init);