summaryrefslogtreecommitdiff
path: root/fs/ext4/fast_commit.c
blob: 4594b62f147bb988d189a0b00318da7cf135699f (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
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
// SPDX-License-Identifier: GPL-2.0

/*
 * fs/ext4/fast_commit.c
 *
 * Written by Harshad Shirwadkar <harshadshirwadkar@gmail.com>
 *
 * Ext4 fast commits routines.
 */
#include "ext4.h"
#include "ext4_jbd2.h"
#include "ext4_extents.h"
#include "mballoc.h"

/*
 * Ext4 Fast Commits
 * -----------------
 *
 * Ext4 fast commits implement fine grained journalling for Ext4.
 *
 * Fast commits are organized as a log of tag-length-value (TLV) structs. (See
 * struct ext4_fc_tl). Each TLV contains some delta that is replayed TLV by
 * TLV during the recovery phase. For the scenarios for which we currently
 * don't have replay code, fast commit falls back to full commits.
 * Fast commits record delta in one of the following three categories.
 *
 * (A) Directory entry updates:
 *
 * - EXT4_FC_TAG_UNLINK		- records directory entry unlink
 * - EXT4_FC_TAG_LINK		- records directory entry link
 * - EXT4_FC_TAG_CREAT		- records inode and directory entry creation
 *
 * (B) File specific data range updates:
 *
 * - EXT4_FC_TAG_ADD_RANGE	- records addition of new blocks to an inode
 * - EXT4_FC_TAG_DEL_RANGE	- records deletion of blocks from an inode
 *
 * (C) Inode metadata (mtime / ctime etc):
 *
 * - EXT4_FC_TAG_INODE		- record the inode that should be replayed
 *				  during recovery. Note that iblocks field is
 *				  not replayed and instead derived during
 *				  replay.
 * Commit Operation
 * ----------------
 * With fast commits, we maintain all the directory entry operations in the
 * order in which they are issued in an in-memory queue. This queue is flushed
 * to disk during the commit operation. We also maintain a list of inodes
 * that need to be committed during a fast commit in another in memory queue of
 * inodes. During the commit operation, we commit in the following order:
 *
 * [1] Lock inodes for any further data updates by setting COMMITTING state
 * [2] Submit data buffers of all the inodes
 * [3] Wait for [2] to complete
 * [4] Commit all the directory entry updates in the fast commit space
 * [5] Commit all the changed inode structures
 * [6] Write tail tag (this tag ensures the atomicity, please read the following
 *     section for more details).
 * [7] Wait for [4], [5] and [6] to complete.
 *
 * All the inode updates must call ext4_fc_start_update() before starting an
 * update. If such an ongoing update is present, fast commit waits for it to
 * complete. The completion of such an update is marked by
 * ext4_fc_stop_update().
 *
 * Fast Commit Ineligibility
 * -------------------------
 *
 * Not all operations are supported by fast commits today (e.g extended
 * attributes). Fast commit ineligibility is marked by calling
 * ext4_fc_mark_ineligible(): This makes next fast commit operation to fall back
 * to full commit.
 *
 * Atomicity of commits
 * --------------------
 * In order to guarantee atomicity during the commit operation, fast commit
 * uses "EXT4_FC_TAG_TAIL" tag that marks a fast commit as complete. Tail
 * tag contains CRC of the contents and TID of the transaction after which
 * this fast commit should be applied. Recovery code replays fast commit
 * logs only if there's at least 1 valid tail present. For every fast commit
 * operation, there is 1 tail. This means, we may end up with multiple tails
 * in the fast commit space. Here's an example:
 *
 * - Create a new file A and remove existing file B
 * - fsync()
 * - Append contents to file A
 * - Truncate file A
 * - fsync()
 *
 * The fast commit space at the end of above operations would look like this:
 *      [HEAD] [CREAT A] [UNLINK B] [TAIL] [ADD_RANGE A] [DEL_RANGE A] [TAIL]
 *             |<---  Fast Commit 1   --->|<---      Fast Commit 2     ---->|
 *
 * Replay code should thus check for all the valid tails in the FC area.
 *
 * Fast Commit Replay Idempotence
 * ------------------------------
 *
 * Fast commits tags are idempotent in nature provided the recovery code follows
 * certain rules. The guiding principle that the commit path follows while
 * committing is that it stores the result of a particular operation instead of
 * storing the procedure.
 *
 * Let's consider this rename operation: 'mv /a /b'. Let's assume dirent '/a'
 * was associated with inode 10. During fast commit, instead of storing this
 * operation as a procedure "rename a to b", we store the resulting file system
 * state as a "series" of outcomes:
 *
 * - Link dirent b to inode 10
 * - Unlink dirent a
 * - Inode <10> with valid refcount
 *
 * Now when recovery code runs, it needs "enforce" this state on the file
 * system. This is what guarantees idempotence of fast commit replay.
 *
 * Let's take an example of a procedure that is not idempotent and see how fast
 * commits make it idempotent. Consider following sequence of operations:
 *
 *     rm A;    mv B A;    read A
 *  (x)     (y)        (z)
 *
 * (x), (y) and (z) are the points at which we can crash. If we store this
 * sequence of operations as is then the replay is not idempotent. Let's say
 * while in replay, we crash at (z). During the second replay, file A (which was
 * actually created as a result of "mv B A" operation) would get deleted. Thus,
 * file named A would be absent when we try to read A. So, this sequence of
 * operations is not idempotent. However, as mentioned above, instead of storing
 * the procedure fast commits store the outcome of each procedure. Thus the fast
 * commit log for above procedure would be as follows:
 *
 * (Let's assume dirent A was linked to inode 10 and dirent B was linked to
 * inode 11 before the replay)
 *
 *    [Unlink A]   [Link A to inode 11]   [Unlink B]   [Inode 11]
 * (w)          (x)                    (y)          (z)
 *
 * If we crash at (z), we will have file A linked to inode 11. During the second
 * replay, we will remove file A (inode 11). But we will create it back and make
 * it point to inode 11. We won't find B, so we'll just skip that step. At this
 * point, the refcount for inode 11 is not reliable, but that gets fixed by the
 * replay of last inode 11 tag. Crashes at points (w), (x) and (y) get handled
 * similarly. Thus, by converting a non-idempotent procedure into a series of
 * idempotent outcomes, fast commits ensured idempotence during the replay.
 *
 * TODOs
 * -----
 *
 * 0) Fast commit replay path hardening: Fast commit replay code should use
 *    journal handles to make sure all the updates it does during the replay
 *    path are atomic. With that if we crash during fast commit replay, after
 *    trying to do recovery again, we will find a file system where fast commit
 *    area is invalid (because new full commit would be found). In order to deal
 *    with that, fast commit replay code should ensure that the "FC_REPLAY"
 *    superblock state is persisted before starting the replay, so that after
 *    the crash, fast commit recovery code can look at that flag and perform
 *    fast commit recovery even if that area is invalidated by later full
 *    commits.
 *
 * 1) Fast commit's commit path locks the entire file system during fast
 *    commit. This has significant performance penalty. Instead of that, we
 *    should use ext4_fc_start/stop_update functions to start inode level
 *    updates from ext4_journal_start/stop. Once we do that we can drop file
 *    system locking during commit path.
 *
 * 2) Handle more ineligible cases.
 */

#include <trace/events/ext4.h>
static struct kmem_cache *ext4_fc_dentry_cachep;

static void ext4_end_buffer_io_sync(struct buffer_head *bh, int uptodate)
{
	BUFFER_TRACE(bh, "");
	if (uptodate) {
		ext4_debug("%s: Block %lld up-to-date",
			   __func__, bh->b_blocknr);
		set_buffer_uptodate(bh);
	} else {
		ext4_debug("%s: Block %lld not up-to-date",
			   __func__, bh->b_blocknr);
		clear_buffer_uptodate(bh);
	}

	unlock_buffer(bh);
}

static inline void ext4_fc_reset_inode(struct inode *inode)
{
	struct ext4_inode_info *ei = EXT4_I(inode);

	ei->i_fc_lblk_start = 0;
	ei->i_fc_lblk_len = 0;
}

void ext4_fc_init_inode(struct inode *inode)
{
	struct ext4_inode_info *ei = EXT4_I(inode);

	ext4_fc_reset_inode(inode);
	ext4_clear_inode_state(inode, EXT4_STATE_FC_COMMITTING);
	INIT_LIST_HEAD(&ei->i_fc_list);
	INIT_LIST_HEAD(&ei->i_fc_dilist);
	init_waitqueue_head(&ei->i_fc_wait);
	atomic_set(&ei->i_fc_updates, 0);
}

/* This function must be called with sbi->s_fc_lock held. */
static void ext4_fc_wait_committing_inode(struct inode *inode)
__releases(&EXT4_SB(inode->i_sb)->s_fc_lock)
{
	wait_queue_head_t *wq;
	struct ext4_inode_info *ei = EXT4_I(inode);

#if (BITS_PER_LONG < 64)
	DEFINE_WAIT_BIT(wait, &ei->i_state_flags,
			EXT4_STATE_FC_COMMITTING);
	wq = bit_waitqueue(&ei->i_state_flags,
				EXT4_STATE_FC_COMMITTING);
#else
	DEFINE_WAIT_BIT(wait, &ei->i_flags,
			EXT4_STATE_FC_COMMITTING);
	wq = bit_waitqueue(&ei->i_flags,
				EXT4_STATE_FC_COMMITTING);
#endif
	lockdep_assert_held(&EXT4_SB(inode->i_sb)->s_fc_lock);
	prepare_to_wait(wq, &wait.wq_entry, TASK_UNINTERRUPTIBLE);
	spin_unlock(&EXT4_SB(inode->i_sb)->s_fc_lock);
	schedule();
	finish_wait(wq, &wait.wq_entry);
}

static bool ext4_fc_disabled(struct super_block *sb)
{
	return (!test_opt2(sb, JOURNAL_FAST_COMMIT) ||
		(EXT4_SB(sb)->s_mount_state & EXT4_FC_REPLAY));
}

/*
 * Inform Ext4's fast about start of an inode update
 *
 * This function is called by the high level call VFS callbacks before
 * performing any inode update. This function blocks if there's an ongoing
 * fast commit on the inode in question.
 */
void ext4_fc_start_update(struct inode *inode)
{
	struct ext4_inode_info *ei = EXT4_I(inode);

	if (ext4_fc_disabled(inode->i_sb))
		return;

restart:
	spin_lock(&EXT4_SB(inode->i_sb)->s_fc_lock);
	if (list_empty(&ei->i_fc_list))
		goto out;

	if (ext4_test_inode_state(inode, EXT4_STATE_FC_COMMITTING)) {
		ext4_fc_wait_committing_inode(inode);
		goto restart;
	}
out:
	atomic_inc(&ei->i_fc_updates);
	spin_unlock(&EXT4_SB(inode->i_sb)->s_fc_lock);
}

/*
 * Stop inode update and wake up waiting fast commits if any.
 */
void ext4_fc_stop_update(struct inode *inode)
{
	struct ext4_inode_info *ei = EXT4_I(inode);

	if (ext4_fc_disabled(inode->i_sb))
		return;

	if (atomic_dec_and_test(&ei->i_fc_updates))
		wake_up_all(&ei->i_fc_wait);
}

/*
 * Remove inode from fast commit list. If the inode is being committed
 * we wait until inode commit is done.
 */
void ext4_fc_del(struct inode *inode)
{
	struct ext4_inode_info *ei = EXT4_I(inode);
	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
	struct ext4_fc_dentry_update *fc_dentry;

	if (ext4_fc_disabled(inode->i_sb))
		return;

restart:
	spin_lock(&EXT4_SB(inode->i_sb)->s_fc_lock);
	if (list_empty(&ei->i_fc_list) && list_empty(&ei->i_fc_dilist)) {
		spin_unlock(&EXT4_SB(inode->i_sb)->s_fc_lock);
		return;
	}

	if (ext4_test_inode_state(inode, EXT4_STATE_FC_COMMITTING)) {
		ext4_fc_wait_committing_inode(inode);
		goto restart;
	}

	if (!list_empty(&ei->i_fc_list))
		list_del_init(&ei->i_fc_list);

	/*
	 * Since this inode is getting removed, let's also remove all FC
	 * dentry create references, since it is not needed to log it anyways.
	 */
	if (list_empty(&ei->i_fc_dilist)) {
		spin_unlock(&sbi->s_fc_lock);
		return;
	}

	fc_dentry = list_first_entry(&ei->i_fc_dilist, struct ext4_fc_dentry_update, fcd_dilist);
	WARN_ON(fc_dentry->fcd_op != EXT4_FC_TAG_CREAT);
	list_del_init(&fc_dentry->fcd_list);
	list_del_init(&fc_dentry->fcd_dilist);

	WARN_ON(!list_empty(&ei->i_fc_dilist));
	spin_unlock(&sbi->s_fc_lock);

	if (fc_dentry->fcd_name.name &&
		fc_dentry->fcd_name.len > DNAME_INLINE_LEN)
		kfree(fc_dentry->fcd_name.name);
	kmem_cache_free(ext4_fc_dentry_cachep, fc_dentry);

	return;
}

/*
 * Mark file system as fast commit ineligible, and record latest
 * ineligible transaction tid. This means until the recorded
 * transaction, commit operation would result in a full jbd2 commit.
 */
void ext4_fc_mark_ineligible(struct super_block *sb, int reason, handle_t *handle)
{
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	tid_t tid;

	if (ext4_fc_disabled(sb))
		return;

	ext4_set_mount_flag(sb, EXT4_MF_FC_INELIGIBLE);
	if (handle && !IS_ERR(handle))
		tid = handle->h_transaction->t_tid;
	else {
		read_lock(&sbi->s_journal->j_state_lock);
		tid = sbi->s_journal->j_running_transaction ?
				sbi->s_journal->j_running_transaction->t_tid : 0;
		read_unlock(&sbi->s_journal->j_state_lock);
	}
	spin_lock(&sbi->s_fc_lock);
	if (sbi->s_fc_ineligible_tid < tid)
		sbi->s_fc_ineligible_tid = tid;
	spin_unlock(&sbi->s_fc_lock);
	WARN_ON(reason >= EXT4_FC_REASON_MAX);
	sbi->s_fc_stats.fc_ineligible_reason_count[reason]++;
}

/*
 * Generic fast commit tracking function. If this is the first time this we are
 * called after a full commit, we initialize fast commit fields and then call
 * __fc_track_fn() with update = 0. If we have already been called after a full
 * commit, we pass update = 1. Based on that, the track function can determine
 * if it needs to track a field for the first time or if it needs to just
 * update the previously tracked value.
 *
 * If enqueue is set, this function enqueues the inode in fast commit list.
 */
static int ext4_fc_track_template(
	handle_t *handle, struct inode *inode,
	int (*__fc_track_fn)(struct inode *, void *, bool),
	void *args, int enqueue)
{
	bool update = false;
	struct ext4_inode_info *ei = EXT4_I(inode);
	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
	tid_t tid = 0;
	int ret;

	tid = handle->h_transaction->t_tid;
	mutex_lock(&ei->i_fc_lock);
	if (tid == ei->i_sync_tid) {
		update = true;
	} else {
		ext4_fc_reset_inode(inode);
		ei->i_sync_tid = tid;
	}
	ret = __fc_track_fn(inode, args, update);
	mutex_unlock(&ei->i_fc_lock);

	if (!enqueue)
		return ret;

	spin_lock(&sbi->s_fc_lock);
	if (list_empty(&EXT4_I(inode)->i_fc_list))
		list_add_tail(&EXT4_I(inode)->i_fc_list,
				(sbi->s_journal->j_flags & JBD2_FULL_COMMIT_ONGOING ||
				 sbi->s_journal->j_flags & JBD2_FAST_COMMIT_ONGOING) ?
				&sbi->s_fc_q[FC_Q_STAGING] :
				&sbi->s_fc_q[FC_Q_MAIN]);
	spin_unlock(&sbi->s_fc_lock);

	return ret;
}

struct __track_dentry_update_args {
	struct dentry *dentry;
	int op;
};

/* __track_fn for directory entry updates. Called with ei->i_fc_lock. */
static int __track_dentry_update(struct inode *inode, void *arg, bool update)
{
	struct ext4_fc_dentry_update *node;
	struct ext4_inode_info *ei = EXT4_I(inode);
	struct __track_dentry_update_args *dentry_update =
		(struct __track_dentry_update_args *)arg;
	struct dentry *dentry = dentry_update->dentry;
	struct inode *dir = dentry->d_parent->d_inode;
	struct super_block *sb = inode->i_sb;
	struct ext4_sb_info *sbi = EXT4_SB(sb);

	mutex_unlock(&ei->i_fc_lock);

	if (IS_ENCRYPTED(dir)) {
		ext4_fc_mark_ineligible(sb, EXT4_FC_REASON_ENCRYPTED_FILENAME,
					NULL);
		mutex_lock(&ei->i_fc_lock);
		return -EOPNOTSUPP;
	}

	node = kmem_cache_alloc(ext4_fc_dentry_cachep, GFP_NOFS);
	if (!node) {
		ext4_fc_mark_ineligible(sb, EXT4_FC_REASON_NOMEM, NULL);
		mutex_lock(&ei->i_fc_lock);
		return -ENOMEM;
	}

	node->fcd_op = dentry_update->op;
	node->fcd_parent = dir->i_ino;
	node->fcd_ino = inode->i_ino;
	if (dentry->d_name.len > DNAME_INLINE_LEN) {
		node->fcd_name.name = kmalloc(dentry->d_name.len, GFP_NOFS);
		if (!node->fcd_name.name) {
			kmem_cache_free(ext4_fc_dentry_cachep, node);
			ext4_fc_mark_ineligible(sb, EXT4_FC_REASON_NOMEM, NULL);
			mutex_lock(&ei->i_fc_lock);
			return -ENOMEM;
		}
		memcpy((u8 *)node->fcd_name.name, dentry->d_name.name,
			dentry->d_name.len);
	} else {
		memcpy(node->fcd_iname, dentry->d_name.name,
			dentry->d_name.len);
		node->fcd_name.name = node->fcd_iname;
	}
	node->fcd_name.len = dentry->d_name.len;
	INIT_LIST_HEAD(&node->fcd_dilist);
	spin_lock(&sbi->s_fc_lock);
	if (sbi->s_journal->j_flags & JBD2_FULL_COMMIT_ONGOING ||
		sbi->s_journal->j_flags & JBD2_FAST_COMMIT_ONGOING)
		list_add_tail(&node->fcd_list,
				&sbi->s_fc_dentry_q[FC_Q_STAGING]);
	else
		list_add_tail(&node->fcd_list, &sbi->s_fc_dentry_q[FC_Q_MAIN]);

	/*
	 * This helps us keep a track of all fc_dentry updates which is part of
	 * this ext4 inode. So in case the inode is getting unlinked, before
	 * even we get a chance to fsync, we could remove all fc_dentry
	 * references while evicting the inode in ext4_fc_del().
	 * Also with this, we don't need to loop over all the inodes in
	 * sbi->s_fc_q to get the corresponding inode in
	 * ext4_fc_commit_dentry_updates().
	 */
	if (dentry_update->op == EXT4_FC_TAG_CREAT) {
		WARN_ON(!list_empty(&ei->i_fc_dilist));
		list_add_tail(&node->fcd_dilist, &ei->i_fc_dilist);
	}
	spin_unlock(&sbi->s_fc_lock);
	mutex_lock(&ei->i_fc_lock);

	return 0;
}

void __ext4_fc_track_unlink(handle_t *handle,
		struct inode *inode, struct dentry *dentry)
{
	struct __track_dentry_update_args args;
	int ret;

	args.dentry = dentry;
	args.op = EXT4_FC_TAG_UNLINK;

	ret = ext4_fc_track_template(handle, inode, __track_dentry_update,
					(void *)&args, 0);
	trace_ext4_fc_track_unlink(handle, inode, dentry, ret);
}

void ext4_fc_track_unlink(handle_t *handle, struct dentry *dentry)
{
	struct inode *inode = d_inode(dentry);

	if (ext4_fc_disabled(inode->i_sb))
		return;

	if (ext4_test_mount_flag(inode->i_sb, EXT4_MF_FC_INELIGIBLE))
		return;

	__ext4_fc_track_unlink(handle, inode, dentry);
}

void __ext4_fc_track_link(handle_t *handle,
	struct inode *inode, struct dentry *dentry)
{
	struct __track_dentry_update_args args;
	int ret;

	args.dentry = dentry;
	args.op = EXT4_FC_TAG_LINK;

	ret = ext4_fc_track_template(handle, inode, __track_dentry_update,
					(void *)&args, 0);
	trace_ext4_fc_track_link(handle, inode, dentry, ret);
}

void ext4_fc_track_link(handle_t *handle, struct dentry *dentry)
{
	struct inode *inode = d_inode(dentry);

	if (ext4_fc_disabled(inode->i_sb))
		return;

	if (ext4_test_mount_flag(inode->i_sb, EXT4_MF_FC_INELIGIBLE))
		return;

	__ext4_fc_track_link(handle, inode, dentry);
}

void __ext4_fc_track_create(handle_t *handle, struct inode *inode,
			  struct dentry *dentry)
{
	struct __track_dentry_update_args args;
	int ret;

	args.dentry = dentry;
	args.op = EXT4_FC_TAG_CREAT;

	ret = ext4_fc_track_template(handle, inode, __track_dentry_update,
					(void *)&args, 0);
	trace_ext4_fc_track_create(handle, inode, dentry, ret);
}

void ext4_fc_track_create(handle_t *handle, struct dentry *dentry)
{
	struct inode *inode = d_inode(dentry);

	if (ext4_fc_disabled(inode->i_sb))
		return;

	if (ext4_test_mount_flag(inode->i_sb, EXT4_MF_FC_INELIGIBLE))
		return;

	__ext4_fc_track_create(handle, inode, dentry);
}

/* __track_fn for inode tracking */
static int __track_inode(struct inode *inode, void *arg, bool update)
{
	if (update)
		return -EEXIST;

	EXT4_I(inode)->i_fc_lblk_len = 0;

	return 0;
}

void ext4_fc_track_inode(handle_t *handle, struct inode *inode)
{
	int ret;

	if (S_ISDIR(inode->i_mode))
		return;

	if (ext4_fc_disabled(inode->i_sb))
		return;

	if (ext4_should_journal_data(inode)) {
		ext4_fc_mark_ineligible(inode->i_sb,
					EXT4_FC_REASON_INODE_JOURNAL_DATA, handle);
		return;
	}

	if (ext4_test_mount_flag(inode->i_sb, EXT4_MF_FC_INELIGIBLE))
		return;

	ret = ext4_fc_track_template(handle, inode, __track_inode, NULL, 1);
	trace_ext4_fc_track_inode(handle, inode, ret);
}

struct __track_range_args {
	ext4_lblk_t start, end;
};

/* __track_fn for tracking data updates */
static int __track_range(struct inode *inode, void *arg, bool update)
{
	struct ext4_inode_info *ei = EXT4_I(inode);
	ext4_lblk_t oldstart;
	struct __track_range_args *__arg =
		(struct __track_range_args *)arg;

	if (inode->i_ino < EXT4_FIRST_INO(inode->i_sb)) {
		ext4_debug("Special inode %ld being modified\n", inode->i_ino);
		return -ECANCELED;
	}

	oldstart = ei->i_fc_lblk_start;

	if (update && ei->i_fc_lblk_len > 0) {
		ei->i_fc_lblk_start = min(ei->i_fc_lblk_start, __arg->start);
		ei->i_fc_lblk_len =
			max(oldstart + ei->i_fc_lblk_len - 1, __arg->end) -
				ei->i_fc_lblk_start + 1;
	} else {
		ei->i_fc_lblk_start = __arg->start;
		ei->i_fc_lblk_len = __arg->end - __arg->start + 1;
	}

	return 0;
}

void ext4_fc_track_range(handle_t *handle, struct inode *inode, ext4_lblk_t start,
			 ext4_lblk_t end)
{
	struct __track_range_args args;
	int ret;

	if (S_ISDIR(inode->i_mode))
		return;

	if (ext4_fc_disabled(inode->i_sb))
		return;

	if (ext4_test_mount_flag(inode->i_sb, EXT4_MF_FC_INELIGIBLE))
		return;

	args.start = start;
	args.end = end;

	ret = ext4_fc_track_template(handle, inode,  __track_range, &args, 1);

	trace_ext4_fc_track_range(handle, inode, start, end, ret);
}

static void ext4_fc_submit_bh(struct super_block *sb, bool is_tail)
{
	blk_opf_t write_flags = REQ_SYNC;
	struct buffer_head *bh = EXT4_SB(sb)->s_fc_bh;

	/* Add REQ_FUA | REQ_PREFLUSH only its tail */
	if (test_opt(sb, BARRIER) && is_tail)
		write_flags |= REQ_FUA | REQ_PREFLUSH;
	lock_buffer(bh);
	set_buffer_dirty(bh);
	set_buffer_uptodate(bh);
	bh->b_end_io = ext4_end_buffer_io_sync;
	submit_bh(REQ_OP_WRITE | write_flags, bh);
	EXT4_SB(sb)->s_fc_bh = NULL;
}

/* Ext4 commit path routines */

/*
 * Allocate len bytes on a fast commit buffer.
 *
 * During the commit time this function is used to manage fast commit
 * block space. We don't split a fast commit log onto different
 * blocks. So this function makes sure that if there's not enough space
 * on the current block, the remaining space in the current block is
 * marked as unused by adding EXT4_FC_TAG_PAD tag. In that case,
 * new block is from jbd2 and CRC is updated to reflect the padding
 * we added.
 */
static u8 *ext4_fc_reserve_space(struct super_block *sb, int len, u32 *crc)
{
	struct ext4_fc_tl tl;
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	struct buffer_head *bh;
	int bsize = sbi->s_journal->j_blocksize;
	int ret, off = sbi->s_fc_bytes % bsize;
	int remaining;
	u8 *dst;

	/*
	 * If 'len' is too long to fit in any block alongside a PAD tlv, then we
	 * cannot fulfill the request.
	 */
	if (len > bsize - EXT4_FC_TAG_BASE_LEN)
		return NULL;

	if (!sbi->s_fc_bh) {
		ret = jbd2_fc_get_buf(EXT4_SB(sb)->s_journal, &bh);
		if (ret)
			return NULL;
		sbi->s_fc_bh = bh;
	}
	dst = sbi->s_fc_bh->b_data + off;

	/*
	 * Allocate the bytes in the current block if we can do so while still
	 * leaving enough space for a PAD tlv.
	 */
	remaining = bsize - EXT4_FC_TAG_BASE_LEN - off;
	if (len <= remaining) {
		sbi->s_fc_bytes += len;
		return dst;
	}

	/*
	 * Else, terminate the current block with a PAD tlv, then allocate a new
	 * block and allocate the bytes at the start of that new block.
	 */

	tl.fc_tag = cpu_to_le16(EXT4_FC_TAG_PAD);
	tl.fc_len = cpu_to_le16(remaining);
	memcpy(dst, &tl, EXT4_FC_TAG_BASE_LEN);
	memset(dst + EXT4_FC_TAG_BASE_LEN, 0, remaining);
	*crc = ext4_chksum(sbi, *crc, sbi->s_fc_bh->b_data, bsize);

	ext4_fc_submit_bh(sb, false);

	ret = jbd2_fc_get_buf(EXT4_SB(sb)->s_journal, &bh);
	if (ret)
		return NULL;
	sbi->s_fc_bh = bh;
	sbi->s_fc_bytes += bsize - off + len;
	return sbi->s_fc_bh->b_data;
}

/*
 * Complete a fast commit by writing tail tag.
 *
 * Writing tail tag marks the end of a fast commit. In order to guarantee
 * atomicity, after writing tail tag, even if there's space remaining
 * in the block, next commit shouldn't use it. That's why tail tag
 * has the length as that of the remaining space on the block.
 */
static int ext4_fc_write_tail(struct super_block *sb, u32 crc)
{
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	struct ext4_fc_tl tl;
	struct ext4_fc_tail tail;
	int off, bsize = sbi->s_journal->j_blocksize;
	u8 *dst;

	/*
	 * ext4_fc_reserve_space takes care of allocating an extra block if
	 * there's no enough space on this block for accommodating this tail.
	 */
	dst = ext4_fc_reserve_space(sb, EXT4_FC_TAG_BASE_LEN + sizeof(tail), &crc);
	if (!dst)
		return -ENOSPC;

	off = sbi->s_fc_bytes % bsize;

	tl.fc_tag = cpu_to_le16(EXT4_FC_TAG_TAIL);
	tl.fc_len = cpu_to_le16(bsize - off + sizeof(struct ext4_fc_tail));
	sbi->s_fc_bytes = round_up(sbi->s_fc_bytes, bsize);

	memcpy(dst, &tl, EXT4_FC_TAG_BASE_LEN);
	dst += EXT4_FC_TAG_BASE_LEN;
	tail.fc_tid = cpu_to_le32(sbi->s_journal->j_running_transaction->t_tid);
	memcpy(dst, &tail.fc_tid, sizeof(tail.fc_tid));
	dst += sizeof(tail.fc_tid);
	crc = ext4_chksum(sbi, crc, sbi->s_fc_bh->b_data,
			  dst - (u8 *)sbi->s_fc_bh->b_data);
	tail.fc_crc = cpu_to_le32(crc);
	memcpy(dst, &tail.fc_crc, sizeof(tail.fc_crc));
	dst += sizeof(tail.fc_crc);
	memset(dst, 0, bsize - off); /* Don't leak uninitialized memory. */

	ext4_fc_submit_bh(sb, true);

	return 0;
}

/*
 * Adds tag, length, value and updates CRC. Returns true if tlv was added.
 * Returns false if there's not enough space.
 */
static bool ext4_fc_add_tlv(struct super_block *sb, u16 tag, u16 len, u8 *val,
			   u32 *crc)
{
	struct ext4_fc_tl tl;
	u8 *dst;

	dst = ext4_fc_reserve_space(sb, EXT4_FC_TAG_BASE_LEN + len, crc);
	if (!dst)
		return false;

	tl.fc_tag = cpu_to_le16(tag);
	tl.fc_len = cpu_to_le16(len);

	memcpy(dst, &tl, EXT4_FC_TAG_BASE_LEN);
	memcpy(dst + EXT4_FC_TAG_BASE_LEN, val, len);

	return true;
}

/* Same as above, but adds dentry tlv. */
static bool ext4_fc_add_dentry_tlv(struct super_block *sb, u32 *crc,
				   struct ext4_fc_dentry_update *fc_dentry)
{
	struct ext4_fc_dentry_info fcd;
	struct ext4_fc_tl tl;
	int dlen = fc_dentry->fcd_name.len;
	u8 *dst = ext4_fc_reserve_space(sb,
			EXT4_FC_TAG_BASE_LEN + sizeof(fcd) + dlen, crc);

	if (!dst)
		return false;

	fcd.fc_parent_ino = cpu_to_le32(fc_dentry->fcd_parent);
	fcd.fc_ino = cpu_to_le32(fc_dentry->fcd_ino);
	tl.fc_tag = cpu_to_le16(fc_dentry->fcd_op);
	tl.fc_len = cpu_to_le16(sizeof(fcd) + dlen);
	memcpy(dst, &tl, EXT4_FC_TAG_BASE_LEN);
	dst += EXT4_FC_TAG_BASE_LEN;
	memcpy(dst, &fcd, sizeof(fcd));
	dst += sizeof(fcd);
	memcpy(dst, fc_dentry->fcd_name.name, dlen);

	return true;
}

/*
 * Writes inode in the fast commit space under TLV with tag @tag.
 * Returns 0 on success, error on failure.
 */
static int ext4_fc_write_inode(struct inode *inode, u32 *crc)
{
	struct ext4_inode_info *ei = EXT4_I(inode);
	int inode_len = EXT4_GOOD_OLD_INODE_SIZE;
	int ret;
	struct ext4_iloc iloc;
	struct ext4_fc_inode fc_inode;
	struct ext4_fc_tl tl;
	u8 *dst;

	ret = ext4_get_inode_loc(inode, &iloc);
	if (ret)
		return ret;

	if (ext4_test_inode_flag(inode, EXT4_INODE_INLINE_DATA))
		inode_len = EXT4_INODE_SIZE(inode->i_sb);
	else if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE)
		inode_len += ei->i_extra_isize;

	fc_inode.fc_ino = cpu_to_le32(inode->i_ino);
	tl.fc_tag = cpu_to_le16(EXT4_FC_TAG_INODE);
	tl.fc_len = cpu_to_le16(inode_len + sizeof(fc_inode.fc_ino));

	ret = -ECANCELED;
	dst = ext4_fc_reserve_space(inode->i_sb,
		EXT4_FC_TAG_BASE_LEN + inode_len + sizeof(fc_inode.fc_ino), crc);
	if (!dst)
		goto err;

	memcpy(dst, &tl, EXT4_FC_TAG_BASE_LEN);
	dst += EXT4_FC_TAG_BASE_LEN;
	memcpy(dst, &fc_inode, sizeof(fc_inode));
	dst += sizeof(fc_inode);
	memcpy(dst, (u8 *)ext4_raw_inode(&iloc), inode_len);
	ret = 0;
err:
	brelse(iloc.bh);
	return ret;
}

/*
 * Writes updated data ranges for the inode in question. Updates CRC.
 * Returns 0 on success, error otherwise.
 */
static int ext4_fc_write_inode_data(struct inode *inode, u32 *crc)
{
	ext4_lblk_t old_blk_size, cur_lblk_off, new_blk_size;
	struct ext4_inode_info *ei = EXT4_I(inode);
	struct ext4_map_blocks map;
	struct ext4_fc_add_range fc_ext;
	struct ext4_fc_del_range lrange;
	struct ext4_extent *ex;
	int ret;

	mutex_lock(&ei->i_fc_lock);
	if (ei->i_fc_lblk_len == 0) {
		mutex_unlock(&ei->i_fc_lock);
		return 0;
	}
	old_blk_size = ei->i_fc_lblk_start;
	new_blk_size = ei->i_fc_lblk_start + ei->i_fc_lblk_len - 1;
	ei->i_fc_lblk_len = 0;
	mutex_unlock(&ei->i_fc_lock);

	cur_lblk_off = old_blk_size;
	ext4_debug("will try writing %d to %d for inode %ld\n",
		   cur_lblk_off, new_blk_size, inode->i_ino);

	while (cur_lblk_off <= new_blk_size) {
		map.m_lblk = cur_lblk_off;
		map.m_len = new_blk_size - cur_lblk_off + 1;
		ret = ext4_map_blocks(NULL, inode, &map, 0);
		if (ret < 0)
			return -ECANCELED;

		if (map.m_len == 0) {
			cur_lblk_off++;
			continue;
		}

		if (ret == 0) {
			lrange.fc_ino = cpu_to_le32(inode->i_ino);
			lrange.fc_lblk = cpu_to_le32(map.m_lblk);
			lrange.fc_len = cpu_to_le32(map.m_len);
			if (!ext4_fc_add_tlv(inode->i_sb, EXT4_FC_TAG_DEL_RANGE,
					    sizeof(lrange), (u8 *)&lrange, crc))
				return -ENOSPC;
		} else {
			unsigned int max = (map.m_flags & EXT4_MAP_UNWRITTEN) ?
				EXT_UNWRITTEN_MAX_LEN : EXT_INIT_MAX_LEN;

			/* Limit the number of blocks in one extent */
			map.m_len = min(max, map.m_len);

			fc_ext.fc_ino = cpu_to_le32(inode->i_ino);
			ex = (struct ext4_extent *)&fc_ext.fc_ex;
			ex->ee_block = cpu_to_le32(map.m_lblk);
			ex->ee_len = cpu_to_le16(map.m_len);
			ext4_ext_store_pblock(ex, map.m_pblk);
			if (map.m_flags & EXT4_MAP_UNWRITTEN)
				ext4_ext_mark_unwritten(ex);
			else
				ext4_ext_mark_initialized(ex);
			if (!ext4_fc_add_tlv(inode->i_sb, EXT4_FC_TAG_ADD_RANGE,
					    sizeof(fc_ext), (u8 *)&fc_ext, crc))
				return -ENOSPC;
		}

		cur_lblk_off += map.m_len;
	}

	return 0;
}


/* Submit data for all the fast commit inodes */
static int ext4_fc_submit_inode_data_all(journal_t *journal)
{
	struct super_block *sb = journal->j_private;
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	struct ext4_inode_info *ei;
	int ret = 0;

	spin_lock(&sbi->s_fc_lock);
	list_for_each_entry(ei, &sbi->s_fc_q[FC_Q_MAIN], i_fc_list) {
		ext4_set_inode_state(&ei->vfs_inode, EXT4_STATE_FC_COMMITTING);
		while (atomic_read(&ei->i_fc_updates)) {
			DEFINE_WAIT(wait);

			prepare_to_wait(&ei->i_fc_wait, &wait,
						TASK_UNINTERRUPTIBLE);
			if (atomic_read(&ei->i_fc_updates)) {
				spin_unlock(&sbi->s_fc_lock);
				schedule();
				spin_lock(&sbi->s_fc_lock);
			}
			finish_wait(&ei->i_fc_wait, &wait);
		}
		spin_unlock(&sbi->s_fc_lock);
		ret = jbd2_submit_inode_data(journal, ei->jinode);
		if (ret)
			return ret;
		spin_lock(&sbi->s_fc_lock);
	}
	spin_unlock(&sbi->s_fc_lock);

	return ret;
}

/* Wait for completion of data for all the fast commit inodes */
static int ext4_fc_wait_inode_data_all(journal_t *journal)
{
	struct super_block *sb = journal->j_private;
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	struct ext4_inode_info *pos, *n;
	int ret = 0;

	spin_lock(&sbi->s_fc_lock);
	list_for_each_entry_safe(pos, n, &sbi->s_fc_q[FC_Q_MAIN], i_fc_list) {
		if (!ext4_test_inode_state(&pos->vfs_inode,
					   EXT4_STATE_FC_COMMITTING))
			continue;
		spin_unlock(&sbi->s_fc_lock);

		ret = jbd2_wait_inode_data(journal, pos->jinode);
		if (ret)
			return ret;
		spin_lock(&sbi->s_fc_lock);
	}
	spin_unlock(&sbi->s_fc_lock);

	return 0;
}

/* Commit all the directory entry updates */
static int ext4_fc_commit_dentry_updates(journal_t *journal, u32 *crc)
__acquires(&sbi->s_fc_lock)
__releases(&sbi->s_fc_lock)
{
	struct super_block *sb = journal->j_private;
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	struct ext4_fc_dentry_update *fc_dentry, *fc_dentry_n;
	struct inode *inode;
	struct ext4_inode_info *ei;
	int ret;

	if (list_empty(&sbi->s_fc_dentry_q[FC_Q_MAIN]))
		return 0;
	list_for_each_entry_safe(fc_dentry, fc_dentry_n,
				 &sbi->s_fc_dentry_q[FC_Q_MAIN], fcd_list) {
		if (fc_dentry->fcd_op != EXT4_FC_TAG_CREAT) {
			spin_unlock(&sbi->s_fc_lock);
			if (!ext4_fc_add_dentry_tlv(sb, crc, fc_dentry)) {
				ret = -ENOSPC;
				goto lock_and_exit;
			}
			spin_lock(&sbi->s_fc_lock);
			continue;
		}
		/*
		 * With fcd_dilist we need not loop in sbi->s_fc_q to get the
		 * corresponding inode pointer
		 */
		WARN_ON(list_empty(&fc_dentry->fcd_dilist));
		ei = list_first_entry(&fc_dentry->fcd_dilist,
				struct ext4_inode_info, i_fc_dilist);
		inode = &ei->vfs_inode;
		WARN_ON(inode->i_ino != fc_dentry->fcd_ino);

		spin_unlock(&sbi->s_fc_lock);

		/*
		 * We first write the inode and then the create dirent. This
		 * allows the recovery code to create an unnamed inode first
		 * and then link it to a directory entry. This allows us
		 * to use namei.c routines almost as is and simplifies
		 * the recovery code.
		 */
		ret = ext4_fc_write_inode(inode, crc);
		if (ret)
			goto lock_and_exit;

		ret = ext4_fc_write_inode_data(inode, crc);
		if (ret)
			goto lock_and_exit;

		if (!ext4_fc_add_dentry_tlv(sb, crc, fc_dentry)) {
			ret = -ENOSPC;
			goto lock_and_exit;
		}

		spin_lock(&sbi->s_fc_lock);
	}
	return 0;
lock_and_exit:
	spin_lock(&sbi->s_fc_lock);
	return ret;
}

static int ext4_fc_perform_commit(journal_t *journal)
{
	struct super_block *sb = journal->j_private;
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	struct ext4_inode_info *iter;
	struct ext4_fc_head head;
	struct inode *inode;
	struct blk_plug plug;
	int ret = 0;
	u32 crc = 0;

	ret = ext4_fc_submit_inode_data_all(journal);
	if (ret)
		return ret;

	ret = ext4_fc_wait_inode_data_all(journal);
	if (ret)
		return ret;

	/*
	 * If file system device is different from journal device, issue a cache
	 * flush before we start writing fast commit blocks.
	 */
	if (journal->j_fs_dev != journal->j_dev)
		blkdev_issue_flush(journal->j_fs_dev);

	blk_start_plug(&plug);
	if (sbi->s_fc_bytes == 0) {
		/*
		 * Add a head tag only if this is the first fast commit
		 * in this TID.
		 */
		head.fc_features = cpu_to_le32(EXT4_FC_SUPPORTED_FEATURES);
		head.fc_tid = cpu_to_le32(
			sbi->s_journal->j_running_transaction->t_tid);
		if (!ext4_fc_add_tlv(sb, EXT4_FC_TAG_HEAD, sizeof(head),
			(u8 *)&head, &crc)) {
			ret = -ENOSPC;
			goto out;
		}
	}

	spin_lock(&sbi->s_fc_lock);
	ret = ext4_fc_commit_dentry_updates(journal, &crc);
	if (ret) {
		spin_unlock(&sbi->s_fc_lock);
		goto out;
	}

	list_for_each_entry(iter, &sbi->s_fc_q[FC_Q_MAIN], i_fc_list) {
		inode = &iter->vfs_inode;
		if (!ext4_test_inode_state(inode, EXT4_STATE_FC_COMMITTING))
			continue;

		spin_unlock(&sbi->s_fc_lock);
		ret = ext4_fc_write_inode_data(inode, &crc);
		if (ret)
			goto out;
		ret = ext4_fc_write_inode(inode, &crc);
		if (ret)
			goto out;
		spin_lock(&sbi->s_fc_lock);
	}
	spin_unlock(&sbi->s_fc_lock);

	ret = ext4_fc_write_tail(sb, crc);

out:
	blk_finish_plug(&plug);
	return ret;
}

static void ext4_fc_update_stats(struct super_block *sb, int status,
				 u64 commit_time, int nblks, tid_t commit_tid)
{
	struct ext4_fc_stats *stats = &EXT4_SB(sb)->s_fc_stats;

	ext4_debug("Fast commit ended with status = %d for tid %u",
			status, commit_tid);
	if (status == EXT4_FC_STATUS_OK) {
		stats->fc_num_commits++;
		stats->fc_numblks += nblks;
		if (likely(stats->s_fc_avg_commit_time))
			stats->s_fc_avg_commit_time =
				(commit_time +
				 stats->s_fc_avg_commit_time * 3) / 4;
		else
			stats->s_fc_avg_commit_time = commit_time;
	} else if (status == EXT4_FC_STATUS_FAILED ||
		   status == EXT4_FC_STATUS_INELIGIBLE) {
		if (status == EXT4_FC_STATUS_FAILED)
			stats->fc_failed_commits++;
		stats->fc_ineligible_commits++;
	} else {
		stats->fc_skipped_commits++;
	}
	trace_ext4_fc_commit_stop(sb, nblks, status, commit_tid);
}

/*
 * The main commit entry point. Performs a fast commit for transaction
 * commit_tid if needed. If it's not possible to perform a fast commit
 * due to various reasons, we fall back to full commit. Returns 0
 * on success, error otherwise.
 */
int ext4_fc_commit(journal_t *journal, tid_t commit_tid)
{
	struct super_block *sb = journal->j_private;
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	int nblks = 0, ret, bsize = journal->j_blocksize;
	int subtid = atomic_read(&sbi->s_fc_subtid);
	int status = EXT4_FC_STATUS_OK, fc_bufs_before = 0;
	ktime_t start_time, commit_time;

	if (!test_opt2(sb, JOURNAL_FAST_COMMIT))
		return jbd2_complete_transaction(journal, commit_tid);

	trace_ext4_fc_commit_start(sb, commit_tid);

	start_time = ktime_get();

restart_fc:
	ret = jbd2_fc_begin_commit(journal, commit_tid);
	if (ret == -EALREADY) {
		/* There was an ongoing commit, check if we need to restart */
		if (atomic_read(&sbi->s_fc_subtid) <= subtid &&
			commit_tid > journal->j_commit_sequence)
			goto restart_fc;
		ext4_fc_update_stats(sb, EXT4_FC_STATUS_SKIPPED, 0, 0,
				commit_tid);
		return 0;
	} else if (ret) {
		/*
		 * Commit couldn't start. Just update stats and perform a
		 * full commit.
		 */
		ext4_fc_update_stats(sb, EXT4_FC_STATUS_FAILED, 0, 0,
				commit_tid);
		return jbd2_complete_transaction(journal, commit_tid);
	}

	/*
	 * After establishing journal barrier via jbd2_fc_begin_commit(), check
	 * if we are fast commit ineligible.
	 */
	if (ext4_test_mount_flag(sb, EXT4_MF_FC_INELIGIBLE)) {
		status = EXT4_FC_STATUS_INELIGIBLE;
		goto fallback;
	}

	fc_bufs_before = (sbi->s_fc_bytes + bsize - 1) / bsize;
	ret = ext4_fc_perform_commit(journal);
	if (ret < 0) {
		status = EXT4_FC_STATUS_FAILED;
		goto fallback;
	}
	nblks = (sbi->s_fc_bytes + bsize - 1) / bsize - fc_bufs_before;
	ret = jbd2_fc_wait_bufs(journal, nblks);
	if (ret < 0) {
		status = EXT4_FC_STATUS_FAILED;
		goto fallback;
	}
	atomic_inc(&sbi->s_fc_subtid);
	ret = jbd2_fc_end_commit(journal);
	/*
	 * weight the commit time higher than the average time so we
	 * don't react too strongly to vast changes in the commit time
	 */
	commit_time = ktime_to_ns(ktime_sub(ktime_get(), start_time));
	ext4_fc_update_stats(sb, status, commit_time, nblks, commit_tid);
	return ret;

fallback:
	ret = jbd2_fc_end_commit_fallback(journal);
	ext4_fc_update_stats(sb, status, 0, 0, commit_tid);
	return ret;
}

/*
 * Fast commit cleanup routine. This is called after every fast commit and
 * full commit. full is true if we are called after a full commit.
 */
static void ext4_fc_cleanup(journal_t *journal, int full, tid_t tid)
{
	struct super_block *sb = journal->j_private;
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	struct ext4_inode_info *iter, *iter_n;
	struct ext4_fc_dentry_update *fc_dentry;

	if (full && sbi->s_fc_bh)
		sbi->s_fc_bh = NULL;

	trace_ext4_fc_cleanup(journal, full, tid);
	jbd2_fc_release_bufs(journal);

	spin_lock(&sbi->s_fc_lock);
	list_for_each_entry_safe(iter, iter_n, &sbi->s_fc_q[FC_Q_MAIN],
				 i_fc_list) {
		list_del_init(&iter->i_fc_list);
		ext4_clear_inode_state(&iter->vfs_inode,
				       EXT4_STATE_FC_COMMITTING);
		if (iter->i_sync_tid <= tid)
			ext4_fc_reset_inode(&iter->vfs_inode);
		/* Make sure EXT4_STATE_FC_COMMITTING bit is clear */
		smp_mb();
#if (BITS_PER_LONG < 64)
		wake_up_bit(&iter->i_state_flags, EXT4_STATE_FC_COMMITTING);
#else
		wake_up_bit(&iter->i_flags, EXT4_STATE_FC_COMMITTING);
#endif
	}

	while (!list_empty(&sbi->s_fc_dentry_q[FC_Q_MAIN])) {
		fc_dentry = list_first_entry(&sbi->s_fc_dentry_q[FC_Q_MAIN],
					     struct ext4_fc_dentry_update,
					     fcd_list);
		list_del_init(&fc_dentry->fcd_list);
		list_del_init(&fc_dentry->fcd_dilist);
		spin_unlock(&sbi->s_fc_lock);

		if (fc_dentry->fcd_name.name &&
			fc_dentry->fcd_name.len > DNAME_INLINE_LEN)
			kfree(fc_dentry->fcd_name.name);
		kmem_cache_free(ext4_fc_dentry_cachep, fc_dentry);
		spin_lock(&sbi->s_fc_lock);
	}

	list_splice_init(&sbi->s_fc_dentry_q[FC_Q_STAGING],
				&sbi->s_fc_dentry_q[FC_Q_MAIN]);
	list_splice_init(&sbi->s_fc_q[FC_Q_STAGING],
				&sbi->s_fc_q[FC_Q_MAIN]);

	if (tid >= sbi->s_fc_ineligible_tid) {
		sbi->s_fc_ineligible_tid = 0;
		ext4_clear_mount_flag(sb, EXT4_MF_FC_INELIGIBLE);
	}

	if (full)
		sbi->s_fc_bytes = 0;
	spin_unlock(&sbi->s_fc_lock);
	trace_ext4_fc_stats(sb);
}

/* Ext4 Replay Path Routines */

/* Helper struct for dentry replay routines */
struct dentry_info_args {
	int parent_ino, dname_len, ino, inode_len;
	char *dname;
};

static inline void tl_to_darg(struct dentry_info_args *darg,
			      struct ext4_fc_tl *tl, u8 *val)
{
	struct ext4_fc_dentry_info fcd;

	memcpy(&fcd, val, sizeof(fcd));

	darg->parent_ino = le32_to_cpu(fcd.fc_parent_ino);
	darg->ino = le32_to_cpu(fcd.fc_ino);
	darg->dname = val + offsetof(struct ext4_fc_dentry_info, fc_dname);
	darg->dname_len = tl->fc_len - sizeof(struct ext4_fc_dentry_info);
}

static inline void ext4_fc_get_tl(struct ext4_fc_tl *tl, u8 *val)
{
	memcpy(tl, val, EXT4_FC_TAG_BASE_LEN);
	tl->fc_len = le16_to_cpu(tl->fc_len);
	tl->fc_tag = le16_to_cpu(tl->fc_tag);
}

/* Unlink replay function */
static int ext4_fc_replay_unlink(struct super_block *sb, struct ext4_fc_tl *tl,
				 u8 *val)
{
	struct inode *inode, *old_parent;
	struct qstr entry;
	struct dentry_info_args darg;
	int ret = 0;

	tl_to_darg(&darg, tl, val);

	trace_ext4_fc_replay(sb, EXT4_FC_TAG_UNLINK, darg.ino,
			darg.parent_ino, darg.dname_len);

	entry.name = darg.dname;
	entry.len = darg.dname_len;
	inode = ext4_iget(sb, darg.ino, EXT4_IGET_NORMAL);

	if (IS_ERR(inode)) {
		ext4_debug("Inode %d not found", darg.ino);
		return 0;
	}

	old_parent = ext4_iget(sb, darg.parent_ino,
				EXT4_IGET_NORMAL);
	if (IS_ERR(old_parent)) {
		ext4_debug("Dir with inode %d not found", darg.parent_ino);
		iput(inode);
		return 0;
	}

	ret = __ext4_unlink(old_parent, &entry, inode, NULL);
	/* -ENOENT ok coz it might not exist anymore. */
	if (ret == -ENOENT)
		ret = 0;
	iput(old_parent);
	iput(inode);
	return ret;
}

static int ext4_fc_replay_link_internal(struct super_block *sb,
				struct dentry_info_args *darg,
				struct inode *inode)
{
	struct inode *dir = NULL;
	struct dentry *dentry_dir = NULL, *dentry_inode = NULL;
	struct qstr qstr_dname = QSTR_INIT(darg->dname, darg->dname_len);
	int ret = 0;

	dir = ext4_iget(sb, darg->parent_ino, EXT4_IGET_NORMAL);
	if (IS_ERR(dir)) {
		ext4_debug("Dir with inode %d not found.", darg->parent_ino);
		dir = NULL;
		goto out;
	}

	dentry_dir = d_obtain_alias(dir);
	if (IS_ERR(dentry_dir)) {
		ext4_debug("Failed to obtain dentry");
		dentry_dir = NULL;
		goto out;
	}

	dentry_inode = d_alloc(dentry_dir, &qstr_dname);
	if (!dentry_inode) {
		ext4_debug("Inode dentry not created.");
		ret = -ENOMEM;
		goto out;
	}

	ret = __ext4_link(dir, inode, dentry_inode);
	/*
	 * It's possible that link already existed since data blocks
	 * for the dir in question got persisted before we crashed OR
	 * we replayed this tag and crashed before the entire replay
	 * could complete.
	 */
	if (ret && ret != -EEXIST) {
		ext4_debug("Failed to link\n");
		goto out;
	}

	ret = 0;
out:
	if (dentry_dir) {
		d_drop(dentry_dir);
		dput(dentry_dir);
	} else if (dir) {
		iput(dir);
	}
	if (dentry_inode) {
		d_drop(dentry_inode);
		dput(dentry_inode);
	}

	return ret;
}

/* Link replay function */
static int ext4_fc_replay_link(struct super_block *sb, struct ext4_fc_tl *tl,
			       u8 *val)
{
	struct inode *inode;
	struct dentry_info_args darg;
	int ret = 0;

	tl_to_darg(&darg, tl, val);
	trace_ext4_fc_replay(sb, EXT4_FC_TAG_LINK, darg.ino,
			darg.parent_ino, darg.dname_len);

	inode = ext4_iget(sb, darg.ino, EXT4_IGET_NORMAL);
	if (IS_ERR(inode)) {
		ext4_debug("Inode not found.");
		return 0;
	}

	ret = ext4_fc_replay_link_internal(sb, &darg, inode);
	iput(inode);
	return ret;
}

/*
 * Record all the modified inodes during replay. We use this later to setup
 * block bitmaps correctly.
 */
static int ext4_fc_record_modified_inode(struct super_block *sb, int ino)
{
	struct ext4_fc_replay_state *state;
	int i;

	state = &EXT4_SB(sb)->s_fc_replay_state;
	for (i = 0; i < state->fc_modified_inodes_used; i++)
		if (state->fc_modified_inodes[i] == ino)
			return 0;
	if (state->fc_modified_inodes_used == state->fc_modified_inodes_size) {
		int *fc_modified_inodes;

		fc_modified_inodes = krealloc(state->fc_modified_inodes,
				sizeof(int) * (state->fc_modified_inodes_size +
				EXT4_FC_REPLAY_REALLOC_INCREMENT),
				GFP_KERNEL);
		if (!fc_modified_inodes)
			return -ENOMEM;
		state->fc_modified_inodes = fc_modified_inodes;
		state->fc_modified_inodes_size +=
			EXT4_FC_REPLAY_REALLOC_INCREMENT;
	}
	state->fc_modified_inodes[state->fc_modified_inodes_used++] = ino;
	return 0;
}

/*
 * Inode replay function
 */
static int ext4_fc_replay_inode(struct super_block *sb, struct ext4_fc_tl *tl,
				u8 *val)
{
	struct ext4_fc_inode fc_inode;
	struct ext4_inode *raw_inode;
	struct ext4_inode *raw_fc_inode;
	struct inode *inode = NULL;
	struct ext4_iloc iloc;
	int inode_len, ino, ret, tag = tl->fc_tag;
	struct ext4_extent_header *eh;
	size_t off_gen = offsetof(struct ext4_inode, i_generation);

	memcpy(&fc_inode, val, sizeof(fc_inode));

	ino = le32_to_cpu(fc_inode.fc_ino);
	trace_ext4_fc_replay(sb, tag, ino, 0, 0);

	inode = ext4_iget(sb, ino, EXT4_IGET_NORMAL);
	if (!IS_ERR(inode)) {
		ext4_ext_clear_bb(inode);
		iput(inode);
	}
	inode = NULL;

	ret = ext4_fc_record_modified_inode(sb, ino);
	if (ret)
		goto out;

	raw_fc_inode = (struct ext4_inode *)
		(val + offsetof(struct ext4_fc_inode, fc_raw_inode));
	ret = ext4_get_fc_inode_loc(sb, ino, &iloc);
	if (ret)
		goto out;

	inode_len = tl->fc_len - sizeof(struct ext4_fc_inode);
	raw_inode = ext4_raw_inode(&iloc);

	memcpy(raw_inode, raw_fc_inode, offsetof(struct ext4_inode, i_block));
	memcpy((u8 *)raw_inode + off_gen, (u8 *)raw_fc_inode + off_gen,
	       inode_len - off_gen);
	if (le32_to_cpu(raw_inode->i_flags) & EXT4_EXTENTS_FL) {
		eh = (struct ext4_extent_header *)(&raw_inode->i_block[0]);
		if (eh->eh_magic != EXT4_EXT_MAGIC) {
			memset(eh, 0, sizeof(*eh));
			eh->eh_magic = EXT4_EXT_MAGIC;
			eh->eh_max = cpu_to_le16(
				(sizeof(raw_inode->i_block) -
				 sizeof(struct ext4_extent_header))
				 / sizeof(struct ext4_extent));
		}
	} else if (le32_to_cpu(raw_inode->i_flags) & EXT4_INLINE_DATA_FL) {
		memcpy(raw_inode->i_block, raw_fc_inode->i_block,
			sizeof(raw_inode->i_block));
	}

	/* Immediately update the inode on disk. */
	ret = ext4_handle_dirty_metadata(NULL, NULL, iloc.bh);
	if (ret)
		goto out;
	ret = sync_dirty_buffer(iloc.bh);
	if (ret)
		goto out;
	ret = ext4_mark_inode_used(sb, ino);
	if (ret)
		goto out;

	/* Given that we just wrote the inode on disk, this SHOULD succeed. */
	inode = ext4_iget(sb, ino, EXT4_IGET_NORMAL);
	if (IS_ERR(inode)) {
		ext4_debug("Inode not found.");
		return -EFSCORRUPTED;
	}

	/*
	 * Our allocator could have made different decisions than before
	 * crashing. This should be fixed but until then, we calculate
	 * the number of blocks the inode.
	 */
	if (!ext4_test_inode_flag(inode, EXT4_INODE_INLINE_DATA))
		ext4_ext_replay_set_iblocks(inode);

	inode->i_generation = le32_to_cpu(ext4_raw_inode(&iloc)->i_generation);
	ext4_reset_inode_seed(inode);

	ext4_inode_csum_set(inode, ext4_raw_inode(&iloc), EXT4_I(inode));
	ret = ext4_handle_dirty_metadata(NULL, NULL, iloc.bh);
	sync_dirty_buffer(iloc.bh);
	brelse(iloc.bh);
out:
	iput(inode);
	if (!ret)
		blkdev_issue_flush(sb->s_bdev);

	return 0;
}

/*
 * Dentry create replay function.
 *
 * EXT4_FC_TAG_CREAT is preceded by EXT4_FC_TAG_INODE_FULL. Which means, the
 * inode for which we are trying to create a dentry here, should already have
 * been replayed before we start here.
 */
static int ext4_fc_replay_create(struct super_block *sb, struct ext4_fc_tl *tl,
				 u8 *val)
{
	int ret = 0;
	struct inode *inode = NULL;
	struct inode *dir = NULL;
	struct dentry_info_args darg;

	tl_to_darg(&darg, tl, val);

	trace_ext4_fc_replay(sb, EXT4_FC_TAG_CREAT, darg.ino,
			darg.parent_ino, darg.dname_len);

	/* This takes care of update group descriptor and other metadata */
	ret = ext4_mark_inode_used(sb, darg.ino);
	if (ret)
		goto out;

	inode = ext4_iget(sb, darg.ino, EXT4_IGET_NORMAL);
	if (IS_ERR(inode)) {
		ext4_debug("inode %d not found.", darg.ino);
		inode = NULL;
		ret = -EINVAL;
		goto out;
	}

	if (S_ISDIR(inode->i_mode)) {
		/*
		 * If we are creating a directory, we need to make sure that the
		 * dot and dot dot dirents are setup properly.
		 */
		dir = ext4_iget(sb, darg.parent_ino, EXT4_IGET_NORMAL);
		if (IS_ERR(dir)) {
			ext4_debug("Dir %d not found.", darg.ino);
			goto out;
		}
		ret = ext4_init_new_dir(NULL, dir, inode);
		iput(dir);
		if (ret) {
			ret = 0;
			goto out;
		}
	}
	ret = ext4_fc_replay_link_internal(sb, &darg, inode);
	if (ret)
		goto out;
	set_nlink(inode, 1);
	ext4_mark_inode_dirty(NULL, inode);
out:
	iput(inode);
	return ret;
}

/*
 * Record physical disk regions which are in use as per fast commit area,
 * and used by inodes during replay phase. Our simple replay phase
 * allocator excludes these regions from allocation.
 */
int ext4_fc_record_regions(struct super_block *sb, int ino,
		ext4_lblk_t lblk, ext4_fsblk_t pblk, int len, int replay)
{
	struct ext4_fc_replay_state *state;
	struct ext4_fc_alloc_region *region;

	state = &EXT4_SB(sb)->s_fc_replay_state;
	/*
	 * during replay phase, the fc_regions_valid may not same as
	 * fc_regions_used, update it when do new additions.
	 */
	if (replay && state->fc_regions_used != state->fc_regions_valid)
		state->fc_regions_used = state->fc_regions_valid;
	if (state->fc_regions_used == state->fc_regions_size) {
		struct ext4_fc_alloc_region *fc_regions;

		fc_regions = krealloc(state->fc_regions,
				      sizeof(struct ext4_fc_alloc_region) *
				      (state->fc_regions_size +
				       EXT4_FC_REPLAY_REALLOC_INCREMENT),
				      GFP_KERNEL);
		if (!fc_regions)
			return -ENOMEM;
		state->fc_regions_size +=
			EXT4_FC_REPLAY_REALLOC_INCREMENT;
		state->fc_regions = fc_regions;
	}
	region = &state->fc_regions[state->fc_regions_used++];
	region->ino = ino;
	region->lblk = lblk;
	region->pblk = pblk;
	region->len = len;

	if (replay)
		state->fc_regions_valid++;

	return 0;
}

/* Replay add range tag */
static int ext4_fc_replay_add_range(struct super_block *sb,
				    struct ext4_fc_tl *tl, u8 *val)
{
	struct ext4_fc_add_range fc_add_ex;
	struct ext4_extent newex, *ex;
	struct inode *inode;
	ext4_lblk_t start, cur;
	int remaining, len;
	ext4_fsblk_t start_pblk;
	struct ext4_map_blocks map;
	struct ext4_ext_path *path = NULL;
	int ret;

	memcpy(&fc_add_ex, val, sizeof(fc_add_ex));
	ex = (struct ext4_extent *)&fc_add_ex.fc_ex;

	trace_ext4_fc_replay(sb, EXT4_FC_TAG_ADD_RANGE,
		le32_to_cpu(fc_add_ex.fc_ino), le32_to_cpu(ex->ee_block),
		ext4_ext_get_actual_len(ex));

	inode = ext4_iget(sb, le32_to_cpu(fc_add_ex.fc_ino), EXT4_IGET_NORMAL);
	if (IS_ERR(inode)) {
		ext4_debug("Inode not found.");
		return 0;
	}

	ret = ext4_fc_record_modified_inode(sb, inode->i_ino);
	if (ret)
		goto out;

	start = le32_to_cpu(ex->ee_block);
	start_pblk = ext4_ext_pblock(ex);
	len = ext4_ext_get_actual_len(ex);

	cur = start;
	remaining = len;
	ext4_debug("ADD_RANGE, lblk %d, pblk %lld, len %d, unwritten %d, inode %ld\n",
		  start, start_pblk, len, ext4_ext_is_unwritten(ex),
		  inode->i_ino);

	while (remaining > 0) {
		map.m_lblk = cur;
		map.m_len = remaining;
		map.m_pblk = 0;
		ret = ext4_map_blocks(NULL, inode, &map, 0);

		if (ret < 0)
			goto out;

		if (ret == 0) {
			/* Range is not mapped */
			path = ext4_find_extent(inode, cur, NULL, 0);
			if (IS_ERR(path))
				goto out;
			memset(&newex, 0, sizeof(newex));
			newex.ee_block = cpu_to_le32(cur);
			ext4_ext_store_pblock(
				&newex, start_pblk + cur - start);
			newex.ee_len = cpu_to_le16(map.m_len);
			if (ext4_ext_is_unwritten(ex))
				ext4_ext_mark_unwritten(&newex);
			down_write(&EXT4_I(inode)->i_data_sem);
			ret = ext4_ext_insert_extent(
				NULL, inode, &path, &newex, 0);
			up_write((&EXT4_I(inode)->i_data_sem));
			ext4_free_ext_path(path);
			if (ret)
				goto out;
			goto next;
		}

		if (start_pblk + cur - start != map.m_pblk) {
			/*
			 * Logical to physical mapping changed. This can happen
			 * if this range was removed and then reallocated to
			 * map to new physical blocks during a fast commit.
			 */
			ret = ext4_ext_replay_update_ex(inode, cur, map.m_len,
					ext4_ext_is_unwritten(ex),
					start_pblk + cur - start);
			if (ret)
				goto out;
			/*
			 * Mark the old blocks as free since they aren't used
			 * anymore. We maintain an array of all the modified
			 * inodes. In case these blocks are still used at either
			 * a different logical range in the same inode or in
			 * some different inode, we will mark them as allocated
			 * at the end of the FC replay using our array of
			 * modified inodes.
			 */
			ext4_mb_mark_bb(inode->i_sb, map.m_pblk, map.m_len, 0);
			goto next;
		}

		/* Range is mapped and needs a state change */
		ext4_debug("Converting from %ld to %d %lld",
				map.m_flags & EXT4_MAP_UNWRITTEN,
			ext4_ext_is_unwritten(ex), map.m_pblk);
		ret = ext4_ext_replay_update_ex(inode, cur, map.m_len,
					ext4_ext_is_unwritten(ex), map.m_pblk);
		if (ret)
			goto out;
		/*
		 * We may have split the extent tree while toggling the state.
		 * Try to shrink the extent tree now.
		 */
		ext4_ext_replay_shrink_inode(inode, start + len);
next:
		cur += map.m_len;
		remaining -= map.m_len;
	}
	ext4_ext_replay_shrink_inode(inode, i_size_read(inode) >>
					sb->s_blocksize_bits);
out:
	iput(inode);
	return 0;
}

/* Replay DEL_RANGE tag */
static int
ext4_fc_replay_del_range(struct super_block *sb, struct ext4_fc_tl *tl,
			 u8 *val)
{
	struct inode *inode;
	struct ext4_fc_del_range lrange;
	struct ext4_map_blocks map;
	ext4_lblk_t cur, remaining;
	int ret;

	memcpy(&lrange, val, sizeof(lrange));
	cur = le32_to_cpu(lrange.fc_lblk);
	remaining = le32_to_cpu(lrange.fc_len);

	trace_ext4_fc_replay(sb, EXT4_FC_TAG_DEL_RANGE,
		le32_to_cpu(lrange.fc_ino), cur, remaining);

	inode = ext4_iget(sb, le32_to_cpu(lrange.fc_ino), EXT4_IGET_NORMAL);
	if (IS_ERR(inode)) {
		ext4_debug("Inode %d not found", le32_to_cpu(lrange.fc_ino));
		return 0;
	}

	ret = ext4_fc_record_modified_inode(sb, inode->i_ino);
	if (ret)
		goto out;

	ext4_debug("DEL_RANGE, inode %ld, lblk %d, len %d\n",
			inode->i_ino, le32_to_cpu(lrange.fc_lblk),
			le32_to_cpu(lrange.fc_len));
	while (remaining > 0) {
		map.m_lblk = cur;
		map.m_len = remaining;

		ret = ext4_map_blocks(NULL, inode, &map, 0);
		if (ret < 0)
			goto out;
		if (ret > 0) {
			remaining -= ret;
			cur += ret;
			ext4_mb_mark_bb(inode->i_sb, map.m_pblk, map.m_len, 0);
		} else {
			remaining -= map.m_len;
			cur += map.m_len;
		}
	}

	down_write(&EXT4_I(inode)->i_data_sem);
	ret = ext4_ext_remove_space(inode, le32_to_cpu(lrange.fc_lblk),
				le32_to_cpu(lrange.fc_lblk) +
				le32_to_cpu(lrange.fc_len) - 1);
	up_write(&EXT4_I(inode)->i_data_sem);
	if (ret)
		goto out;
	ext4_ext_replay_shrink_inode(inode,
		i_size_read(inode) >> sb->s_blocksize_bits);
	ext4_mark_inode_dirty(NULL, inode);
out:
	iput(inode);
	return 0;
}

static void ext4_fc_set_bitmaps_and_counters(struct super_block *sb)
{
	struct ext4_fc_replay_state *state;
	struct inode *inode;
	struct ext4_ext_path *path = NULL;
	struct ext4_map_blocks map;
	int i, ret, j;
	ext4_lblk_t cur, end;

	state = &EXT4_SB(sb)->s_fc_replay_state;
	for (i = 0; i < state->fc_modified_inodes_used; i++) {
		inode = ext4_iget(sb, state->fc_modified_inodes[i],
			EXT4_IGET_NORMAL);
		if (IS_ERR(inode)) {
			ext4_debug("Inode %d not found.",
				state->fc_modified_inodes[i]);
			continue;
		}
		cur = 0;
		end = EXT_MAX_BLOCKS;
		if (ext4_test_inode_flag(inode, EXT4_INODE_INLINE_DATA)) {
			iput(inode);
			continue;
		}
		while (cur < end) {
			map.m_lblk = cur;
			map.m_len = end - cur;

			ret = ext4_map_blocks(NULL, inode, &map, 0);
			if (ret < 0)
				break;

			if (ret > 0) {
				path = ext4_find_extent(inode, map.m_lblk, NULL, 0);
				if (!IS_ERR(path)) {
					for (j = 0; j < path->p_depth; j++)
						ext4_mb_mark_bb(inode->i_sb,
							path[j].p_block, 1, 1);
					ext4_free_ext_path(path);
				}
				cur += ret;
				ext4_mb_mark_bb(inode->i_sb, map.m_pblk,
							map.m_len, 1);
			} else {
				cur = cur + (map.m_len ? map.m_len : 1);
			}
		}
		iput(inode);
	}
}

/*
 * Check if block is in excluded regions for block allocation. The simple
 * allocator that runs during replay phase is calls this function to see
 * if it is okay to use a block.
 */
bool ext4_fc_replay_check_excluded(struct super_block *sb, ext4_fsblk_t blk)
{
	int i;
	struct ext4_fc_replay_state *state;

	state = &EXT4_SB(sb)->s_fc_replay_state;
	for (i = 0; i < state->fc_regions_valid; i++) {
		if (state->fc_regions[i].ino == 0 ||
			state->fc_regions[i].len == 0)
			continue;
		if (in_range(blk, state->fc_regions[i].pblk,
					state->fc_regions[i].len))
			return true;
	}
	return false;
}

/* Cleanup function called after replay */
void ext4_fc_replay_cleanup(struct super_block *sb)
{
	struct ext4_sb_info *sbi = EXT4_SB(sb);

	sbi->s_mount_state &= ~EXT4_FC_REPLAY;
	kfree(sbi->s_fc_replay_state.fc_regions);
	kfree(sbi->s_fc_replay_state.fc_modified_inodes);
}

static bool ext4_fc_value_len_isvalid(struct ext4_sb_info *sbi,
				      int tag, int len)
{
	switch (tag) {
	case EXT4_FC_TAG_ADD_RANGE:
		return len == sizeof(struct ext4_fc_add_range);
	case EXT4_FC_TAG_DEL_RANGE:
		return len == sizeof(struct ext4_fc_del_range);
	case EXT4_FC_TAG_CREAT:
	case EXT4_FC_TAG_LINK:
	case EXT4_FC_TAG_UNLINK:
		len -= sizeof(struct ext4_fc_dentry_info);
		return len >= 1 && len <= EXT4_NAME_LEN;
	case EXT4_FC_TAG_INODE:
		len -= sizeof(struct ext4_fc_inode);
		return len >= EXT4_GOOD_OLD_INODE_SIZE &&
			len <= sbi->s_inode_size;
	case EXT4_FC_TAG_PAD:
		return true; /* padding can have any length */
	case EXT4_FC_TAG_TAIL:
		return len >= sizeof(struct ext4_fc_tail);
	case EXT4_FC_TAG_HEAD:
		return len == sizeof(struct ext4_fc_head);
	}
	return false;
}

/*
 * Recovery Scan phase handler
 *
 * This function is called during the scan phase and is responsible
 * for doing following things:
 * - Make sure the fast commit area has valid tags for replay
 * - Count number of tags that need to be replayed by the replay handler
 * - Verify CRC
 * - Create a list of excluded blocks for allocation during replay phase
 *
 * This function returns JBD2_FC_REPLAY_CONTINUE to indicate that SCAN is
 * incomplete and JBD2 should send more blocks. It returns JBD2_FC_REPLAY_STOP
 * to indicate that scan has finished and JBD2 can now start replay phase.
 * It returns a negative error to indicate that there was an error. At the end
 * of a successful scan phase, sbi->s_fc_replay_state.fc_replay_num_tags is set
 * to indicate the number of tags that need to replayed during the replay phase.
 */
static int ext4_fc_replay_scan(journal_t *journal,
				struct buffer_head *bh, int off,
				tid_t expected_tid)
{
	struct super_block *sb = journal->j_private;
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	struct ext4_fc_replay_state *state;
	int ret = JBD2_FC_REPLAY_CONTINUE;
	struct ext4_fc_add_range ext;
	struct ext4_fc_tl tl;
	struct ext4_fc_tail tail;
	__u8 *start, *end, *cur, *val;
	struct ext4_fc_head head;
	struct ext4_extent *ex;

	state = &sbi->s_fc_replay_state;

	start = (u8 *)bh->b_data;
	end = start + journal->j_blocksize;

	if (state->fc_replay_expected_off == 0) {
		state->fc_cur_tag = 0;
		state->fc_replay_num_tags = 0;
		state->fc_crc = 0;
		state->fc_regions = NULL;
		state->fc_regions_valid = state->fc_regions_used =
			state->fc_regions_size = 0;
		/* Check if we can stop early */
		if (le16_to_cpu(((struct ext4_fc_tl *)start)->fc_tag)
			!= EXT4_FC_TAG_HEAD)
			return 0;
	}

	if (off != state->fc_replay_expected_off) {
		ret = -EFSCORRUPTED;
		goto out_err;
	}

	state->fc_replay_expected_off++;
	for (cur = start; cur <= end - EXT4_FC_TAG_BASE_LEN;
	     cur = cur + EXT4_FC_TAG_BASE_LEN + tl.fc_len) {
		ext4_fc_get_tl(&tl, cur);
		val = cur + EXT4_FC_TAG_BASE_LEN;
		if (tl.fc_len > end - val ||
		    !ext4_fc_value_len_isvalid(sbi, tl.fc_tag, tl.fc_len)) {
			ret = state->fc_replay_num_tags ?
				JBD2_FC_REPLAY_STOP : -ECANCELED;
			goto out_err;
		}
		ext4_debug("Scan phase, tag:%s, blk %lld\n",
			   tag2str(tl.fc_tag), bh->b_blocknr);
		switch (tl.fc_tag) {
		case EXT4_FC_TAG_ADD_RANGE:
			memcpy(&ext, val, sizeof(ext));
			ex = (struct ext4_extent *)&ext.fc_ex;
			ret = ext4_fc_record_regions(sb,
				le32_to_cpu(ext.fc_ino),
				le32_to_cpu(ex->ee_block), ext4_ext_pblock(ex),
				ext4_ext_get_actual_len(ex), 0);
			if (ret < 0)
				break;
			ret = JBD2_FC_REPLAY_CONTINUE;
			fallthrough;
		case EXT4_FC_TAG_DEL_RANGE:
		case EXT4_FC_TAG_LINK:
		case EXT4_FC_TAG_UNLINK:
		case EXT4_FC_TAG_CREAT:
		case EXT4_FC_TAG_INODE:
		case EXT4_FC_TAG_PAD:
			state->fc_cur_tag++;
			state->fc_crc = ext4_chksum(sbi, state->fc_crc, cur,
				EXT4_FC_TAG_BASE_LEN + tl.fc_len);
			break;
		case EXT4_FC_TAG_TAIL:
			state->fc_cur_tag++;
			memcpy(&tail, val, sizeof(tail));
			state->fc_crc = ext4_chksum(sbi, state->fc_crc, cur,
						EXT4_FC_TAG_BASE_LEN +
						offsetof(struct ext4_fc_tail,
						fc_crc));
			if (le32_to_cpu(tail.fc_tid) == expected_tid &&
				le32_to_cpu(tail.fc_crc) == state->fc_crc) {
				state->fc_replay_num_tags = state->fc_cur_tag;
				state->fc_regions_valid =
					state->fc_regions_used;
			} else {
				ret = state->fc_replay_num_tags ?
					JBD2_FC_REPLAY_STOP : -EFSBADCRC;
			}
			state->fc_crc = 0;
			break;
		case EXT4_FC_TAG_HEAD:
			memcpy(&head, val, sizeof(head));
			if (le32_to_cpu(head.fc_features) &
				~EXT4_FC_SUPPORTED_FEATURES) {
				ret = -EOPNOTSUPP;
				break;
			}
			if (le32_to_cpu(head.fc_tid) != expected_tid) {
				ret = JBD2_FC_REPLAY_STOP;
				break;
			}
			state->fc_cur_tag++;
			state->fc_crc = ext4_chksum(sbi, state->fc_crc, cur,
				EXT4_FC_TAG_BASE_LEN + tl.fc_len);
			break;
		default:
			ret = state->fc_replay_num_tags ?
				JBD2_FC_REPLAY_STOP : -ECANCELED;
		}
		if (ret < 0 || ret == JBD2_FC_REPLAY_STOP)
			break;
	}

out_err:
	trace_ext4_fc_replay_scan(sb, ret, off);
	return ret;
}

/*
 * Main recovery path entry point.
 * The meaning of return codes is similar as above.
 */
static int ext4_fc_replay(journal_t *journal, struct buffer_head *bh,
				enum passtype pass, int off, tid_t expected_tid)
{
	struct super_block *sb = journal->j_private;
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	struct ext4_fc_tl tl;
	__u8 *start, *end, *cur, *val;
	int ret = JBD2_FC_REPLAY_CONTINUE;
	struct ext4_fc_replay_state *state = &sbi->s_fc_replay_state;
	struct ext4_fc_tail tail;

	if (pass == PASS_SCAN) {
		state->fc_current_pass = PASS_SCAN;
		return ext4_fc_replay_scan(journal, bh, off, expected_tid);
	}

	if (state->fc_current_pass != pass) {
		state->fc_current_pass = pass;
		sbi->s_mount_state |= EXT4_FC_REPLAY;
	}
	if (!sbi->s_fc_replay_state.fc_replay_num_tags) {
		ext4_debug("Replay stops\n");
		ext4_fc_set_bitmaps_and_counters(sb);
		return 0;
	}

#ifdef CONFIG_EXT4_DEBUG
	if (sbi->s_fc_debug_max_replay && off >= sbi->s_fc_debug_max_replay) {
		pr_warn("Dropping fc block %d because max_replay set\n", off);
		return JBD2_FC_REPLAY_STOP;
	}
#endif

	start = (u8 *)bh->b_data;
	end = start + journal->j_blocksize;

	for (cur = start; cur <= end - EXT4_FC_TAG_BASE_LEN;
	     cur = cur + EXT4_FC_TAG_BASE_LEN + tl.fc_len) {
		ext4_fc_get_tl(&tl, cur);
		val = cur + EXT4_FC_TAG_BASE_LEN;

		if (state->fc_replay_num_tags == 0) {
			ret = JBD2_FC_REPLAY_STOP;
			ext4_fc_set_bitmaps_and_counters(sb);
			break;
		}

		ext4_debug("Replay phase, tag:%s\n", tag2str(tl.fc_tag));
		state->fc_replay_num_tags--;
		switch (tl.fc_tag) {
		case EXT4_FC_TAG_LINK:
			ret = ext4_fc_replay_link(sb, &tl, val);
			break;
		case EXT4_FC_TAG_UNLINK:
			ret = ext4_fc_replay_unlink(sb, &tl, val);
			break;
		case EXT4_FC_TAG_ADD_RANGE:
			ret = ext4_fc_replay_add_range(sb, &tl, val);
			break;
		case EXT4_FC_TAG_CREAT:
			ret = ext4_fc_replay_create(sb, &tl, val);
			break;
		case EXT4_FC_TAG_DEL_RANGE:
			ret = ext4_fc_replay_del_range(sb, &tl, val);
			break;
		case EXT4_FC_TAG_INODE:
			ret = ext4_fc_replay_inode(sb, &tl, val);
			break;
		case EXT4_FC_TAG_PAD:
			trace_ext4_fc_replay(sb, EXT4_FC_TAG_PAD, 0,
					     tl.fc_len, 0);
			break;
		case EXT4_FC_TAG_TAIL:
			trace_ext4_fc_replay(sb, EXT4_FC_TAG_TAIL,
					     0, tl.fc_len, 0);
			memcpy(&tail, val, sizeof(tail));
			WARN_ON(le32_to_cpu(tail.fc_tid) != expected_tid);
			break;
		case EXT4_FC_TAG_HEAD:
			break;
		default:
			trace_ext4_fc_replay(sb, tl.fc_tag, 0, tl.fc_len, 0);
			ret = -ECANCELED;
			break;
		}
		if (ret < 0)
			break;
		ret = JBD2_FC_REPLAY_CONTINUE;
	}
	return ret;
}

void ext4_fc_init(struct super_block *sb, journal_t *journal)
{
	/*
	 * We set replay callback even if fast commit disabled because we may
	 * could still have fast commit blocks that need to be replayed even if
	 * fast commit has now been turned off.
	 */
	journal->j_fc_replay_callback = ext4_fc_replay;
	if (!test_opt2(sb, JOURNAL_FAST_COMMIT))
		return;
	journal->j_fc_cleanup_callback = ext4_fc_cleanup;
}

static const char * const fc_ineligible_reasons[] = {
	[EXT4_FC_REASON_XATTR] = "Extended attributes changed",
	[EXT4_FC_REASON_CROSS_RENAME] = "Cross rename",
	[EXT4_FC_REASON_JOURNAL_FLAG_CHANGE] = "Journal flag changed",
	[EXT4_FC_REASON_NOMEM] = "Insufficient memory",
	[EXT4_FC_REASON_SWAP_BOOT] = "Swap boot",
	[EXT4_FC_REASON_RESIZE] = "Resize",
	[EXT4_FC_REASON_RENAME_DIR] = "Dir renamed",
	[EXT4_FC_REASON_FALLOC_RANGE] = "Falloc range op",
	[EXT4_FC_REASON_INODE_JOURNAL_DATA] = "Data journalling",
	[EXT4_FC_REASON_ENCRYPTED_FILENAME] = "Encrypted filename",
};

int ext4_fc_info_show(struct seq_file *seq, void *v)
{
	struct ext4_sb_info *sbi = EXT4_SB((struct super_block *)seq->private);
	struct ext4_fc_stats *stats = &sbi->s_fc_stats;
	int i;

	if (v != SEQ_START_TOKEN)
		return 0;

	seq_printf(seq,
		"fc stats:\n%ld commits\n%ld ineligible\n%ld numblks\n%lluus avg_commit_time\n",
		   stats->fc_num_commits, stats->fc_ineligible_commits,
		   stats->fc_numblks,
		   div_u64(stats->s_fc_avg_commit_time, 1000));
	seq_puts(seq, "Ineligible reasons:\n");
	for (i = 0; i < EXT4_FC_REASON_MAX; i++)
		seq_printf(seq, "\"%s\":\t%d\n", fc_ineligible_reasons[i],
			stats->fc_ineligible_reason_count[i]);

	return 0;
}

int __init ext4_fc_init_dentry_cache(void)
{
	ext4_fc_dentry_cachep = KMEM_CACHE(ext4_fc_dentry_update,
					   SLAB_RECLAIM_ACCOUNT);

	if (ext4_fc_dentry_cachep == NULL)
		return -ENOMEM;

	return 0;
}

void ext4_fc_destroy_dentry_cache(void)
{
	kmem_cache_destroy(ext4_fc_dentry_cachep);
}