summaryrefslogtreecommitdiffstats
path: root/fs/ext4/resize.c
blob: 6dfe9ccae0c50c2ba92cc24e9b7489072f4e42a4 (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
// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/fs/ext4/resize.c
 *
 * Support for resizing an ext4 filesystem while it is mounted.
 *
 * Copyright (C) 2001, 2002 Andreas Dilger <adilger@clusterfs.com>
 *
 * This could probably be made into a module, because it is not often in use.
 */


#define EXT4FS_DEBUG

#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/jiffies.h>

#include "ext4_jbd2.h"

struct ext4_rcu_ptr {
	struct rcu_head rcu;
	void *ptr;
};

static void ext4_rcu_ptr_callback(struct rcu_head *head)
{
	struct ext4_rcu_ptr *ptr;

	ptr = container_of(head, struct ext4_rcu_ptr, rcu);
	kvfree(ptr->ptr);
	kfree(ptr);
}

void ext4_kvfree_array_rcu(void *to_free)
{
	struct ext4_rcu_ptr *ptr = kzalloc(sizeof(*ptr), GFP_KERNEL);

	if (ptr) {
		ptr->ptr = to_free;
		call_rcu(&ptr->rcu, ext4_rcu_ptr_callback);
		return;
	}
	synchronize_rcu();
	kvfree(to_free);
}

int ext4_resize_begin(struct super_block *sb)
{
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	int ret = 0;

	if (!capable(CAP_SYS_RESOURCE))
		return -EPERM;

	/*
	 * If the reserved GDT blocks is non-zero, the resize_inode feature
	 * should always be set.
	 */
	if (EXT4_SB(sb)->s_es->s_reserved_gdt_blocks &&
	    !ext4_has_feature_resize_inode(sb)) {
		ext4_error(sb, "resize_inode disabled but reserved GDT blocks non-zero");
		return -EFSCORRUPTED;
	}

	/*
	 * If we are not using the primary superblock/GDT copy don't resize,
         * because the user tools have no way of handling this.  Probably a
         * bad time to do it anyways.
         */
	if (EXT4_B2C(sbi, sbi->s_sbh->b_blocknr) !=
	    le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block)) {
		ext4_warning(sb, "won't resize using backup superblock at %llu",
			(unsigned long long)EXT4_SB(sb)->s_sbh->b_blocknr);
		return -EPERM;
	}

	/*
	 * We are not allowed to do online-resizing on a filesystem mounted
	 * with error, because it can destroy the filesystem easily.
	 */
	if (EXT4_SB(sb)->s_mount_state & EXT4_ERROR_FS) {
		ext4_warning(sb, "There are errors in the filesystem, "
			     "so online resizing is not allowed");
		return -EPERM;
	}

	if (ext4_has_feature_sparse_super2(sb)) {
		ext4_msg(sb, KERN_ERR, "Online resizing not supported with sparse_super2");
		return -EOPNOTSUPP;
	}

	if (test_and_set_bit_lock(EXT4_FLAGS_RESIZING,
				  &EXT4_SB(sb)->s_ext4_flags))
		ret = -EBUSY;

	return ret;
}

int ext4_resize_end(struct super_block *sb, bool update_backups)
{
	clear_bit_unlock(EXT4_FLAGS_RESIZING, &EXT4_SB(sb)->s_ext4_flags);
	smp_mb__after_atomic();
	if (update_backups)
		return ext4_update_overhead(sb, true);
	return 0;
}

static ext4_group_t ext4_meta_bg_first_group(struct super_block *sb,
					     ext4_group_t group) {
	return (group >> EXT4_DESC_PER_BLOCK_BITS(sb)) <<
	       EXT4_DESC_PER_BLOCK_BITS(sb);
}

static ext4_fsblk_t ext4_meta_bg_first_block_no(struct super_block *sb,
					     ext4_group_t group) {
	group = ext4_meta_bg_first_group(sb, group);
	return ext4_group_first_block_no(sb, group);
}

static ext4_grpblk_t ext4_group_overhead_blocks(struct super_block *sb,
						ext4_group_t group) {
	ext4_grpblk_t overhead;
	overhead = ext4_bg_num_gdb(sb, group);
	if (ext4_bg_has_super(sb, group))
		overhead += 1 +
			  le16_to_cpu(EXT4_SB(sb)->s_es->s_reserved_gdt_blocks);
	return overhead;
}

#define outside(b, first, last)	((b) < (first) || (b) >= (last))
#define inside(b, first, last)	((b) >= (first) && (b) < (last))

static int verify_group_input(struct super_block *sb,
			      struct ext4_new_group_data *input)
{
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	struct ext4_super_block *es = sbi->s_es;
	ext4_fsblk_t start = ext4_blocks_count(es);
	ext4_fsblk_t end = start + input->blocks_count;
	ext4_group_t group = input->group;
	ext4_fsblk_t itend = input->inode_table + sbi->s_itb_per_group;
	unsigned overhead;
	ext4_fsblk_t metaend;
	struct buffer_head *bh = NULL;
	ext4_grpblk_t free_blocks_count, offset;
	int err = -EINVAL;

	if (group != sbi->s_groups_count) {
		ext4_warning(sb, "Cannot add at group %u (only %u groups)",
			     input->group, sbi->s_groups_count);
		return -EINVAL;
	}

	overhead = ext4_group_overhead_blocks(sb, group);
	metaend = start + overhead;
	input->free_clusters_count = free_blocks_count =
		input->blocks_count - 2 - overhead - sbi->s_itb_per_group;

	if (test_opt(sb, DEBUG))
		printk(KERN_DEBUG "EXT4-fs: adding %s group %u: %u blocks "
		       "(%d free, %u reserved)\n",
		       ext4_bg_has_super(sb, input->group) ? "normal" :
		       "no-super", input->group, input->blocks_count,
		       free_blocks_count, input->reserved_blocks);

	ext4_get_group_no_and_offset(sb, start, NULL, &offset);
	if (offset != 0)
			ext4_warning(sb, "Last group not full");
	else if (input->reserved_blocks > input->blocks_count / 5)
		ext4_warning(sb, "Reserved blocks too high (%u)",
			     input->reserved_blocks);
	else if (free_blocks_count < 0)
		ext4_warning(sb, "Bad blocks count %u",
			     input->blocks_count);
	else if (IS_ERR(bh = ext4_sb_bread(sb, end - 1, 0))) {
		err = PTR_ERR(bh);
		bh = NULL;
		ext4_warning(sb, "Cannot read last block (%llu)",
			     end - 1);
	} else if (outside(input->block_bitmap, start, end))
		ext4_warning(sb, "Block bitmap not in group (block %llu)",
			     (unsigned long long)input->block_bitmap);
	else if (outside(input->inode_bitmap, start, end))
		ext4_warning(sb, "Inode bitmap not in group (block %llu)",
			     (unsigned long long)input->inode_bitmap);
	else if (outside(input->inode_table, start, end) ||
		 outside(itend - 1, start, end))
		ext4_warning(sb, "Inode table not in group (blocks %llu-%llu)",
			     (unsigned long long)input->inode_table, itend - 1);
	else if (input->inode_bitmap == input->block_bitmap)
		ext4_warning(sb, "Block bitmap same as inode bitmap (%llu)",
			     (unsigned long long)input->block_bitmap);
	else if (inside(input->block_bitmap, input->inode_table, itend))
		ext4_warning(sb, "Block bitmap (%llu) in inode table "
			     "(%llu-%llu)",
			     (unsigned long long)input->block_bitmap,
			     (unsigned long long)input->inode_table, itend - 1);
	else if (inside(input->inode_bitmap, input->inode_table, itend))
		ext4_warning(sb, "Inode bitmap (%llu) in inode table "
			     "(%llu-%llu)",
			     (unsigned long long)input->inode_bitmap,
			     (unsigned long long)input->inode_table, itend - 1);
	else if (inside(input->block_bitmap, start, metaend))
		ext4_warning(sb, "Block bitmap (%llu) in GDT table (%llu-%llu)",
			     (unsigned long long)input->block_bitmap,
			     start, metaend - 1);
	else if (inside(input->inode_bitmap, start, metaend))
		ext4_warning(sb, "Inode bitmap (%llu) in GDT table (%llu-%llu)",
			     (unsigned long long)input->inode_bitmap,
			     start, metaend - 1);
	else if (inside(input->inode_table, start, metaend) ||
		 inside(itend - 1, start, metaend))
		ext4_warning(sb, "Inode table (%llu-%llu) overlaps GDT table "
			     "(%llu-%llu)",
			     (unsigned long long)input->inode_table,
			     itend - 1, start, metaend - 1);
	else
		err = 0;
	brelse(bh);

	return err;
}

/*
 * ext4_new_flex_group_data is used by 64bit-resize interface to add a flex
 * group each time.
 */
struct ext4_new_flex_group_data {
	struct ext4_new_group_data *groups;	/* new_group_data for groups
						   in the flex group */
	__u16 *bg_flags;			/* block group flags of groups
						   in @groups */
	ext4_group_t count;			/* number of groups in @groups
						 */
};

/*
 * alloc_flex_gd() allocates a ext4_new_flex_group_data with size of
 * @flexbg_size.
 *
 * Returns NULL on failure otherwise address of the allocated structure.
 */
static struct ext4_new_flex_group_data *alloc_flex_gd(unsigned long flexbg_size)
{
	struct ext4_new_flex_group_data *flex_gd;

	flex_gd = kmalloc(sizeof(*flex_gd), GFP_NOFS);
	if (flex_gd == NULL)
		goto out3;

	if (flexbg_size >= UINT_MAX / sizeof(struct ext4_new_group_data))
		goto out2;
	flex_gd->count = flexbg_size;

	flex_gd->groups = kmalloc_array(flexbg_size,
					sizeof(struct ext4_new_group_data),
					GFP_NOFS);
	if (flex_gd->groups == NULL)
		goto out2;

	flex_gd->bg_flags = kmalloc_array(flexbg_size, sizeof(__u16),
					  GFP_NOFS);
	if (flex_gd->bg_flags == NULL)
		goto out1;

	return flex_gd;

out1:
	kfree(flex_gd->groups);
out2:
	kfree(flex_gd);
out3:
	return NULL;
}

static void free_flex_gd(struct ext4_new_flex_group_data *flex_gd)
{
	kfree(flex_gd->bg_flags);
	kfree(flex_gd->groups);
	kfree(flex_gd);
}

/*
 * ext4_alloc_group_tables() allocates block bitmaps, inode bitmaps
 * and inode tables for a flex group.
 *
 * This function is used by 64bit-resize.  Note that this function allocates
 * group tables from the 1st group of groups contained by @flexgd, which may
 * be a partial of a flex group.
 *
 * @sb: super block of fs to which the groups belongs
 *
 * Returns 0 on a successful allocation of the metadata blocks in the
 * block group.
 */
static int ext4_alloc_group_tables(struct super_block *sb,
				struct ext4_new_flex_group_data *flex_gd,
				int flexbg_size)
{
	struct ext4_new_group_data *group_data = flex_gd->groups;
	ext4_fsblk_t start_blk;
	ext4_fsblk_t last_blk;
	ext4_group_t src_group;
	ext4_group_t bb_index = 0;
	ext4_group_t ib_index = 0;
	ext4_group_t it_index = 0;
	ext4_group_t group;
	ext4_group_t last_group;
	unsigned overhead;
	__u16 uninit_mask = (flexbg_size > 1) ? ~EXT4_BG_BLOCK_UNINIT : ~0;
	int i;

	BUG_ON(flex_gd->count == 0 || group_data == NULL);

	src_group = group_data[0].group;
	last_group  = src_group + flex_gd->count - 1;

	BUG_ON((flexbg_size > 1) && ((src_group & ~(flexbg_size - 1)) !=
	       (last_group & ~(flexbg_size - 1))));
next_group:
	group = group_data[0].group;
	if (src_group >= group_data[0].group + flex_gd->count)
		return -ENOSPC;
	start_blk = ext4_group_first_block_no(sb, src_group);
	last_blk = start_blk + group_data[src_group - group].blocks_count;

	overhead = ext4_group_overhead_blocks(sb, src_group);

	start_blk += overhead;

	/* We collect contiguous blocks as much as possible. */
	src_group++;
	for (; src_group <= last_group; src_group++) {
		overhead = ext4_group_overhead_blocks(sb, src_group);
		if (overhead == 0)
			last_blk += group_data[src_group - group].blocks_count;
		else
			break;
	}

	/* Allocate block bitmaps */
	for (; bb_index < flex_gd->count; bb_index++) {
		if (start_blk >= last_blk)
			goto next_group;
		group_data[bb_index].block_bitmap = start_blk++;
		group = ext4_get_group_number(sb, start_blk - 1);
		group -= group_data[0].group;
		group_data[group].mdata_blocks++;
		flex_gd->bg_flags[group] &= uninit_mask;
	}

	/* Allocate inode bitmaps */
	for (; ib_index < flex_gd->count; ib_index++) {
		if (start_blk >= last_blk)
			goto next_group;
		group_data[ib_index].inode_bitmap = start_blk++;
		group = ext4_get_group_number(sb, start_blk - 1);
		group -= group_data[0].group;
		group_data[group].mdata_blocks++;
		flex_gd->bg_flags[group] &= uninit_mask;
	}

	/* Allocate inode tables */
	for (; it_index < flex_gd->count; it_index++) {
		unsigned int itb = EXT4_SB(sb)->s_itb_per_group;
		ext4_fsblk_t next_group_start;

		if (start_blk + itb > last_blk)
			goto next_group;
		group_data[it_index].inode_table = start_blk;
		group = ext4_get_group_number(sb, start_blk);
		next_group_start = ext4_group_first_block_no(sb, group + 1);
		group -= group_data[0].group;

		if (start_blk + itb > next_group_start) {
			flex_gd->bg_flags[group + 1] &= uninit_mask;
			overhead = start_blk + itb - next_group_start;
			group_data[group + 1].mdata_blocks += overhead;
			itb -= overhead;
		}

		group_data[group].mdata_blocks += itb;
		flex_gd->bg_flags[group] &= uninit_mask;
		start_blk += EXT4_SB(sb)->s_itb_per_group;
	}

	/* Update free clusters count to exclude metadata blocks */
	for (i = 0; i < flex_gd->count; i++) {
		group_data[i].free_clusters_count -=
				EXT4_NUM_B2C(EXT4_SB(sb),
					     group_data[i].mdata_blocks);
	}

	if (test_opt(sb, DEBUG)) {
		int i;
		group = group_data[0].group;

		printk(KERN_DEBUG "EXT4-fs: adding a flex group with "
		       "%d groups, flexbg size is %d:\n", flex_gd->count,
		       flexbg_size);

		for (i = 0; i < flex_gd->count; i++) {
			ext4_debug(
			       "adding %s group %u: %u blocks (%d free, %d mdata blocks)\n",
			       ext4_bg_has_super(sb, group + i) ? "normal" :
			       "no-super", group + i,
			       group_data[i].blocks_count,
			       group_data[i].free_clusters_count,
			       group_data[i].mdata_blocks);
		}
	}
	return 0;
}

static struct buffer_head *bclean(handle_t *handle, struct super_block *sb,
				  ext4_fsblk_t blk)
{
	struct buffer_head *bh;
	int err;

	bh = sb_getblk(sb, blk);
	if (unlikely(!bh))
		return ERR_PTR(-ENOMEM);
	BUFFER_TRACE(bh, "get_write_access");
	err = ext4_journal_get_write_access(handle, sb, bh, EXT4_JTR_NONE);
	if (err) {
		brelse(bh);
		bh = ERR_PTR(err);
	} else {
		memset(bh->b_data, 0, sb->s_blocksize);
		set_buffer_uptodate(bh);
	}

	return bh;
}

static int ext4_resize_ensure_credits_batch(handle_t *handle, int credits)
{
	return ext4_journal_ensure_credits_fn(handle, credits,
		EXT4_MAX_TRANS_DATA, 0, 0);
}

/*
 * set_flexbg_block_bitmap() mark clusters [@first_cluster, @last_cluster] used.
 *
 * Helper function for ext4_setup_new_group_blocks() which set .
 *
 * @sb: super block
 * @handle: journal handle
 * @flex_gd: flex group data
 */
static int set_flexbg_block_bitmap(struct super_block *sb, handle_t *handle,
			struct ext4_new_flex_group_data *flex_gd,
			ext4_fsblk_t first_cluster, ext4_fsblk_t last_cluster)
{
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	ext4_group_t count = last_cluster - first_cluster + 1;
	ext4_group_t count2;

	ext4_debug("mark clusters [%llu-%llu] used\n", first_cluster,
		   last_cluster);
	for (count2 = count; count > 0;
	     count -= count2, first_cluster += count2) {
		ext4_fsblk_t start;
		struct buffer_head *bh;
		ext4_group_t group;
		int err;

		group = ext4_get_group_number(sb, EXT4_C2B(sbi, first_cluster));
		start = EXT4_B2C(sbi, ext4_group_first_block_no(sb, group));
		group -= flex_gd->groups[0].group;

		count2 = EXT4_CLUSTERS_PER_GROUP(sb) - (first_cluster - start);
		if (count2 > count)
			count2 = count;

		if (flex_gd->bg_flags[group] & EXT4_BG_BLOCK_UNINIT) {
			BUG_ON(flex_gd->count > 1);
			continue;
		}

		err = ext4_resize_ensure_credits_batch(handle, 1);
		if (err < 0)
			return err;

		bh = sb_getblk(sb, flex_gd->groups[group].block_bitmap);
		if (unlikely(!bh))
			return -ENOMEM;

		BUFFER_TRACE(bh, "get_write_access");
		err = ext4_journal_get_write_access(handle, sb, bh,
						    EXT4_JTR_NONE);
		if (err) {
			brelse(bh);
			return err;
		}
		ext4_debug("mark block bitmap %#04llx (+%llu/%u)\n",
			   first_cluster, first_cluster - start, count2);
		mb_set_bits(bh->b_data, first_cluster - start, count2);

		err = ext4_handle_dirty_metadata(handle, NULL, bh);
		brelse(bh);
		if (unlikely(err))
			return err;
	}

	return 0;
}

/*
 * Set up the block and inode bitmaps, and the inode table for the new groups.
 * This doesn't need to be part of the main transaction, since we are only
 * changing blocks outside the actual filesystem.  We still do journaling to
 * ensure the recovery is correct in case of a failure just after resize.
 * If any part of this fails, we simply abort the resize.
 *
 * setup_new_flex_group_blocks handles a flex group as follow:
 *  1. copy super block and GDT, and initialize group tables if necessary.
 *     In this step, we only set bits in blocks bitmaps for blocks taken by
 *     super block and GDT.
 *  2. allocate group tables in block bitmaps, that is, set bits in block
 *     bitmap for blocks taken by group tables.
 */
static int setup_new_flex_group_blocks(struct super_block *sb,
				struct ext4_new_flex_group_data *flex_gd)
{
	int group_table_count[] = {1, 1, EXT4_SB(sb)->s_itb_per_group};
	ext4_fsblk_t start;
	ext4_fsblk_t block;
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	struct ext4_super_block *es = sbi->s_es;
	struct ext4_new_group_data *group_data = flex_gd->groups;
	__u16 *bg_flags = flex_gd->bg_flags;
	handle_t *handle;
	ext4_group_t group, count;
	struct buffer_head *bh = NULL;
	int reserved_gdb, i, j, err = 0, err2;
	int meta_bg;

	BUG_ON(!flex_gd->count || !group_data ||
	       group_data[0].group != sbi->s_groups_count);

	reserved_gdb = le16_to_cpu(es->s_reserved_gdt_blocks);
	meta_bg = ext4_has_feature_meta_bg(sb);

	/* This transaction may be extended/restarted along the way */
	handle = ext4_journal_start_sb(sb, EXT4_HT_RESIZE, EXT4_MAX_TRANS_DATA);
	if (IS_ERR(handle))
		return PTR_ERR(handle);

	group = group_data[0].group;
	for (i = 0; i < flex_gd->count; i++, group++) {
		unsigned long gdblocks;
		ext4_grpblk_t overhead;

		gdblocks = ext4_bg_num_gdb(sb, group);
		start = ext4_group_first_block_no(sb, group);

		if (meta_bg == 0 && !ext4_bg_has_super(sb, group))
			goto handle_itb;

		if (meta_bg == 1) {
			ext4_group_t first_group;
			first_group = ext4_meta_bg_first_group(sb, group);
			if (first_group != group + 1 &&
			    first_group != group + EXT4_DESC_PER_BLOCK(sb) - 1)
				goto handle_itb;
		}

		block = start + ext4_bg_has_super(sb, group);
		/* Copy all of the GDT blocks into the backup in this group */
		for (j = 0; j < gdblocks; j++, block++) {
			struct buffer_head *gdb;

			ext4_debug("update backup group %#04llx\n", block);
			err = ext4_resize_ensure_credits_batch(handle, 1);
			if (err < 0)
				goto out;

			gdb = sb_getblk(sb, block);
			if (unlikely(!gdb)) {
				err = -ENOMEM;
				goto out;
			}

			BUFFER_TRACE(gdb, "get_write_access");
			err = ext4_journal_get_write_access(handle, sb, gdb,
							    EXT4_JTR_NONE);
			if (err) {
				brelse(gdb);
				goto out;
			}
			memcpy(gdb->b_data, sbi_array_rcu_deref(sbi,
				s_group_desc, j)->b_data, gdb->b_size);
			set_buffer_uptodate(gdb);

			err = ext4_handle_dirty_metadata(handle, NULL, gdb);
			if (unlikely(err)) {
				brelse(gdb);
				goto out;
			}
			brelse(gdb);
		}

		/* Zero out all of the reserved backup group descriptor
		 * table blocks
		 */
		if (ext4_bg_has_super(sb, group)) {
			err = sb_issue_zeroout(sb, gdblocks + start + 1,
					reserved_gdb, GFP_NOFS);
			if (err)
				goto out;
		}

handle_itb:
		/* Initialize group tables of the grop @group */
		if (!(bg_flags[i] & EXT4_BG_INODE_ZEROED))
			goto handle_bb;

		/* Zero out all of the inode table blocks */
		block = group_data[i].inode_table;
		ext4_debug("clear inode table blocks %#04llx -> %#04lx\n",
			   block, sbi->s_itb_per_group);
		err = sb_issue_zeroout(sb, block, sbi->s_itb_per_group,
				       GFP_NOFS);
		if (err)
			goto out;

handle_bb:
		if (bg_flags[i] & EXT4_BG_BLOCK_UNINIT)
			goto handle_ib;

		/* Initialize block bitmap of the @group */
		block = group_data[i].block_bitmap;
		err = ext4_resize_ensure_credits_batch(handle, 1);
		if (err < 0)
			goto out;

		bh = bclean(handle, sb, block);
		if (IS_ERR(bh)) {
			err = PTR_ERR(bh);
			goto out;
		}
		overhead = ext4_group_overhead_blocks(sb, group);
		if (overhead != 0) {
			ext4_debug("mark backup superblock %#04llx (+0)\n",
				   start);
			mb_set_bits(bh->b_data, 0,
				      EXT4_NUM_B2C(sbi, overhead));
		}
		ext4_mark_bitmap_end(EXT4_B2C(sbi, group_data[i].blocks_count),
				     sb->s_blocksize * 8, bh->b_data);
		err = ext4_handle_dirty_metadata(handle, NULL, bh);
		brelse(bh);
		if (err)
			goto out;

handle_ib:
		if (bg_flags[i] & EXT4_BG_INODE_UNINIT)
			continue;

		/* Initialize inode bitmap of the @group */
		block = group_data[i].inode_bitmap;
		err = ext4_resize_ensure_credits_batch(handle, 1);
		if (err < 0)
			goto out;
		/* Mark unused entries in inode bitmap used */
		bh = bclean(handle, sb, block);
		if (IS_ERR(bh)) {
			err = PTR_ERR(bh);
			goto out;
		}

		ext4_mark_bitmap_end(EXT4_INODES_PER_GROUP(sb),
				     sb->s_blocksize * 8, bh->b_data);
		err = ext4_handle_dirty_metadata(handle, NULL, bh);
		brelse(bh);
		if (err)
			goto out;
	}

	/* Mark group tables in block bitmap */
	for (j = 0; j < GROUP_TABLE_COUNT; j++) {
		count = group_table_count[j];
		start = (&group_data[0].block_bitmap)[j];
		block = start;
		for (i = 1; i < flex_gd->count; i++) {
			block += group_table_count[j];
			if (block == (&group_data[i].block_bitmap)[j]) {
				count += group_table_count[j];
				continue;
			}
			err = set_flexbg_block_bitmap(sb, handle,
						      flex_gd,
						      EXT4_B2C(sbi, start),
						      EXT4_B2C(sbi,
							       start + count
							       - 1));
			if (err)
				goto out;
			count = group_table_count[j];
			start = (&group_data[i].block_bitmap)[j];
			block = start;
		}

		if (count) {
			err = set_flexbg_block_bitmap(sb, handle,
						      flex_gd,
						      EXT4_B2C(sbi, start),
						      EXT4_B2C(sbi,
							       start + count
							       - 1));
			if (err)
				goto out;
		}
	}

out:
	err2 = ext4_journal_stop(handle);
	if (err2 && !err)
		err = err2;

	return err;
}

/*
 * Iterate through the groups which hold BACKUP superblock/GDT copies in an
 * ext4 filesystem.  The counters should be initialized to 1, 5, and 7 before
 * calling this for the first time.  In a sparse filesystem it will be the
 * sequence of powers of 3, 5, and 7: 1, 3, 5, 7, 9, 25, 27, 49, 81, ...
 * For a non-sparse filesystem it will be every group: 1, 2, 3, 4, ...
 */
unsigned int ext4_list_backups(struct super_block *sb, unsigned int *three,
			       unsigned int *five, unsigned int *seven)
{
	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
	unsigned int *min = three;
	int mult = 3;
	unsigned int ret;

	if (ext4_has_feature_sparse_super2(sb)) {
		do {
			if (*min > 2)
				return UINT_MAX;
			ret = le32_to_cpu(es->s_backup_bgs[*min - 1]);
			*min += 1;
		} while (!ret);
		return ret;
	}

	if (!ext4_has_feature_sparse_super(sb)) {
		ret = *min;
		*min += 1;
		return ret;
	}

	if (*five < *min) {
		min = five;
		mult = 5;
	}
	if (*seven < *min) {
		min = seven;
		mult = 7;
	}

	ret = *min;
	*min *= mult;

	return ret;
}

/*
 * Check that all of the backup GDT blocks are held in the primary GDT block.
 * It is assumed that they are stored in group order.  Returns the number of
 * groups in current filesystem that have BACKUPS, or -ve error code.
 */
static int verify_reserved_gdb(struct super_block *sb,
			       ext4_group_t end,
			       struct buffer_head *primary)
{
	const ext4_fsblk_t blk = primary->b_blocknr;
	unsigned three = 1;
	unsigned five = 5;
	unsigned seven = 7;
	unsigned grp;
	__le32 *p = (__le32 *)primary->b_data;
	int gdbackups = 0;

	while ((grp = ext4_list_backups(sb, &three, &five, &seven)) < end) {
		if (le32_to_cpu(*p++) !=
		    grp * EXT4_BLOCKS_PER_GROUP(sb) + blk){
			ext4_warning(sb, "reserved GDT %llu"
				     " missing grp %d (%llu)",
				     blk, grp,
				     grp *
				     (ext4_fsblk_t)EXT4_BLOCKS_PER_GROUP(sb) +
				     blk);
			return -EINVAL;
		}
		if (++gdbackups > EXT4_ADDR_PER_BLOCK(sb))
			return -EFBIG;
	}

	return gdbackups;
}

/*
 * Called when we need to bring a reserved group descriptor table block into
 * use from the resize inode.  The primary copy of the new GDT block currently
 * is an indirect block (under the double indirect block in the resize inode).
 * The new backup GDT blocks will be stored as leaf blocks in this indirect
 * block, in group order.  Even though we know all the block numbers we need,
 * we check to ensure that the resize inode has actually reserved these blocks.
 *
 * Don't need to update the block bitmaps because the blocks are still in use.
 *
 * We get all of the error cases out of the way, so that we are sure to not
 * fail once we start modifying the data on disk, because JBD has no rollback.
 */
static int add_new_gdb(handle_t *handle, struct inode *inode,
		       ext4_group_t group)
{
	struct super_block *sb = inode->i_sb;
	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
	unsigned long gdb_num = group / EXT4_DESC_PER_BLOCK(sb);
	ext4_fsblk_t gdblock = EXT4_SB(sb)->s_sbh->b_blocknr + 1 + gdb_num;
	struct buffer_head **o_group_desc, **n_group_desc = NULL;
	struct buffer_head *dind = NULL;
	struct buffer_head *gdb_bh = NULL;
	int gdbackups;
	struct ext4_iloc iloc = { .bh = NULL };
	__le32 *data;
	int err;

	if (test_opt(sb, DEBUG))
		printk(KERN_DEBUG
		       "EXT4-fs: ext4_add_new_gdb: adding group block %lu\n",
		       gdb_num);

	gdb_bh = ext4_sb_bread(sb, gdblock, 0);
	if (IS_ERR(gdb_bh))
		return PTR_ERR(gdb_bh);

	gdbackups = verify_reserved_gdb(sb, group, gdb_bh);
	if (gdbackups < 0) {
		err = gdbackups;
		goto errout;
	}

	data = EXT4_I(inode)->i_data + EXT4_DIND_BLOCK;
	dind = ext4_sb_bread(sb, le32_to_cpu(*data), 0);
	if (IS_ERR(dind)) {
		err = PTR_ERR(dind);
		dind = NULL;
		goto errout;
	}

	data = (__le32 *)dind->b_data;
	if (le32_to_cpu(data[gdb_num % EXT4_ADDR_PER_BLOCK(sb)]) != gdblock) {
		ext4_warning(sb, "new group %u GDT block %llu not reserved",
			     group, gdblock);
		err = -EINVAL;
		goto errout;
	}

	BUFFER_TRACE(EXT4_SB(sb)->s_sbh, "get_write_access");
	err = ext4_journal_get_write_access(handle, sb, EXT4_SB(sb)->s_sbh,
					    EXT4_JTR_NONE);
	if (unlikely(err))
		goto errout;

	BUFFER_TRACE(gdb_bh, "get_write_access");
	err = ext4_journal_get_write_access(handle, sb, gdb_bh, EXT4_JTR_NONE);
	if (unlikely(err))
		goto errout;

	BUFFER_TRACE(dind, "get_write_access");
	err = ext4_journal_get_write_access(handle, sb, dind, EXT4_JTR_NONE);
	if (unlikely(err)) {
		ext4_std_error(sb, err);
		goto errout;
	}

	/* ext4_reserve_inode_write() gets a reference on the iloc */
	err = ext4_reserve_inode_write(handle, inode, &iloc);
	if (unlikely(err))
		goto errout;

	n_group_desc = kvmalloc((gdb_num + 1) * sizeof(struct buffer_head *),
				GFP_KERNEL);
	if (!n_group_desc) {
		err = -ENOMEM;
		ext4_warning(sb, "not enough memory for %lu groups",
			     gdb_num + 1);
		goto errout;
	}

	/*
	 * Finally, we have all of the possible failures behind us...
	 *
	 * Remove new GDT block from inode double-indirect block and clear out
	 * the new GDT block for use (which also "frees" the backup GDT blocks
	 * from the reserved inode).  We don't need to change the bitmaps for
	 * these blocks, because they are marked as in-use from being in the
	 * reserved inode, and will become GDT blocks (primary and backup).
	 */
	data[gdb_num % EXT4_ADDR_PER_BLOCK(sb)] = 0;
	err = ext4_handle_dirty_metadata(handle, NULL, dind);
	if (unlikely(err)) {
		ext4_std_error(sb, err);
		goto errout;
	}
	inode->i_blocks -= (gdbackups + 1) * sb->s_blocksize >>
			   (9 - EXT4_SB(sb)->s_cluster_bits);
	ext4_mark_iloc_dirty(handle, inode, &iloc);
	memset(gdb_bh->b_data, 0, sb->s_blocksize);
	err = ext4_handle_dirty_metadata(handle, NULL, gdb_bh);
	if (unlikely(err)) {
		ext4_std_error(sb, err);
		iloc.bh = NULL;
		goto errout;
	}
	brelse(dind);

	rcu_read_lock();
	o_group_desc = rcu_dereference(EXT4_SB(sb)->s_group_desc);
	memcpy(n_group_desc, o_group_desc,
	       EXT4_SB(sb)->s_gdb_count * sizeof(struct buffer_head *));
	rcu_read_unlock();
	n_group_desc[gdb_num] = gdb_bh;
	rcu_assign_pointer(EXT4_SB(sb)->s_group_desc, n_group_desc);
	EXT4_SB(sb)->s_gdb_count++;
	ext4_kvfree_array_rcu(o_group_desc);

	lock_buffer(EXT4_SB(sb)->s_sbh);
	le16_add_cpu(&es->s_reserved_gdt_blocks, -1);
	ext4_superblock_csum_set(sb);
	unlock_buffer(EXT4_SB(sb)->s_sbh);
	err = ext4_handle_dirty_metadata(handle, NULL, EXT4_SB(sb)->s_sbh);
	if (err)
		ext4_std_error(sb, err);
	return err;
errout:
	kvfree(n_group_desc);
	brelse(iloc.bh);
	brelse(dind);
	brelse(gdb_bh);

	ext4_debug("leaving with error %d\n", err);
	return err;
}

/*
 * add_new_gdb_meta_bg is the sister of add_new_gdb.
 */
static int add_new_gdb_meta_bg(struct super_block *sb,
			       handle_t *handle, ext4_group_t group) {
	ext4_fsblk_t gdblock;
	struct buffer_head *gdb_bh;
	struct buffer_head **o_group_desc, **n_group_desc;
	unsigned long gdb_num = group / EXT4_DESC_PER_BLOCK(sb);
	int err;

	gdblock = ext4_meta_bg_first_block_no(sb, group) +
		   ext4_bg_has_super(sb, group);
	gdb_bh = ext4_sb_bread(sb, gdblock, 0);
	if (IS_ERR(gdb_bh))
		return PTR_ERR(gdb_bh);
	n_group_desc = kvmalloc((gdb_num + 1) * sizeof(struct buffer_head *),
				GFP_KERNEL);
	if (!n_group_desc) {
		brelse(gdb_bh);
		err = -ENOMEM;
		ext4_warning(sb, "not enough memory for %lu groups",
			     gdb_num + 1);
		return err;
	}

	rcu_read_lock();
	o_group_desc = rcu_dereference(EXT4_SB(sb)->s_group_desc);
	memcpy(n_group_desc, o_group_desc,
	       EXT4_SB(sb)->s_gdb_count * sizeof(struct buffer_head *));
	rcu_read_unlock();
	n_group_desc[gdb_num] = gdb_bh;

	BUFFER_TRACE(gdb_bh, "get_write_access");
	err = ext4_journal_get_write_access(handle, sb, gdb_bh, EXT4_JTR_NONE);
	if (err) {
		kvfree(n_group_desc);
		brelse(gdb_bh);
		return err;
	}

	rcu_assign_pointer(EXT4_SB(sb)->s_group_desc, n_group_desc);
	EXT4_SB(sb)->s_gdb_count++;
	ext4_kvfree_array_rcu(o_group_desc);
	return err;
}

/*
 * Called when we are adding a new group which has a backup copy of each of
 * the GDT blocks (i.e. sparse group) and there are reserved GDT blocks.
 * We need to add these reserved backup GDT blocks to the resize inode, so
 * that they are kept for future resizing and not allocated to files.
 *
 * Each reserved backup GDT block will go into a different indirect block.
 * The indirect blocks are actually the primary reserved GDT blocks,
 * so we know in advance what their block numbers are.  We only get the
 * double-indirect block to verify it is pointing to the primary reserved
 * GDT blocks so we don't overwrite a data block by accident.  The reserved
 * backup GDT blocks are stored in their reserved primary GDT block.
 */
static int reserve_backup_gdb(handle_t *handle, struct inode *inode,
			      ext4_group_t group)
{
	struct super_block *sb = inode->i_sb;
	int reserved_gdb =le16_to_cpu(EXT4_SB(sb)->s_es->s_reserved_gdt_blocks);
	int cluster_bits = EXT4_SB(sb)->s_cluster_bits;
	struct buffer_head **primary;
	struct buffer_head *dind;
	struct ext4_iloc iloc;
	ext4_fsblk_t blk;
	__le32 *data, *end;
	int gdbackups = 0;
	int res, i;
	int err;

	primary = kmalloc_array(reserved_gdb, sizeof(*primary), GFP_NOFS);
	if (!primary)
		return -ENOMEM;

	data = EXT4_I(inode)->i_data + EXT4_DIND_BLOCK;
	dind = ext4_sb_bread(sb, le32_to_cpu(*data), 0);
	if (IS_ERR(dind)) {
		err = PTR_ERR(dind);
		dind = NULL;
		goto exit_free;
	}

	blk = EXT4_SB(sb)->s_sbh->b_blocknr + 1 + EXT4_SB(sb)->s_gdb_count;
	data = (__le32 *)dind->b_data + (EXT4_SB(sb)->s_gdb_count %
					 EXT4_ADDR_PER_BLOCK(sb));
	end = (__le32 *)dind->b_data + EXT4_ADDR_PER_BLOCK(sb);

	/* Get each reserved primary GDT block and verify it holds backups */
	for (res = 0; res < reserved_gdb; res++, blk++) {
		if (le32_to_cpu(*data) != blk) {
			ext4_warning(sb, "reserved block %llu"
				     " not at offset %ld",
				     blk,
				     (long)(data - (__le32 *)dind->b_data));
			err = -EINVAL;
			goto exit_bh;
		}
		primary[res] = ext4_sb_bread(sb, blk, 0);
		if (IS_ERR(primary[res])) {
			err = PTR_ERR(primary[res]);
			primary[res] = NULL;
			goto exit_bh;
		}
		gdbackups = verify_reserved_gdb(sb, group, primary[res]);
		if (gdbackups < 0) {
			brelse(primary[res]);
			err = gdbackups;
			goto exit_bh;
		}
		if (++data >= end)
			data = (__le32 *)dind->b_data;
	}

	for (i = 0; i < reserved_gdb; i++) {
		BUFFER_TRACE(primary[i], "get_write_access");
		if ((err = ext4_journal_get_write_access(handle, sb, primary[i],
							 EXT4_JTR_NONE)))
			goto exit_bh;
	}

	if ((err = ext4_reserve_inode_write(handle, inode, &iloc)))
		goto exit_bh;

	/*
	 * Finally we can add each of the reserved backup GDT blocks from
	 * the new group to its reserved primary GDT block.
	 */
	blk = group * EXT4_BLOCKS_PER_GROUP(sb);
	for (i = 0; i < reserved_gdb; i++) {
		int err2;
		data = (__le32 *)primary[i]->b_data;
		/* printk("reserving backup %lu[%u] = %lu\n",
		       primary[i]->b_blocknr, gdbackups,
		       blk + primary[i]->b_blocknr); */
		data[gdbackups] = cpu_to_le32(blk + primary[i]->b_blocknr);
		err2 = ext4_handle_dirty_metadata(handle, NULL, primary[i]);
		if (!err)
			err = err2;
	}

	inode->i_blocks += reserved_gdb * sb->s_blocksize >> (9 - cluster_bits);
	ext4_mark_iloc_dirty(handle, inode, &iloc);

exit_bh:
	while (--res >= 0)
		brelse(primary[res]);
	brelse(dind);

exit_free:
	kfree(primary);

	return err;
}

/*
 * Update the backup copies of the ext4 metadata.  These don't need to be part
 * of the main resize transaction, because e2fsck will re-write them if there
 * is a problem (basically only OOM will cause a problem).  However, we
 * _should_ update the backups if possible, in case the primary gets trashed
 * for some reason and we need to run e2fsck from a backup superblock.  The
 * important part is that the new block and inode counts are in the backup
 * superblocks, and the location of the new group metadata in the GDT backups.
 *
 * We do not need take the s_resize_lock for this, because these
 * blocks are not otherwise touched by the filesystem code when it is
 * mounted.  We don't need to worry about last changing from
 * sbi->s_groups_count, because the worst that can happen is that we
 * do not copy the full number of backups at this time.  The resize
 * which changed s_groups_count will backup again.
 */
static void update_backups(struct super_block *sb, sector_t blk_off, char *data,
			   int size, int meta_bg)
{
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	ext4_group_t last;
	const int bpg = EXT4_BLOCKS_PER_GROUP(sb);
	unsigned three = 1;
	unsigned five = 5;
	unsigned seven = 7;
	ext4_group_t group = 0;
	int rest = sb->s_blocksize - size;
	handle_t *handle;
	int err = 0, err2;

	handle = ext4_journal_start_sb(sb, EXT4_HT_RESIZE, EXT4_MAX_TRANS_DATA);
	if (IS_ERR(handle)) {
		group = 1;
		err = PTR_ERR(handle);
		goto exit_err;
	}

	if (meta_bg == 0) {
		group = ext4_list_backups(sb, &three, &five, &seven);
		last = sbi->s_groups_count;
	} else {
		group = ext4_get_group_number(sb, blk_off) + 1;
		last = (ext4_group_t)(group + EXT4_DESC_PER_BLOCK(sb) - 2);
	}

	while (group < sbi->s_groups_count) {
		struct buffer_head *bh;
		ext4_fsblk_t backup_block;

		/* Out of journal space, and can't get more - abort - so sad */
		err = ext4_resize_ensure_credits_batch(handle, 1);
		if (err < 0)
			break;

		if (meta_bg == 0)
			backup_block = ((ext4_fsblk_t)group) * bpg + blk_off;
		else
			backup_block = (ext4_group_first_block_no(sb, group) +
					ext4_bg_has_super(sb, group));

		bh = sb_getblk(sb, backup_block);
		if (unlikely(!bh)) {
			err = -ENOMEM;
			break;
		}
		ext4_debug("update metadata backup %llu(+%llu)\n",
			   backup_block, backup_block -
			   ext4_group_first_block_no(sb, group));
		BUFFER_TRACE(bh, "get_write_access");
		if ((err = ext4_journal_get_write_access(handle, sb, bh,
							 EXT4_JTR_NONE)))
			break;
		lock_buffer(bh);
		memcpy(bh->b_data, data, size);
		if (rest)
			memset(bh->b_data + size, 0, rest);
		set_buffer_uptodate(bh);
		unlock_buffer(bh);
		err = ext4_handle_dirty_metadata(handle, NULL, bh);
		if (unlikely(err))
			ext4_std_error(sb, err);
		brelse(bh);

		if (meta_bg == 0)
			group = ext4_list_backups(sb, &three, &five, &seven);
		else if (group == last)
			break;
		else
			group = last;
	}
	if ((err2 = ext4_journal_stop(handle)) && !err)
		err = err2;

	/*
	 * Ugh! Need to have e2fsck write the backup copies.  It is too
	 * late to revert the resize, we shouldn't fail just because of
	 * the backup copies (they are only needed in case of corruption).
	 *
	 * However, if we got here we have a journal problem too, so we
	 * can't really start a transaction to mark the superblock.
	 * Chicken out and just set the flag on the hope it will be written
	 * to disk, and if not - we will simply wait until next fsck.
	 */
exit_err:
	if (err) {
		ext4_warning(sb, "can't update backup for group %u (err %d), "
			     "forcing fsck on next reboot", group, err);
		sbi->s_mount_state &= ~EXT4_VALID_FS;
		sbi->s_es->s_state &= cpu_to_le16(~EXT4_VALID_FS);
		mark_buffer_dirty(sbi->s_sbh);
	}
}

/*
 * ext4_add_new_descs() adds @count group descriptor of groups
 * starting at @group
 *
 * @handle: journal handle
 * @sb: super block
 * @group: the group no. of the first group desc to be added
 * @resize_inode: the resize inode
 * @count: number of group descriptors to be added
 */
static int ext4_add_new_descs(handle_t *handle, struct super_block *sb,
			      ext4_group_t group, struct inode *resize_inode,
			      ext4_group_t count)
{
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	struct ext4_super_block *es = sbi->s_es;
	struct buffer_head *gdb_bh;
	int i, gdb_off, gdb_num, err = 0;
	int meta_bg;

	meta_bg = ext4_has_feature_meta_bg(sb);
	for (i = 0; i < count; i++, group++) {
		int reserved_gdb = ext4_bg_has_super(sb, group) ?
			le16_to_cpu(es->s_reserved_gdt_blocks) : 0;

		gdb_off = group % EXT4_DESC_PER_BLOCK(sb);
		gdb_num = group / EXT4_DESC_PER_BLOCK(sb);

		/*
		 * We will only either add reserved group blocks to a backup group
		 * or remove reserved blocks for the first group in a new group block.
		 * Doing both would be mean more complex code, and sane people don't
		 * use non-sparse filesystems anymore.  This is already checked above.
		 */
		if (gdb_off) {
			gdb_bh = sbi_array_rcu_deref(sbi, s_group_desc,
						     gdb_num);
			BUFFER_TRACE(gdb_bh, "get_write_access");
			err = ext4_journal_get_write_access(handle, sb, gdb_bh,
							    EXT4_JTR_NONE);

			if (!err && reserved_gdb && ext4_bg_num_gdb(sb, group))
				err = reserve_backup_gdb(handle, resize_inode, group);
		} else if (meta_bg != 0) {
			err = add_new_gdb_meta_bg(sb, handle, group);
		} else {
			err = add_new_gdb(handle, resize_inode, group);
		}
		if (err)
			break;
	}
	return err;
}

static struct buffer_head *ext4_get_bitmap(struct super_block *sb, __u64 block)
{
	struct buffer_head *bh = sb_getblk(sb, block);
	if (unlikely(!bh))
		return NULL;
	if (!bh_uptodate_or_lock(bh)) {
		if (ext4_read_bh(bh, 0, NULL) < 0) {
			brelse(bh);
			return NULL;
		}
	}

	return bh;
}

static int ext4_set_bitmap_checksums(struct super_block *sb,
				     ext4_group_t group,
				     struct ext4_group_desc *gdp,
				     struct ext4_new_group_data *group_data)
{
	struct buffer_head *bh;

	if (!ext4_has_metadata_csum(sb))
		return 0;

	bh = ext4_get_bitmap(sb, group_data->inode_bitmap);
	if (!bh)
		return -EIO;
	ext4_inode_bitmap_csum_set(sb, group, gdp, bh,
				   EXT4_INODES_PER_GROUP(sb) / 8);
	brelse(bh);

	bh = ext4_get_bitmap(sb, group_data->block_bitmap);
	if (!bh)
		return -EIO;
	ext4_block_bitmap_csum_set(sb, group, gdp, bh);
	brelse(bh);

	return 0;
}

/*
 * ext4_setup_new_descs() will set up the group descriptor descriptors of a flex bg
 */
static int ext4_setup_new_descs(handle_t *handle, struct super_block *sb,
				struct ext4_new_flex_group_data *flex_gd)
{
	struct ext4_new_group_data	*group_data = flex_gd->groups;
	struct ext4_group_desc		*gdp;
	struct ext4_sb_info		*sbi = EXT4_SB(sb);
	struct buffer_head		*gdb_bh;
	ext4_group_t			group;
	__u16				*bg_flags = flex_gd->bg_flags;
	int				i, gdb_off, gdb_num, err = 0;


	for (i = 0; i < flex_gd->count; i++, group_data++, bg_flags++) {
		group = group_data->group;

		gdb_off = group % EXT4_DESC_PER_BLOCK(sb);
		gdb_num = group / EXT4_DESC_PER_BLOCK(sb);

		/*
		 * get_write_access() has been called on gdb_bh by ext4_add_new_desc().
		 */
		gdb_bh = sbi_array_rcu_deref(sbi, s_group_desc, gdb_num);
		/* Update group descriptor block for new group */
		gdp = (struct ext4_group_desc *)(gdb_bh->b_data +
						 gdb_off * EXT4_DESC_SIZE(sb));

		memset(gdp, 0, EXT4_DESC_SIZE(sb));
		ext4_block_bitmap_set(sb, gdp, group_data->block_bitmap);
		ext4_inode_bitmap_set(sb, gdp, group_data->inode_bitmap);
		err = ext4_set_bitmap_checksums(sb, group, gdp, group_data);
		if (err) {
			ext4_std_error(sb, err);
			break;
		}

		ext4_inode_table_set(sb, gdp, group_data->inode_table);
		ext4_free_group_clusters_set(sb, gdp,
					     group_data->free_clusters_count);
		ext4_free_inodes_set(sb, gdp, EXT4_INODES_PER_GROUP(sb));
		if (ext4_has_group_desc_csum(sb))
			ext4_itable_unused_set(sb, gdp,
					       EXT4_INODES_PER_GROUP(sb));
		gdp->bg_flags = cpu_to_le16(*bg_flags);
		ext4_group_desc_csum_set(sb, group, gdp);

		err = ext4_handle_dirty_metadata(handle, NULL, gdb_bh);
		if (unlikely(err)) {
			ext4_std_error(sb, err);
			break;
		}

		/*
		 * We can allocate memory for mb_alloc based on the new group
		 * descriptor
		 */
		err = ext4_mb_add_groupinfo(sb, group, gdp);
		if (err)
			break;
	}
	return err;
}

static void ext4_add_overhead(struct super_block *sb,
                              const ext4_fsblk_t overhead)
{
       struct ext4_sb_info *sbi = EXT4_SB(sb);
       struct ext4_super_block *es = sbi->s_es;

       sbi->s_overhead += overhead;
       es->s_overhead_clusters = cpu_to_le32(sbi->s_overhead);
       smp_wmb();
}

/*
 * ext4_update_super() updates the super block so that the newly added
 * groups can be seen by the filesystem.
 *
 * @sb: super block
 * @flex_gd: new added groups
 */
static void ext4_update_super(struct super_block *sb,
			     struct ext4_new_flex_group_data *flex_gd)
{
	ext4_fsblk_t blocks_count = 0;
	ext4_fsblk_t free_blocks = 0;
	ext4_fsblk_t reserved_blocks = 0;
	struct ext4_new_group_data *group_data = flex_gd->groups;
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	struct ext4_super_block *es = sbi->s_es;
	int i;

	BUG_ON(flex_gd->count == 0 || group_data == NULL);
	/*
	 * Make the new blocks and inodes valid next.  We do this before
	 * increasing the group count so that once the group is enabled,
	 * all of its blocks and inodes are already valid.
	 *
	 * We always allocate group-by-group, then block-by-block or
	 * inode-by-inode within a group, so enabling these
	 * blocks/inodes before the group is live won't actually let us
	 * allocate the new space yet.
	 */
	for (i = 0; i < flex_gd->count; i++) {
		blocks_count += group_data[i].blocks_count;
		free_blocks += EXT4_C2B(sbi, group_data[i].free_clusters_count);
	}

	reserved_blocks = ext4_r_blocks_count(es) * 100;
	reserved_blocks = div64_u64(reserved_blocks, ext4_blocks_count(es));
	reserved_blocks *= blocks_count;
	do_div(reserved_blocks, 100);

	lock_buffer(sbi->s_sbh);
	ext4_blocks_count_set(es, ext4_blocks_count(es) + blocks_count);
	ext4_free_blocks_count_set(es, ext4_free_blocks_count(es) + free_blocks);
	le32_add_cpu(&es->s_inodes_count, EXT4_INODES_PER_GROUP(sb) *
		     flex_gd->count);
	le32_add_cpu(&es->s_free_inodes_count, EXT4_INODES_PER_GROUP(sb) *
		     flex_gd->count);

	ext4_debug("free blocks count %llu", ext4_free_blocks_count(es));
	/*
	 * We need to protect s_groups_count against other CPUs seeing
	 * inconsistent state in the superblock.
	 *
	 * The precise rules we use are:
	 *
	 * * Writers must perform a smp_wmb() after updating all
	 *   dependent data and before modifying the groups count
	 *
	 * * Readers must perform an smp_rmb() after reading the groups
	 *   count and before reading any dependent data.
	 *
	 * NB. These rules can be relaxed when checking the group count
	 * while freeing data, as we can only allocate from a block
	 * group after serialising against the group count, and we can
	 * only then free after serialising in turn against that
	 * allocation.
	 */
	smp_wmb();

	/* Update the global fs size fields */
	sbi->s_groups_count += flex_gd->count;
	sbi->s_blockfile_groups = min_t(ext4_group_t, sbi->s_groups_count,
			(EXT4_MAX_BLOCK_FILE_PHYS / EXT4_BLOCKS_PER_GROUP(sb)));

	/* Update the reserved block counts only once the new group is
	 * active. */
	ext4_r_blocks_count_set(es, ext4_r_blocks_count(es) +
				reserved_blocks);
	ext4_superblock_csum_set(sb);
	unlock_buffer(sbi->s_sbh);

	/* Update the free space counts */
	percpu_counter_add(&sbi->s_freeclusters_counter,
			   EXT4_NUM_B2C(sbi, free_blocks));
	percpu_counter_add(&sbi->s_freeinodes_counter,
			   EXT4_INODES_PER_GROUP(sb) * flex_gd->count);

	ext4_debug("free blocks count %llu",
		   percpu_counter_read(&sbi->s_freeclusters_counter));
	if (ext4_has_feature_flex_bg(sb) && sbi->s_log_groups_per_flex) {
		ext4_group_t flex_group;
		struct flex_groups *fg;

		flex_group = ext4_flex_group(sbi, group_data[0].group);
		fg = sbi_array_rcu_deref(sbi, s_flex_groups, flex_group);
		atomic64_add(EXT4_NUM_B2C(sbi, free_blocks),
			     &fg->free_clusters);
		atomic_add(EXT4_INODES_PER_GROUP(sb) * flex_gd->count,
			   &fg->free_inodes);
	}

	/*
	 * Update the fs overhead information.
	 *
	 * For bigalloc, if the superblock already has a properly calculated
	 * overhead, update it with a value based on numbers already computed
	 * above for the newly allocated capacity.
	 */
	if (ext4_has_feature_bigalloc(sb) && (sbi->s_overhead != 0))
		ext4_add_overhead(sb,
			EXT4_NUM_B2C(sbi, blocks_count - free_blocks));
	else
		ext4_calculate_overhead(sb);
	es->s_overhead_clusters = cpu_to_le32(sbi->s_overhead);

	if (test_opt(sb, DEBUG))
		printk(KERN_DEBUG "EXT4-fs: added group %u:"
		       "%llu blocks(%llu free %llu reserved)\n", flex_gd->count,
		       blocks_count, free_blocks, reserved_blocks);
}

/* Add a flex group to an fs. Ensure we handle all possible error conditions
 * _before_ we start modifying the filesystem, because we cannot abort the
 * transaction and not have it write the data to disk.
 */
static int ext4_flex_group_add(struct super_block *sb,
			       struct inode *resize_inode,
			       struct ext4_new_flex_group_data *flex_gd)
{
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	struct ext4_super_block *es = sbi->s_es;
	ext4_fsblk_t o_blocks_count;
	ext4_grpblk_t last;
	ext4_group_t group;
	handle_t *handle;
	unsigned reserved_gdb;
	int err = 0, err2 = 0, credit;

	BUG_ON(!flex_gd->count || !flex_gd->groups || !flex_gd->bg_flags);

	reserved_gdb = le16_to_cpu(es->s_reserved_gdt_blocks);
	o_blocks_count = ext4_blocks_count(es);
	ext4_get_group_no_and_offset(sb, o_blocks_count, &group, &last);
	BUG_ON(last);

	err = setup_new_flex_group_blocks(sb, flex_gd);
	if (err)
		goto exit;
	/*
	 * We will always be modifying at least the superblock and  GDT
	 * blocks.  If we are adding a group past the last current GDT block,
	 * we will also modify the inode and the dindirect block.  If we
	 * are adding a group with superblock/GDT backups  we will also
	 * modify each of the reserved GDT dindirect blocks.
	 */
	credit = 3;	/* sb, resize inode, resize inode dindirect */
	/* GDT blocks */
	credit += 1 + DIV_ROUND_UP(flex_gd->count, EXT4_DESC_PER_BLOCK(sb));
	credit += reserved_gdb;	/* Reserved GDT dindirect blocks */
	handle = ext4_journal_start_sb(sb, EXT4_HT_RESIZE, credit);
	if (IS_ERR(handle)) {
		err = PTR_ERR(handle);
		goto exit;
	}

	BUFFER_TRACE(sbi->s_sbh, "get_write_access");
	err = ext4_journal_get_write_access(handle, sb, sbi->s_sbh,
					    EXT4_JTR_NONE);
	if (err)
		goto exit_journal;

	group = flex_gd->groups[0].group;
	BUG_ON(group != sbi->s_groups_count);
	err = ext4_add_new_descs(handle, sb, group,
				resize_inode, flex_gd->count);
	if (err)
		goto exit_journal;

	err = ext4_setup_new_descs(handle, sb, flex_gd);
	if (err)
		goto exit_journal;

	ext4_update_super(sb, flex_gd);

	err = ext4_handle_dirty_metadata(handle, NULL, sbi->s_sbh);

exit_journal:
	err2 = ext4_journal_stop(handle);
	if (!err)
		err = err2;

	if (!err) {
		int gdb_num = group / EXT4_DESC_PER_BLOCK(sb);
		int gdb_num_end = ((group + flex_gd->count - 1) /
				   EXT4_DESC_PER_BLOCK(sb));
		int meta_bg = ext4_has_feature_meta_bg(sb);
		sector_t old_gdb = 0;

		update_backups(sb, sbi->s_sbh->b_blocknr, (char *)es,
			       sizeof(struct ext4_super_block), 0);
		for (; gdb_num <= gdb_num_end; gdb_num++) {
			struct buffer_head *gdb_bh;

			gdb_bh = sbi_array_rcu_deref(sbi, s_group_desc,
						     gdb_num);
			if (old_gdb == gdb_bh->b_blocknr)
				continue;
			update_backups(sb, gdb_bh->b_blocknr, gdb_bh->b_data,
				       gdb_bh->b_size, meta_bg);
			old_gdb = gdb_bh->b_blocknr;
		}
	}
exit:
	return err;
}

static int ext4_setup_next_flex_gd(struct super_block *sb,
				    struct ext4_new_flex_group_data *flex_gd,
				    ext4_fsblk_t n_blocks_count,
				    unsigned long flexbg_size)
{
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	struct ext4_super_block *es = sbi->s_es;
	struct ext4_new_group_data *group_data = flex_gd->groups;
	ext4_fsblk_t o_blocks_count;
	ext4_group_t n_group;
	ext4_group_t group;
	ext4_group_t last_group;
	ext4_grpblk_t last;
	ext4_grpblk_t clusters_per_group;
	unsigned long i;

	clusters_per_group = EXT4_CLUSTERS_PER_GROUP(sb);

	o_blocks_count = ext4_blocks_count(es);

	if (o_blocks_count == n_blocks_count)
		return 0;

	ext4_get_group_no_and_offset(sb, o_blocks_count, &group, &last);
	BUG_ON(last);
	ext4_get_group_no_and_offset(sb, n_blocks_count - 1, &n_group, &last);

	last_group = group | (flexbg_size - 1);
	if (last_group > n_group)
		last_group = n_group;

	flex_gd->count = last_group - group + 1;

	for (i = 0; i < flex_gd->count; i++) {
		int overhead;

		group_data[i].group = group + i;
		group_data[i].blocks_count = EXT4_BLOCKS_PER_GROUP(sb);
		overhead = ext4_group_overhead_blocks(sb, group + i);
		group_data[i].mdata_blocks = overhead;
		group_data[i].free_clusters_count = EXT4_CLUSTERS_PER_GROUP(sb);
		if (ext4_has_group_desc_csum(sb)) {
			flex_gd->bg_flags[i] = EXT4_BG_BLOCK_UNINIT |
					       EXT4_BG_INODE_UNINIT;
			if (!test_opt(sb, INIT_INODE_TABLE))
				flex_gd->bg_flags[i] |= EXT4_BG_INODE_ZEROED;
		} else
			flex_gd->bg_flags[i] = EXT4_BG_INODE_ZEROED;
	}

	if (last_group == n_group && ext4_has_group_desc_csum(sb))
		/* We need to initialize block bitmap of last group. */
		flex_gd->bg_flags[i - 1] &= ~EXT4_BG_BLOCK_UNINIT;

	if ((last_group == n_group) && (last != clusters_per_group - 1)) {
		group_data[i - 1].blocks_count = EXT4_C2B(sbi, last + 1);
		group_data[i - 1].free_clusters_count -= clusters_per_group -
						       last - 1;
	}

	return 1;
}

/* Add group descriptor data to an existing or new group descriptor block.
 * Ensure we handle all possible error conditions _before_ we start modifying
 * the filesystem, because we cannot abort the transaction and not have it
 * write the data to disk.
 *
 * If we are on a GDT block boundary, we need to get the reserved GDT block.
 * Otherwise, we may need to add backup GDT blocks for a sparse group.
 *
 * We only need to hold the superblock lock while we are actually adding
 * in the new group's counts to the superblock.  Prior to that we have
 * not really "added" the group at all.  We re-check that we are still
 * adding in the last group in case things have changed since verifying.
 */
int ext4_group_add(struct super_block *sb, struct ext4_new_group_data *input)
{
	struct ext4_new_flex_group_data flex_gd;
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	struct ext4_super_block *es = sbi->s_es;
	int reserved_gdb = ext4_bg_has_super(sb, input->group) ?
		le16_to_cpu(es->s_reserved_gdt_blocks) : 0;
	struct inode *inode = NULL;
	int gdb_off;
	int err;
	__u16 bg_flags = 0;

	gdb_off = input->group % EXT4_DESC_PER_BLOCK(sb);

	if (gdb_off == 0 && !ext4_has_feature_sparse_super(sb)) {
		ext4_warning(sb, "Can't resize non-sparse filesystem further");
		return -EPERM;
	}

	if (ext4_blocks_count(es) + input->blocks_count <
	    ext4_blocks_count(es)) {
		ext4_warning(sb, "blocks_count overflow");
		return -EINVAL;
	}

	if (le32_to_cpu(es->s_inodes_count) + EXT4_INODES_PER_GROUP(sb) <
	    le32_to_cpu(es->s_inodes_count)) {
		ext4_warning(sb, "inodes_count overflow");
		return -EINVAL;
	}

	if (reserved_gdb || gdb_off == 0) {
		if (!ext4_has_feature_resize_inode(sb) ||
		    !le16_to_cpu(es->s_reserved_gdt_blocks)) {
			ext4_warning(sb,
				     "No reserved GDT blocks, can't resize");
			return -EPERM;
		}
		inode = ext4_iget(sb, EXT4_RESIZE_INO, EXT4_IGET_SPECIAL);
		if (IS_ERR(inode)) {
			ext4_warning(sb, "Error opening resize inode");
			return PTR_ERR(inode);
		}
	}


	err = verify_group_input(sb, input);
	if (err)
		goto out;

	err = ext4_alloc_flex_bg_array(sb, input->group + 1);
	if (err)
		goto out;

	err = ext4_mb_alloc_groupinfo(sb, input->group + 1);
	if (err)
		goto out;

	flex_gd.count = 1;
	flex_gd.groups = input;
	flex_gd.bg_flags = &bg_flags;
	err = ext4_flex_group_add(sb, inode, &flex_gd);
out:
	iput(inode);
	return err;
} /* ext4_group_add */

/*
 * extend a group without checking assuming that checking has been done.
 */
static int ext4_group_extend_no_check(struct super_block *sb,
				      ext4_fsblk_t o_blocks_count, ext4_grpblk_t add)
{
	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
	handle_t *handle;
	int err = 0, err2;

	/* We will update the superblock, one block bitmap, and
	 * one group descriptor via ext4_group_add_blocks().
	 */
	handle = ext4_journal_start_sb(sb, EXT4_HT_RESIZE, 3);
	if (IS_ERR(handle)) {
		err = PTR_ERR(handle);
		ext4_warning(sb, "error %d on journal start", err);
		return err;
	}

	BUFFER_TRACE(EXT4_SB(sb)->s_sbh, "get_write_access");
	err = ext4_journal_get_write_access(handle, sb, EXT4_SB(sb)->s_sbh,
					    EXT4_JTR_NONE);
	if (err) {
		ext4_warning(sb, "error %d on journal write access", err);
		goto errout;
	}

	lock_buffer(EXT4_SB(sb)->s_sbh);
	ext4_blocks_count_set(es, o_blocks_count + add);
	ext4_free_blocks_count_set(es, ext4_free_blocks_count(es) + add);
	ext4_superblock_csum_set(sb);
	unlock_buffer(EXT4_SB(sb)->s_sbh);
	ext4_debug("freeing blocks %llu through %llu\n", o_blocks_count,
		   o_blocks_count + add);
	/* We add the blocks to the bitmap and set the group need init bit */
	err = ext4_group_add_blocks(handle, sb, o_blocks_count, add);
	if (err)
		goto errout;
	ext4_handle_dirty_metadata(handle, NULL, EXT4_SB(sb)->s_sbh);
	ext4_debug("freed blocks %llu through %llu\n", o_blocks_count,
		   o_blocks_count + add);
errout:
	err2 = ext4_journal_stop(handle);
	if (err2 && !err)
		err = err2;

	if (!err) {
		if (test_opt(sb, DEBUG))
			printk(KERN_DEBUG "EXT4-fs: extended group to %llu "
			       "blocks\n", ext4_blocks_count(es));
		update_backups(sb, EXT4_SB(sb)->s_sbh->b_blocknr,
			       (char *)es, sizeof(struct ext4_super_block), 0);
	}
	return err;
}

/*
 * Extend the filesystem to the new number of blocks specified.  This entry
 * point is only used to extend the current filesystem to the end of the last
 * existing group.  It can be accessed via ioctl, or by "remount,resize=<size>"
 * for emergencies (because it has no dependencies on reserved blocks).
 *
 * If we _really_ wanted, we could use default values to call ext4_group_add()
 * allow the "remount" trick to work for arbitrary resizing, assuming enough
 * GDT blocks are reserved to grow to the desired size.
 */
int ext4_group_extend(struct super_block *sb, struct ext4_super_block *es,
		      ext4_fsblk_t n_blocks_count)
{
	ext4_fsblk_t o_blocks_count;
	ext4_grpblk_t last;
	ext4_grpblk_t add;
	struct buffer_head *bh;
	int err;
	ext4_group_t group;

	o_blocks_count = ext4_blocks_count(es);

	if (test_opt(sb, DEBUG))
		ext4_msg(sb, KERN_DEBUG,
			 "extending last group from %llu to %llu blocks",
			 o_blocks_count, n_blocks_count);

	if (n_blocks_count == 0 || n_blocks_count == o_blocks_count)
		return 0;

	if (n_blocks_count > (sector_t)(~0ULL) >> (sb->s_blocksize_bits - 9)) {
		ext4_msg(sb, KERN_ERR,
			 "filesystem too large to resize to %llu blocks safely",
			 n_blocks_count);
		return -EINVAL;
	}

	if (n_blocks_count < o_blocks_count) {
		ext4_warning(sb, "can't shrink FS - resize aborted");
		return -EINVAL;
	}

	/* Handle the remaining blocks in the last group only. */
	ext4_get_group_no_and_offset(sb, o_blocks_count, &group, &last);

	if (last == 0) {
		ext4_warning(sb, "need to use ext2online to resize further");
		return -EPERM;
	}

	add = EXT4_BLOCKS_PER_GROUP(sb) - last;

	if (o_blocks_count + add < o_blocks_count) {
		ext4_warning(sb, "blocks_count overflow");
		return -EINVAL;
	}

	if (o_blocks_count + add > n_blocks_count)
		add = n_blocks_count - o_blocks_count;

	if (o_blocks_count + add < n_blocks_count)
		ext4_warning(sb, "will only finish group (%llu blocks, %u new)",
			     o_blocks_count + add, add);

	/* See if the device is actually as big as what was requested */
	bh = ext4_sb_bread(sb, o_blocks_count + add - 1, 0);
	if (IS_ERR(bh)) {
		ext4_warning(sb, "can't read last block, resize aborted");
		return -ENOSPC;
	}
	brelse(bh);

	err = ext4_group_extend_no_check(sb, o_blocks_count, add);
	return err;
} /* ext4_group_extend */


static int num_desc_blocks(struct super_block *sb, ext4_group_t groups)
{
	return (groups + EXT4_DESC_PER_BLOCK(sb) - 1) / EXT4_DESC_PER_BLOCK(sb);
}

/*
 * Release the resize inode and drop the resize_inode feature if there
 * are no more reserved gdt blocks, and then convert the file system
 * to enable meta_bg
 */
static int ext4_convert_meta_bg(struct super_block *sb, struct inode *inode)
{
	handle_t *handle;
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	struct ext4_super_block *es = sbi->s_es;
	struct ext4_inode_info *ei = EXT4_I(inode);
	ext4_fsblk_t nr;
	int i, ret, err = 0;
	int credits = 1;

	ext4_msg(sb, KERN_INFO, "Converting file system to meta_bg");
	if (inode) {
		if (es->s_reserved_gdt_blocks) {
			ext4_error(sb, "Unexpected non-zero "
				   "s_reserved_gdt_blocks");
			return -EPERM;
		}

		/* Do a quick sanity check of the resize inode */
		if (inode->i_blocks != 1 << (inode->i_blkbits -
					     (9 - sbi->s_cluster_bits)))
			goto invalid_resize_inode;
		for (i = 0; i < EXT4_N_BLOCKS; i++) {
			if (i == EXT4_DIND_BLOCK) {
				if (ei->i_data[i])
					continue;
				else
					goto invalid_resize_inode;
			}
			if (ei->i_data[i])
				goto invalid_resize_inode;
		}
		credits += 3;	/* block bitmap, bg descriptor, resize inode */
	}

	handle = ext4_journal_start_sb(sb, EXT4_HT_RESIZE, credits);
	if (IS_ERR(handle))
		return PTR_ERR(handle);

	BUFFER_TRACE(sbi->s_sbh, "get_write_access");
	err = ext4_journal_get_write_access(handle, sb, sbi->s_sbh,
					    EXT4_JTR_NONE);
	if (err)
		goto errout;

	lock_buffer(sbi->s_sbh);
	ext4_clear_feature_resize_inode(sb);
	ext4_set_feature_meta_bg(sb);
	sbi->s_es->s_first_meta_bg =
		cpu_to_le32(num_desc_blocks(sb, sbi->s_groups_count));
	ext4_superblock_csum_set(sb);
	unlock_buffer(sbi->s_sbh);

	err = ext4_handle_dirty_metadata(handle, NULL, sbi->s_sbh);
	if (err) {
		ext4_std_error(sb, err);
		goto errout;
	}

	if (inode) {
		nr = le32_to_cpu(ei->i_data[EXT4_DIND_BLOCK]);
		ext4_free_blocks(handle, inode, NULL, nr, 1,
				 EXT4_FREE_BLOCKS_METADATA |
				 EXT4_FREE_BLOCKS_FORGET);
		ei->i_data[EXT4_DIND_BLOCK] = 0;
		inode->i_blocks = 0;

		err = ext4_mark_inode_dirty(handle, inode);
		if (err)
			ext4_std_error(sb, err);
	}

errout:
	ret = ext4_journal_stop(handle);
	if (!err)
		err = ret;
	return ret;

invalid_resize_inode:
	ext4_error(sb, "corrupted/inconsistent resize inode");
	return -EINVAL;
}

/*
 * ext4_resize_fs() resizes a fs to new size specified by @n_blocks_count
 *
 * @sb: super block of the fs to be resized
 * @n_blocks_count: the number of blocks resides in the resized fs
 */
int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
{
	struct ext4_new_flex_group_data *flex_gd = NULL;
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	struct ext4_super_block *es = sbi->s_es;
	struct buffer_head *bh;
	struct inode *resize_inode = NULL;
	ext4_grpblk_t add, offset;
	unsigned long n_desc_blocks;
	unsigned long o_desc_blocks;
	ext4_group_t o_group;
	ext4_group_t n_group;
	ext4_fsblk_t o_blocks_count;
	ext4_fsblk_t n_blocks_count_retry = 0;
	unsigned long last_update_time = 0;
	int err = 0, flexbg_size = 1 << sbi->s_log_groups_per_flex;
	int meta_bg;

	/* See if the device is actually as big as what was requested */
	bh = ext4_sb_bread(sb, n_blocks_count - 1, 0);
	if (IS_ERR(bh)) {
		ext4_warning(sb, "can't read last block, resize aborted");
		return -ENOSPC;
	}
	brelse(bh);

	/*
	 * For bigalloc, trim the requested size to the nearest cluster
	 * boundary to avoid creating an unusable filesystem. We do this
	 * silently, instead of returning an error, to avoid breaking
	 * callers that blindly resize the filesystem to the full size of
	 * the underlying block device.
	 */
	if (ext4_has_feature_bigalloc(sb))
		n_blocks_count &= ~((1 << EXT4_CLUSTER_BITS(sb)) - 1);

retry:
	o_blocks_count = ext4_blocks_count(es);

	ext4_msg(sb, KERN_INFO, "resizing filesystem from %llu "
		 "to %llu blocks", o_blocks_count, n_blocks_count);

	if (n_blocks_count < o_blocks_count) {
		/* On-line shrinking not supported */
		ext4_warning(sb, "can't shrink FS - resize aborted");
		return -EINVAL;
	}

	if (n_blocks_count == o_blocks_count)
		/* Nothing need to do */
		return 0;

	n_group = ext4_get_group_number(sb, n_blocks_count - 1);
	if (n_group >= (0xFFFFFFFFUL / EXT4_INODES_PER_GROUP(sb))) {
		ext4_warning(sb, "resize would cause inodes_count overflow");
		return -EINVAL;
	}
	ext4_get_group_no_and_offset(sb, o_blocks_count - 1, &o_group, &offset);

	n_desc_blocks = num_desc_blocks(sb, n_group + 1);
	o_desc_blocks = num_desc_blocks(sb, sbi->s_groups_count);

	meta_bg = ext4_has_feature_meta_bg(sb);

	if (ext4_has_feature_resize_inode(sb)) {
		if (meta_bg) {
			ext4_error(sb, "resize_inode and meta_bg enabled "
				   "simultaneously");
			return -EINVAL;
		}
		if (n_desc_blocks > o_desc_blocks +
		    le16_to_cpu(es->s_reserved_gdt_blocks)) {
			n_blocks_count_retry = n_blocks_count;
			n_desc_blocks = o_desc_blocks +
				le16_to_cpu(es->s_reserved_gdt_blocks);
			n_group = n_desc_blocks * EXT4_DESC_PER_BLOCK(sb);
			n_blocks_count = (ext4_fsblk_t)n_group *
				EXT4_BLOCKS_PER_GROUP(sb) +
				le32_to_cpu(es->s_first_data_block);
			n_group--; /* set to last group number */
		}

		if (!resize_inode)
			resize_inode = ext4_iget(sb, EXT4_RESIZE_INO,
						 EXT4_IGET_SPECIAL);
		if (IS_ERR(resize_inode)) {
			ext4_warning(sb, "Error opening resize inode");
			return PTR_ERR(resize_inode);
		}
	}

	if ((!resize_inode && !meta_bg) || n_blocks_count == o_blocks_count) {
		err = ext4_convert_meta_bg(sb, resize_inode);
		if (err)
			goto out;
		if (resize_inode) {
			iput(resize_inode);
			resize_inode = NULL;
		}
		if (n_blocks_count_retry) {
			n_blocks_count = n_blocks_count_retry;
			n_blocks_count_retry = 0;
			goto retry;
		}
	}

	/*
	 * Make sure the last group has enough space so that it's
	 * guaranteed to have enough space for all metadata blocks
	 * that it might need to hold.  (We might not need to store
	 * the inode table blocks in the last block group, but there
	 * will be cases where this might be needed.)
	 */
	if ((ext4_group_first_block_no(sb, n_group) +
	     ext4_group_overhead_blocks(sb, n_group) + 2 +
	     sbi->s_itb_per_group + sbi->s_cluster_ratio) >= n_blocks_count) {
		n_blocks_count = ext4_group_first_block_no(sb, n_group);
		n_group--;
		n_blocks_count_retry = 0;
		if (resize_inode) {
			iput(resize_inode);
			resize_inode = NULL;
		}
		goto retry;
	}

	/* extend the last group */
	if (n_group == o_group)
		add = n_blocks_count - o_blocks_count;
	else
		add = EXT4_C2B(sbi, EXT4_CLUSTERS_PER_GROUP(sb) - (offset + 1));
	if (add > 0) {
		err = ext4_group_extend_no_check(sb, o_blocks_count, add);
		if (err)
			goto out;
	}

	if (ext4_blocks_count(es) == n_blocks_count && n_blocks_count_retry == 0)
		goto out;

	err = ext4_alloc_flex_bg_array(sb, n_group + 1);
	if (err)
		goto out;

	err = ext4_mb_alloc_groupinfo(sb, n_group + 1);
	if (err)
		goto out;

	flex_gd = alloc_flex_gd(flexbg_size);
	if (flex_gd == NULL) {
		err = -ENOMEM;
		goto out;
	}

	/* Add flex groups. Note that a regular group is a
	 * flex group with 1 group.
	 */
	while (ext4_setup_next_flex_gd(sb, flex_gd, n_blocks_count,
					      flexbg_size)) {
		if (time_is_before_jiffies(last_update_time + HZ * 10)) {
			if (last_update_time)
				ext4_msg(sb, KERN_INFO,
					 "resized to %llu blocks",
					 ext4_blocks_count(es));
			last_update_time = jiffies;
		}
		if (ext4_alloc_group_tables(sb, flex_gd, flexbg_size) != 0)
			break;
		err = ext4_flex_group_add(sb, resize_inode, flex_gd);
		if (unlikely(err))
			break;
	}

	if (!err && n_blocks_count_retry) {
		n_blocks_count = n_blocks_count_retry;
		n_blocks_count_retry = 0;
		free_flex_gd(flex_gd);
		flex_gd = NULL;
		if (resize_inode) {
			iput(resize_inode);
			resize_inode = NULL;
		}
		goto retry;
	}

out:
	if (flex_gd)
		free_flex_gd(flex_gd);
	if (resize_inode != NULL)
		iput(resize_inode);
	if (err)
		ext4_warning(sb, "error (%d) occurred during "
			     "file system resize", err);
	ext4_msg(sb, KERN_INFO, "resized filesystem to %llu",
		 ext4_blocks_count(es));
	return err;
}