1 /*
2 * sparse.c --- find the groups in an ext2 filesystem with metadata backups
3 *
4 * Copyright (C) 1993, 1994, 1995, 1996 Theodore Ts'o.
5 * Copyright (C) 2002 Andreas Dilger.
6 *
7 * %Begin-Header%
8 * This file may be redistributed under the terms of the GNU Public
9 * License.
10 * %End-Header%
11 */
12
13 #include <stdio.h>
14
15 #include "ext2_fs.h"
16 #include "ext2fsP.h"
17
test_root(int a,int b)18 static int test_root(int a, int b)
19 {
20 if (a == 0)
21 return 1;
22 while (1) {
23 if (a == 1)
24 return 1;
25 if (a % b)
26 return 0;
27 a = a / b;
28 }
29 }
30
ext2fs_bg_has_super(ext2_filsys fs,int group_block)31 int ext2fs_bg_has_super(ext2_filsys fs, int group_block)
32 {
33 if (!(fs->super->s_feature_ro_compat &
34 EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER))
35 return 1;
36
37 if (test_root(group_block, 3) || (test_root(group_block, 5)) ||
38 test_root(group_block, 7))
39 return 1;
40
41 return 0;
42 }
43
44 /*
45 * Iterate through the groups which hold BACKUP superblock/GDT copies in an
46 * ext3 filesystem. The counters should be initialized to 1, 5, and 7 before
47 * calling this for the first time. In a sparse filesystem it will be the
48 * sequence of powers of 3, 5, and 7: 1, 3, 5, 7, 9, 25, 27, 49, 81, ...
49 * For a non-sparse filesystem it will be every group: 1, 2, 3, 4, ...
50 */
ext2fs_list_backups(ext2_filsys fs,unsigned int * three,unsigned int * five,unsigned int * seven)51 unsigned int ext2fs_list_backups(ext2_filsys fs, unsigned int *three,
52 unsigned int *five, unsigned int *seven)
53 {
54 unsigned int *min = three;
55 int mult = 3;
56 unsigned int ret;
57
58 if (!(fs->super->s_feature_ro_compat &
59 EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER)) {
60 ret = *min;
61 *min += 1;
62 return ret;
63 }
64
65 if (*five < *min) {
66 min = five;
67 mult = 5;
68 }
69 if (*seven < *min) {
70 min = seven;
71 mult = 7;
72 }
73
74 ret = *min;
75 *min *= mult;
76
77 return ret;
78 }
79