blob: b3d3071e985e405bcb9facb5c7d2d99d0d082e05
1 | /* vi: set sw=4 ts=4: */ |
2 | /* |
3 | * sparse.c --- find the groups in an ext2 filesystem with metadata backups |
4 | * |
5 | * Copyright (C) 1993, 1994, 1995, 1996 Theodore Ts'o. |
6 | * Copyright (C) 2002 Andreas Dilger. |
7 | * |
8 | * %Begin-Header% |
9 | * This file may be redistributed under the terms of the GNU Public |
10 | * License. |
11 | * %End-Header% |
12 | */ |
13 | |
14 | #include <stdio.h> |
15 | |
16 | #include "ext2_fs.h" |
17 | #include "ext2fsP.h" |
18 | |
19 | static int test_root(int a, int b) |
20 | { |
21 | if (a == 0) |
22 | return 1; |
23 | while (1) { |
24 | if (a == 1) |
25 | return 1; |
26 | if (a % b) |
27 | return 0; |
28 | a = a / b; |
29 | } |
30 | } |
31 | |
32 | int ext2fs_bg_has_super(ext2_filsys fs, int group_block) |
33 | { |
34 | if (!(fs->super->s_feature_ro_compat & |
35 | EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER)) |
36 | return 1; |
37 | |
38 | if (test_root(group_block, 3) || (test_root(group_block, 5)) || |
39 | test_root(group_block, 7)) |
40 | return 1; |
41 | |
42 | return 0; |
43 | } |
44 | |
45 | /* |
46 | * Iterate through the groups which hold BACKUP superblock/GDT copies in an |
47 | * ext3 filesystem. The counters should be initialized to 1, 5, and 7 before |
48 | * calling this for the first time. In a sparse filesystem it will be the |
49 | * sequence of powers of 3, 5, and 7: 1, 3, 5, 7, 9, 25, 27, 49, 81, ... |
50 | * For a non-sparse filesystem it will be every group: 1, 2, 3, 4, ... |
51 | */ |
52 | unsigned int ext2fs_list_backups(ext2_filsys fs, unsigned int *three, |
53 | unsigned int *five, unsigned int *seven) |
54 | { |
55 | unsigned int *min = three; |
56 | int mult = 3; |
57 | unsigned int ret; |
58 | |
59 | if (!(fs->super->s_feature_ro_compat & |
60 | EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER)) { |
61 | ret = *min; |
62 | *min += 1; |
63 | return ret; |
64 | } |
65 | |
66 | if (*five < *min) { |
67 | min = five; |
68 | mult = 5; |
69 | } |
70 | if (*seven < *min) { |
71 | min = seven; |
72 | mult = 7; |
73 | } |
74 | |
75 | ret = *min; |
76 | *min *= mult; |
77 | |
78 | return ret; |
79 | } |
80 |