| Denis Vlasenko | c4f623e | 2006-12-26 01:30:59 +0000 | [diff] [blame] | 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 | } |