| [821] | 1 | /*
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| 2 | * sparse.c --- find the groups in an ext2 filesystem with metadata backups
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| 3 | *
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| 4 | * Copyright (C) 1993, 1994, 1995, 1996 Theodore Ts'o.
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| 5 | * Copyright (C) 2002 Andreas Dilger.
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| 6 | *
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| 7 | * %Begin-Header%
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| 8 | * This file may be redistributed under the terms of the GNU Public
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| 9 | * License.
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| 10 | * %End-Header%
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| 11 | */
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| 12 |
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| 13 | #include <stdio.h>
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| 14 |
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| 15 | #include "ext2_fs.h"
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| 16 | #include "ext2fsP.h"
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| 17 |
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| 18 | static int test_root(int a, int b)
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| 19 | {
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| 20 | if (a == 0)
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| 21 | return 1;
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| 22 | while (1) {
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| 23 | if (a == 1)
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| 24 | return 1;
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| 25 | if (a % b)
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| 26 | return 0;
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| 27 | a = a / b;
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| 28 | }
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| 29 | }
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| 30 |
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| 31 | int ext2fs_bg_has_super(ext2_filsys fs, int group_block)
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| 32 | {
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| 33 | if (!(fs->super->s_feature_ro_compat &
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| 34 | EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER))
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| 35 | return 1;
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| 36 |
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| 37 | if (test_root(group_block, 3) || (test_root(group_block, 5)) ||
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| 38 | test_root(group_block, 7))
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| 39 | return 1;
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| 40 |
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| 41 | return 0;
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| 42 | }
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| 43 |
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| 44 | /*
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| 45 | * Iterate through the groups which hold BACKUP superblock/GDT copies in an
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| 46 | * ext3 filesystem. The counters should be initialized to 1, 5, and 7 before
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| 47 | * calling this for the first time. In a sparse filesystem it will be the
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| 48 | * sequence of powers of 3, 5, and 7: 1, 3, 5, 7, 9, 25, 27, 49, 81, ...
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| 49 | * For a non-sparse filesystem it will be every group: 1, 2, 3, 4, ...
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| 50 | */
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| 51 | unsigned int ext2fs_list_backups(ext2_filsys fs, unsigned int *three,
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| 52 | unsigned int *five, unsigned int *seven)
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| 53 | {
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| 54 | unsigned int *min = three;
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| 55 | int mult = 3;
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| 56 | unsigned int ret;
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| 57 |
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| 58 | if (!(fs->super->s_feature_ro_compat &
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| 59 | EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER)) {
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| 60 | ret = *min;
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| 61 | *min += 1;
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| 62 | return ret;
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| 63 | }
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| 64 |
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| 65 | if (*five < *min) {
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| 66 | min = five;
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| 67 | mult = 5;
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| 68 | }
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| 69 | if (*seven < *min) {
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| 70 | min = seven;
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| 71 | mult = 7;
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| 72 | }
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| 73 |
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| 74 | ret = *min;
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| 75 | *min *= mult;
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| 76 |
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| 77 | return ret;
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| 78 | }
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