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80 lines
1.6 KiB
C
80 lines
1.6 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* sparse.c --- find the groups in an ext2 filesystem with metadata backups
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*
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* Copyright (C) 1993, 1994, 1995, 1996 Theodore Ts'o.
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* Copyright (C) 2002 Andreas Dilger.
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*
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* %Begin-Header%
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* This file may be redistributed under the terms of the GNU Public
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* License.
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* %End-Header%
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*/
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#include <stdio.h>
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#include "ext2_fs.h"
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#include "ext2fsP.h"
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static int test_root(int a, int b)
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{
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if (a == 0)
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return 1;
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while (1) {
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if (a == 1)
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return 1;
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if (a % b)
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return 0;
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a = a / b;
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}
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}
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int ext2fs_bg_has_super(ext2_filsys fs, int group_block)
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{
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if (!(fs->super->s_feature_ro_compat &
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EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER))
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return 1;
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if (test_root(group_block, 3) || (test_root(group_block, 5)) ||
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test_root(group_block, 7))
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return 1;
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return 0;
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}
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/*
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* Iterate through the groups which hold BACKUP superblock/GDT copies in an
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* ext3 filesystem. The counters should be initialized to 1, 5, and 7 before
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* calling this for the first time. In a sparse filesystem it will be the
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* sequence of powers of 3, 5, and 7: 1, 3, 5, 7, 9, 25, 27, 49, 81, ...
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* For a non-sparse filesystem it will be every group: 1, 2, 3, 4, ...
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*/
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unsigned int ext2fs_list_backups(ext2_filsys fs, unsigned int *three,
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unsigned int *five, unsigned int *seven)
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{
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unsigned int *min = three;
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int mult = 3;
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unsigned int ret;
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if (!(fs->super->s_feature_ro_compat &
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EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER)) {
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ret = *min;
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*min += 1;
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return ret;
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}
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if (*five < *min) {
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min = five;
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mult = 5;
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}
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if (*seven < *min) {
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min = seven;
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mult = 7;
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}
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ret = *min;
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*min *= mult;
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return ret;
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}
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