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