/* 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; }