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/*
* alloc_sb.c --- Allocate the superblock and block group descriptors for a
* newly initialized filesystem. Used by mke2fs when initializing a filesystem
*
* Copyright (C) 1994, 1995, 1996, 2003 Theodore Ts'o.
*
* %Begin-Header%
* This file may be redistributed under the terms of the GNU Library
* General Public License, version 2.
* %End-Header%
*/
#include "config.h"
#include <stdio.h>
#include <string.h>
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <fcntl.h>
#include <time.h>
#if HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif
#if HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#include "ext2_fs.h"
#include "ext2fs.h"
/*
* This function reserves the superblock and block group descriptors
* for a given block group. It currently returns the number of free
* blocks assuming that inode table and allocation bitmaps will be in
* the group. This is not necessarily the case when the flex_bg
* feature is enabled, so callers should take care! It was only
* really intended for use by mke2fs, and even there it's not that
* useful. In the future, when we redo this function for 64-bit block
* numbers, we should probably return the number of blocks used by the
* super block and group descriptors instead.
*
* See also the comment for ext2fs_super_and_bgd_loc()
*/
int ext2fs_reserve_super_and_bgd(ext2_filsys fs,
dgrp_t group,
ext2fs_block_bitmap bmap)
{
blk64_t super_blk, old_desc_blk, new_desc_blk;
blk_t used_blks;
int old_desc_blocks, num_blocks;
ext2fs_super_and_bgd_loc2(fs, group, &super_blk,
&old_desc_blk, &new_desc_blk, &used_blks);
if (ext2fs_has_feature_meta_bg(fs->super))
old_desc_blocks = fs->super->s_first_meta_bg;
else
old_desc_blocks =
fs->desc_blocks + fs->super->s_reserved_gdt_blocks;
if (super_blk || (group == 0))
ext2fs_mark_block_bitmap2(bmap, super_blk);
if ((group == 0) && (fs->blocksize == 1024) &&
EXT2FS_CLUSTER_RATIO(fs) > 1)
ext2fs_mark_block_bitmap2(bmap, 0);
if (old_desc_blk) {
num_blocks = old_desc_blocks;
if (old_desc_blk + num_blocks >= ext2fs_blocks_count(fs->super))
num_blocks = ext2fs_blocks_count(fs->super) -
old_desc_blk;
ext2fs_mark_block_bitmap_range2(bmap, old_desc_blk, num_blocks);
}
if (new_desc_blk)
ext2fs_mark_block_bitmap2(bmap, new_desc_blk);
num_blocks = ext2fs_group_blocks_count(fs, group);
num_blocks -= 2 + fs->inode_blocks_per_group + used_blks;
return num_blocks ;
}
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