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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 <common.h>
//#include <ext_common.h>
//#include <ext4fs.h>
#include <malloc.h>
#include <stddef.h>
#include <linux/stat.h>
#include <linux/time.h>
#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)
{
blk_t super_blk, old_desc_blk, new_desc_blk;
int j, old_desc_blocks, num_blocks;
num_blocks = ext2fs_super_and_bgd_loc(fs, group, &super_blk,
&old_desc_blk, &new_desc_blk, 0);//how many data blocks
if (fs->super->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG)
old_desc_blocks = fs->super->s_first_meta_bg;
else
old_desc_blocks =
fs->desc_blocks + fs->super->s_reserved_gdt_blocks;//how many block the group descriptions will take and reserve
if (super_blk || (group == 0))
ext2fs_mark_block_bitmap(bmap, super_blk);//mark the superblock in block bitmap
if (old_desc_blk) {
if (fs->super->s_reserved_gdt_blocks && fs->block_map == bmap)
fs->group_desc[group].bg_flags &= ~EXT2_BG_BLOCK_UNINIT;
for (j=0; j < old_desc_blocks; j++)
if (old_desc_blk + j < fs->super->s_blocks_count)
ext2fs_mark_block_bitmap(bmap,
old_desc_blk + j);//mar the group descriptions in the block bitmap
}
if (new_desc_blk)
ext2fs_mark_block_bitmap(bmap, new_desc_blk);
return num_blocks;//how many data blocks
}
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