alloc_sb.c revision d1154eb460efe588eaed3d439c1caaca149fa362 
1/*
2 * alloc_sb.c --- Allocate the superblock and block group descriptors for a
3 * newly initialized filesystem.  Used by mke2fs when initializing a filesystem
4 *
5 * Copyright (C) 1994, 1995, 1996, 2003 Theodore Ts'o.
6 *
7 * %Begin-Header%
8 * This file may be redistributed under the terms of the GNU Library
9 * General Public License, version 2.
10 * %End-Header%
11 */
12
13#include "config.h"
14#include <stdio.h>
15#include <string.h>
16#if HAVE_UNISTD_H
17#include <unistd.h>
18#endif
19#include <fcntl.h>
20#include <time.h>
21#if HAVE_SYS_STAT_H
22#include <sys/stat.h>
23#endif
24#if HAVE_SYS_TYPES_H
25#include <sys/types.h>
26#endif
27
28#include "ext2_fs.h"
29#include "ext2fs.h"
30
31/*
32 * This function reserves the superblock and block group descriptors
33 * for a given block group.  It currently returns the number of free
34 * blocks assuming that inode table and allocation bitmaps will be in
35 * the group.  This is not necessarily the case when the flex_bg
36 * feature is enabled, so callers should take care!  It was only
37 * really intended for use by mke2fs, and even there it's not that
38 * useful.  In the future, when we redo this function for 64-bit block
39 * numbers, we should probably return the number of blocks used by the
40 * super block and group descriptors instead.
41 *
42 * See also the comment for ext2fs_super_and_bgd_loc()
43 */
44int ext2fs_reserve_super_and_bgd(ext2_filsys fs,
45				 dgrp_t group,
46				 ext2fs_block_bitmap bmap)
47{
48	blk64_t	super_blk, old_desc_blk, new_desc_blk;
49	blk_t	used_blks;
50	int	j, old_desc_blocks, num_blocks;
51
52	ext2fs_super_and_bgd_loc2(fs, group, &super_blk,
53				  &old_desc_blk, &new_desc_blk, &used_blks);
54
55	if (fs->super->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG)
56		old_desc_blocks = fs->super->s_first_meta_bg;
57	else
58		old_desc_blocks =
59			fs->desc_blocks + fs->super->s_reserved_gdt_blocks;
60
61	if (super_blk || (group == 0))
62		ext2fs_mark_block_bitmap2(bmap, super_blk);
63	if ((group == 0) && (fs->blocksize == 1024) &&
64	    EXT2FS_CLUSTER_RATIO(fs) > 1)
65		ext2fs_mark_block_bitmap2(bmap, 0);
66
67	if (old_desc_blk) {
68		if (fs->super->s_reserved_gdt_blocks && fs->block_map == bmap)
69			ext2fs_bg_flags_clear(fs, group, EXT2_BG_BLOCK_UNINIT);
70		for (j=0; j < old_desc_blocks; j++)
71			if (old_desc_blk + j < ext2fs_blocks_count(fs->super))
72				ext2fs_mark_block_bitmap2(bmap,
73							 old_desc_blk + j);
74	}
75	if (new_desc_blk)
76		ext2fs_mark_block_bitmap2(bmap, new_desc_blk);
77
78	num_blocks = ext2fs_group_blocks_count(fs, group);
79	num_blocks -= 2 + fs->inode_blocks_per_group + used_blks;
80
81	return num_blocks  ;
82}
83