alloc_sb.c revision e0ed7404719a9ddd2ba427a80db5365c8bad18c0 
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 <stdio.h>
14#include <string.h>
15#if HAVE_UNISTD_H
16#include <unistd.h>
17#endif
18#include <fcntl.h>
19#include <time.h>
20#if HAVE_SYS_STAT_H
21#include <sys/stat.h>
22#endif
23#if HAVE_SYS_TYPES_H
24#include <sys/types.h>
25#endif
26
27#include "ext2_fs.h"
28#include "ext2fs.h"
29
30/*
31 * This function reserves the superblock and block group descriptors
32 * for a given block group.  It currently returns the number of free
33 * blocks assuming that inode table and allocation bitmaps will be in
34 * the group.  This is not necessarily the case when the flex_bg
35 * feature is enabled, so callers should take care!  It was only
36 * really intended for use by mke2fs, and even there it's not that
37 * useful.  In the future, when we redo this function for 64-bit block
38 * numbers, we should probably return the number of blocks used by the
39 * super block and group descriptors instead.
40 *
41 * See also the comment for ext2fs_super_and_bgd_loc()
42 */
43int ext2fs_reserve_super_and_bgd(ext2_filsys fs,
44				 dgrp_t group,
45				 ext2fs_block_bitmap bmap)
46{
47	blk64_t	super_blk, old_desc_blk, new_desc_blk;
48	blk_t	used_blks;
49	int	old_desc_blocks, num_blocks;
50
51	ext2fs_super_and_bgd_loc2(fs, group, &super_blk,
52				  &old_desc_blk, &new_desc_blk, &used_blks);
53
54	if (fs->super->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG)
55		old_desc_blocks = fs->super->s_first_meta_bg;
56	else
57		old_desc_blocks =
58			fs->desc_blocks + fs->super->s_reserved_gdt_blocks;
59
60	if (super_blk || (group == 0))
61		ext2fs_mark_block_bitmap2(bmap, super_blk);
62	if ((group == 0) && (fs->blocksize == 1024) &&
63	    EXT2FS_CLUSTER_RATIO(fs) > 1)
64		ext2fs_mark_block_bitmap2(bmap, 0);
65
66	if (old_desc_blk) {
67		if (fs->super->s_reserved_gdt_blocks && fs->block_map == bmap)
68			ext2fs_bg_flags_clear(fs, group, EXT2_BG_BLOCK_UNINIT);
69		num_blocks = old_desc_blocks;
70		if (old_desc_blk + num_blocks >= ext2fs_blocks_count(fs->super))
71			num_blocks = ext2fs_blocks_count(fs->super) -
72				old_desc_blk;
73		ext2fs_mark_block_bitmap_range2(bmap, old_desc_blk, num_blocks);
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