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 */
ext2fs_reserve_super_and_bgd(ext2_filsys fs,dgrp_t group,ext2fs_block_bitmap bmap)44 int 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 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 (ext2fs_has_feature_meta_bg(fs->super))
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 num_blocks = old_desc_blocks;
69 if (old_desc_blk + num_blocks >= ext2fs_blocks_count(fs->super))
70 num_blocks = ext2fs_blocks_count(fs->super) -
71 old_desc_blk;
72 ext2fs_mark_block_bitmap_range2(bmap, old_desc_blk, num_blocks);
73 }
74 if (new_desc_blk)
75 ext2fs_mark_block_bitmap2(bmap, new_desc_blk);
76
77 num_blocks = ext2fs_group_blocks_count(fs, group);
78 num_blocks -= 2 + fs->inode_blocks_per_group + used_blks;
79
80 return num_blocks ;
81 }
82