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 */ 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
