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 */ 43 int 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
