lib/ext2fs/alloc_sb.c

   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 }