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 <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         blk_t   super_blk, old_desc_blk, new_desc_blk;
  48         int     j, old_desc_blocks, num_blocks;
  49
  50         num_blocks = ext2fs_super_and_bgd_loc(fs, group, &super_blk,
  51                                               &old_desc_blk, &new_desc_blk, 0);
  52
  53         if (fs->super->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG)
  54                 old_desc_blocks = fs->super->s_first_meta_bg;
  55         else
  56                 old_desc_blocks =
  57                         fs->desc_blocks + fs->super->s_reserved_gdt_blocks;
  58
  59         if (super_blk || (group == 0))
  60                 ext2fs_mark_block_bitmap(bmap, super_blk);
  61
  62         if (old_desc_blk) {
  63                 if (fs->super->s_reserved_gdt_blocks && fs->block_map == bmap)
  64                         fs->group_desc[group].bg_flags &= ~EXT2_BG_BLOCK_UNINIT;
  65                 for (j=0; j < old_desc_blocks; j++)
  66                         if (old_desc_blk + j < fs->super->s_blocks_count)
  67                                 ext2fs_mark_block_bitmap(bmap,
  68                                                          old_desc_blk + j);
  69         }
  70         if (new_desc_blk)
  71                 ext2fs_mark_block_bitmap(bmap, new_desc_blk);
  72
  73         return num_blocks;
  74 }