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         blk64_t super_blk, old_desc_blk, new_desc_blk;
  48         blk_t   used_blks;
  49         int     j, 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                 for (j=0; j < old_desc_blocks; j++)
  70                         if (old_desc_blk + j < ext2fs_blocks_count(fs->super))
  71                                 ext2fs_mark_block_bitmap2(bmap,
  72                                                          old_desc_blk + j);
  73         }
  74         if (new_desc_blk)
  75                 ext2fs_mark_block_bitmap2(bmap, new_desc_blk);
  76
  77         if (group == fs->group_desc_count-1) {
  78                 num_blocks = (ext2fs_blocks_count(fs->super) -
  79                              fs->super->s_first_data_block) %
  80                         fs->super->s_blocks_per_group;
  81                 if (!num_blocks)
  82                         num_blocks = fs->super->s_blocks_per_group;
  83         } else
  84                 num_blocks = fs->super->s_blocks_per_group;
  85
  86         num_blocks -= 2 + fs->inode_blocks_per_group + used_blks;
  87
  88         return num_blocks  ;
  89 }