fs/balloc.c

   1 /*
   2  *  thunix/fs/balloc.c
   3  *  it contains the blocks allocation and deallocation routines
   4  */
   5
   6 #include <fs_ext2.h>
   7
   8 #define in_range(b, first, len) ((b) >= (first) && (b) <= (first) + (len) - 1)
   9
  10 struct ext2_group_desc * ext2_get_group_desc(unsigned int block_group)
  11 {
  12         struct ext2_group_desc * desc;
  13         /*      struct ext2_sb_info *sbi = EXT2_SBI();
  14
  15
  16         if (block_group >= sbi->s_groups_count) {
  17                 ext2_error ("ext2_get_group_desc",
  18                             "block_group >= groups_count - "
  19                             "block_group = %d, groups_count = %lu",
  20                             block_group, sbi->s_groups_count);
  21
  22                 return NULL;
  23         }
  24         */
  25
  26         desc = (struct ext2_group_desc *) EXT2_GROUP_DESC_BUFFER;
  27
  28         return desc + block_group;
  29 }
  30
  31
  32
  33 /*
  34  * Read the bitmap for a given block_group, reading into the specified
  35  * slot in the superblock's bitmap cache.
  36  *
  37  */
  38 void * ext2_read_block_bitmap(unsigned int block_group)
  39 {
  40         struct ext2_group_desc * desc;
  41         void * bitmap = NULL;
  42
  43         desc = ext2_get_group_desc (block_group);
  44         if (!desc)
  45                 goto error_out;
  46         bitmap = (void *)(EXT2_BITMAP_BUFFER + (block_group << 1) * EXT2_BLOCK_SIZE);
  47         if (!bitmap)
  48                 ext2_error ("read_block_bitmap",
  49                             "Cannot read block bitmap - "
  50                             "block_group = %d, block_bitmap = %u",
  51                             block_group, desc->bg_block_bitmap);
  52 error_out:
  53         return bitmap;
  54 }
  55
  56
  57 /* free the goal block, clean it */
  58 void ext2_free_block(unsigned int block)
  59 {
  60         unsigned int block_group;
  61         unsigned int bit;
  62         struct ext2_group_desc *desc;
  63         struct ext2_sb_info * sbi = EXT2_SBI();
  64         void * bitmap;
  65
  66         block_group = ext2_get_group_num (block, BLOCK);
  67         bit = ext2_get_group_offset (block, BLOCK);
  68
  69         desc = ext2_get_group_desc (block_group);
  70         bitmap = ext2_read_block_bitmap (block_group);
  71
  72
  73         if ( !ext2_clear_bit(bitmap, bit) )
  74                 ext2_error("bit %d (%d) alread cleard", bit, block_group);
  75
  76         desc->bg_free_blocks_count ++;
  77         sbi->s_free_blocks_count ++;
  78 }
  79
  80 /*
  81  * get the specified goal block
  82  * if alread alloced find it by looking forward
  83  */
  84 int ext2_grab_block( char *bitmap, unsigned int goal)
  85 {
  86         if ( !ext2_test_bit(bitmap, goal) )
  87                 goto got_block;
  88
  89         /* else looking forward */
  90         goal = find_first_zero (bitmap, goal + 1, EXT2_BLOCKS_PER_GROUP);
  91  got_block:
  92         return goal;
  93 }
  94
  95 /* alloc a new block */
  96 int ext2_alloc_block ( unsigned int goal)
  97 {
  98         unsigned int block;
  99         unsigned int block_group;
 100         unsigned int bit;
 101         struct ext2_group_desc *desc;
 102         struct ext2_sb_info * sbi = EXT2_SBI();
 103         void *bitmap;
 104
 105         block_group = ext2_get_group_num (goal, BLOCK);
 106         bit = ext2_get_group_offset (goal, BLOCK);
 107
 108         bitmap = ext2_read_block_bitmap (block_group);
 109         block = ext2_grab_block (bitmap, bit);
 110
 111         if ( !block)
 112                 ext2_error ("no free blocks any more");
 113
 114         desc = ext2_get_group_desc (block_group);
 115         desc->bg_free_blocks_count --;
 116         sbi->s_free_blocks_count --;
 117         ext2_set_bit (bitmap, block);
 118
 119         return block;
 120 }
 121