fs/qnx4/bitmap.c

   1 /*
   2  * QNX4 file system, Linux implementation.
   3  *
   4  * Version : 0.2.1
   5  *
   6  * Using parts of the xiafs filesystem.
   7  *
   8  * History :
   9  *
  10  * 28-05-1998 by Richard Frowijn : first release.
  11  * 20-06-1998 by Frank Denis : basic optimisations.
  12  * 25-06-1998 by Frank Denis : qnx4_is_free, qnx4_set_bitmap, qnx4_bmap .
  13  * 28-06-1998 by Frank Denis : qnx4_free_inode (to be fixed) .
  14  */
  15
  16 #include <linux/buffer_head.h>
  17 #include <linux/bitops.h>
  18 #include "qnx4.h"
  19
  20 #if 0
  21 int qnx4_new_block(struct super_block *sb)
  22 {
  23         return 0;
  24 }
  25 #endif  /*  0  */
  26
  27 static void count_bits(register const char *bmPart, register int size,
  28                        int *const tf)
  29 {
  30         char b;
  31         int tot = *tf;
  32
  33         if (size > QNX4_BLOCK_SIZE) {
  34                 size = QNX4_BLOCK_SIZE;
  35         }
  36         do {
  37                 b = *bmPart++;
  38                 if ((b & 1) == 0)
  39                         tot++;
  40                 if ((b & 2) == 0)
  41                         tot++;
  42                 if ((b & 4) == 0)
  43                         tot++;
  44                 if ((b & 8) == 0)
  45                         tot++;
  46                 if ((b & 16) == 0)
  47                         tot++;
  48                 if ((b & 32) == 0)
  49                         tot++;
  50                 if ((b & 64) == 0)
  51                         tot++;
  52                 if ((b & 128) == 0)
  53                         tot++;
  54                 size--;
  55         } while (size != 0);
  56         *tf = tot;
  57 }
  58
  59 unsigned long qnx4_count_free_blocks(struct super_block *sb)
  60 {
  61         int start = le32_to_cpu(qnx4_sb(sb)->BitMap->di_first_xtnt.xtnt_blk) - 1;
  62         int total = 0;
  63         int total_free = 0;
  64         int offset = 0;
  65         int size = le32_to_cpu(qnx4_sb(sb)->BitMap->di_size);
  66         struct buffer_head *bh;
  67
  68         while (total < size) {
  69                 if ((bh = sb_bread(sb, start + offset)) == NULL) {
  70                         printk("qnx4: I/O error in counting free blocks\n");
  71                         break;
  72                 }
  73                 count_bits(bh->b_data, size - total, &total_free);
  74                 brelse(bh);
  75                 total += QNX4_BLOCK_SIZE;
  76                 offset++;
  77         }
  78
  79         return total_free;
  80 }