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 static void count_bits(register const char *bmPart, register int size,
  21                        int *const tf)
  22 {
  23         char b;
  24         int tot = *tf;
  25
  26         if (size > QNX4_BLOCK_SIZE) {
  27                 size = QNX4_BLOCK_SIZE;
  28         }
  29         do {
  30                 b = *bmPart++;
  31                 if ((b & 1) == 0)
  32                         tot++;
  33                 if ((b & 2) == 0)
  34                         tot++;
  35                 if ((b & 4) == 0)
  36                         tot++;
  37                 if ((b & 8) == 0)
  38                         tot++;
  39                 if ((b & 16) == 0)
  40                         tot++;
  41                 if ((b & 32) == 0)
  42                         tot++;
  43                 if ((b & 64) == 0)
  44                         tot++;
  45                 if ((b & 128) == 0)
  46                         tot++;
  47                 size--;
  48         } while (size != 0);
  49         *tf = tot;
  50 }
  51
  52 unsigned long qnx4_count_free_blocks(struct super_block *sb)
  53 {
  54         int start = le32_to_cpu(qnx4_sb(sb)->BitMap->di_first_xtnt.xtnt_blk) - 1;
  55         int total = 0;
  56         int total_free = 0;
  57         int offset = 0;
  58         int size = le32_to_cpu(qnx4_sb(sb)->BitMap->di_size);
  59         struct buffer_head *bh;
  60
  61         while (total < size) {
  62                 if ((bh = sb_bread(sb, start + offset)) == NULL) {
  63                         printk(KERN_ERR "qnx4: I/O error in counting free blocks\n");
  64                         break;
  65                 }
  66                 count_bits(bh->b_data, size - total, &total_free);
  67                 brelse(bh);
  68                 total += QNX4_BLOCK_SIZE;
  69                 offset++;
  70         }
  71
  72         return total_free;
  73 }