fs/ext4/bitmap.c

   1 /*
   2  *  linux/fs/ext4/bitmap.c
   3  *
   4  * Copyright (C) 1992, 1993, 1994, 1995
   5  * Remy Card (card@masi.ibp.fr)
   6  * Laboratoire MASI - Institut Blaise Pascal
   7  * Universite Pierre et Marie Curie (Paris VI)
   8  */
   9
  10 #include <linux/buffer_head.h>
  11 #include <linux/jbd2.h>
  12 #include "ext4.h"
  13
  14 #ifdef EXT4FS_DEBUG
  15
  16 static const int nibblemap[] = {4, 3, 3, 2, 3, 2, 2, 1, 3, 2, 2, 1, 2, 1, 1, 0};
  17
  18 unsigned long ext4_count_free(struct buffer_head *map, unsigned int numchars)
  19 {
  20         unsigned int i;
  21         unsigned long sum = 0;
  22
  23         if (!map)
  24                 return 0;
  25         for (i = 0; i < numchars; i++)
  26                 sum += nibblemap[map->b_data[i] & 0xf] +
  27                         nibblemap[(map->b_data[i] >> 4) & 0xf];
  28         return sum;
  29 }
  30
  31 #endif  /*  EXT4FS_DEBUG  */
  32