minix/lib/libc/gen/fslib.c

   1 /* fslib.c - routines needed by fs and fs utilities */
   2
   3 #include <minix/config.h>       /* for unused stuff in <minix/type.h> :-( */
   4 #include <limits.h>
   5 #include <dirent.h>
   6 #include <assert.h>
   7 #include <stdlib.h>             /* for abort() */
   8 #include <sys/types.h>
   9 #include <minix/const.h>
  10 #include <minix/type.h>         /* for unshort :-( */
  11 #include <minix/minlib.h>
  12 #include <minix/ipc.h>
  13 #include "mfs/const.h"          /* depends of -I flag in Makefile */
  14 #include "mfs/type.h"           /* ditto */
  15 #include "mfs/inode.h"          /* ditto */
  16 #include "mfs/super.h"
  17 #include <minix/fslib.h>
  18
  19 /* The next routine is copied from fsck.c and mkfs.c...  (Re)define some
  20  * things for consistency.  Some things should be done better.
  21  */
  22
  23 /* Convert from bit count to a block count. The usual expression
  24  *
  25  *      (nr_bits + (1 << BITMAPSHIFT) - 1) >> BITMAPSHIFT
  26  *
  27  * doesn't work because of overflow.
  28  *
  29  * Other overflow bugs, such as the expression for N_ILIST overflowing when
  30  * s_inodes is just over V*_INODES_PER_BLOCK less than the maximum+1, are not
  31  * fixed yet, because that number of inodes is silly.
  32  */
  33 /* The above comment doesn't all apply now bit_t is long.  Overflow is now
  34  * unlikely, but negative bit counts are now possible (though unlikely)
  35  * and give silly results.
  36  */
  37 int bitmapsize(nr_bits, block_size)
  38 bit_t nr_bits;
  39 int block_size;
  40 {
  41   int nr_blocks;
  42
  43   nr_blocks = (int) (nr_bits / FS_BITS_PER_BLOCK(block_size));
  44   if (((bit_t) nr_blocks * FS_BITS_PER_BLOCK(block_size)) < nr_bits) ++nr_blocks;
  45   return(nr_blocks);
  46 }