minix/fs/mfs/stats.c

   1 #include "fs.h"
   2 #include <string.h>
   3 #include <minix/com.h>
   4 #include <assert.h>
   5 #include <minix/u64.h>
   6 #include "buf.h"
   7 #include "inode.h"
   8 #include "super.h"
   9 #include "const.h"
  10
  11 /*===========================================================================*
  12  *                              count_free_bits                              *
  13  *===========================================================================*/
  14 bit_t count_free_bits(sp, map)
  15 struct super_block *sp;         /* the filesystem to allocate from */
  16 int map;                        /* IMAP (inode map) or ZMAP (zone map) */
  17 {
  18 /* Allocate a bit from a bit map and return its bit number. */
  19   block_t start_block;          /* first bit block */
  20   block_t block;
  21   bit_t map_bits;               /* how many bits are there in the bit map? */
  22   short bit_blocks;             /* how many blocks are there in the bit map? */
  23   bit_t origin;                 /* number of bit to start searching at */
  24   unsigned word, bcount;
  25   struct buf *bp;
  26   bitchunk_t *wptr, *wlim, k;
  27   bit_t i, b;
  28   bit_t free_bits;
  29
  30   assert(sp != NULL);
  31
  32   if (map == IMAP) {
  33     start_block = START_BLOCK;
  34     map_bits = (bit_t) (sp->s_ninodes + 1);
  35     bit_blocks = sp->s_imap_blocks;
  36     origin = sp->s_isearch;
  37   } else {
  38     start_block = START_BLOCK + sp->s_imap_blocks;
  39     map_bits = (bit_t) (sp->s_zones - (sp->s_firstdatazone - 1));
  40     bit_blocks = sp->s_zmap_blocks;
  41     origin = sp->s_zsearch;
  42   }
  43
  44   /* Figure out where to start the bit search (depends on 'origin'). */
  45   if (origin >= map_bits) origin = 0;    /* for robustness */
  46   free_bits = 0;
  47
  48   /* Locate the starting place. */
  49   block = (block_t) (origin / FS_BITS_PER_BLOCK(sp->s_block_size));
  50   word = (origin % FS_BITS_PER_BLOCK(sp->s_block_size)) / FS_BITCHUNK_BITS;
  51
  52   /* Iterate over all blocks plus one, because we start in the middle. */
  53   bcount = bit_blocks;
  54   do {
  55     bp = get_block(sp->s_dev, start_block + block, NORMAL);
  56     assert(bp);
  57     wlim = &b_bitmap(bp)[FS_BITMAP_CHUNKS(sp->s_block_size)];
  58
  59     /* Iterate over the words in block. */
  60     for (wptr = &b_bitmap(bp)[word]; wptr < wlim; wptr++) {
  61
  62       /* Does this word contain a free bit? */
  63       if (*wptr == (bitchunk_t) ~0) continue;
  64
  65       k = (bitchunk_t) conv4(sp->s_native, (int) *wptr);
  66
  67       for (i = 0; i < 8*sizeof(k); ++i) {
  68         /* Bit number from the start of the bit map. */
  69         b = ((bit_t) block * FS_BITS_PER_BLOCK(sp->s_block_size))
  70             + (wptr - &b_bitmap(bp)[0]) * FS_BITCHUNK_BITS
  71             + i;
  72
  73         /* Don't count bits beyond the end of the map. */
  74         if (b >= map_bits) {
  75           break;
  76         }
  77         if ((k & (1 << i)) == 0) {
  78           free_bits++;
  79         }
  80       }
  81
  82       if (b >= map_bits) break;
  83     }
  84     put_block(bp);
  85     ++block;
  86     word = 0;
  87   } while (--bcount > 0);
  88   return free_bits;
  89 }