arch/sparc/lib/bitext.c

   1 /*
   2  * bitext.c: kernel little helper (of bit shuffling variety).
   3  *
   4  * Copyright (C) 2002 Pete Zaitcev <zaitcev@yahoo.com>
   5  *
   6  * The algorithm to search a zero bit string is geared towards its application.
   7  * We expect a couple of fixed sizes of requests, so a rotating counter, reset
   8  * by align size, should provide fast enough search while maintaining low
   9  * fragmentation.
  10  */
  11
  12 #include <linux/smp_lock.h>
  13 #include <linux/string.h>
  14 #include <linux/bitops.h>
  15
  16 #include <asm/bitext.h>
  17
  18 /**
  19  * bit_map_string_get - find and set a bit string in bit map.
  20  * @t: the bit map.
  21  * @len: requested string length
  22  * @align: requested alignment
  23  *
  24  * Returns offset in the map or -1 if out of space.
  25  *
  26  * Not safe to call from an interrupt (uses spin_lock).
  27  */
  28 int bit_map_string_get(struct bit_map *t, int len, int align)
  29 {
  30         int offset, count;      /* siamese twins */
  31         int off_new;
  32         int align1;
  33         int i, color;
  34
  35         if (t->num_colors) {
  36                 /* align is overloaded to be the page color */
  37                 color = align;
  38                 align = t->num_colors;
  39         } else {
  40                 color = 0;
  41                 if (align == 0)
  42                         align = 1;
  43         }
  44         align1 = align - 1;
  45         if ((align & align1) != 0)
  46                 BUG();
  47         if (align < 0 || align >= t->size)
  48                 BUG();
  49         if (len <= 0 || len > t->size)
  50                 BUG();
  51         color &= align1;
  52
  53         spin_lock(&t->lock);
  54         if (len < t->last_size)
  55                 offset = t->first_free;
  56         else
  57                 offset = t->last_off & ~align1;
  58         count = 0;
  59         for (;;) {
  60                 off_new = find_next_zero_bit(t->map, t->size, offset);
  61                 off_new = ((off_new + align1) & ~align1) + color;
  62                 count += off_new - offset;
  63                 offset = off_new;
  64                 if (offset >= t->size)
  65                         offset = 0;
  66                 if (count + len > t->size) {
  67                         spin_unlock(&t->lock);
  68 /* P3 */ printk(KERN_ERR
  69   "bitmap out: size %d used %d off %d len %d align %d count %d\n",
  70   t->size, t->used, offset, len, align, count);
  71                         return -1;
  72                 }
  73
  74                 if (offset + len > t->size) {
  75                         count += t->size - offset;
  76                         offset = 0;
  77                         continue;
  78                 }
  79
  80                 i = 0;
  81                 while (test_bit(offset + i, t->map) == 0) {
  82                         i++;
  83                         if (i == len) {
  84                                 for (i = 0; i < len; i++)
  85                                         __set_bit(offset + i, t->map);
  86                                 if (offset == t->first_free)
  87                                         t->first_free = find_next_zero_bit
  88                                                         (t->map, t->size,
  89                                                          t->first_free + len);
  90                                 if ((t->last_off = offset + len) >= t->size)
  91                                         t->last_off = 0;
  92                                 t->used += len;
  93                                 t->last_size = len;
  94                                 spin_unlock(&t->lock);
  95                                 return offset;
  96                         }
  97                 }
  98                 count += i + 1;
  99                 if ((offset += i + 1) >= t->size)
 100                         offset = 0;
 101         }
 102 }
 103
 104 void bit_map_clear(struct bit_map *t, int offset, int len)
 105 {
 106         int i;
 107
 108         if (t->used < len)
 109                 BUG();          /* Much too late to do any good, but alas... */
 110         spin_lock(&t->lock);
 111         for (i = 0; i < len; i++) {
 112                 if (test_bit(offset + i, t->map) == 0)
 113                         BUG();
 114                 __clear_bit(offset + i, t->map);
 115         }
 116         if (offset < t->first_free)
 117                 t->first_free = offset;
 118         t->used -= len;
 119         spin_unlock(&t->lock);
 120 }
 121
 122 void bit_map_init(struct bit_map *t, unsigned long *map, int size)
 123 {
 124
 125         if ((size & 07) != 0)
 126                 BUG();
 127         memset(map, 0, size>>3);
 128
 129         memset(t, 0, sizeof *t);
 130         spin_lock_init(&t->lock);
 131         t->map = map;
 132         t->size = size;
 133 }