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/string.h>
  13 #include <linux/bitmap.h>
  14
  15 #include <asm/bitext.h>
  16
  17 /**
  18  * bit_map_string_get - find and set a bit string in bit map.
  19  * @t: the bit map.
  20  * @len: requested string length
  21  * @align: requested alignment
  22  *
  23  * Returns offset in the map or -1 if out of space.
  24  *
  25  * Not safe to call from an interrupt (uses spin_lock).
  26  */
  27 int bit_map_string_get(struct bit_map *t, int len, int align)
  28 {
  29         int offset, count;      /* siamese twins */
  30         int off_new;
  31         int align1;
  32         int i, color;
  33
  34         if (t->num_colors) {
  35                 /* align is overloaded to be the page color */
  36                 color = align;
  37                 align = t->num_colors;
  38         } else {
  39                 color = 0;
  40                 if (align == 0)
  41                         align = 1;
  42         }
  43         align1 = align - 1;
  44         if ((align & align1) != 0)
  45                 BUG();
  46         if (align < 0 || align >= t->size)
  47                 BUG();
  48         if (len <= 0 || len > t->size)
  49                 BUG();
  50         color &= align1;
  51
  52         spin_lock(&t->lock);
  53         if (len < t->last_size)
  54                 offset = t->first_free;
  55         else
  56                 offset = t->last_off & ~align1;
  57         count = 0;
  58         for (;;) {
  59                 off_new = find_next_zero_bit(t->map, t->size, offset);
  60                 off_new = ((off_new + align1) & ~align1) + color;
  61                 count += off_new - offset;
  62                 offset = off_new;
  63                 if (offset >= t->size)
  64                         offset = 0;
  65                 if (count + len > t->size) {
  66                         spin_unlock(&t->lock);
  67 /* P3 */ printk(KERN_ERR
  68   "bitmap out: size %d used %d off %d len %d align %d count %d\n",
  69   t->size, t->used, offset, len, align, count);
  70                         return -1;
  71                 }
  72
  73                 if (offset + len > t->size) {
  74                         count += t->size - offset;
  75                         offset = 0;
  76                         continue;
  77                 }
  78
  79                 i = 0;
  80                 while (test_bit(offset + i, t->map) == 0) {
  81                         i++;
  82                         if (i == len) {
  83                                 bitmap_set(t->map, offset, len);
  84                                 if (offset == t->first_free)
  85                                         t->first_free = find_next_zero_bit
  86                                                         (t->map, t->size,
  87                                                          t->first_free + len);
  88                                 if ((t->last_off = offset + len) >= t->size)
  89                                         t->last_off = 0;
  90                                 t->used += len;
  91                                 t->last_size = len;
  92                                 spin_unlock(&t->lock);
  93                                 return offset;
  94                         }
  95                 }
  96                 count += i + 1;
  97                 if ((offset += i + 1) >= t->size)
  98                         offset = 0;
  99         }
 100 }
 101
 102 void bit_map_clear(struct bit_map *t, int offset, int len)
 103 {
 104         int i;
 105
 106         if (t->used < len)
 107                 BUG();          /* Much too late to do any good, but alas... */
 108         spin_lock(&t->lock);
 109         for (i = 0; i < len; i++) {
 110                 if (test_bit(offset + i, t->map) == 0)
 111                         BUG();
 112                 __clear_bit(offset + i, t->map);
 113         }
 114         if (offset < t->first_free)
 115                 t->first_free = offset;
 116         t->used -= len;
 117         spin_unlock(&t->lock);
 118 }
 119
 120 void bit_map_init(struct bit_map *t, unsigned long *map, int size)
 121 {
 122         bitmap_zero(map, size);
 123         memset(t, 0, sizeof *t);
 124         spin_lock_init(&t->lock);
 125         t->map = map;
 126         t->size = size;
 127 }