128 lines
2.8 KiB
C
128 lines
2.8 KiB
C
|
/*
|
||
|
|
* bitext.c: kernel little helper (of bit shuffling variety).
|
||
|
|
*
|
||
|
|
* Copyright (C) 2002 Pete Zaitcev <zaitcev@yahoo.com>
|
||
|
|
*
|
||
|
|
* The algorithm to search a zero bit string is geared towards its application.
|
||
|
|
* We expect a couple of fixed sizes of requests, so a rotating counter, reset
|
||
|
|
* by align size, should provide fast enough search while maintaining low
|
||
|
|
* fragmentation.
|
||
|
|
*/
|
||
|
|
|
||
|
|
#include <linux/string.h>
|
||
|
|
#include <linux/bitmap.h>
|
||
|
|
|
||
|
|
#include <asm/bitext.h>
|
||
|
|
|
||
|
|
/**
|
||
|
|
* bit_map_string_get - find and set a bit string in bit map.
|
||
|
|
* @t: the bit map.
|
||
|
|
* @len: requested string length
|
||
|
|
* @align: requested alignment
|
||
|
|
*
|
||
|
|
* Returns offset in the map or -1 if out of space.
|
||
|
|
*
|
||
|
|
* Not safe to call from an interrupt (uses spin_lock).
|
||
|
|
*/
|
||
|
|
int bit_map_string_get(struct bit_map *t, int len, int align)
|
||
|
|
{
|
||
|
|
int offset, count; /* siamese twins */
|
||
|
|
int off_new;
|
||
|
|
int align1;
|
||
|
|
int i, color;
|
||
|
|
|
||
|
|
if (t->num_colors) {
|
||
|
|
/* align is overloaded to be the page color */
|
||
|
|
color = align;
|
||
|
|
align = t->num_colors;
|
||
|
|
} else {
|
||
|
|
color = 0;
|
||
|
|
if (align == 0)
|
||
|
|
align = 1;
|
||
|
|
}
|
||
|
|
align1 = align - 1;
|
||
|
|
if ((align & align1) != 0)
|
||
|
|
BUG();
|
||
|
|
if (align < 0 || align >= t->size)
|
||
|
|
BUG();
|
||
|
|
if (len <= 0 || len > t->size)
|
||
|
|
BUG();
|
||
|
|
color &= align1;
|
||
|
|
|
||
|
|
spin_lock(&t->lock);
|
||
|
|
if (len < t->last_size)
|
||
|
|
offset = t->first_free;
|
||
|
|
else
|
||
|
|
offset = t->last_off & ~align1;
|
||
|
|
count = 0;
|
||
|
|
for (;;) {
|
||
|
|
off_new = find_next_zero_bit(t->map, t->size, offset);
|
||
|
|
off_new = ((off_new + align1) & ~align1) + color;
|
||
|
|
count += off_new - offset;
|
||
|
|
offset = off_new;
|
||
|
|
if (offset >= t->size)
|
||
|
|
offset = 0;
|
||
|
|
if (count + len > t->size) {
|
||
|
|
spin_unlock(&t->lock);
|
||
|
|
/* P3 */ printk(KERN_ERR
|
||
|
|
"bitmap out: size %d used %d off %d len %d align %d count %d\n",
|
||
|
|
t->size, t->used, offset, len, align, count);
|
||
|
|
return -1;
|
||
|
|
}
|
||
|
|
|
||
|
|
if (offset + len > t->size) {
|
||
|
|
count += t->size - offset;
|
||
|
|
offset = 0;
|
||
|
|
continue;
|
||
|
|
}
|
||
|
|
|
||
|
|
i = 0;
|
||
|
|
while (test_bit(offset + i, t->map) == 0) {
|
||
|
|
i++;
|
||
|
|
if (i == len) {
|
||
|
|
bitmap_set(t->map, offset, len);
|
||
|
|
if (offset == t->first_free)
|
||
|
|
t->first_free = find_next_zero_bit
|
||
|
|
(t->map, t->size,
|
||
|
|
t->first_free + len);
|
||
|
|
if ((t->last_off = offset + len) >= t->size)
|
||
|
|
t->last_off = 0;
|
||
|
|
t->used += len;
|
||
|
|
t->last_size = len;
|
||
|
|
spin_unlock(&t->lock);
|
||
|
|
return offset;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
count += i + 1;
|
||
|
|
if ((offset += i + 1) >= t->size)
|
||
|
|
offset = 0;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
void bit_map_clear(struct bit_map *t, int offset, int len)
|
||
|
|
{
|
||
|
|
int i;
|
||
|
|
|
||
|
|
if (t->used < len)
|
||
|
|
BUG(); /* Much too late to do any good, but alas... */
|
||
|
|
spin_lock(&t->lock);
|
||
|
|
for (i = 0; i < len; i++) {
|
||
|
|
if (test_bit(offset + i, t->map) == 0)
|
||
|
|
BUG();
|
||
|
|
__clear_bit(offset + i, t->map);
|
||
|
|
}
|
||
|
|
if (offset < t->first_free)
|
||
|
|
t->first_free = offset;
|
||
|
|
t->used -= len;
|
||
|
|
spin_unlock(&t->lock);
|
||
|
|
}
|
||
|
|
|
||
|
|
void bit_map_init(struct bit_map *t, unsigned long *map, int size)
|
||
|
|
{
|
||
|
|
bitmap_zero(map, size);
|
||
|
|
memset(t, 0, sizeof *t);
|
||
|
|
spin_lock_init(&t->lock);
|
||
|
|
t->map = map;
|
||
|
|
t->size = size;
|
||
|
|
}
|