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