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128 lines
2.9 KiB
128 lines
2.9 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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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 <[email protected]> |
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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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