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 */
27int 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
102void 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
120void 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}
128