1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
|
/*
* 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/smp_lock.h>
#include <linux/string.h>
#include <linux/bitops.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) {
for (i = 0; i < len; i++)
__set_bit(offset + i, t->map);
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)
{
if ((size & 07) != 0)
BUG();
memset(map, 0, size>>3);
memset(t, 0, sizeof *t);
spin_lock_init(&t->lock);
t->map = map;
t->size = size;
}
|
