1// SPDX-License-Identifier: GPL-2.0
2/*
3 * bitext.c: kernel little helper (of bit shuffling variety).
4 *
5 * Copyright (C) 2002 Pete Zaitcev <zaitcev@yahoo.com>
6 *
7 * The algorithm to search a zero bit string is geared towards its application.
8 * We expect a couple of fixed sizes of requests, so a rotating counter, reset
9 * by align size, should provide fast enough search while maintaining low
10 * fragmentation.
11 */
12
13#include <linux/string.h>
14#include <linux/bitmap.h>
15
16#include <asm/bitext.h>
17
18/**
19 * bit_map_string_get - find and set a bit string in bit map.
20 * @t: the bit map.
21 * @len: requested string length
22 * @align: requested alignment
23 *
24 * Returns offset in the map or -1 if out of space.
25 *
26 * Not safe to call from an interrupt (uses spin_lock).
27 */
28int bit_map_string_get(struct bit_map *t, int len, int align)
29{
30	int offset, count;	/* siamese twins */
31	int off_new;
32	int align1;
33	int i, color;
34
35	if (t->num_colors) {
36		/* align is overloaded to be the page color */
37		color = align;
38		align = t->num_colors;
39	} else {
40		color = 0;
41		if (align == 0)
42			align = 1;
43	}
44	align1 = align - 1;
45	if ((align & align1) != 0)
46		BUG();
47	if (align < 0 || align >= t->size)
48		BUG();
49	if (len <= 0 || len > t->size)
50		BUG();
51	color &= align1;
52
53	spin_lock(&t->lock);
54	if (len < t->last_size)
55		offset = t->first_free;
56	else
57		offset = t->last_off & ~align1;
58	count = 0;
59	for (;;) {
60		off_new = find_next_zero_bit(t->map, t->size, offset);
61		off_new = ((off_new + align1) & ~align1) + color;
62		count += off_new - offset;
63		offset = off_new;
64		if (offset >= t->size)
65			offset = 0;
66		if (count + len > t->size) {
67			spin_unlock(&t->lock);
68/* P3 */ printk(KERN_ERR
69  "bitmap out: size %d used %d off %d len %d align %d count %d\n",
70  t->size, t->used, offset, len, align, count);
71			return -1;
72		}
73
74		if (offset + len > t->size) {
75			count += t->size - offset;
76			offset = 0;
77			continue;
78		}
79
80		i = 0;
81		while (test_bit(offset + i, t->map) == 0) {
82			i++;
83			if (i == len) {
84				bitmap_set(t->map, offset, len);
85				if (offset == t->first_free)
86					t->first_free = find_next_zero_bit
87							(t->map, t->size,
88							 t->first_free + len);
89				if ((t->last_off = offset + len) >= t->size)
90					t->last_off = 0;
91				t->used += len;
92				t->last_size = len;
93				spin_unlock(&t->lock);
94				return offset;
95			}
96		}
97		count += i + 1;
98		if ((offset += i + 1) >= t->size)
99			offset = 0;
100	}
101}
102
103void bit_map_clear(struct bit_map *t, int offset, int len)
104{
105	int i;
106
107	if (t->used < len)
108		BUG();		/* Much too late to do any good, but alas... */
109	spin_lock(&t->lock);
110	for (i = 0; i < len; i++) {
111		if (test_bit(offset + i, t->map) == 0)
112			BUG();
113		__clear_bit(offset + i, t->map);
114	}
115	if (offset < t->first_free)
116		t->first_free = offset;
117	t->used -= len;
118	spin_unlock(&t->lock);
119}
120
121void bit_map_init(struct bit_map *t, unsigned long *map, int size)
122{
123	bitmap_zero(map, size);
124	memset(t, 0, sizeof *t);
125	spin_lock_init(&t->lock);
126	t->map = map;
127	t->size = size;
128}
129