// SPDX-License-Identifier: GPL-2.0
/*
 * 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/string.h>
#include <linux/bitmap.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) {
                                bitmap_set(t->map, offset, len);
                                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)
{
        bitmap_zero(map, size);
        memset(t, 0, sizeof *t);
        spin_lock_init(&t->lock);
        t->map = map;
        t->size = size;
}