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// SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
/*
* Simple power-of-two buddy allocation mechanism.
*
* Copyright 2016 IBM Corp.
*/
#ifndef __BUDDY_H
#define __BUDDY_H
#include "bitmap.h"
#define BUDDY_MAX_ORDER 30
struct buddy {
/* max_order is both the height of the tree - 1 and the ^2 of the
* size of the lowest level.
*
* So if we have 512k elements, max_order is 19, which gives us
* a 20 levels tree.
*
* The max supported order is 30 for now. We can increase that
* later if really needed but the performance is going to be
* already pretty bad if we go near that limit.
*/
unsigned int max_order;
/* For each order, we keep track of how many free modes we
* have there to speed up searches.
*/
unsigned int freecounts[BUDDY_MAX_ORDER + 1];
bitmap_elem_t map[];
};
extern struct buddy *buddy_create(unsigned int max_order);
extern void buddy_destroy(struct buddy *b);
extern int buddy_alloc(struct buddy *b, unsigned int order);
extern bool buddy_reserve(struct buddy *b, unsigned int index, unsigned int order);
extern void buddy_free(struct buddy *b, unsigned int index, unsigned int order);
extern void buddy_reset(struct buddy *b);
#endif /* __BUDDY_H */
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