/*	$NetBSD: shrinker.h,v 1.5 2021/12/19 01:22:37 riastradh Exp $	*/

/*-
 * Copyright (c) 2013 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Taylor R. Campbell.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef _LINUX_SHRINKER_H_
#define _LINUX_SHRINKER_H_

#include <uvm/uvm.h>

struct shrink_control {
	unsigned long	nr_to_scan;
	unsigned long	nr_scanned;
};

struct shrinker {
	int		(*shrink)(struct shrinker *, struct shrink_control *);
	unsigned long	(*count_objects)(struct shrinker *,
			    struct shrink_control *);
	unsigned long	(*scan_objects)(struct shrinker *,
			    struct shrink_control *);
	int		seeks;
	size_t		batch;
};

#define	SHRINK_STOP	(~0UL)

#define	DEFAULT_SEEKS	2	/* XXX cargo-culted from Linux */

static inline int
register_shrinker(struct shrinker *shrinker __unused)
{
	return 0;
}

static inline void
unregister_shrinker(struct shrinker *shrinker __unused)
{
}

static inline bool
current_is_kswapd(void)
{
	return curlwp == uvm.pagedaemon_lwp;
}

static inline size_t
get_nr_swap_pages(void)
{
	return uvmexp.swpages;
}

#endif  /* _LINUX_SHRINKER_H_ */