1/*-
2 * Copyright (c) 2020 Emmanuel Vadot <manu@FreeBSD.org>
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
14 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
16 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
17 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
18 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
19 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
20 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
21 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
22 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
23 * SUCH DAMAGE.
24 *
25 * $FreeBSD$
26 */
27
28
29#include <sys/cdefs.h>
30__FBSDID("$FreeBSD$");
31
32#include <sys/param.h>
33#include <sys/systm.h>
34#include <sys/kernel.h>
35#include <sys/queue.h>
36#include <sys/eventhandler.h>
37#include <sys/mutex.h>
38
39#include <linux/shrinker.h>
40
41TAILQ_HEAD(, shrinker) lkpi_shrinkers = TAILQ_HEAD_INITIALIZER(lkpi_shrinkers);
42static struct mtx mtx_shrinker;
43
44int
45linuxkpi_register_shrinker(struct shrinker *s)
46{
47
48	KASSERT(s != NULL, ("NULL shrinker"));
49	KASSERT(s->count_objects != NULL, ("NULL shrinker"));
50	KASSERT(s->scan_objects != NULL, ("NULL shrinker"));
51	mtx_lock(&mtx_shrinker);
52	TAILQ_INSERT_TAIL(&lkpi_shrinkers, s, next);
53	mtx_unlock(&mtx_shrinker);
54	return (0);
55}
56
57void
58linuxkpi_unregister_shrinker(struct shrinker *s)
59{
60
61	mtx_lock(&mtx_shrinker);
62	TAILQ_REMOVE(&lkpi_shrinkers, s, next);
63	mtx_unlock(&mtx_shrinker);
64}
65
66#define	SHRINKER_BATCH	512
67
68static void
69shrinker_shrink(struct shrinker *s)
70{
71	struct shrink_control sc;
72	unsigned long can_free;
73	unsigned long batch;
74	unsigned long scanned = 0;
75	unsigned long ret;
76
77	can_free = s->count_objects(s, &sc);
78	if (can_free <= 0)
79		return;
80
81	batch = s->batch ? s->batch : SHRINKER_BATCH;
82	while (scanned <= can_free) {
83		sc.nr_to_scan = batch;
84		ret = s->scan_objects(s, &sc);
85		if (ret == SHRINK_STOP)
86			break;
87		scanned += batch;
88	}
89}
90
91static void
92linuxkpi_vm_lowmem(void *arg __unused)
93{
94	struct shrinker *s;
95
96	mtx_lock(&mtx_shrinker);
97	TAILQ_FOREACH(s, &lkpi_shrinkers, next) {
98		shrinker_shrink(s);
99	}
100	mtx_unlock(&mtx_shrinker);
101}
102
103static eventhandler_tag lowmem_tag;
104
105static void
106linuxkpi_sysinit_shrinker(void *arg __unused)
107{
108
109	mtx_init(&mtx_shrinker, "lkpi-shrinker", NULL, MTX_DEF);
110	lowmem_tag = EVENTHANDLER_REGISTER(vm_lowmem, linuxkpi_vm_lowmem,
111	    NULL, EVENTHANDLER_PRI_FIRST);
112}
113
114static void
115linuxkpi_sysuninit_shrinker(void *arg __unused)
116{
117
118	mtx_destroy(&mtx_shrinker);
119	EVENTHANDLER_DEREGISTER(vm_lowmem, lowmem_tag);
120}
121
122SYSINIT(linuxkpi_shrinker, SI_SUB_DRIVERS, SI_ORDER_ANY,
123    linuxkpi_sysinit_shrinker, NULL);
124SYSUNINIT(linuxkpi_shrinker, SI_SUB_DRIVERS, SI_ORDER_ANY,
125    linuxkpi_sysuninit_shrinker, NULL);
126