1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0
2*4882a593Smuzhiyun /*
3*4882a593Smuzhiyun * Deferred dmabuf freeing helper
4*4882a593Smuzhiyun *
5*4882a593Smuzhiyun * Copyright (C) 2020 Linaro, Ltd.
6*4882a593Smuzhiyun *
7*4882a593Smuzhiyun * Based on the ION page pool code
8*4882a593Smuzhiyun * Copyright (C) 2011 Google, Inc.
9*4882a593Smuzhiyun */
10*4882a593Smuzhiyun
11*4882a593Smuzhiyun #include <linux/freezer.h>
12*4882a593Smuzhiyun #include <linux/list.h>
13*4882a593Smuzhiyun #include <linux/slab.h>
14*4882a593Smuzhiyun #include <linux/swap.h>
15*4882a593Smuzhiyun #include <linux/sched/signal.h>
16*4882a593Smuzhiyun
17*4882a593Smuzhiyun #include "deferred-free-helper.h"
18*4882a593Smuzhiyun
19*4882a593Smuzhiyun static LIST_HEAD(free_list);
20*4882a593Smuzhiyun static size_t list_nr_pages;
21*4882a593Smuzhiyun wait_queue_head_t freelist_waitqueue;
22*4882a593Smuzhiyun struct task_struct *freelist_task;
23*4882a593Smuzhiyun static DEFINE_SPINLOCK(free_list_lock);
24*4882a593Smuzhiyun
deferred_free(struct deferred_freelist_item * item,void (* free)(struct deferred_freelist_item *,enum df_reason),size_t nr_pages)25*4882a593Smuzhiyun void deferred_free(struct deferred_freelist_item *item,
26*4882a593Smuzhiyun void (*free)(struct deferred_freelist_item*,
27*4882a593Smuzhiyun enum df_reason),
28*4882a593Smuzhiyun size_t nr_pages)
29*4882a593Smuzhiyun {
30*4882a593Smuzhiyun unsigned long flags;
31*4882a593Smuzhiyun
32*4882a593Smuzhiyun INIT_LIST_HEAD(&item->list);
33*4882a593Smuzhiyun item->nr_pages = nr_pages;
34*4882a593Smuzhiyun item->free = free;
35*4882a593Smuzhiyun
36*4882a593Smuzhiyun spin_lock_irqsave(&free_list_lock, flags);
37*4882a593Smuzhiyun list_add(&item->list, &free_list);
38*4882a593Smuzhiyun list_nr_pages += nr_pages;
39*4882a593Smuzhiyun spin_unlock_irqrestore(&free_list_lock, flags);
40*4882a593Smuzhiyun wake_up(&freelist_waitqueue);
41*4882a593Smuzhiyun }
42*4882a593Smuzhiyun EXPORT_SYMBOL_GPL(deferred_free);
43*4882a593Smuzhiyun
free_one_item(enum df_reason reason)44*4882a593Smuzhiyun static size_t free_one_item(enum df_reason reason)
45*4882a593Smuzhiyun {
46*4882a593Smuzhiyun unsigned long flags;
47*4882a593Smuzhiyun size_t nr_pages;
48*4882a593Smuzhiyun struct deferred_freelist_item *item;
49*4882a593Smuzhiyun
50*4882a593Smuzhiyun spin_lock_irqsave(&free_list_lock, flags);
51*4882a593Smuzhiyun if (list_empty(&free_list)) {
52*4882a593Smuzhiyun spin_unlock_irqrestore(&free_list_lock, flags);
53*4882a593Smuzhiyun return 0;
54*4882a593Smuzhiyun }
55*4882a593Smuzhiyun item = list_first_entry(&free_list, struct deferred_freelist_item, list);
56*4882a593Smuzhiyun list_del(&item->list);
57*4882a593Smuzhiyun nr_pages = item->nr_pages;
58*4882a593Smuzhiyun list_nr_pages -= nr_pages;
59*4882a593Smuzhiyun spin_unlock_irqrestore(&free_list_lock, flags);
60*4882a593Smuzhiyun
61*4882a593Smuzhiyun item->free(item, reason);
62*4882a593Smuzhiyun return nr_pages;
63*4882a593Smuzhiyun }
64*4882a593Smuzhiyun
get_freelist_nr_pages(void)65*4882a593Smuzhiyun unsigned long get_freelist_nr_pages(void)
66*4882a593Smuzhiyun {
67*4882a593Smuzhiyun unsigned long nr_pages;
68*4882a593Smuzhiyun unsigned long flags;
69*4882a593Smuzhiyun
70*4882a593Smuzhiyun spin_lock_irqsave(&free_list_lock, flags);
71*4882a593Smuzhiyun nr_pages = list_nr_pages;
72*4882a593Smuzhiyun spin_unlock_irqrestore(&free_list_lock, flags);
73*4882a593Smuzhiyun return nr_pages;
74*4882a593Smuzhiyun }
75*4882a593Smuzhiyun EXPORT_SYMBOL_GPL(get_freelist_nr_pages);
76*4882a593Smuzhiyun
freelist_shrink_count(struct shrinker * shrinker,struct shrink_control * sc)77*4882a593Smuzhiyun static unsigned long freelist_shrink_count(struct shrinker *shrinker,
78*4882a593Smuzhiyun struct shrink_control *sc)
79*4882a593Smuzhiyun {
80*4882a593Smuzhiyun return get_freelist_nr_pages();
81*4882a593Smuzhiyun }
82*4882a593Smuzhiyun
freelist_shrink_scan(struct shrinker * shrinker,struct shrink_control * sc)83*4882a593Smuzhiyun static unsigned long freelist_shrink_scan(struct shrinker *shrinker,
84*4882a593Smuzhiyun struct shrink_control *sc)
85*4882a593Smuzhiyun {
86*4882a593Smuzhiyun unsigned long total_freed = 0;
87*4882a593Smuzhiyun
88*4882a593Smuzhiyun if (sc->nr_to_scan == 0)
89*4882a593Smuzhiyun return 0;
90*4882a593Smuzhiyun
91*4882a593Smuzhiyun while (total_freed < sc->nr_to_scan) {
92*4882a593Smuzhiyun size_t pages_freed = free_one_item(DF_UNDER_PRESSURE);
93*4882a593Smuzhiyun
94*4882a593Smuzhiyun if (!pages_freed)
95*4882a593Smuzhiyun break;
96*4882a593Smuzhiyun
97*4882a593Smuzhiyun total_freed += pages_freed;
98*4882a593Smuzhiyun }
99*4882a593Smuzhiyun
100*4882a593Smuzhiyun return total_freed;
101*4882a593Smuzhiyun }
102*4882a593Smuzhiyun
103*4882a593Smuzhiyun static struct shrinker freelist_shrinker = {
104*4882a593Smuzhiyun .count_objects = freelist_shrink_count,
105*4882a593Smuzhiyun .scan_objects = freelist_shrink_scan,
106*4882a593Smuzhiyun .seeks = DEFAULT_SEEKS,
107*4882a593Smuzhiyun .batch = 0,
108*4882a593Smuzhiyun };
109*4882a593Smuzhiyun
deferred_free_thread(void * data)110*4882a593Smuzhiyun static int deferred_free_thread(void *data)
111*4882a593Smuzhiyun {
112*4882a593Smuzhiyun while (true) {
113*4882a593Smuzhiyun wait_event_freezable(freelist_waitqueue,
114*4882a593Smuzhiyun get_freelist_nr_pages() > 0);
115*4882a593Smuzhiyun
116*4882a593Smuzhiyun free_one_item(DF_NORMAL);
117*4882a593Smuzhiyun }
118*4882a593Smuzhiyun
119*4882a593Smuzhiyun return 0;
120*4882a593Smuzhiyun }
121*4882a593Smuzhiyun
deferred_freelist_init(void)122*4882a593Smuzhiyun static int deferred_freelist_init(void)
123*4882a593Smuzhiyun {
124*4882a593Smuzhiyun list_nr_pages = 0;
125*4882a593Smuzhiyun
126*4882a593Smuzhiyun init_waitqueue_head(&freelist_waitqueue);
127*4882a593Smuzhiyun freelist_task = kthread_run(deferred_free_thread, NULL,
128*4882a593Smuzhiyun "%s", "dmabuf-deferred-free-worker");
129*4882a593Smuzhiyun if (IS_ERR(freelist_task)) {
130*4882a593Smuzhiyun pr_err("Creating thread for deferred free failed\n");
131*4882a593Smuzhiyun return -1;
132*4882a593Smuzhiyun }
133*4882a593Smuzhiyun sched_set_normal(freelist_task, 19);
134*4882a593Smuzhiyun
135*4882a593Smuzhiyun return register_shrinker(&freelist_shrinker);
136*4882a593Smuzhiyun }
137*4882a593Smuzhiyun module_init(deferred_freelist_init);
138*4882a593Smuzhiyun MODULE_LICENSE("GPL v2");
139*4882a593Smuzhiyun
140