1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Deferred dmabuf freeing helper
4 *
5 * Copyright (C) 2020 Linaro, Ltd.
6 *
7 * Based on the ION page pool code
8 * Copyright (C) 2011 Google, Inc.
9 */
10
11 #include <linux/freezer.h>
12 #include <linux/list.h>
13 #include <linux/slab.h>
14 #include <linux/swap.h>
15 #include <linux/sched/signal.h>
16
17 #include "deferred-free-helper.h"
18
19 static LIST_HEAD(free_list);
20 static size_t list_nr_pages;
21 wait_queue_head_t freelist_waitqueue;
22 struct task_struct *freelist_task;
23 static DEFINE_SPINLOCK(free_list_lock);
24
deferred_free(struct deferred_freelist_item * item,void (* free)(struct deferred_freelist_item *,enum df_reason),size_t nr_pages)25 void deferred_free(struct deferred_freelist_item *item, void (*free)(struct deferred_freelist_item *, enum df_reason),
26 size_t nr_pages)
27 {
28 unsigned long flags;
29
30 INIT_LIST_HEAD(&item->list);
31 item->nr_pages = nr_pages;
32 item->free = free;
33
34 spin_lock_irqsave(&free_list_lock, flags);
35 list_add(&item->list, &free_list);
36 list_nr_pages += nr_pages;
37 spin_unlock_irqrestore(&free_list_lock, flags);
38 wake_up(&freelist_waitqueue);
39 }
40 EXPORT_SYMBOL_GPL(deferred_free);
41
free_one_item(enum df_reason reason)42 static size_t free_one_item(enum df_reason reason)
43 {
44 unsigned long flags;
45 size_t nr_pages;
46 struct deferred_freelist_item *item;
47
48 spin_lock_irqsave(&free_list_lock, flags);
49 if (list_empty(&free_list)) {
50 spin_unlock_irqrestore(&free_list_lock, flags);
51 return 0;
52 }
53 item = list_first_entry(&free_list, struct deferred_freelist_item, list);
54 list_del(&item->list);
55 nr_pages = item->nr_pages;
56 list_nr_pages -= nr_pages;
57 spin_unlock_irqrestore(&free_list_lock, flags);
58
59 item->free(item, reason);
60 return nr_pages;
61 }
62
get_freelist_nr_pages(void)63 static unsigned long get_freelist_nr_pages(void)
64 {
65 unsigned long nr_pages;
66 unsigned long flags;
67
68 spin_lock_irqsave(&free_list_lock, flags);
69 nr_pages = list_nr_pages;
70 spin_unlock_irqrestore(&free_list_lock, flags);
71 return nr_pages;
72 }
73
freelist_shrink_count(struct shrinker * shrinker,struct shrink_control * sc)74 static unsigned long freelist_shrink_count(struct shrinker *shrinker, struct shrink_control *sc)
75 {
76 return get_freelist_nr_pages();
77 }
78
freelist_shrink_scan(struct shrinker * shrinker,struct shrink_control * sc)79 static unsigned long freelist_shrink_scan(struct shrinker *shrinker, struct shrink_control *sc)
80 {
81 unsigned long total_freed = 0;
82
83 if (sc->nr_to_scan == 0) {
84 return 0;
85 }
86
87 while (total_freed < sc->nr_to_scan) {
88 size_t pages_freed = free_one_item(DF_UNDER_PRESSURE);
89 if (!pages_freed) {
90 break;
91 }
92
93 total_freed += pages_freed;
94 }
95
96 return total_freed;
97 }
98
99 static struct shrinker freelist_shrinker = {
100 .count_objects = freelist_shrink_count,
101 .scan_objects = freelist_shrink_scan,
102 .seeks = DEFAULT_SEEKS,
103 .batch = 0,
104 };
105
deferred_free_thread(void * data)106 static int deferred_free_thread(void *data)
107 {
108 while (true) {
109 wait_event_freezable(freelist_waitqueue, get_freelist_nr_pages() > 0);
110
111 free_one_item(DF_NORMAL);
112 }
113
114 return 0;
115 }
116
deferred_freelist_init(void)117 static int deferred_freelist_init(void)
118 {
119 list_nr_pages = 0;
120
121 init_waitqueue_head(&freelist_waitqueue);
122 freelist_task = kthread_run(deferred_free_thread, NULL, "%s", "dmabuf-deferred-free-worker");
123 if (IS_ERR(freelist_task)) {
124 pr_err("Creating thread for deferred free failed\n");
125 return -1;
126 }
127 sched_set_normal(freelist_task, 0x13);
128
129 return register_shrinker(&freelist_shrinker);
130 }
131 module_init(deferred_freelist_init);
132 MODULE_LICENSE("GPL v2");
133