// SPDX-License-Identifier: GPL-2.0
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/*
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* Deferred dmabuf freeing helper
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*
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* Copyright (C) 2020 Linaro, Ltd.
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*
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* Based on the ION page pool code
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* Copyright (C) 2011 Google, Inc.
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*/
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#include <linux/freezer.h>
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#include <linux/list.h>
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#include <linux/slab.h>
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#include <linux/swap.h>
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#include <linux/sched/signal.h>
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#include "deferred-free-helper.h"
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static LIST_HEAD(free_list);
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static size_t list_nr_pages;
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wait_queue_head_t freelist_waitqueue;
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struct task_struct *freelist_task;
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static DEFINE_SPINLOCK(free_list_lock);
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void deferred_free(struct deferred_freelist_item *item,
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void (*free)(struct deferred_freelist_item*,
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enum df_reason),
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size_t nr_pages)
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{
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unsigned long flags;
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INIT_LIST_HEAD(&item->list);
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item->nr_pages = nr_pages;
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item->free = free;
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spin_lock_irqsave(&free_list_lock, flags);
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list_add(&item->list, &free_list);
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list_nr_pages += nr_pages;
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spin_unlock_irqrestore(&free_list_lock, flags);
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wake_up(&freelist_waitqueue);
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}
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EXPORT_SYMBOL_GPL(deferred_free);
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static size_t free_one_item(enum df_reason reason)
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{
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unsigned long flags;
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size_t nr_pages;
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struct deferred_freelist_item *item;
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spin_lock_irqsave(&free_list_lock, flags);
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if (list_empty(&free_list)) {
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spin_unlock_irqrestore(&free_list_lock, flags);
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return 0;
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}
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item = list_first_entry(&free_list, struct deferred_freelist_item, list);
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list_del(&item->list);
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nr_pages = item->nr_pages;
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list_nr_pages -= nr_pages;
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spin_unlock_irqrestore(&free_list_lock, flags);
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item->free(item, reason);
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return nr_pages;
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}
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unsigned long get_freelist_nr_pages(void)
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{
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unsigned long nr_pages;
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unsigned long flags;
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spin_lock_irqsave(&free_list_lock, flags);
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nr_pages = list_nr_pages;
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spin_unlock_irqrestore(&free_list_lock, flags);
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return nr_pages;
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}
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EXPORT_SYMBOL_GPL(get_freelist_nr_pages);
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static unsigned long freelist_shrink_count(struct shrinker *shrinker,
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struct shrink_control *sc)
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{
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return get_freelist_nr_pages();
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}
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static unsigned long freelist_shrink_scan(struct shrinker *shrinker,
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struct shrink_control *sc)
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{
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unsigned long total_freed = 0;
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if (sc->nr_to_scan == 0)
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return 0;
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while (total_freed < sc->nr_to_scan) {
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size_t pages_freed = free_one_item(DF_UNDER_PRESSURE);
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if (!pages_freed)
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break;
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total_freed += pages_freed;
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}
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return total_freed;
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}
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static struct shrinker freelist_shrinker = {
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.count_objects = freelist_shrink_count,
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.scan_objects = freelist_shrink_scan,
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.seeks = DEFAULT_SEEKS,
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.batch = 0,
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};
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static int deferred_free_thread(void *data)
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{
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while (true) {
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wait_event_freezable(freelist_waitqueue,
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get_freelist_nr_pages() > 0);
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free_one_item(DF_NORMAL);
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}
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return 0;
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}
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static int deferred_freelist_init(void)
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{
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list_nr_pages = 0;
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init_waitqueue_head(&freelist_waitqueue);
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freelist_task = kthread_run(deferred_free_thread, NULL,
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"%s", "dmabuf-deferred-free-worker");
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if (IS_ERR(freelist_task)) {
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pr_err("Creating thread for deferred free failed\n");
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return -1;
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}
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sched_set_normal(freelist_task, 19);
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return register_shrinker(&freelist_shrinker);
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}
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module_init(deferred_freelist_init);
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MODULE_LICENSE("GPL v2");
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