tegra-linux-noble/fs/erofs/utils.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2018 HUAWEI, Inc.
 *             https://www.huawei.com/
 * Copyright (C) 2024 Alibaba Cloud
 */
#include "internal.h"

struct page *erofs_allocpage(struct page **pagepool, gfp_t gfp)
{
	struct page *page = *pagepool;

	if (page) {
		DBG_BUGON(page_ref_count(page) != 1);
		*pagepool = (struct page *)page_private(page);
	} else {
		page = alloc_page(gfp);
	}
	return page;
}

void erofs_release_pages(struct page **pagepool)
{
	while (*pagepool) {
		struct page *page = *pagepool;

		*pagepool = (struct page *)page_private(page);
		put_page(page);
	}
}

#ifdef CONFIG_EROFS_FS_ZIP
/* global shrink count (for all mounted EROFS instances) */
atomic_long_t erofs_global_shrink_cnt;

/* protects `erofs_sb_list_lock` and the mounted `erofs_sb_list` */
static DEFINE_SPINLOCK(erofs_sb_list_lock);
static LIST_HEAD(erofs_sb_list);
static unsigned int shrinker_run_no;

void erofs_shrinker_register(struct super_block *sb)
{
	struct erofs_sb_info *sbi = EROFS_SB(sb);

	mutex_init(&sbi->umount_mutex);

	spin_lock(&erofs_sb_list_lock);
	list_add(&sbi->list, &erofs_sb_list);
	spin_unlock(&erofs_sb_list_lock);
}

void erofs_shrinker_unregister(struct super_block *sb)
{
	struct erofs_sb_info *const sbi = EROFS_SB(sb);

	mutex_lock(&sbi->umount_mutex);
	/* clean up all remaining pclusters in memory */
	z_erofs_shrink_scan(sbi, ~0UL);

	spin_lock(&erofs_sb_list_lock);
	list_del(&sbi->list);
	spin_unlock(&erofs_sb_list_lock);
	mutex_unlock(&sbi->umount_mutex);
}

static unsigned long erofs_shrink_count(struct shrinker *shrink,
					struct shrink_control *sc)
{
	return atomic_long_read(&erofs_global_shrink_cnt);
}

static unsigned long erofs_shrink_scan(struct shrinker *shrink,
				       struct shrink_control *sc)
{
	struct erofs_sb_info *sbi;
	struct list_head *p;

	unsigned long nr = sc->nr_to_scan;
	unsigned int run_no;
	unsigned long freed = 0;

	spin_lock(&erofs_sb_list_lock);
	do {
		run_no = ++shrinker_run_no;
	} while (run_no == 0);

	/* Iterate over all mounted superblocks and try to shrink them */
	p = erofs_sb_list.next;
	while (p != &erofs_sb_list) {
		sbi = list_entry(p, struct erofs_sb_info, list);

		/*
		 * We move the ones we do to the end of the list, so we stop
		 * when we see one we have already done.
		 */
		if (sbi->shrinker_run_no == run_no)
			break;

		if (!mutex_trylock(&sbi->umount_mutex)) {
			p = p->next;
			continue;
		}

		spin_unlock(&erofs_sb_list_lock);
		sbi->shrinker_run_no = run_no;
		freed += z_erofs_shrink_scan(sbi, nr - freed);
		spin_lock(&erofs_sb_list_lock);
		/* Get the next list element before we move this one */
		p = p->next;

		/*
		 * Move this one to the end of the list to provide some
		 * fairness.
		 */
		list_move_tail(&sbi->list, &erofs_sb_list);
		mutex_unlock(&sbi->umount_mutex);

		if (freed >= nr)
			break;
	}
	spin_unlock(&erofs_sb_list_lock);
	return freed;
}

static struct shrinker *erofs_shrinker_info;

int __init erofs_init_shrinker(void)
{
	erofs_shrinker_info = shrinker_alloc(0, "erofs-shrinker");
	if (!erofs_shrinker_info)
		return -ENOMEM;

	erofs_shrinker_info->count_objects = erofs_shrink_count;
	erofs_shrinker_info->scan_objects = erofs_shrink_scan;

	shrinker_register(erofs_shrinker_info);

	return 0;
}

void erofs_exit_shrinker(void)
{
	shrinker_free(erofs_shrinker_info);
}
#endif	/* !CONFIG_EROFS_FS_ZIP */