// SPDX-License-Identifier: GPL-2.0
/*
 * Common Primitives for Data Access Monitoring
 *
 * Author: SeongJae Park <sj@kernel.org>
 */

#include <linux/mmu_notifier.h>
#include <linux/page_idle.h>
#include <linux/pagemap.h>
#include <linux/rmap.h>

#include "prmtv-common.h"

/*
 * Get an online page for a pfn if it's in the LRU list.  Otherwise, returns
 * NULL.
 *
 * The body of this function is stolen from the 'page_idle_get_page()'.  We
 * steal rather than reuse it because the code is quite simple.
 */
struct page *damon_get_page(unsigned long pfn)
{
	struct page *page = pfn_to_online_page(pfn);

	if (!page || !PageLRU(page) || !get_page_unless_zero(page))
		return NULL;

	if (unlikely(!PageLRU(page))) {
		put_page(page);
		page = NULL;
	}
	return page;
}

void damon_ptep_mkold(pte_t *pte, struct mm_struct *mm, unsigned long addr)
{
	bool referenced = false;
	struct page *page = damon_get_page(pte_pfn(*pte));

	if (!page)
		return;

	if (pte_young(*pte)) {
		referenced = true;
		*pte = pte_mkold(*pte);
	}

#ifdef CONFIG_MMU_NOTIFIER
	if (mmu_notifier_clear_young(mm, addr, addr + PAGE_SIZE))
		referenced = true;
#endif /* CONFIG_MMU_NOTIFIER */

	if (referenced)
		set_page_young(page);

	set_page_idle(page);
	put_page(page);
}

void damon_pmdp_mkold(pmd_t *pmd, struct mm_struct *mm, unsigned long addr)
{
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
	bool referenced = false;
	struct page *page = damon_get_page(pmd_pfn(*pmd));

	if (!page)
		return;

	if (pmd_young(*pmd)) {
		referenced = true;
		*pmd = pmd_mkold(*pmd);
	}

#ifdef CONFIG_MMU_NOTIFIER
	if (mmu_notifier_clear_young(mm, addr,
				addr + ((1UL) << HPAGE_PMD_SHIFT)))
		referenced = true;
#endif /* CONFIG_MMU_NOTIFIER */

	if (referenced)
		set_page_young(page);

	set_page_idle(page);
	put_page(page);
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
}