// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/mm/swap_state.c
 *
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *  Swap reorganised 29.12.95, Stephen Tweedie
 *
 *  Rewritten to use page cache, (C) 1998 Stephen Tweedie
 */

/*
 * Official Linux v6.0: mm/swap_state.c
 * https://github.com/torvalds/linux/blob/v6.0/mm/swap_state.c#L568
 * Exact definition/declaration; not a reconstruction of a book listing.
 * See GPL-2.0.txt. Not a standalone translation unit.
 */

static unsigned long swapin_nr_pages(unsigned long offset)
{
	static unsigned long prev_offset;
	unsigned int hits, pages, max_pages;
	static atomic_t last_readahead_pages;

	max_pages = 1 << READ_ONCE(page_cluster);
	if (max_pages <= 1)
		return 1;

	hits = atomic_xchg(&swapin_readahead_hits, 0);
	pages = __swapin_nr_pages(READ_ONCE(prev_offset), offset, hits,
				  max_pages,
				  atomic_read(&last_readahead_pages));
	if (!hits)
		WRITE_ONCE(prev_offset, offset);
	atomic_set(&last_readahead_pages, pages);

	return pages;
}