// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/mm/swapfile.c
 *
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *  Swap reorganised 29.12.95, Stephen Tweedie
 */

/*
 * Official Linux v6.12: mm/swapfile.c
 * https://github.com/torvalds/linux/blob/v6.12/mm/swapfile.c#L1830
 * Exact definition/declaration; not a reconstruction of a book listing.
 * See GPL-2.0.txt. Not a standalone translation unit.
 */

static bool folio_swapcache_freeable(struct folio *folio)
{
	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);

	if (!folio_test_swapcache(folio))
		return false;
	if (folio_test_writeback(folio))
		return false;

	/*
	 * Once hibernation has begun to create its image of memory,
	 * there's a danger that one of the calls to folio_free_swap()
	 * - most probably a call from __try_to_reclaim_swap() while
	 * hibernation is allocating its own swap pages for the image,
	 * but conceivably even a call from memory reclaim - will free
	 * the swap from a folio which has already been recorded in the
	 * image as a clean swapcache folio, and then reuse its swap for
	 * another page of the image.  On waking from hibernation, the
	 * original folio might be freed under memory pressure, then
	 * later read back in from swap, now with the wrong data.
	 *
	 * Hibernation suspends storage while it is writing the image
	 * to disk so check that here.
	 */
	if (pm_suspended_storage())
		return false;

	return true;
}