// SPDX-License-Identifier: GPL-2.0
/*
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *
 *  Swap reorganised 29.12.95, Stephen Tweedie.
 *  kswapd added: 7.1.96  sct
 *  Removed kswapd_ctl limits, and swap out as many pages as needed
 *  to bring the system back to freepages.high: 2.4.97, Rik van Riel.
 *  Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
 *  Multiqueue VM started 5.8.00, Rik van Riel.
 */

/* Extracted unchanged from Linux v6.18, mm/vmscan.c:512-538.
 * Complete function definition; surrounding kernel context is required.
 * Source: https://github.com/torvalds/linux/blob/v6.18/mm/vmscan.c#L512
 * License text: GPL-2.0.txt (in this directory).
 */
static bool skip_throttle_noprogress(pg_data_t *pgdat)
{
	int reclaimable = 0, write_pending = 0;
	int i;
	struct zone *zone;
	/*
	 * If kswapd is disabled, reschedule if necessary but do not
	 * throttle as the system is likely near OOM.
	 */
	if (atomic_read(&pgdat->kswapd_failures) >= MAX_RECLAIM_RETRIES)
		return true;

	/*
	 * If there are a lot of dirty/writeback folios then do not
	 * throttle as throttling will occur when the folios cycle
	 * towards the end of the LRU if still under writeback.
	 */
	for_each_managed_zone_pgdat(zone, pgdat, i, MAX_NR_ZONES - 1) {
		reclaimable += zone_reclaimable_pages(zone);
		write_pending += zone_page_state_snapshot(zone,
						  NR_ZONE_WRITE_PENDING);
	}
	if (2 * write_pending <= reclaimable)
		return true;

	return false;
}