// 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 v6.12, mm/vmscan.c:5805-5855.
 * Full function definition; surrounding kernel context is required.
 * Source: https://github.com/torvalds/linux/blob/v6.12/mm/vmscan.c#L5805
 * License text: GPL-2.0.txt (in this directory).
 */
static inline bool should_continue_reclaim(struct pglist_data *pgdat,
					unsigned long nr_reclaimed,
					struct scan_control *sc)
{
	unsigned long pages_for_compaction;
	unsigned long inactive_lru_pages;
	int z;

	/* If not in reclaim/compaction mode, stop */
	if (!in_reclaim_compaction(sc))
		return false;

	/*
	 * Stop if we failed to reclaim any pages from the last SWAP_CLUSTER_MAX
	 * number of pages that were scanned. This will return to the caller
	 * with the risk reclaim/compaction and the resulting allocation attempt
	 * fails. In the past we have tried harder for __GFP_RETRY_MAYFAIL
	 * allocations through requiring that the full LRU list has been scanned
	 * first, by assuming that zero delta of sc->nr_scanned means full LRU
	 * scan, but that approximation was wrong, and there were corner cases
	 * where always a non-zero amount of pages were scanned.
	 */
	if (!nr_reclaimed)
		return false;

	/* If compaction would go ahead or the allocation would succeed, stop */
	for (z = 0; z <= sc->reclaim_idx; z++) {
		struct zone *zone = &pgdat->node_zones[z];
		if (!managed_zone(zone))
			continue;

		/* Allocation can already succeed, nothing to do */
		if (zone_watermark_ok(zone, sc->order, min_wmark_pages(zone),
				      sc->reclaim_idx, 0))
			return false;

		if (compaction_suitable(zone, sc->order, sc->reclaim_idx))
			return false;
	}

	/*
	 * If we have not reclaimed enough pages for compaction and the
	 * inactive lists are large enough, continue reclaiming
	 */
	pages_for_compaction = compact_gap(sc->order);
	inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE);
	if (can_reclaim_anon_pages(NULL, pgdat->node_id, sc))
		inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON);

	return inactive_lru_pages > pages_for_compaction;
}