// 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:7250-7293.
 * Full function definition; surrounding kernel context is required.
 * Source: https://github.com/torvalds/linux/blob/v6.12/mm/vmscan.c#L7250
 * License text: GPL-2.0.txt (in this directory).
 */
void wakeup_kswapd(struct zone *zone, gfp_t gfp_flags, int order,
		   enum zone_type highest_zoneidx)
{
	pg_data_t *pgdat;
	enum zone_type curr_idx;

	if (!managed_zone(zone))
		return;

	if (!cpuset_zone_allowed(zone, gfp_flags))
		return;

	pgdat = zone->zone_pgdat;
	curr_idx = READ_ONCE(pgdat->kswapd_highest_zoneidx);

	if (curr_idx == MAX_NR_ZONES || curr_idx < highest_zoneidx)
		WRITE_ONCE(pgdat->kswapd_highest_zoneidx, highest_zoneidx);

	if (READ_ONCE(pgdat->kswapd_order) < order)
		WRITE_ONCE(pgdat->kswapd_order, order);

	if (!waitqueue_active(&pgdat->kswapd_wait))
		return;

	/* Hopeless node, leave it to direct reclaim if possible */
	if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES ||
	    (pgdat_balanced(pgdat, order, highest_zoneidx) &&
	     !pgdat_watermark_boosted(pgdat, highest_zoneidx))) {
		/*
		 * There may be plenty of free memory available, but it's too
		 * fragmented for high-order allocations.  Wake up kcompactd
		 * and rely on compaction_suitable() to determine if it's
		 * needed.  If it fails, it will defer subsequent attempts to
		 * ratelimit its work.
		 */
		if (!(gfp_flags & __GFP_DIRECT_RECLAIM))
			wakeup_kcompactd(pgdat, order, highest_zoneidx);
		return;
	}

	trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, highest_zoneidx, order,
				      gfp_flags);
	wake_up_interruptible(&pgdat->kswapd_wait);
}