From: Chen Wandun <chenwandun@huawei.com>
Subject: mm/page_alloc: simplify update of pgdat in wake_all_kswapds

There is no need to update last_pgdat for each zone, only update
last_pgdat when iterating the first zone of a node.

Link: https://lkml.kernel.org/r/20220322115635.2708989-1-chenwandun@huawei.com
Signed-off-by: Chen Wandun <chenwandun@huawei.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/page_alloc.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/mm/page_alloc.c~mm-page_alloc-simplify-update-of-pgdat-in-wake_all_kswapds
+++ a/mm/page_alloc.c
@@ -4678,9 +4678,10 @@ static void wake_all_kswapds(unsigned in
 
 	for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, highest_zoneidx,
 					ac->nodemask) {
-		if (last_pgdat != zone->zone_pgdat)
+		if (last_pgdat != zone->zone_pgdat) {
 			wakeup_kswapd(zone, gfp_mask, order, highest_zoneidx);
-		last_pgdat = zone->zone_pgdat;
+			last_pgdat = zone->zone_pgdat;
+		}
 	}
 }
 
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