[RFC v1 09/19] mm, vmscan: use for_each_node in shrink_zones()

[Pengfei Li <fly@kernel.page>]

In shrink_zones(), we want to traverse node instead of zone, so
use for_each_node instead of for_each_zone.

Signed-off-by: Pengfei Li <fly@kernel.page>
---
 mm/vmscan.c | 53 ++++++++++++++++++++++++++++++-----------------------
 1 file changed, 30 insertions(+), 23 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index b5256ef682c2..2b0e51525c3a 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2910,6 +2910,25 @@ static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
 	return zone_watermark_ok_safe(zone, 0, watermark, sc->reclaim_idx);
 }
 
+static bool
+node_compaction_ready(struct nlist_traverser *t, struct scan_control *sc)
+{
+	bool node_ready = true;
+	struct zone *zone;
+
+	do {
+		zone = traverser_zone(t);
+
+		if (compaction_ready(zone, sc))
+			sc->compaction_ready = true;
+		else
+			node_ready = false;
+
+	} while (t->usable_zones);
+
+	return node_ready;
+}
+
 /*
  * This is the direct reclaim path, for page-allocating processes.  We only
  * try to reclaim pages from zones which will satisfy the caller's allocation
@@ -2920,12 +2939,12 @@ static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
  */
 static void shrink_zones(struct nodelist *nodelist, struct scan_control *sc)
 {
-	struct nlist_traverser t;
-	struct zone *zone;
 	unsigned long nr_soft_reclaimed;
 	unsigned long nr_soft_scanned;
 	gfp_t orig_mask;
-	pg_data_t *last_pgdat = NULL;
+	pg_data_t *pgdat;
+	struct nlist_traverser t;
+	int node;
 
 	/*
 	 * If the number of buffer_heads in the machine exceeds the maximum
@@ -2938,14 +2957,17 @@ static void shrink_zones(struct nodelist *nodelist, struct scan_control *sc)
 		sc->reclaim_idx = gfp_zone(sc->gfp_mask);
 	}
 
-	for_each_zone_nlist_nodemask(zone, &t, nodelist,
+	for_each_node_nlist_nodemask(node, &t, nodelist,
 					sc->reclaim_idx, sc->nodemask) {
+
+		pgdat = NODE_DATA(node);
+
 		/*
 		 * Take care memory controller reclaiming has small influence
 		 * to global LRU.
 		 */
 		if (!cgroup_reclaim(sc)) {
-			if (!cpuset_zone_allowed(zone,
+			if (!cpuset_node_allowed(node,
 						 GFP_KERNEL | __GFP_HARDWALL))
 				continue;
 
@@ -2960,18 +2982,7 @@ static void shrink_zones(struct nodelist *nodelist, struct scan_control *sc)
 			 */
 			if (IS_ENABLED(CONFIG_COMPACTION) &&
 			    sc->order > PAGE_ALLOC_COSTLY_ORDER &&
-			    compaction_ready(zone, sc)) {
-				sc->compaction_ready = true;
-				continue;
-			}
-
-			/*
-			 * Shrink each node in the zonelist once. If the
-			 * zonelist is ordered by zone (not the default) then a
-			 * node may be shrunk multiple times but in that case
-			 * the user prefers lower zones being preserved.
-			 */
-			if (zone->zone_pgdat == last_pgdat)
+			    node_compaction_ready(&t, sc))
 				continue;
 
 			/*
@@ -2981,7 +2992,7 @@ static void shrink_zones(struct nodelist *nodelist, struct scan_control *sc)
 			 * and balancing, not for a memcg's limit.
 			 */
 			nr_soft_scanned = 0;
-			nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone->zone_pgdat,
+			nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(pgdat,
 						sc->order, sc->gfp_mask,
 						&nr_soft_scanned);
 			sc->nr_reclaimed += nr_soft_reclaimed;
@@ -2989,11 +3000,7 @@ static void shrink_zones(struct nodelist *nodelist, struct scan_control *sc)
 			/* need some check for avoid more shrink_zone() */
 		}
 
-		/* See comment about same check for global reclaim above */
-		if (zone->zone_pgdat == last_pgdat)
-			continue;
-		last_pgdat = zone->zone_pgdat;
-		shrink_node(zone->zone_pgdat, sc);
+		shrink_node(pgdat, sc);
 	}
 
 	/*
-- 
2.23.0