mm/mglru: consolidate common code for retrieving evictable size

Merge commonly used code for counting evictable folios in a lruvec.

No behavior change.

Return unsigned long instead of long as suggested [ Axel Rasmussen ]

Acked-by: Yuanchu Xie <yuanchu@google.com>
Reviewed-by: Barry Song <baohua@kernel.org>
Reviewed-by: Chen Ridong <chenridong@huaweicloud.com>
Reviewed-by: Axel Rasmussen <axelrasmussen@google.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Signed-off-by: Kairui Song <kasong@tencent.com>

Author: ryncsn

mm/vmscan.c

@@ -4102,27 +4102,33 @@ static void set_initial_priority(struct pglist_data *pgdat, struct scan_control
 	sc->priority = clamp(priority, DEF_PRIORITY / 2, DEF_PRIORITY);
 }
 
-static bool lruvec_is_sizable(struct lruvec *lruvec, struct scan_control *sc)
+static unsigned long lruvec_evictable_size(struct lruvec *lruvec, int swappiness)
 {
 	int gen, type, zone;
-	unsigned long total = 0;
-	int swappiness = get_swappiness(lruvec, sc);
+	unsigned long seq, total = 0;
 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
-	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
 	DEFINE_MAX_SEQ(lruvec);
 	DEFINE_MIN_SEQ(lruvec);
 
 	for_each_evictable_type(type, swappiness) {
-		unsigned long seq;
-
 		for (seq = min_seq[type]; seq <= max_seq; seq++) {
 			gen = lru_gen_from_seq(seq);
-
 			for (zone = 0; zone < MAX_NR_ZONES; zone++)
 				total += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L);
 		}
 	}
 
+	return total;
+}
+
+static bool lruvec_is_sizable(struct lruvec *lruvec, struct scan_control *sc)
+{
+	unsigned long total;
+	int swappiness = get_swappiness(lruvec, sc);
+	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
+
+	total = lruvec_evictable_size(lruvec, swappiness);
+
 	/* whether the size is big enough to be helpful */
 	return mem_cgroup_online(memcg) ? (total >> sc->priority) : total;
 }
@@ -4777,28 +4783,14 @@ static int evict_folios(unsigned long nr_to_scan, struct lruvec *lruvec,
 static bool should_run_aging(struct lruvec *lruvec, unsigned long max_seq,
 			     int swappiness, unsigned long *nr_to_scan)
 {
-	int gen, type, zone;
-	unsigned long size = 0;
-	struct lru_gen_folio *lrugen = &lruvec->lrugen;
 	DEFINE_MIN_SEQ(lruvec);
 
 	*nr_to_scan = 0;
 	/* have to run aging, since eviction is not possible anymore */
 	if (evictable_min_seq(min_seq, swappiness) + MIN_NR_GENS > max_seq)
 		return true;
 
-	for_each_evictable_type(type, swappiness) {
-		unsigned long seq;
-
-		for (seq = min_seq[type]; seq <= max_seq; seq++) {
-			gen = lru_gen_from_seq(seq);
-
-			for (zone = 0; zone < MAX_NR_ZONES; zone++)
-				size += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L);
-		}
-	}
-
-	*nr_to_scan = size;
+	*nr_to_scan = lruvec_evictable_size(lruvec, swappiness);
 	/* better to run aging even though eviction is still possible */
 	return evictable_min_seq(min_seq, swappiness) + MIN_NR_GENS == max_seq;
 }