[patch 109/158] mm: vmscan: turn shrink_node_memcg() into shrink_lruvec()

[akpm@linux-foundation.org]

From: Johannes Weiner <hannes@cmpxchg.org>
Subject: mm: vmscan: turn shrink_node_memcg() into shrink_lruvec()

An lruvec holds LRU pages owned by a certain NUMA node and cgroup. 
Instead of awkwardly passing around a combination of a pgdat and a memcg
pointer, pass down the lruvec as soon as we can look it up.

Nested callers that need to access node or cgroup properties can look them
them up if necessary, but there are only a few cases.

Link: http://lkml.kernel.org/r/20191022144803.302233-7-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/vmscan.c |   21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

--- a/mm/vmscan.c~mm-vmscan-turn-shrink_node_memcg-into-shrink_lruvec
+++ a/mm/vmscan.c
@@ -2280,9 +2280,10 @@ enum scan_balance {
  * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan
  * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan
  */
-static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg,
-			   struct scan_control *sc, unsigned long *nr)
+static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
+			   unsigned long *nr)
 {
+	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
 	int swappiness = mem_cgroup_swappiness(memcg);
 	struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
 	u64 fraction[2];
@@ -2530,13 +2531,8 @@ out:
 	}
 }
 
-/*
- * This is a basic per-node page freer.  Used by both kswapd and direct reclaim.
- */
-static void shrink_node_memcg(struct pglist_data *pgdat, struct mem_cgroup *memcg,
-			      struct scan_control *sc)
+static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
 {
-	struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
 	unsigned long nr[NR_LRU_LISTS];
 	unsigned long targets[NR_LRU_LISTS];
 	unsigned long nr_to_scan;
@@ -2546,7 +2542,7 @@ static void shrink_node_memcg(struct pgl
 	struct blk_plug plug;
 	bool scan_adjusted;
 
-	get_scan_count(lruvec, memcg, sc, nr);
+	get_scan_count(lruvec, sc, nr);
 
 	/* Record the original scan target for proportional adjustments later */
 	memcpy(targets, nr, sizeof(nr));
@@ -2741,6 +2737,7 @@ again:
 
 	memcg = mem_cgroup_iter(root, NULL, NULL);
 	do {
+		struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
 		unsigned long reclaimed;
 		unsigned long scanned;
 
@@ -2777,7 +2774,8 @@ again:
 
 		reclaimed = sc->nr_reclaimed;
 		scanned = sc->nr_scanned;
-		shrink_node_memcg(pgdat, memcg, sc);
+
+		shrink_lruvec(lruvec, sc);
 
 		shrink_slab(sc->gfp_mask, pgdat->node_id, memcg,
 			    sc->priority);
@@ -3281,6 +3279,7 @@ unsigned long mem_cgroup_shrink_node(str
 						pg_data_t *pgdat,
 						unsigned long *nr_scanned)
 {
+	struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
 	struct scan_control sc = {
 		.nr_to_reclaim = SWAP_CLUSTER_MAX,
 		.target_mem_cgroup = memcg,
@@ -3305,7 +3304,7 @@ unsigned long mem_cgroup_shrink_node(str
 	 * will pick up pages from other mem cgroup's as well. We hack
 	 * the priority and make it zero.
 	 */
-	shrink_node_memcg(pgdat, memcg, &sc);
+	shrink_lruvec(lruvec, &sc);
 
 	trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
 
_