[PATCH v4 28/31] mm: workingset: use lruvec_lru_size() to get the number of lru pages

[Qi Zheng <qi.zheng@linux.dev>]

From: Qi Zheng <zhengqi.arch@bytedance.com>

For cgroup v2, count_shadow_nodes() is the only place to read
non-hierarchical stats (lruvec_stats->state_local). To avoid the need to
consider cgroup v2 during subsequent non-hierarchical stats reparenting,
use lruvec_lru_size() instead of lruvec_page_state_local() to get the
number of lru pages.

For NR_SLAB_RECLAIMABLE_B and NR_SLAB_UNRECLAIMABLE_B cases, it appears
that the statistics here have already been problematic for a while since
slab pages have been reparented. So just ignore it for now.

Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
---
 include/linux/swap.h | 1 +
 mm/vmscan.c          | 3 +--
 mm/workingset.c      | 5 +++--
 3 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 62e124ec6b75a..2ee736438b9d6 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -370,6 +370,7 @@ extern void swap_setup(void);
 extern unsigned long zone_reclaimable_pages(struct zone *zone);
 extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
 					gfp_t gfp_mask, nodemask_t *mask);
+unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru, int zone_idx);
 
 #define MEMCG_RECLAIM_MAY_SWAP (1 << 1)
 #define MEMCG_RECLAIM_PROACTIVE (1 << 2)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 8c6f8f0df24b1..4dc52b4b4af50 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -390,8 +390,7 @@ unsigned long zone_reclaimable_pages(struct zone *zone)
  * @lru: lru to use
  * @zone_idx: zones to consider (use MAX_NR_ZONES - 1 for the whole LRU list)
  */
-static unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru,
-				     int zone_idx)
+unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru, int zone_idx)
 {
 	unsigned long size = 0;
 	int zid;
diff --git a/mm/workingset.c b/mm/workingset.c
index 2be53098f6282..ecdc293cd06fb 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -684,9 +684,10 @@ static unsigned long count_shadow_nodes(struct shrinker *shrinker,
 
 		mem_cgroup_flush_stats_ratelimited(sc->memcg);
 		lruvec = mem_cgroup_lruvec(sc->memcg, NODE_DATA(sc->nid));
+
 		for (pages = 0, i = 0; i < NR_LRU_LISTS; i++)
-			pages += lruvec_page_state_local(lruvec,
-							 NR_LRU_BASE + i);
+			pages += lruvec_lru_size(lruvec, i, MAX_NR_ZONES - 1);
+
 		pages += lruvec_page_state_local(
 			lruvec, NR_SLAB_RECLAIMABLE_B) >> PAGE_SHIFT;
 		pages += lruvec_page_state_local(
-- 
2.20.1