Check shrinker enablement early, and use a less costly stat flushing.

Suggested-by: Yosry Ahmed <yosryah...@google.com>
Suggested-by: Chengming Zhou <chengming.z...@linux.dev>
Signed-off-by: Nhat Pham <npha...@gmail.com>
---
 mm/zswap.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index 27c749f6c1ba..d8ecd79120f3 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -596,13 +596,17 @@ static unsigned long zswap_shrinker_scan(struct shrinker 
*shrinker,
        struct zswap_pool *pool = shrinker->private_data;
        bool encountered_page_in_swapcache = false;
 
+       if (!zswap_shrinker_enabled) {
+               sc->nr_scanned = 0;
+               return SHRINK_STOP;
+       }
+
        nr_protected =
                
atomic_long_read(&lruvec->zswap_lruvec_state.nr_zswap_protected);
        lru_size = list_lru_shrink_count(&pool->list_lru, sc);
 
        /*
-        * Abort if the shrinker is disabled or if we are shrinking into the
-        * protected region.
+        * Abort if we are shrinking into the protected region.
         *
         * This short-circuiting is necessary because if we have too many 
multiple
         * concurrent reclaimers getting the freeable zswap object counts at the
@@ -611,7 +615,7 @@ static unsigned long zswap_shrinker_scan(struct shrinker 
*shrinker,
         * objects (i.e the reclaimers will reclaim into the protected area of 
the
         * zswap LRU).
         */
-       if (!zswap_shrinker_enabled || nr_protected >= lru_size - 
sc->nr_to_scan) {
+       if (nr_protected >= lru_size - sc->nr_to_scan) {
                sc->nr_scanned = 0;
                return SHRINK_STOP;
        }
@@ -633,8 +637,11 @@ static unsigned long zswap_shrinker_count(struct shrinker 
*shrinker,
        struct lruvec *lruvec = mem_cgroup_lruvec(memcg, NODE_DATA(sc->nid));
        unsigned long nr_backing, nr_stored, nr_freeable, nr_protected;
 
+       if (!zswap_shrinker_enabled)
+               return 0;
+
 #ifdef CONFIG_MEMCG_KMEM
-       cgroup_rstat_flush(memcg->css.cgroup);
+       mem_cgroup_flush_stats();
        nr_backing = memcg_page_state(memcg, MEMCG_ZSWAP_B) >> PAGE_SHIFT;
        nr_stored = memcg_page_state(memcg, MEMCG_ZSWAPPED);
 #else
@@ -643,7 +650,7 @@ static unsigned long zswap_shrinker_count(struct shrinker 
*shrinker,
        nr_stored = atomic_read(&pool->nr_stored);
 #endif
 
-       if (!zswap_shrinker_enabled || !nr_stored)
+       if (!nr_stored)
                return 0;
 
        nr_protected =
-- 
2.34.1

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