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Date:   Tue,  5 Oct 2021 16:24:50 -0400
From:   Waiman Long <longman@...hat.com>
To:     Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>, Roman Gushchin <guro@...com>
Cc:     linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        linux-mm@...ck.org, Shakeel Butt <shakeelb@...gle.com>,
        Muchun Song <songmuchun@...edance.com>,
        Waiman Long <longman@...hat.com>
Subject: [PATCH v2] mm/memcg: Remove obsolete memcg_free_kmem()

Since commit d648bcc7fe65 ("mm: kmem: make memcg_kmem_enabled()
irreversible"), the only thing memcg_free_kmem() does is to call
memcg_offline_kmem() when the memcg is still online which can happen when
online_css() fails due to -ENOMEM. However, the name memcg_free_kmem()
is confusing and it is more clear and straight forward to call
memcg_offline_kmem() directly from mem_cgroup_css_free().

Suggested-by: Roman Gushchin <guro@...com>
Signed-off-by: Waiman Long <longman@...hat.com>
---
 mm/memcontrol.c | 14 +++-----------
 1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6da5020a8656..96a93c608d80 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3656,13 +3656,6 @@ static void memcg_offline_kmem(struct mem_cgroup *memcg)
 
 	memcg_free_cache_id(kmemcg_id);
 }
-
-static void memcg_free_kmem(struct mem_cgroup *memcg)
-{
-	/* css_alloc() failed, offlining didn't happen */
-	if (unlikely(memcg->kmem_state == KMEM_ONLINE))
-		memcg_offline_kmem(memcg);
-}
 #else
 static int memcg_online_kmem(struct mem_cgroup *memcg)
 {
@@ -3671,9 +3664,6 @@ static int memcg_online_kmem(struct mem_cgroup *memcg)
 static void memcg_offline_kmem(struct mem_cgroup *memcg)
 {
 }
-static void memcg_free_kmem(struct mem_cgroup *memcg)
-{
-}
 #endif /* CONFIG_MEMCG_KMEM */
 
 static int memcg_update_kmem_max(struct mem_cgroup *memcg,
@@ -5308,7 +5298,9 @@ static void mem_cgroup_css_free(struct cgroup_subsys_state *css)
 	cancel_work_sync(&memcg->high_work);
 	mem_cgroup_remove_from_trees(memcg);
 	free_shrinker_info(memcg);
-	memcg_free_kmem(memcg);
+
+	/* Need to offline kmem if online_css() fails */
+	memcg_offline_kmem(memcg);
 	mem_cgroup_free(memcg);
 }
 
-- 
2.18.1

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