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Message-Id: <20220621125658.64935-2-songmuchun@bytedance.com>
Date: Tue, 21 Jun 2022 20:56:48 +0800
From: Muchun Song <songmuchun@...edance.com>
To: akpm@...ux-foundation.org, hannes@...xchg.org, longman@...hat.com,
mhocko@...nel.org, roman.gushchin@...ux.dev, shakeelb@...gle.com
Cc: cgroups@...r.kernel.org, duanxiongchun@...edance.com,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
Muchun Song <songmuchun@...edance.com>
Subject: [PATCH v6 01/11] mm: memcontrol: remove dead code and comments
Since no-hierarchy mode is deprecated after
commit bef8620cd8e0 ("mm: memcg: deprecate the non-hierarchical mode")
so parent_mem_cgroup() cannot return a NULL except root memcg, however, root
memcg cannot be offline, so it is safe to drop the check of returned value
of parent_mem_cgroup(). Remove those dead code.
The comments in memcg_offline_kmem() above memcg_reparent_list_lrus() are
out of date since
commit 5abc1e37afa0 ("mm: list_lru: allocate list_lru_one only when needed")
There is no ordering requirement between memcg_reparent_list_lrus() and
memcg_reparent_objcgs(), so remove those outdated comments.
Signed-off-by: Muchun Song <songmuchun@...edance.com>
Acked-by: Roman Gushchin <roman.gushchin@...ux.dev>
---
include/linux/memcontrol.h | 3 +--
mm/memcontrol.c | 12 ------------
mm/vmscan.c | 6 +-----
3 files changed, 2 insertions(+), 19 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 4d31ce55b1c0..318d8880d62a 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -866,8 +866,7 @@ static inline struct mem_cgroup *lruvec_memcg(struct lruvec *lruvec)
* parent_mem_cgroup - find the accounting parent of a memcg
* @memcg: memcg whose parent to find
*
- * Returns the parent memcg, or NULL if this is the root or the memory
- * controller is in legacy no-hierarchy mode.
+ * Returns the parent memcg, or NULL if this is the root.
*/
static inline struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *memcg)
{
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 163492b9efa9..fc706d6fc265 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3684,17 +3684,7 @@ static void memcg_offline_kmem(struct mem_cgroup *memcg)
return;
parent = parent_mem_cgroup(memcg);
- if (!parent)
- parent = root_mem_cgroup;
-
memcg_reparent_objcgs(memcg, parent);
-
- /*
- * After we have finished memcg_reparent_objcgs(), all list_lrus
- * corresponding to this cgroup are guaranteed to remain empty.
- * The ordering is imposed by list_lru_node->lock taken by
- * memcg_reparent_list_lrus().
- */
memcg_reparent_list_lrus(memcg, parent);
}
#else
@@ -7195,8 +7185,6 @@ static struct mem_cgroup *mem_cgroup_id_get_online(struct mem_cgroup *memcg)
break;
}
memcg = parent_mem_cgroup(memcg);
- if (!memcg)
- memcg = root_mem_cgroup;
}
return memcg;
}
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 88fce64cfa96..b68b0216424d 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -409,13 +409,9 @@ void reparent_shrinker_deferred(struct mem_cgroup *memcg)
{
int i, nid;
long nr;
- struct mem_cgroup *parent;
+ struct mem_cgroup *parent = parent_mem_cgroup(memcg);
struct shrinker_info *child_info, *parent_info;
- parent = parent_mem_cgroup(memcg);
- if (!parent)
- parent = root_mem_cgroup;
-
/* Prevent from concurrent shrinker_info expand */
down_read(&shrinker_rwsem);
for_each_node(nid) {
--
2.11.0
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