Re: [PATCH] mm: memcontrol: fix get_active_memcg return value
From: Shakeel Butt <hidden>
Date: 2021-02-23 15:20:50
Also in:
cgroups, linux-mm, lkml
On Tue, Feb 23, 2021 at 1:14 AM Muchun Song [off-list ref] wrote:
We use a global percpu int_active_memcg variable to store the remote
memcg when we are in the interrupt context. But get_active_memcg always
return the current->active_memcg or root_mem_cgroup. The remote memcg
(set in the interrupt context) is ignored. This is not what we want.
So fix it.
Fixes: 37d5985c003d ("mm: kmem: prepare remote memcg charging infra for interrupt contexts")
Signed-off-by: Muchun Song <redacted>Good catch. Cc: stable@vger.kernel.org Reviewed-by: Shakeel Butt <redacted>
quoted hunk
--- mm/memcontrol.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-)diff --git a/mm/memcontrol.c b/mm/memcontrol.c index be6bc5044150..bbe25655f7eb 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c@@ -1061,13 +1061,9 @@ static __always_inline struct mem_cgroup *get_active_memcg(void) rcu_read_lock(); memcg = active_memcg(); - if (memcg) { - /* current->active_memcg must hold a ref. */ - if (WARN_ON_ONCE(!css_tryget(&memcg->css))) - memcg = root_mem_cgroup; - else - memcg = current->active_memcg; - } + /* remote memcg must hold a ref. */ + if (memcg && WARN_ON_ONCE(!css_tryget(&memcg->css))) + memcg = root_mem_cgroup; rcu_read_unlock(); return memcg; --2.11.0