* [PATCH] mm: memcontrol: fix get_active_memcg return value
@ 2021-02-23 9:11 Muchun Song
2021-02-23 15:18 ` Shakeel Butt
2021-02-23 15:35 ` Roman Gushchin
0 siblings, 2 replies; 3+ messages in thread
From: Muchun Song @ 2021-02-23 9:11 UTC (permalink / raw)
To: hannes, mhocko, vdavydov.dev, akpm, guro, shakeelb
Cc: cgroups, linux-mm, linux-kernel, Muchun Song
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 <songmuchun@bytedance.com>
---
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
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] mm: memcontrol: fix get_active_memcg return value
2021-02-23 9:11 [PATCH] mm: memcontrol: fix get_active_memcg return value Muchun Song
@ 2021-02-23 15:18 ` Shakeel Butt
2021-02-23 15:35 ` Roman Gushchin
1 sibling, 0 replies; 3+ messages in thread
From: Shakeel Butt @ 2021-02-23 15:18 UTC (permalink / raw)
To: Muchun Song, stable
Cc: Johannes Weiner, Michal Hocko, Vladimir Davydov, Andrew Morton,
Roman Gushchin, Cgroups, Linux MM, LKML
On Tue, Feb 23, 2021 at 1:14 AM Muchun Song <songmuchun@bytedance.com> 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 <songmuchun@bytedance.com>
Good catch.
Cc: stable@vger.kernel.org
Reviewed-by: Shakeel Butt <shakeelb@google.com>
> ---
> 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
>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] mm: memcontrol: fix get_active_memcg return value
2021-02-23 9:11 [PATCH] mm: memcontrol: fix get_active_memcg return value Muchun Song
2021-02-23 15:18 ` Shakeel Butt
@ 2021-02-23 15:35 ` Roman Gushchin
1 sibling, 0 replies; 3+ messages in thread
From: Roman Gushchin @ 2021-02-23 15:35 UTC (permalink / raw)
To: Muchun Song
Cc: hannes, mhocko, vdavydov.dev, akpm, shakeelb, cgroups, linux-mm,
linux-kernel
On Tue, Feb 23, 2021 at 05:11:01PM +0800, Muchun Song 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 <songmuchun@bytedance.com>
> ---
> 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;
Ouch, this is a good one!
Reviewed-by: Roman Gushchin <guro@fb.com>
Thank you!
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-02-23 9:11 [PATCH] mm: memcontrol: fix get_active_memcg return value Muchun Song
2021-02-23 15:18 ` Shakeel Butt
2021-02-23 15:35 ` Roman Gushchin
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