| Message ID | 20210223091101.42150-1-songmuchun@bytedance.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm: memcontrol: fix get_active_memcg return value | expand |
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 >
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!
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;
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(-)