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 <songmuc...@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 <g...@fb.com> Thank you!