Re: [External] RE: kernel warning percpu ref in obj_cgroup_release

[Muchun Song]

On Wed, Mar 31, 2021 at 2:22 PM Christian Borntraeger
<borntraeger@xxxxxxxxxx> wrote:
>
>
>
> On 30.03.21 18:25, Muchun Song wrote:
> > On Tue, Mar 30, 2021 at 11:10 PM Christian Borntraeger
> > <borntraeger@xxxxxxxxxx> wrote:
> >>
> >>
> >> On 30.03.21 15:49, Muchun Song wrote:
> >>> On Tue, Mar 30, 2021 at 9:27 PM Christian Borntraeger
> >>> <borntraeger@xxxxxxxxxx> wrote:
> >>>>
> >>>> So bisect shows this for belows warning:
> >>>
> >>> Thanks for your effort on this. Can you share your config?
> >>
> >> attached (but its s390x) for next-20210330
> >
> > Thanks. Can you apply the following patch and help me test?
> > Very Thanks.
> >
> > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> > index 7fdc92e1983e..579408e4d46f 100644
> > --- a/include/linux/memcontrol.h
> > +++ b/include/linux/memcontrol.h
> > @@ -793,6 +793,12 @@ static inline void obj_cgroup_get(struct obj_cgroup *objcg)
> >          percpu_ref_get(&objcg->refcnt);
> >   }
> >
> > +static inline void obj_cgroup_get_many(struct obj_cgroup *objcg,
> > +                                      unsigned long nr)
> > +{
> > +       percpu_ref_get_many(&objcg->refcnt, nr);
> > +}
> > +
> >   static inline void obj_cgroup_put(struct obj_cgroup *objcg)
> >   {
> >          percpu_ref_put(&objcg->refcnt);
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index c0b83a396299..1634dba1044c 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -3133,7 +3133,10 @@ void split_page_memcg(struct page *head, unsigned int nr)
> >
> >          for (i = 1; i < nr; i++)
> >                  head[i].memcg_data = head->memcg_data;
> > -       css_get_many(&memcg->css, nr - 1);
> > +       if (PageMemcgKmem(head))
> > +               obj_cgroup_get_many(__page_objcg(head), nr - 1);
> > +       else
> > +               css_get_many(&memcg->css, nr - 1);
> >   }
> >
> >   #ifdef CONFIG_MEMCG_SWAP

Hi Andrew,

Now we have two choices to fix this issue.

1) Send a v6 patchset (Use obj_cgroup APIs to charge kmem pages)
    to fix this issue.
2) Send a separate fix patch (Just like above).

Both ways are ok for me. But I want to know which one is more
convenient for you.

Thanks.

> >
>
> This one seems to do the trick, I can no longer see the warning.