Re: fs/buffer.c: WARNING: alloc_page_buffers while mke2fs

[Yang Shi <shy828301@gmail.com>]

On Tue, Mar 3, 2020 at 10:40 AM Naresh Kamboju
<naresh.kamboju@linaro.org> wrote:
>
> On Tue, 3 Mar 2020 at 23:17, Yang Shi <shy828301@gmail.com> wrote:
> >
> > On Tue, Mar 3, 2020 at 2:53 AM Tetsuo Handa
> > <penguin-kernel@i-love.sakura.ne.jp> wrote:
> > >
> > > Hello, Naresh.
> > >
> > > > [   98.003346] WARNING: CPU: 2 PID: 340 at
> > > > include/linux/sched/mm.h:323 alloc_page_buffers+0x210/0x288
> <Trim>
> > >
> > Could you please try the below debug patch? This is not the proper
> > fix, but it may help us narrow down the problem.
> >
> > diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
> > index c49257a..1cc1cdc 100644
> > --- a/include/linux/sched/mm.h
> > +++ b/include/linux/sched/mm.h
> > @@ -320,6 +320,10 @@ static inline void
> > memalloc_nocma_restore(unsigned int flags)
> >   */
> >  static inline void memalloc_use_memcg(struct mem_cgroup *memcg)
> >  {
> > +       if ((current->flags & PF_KTHREAD) &&
> > +            current->active_memcg)
> > +               return;
> > +
> >         WARN_ON_ONCE(current->active_memcg);
> >         current->active_memcg = memcg;
> >  }
>
> After applying this patch the reported "warning" did not happen.
> Here is the full test log.
> https://lkft.validation.linaro.org/scheduler/job/1265325#L1287

Thanks for doing testing. We could confirm this is caused by
paralleled memalloc_use_memcg().

>
> - Naresh