linux-kernel - Re: [v2 PATCH 2/2] mm: don't warn if the node is offlined

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Date:   Fri, 4 Nov 2022 10:42:45 -0700
From:   Yang Shi <shy828301@...il.com>
To:     Michal Hocko <mhocko@...e.com>
Cc:     zokeefe@...gle.com, akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [v2 PATCH 2/2] mm: don't warn if the node is offlined

On Fri, Nov 4, 2022 at 2:56 AM Michal Hocko <mhocko@...e.com> wrote:
>
> On Fri 04-11-22 10:35:21, Michal Hocko wrote:
> [...]
> > diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> > index ef4aea3b356e..308daafc4871 100644
> > --- a/include/linux/gfp.h
> > +++ b/include/linux/gfp.h
> > @@ -227,7 +227,10 @@ static inline
> >  struct folio *__folio_alloc_node(gfp_t gfp, unsigned int order, int nid)
> >  {
> >       VM_BUG_ON(nid < 0 || nid >= MAX_NUMNODES);
> > -     VM_WARN_ON((gfp & __GFP_THISNODE) && !node_online(nid));
> > +     if((gfp & __GFP_THISNODE) && !node_online(nid)) {
>
> or maybe even better
>         if ((gfp & (__GFP_THISNODE|__GFP_NOWARN) == __GFP_THISNODE|__GFP_NOWARN) && !node_online(nid))
>
> because it doesn't really make much sense to dump this information if
> the allocation failure is going to provide sufficient (and even more
> comprehensive) context for the failure. It looks more hairy but this can
> be hidden in a nice little helper shared between the two callers.

Thanks a lot for the suggestion, printing warning if the gfp flag
allows sounds like a good idea to me. Will adopt it. But the check
should look like:

if ((gfp & __GFP_THISNODE) && !(gfp & __GFP_NOWARN) && !node_online(nid))

>
> > +             pr_warn("%pGg allocation from offline node %d\n", &gfp, nid);
> > +             dump_stack();
> > +     }
> >
> >       return __folio_alloc(gfp, order, nid, NULL);
> >  }
> > --
> > Michal Hocko
> > SUSE Labs
>
> --
> Michal Hocko
> SUSE Labs