linux-kernel - Re: [PATCH rfc 3/5] mm: memcontrol/slab: use helpers to access slab page's memcg

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Message-ID: <20200917164916.GA1583192@carbon.dhcp.thefacebook.com>
Date:   Thu, 17 Sep 2020 09:49:16 -0700
From:   Roman Gushchin <guro@...com>
To:     Shakeel Butt <shakeelb@...gle.com>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Kernel Team <kernel-team@...com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH rfc 3/5] mm: memcontrol/slab: use helpers to access slab
 page's memcg_data

On Wed, Sep 16, 2020 at 06:12:37PM -0700, Shakeel Butt wrote:
> On Thu, Sep 10, 2020 at 1:27 PM Roman Gushchin <guro@...com> wrote:
> >
> > To gather all direct accesses to struct page's memcg_data field
> > in one place, let's introduce 4 new helper functions to use in
> > the slab accounting code:
> >   struct obj_cgroup **page_obj_cgroups(struct page *page);
> >   struct obj_cgroup **page_obj_cgroups_check(struct page *page);
> >   bool set_page_obj_cgroups(struct page *page, struct obj_cgroup **objcgs);
> >   void clear_page_obj_cgroups(struct page *page);
> >
> > They are similar to the corresponding API for generic pages, except
> > that the setter can return false, indicating that the value has been
> > already set from a different thread.
> >
> > Signed-off-by: Roman Gushchin <guro@...com>
> 
> Nit below.
> 
> Reviewed-by: Shakeel Butt <shakeelb@...gle.com>
> 
> > ---
> >  include/linux/memcontrol.h | 48 ++++++++++++++++++++++++++++++++++++++
> >  mm/memcontrol.c            |  4 ++--
> >  mm/slab.h                  | 27 +++------------------
> >  3 files changed, 53 insertions(+), 26 deletions(-)
> >
> > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> > index 0997220c84ce..48d4c2c1ce81 100644
> > --- a/include/linux/memcontrol.h
> > +++ b/include/linux/memcontrol.h
> > @@ -375,6 +375,54 @@ static inline void clear_page_mem_cgroup(struct page *page)
> >         page->memcg_data = 0;
> >  }
> >
> 
> I think adding comments on these functions would be helpful.

I agree, will add.

Thank you for taking a look!

Roman