Re: [PATCH 1/4] mm, memcontrol: avoid duplicated memcg enable check

[Kairui Song <ryncsn@gmail.com>]

On Tue, Dec 3, 2024 at 3:11 AM Yosry Ahmed <yosryahmed@google.com> wrote:
>
> On Mon, Dec 2, 2024 at 10:42 AM Kairui Song <ryncsn@gmail.com> wrote:
> >
> > From: Kairui Song <kasong@tencent.com>
> >
> > mem_cgroup_uncharge_swap() implies a mem_cgroup_disabled() check,
> > which is already checked by the caller here. Skip it by calling
> > __mem_cgroup_uncharge_swap() directly.
> >
> > Signed-off-by: Kairui Song <kasong@tencent.com>
> > ---
> >  mm/memcontrol.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index 7b3503d12aaf..d3d1eb506eee 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -4615,7 +4615,7 @@ void mem_cgroup_swapin_uncharge_swap(swp_entry_t entry, unsigned int nr_pages)
> >                  * let's not wait for it.  The page already received a
> >                  * memory+swap charge, drop the swap entry duplicate.
> >                  */
> > -               mem_cgroup_uncharge_swap(entry, nr_pages);
> > +               __mem_cgroup_uncharge_swap(entry, nr_pages);
>
> Would it be better to instead remove the mem_cgroup_disabled() check
> here and have a single check in this path?

Good suggestion, and the kernel test bot just reported
__mem_cgroup_uncharge_swap is undefined with !CONFIG_SWAP, so better
to fix it by removing the check instead.

>
> Anyway, FWIW:
>
> Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
>
> >         }
> >  }
> >
> > --
> > 2.47.0
> >
>