linux-kernel - Re: [PATCH v10 0/3] Charge loop device i/o to issuing cgroup

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Message-ID: <CALvZod6FMQQC17Zsu9xoKs=dFWaJdMC2Qk3YiDPUUQHx8teLYg@mail.gmail.com>
Date:   Thu, 18 Mar 2021 17:56:28 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Jens Axboe <axboe@...nel.dk>,
        Dan Schatzberg <schatzberg.dan@...il.com>,
        Tejun Heo <tj@...nel.org>, Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Hugh Dickins <hughd@...gle.com>, Roman Gushchin <guro@...com>,
        Muchun Song <songmuchun@...edance.com>,
        Alex Shi <alex.shi@...ux.alibaba.com>,
        Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
        Chris Down <chris@...isdown.name>,
        Yafang Shao <laoar.shao@...il.com>,
        Wei Yang <richard.weiyang@...il.com>,
        "open list:BLOCK LAYER" <linux-block@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:CONTROL GROUP (CGROUP)" <cgroups@...r.kernel.org>,
        "open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>
Subject: Re: [PATCH v10 0/3] Charge loop device i/o to issuing cgroup

On Thu, Mar 18, 2021 at 4:46 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> On Thu, 18 Mar 2021 10:00:17 -0600 Jens Axboe <axboe@...nel.dk> wrote:
>
> > On 3/18/21 9:53 AM, Shakeel Butt wrote:
> > > On Wed, Mar 17, 2021 at 3:30 PM Jens Axboe <axboe@...nel.dk> wrote:
> > >>
> > >> On 3/16/21 9:36 AM, Dan Schatzberg wrote:
> > >>> No major changes, just rebasing and resubmitting
> > >>
> > >> Applied for 5.13, thanks.
> > >>
> > >
> > > I have requested a couple of changes in the patch series. Can this
> > > applied series still be changed or new patches are required?
> >
> > I have nothing sitting on top of it for now, so as far as I'm concerned
> > we can apply a new series instead. Then we can also fold in that fix
> > from Colin that he posted this morning...
>
> The collision in memcontrol.c is a pain, but I guess as this is mainly
> a loop patch, the block tree is an appropriate route.
>
> Here's the collision between "mm: Charge active memcg when no mm is
> set" and Shakeels's
> https://lkml.kernel.org/r/20210305212639.775498-1-shakeelb@google.com
>
>
> --- mm/memcontrol.c
> +++ mm/memcontrol.c
> @@ -6728,8 +6730,15 @@ int mem_cgroup_charge(struct page *page, struct mm_struct *mm, gfp_t gfp_mask)
>                 rcu_read_unlock();
>         }
>
> -       if (!memcg)
> -               memcg = get_mem_cgroup_from_mm(mm);
> +       if (!memcg) {
> +               if (!mm) {
> +                       memcg = get_mem_cgroup_from_current();
> +                       if (!memcg)
> +                               memcg = get_mem_cgroup_from_mm(current->mm);
> +               } else {
> +                       memcg = get_mem_cgroup_from_mm(mm);
> +               }
> +       }
>
>         ret = try_charge(memcg, gfp_mask, nr_pages);
>         if (ret)
>
>
> Which I resolved thusly:
>
> int mem_cgroup_charge(struct page *page, struct mm_struct *mm, gfp_t gfp_mask)
> {
>         struct mem_cgroup *memcg;
>         int ret;
>
>         if (mem_cgroup_disabled())
>                 return 0;
>
>         if (!mm) {
>                 memcg = get_mem_cgroup_from_current();
>                 (!memcg)
>                         memcg = get_mem_cgroup_from_mm(current->mm);
>         } else {
>                 memcg = get_mem_cgroup_from_mm(mm);
>         }
>
>         ret = __mem_cgroup_charge(page, memcg, gfp_mask);
>         css_put(&memcg->css);
>
>         return ret;
> }
>

We need something similar for mem_cgroup_swapin_charge_page() as well.

It is better to take this series in mm tree and Jens is ok with that [1].

[1] https://lore.kernel.org/linux-next/4fea89a5-0e18-0791-18a8-4c5907b0d2c4@kernel.dk/