Re: [PATCH 2/3] mm: Charge active memcg when no mm is set

[Shakeel Butt]

On Thu, Jun 3, 2021 at 7:57 AM Dan Schatzberg <schatzberg.dan@xxxxxxxxx> wrote:
>
> set_active_memcg() worked for kernel allocations but was silently
> ignored for user pages.
>
> This patch establishes a precedence order for who gets charged:
>
> 1. If there is a memcg associated with the page already, that memcg is
>    charged. This happens during swapin.
>
> 2. If an explicit mm is passed, mm->memcg is charged. This happens
>    during page faults, which can be triggered in remote VMs (eg gup).
>
> 3. Otherwise consult the current process context. If there is an
>    active_memcg, use that. Otherwise, current->mm->memcg.
>
> Previously, if a NULL mm was passed to mem_cgroup_charge (case 3) it
> would always charge the root cgroup. Now it looks up the active_memcg
> first (falling back to charging the root cgroup if not set).
>
> Signed-off-by: Dan Schatzberg <schatzberg.dan@xxxxxxxxx>
> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> Acked-by: Tejun Heo <tj@xxxxxxxxxx>
> Acked-by: Chris Down <chris@xxxxxxxxxxxxxx>
> Acked-by: Jens Axboe <axboe@xxxxxxxxx>
> Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>

Can you please rebase over the latest mm tree? Specifically over
Muchun's patch "mm: memcontrol: bail out early when !mm in
get_mem_cgroup_from_mm".