From mboxrd@z Thu Jan  1 00:00:00 1970
From: Joonsoo Kim <js1304-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH 18/18] mm: memcontrol: update page->mem_cgroup stability
 rules
Date: Fri, 24 Apr 2020 09:48:03 +0900
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References: <20200420221126.341272-1-hannes@cmpxchg.org>
 <20200420221126.341272-19-hannes@cmpxchg.org>
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To: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
Cc: Alex Shi <alex.shi-KPsoFbNs7GizrGE5bRqYAgC/G2K4zDHf@public.gmane.org>, Shakeel Butt <shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Hugh Dickins <hughd-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Michal Hocko <mhocko-IBi9RG/b67k@public.gmane.org>, "Kirill A. Shutemov" <kirill-oKw7cIdHH8eLwutG50LtGA@public.gmane.org>, Roman Gushchin <guro-b10kYP2dOMg@public.gmane.org>, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kernel-team-b10kYP2dOMg@public.gmane.org

On Mon, Apr 20, 2020 at 06:11:26PM -0400, Johannes Weiner wrote:
> The previous patches have simplified the access rules around
> page->mem_cgroup somewhat:
> 
> 1. We never change page->mem_cgroup while the page is isolated by
>    somebody else. This was by far the biggest exception to our rules
>    and it didn't stop at lock_page() or lock_page_memcg().
> 
> 2. We charge pages before they get put into page tables now, so the
>    somewhat fishy rule about "can be in page table as long as it's
>    still locked" is now gone and boiled down to having an exclusive
>    reference to the page.
> 
> Document the new rules. Any of the following will stabilize the
> page->mem_cgroup association:
> 
> - the page lock
> - LRU isolation
> - lock_page_memcg()
> - exclusive access to the page
> 
> Signed-off-by: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>

Reviewed-by: Joonsoo Kim <iamjoonsoo.kim-Hm3cg6mZ9cc@public.gmane.org>