Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Thu, 11 Jun 2020 11:40:33 +0200
From:   Michal Hocko <mhocko@kernel.org>
To:     Johannes Weiner <hannes@cmpxchg.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Alex Shi <alex.shi@linux.alibaba.com>,
        Joonsoo Kim <js1304@gmail.com>,
        Shakeel Butt <shakeelb@google.com>,
        Hugh Dickins <hughd@google.com>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Roman Gushchin <guro@fb.com>, linux-mm@kvack.org,
        cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
        kernel-team@fb.com
Subject: Re: [PATCH 19/19] mm: memcontrol: update page->mem_cgroup stability
 rules
Message-ID: <20200611094033.GC20450@dhcp22.suse.cz>
References: <20200508183105.225460-1-hannes@cmpxchg.org>
 <20200508183105.225460-20-hannes@cmpxchg.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20200508183105.225460-20-hannes@cmpxchg.org>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Fri 08-05-20 14:31:06, 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@cmpxchg.org>
> Reviewed-by: Alex Shi <alex.shi@linux.alibaba.com>
> Reviewed-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

Thanks a lot this is a big improvement and simplification.

I have gone through the whole series finally. I have followed up where
necessary but overall this is really nice!

Sorry I couldn't jump in to review in time.
-- 
Michal Hocko
SUSE Labs