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:   Fri, 2 Oct 2020 09:25:57 -0400
From:   Johannes Weiner <hannes@cmpxchg.org>
To:     Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>
Cc:     Roman Gushchin <guro@fb.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Shakeel Butt <shakeelb@google.com>,
        Michal Hocko <mhocko@kernel.org>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, kernel-team@fb.com
Subject: Re: [PATCH v4 4/4] mm: convert page kmemcg type to a page memcg flag
Message-ID: <20201002132557.GA525590@cmpxchg.org>
References: <20201001002710.748166-1-guro@fb.com>
 <20201001002710.748166-5-guro@fb.com>
 <20201001170036.GA29848@blackbook>
 <20201001172713.GA500308@cmpxchg.org>
 <20201002100350.GC24008@blackbody.suse.cz>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <20201002100350.GC24008@blackbody.suse.cz>
Precedence: bulk

On Fri, Oct 02, 2020 at 12:03:50PM +0200, Michal Koutn? wrote:
> On Thu, Oct 01, 2020 at 01:27:13PM -0400, Johannes Weiner <hannes@cmpxchg.org> wrote:
> > I do think there is a bug, though: mem_cgroup_move_account() should
> > use WRITE_ONCE() on page->mem_cgroup.
> If this were a bug, wouldn't be the proper approach
> rcu_assign_pointer()/rcu_dereference() pair?

Yes, you're right.

I'll double check these code paths and follow up with a patch if
necessary.