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From:   Waiman Long <llong@redhat.com>
Subject: Re: [PATCH 1/5] mm/memcg: Pass both memcg and lruvec to
 mod_memcg_lruvec_state()
To:     Roman Gushchin <guro@fb.com>
Cc:     Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@kernel.org>,
        Vladimir Davydov <vdavydov.dev@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Tejun Heo <tj@kernel.org>, Christoph Lameter <cl@linux.com>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Vlastimil Babka <vbabka@suse.cz>, linux-kernel@vger.kernel.org,
        cgroups@vger.kernel.org, linux-mm@kvack.org,
        Shakeel Butt <shakeelb@google.com>,
        Muchun Song <songmuchun@bytedance.com>,
        Alex Shi <alex.shi@linux.alibaba.com>,
        Chris Down <chris@chrisdown.name>,
        Yafang Shao <laoar.shao@gmail.com>,
        Alexander Duyck <alexander.h.duyck@linux.intel.com>,
        Wei Yang <richard.weiyang@gmail.com>,
        Masayoshi Mizuma <msys.mizuma@gmail.com>
References: <20210409231842.8840-1-longman@redhat.com>
 <20210409231842.8840-2-longman@redhat.com>
 <YHSLp8bTQGovNLTu@carbon.dhcp.thefacebook.com>
Message-ID: <8a188990-325e-bf89-37ae-f0b29481b738@redhat.com>
Date:   Mon, 12 Apr 2021 15:24:34 -0400
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On 4/12/21 2:04 PM, Roman Gushchin wrote:
> On Fri, Apr 09, 2021 at 07:18:38PM -0400, Waiman Long wrote:
>> The caller of mod_memcg_lruvec_state() has both memcg and lruvec readily
>> available. So both of them are now passed to mod_memcg_lruvec_state()
>> and __mod_memcg_lruvec_state(). The __mod_memcg_lruvec_state() is
>> updated to allow either of the two parameters to be set to null. This
>> makes mod_memcg_lruvec_state() equivalent to mod_memcg_state() if lruvec
>> is null.
> This patch seems to be correct, but it's a bit hard to understand why
> it's required without looking into the rest of the series. Can you, please,
> add a couple of words about it? E.g. we need it to handle stats which do not
> exist on the lruvec level...
>
> Otherwise,
> Acked-by: Roman Gushchin <guro@fb.com>

Good point. Will update the commit log to indicate the change is needed 
for the subsequent patch.

Cheers,
Longman