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Subject: Re: [RFC PATCH v2 5/5] mm: Split move_pages_to_lru into 3 separate
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To:     Alexander Duyck <alexander.duyck@gmail.com>
Cc:     Yang Shi <yang.shi@linux.alibaba.com>,
        kbuild test robot <lkp@intel.com>,
        Rong Chen <rong.a.chen@intel.com>,
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        Tejun Heo <tj@kernel.org>, cgroups@vger.kernel.org,
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        Mel Gorman <mgorman@techsingularity.net>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>
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From:   Alex Shi <alex.shi@linux.alibaba.com>
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Date:   Thu, 20 Aug 2020 17:56:36 +0800
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在 2020/8/19 下午10:42, Alexander Duyck 写道:
>> It's actually changed the meaning from current func. which I had seen a bug if no relock.
>> but after move to 5.9 kernel, I can not reprodce the bug any more. I am not sure if 5.9 fixed
>> the problem, and we don't need relock here.
> So I am not sure what you mean here about "changed the meaning from
> the current func". Which function are you referring to and what
> changed?
> 
> From what I can tell the pages cannot change memcg because they were
> isolated and had the LRU flag stripped. They shouldn't be able to
> change destination LRU vector as a result. Assuming that, then they
> can all be processed under same LRU lock and we can avoid having to
> release it until we are forced to do so to call putback_lru_page or
> destroy the compound pages that were freed while we were shrinking the
> LRU lists.
> 

I had sent a bug which base on 5.8 kernel.
https://lkml.org/lkml/2020/7/28/465

I am not sure it was fixed in new kernel. The original line was introduced by Hugh Dickins
I believe it would be great if you can get comments from him.

Thanks
Alex