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Subject: Re: [PATCH v17 14/21] mm/compaction: do page isolation first in
 compaction
From:   Alex Shi <alex.shi@linux.alibaba.com>
To:     Alexander Duyck <alexander.duyck@gmail.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Mel Gorman <mgorman@techsingularity.net>,
        Tejun Heo <tj@kernel.org>, Hugh Dickins <hughd@google.com>,
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        Daniel Jordan <daniel.m.jordan@oracle.com>,
        Yang Shi <yang.shi@linux.alibaba.com>,
        Matthew Wilcox <willy@infradead.org>,
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        Wei Yang <richard.weiyang@gmail.com>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Rong Chen <rong.a.chen@intel.com>
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Date:   Wed, 12 Aug 2020 20:16:06 +0800
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在 2020/8/12 下午7:43, Alex Shi 写道:
>>> Sorry, I still can not follow you here. Compound code part is unchanged
>>> and follow the original logical. So would you like to pose a new code to
>>> see if its works?
>> No there are significant changes as you reordered all of the
>> operations. Prior to your change the LRU bit was checked, but not
>> cleared before testing for PageCompound. Now you are clearing it
>> before you are testing if it is a compound page. So if compaction is
>> running we will be seeing the pages in the LRU stay put, but the
>> compound bit flickering off and on if the compound page is encountered
>> with the wrong or NULL lruvec. What I was suggesting is that the

> The lruvec could be wrong or NULL here, that is the base stone of whole
> patchset.
> 
Sorry for typo. s/could/could not/