linux-kernel - Re: [PATCH v17 14/21] mm/compaction: do page isolation first in compaction

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Date:   Fri, 7 Aug 2020 11:24:35 +0800
From:   Alex Shi <alex.shi@...ux.alibaba.com>
To:     Alexander Duyck <alexander.duyck@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Tejun Heo <tj@...nel.org>, Hugh Dickins <hughd@...gle.com>,
        Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        Yang Shi <yang.shi@...ux.alibaba.com>,
        Matthew Wilcox <willy@...radead.org>,
        Johannes Weiner <hannes@...xchg.org>,
        kbuild test robot <lkp@...el.com>,
        linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>, cgroups@...r.kernel.org,
        Shakeel Butt <shakeelb@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Wei Yang <richard.weiyang@...il.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Rong Chen <rong.a.chen@...el.com>
Subject: Re: [PATCH v17 14/21] mm/compaction: do page isolation first in
 compaction



在 2020/8/7 上午2:38, Alexander Duyck 写道:
>> +
>>  isolate_abort:
>>         if (locked)
>>                 spin_unlock_irqrestore(&pgdat->lru_lock, flags);
>> +       if (page) {
>> +               SetPageLRU(page);
>> +               put_page(page);
>> +       }
>>
>>         /*
>>          * Updated the cached scanner pfn once the pageblock has been scanned
> We should probably be calling SetPageLRU before we release the lru
> lock instead of before. It might make sense to just call it before we
> get here, similar to how you did in the isolate_fail_put case a few
> lines later. Otherwise this seems to violate the rules you had set up
> earlier where we were only going to be setting the LRU bit while
> holding the LRU lock.

Hi Alex,

Set out of lock here should be fine. I never said we must set the bit in locking.
And this page is get by get_page_unless_zero(), no warry on release.

Thanks
Alex