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Subject: Re: [PATCH v16 15/22] mm/compaction: do page isolation first in
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To:     Alexander Duyck <alexander.duyck@gmail.com>
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From:   Alex Shi <alex.shi@linux.alibaba.com>
Message-ID: <dd0a75b5-c8b2-8b66-79b9-0f6ce259e227@linux.alibaba.com>
Date:   Sun, 19 Jul 2020 11:59:36 +0800
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在 2020/7/18 上午12:09, Alexander Duyck 写道:
>>> I wonder if it wouldn't make sense to combine these two atomic ops
>>> with tests and the put_page into a single inline function? Then it
>>> could be possible to just do one check and if succeeds you do the
>>> block of code below, otherwise you just fall-through into the -EBUSY
>>> case.
>>>
>> Uh, since get_page changes page->_refcount, TestClearPageLRU changes page->flags,
>> So I don't know how to combine them, could you make it more clear with code?
> Actually it is pretty straight forward. Something like this:
> static inline bool get_page_unless_zero_or_nonlru(struct page *page)
> {
>     if (get_page_unless_zero(page)) {
>         if (TestClearPageLRU(page))
>             return true;
>         put_page(page);
>     }
>     return false;
> }
> 
> You can then add comments as necessary. The general idea is you are
> having to do this in two different spots anyway so why not combine the
> logic? Although it does assume you can change the ordering of the
> other test above.


It doesn't look different with original code, does it?

Thanks
Alex