Re: [PATCH] thp: close race between split and zap huge pages

[Bob Liu]

On Wed, Apr 16, 2014 at 4:42 PM, Kirill A. Shutemov
<kirill@xxxxxxxxxxxxx> wrote:
> On Wed, Apr 16, 2014 at 07:52:29AM +0800, Bob Liu wrote:
>> >         *ptl = pmd_lock(mm, pmd);
>> > -       if (pmd_none(*pmd))
>> > +       if (!pmd_present(*pmd))
>> >                 goto unlock;
>>
>> But I didn't get the idea why pmd_none() was removed?
>
> !pmd_present(*pmd) is weaker check then pmd_none(*pmd). I mean if
> pmd_none(*pmd) is true then pmd_present(*pmd) is always false.

Oh, yes. That's right.

BTW, it looks like this bug was introduced by the same reason.
https://lkml.org/lkml/2014/4/16/403

-- 
Regards,
--Bob
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