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SubjectRe: [PATCH 2/2] x86,mem-hotplug: modify PGD entry when removing memory
(2014/06/25 0:12), Toshi Kani wrote:
> On Tue, 2014-06-24 at 09:31 +0900, Yasuaki Ishimatsu wrote:
>> (2014/06/21 3:30), Toshi Kani wrote:
>>> On Wed, 2014-06-18 at 15:38 +0900, Yasuaki Ishimatsu wrote:
>>> :
>>>> @@ -186,7 +186,12 @@ void sync_global_pgds(unsigned long start, unsigned long end)
>>>> const pgd_t *pgd_ref = pgd_offset_k(address);
>>>> struct page *page;
>>>>
>>>> - if (pgd_none(*pgd_ref))
>>>> + /*
>>>> + * When it is called after memory hot remove, pgd_none()
>>>> + * returns true. In this case (removed == 1), we must clear
>>>> + * the PGD entries in the local PGD level page.
>>>> + */
>>>> + if (pgd_none(*pgd_ref) && !removed)
>>>> continue;
>>>>
>>>> spin_lock(&pgd_lock);
>>>> @@ -199,12 +204,18 @@ void sync_global_pgds(unsigned long start, unsigned long end)
>>>> pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
>>>> spin_lock(pgt_lock);
>>>>
>>>> - if (pgd_none(*pgd))
>>>> - set_pgd(pgd, *pgd_ref);
>>>> - else
>>
>>>> + if (!pgd_none(*pgd_ref) && !pgd_none(*pgd))
>>>> BUG_ON(pgd_page_vaddr(*pgd)
>>>> != pgd_page_vaddr(*pgd_ref));
>>>>
>>>> + if (removed) {
>>>
>>> Shouldn't this condition be "else if"?
>>
>> The first if sentence checks whether PGDs hit to BUG_ON. And the second
>> if sentence checks whether the function was called after hot-removing memory.
>> I think that the first if sentence and the second if sentence check different
>> things. So I think the condition should be "if" sentence.
>
> When the 1st if sentence is true, you have no additional operation and
> the 2nd if sentence is redundant. But I agree that the two ifs can be
> logically separated. So:
>

> Acked-by: Toshi Kani <toshi.kani@hp.com>

Thank you for your review.

Thanks,
Yasuaki Ishimatsu

>
> Thanks,
> -Toshi
>




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