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SubjectRe: [PATCH 2/2] x86,mem-hotplug: modify PGD entry when removing memory
(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.

Thanks,
Yasuaki Ishimatsu

>
> Thanks,
> -Toshi
>
>> + if (pgd_none(*pgd_ref) && !pgd_none(*pgd))
>> + pgd_clear(pgd);
>> + } else {
>> + if (pgd_none(*pgd))
>> + set_pgd(pgd, *pgd_ref);
>> + }
>> +
>> spin_unlock(pgt_lock);
>> }
>
>




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