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SubjectRe: [PATCHv5 05/28] mm: adjust FOLL_SPLIT for new refcounting
On 05/15/2015 01:36 PM, Kirill A. Shutemov wrote:
> On Fri, May 15, 2015 at 01:05:27PM +0200, Vlastimil Babka wrote:
>> On 04/23/2015 11:03 PM, Kirill A. Shutemov wrote:
>>> We need to prepare kernel to allow transhuge pages to be mapped with
>>> ptes too. We need to handle FOLL_SPLIT in follow_page_pte().
>>>
>>> Also we use split_huge_page() directly instead of split_huge_page_pmd().
>>> split_huge_page_pmd() will gone.
>>
>> You still call split_huge_page_pmd() for the is_huge_zero_page(page) case.
>
> For huge zero page we split PMD into table of zero pages and don't touch
> compound page under it. That's what split_huge_page_pmd() (renamed into
> split_huge_pmd()) will do by the end of patchset.

Ah, I see.

>> Also, of the code around split_huge_page() you basically took from
>> split_huge_page_pmd() and open-coded into follow_page_mask(), you didn't
>> include the mmu notifier calls. Why are they needed in split_huge_page_pmd()
>> but not here?
>
> We do need mmu notifier in split_huge_page_pmd() for huge zero page. When

Oh, I guess that's obvious then... to someone, anyway. Thanks.

In that case the patch seems fine.

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> we need to split compound page we go into split_huge_page() which takes
> care about mmut notifiers.
>



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