Re: [PATCH v2 06/10] mm: memory: use a folio in zap_pte_range()

Kefeng Wang
2023-11-06T15:09:02Z

On 2023/11/6 22:20, Matthew Wilcox wrote:
> On Mon, Nov 06, 2023 at 10:30:59AM +0800, Kefeng Wang wrote:
>> On 2023/11/5 1:20, Matthew Wilcox wrote:
>>>> - page_remove_rmap(page, vma, false);
>>>> - put_page(page);
>>>> + page_remove_rmap(&folio->page, vma, false);
>>>> + folio_put(folio);
>>>
>>> This is wrong. If we have a PTE-mapped THP, you'll remove the head page
>>> N times instead of removing each of N pages.
>>
>> This is device private entry, I suppose that it won't be a THP and large
>> folio when check migrate_vma_check_page() and migrate_vma_insert_page(),
>> right?
>
> I don't want to leave that kind of booby-trap in the code. Both places
> which currently call page_remove_rmap() should be left as referring to
> the page, not the folio.

Sure, I will fix this, also page_try_dup_anon_rmap() for device private
entry in copy_nonpresent_pte of patch5.