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SubjectRe: [PATCH 08/10] hugetlb: remove unneeded SetHPageVmemmapOptimized()
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> On Aug 27, 2022, at 10:18, Miaohe Lin <linmiaohe@huawei.com> wrote:
>
> On 2022/8/27 9:35, Muchun Song wrote:
>>
>>
>>> On Aug 26, 2022, at 17:24, Miaohe Lin <linmiaohe@huawei.com> wrote:
>>>
>>> If code reaches here, it's guaranteed that HPageVmemmapOptimized is set
>>> for the hugetlb page (or VM_BUG_ON_PAGE() will complain about it). It's
>>
>> Hi Miaohe,
>>
>> Right.
>>
>>> unnecessary to set it again.
>>
>> No, I suppose you didn’t test this patch since it does not work. The
>> HPageVmemmapOptimized is cleared in the above code of line
>> (set_page_private(page, 0)). So NAck.
>
> Sorry, I missed that and thanks for pointing this out. Does this code deserves a
> comment like below?
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index d0617d64d718..3374c1d2b52e 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1522,6 +1522,10 @@ static void add_hugetlb_page(struct hstate *h, struct page *page,
>
> set_compound_page_dtor(page, HUGETLB_PAGE_DTOR);
> set_page_private(page, 0);
> + /*
> + * We have to set HPageVmemmapOptimized again as above
> + * set_page_private(page, 0) cleared it.
> + */
> SetHPageVmemmapOptimized(page);

I’m fine with this comment.

Reviewed-by: Muchun Song <songmuchun@bytedance.com>


>
> /*
>
>
> Thanks,
> Miaohe Lin

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