Re: [PATCH 4/4] mm/mempolicy: Use vma_alloc_folio() in new_page()

[Zi Yan <ziy@nvidia.com>]

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On 4 Apr 2022, at 15:30, Matthew Wilcox (Oracle) wrote:

> Simplify new_page() by unifying the THP and base page cases, and
> handle orders other than 0 and HPAGE_PMD_ORDER correctly.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>  mm/mempolicy.c | 25 +++++++++++--------------
>  1 file changed, 11 insertions(+), 14 deletions(-)
>
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index ec15f4f4b714..d6d7a95b0cce 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -1191,8 +1191,10 @@ int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from,
>   */
>  static struct page *new_page(struct page *page, unsigned long start)
>  {
> +	struct folio *dst, *src = page_folio(page);
>  	struct vm_area_struct *vma;
>  	unsigned long address;
> +	gfp_t gfp = GFP_HIGHUSER_MOVABLE | __GFP_RETRY_MAYFAIL;
>
>  	vma = find_vma(current->mm, start);
>  	while (vma) {
> @@ -1202,24 +1204,19 @@ static struct page *new_page(struct page *page, unsigned long start)
>  		vma = vma->vm_next;
>  	}
>
> -	if (PageHuge(page)) {
> -		return alloc_huge_page_vma(page_hstate(compound_head(page)),
> +	if (folio_test_hugetlb(src)) {
> +		return alloc_huge_page_vma(page_hstate(&src->page),
>  				vma, address);
> -	} else if (PageTransHuge(page)) {
> -		struct page *thp;
> -
> -		thp = alloc_hugepage_vma(GFP_TRANSHUGE, vma, address,
> -					 HPAGE_PMD_ORDER);
> -		if (!thp)
> -			return NULL;
> -		prep_transhuge_page(thp);
> -		return thp;
> +	} else if (folio_test_large(src)) {
> +		gfp = GFP_TRANSHUGE;
>  	}

Nit. The two bracket pairs from the two ifs can be removed.

> +
>  	/*
> -	 * if !vma, alloc_page_vma() will use task or system default policy
> +	 * if !vma, vma_alloc_folio() will use task or system default policy
>  	 */
> -	return alloc_page_vma(GFP_HIGHUSER_MOVABLE | __GFP_RETRY_MAYFAIL,
> -			vma, address);
> +	dst = vma_alloc_folio(gfp, folio_order(src), vma, address,
> +			folio_test_large(src));
> +	return &dst->page;
>  }
>  #else
>
> -- 
> 2.34.1


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Best Regards,
Yan, Zi

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