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Date:   Fri, 2 Jun 2023 09:44:00 -0700
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Subject: Re: [PATCH 1/2] mm/hugetlb: Use a folio in copy_hugetlb_page_range()
To:     Peng Zhang <zhangpeng362@huawei.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
        willy@infradead.org, mike.kravetz@oracle.com
Cc:     muchun.song@linux.dev, vishal.moola@gmail.com,
        wangkefeng.wang@huawei.com, sunnanyong@huawei.com
References: <20230602015408.376149-1-zhangpeng362@huawei.com>
 <20230602015408.376149-2-zhangpeng362@huawei.com>
Content-Language: en-US
From:   Sidhartha Kumar <sidhartha.kumar@oracle.com>
In-Reply-To: <20230602015408.376149-2-zhangpeng362@huawei.com>
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On 6/1/23 6:54 PM, Peng Zhang wrote:
> From: ZhangPeng <zhangpeng362@huawei.com>
> 
> We can replace five implict calls to compound_head() with one by using
> pte_folio. However, we still need to keep ptepage because we need to know
> which page in the folio we are copying.
> 
> Suggested-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> Signed-off-by: ZhangPeng <zhangpeng362@huawei.com>
> ---
>   mm/hugetlb.c | 14 ++++++++------
>   1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index ea24718db4af..0b774dd3d57b 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -5017,6 +5017,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
>   {
>   	pte_t *src_pte, *dst_pte, entry;
>   	struct page *ptepage;
> +	struct folio *pte_folio;
>   	unsigned long addr;
>   	bool cow = is_cow_mapping(src_vma->vm_flags);
>   	struct hstate *h = hstate_vma(src_vma);
> @@ -5116,7 +5117,8 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
>   		} else {
>   			entry = huge_ptep_get(src_pte);
>   			ptepage = pte_page(entry);
> -			get_page(ptepage);
> +			pte_folio = page_folio(ptepage);
> +			folio_get(pte_folio);
>   
>   			/*
>   			 * Failing to duplicate the anon rmap is a rare case
> @@ -5128,7 +5130,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
>   			 * need to be without the pgtable locks since we could
>   			 * sleep during the process.
>   			 */
> -			if (!PageAnon(ptepage)) {
> +			if (!folio_test_anon(pte_folio)) {
>   				page_dup_file_rmap(ptepage, true);
>   			} else if (page_try_dup_anon_rmap(ptepage, true,
>   							  src_vma)) {
> @@ -5140,14 +5142,14 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
>   				/* Do not use reserve as it's private owned */
>   				new_folio = alloc_hugetlb_folio(dst_vma, addr, 1);
>   				if (IS_ERR(new_folio)) {
> -					put_page(ptepage);
> +					folio_put(pte_folio);
>   					ret = PTR_ERR(new_folio);
>   					break;
>   				}
>   				ret = copy_user_large_folio(new_folio,
> -						      page_folio(ptepage),
> -						      addr, dst_vma);
> -				put_page(ptepage);
> +							    pte_folio,
> +							    addr, dst_vma);
> +				folio_put(pte_folio);
>   				if (ret) {
>   					folio_put(new_folio);
>   					break;

Reviewed-by Sidhartha Kumar <sidhartha.kumar@oracle.com>