linux-kernel - Re: [PATCH v2 4/5] mm/huge_memory.c: remove unnecessary tlb_remove_page

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Date:   Thu, 29 Apr 2021 17:02:30 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Miaohe Lin <linmiaohe@...wei.com>, akpm@...ux-foundation.org
Cc:     ziy@...dia.com, william.kucharski@...cle.com, willy@...radead.org,
        yang.shi@...ux.alibaba.com, aneesh.kumar@...ux.ibm.com,
        rcampbell@...dia.com, songliubraving@...com,
        kirill.shutemov@...ux.intel.com, riel@...riel.com,
        hannes@...xchg.org, minchan@...nel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Aaron Lu <aaron.lu@...el.com>
Subject: Re: [PATCH v2 4/5] mm/huge_memory.c: remove unnecessary
 tlb_remove_page_size() for huge zero pmd

On 29.04.21 15:26, Miaohe Lin wrote:
> Commit aa88b68c3b1d ("thp: keep huge zero page pinned until tlb flush")
> introduced tlb_remove_page() for huge zero page to keep it pinned until
> flush is complete and prevents the page from being split under us. But
> huge zero page is kept pinned until all relevant mm_users reach zero since
> the commit 6fcb52a56ff6 ("thp: reduce usage of huge zero page's atomic
> counter"). So tlb_remove_page_size() for huge zero pmd is unnecessary now.
> 
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> ---
>   mm/huge_memory.c | 3 ---
>   1 file changed, 3 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index e24a96de2e37..af30338ac49c 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1680,12 +1680,9 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
>   		if (arch_needs_pgtable_deposit())
>   			zap_deposited_table(tlb->mm, pmd);
>   		spin_unlock(ptl);
> -		if (is_huge_zero_pmd(orig_pmd))
> -			tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
>   	} else if (is_huge_zero_pmd(orig_pmd)) {
>   		zap_deposited_table(tlb->mm, pmd);
>   		spin_unlock(ptl);
> -		tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
>   	} else {
>   		struct page *page = NULL;
>   		int flush_needed = 1;
> 

This sounds sane to me

Acked-by: David Hildenbrand <david@...hat.com>

-- 
Thanks,

David / dhildenb