linux-kernel - Re: [PATCH 4/6] mm: hugetlb_vmemmap: add missing smp_wmb() before set_pte

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Message-ID: <70ea9b8d-c1e1-5ab5-f001-7a81814dd8db@intel.com>
Date:   Thu, 18 Aug 2022 09:15:22 +0800
From:   "Yin, Fengwei" <fengwei.yin@...el.com>
To:     Miaohe Lin <linmiaohe@...wei.com>, <akpm@...ux-foundation.org>,
        <mike.kravetz@...cle.com>, <songmuchun@...edance.com>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/6] mm: hugetlb_vmemmap: add missing smp_wmb() before
 set_pte_at()



On 8/16/2022 9:05 PM, Miaohe Lin wrote:
> The memory barrier smp_wmb() is needed to make sure that preceding stores
> to the page contents become visible before the below set_pte_at() write.
> 
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
Reviewed-by: Yin Fengwei <fengwei.yin@...el.com>

Regards
Yin, Fengwei

> ---
>  mm/hugetlb_vmemmap.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
> index 20f414c0379f..76b2d03a0d8d 100644
> --- a/mm/hugetlb_vmemmap.c
> +++ b/mm/hugetlb_vmemmap.c
> @@ -287,6 +287,11 @@ static void vmemmap_restore_pte(pte_t *pte, unsigned long addr,
>  	copy_page(to, (void *)walk->reuse_addr);
>  	reset_struct_pages(to);
>  
> +	/*
> +	 * Makes sure that preceding stores to the page contents become visible
> +	 * before the set_pte_at() write.
> +	 */
> +	smp_wmb();
>  	set_pte_at(&init_mm, addr, pte, mk_pte(page, pgprot));
>  }
>