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Date:   Thu, 18 Aug 2022 09:15:22 +0800
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Subject: Re: [PATCH 4/6] mm: hugetlb_vmemmap: add missing smp_wmb() before
 set_pte_at()
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To:     Miaohe Lin <linmiaohe@huawei.com>, <akpm@linux-foundation.org>,
        <mike.kravetz@oracle.com>, <songmuchun@bytedance.com>
CC:     <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>
References: <20220816130553.31406-1-linmiaohe@huawei.com>
 <20220816130553.31406-5-linmiaohe@huawei.com>
From:   "Yin, Fengwei" <fengwei.yin@intel.com>
In-Reply-To: <20220816130553.31406-5-linmiaohe@huawei.com>
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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@huawei.com>
Reviewed-by: Yin Fengwei <fengwei.yin@intel.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));
>  }
>