Re: [PATCH 4/6] mm: hugetlb_vmemmap: add missing smp_wmb() before set_pte_at()

[Yin, Fengwei]

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@xxxxxxxxxx>
Reviewed-by: Yin Fengwei <fengwei.yin@xxxxxxxxx>

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));
>  }
>