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

[Muchun Song <muchun.song@linux.dev>]

> On Aug 16, 2022, at 21:05, Miaohe Lin <linmiaohe@huawei.com> 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.

I found another place where is a similar case. See kasan_populate_vmalloc_pte() in
mm/kasan/shadow.c. 

Should we fix it as well?


> 
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
> ---
> 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));
> }
> 
> -- 
> 2.23.0
> 
>