linux-kernel - Re: [PATCH v2] mm/damon: Remove redundant page validation

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Message-ID: <3db0e468-8713-b87b-1579-b79481e2c110@huawei.com>
Date:   Tue, 25 Jan 2022 11:43:33 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Baolin Wang <baolin.wang@...ux.alibaba.com>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <sj@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2] mm/damon: Remove redundant page validation

On 2022/1/17 10:34, Baolin Wang wrote:
> It will never get a NULL page by pte_page() as discussed in thread [1],
> thus remove the redundant page validation to fix below Smatch static
> checker warning.
> 
>     mm/damon/vaddr.c:405 damon_hugetlb_mkold()
>     warn: 'page' can't be NULL.
> 
> [1] https://lore.kernel.org/linux-mm/20220106091200.GA14564@kili/
> 
> Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> Reviewed-by: SeongJae Park <sj@...nel.org>

LGTM. Thanks.

Reviewed-by: Miaohe Lin <linmiaohe@...wei.com>

> ---
> Changes from v1:
>  - Improve the commit message suggested by SeongJae.
>  - Add reviewed-by tag from SeongJae.
> ---
>  mm/damon/vaddr.c | 6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
> index 89b6468d..8a52e00 100644
> --- a/mm/damon/vaddr.c
> +++ b/mm/damon/vaddr.c
> @@ -402,9 +402,6 @@ static void damon_hugetlb_mkold(pte_t *pte, struct mm_struct *mm,
>  	pte_t entry = huge_ptep_get(pte);
>  	struct page *page = pte_page(entry);
>  
> -	if (!page)
> -		return;
> -
>  	get_page(page);
>  
>  	if (pte_young(entry)) {
> @@ -564,9 +561,6 @@ static int damon_young_hugetlb_entry(pte_t *pte, unsigned long hmask,
>  		goto out;
>  
>  	page = pte_page(entry);
> -	if (!page)
> -		goto out;
> -
>  	get_page(page);
>  
>  	if (pte_young(entry) || !page_is_idle(page) ||
>