linux-kernel - Re: [PATCH] mm: userfaultfd: Use swap() in double_pt

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Date: Fri, 31 May 2024 12:02:12 +0200
From: David Hildenbrand <david@...hat.com>
To: Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>, akpm@...ux-foundation.org
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
 Abaci Robot <abaci@...ux.alibaba.com>
Subject: Re: [PATCH] mm: userfaultfd: Use swap() in double_pt_lock()

On 31.05.24 11:16, Jiapeng Chong wrote:
> Use existing swap() function rather than duplicating its implementation.
> 
> ./mm/userfaultfd.c:1006:13-14: WARNING opportunity for swap()
> 
> Reported-by: Abaci Robot <abaci@...ux.alibaba.com>
> Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=9266
> Signed-off-by: Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>
> ---
>   mm/userfaultfd.c | 10 ++--------
>   1 file changed, 2 insertions(+), 8 deletions(-)
> 
> diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
> index defa5109cc62..5e7f2801698a 100644
> --- a/mm/userfaultfd.c
> +++ b/mm/userfaultfd.c
> @@ -995,14 +995,8 @@ void double_pt_lock(spinlock_t *ptl1,
>   	__acquires(ptl1)
>   	__acquires(ptl2)
>   {
> -	spinlock_t *ptl_tmp;
> -
> -	if (ptl1 > ptl2) {
> -		/* exchange ptl1 and ptl2 */
> -		ptl_tmp = ptl1;
> -		ptl1 = ptl2;
> -		ptl2 = ptl_tmp;
> -	}
> +	if (ptl1 > ptl2)
> +		swap(ptl1, ptl2);
>   	/* lock in virtual address order to avoid lock inversion */
>   	spin_lock(ptl1);
>   	if (ptl1 != ptl2)

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 
Cheers,

David / dhildenb