Re: [PATCH] mm: get rid of odd jump label in find_mergeable_anon_vma

[David Hildenbrand]

On 15.11.19 07:36, linmiaohe wrote:
> From: Miaohe Lin <linmiaohe@xxxxxxxxxx>

I'm pro removing unnecessary jump labels.

Subject: "mm: get rid of jump labels in find_mergeable_anon_vma()"

> 
> The odd jump label try_prev and none is not really need

s/odd jump label/jump labels/

s/is/are/

> in func find_mergeable_anon_vma, eliminate them to
> improve readability.
> 
> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> ---
>  mm/mmap.c | 18 +++++++-----------
>  1 file changed, 7 insertions(+), 11 deletions(-)
> 
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 4d4db76a07da..ab980d468a10 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1276,25 +1276,21 @@ static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, struct vm_
>   */
>  struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
>  {
> -	struct anon_vma *anon_vma;
> +	struct anon_vma *anon_vma = NULL;
>  	struct vm_area_struct *near;
>  
>  	near = vma->vm_next;
> -	if (!near)
> -		goto try_prev;
> -
> -	anon_vma = reusable_anon_vma(near, vma, near);
> +	if (near)
> +		anon_vma = reusable_anon_vma(near, vma, near);>  	if (anon_vma)
>  		return anon_vma;

Let me suggest the following instead:

/* Try next first */
near = vma->vm_next;
if (near) {
	anon_vma = reusable_anon_vma(near, vma, near);
	if (anon_vma)
		return anon_vma;
}
/* Try prev next */
near = vma->vm_prev;
if (near) {
	anon_vma = reusable_anon_vma(near, vma, near);
	if (anon_vma)
		return anon_vma;
}

> -try_prev:
> -	near = vma->vm_prev;
> -	if (!near)
> -		goto none;
>  
> -	anon_vma = reusable_anon_vma(near, near, vma);
> +	near = vma->vm_prev;
> +	if (near)
> +		anon_vma = reusable_anon_vma(near, near, vma);
>  	if (anon_vma)
>  		return anon_vma;
> -none:
> +
>  	/*
>  	 * There's no absolute need to look only at touching neighbours:
>  	 * we could search further afield for "compatible" anon_vmas.
> 


-- 

Thanks,

David / dhildenb