Re: [PATCH] mm/page_alloc: simplify page_is_buddy() for better code readability

[Baoquan He <bhe@redhat.com>]

On 03/08/20 at 04:10pm, qiwuchen55@gmail.com wrote:
> From: chenqiwu <chenqiwu@xiaomi.com>
> 
> Simplify page_is_buddy() to reduce the redundant code for better
> code readability.
> 
> Signed-off-by: chenqiwu <chenqiwu@xiaomi.com>
> ---
>  mm/page_alloc.c | 13 +++----------
>  1 file changed, 3 insertions(+), 10 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 79e950d..c6eef38 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -797,16 +797,8 @@ static inline void set_page_order(struct page *page, unsigned int order)
>  static inline int page_is_buddy(struct page *page, struct page *buddy,
>  							unsigned int order)
>  {
> -	if (page_is_guard(buddy) && page_order(buddy) == order) {
> -		if (page_zone_id(page) != page_zone_id(buddy))
> -			return 0;
> -
> -		VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy);
> -
> -		return 1;
> -	}
This duplicated removing Looks good, not sure if there's any performance
impact or other considering.

FWIW,
Reviewed-by: Baoquan He <bhe@redhat.com>

> -
> -	if (PageBuddy(buddy) && page_order(buddy) == order) {
> +	if ((page_is_guard(buddy) || PageBuddy(buddy))
> +	     && page_order(buddy) == order) {


>  		/*
>  		 * zone check is done late to avoid uselessly
>  		 * calculating zone/node ids for pages that could
> @@ -819,6 +811,7 @@ static inline int page_is_buddy(struct page *page, struct page *buddy,
>  
>  		return 1;
>  	}
> +
>  	return 0;
>  }
>  
> -- 
> 1.9.1
> 
>