linux-kernel - Re: [PATCH] mm: remove a redundant condition in the for loop

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Date:   Mon, 19 Jun 2017 16:17:01 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Hao Lee <haolee.swjtu@...il.com>, akpm@...ux-foundation.org
Cc:     mgorman@...hsingularity.net, mhocko@...e.com, hannes@...xchg.org,
        iamjoonsoo.kim@....com, minchan@...nel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: remove a redundant condition in the for loop

On 06/19/2017 03:54 PM, Hao Lee wrote:
> The variable current_order decreases from MAX_ORDER-1 to order, so the
> condition current_order <= MAX_ORDER-1 is always true.
> 
> Signed-off-by: Hao Lee <haolee.swjtu@...il.com>

Sounds right.

Acked-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>  mm/page_alloc.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 2302f25..9120c2b 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2215,9 +2215,8 @@ __rmqueue_fallback(struct zone *zone, unsigned int order, int start_migratetype)
>  	bool can_steal;
>  
>  	/* Find the largest possible block of pages in the other list */
> -	for (current_order = MAX_ORDER-1;
> -				current_order >= order && current_order <= MAX_ORDER-1;
> -				--current_order) {
> +	for (current_order = MAX_ORDER-1; current_order >= order;
> +							--current_order) {
>  		area = &(zone->free_area[current_order]);
>  		fallback_mt = find_suitable_fallback(area, current_order,
>  				start_migratetype, false, &can_steal);
>