linux-kernel - Re: [PATCH v3 9/9] mm/page_isolation: clean up confused code

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Date:	Fri, 17 Jun 2016 15:34:12 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	js1304@...il.com, Andrew Morton <akpm@...ux-foundation.org>
Cc:	mgorman@...hsingularity.net, Minchan Kim <minchan@...nel.org>,
	Alexander Potapenko <glider@...gle.com>,
	Hugh Dickins <hughd@...gle.com>,
	Michal Hocko <mhocko@...nel.org>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Sasha Levin <sasha.levin@...cle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH v3 9/9] mm/page_isolation: clean up confused code

On 06/17/2016 09:57 AM, js1304@...il.com wrote:
> From: Joonsoo Kim <iamjoonsoo.kim@....com>
>
> When there is an isolated_page, post_alloc_hook() is called with
> page but __free_pages() is called with isolated_page. Since they are
> the same so no problem but it's very confusing. To reduce it,
> this patch changes isolated_page to boolean type and uses page variable
> consistently.
>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>

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

Could be also just folded to mm/page_owner: initialize page owner without 
holding the zone lock

> ---
>  mm/page_isolation.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index 4639163..064b7fb 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -81,7 +81,7 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
>  {
>  	struct zone *zone;
>  	unsigned long flags, nr_pages;
> -	struct page *isolated_page = NULL;
> +	bool isolated_page = false;
>  	unsigned int order;
>  	unsigned long page_idx, buddy_idx;
>  	struct page *buddy;
> @@ -109,7 +109,7 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
>  			if (pfn_valid_within(page_to_pfn(buddy)) &&
>  			    !is_migrate_isolate_page(buddy)) {
>  				__isolate_free_page(page, order);
> -				isolated_page = page;
> +				isolated_page = true;
>  			}
>  		}
>  	}
> @@ -129,7 +129,7 @@ out:
>  	spin_unlock_irqrestore(&zone->lock, flags);
>  	if (isolated_page) {
>  		post_alloc_hook(page, order, __GFP_MOVABLE);
> -		__free_pages(isolated_page, order);
> +		__free_pages(page, order);
>  	}
>  }
>
>