linux-kernel - Re: [PATCH] Delete meaningless check of current_order in __rmqueue

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Message-ID: <CAM-Ae1O5m-qUqyX=2UBbucb3fTo6WW15DKyfVEJLRTGyDnJYPA@mail.gmail.com>
Date:	Sat, 25 Jun 2016 17:21:35 +0900
From:	Masanori YOSHIDA <masanori.yoshida.lkml@...il.com>
To:	Michal Hocko <mhocko@...nel.org>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	mgorman@...hsingularity.net, vbabka@...e.cz, rientjes@...gle.com,
	iamjoonsoo.kim@....com, izumi.taku@...fujitsu.com,
	Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org,
	YOSHIDA Masanori <masanori.yoshida@...il.com>
Subject: Re: [PATCH] Delete meaningless check of current_order in __rmqueue_fallback

On Mon, Jun 20, 2016 at 11:35 PM, Michal Hocko <mhocko@...nel.org> wrote:
> On Mon 13-06-16 03:03:31, YOSHIDA Masanori wrote:
>> From: YOSHIDA Masanori <masanori.yoshida@...il.com>
>>
>> Signed-off-by: YOSHIDA Masanori <masanori.yoshida@...il.com>
>> ---
>>  mm/page_alloc.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 6903b69..db02967 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -2105,7 +2105,7 @@ __rmqueue_fallback(struct zone *zone, unsigned int order, int start_migratetype)
>>
>>       /* 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 >= order;
>>                               --current_order) {
>>               area = &(zone->free_area[current_order]);
>>               fallback_mt = find_suitable_fallback(area, current_order,
>
> This is incorrect. Guess what happens if the given order is 0. Hint,
> current_order is unsigned int.

I see. Thank you for replying.
And I should have noticed this before submission by using git-blame. Excuse me.

> --
> Michal Hocko
> SUSE Labs