From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f70.google.com (mail-wm0-f70.google.com [74.125.82.70]) by kanga.kvack.org (Postfix) with ESMTP id 075196B0292 for ; Mon, 19 Jun 2017 15:05:34 -0400 (EDT) Received: by mail-wm0-f70.google.com with SMTP id c68so12843900wmi.4 for ; Mon, 19 Jun 2017 12:05:33 -0700 (PDT) Received: from mail-wm0-x232.google.com (mail-wm0-x232.google.com. [2a00:1450:400c:c09::232]) by mx.google.com with ESMTPS id 53si5420894wru.4.2017.06.19.12.05.32 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 19 Jun 2017 12:05:32 -0700 (PDT) Received: by mail-wm0-x232.google.com with SMTP id m125so1875458wmm.1 for ; Mon, 19 Jun 2017 12:05:32 -0700 (PDT) From: Rasmus Villemoes Subject: Re: [PATCH] mm: remove a redundant condition in the for loop References: <20170619135418.8580-1-haolee.swjtu@gmail.com> Date: Mon, 19 Jun 2017 21:05:29 +0200 In-Reply-To: (Vlastimil Babka's message of "Mon, 19 Jun 2017 16:17:01 +0200") Message-ID: <87y3snajd2.fsf@rasmusvillemoes.dk> MIME-Version: 1.0 Content-Type: text/plain Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka Cc: Hao Lee , akpm@linux-foundation.org, mgorman@techsingularity.net, mhocko@suse.com, hannes@cmpxchg.org, iamjoonsoo.kim@lge.com, minchan@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org On Mon, Jun 19 2017, Vlastimil Babka wrote: > 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 > > Sounds right. > > Acked-by: Vlastimil Babka current_order and order are both unsigned, and if order==0, current_order >= order is always true, and we may decrement current_order past 0 making it UINT_MAX... A comment would be in order, though. >> --- >> 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); >> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org