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 E45576B0069 for ; Wed, 12 Oct 2016 02:53:35 -0400 (EDT) Received: by mail-wm0-f70.google.com with SMTP id d128so3958145wmf.0 for ; Tue, 11 Oct 2016 23:53:35 -0700 (PDT) Received: from mail-wm0-f65.google.com (mail-wm0-f65.google.com. [74.125.82.65]) by mx.google.com with ESMTPS id tp11si8608850wjb.241.2016.10.11.23.53.34 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 11 Oct 2016 23:53:34 -0700 (PDT) Received: by mail-wm0-f65.google.com with SMTP id b80so886264wme.3 for ; Tue, 11 Oct 2016 23:53:34 -0700 (PDT) Date: Wed, 12 Oct 2016 08:53:32 +0200 From: Michal Hocko Subject: Re: [RFC PATCH 1/1] mm/percpu.c: fix memory leakage issue when allocate a odd alignment area Message-ID: <20161012065332.GA9504@dhcp22.suse.cz> References: <20161011172228.GA30403@dhcp22.suse.cz> <7649b844-cfe6-abce-148e-1e2236e7d443@zoho.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7649b844-cfe6-abce-148e-1e2236e7d443@zoho.com> Sender: owner-linux-mm@kvack.org List-ID: To: zijun_hu Cc: zijun_hu@htc.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, tj@kernel.org, akpm@linux-foundation.org, cl@linux.com On Wed 12-10-16 08:28:17, zijun_hu wrote: > On 2016/10/12 1:22, Michal Hocko wrote: > > On Tue 11-10-16 21:24:50, zijun_hu wrote: > >> From: zijun_hu > >> > >> the LSB of a chunk->map element is used for free/in-use flag of a area > >> and the other bits for offset, the sufficient and necessary condition of > >> this usage is that both size and alignment of a area must be even numbers > >> however, pcpu_alloc() doesn't force its @align parameter a even number > >> explicitly, so a odd @align maybe causes a series of errors, see below > >> example for concrete descriptions. > > > > Is or was there any user who would use a different than even (or power of 2) > > alighment? If not is this really worth handling? > > > > it seems only a power of 2 alignment except 1 can make sure it work very well, > that is a strict limit, maybe this more strict limit should be checked I fail to see how any other alignment would actually make any sense what so ever. Look, I am not a maintainer of this code but adding a new code to catch something that doesn't make any sense sounds dubious at best to me. I could understand this patch if you see a problem and want to prevent it from repeating bug doing these kind of changes just in case sounds like a bad idea. -- Michal Hocko SUSE Labs -- 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