Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755664AbbHYQot (ORCPT ); Tue, 25 Aug 2015 12:44:49 -0400 Received: from mail-ig0-f196.google.com ([209.85.213.196]:35585 "EHLO mail-ig0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754183AbbHYQor (ORCPT ); Tue, 25 Aug 2015 12:44:47 -0400 MIME-Version: 1.0 In-Reply-To: <20150825101507.4e3be4ca@gandalf.local.home> References: <20150824125902.4ba11ec6@gandalf.local.home> <9CF68C3D-499C-4AFC-B890-BA5ECA284347@xmission.com> <20150825101507.4e3be4ca@gandalf.local.home> Date: Wed, 26 Aug 2015 00:44:46 +0800 Message-ID: Subject: Re: [PATCH] kernel/sysctl.c: If "count" including the terminating byte '\0' the write system call should retrun success. From: Sean Fu To: Steven Rostedt Cc: "Eric W. Biederman" , Andrey Ryabinin , Ulrich Obergfell , Prarit Bhargava , Eric B Munson , "Paul E. McKenney" , Johannes Weiner , Andrew Morton , Thomas Gleixner , Don Zickus , Heinrich Schuchardt , David Rientjes , linux-kernel@vger.kernel.org Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2524 Lines: 63 On Tue, Aug 25, 2015 at 10:15 PM, Steven Rostedt wrote: > On Tue, 25 Aug 2015 15:50:18 +0800 > Sean Fu wrote: > >> On Tue, Aug 25, 2015 at 10:24 AM, Eric W. Biederman >> wrote: >> > >> > >> > On August 24, 2015 6:57:57 PM MDT, Sean Fu wrote: >> >>An application from HuaWei which works fine on 2.6 encounters this >> >>issue on 3.0 or later kernel. >> > >> > My sympathies. Being stuck with a 3rd party application you can barely talk about that has been broken for 5years and no one reported it. >> > >> > Ordinarily we would fix a regression like this. As it has been 5years the challenge now is how do we tell if there are applications that depend on the current behavior. >> > >> > Before we can change the behavior back we need a convincing argument that we won't cause a regression in another application by making the change. >> > >> > I do not see how such an argument can be made. So you have my sympathies but I do not see how we can help you. >> We should consider this patch basing on my following arguments. >> 1 Different version kernel should keep consistent on this behavior. > > The thing is, the above argument is against the patch. The behavior > changed 2 years ago, and nobody noticed. Changing it back only causes > more inconsistent behavior. It is impossible to cause more inconsistent behavior. it just enhance compatibility(support "xx...x\0"). This patch just modify "proc_wspace_sep" array. and "proc_wspace_sep" is static. Only "proc_get_long" used this array, "proc_get_long" is also static. There are only 4 place to call "proc_get_long" in kernel/sysctl.c. I will prove that these 4 callers have no bad impact later. > > >> 2 This writting behavior on proc file should be same with writting on >> regular file as possible as we can. > > Writing to a proc file causes kernel actions. Writing to a regular file > just saves data. That's not an argument here. > >> 3 This patch does not have any potential compatibility risk with 3rd >> party application. > > How do you know that? I will prove that all other write usage is not impacted later. Thanks for all reply. Sean > > -- Steve > >> 4 Support writting "1...\0" to proc file. >> >> > >> > Eric >> > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/