Date: Tue, 25 Aug 2015 10:15:07 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: Sean Fu <fxinrong@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        Ulrich Obergfell <uobergfe@redhat.com>,
        Prarit Bhargava <prarit@redhat.com>,
        Eric B Munson <emunson@akamai.com>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>, Don Zickus <dzickus@redhat.com>,
        Heinrich Schuchardt <xypron.glpk@gmx.de>,
        David Rientjes <rientjes@google.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] kernel/sysctl.c: If "count" including the terminating
 byte '\0' the write system call should retrun success.
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On Tue, 25 Aug 2015 15:50:18 +0800
Sean Fu <fxinrong@gmail.com> wrote:

> On Tue, Aug 25, 2015 at 10:24 AM, Eric W. Biederman
> <ebiederm@xmission.com> wrote:
> >
> >
> > On August 24, 2015 6:57:57 PM MDT, Sean Fu <fxinrong@gmail.com> 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.


> 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?

-- Steve

> 4 Support writting "1...\0" to proc file.
> 
> >
> > Eric
> >

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