linux-kernel - Re: [PATCH] kernel/sysctl.c: If "count" including the terminating byte '\0' the write system call should retrun success.

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Message-ID: <20150825101507.4e3be4ca@gandalf.local.home>
Date:	Tue, 25 Aug 2015 10:15:07 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Sean Fu <fxinrong@...il.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	Ulrich Obergfell <uobergfe@...hat.com>,
	Prarit Bhargava <prarit@...hat.com>,
	Eric B Munson <emunson@...mai.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Don Zickus <dzickus@...hat.com>,
	Heinrich Schuchardt <xypron.glpk@....de>,
	David Rientjes <rientjes@...gle.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kernel/sysctl.c: If "count" including the terminating
 byte '\0' the write system call should retrun success.

On Tue, 25 Aug 2015 15:50:18 +0800
Sean Fu <fxinrong@...il.com> wrote:

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