linux-kernel - Re: [PATCH] proc: move the adding option Ngid to the end of proc/PID/status

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Date:	Thu, 23 Apr 2015 23:32:26 +0300
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	xiaoming.wang@...el.com,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Mel Gorman <mgorman@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] proc: move the adding option Ngid to the end of
 proc/PID/status

On Tue, Apr 21, 2015 at 11:11:19AM -0400, Tejun Heo wrote:
> On Tue, Apr 21, 2015 at 05:00:07PM +0300, Alexey Dobriyan wrote:
> > > The only reason for changing the position is because
> > > there's this specific breakage.  The goal should be working around
> > > that specific case while keeping the impact minimum on everyone else.
> > 
> > If there are TWO incorrect parsers, one for TracerPid, another for Ngid,
> > you CAN'T workaround it. And if you can't workaround you choose code
> > which was written first, namely, TracerPid one.
> 
> Not when the code has been out for 1.5 years.  Minimizing the
> disturbance is the better course of action.  Look at the file.  If you
> move ngid to the end now, it's gonna shift most of the file content,
> which is what caused the problem in the first place.
> 
> We don't know what's out there which again was the same problem which
> triggered this thread in the first place.  Why would you take the same
> amount of risk when you can fix the known issue with less amount of
> changes?

There are 2 fields before Ngid and 35+ after Ngid. So the risk is not
the same. Potentionally, Ngid addition broke almost every parser.

> Just put ngid after tracerpid.  That way, we can fix the
> known problems while changing the offsets of only four fields.  At
> this point, no change to the file layout is "right".  Such thing isn't
> defined regardless of who came first.  The only thing we can do is
> working around the known cases while minimizing possible impacts.

We'll return to this thread when next breakage will be reported,
I promise. :^)
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