From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1755327Ab3DVUoS (ORCPT <rfc822;w@1wt.eu>);
	Mon, 22 Apr 2013 16:44:18 -0400
Received: from mail.linuxfoundation.org ([140.211.169.12]:52524 "EHLO
	mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1755287Ab3DVUoR (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Mon, 22 Apr 2013 16:44:17 -0400
Date: Mon, 22 Apr 2013 13:44:15 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: David Rientjes <rientjes@google.com>
Cc: Steven Rostedt <rostedt@goodmis.org>, Pekka Enberg <penberg@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>, linux-mm@kvack.org,
        Christoph Lameter <cl@linux.com>,
        Behan Webster <behanw@converseincode.com>
Subject: Re: [PATCH] slab: Remove unnecessary __builtin_constant_p()
Message-Id: <20130422134415.32c7f2cac07c924bff3017a4@linux-foundation.org>
In-Reply-To: <alpine.DEB.2.02.1304171702380.24494@chino.kir.corp.google.com>
References: <1366225776.8817.28.camel@pippen.local.home>
	<alpine.DEB.2.02.1304171702380.24494@chino.kir.corp.google.com>
X-Mailer: Sylpheed 3.2.0beta5 (GTK+ 2.24.10; x86_64-pc-linux-gnu)
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Wed, 17 Apr 2013 17:03:21 -0700 (PDT) David Rientjes <rientjes@google.com> wrote:

> On Wed, 17 Apr 2013, Steven Rostedt wrote:
> 
> > The slab.c code has a size check macro that checks the size of the
> > following structs:
> > 
> > struct arraycache_init
> > struct kmem_list3
> > 
> > The index_of() function that takes the sizeof() of the above two structs
> > and does an unnecessary __builtin_constant_p() on that. As sizeof() will
> > always end up being a constant making this always be true. The code is
> > not incorrect, but it just adds added complexity, and confuses users and
> > wastes the time of reviewers of the code, who spends time trying to
> > figure out why the builtin_constant_p() was used.
> > 
> > This patch is just a clean up that makes the index_of() code a little
> > bit less complex.
> > 
> > Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
> 
> Acked-by: David Rientjes <rientjes@google.com>
> 
> Adding Pekka to the cc.

I ducked this patch because it seemed rather pointless - but a little
birdie told me that there is a secret motivation which seems pretty
reasonable to me.  So I shall await chirp-the-second, which hopefully
will have a fuller and franker changelog ;)