linux-kernel - Re: [PATCH] slab: Remove unnecessary __builtin_constant

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Message-Id: <20130422134415.32c7f2cac07c924bff3017a4@linux-foundation.org>
Date:	Mon, 22 Apr 2013 13:44:15 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Pekka Enberg <penberg@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
	Christoph Lameter <cl@...ux.com>,
	Behan Webster <behanw@...verseincode.com>
Subject: Re: [PATCH] slab: Remove unnecessary __builtin_constant_p()

On Wed, 17 Apr 2013 17:03:21 -0700 (PDT) David Rientjes <rientjes@...gle.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@...dmis.org>
> 
> Acked-by: David Rientjes <rientjes@...gle.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 ;)

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