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 S1753346Ab2GPOR1 (ORCPT <rfc822;w@1wt.eu>);
	Mon, 16 Jul 2012 10:17:27 -0400
Received: from smtp101.prem.mail.ac4.yahoo.com ([76.13.13.40]:40659 "HELO
	smtp101.prem.mail.ac4.yahoo.com" rhost-flags-OK-OK-OK-OK)
	by vger.kernel.org with SMTP id S1751199Ab2GPORY (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Mon, 16 Jul 2012 10:17:24 -0400
X-Yahoo-Newman-Property: ymail-3
X-YMail-OSG: MoJ_3WoVM1mc2uCQnS_8UJ1jF_Fqm3CYwtPW3UMGwLSeLiR
 7inDebH3_M4bM3JylUvll1l88DOeWgwSHccwhh018FILxh2NDfMqGtXOUE9t
 ksps9Pc4v08evfsGi8j7heGFp7OEVSq9dWMZ7t30xlIvmGOeA11NQZampJ83
 TJBJ7qQFfDcbTPRoyPoALEgRrxcIYJgvvzXxXBtvL_vXKqQOaO1xv_8YsS8g
 mKcXCQ7cAlUI2LMtwxsB6i6vke_s1IwyIwNAdJVhW61c.W_Pi9dBbrkmw0Pq
 _XPKRHBzxNxCMFnEtk2CjMR0by8yc5U5n79nW5GuHhHAXbJYhivQHs0tbRZF
 jqTA9LL99CPhNfTxNwn9_YiQsYZPG2kPA4Wit_Xe0x6gVp5IOU0mRrZb5Avs
 2
X-Yahoo-SMTP: _Dag8S.swBC1p4FJKLCXbs8NQzyse1SYSgnAbY0-
Date: Mon, 16 Jul 2012 09:17:20 -0500 (CDT)
From: Christoph Lameter <cl@linux.com>
X-X-Sender: cl@router.home
To: David Rientjes <rientjes@google.com>
cc: Shuah Khan <shuah.khan@hp.com>, Pekka Enberg <penberg@kernel.org>,
        glommer@parallels.com, js1304@gmail.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, shuahkhan@gmail.com
Subject: Re: [PATCH TRIVIAL] mm: Fix build warning in kmem_cache_create()
In-Reply-To: <alpine.DEB.2.00.1207160257420.11472@chino.kir.corp.google.com>
Message-ID: <alpine.DEB.2.00.1207160915470.28952@router.home>
References: <1342221125.17464.8.camel@lorien2> <alpine.DEB.2.00.1207140216040.20297@chino.kir.corp.google.com> <CAOJsxLE3dDd01WaAp5UAHRb0AiXn_s43M=Gg4TgXzRji_HffEQ@mail.gmail.com> <1342407840.3190.5.camel@lorien2>
 <alpine.DEB.2.00.1207160257420.11472@chino.kir.corp.google.com>
User-Agent: Alpine 2.00 (DEB 1167 2008-08-23)
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Mon, 16 Jul 2012, David Rientjes wrote:

> On Sun, 15 Jul 2012, Shuah Khan wrote:
>
> > I can work on reshuffling the code. Do have a question though. This
> > following sanity check is currently done only when CONFIG_DEBUG_VM is
> > defined. However, it does appear to be something that is that should be
> > checked even in regular path.
> >
> > struct kmem_cache *kmem_cache_create(const char *name, size_t size,
> > size_t align,
> >                 unsigned long flags, void (*ctor)(void *))
> > {
> >         struct kmem_cache *s = NULL;
> >
> > #ifdef CONFIG_DEBUG_VM
> >         if (!name || in_interrupt() || size < sizeof(void *) ||
> >                 size > KMALLOC_MAX_SIZE) {
> >                 printk(KERN_ERR "kmem_cache_create(%s) integrity check"
> >                         " failed\n", name);
> >                 goto out;
> >         }
> > #endif
> >
>
> Agreed, this shouldn't depend on CONFIG_DEBUG_VM.

These checks are useless for regular kernel operations. They are
only useful when developing code and should only be enabled during
development. There is no point in testing the size and the name which are
typically constant when a slab is created with a stable kernel.