From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753191Ab3LSJpe (ORCPT ); Thu, 19 Dec 2013 04:45:34 -0500 Received: from cantor2.suse.de ([195.135.220.15]:46436 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752897Ab3LSJp2 (ORCPT ); Thu, 19 Dec 2013 04:45:28 -0500 Date: Thu, 19 Dec 2013 10:45:27 +0100 From: Michal Hocko To: Vasily Averin Cc: Vladimir Davydov , Glauber Costa , linux-kernel@vger.kernel.org, Pekka Enberg , linux-mm@kvack.org, Johannes Weiner , cgroups@vger.kernel.org, Christoph Lameter , Andrew Morton , devel@openvz.org Subject: Re: [Devel] [PATCH 1/6] slab: cleanup kmem_cache_create_memcg() Message-ID: <20131219094527.GC10855@dhcp22.suse.cz> References: <6f02b2d079ffd0990ae335339c803337b13ecd8c.1387372122.git.vdavydov@parallels.com> <52B2AB7C.1010803@parallels.com> <52B2B0A4.8050009@parallels.com> <52B2BBB4.3090209@parallels.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <52B2BBB4.3090209@parallels.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 19-12-13 13:26:12, Vasily Averin wrote: > On 12/19/2013 12:39 PM, Vladimir Davydov wrote: > > On 12/19/2013 12:17 PM, Vasily Averin wrote: > >> On 12/18/2013 05:16 PM, Vladimir Davydov wrote: > >>> --- a/mm/slab_common.c > >>> +++ b/mm/slab_common.c > >>> @@ -176,8 +176,9 @@ kmem_cache_create_memcg(struct mem_cgroup *memcg, const char *name, size_t size, > >>> get_online_cpus(); > >>> mutex_lock(&slab_mutex); > >>> > >>> - if (!kmem_cache_sanity_check(memcg, name, size) == 0) > >>> - goto out_locked; > >>> + err = kmem_cache_sanity_check(memcg, name, size); > >>> + if (err) > >>> + goto out_unlock; > >>> > >>> /* > >>> * Some allocators will constraint the set of valid flags to a subset > >> Theoretically in future kmem_cache_sanity_check() can return positive value. > >> Probably it's better to check (err < 0) in caller ? > > > > Hmm, why? What information could positive retval carry here? We have > > plenty of places throughout the code where we check for (err), not > > (err<0), simply because it looks clearer, e.g. look at > > __kmem_cache_create() calls. If it returns a positive value one day, we > > will have to parse every place where it's called. Anyway, if someone > > wants to change a function behavior, he must check every place where > > this function is called and fix them accordingly. > > I believe expected semantic of function -- return negative in case of error. > So correct error cheek should be (err < 0). > (err) check is semantically incorrect, and it can lead to troubles in future. No, this function returns -ERRNO or 0 on success. -- Michal Hocko SUSE Labs