From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vladimir Davydov Subject: Re: [Devel] [PATCH 1/6] slab: cleanup kmem_cache_create_memcg() Date: Thu, 19 Dec 2013 12:39:00 +0400 Message-ID: <52B2B0A4.8050009@parallels.com> References: <6f02b2d079ffd0990ae335339c803337b13ecd8c.1387372122.git.vdavydov@parallels.com> <52B2AB7C.1010803@parallels.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <52B2AB7C.1010803-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Vasily Averin Cc: Michal Hocko , Glauber Costa , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Pekka Enberg , linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, Johannes Weiner , cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Christoph Lameter , Andrew Morton , devel-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org 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. Thanks. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lb0-f173.google.com (mail-lb0-f173.google.com [209.85.217.173]) by kanga.kvack.org (Postfix) with ESMTP id A3D246B0031 for ; Thu, 19 Dec 2013 03:39:12 -0500 (EST) Received: by mail-lb0-f173.google.com with SMTP id z5so312782lbh.18 for ; Thu, 19 Dec 2013 00:39:11 -0800 (PST) Received: from relay.parallels.com (relay.parallels.com. [195.214.232.42]) by mx.google.com with ESMTPS id ww4si1235222lbb.177.2013.12.19.00.39.11 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Thu, 19 Dec 2013 00:39:11 -0800 (PST) Message-ID: <52B2B0A4.8050009@parallels.com> Date: Thu, 19 Dec 2013 12:39:00 +0400 From: Vladimir Davydov MIME-Version: 1.0 Subject: Re: [Devel] [PATCH 1/6] slab: cleanup kmem_cache_create_memcg() References: <6f02b2d079ffd0990ae335339c803337b13ecd8c.1387372122.git.vdavydov@parallels.com> <52B2AB7C.1010803@parallels.com> In-Reply-To: <52B2AB7C.1010803@parallels.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Vasily Averin Cc: Michal Hocko , 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 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. Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752502Ab3LSIjJ (ORCPT ); Thu, 19 Dec 2013 03:39:09 -0500 Received: from relay.parallels.com ([195.214.232.42]:54630 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750807Ab3LSIjI (ORCPT ); Thu, 19 Dec 2013 03:39:08 -0500 Message-ID: <52B2B0A4.8050009@parallels.com> Date: Thu, 19 Dec 2013 12:39:00 +0400 From: Vladimir Davydov User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130922 Icedove/17.0.9 MIME-Version: 1.0 To: Vasily Averin CC: Michal Hocko , Glauber Costa , , Pekka Enberg , , Johannes Weiner , , Christoph Lameter , Andrew Morton , Subject: Re: [Devel] [PATCH 1/6] slab: cleanup kmem_cache_create_memcg() References: <6f02b2d079ffd0990ae335339c803337b13ecd8c.1387372122.git.vdavydov@parallels.com> <52B2AB7C.1010803@parallels.com> In-Reply-To: <52B2AB7C.1010803@parallels.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.30.16.96] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Thanks.