From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lb0-f169.google.com (mail-lb0-f169.google.com [209.85.217.169]) by kanga.kvack.org (Postfix) with ESMTP id 402BE6B0039 for ; Thu, 19 Dec 2013 04:42:23 -0500 (EST) Received: by mail-lb0-f169.google.com with SMTP id u14so344923lbd.14 for ; Thu, 19 Dec 2013 01:42:22 -0800 (PST) Received: from relay.parallels.com (relay.parallels.com. [195.214.232.42]) by mx.google.com with ESMTPS id h3si1339867lbd.81.2013.12.19.01.42.21 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Thu, 19 Dec 2013 01:42:21 -0800 (PST) Message-ID: <52B2BF70.7080204@parallels.com> Date: Thu, 19 Dec 2013 13:42:08 +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> <52B2B0A4.8050009@parallels.com> <52B2BBB4.3090209@parallels.com> In-Reply-To: <52B2BBB4.3090209@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 01:26 PM, 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. You are free to use the "correct" check then, but making everyone do so would be too painful ;-) linux-tip$ grep -rI '^\s*if (err)' . | wc -l 13631 linux-tip$ grep -rI '^\s*if (err\s*<\s*0)' . | wc -l 5449 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