From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756553Ab1AaWmV (ORCPT ); Mon, 31 Jan 2011 17:42:21 -0500 Received: from smtp1.linux-foundation.org ([140.211.169.13]:53704 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754328Ab1AaWmU (ORCPT ); Mon, 31 Jan 2011 17:42:20 -0500 Date: Mon, 31 Jan 2011 14:41:31 -0800 From: Andrew Morton To: Johannes Weiner Cc: kamezawa.hiroyu@jp.fujitsu.com, nishimura@mxp.nes.nec.co.jp, balbir@linux.vnet.ibm.com, minchan.kim@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [patch 2/3] memcg: prevent endless loop when charging huge pages to near-limit group Message-Id: <20110131144131.6733aa3a.akpm@linux-foundation.org> In-Reply-To: <1296482635-13421-3-git-send-email-hannes@cmpxchg.org> References: <1296482635-13421-1-git-send-email-hannes@cmpxchg.org> <1296482635-13421-3-git-send-email-hannes@cmpxchg.org> X-Mailer: Sylpheed 3.0.2 (GTK+ 2.20.1; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 31 Jan 2011 15:03:54 +0100 Johannes Weiner wrote: > +static inline bool res_counter_check_margin(struct res_counter *cnt, > + unsigned long bytes) > +{ > + bool ret; > + unsigned long flags; > + > + spin_lock_irqsave(&cnt->lock, flags); > + ret = cnt->limit - cnt->usage >= bytes; > + spin_unlock_irqrestore(&cnt->lock, flags); > + return ret; > +} > + > static inline bool res_counter_check_under_soft_limit(struct res_counter *cnt) > { > bool ret; > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 73ea323..c28072f 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -1111,6 +1111,15 @@ static bool mem_cgroup_check_under_limit(struct mem_cgroup *mem) > return false; > } > > +static bool mem_cgroup_check_margin(struct mem_cgroup *mem, unsigned long bytes) > +{ > + if (!res_counter_check_margin(&mem->res, bytes)) > + return false; > + if (do_swap_account && !res_counter_check_margin(&mem->memsw, bytes)) > + return false; > + return true; > +} argh. If you ever have a function with the string "check" in its name, it's a good sign that you did something wrong. Check what? Against what? Returning what? mem_cgroup_check_under_limit() isn't toooo bad - the name tells you what's being checked and tells you what to expect the return value to mean. But "res_counter_check_margin" and "mem_cgroup_check_margin" are just awful. Something like bool res_counter_may_charge(counter, bytes) would be much clearer. If we really want to stick with the "check" names (perhaps as an ironic reference to res_counter's past mistakes) then please at least document the sorry things?