From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f173.google.com (mail-wi0-f173.google.com [209.85.212.173]) by kanga.kvack.org (Postfix) with ESMTP id DD09582F64 for ; Tue, 27 Oct 2015 12:23:54 -0400 (EDT) Received: by wicll6 with SMTP id ll6so167399355wic.0 for ; Tue, 27 Oct 2015 09:23:54 -0700 (PDT) Received: from gum.cmpxchg.org (gum.cmpxchg.org. [85.214.110.215]) by mx.google.com with ESMTPS id z19si31010840wij.114.2015.10.27.09.23.53 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 27 Oct 2015 09:23:53 -0700 (PDT) Date: Tue, 27 Oct 2015 09:23:31 -0700 From: Johannes Weiner Subject: Re: [PATCH] memcg: Fix thresholds for 32b architectures. Message-ID: <20151027162331.GA7749@cmpxchg.org> References: <1445942234-11175-1-git-send-email-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1445942234-11175-1-git-send-email-mhocko@kernel.org> Sender: owner-linux-mm@kvack.org List-ID: To: mhocko@kernel.org Cc: Andrew Morton , Shaohua Li , Ben Hutchings , Vladimir Davydov , linux-mm@kvack.org, LKML , Michal Hocko , stable@vger.kernel.org On Tue, Oct 27, 2015 at 11:37:14AM +0100, mhocko@kernel.org wrote: > From: Michal Hocko > > 424cdc141380 ("memcg: convert threshold to bytes") has fixed a > regression introduced by 3e32cb2e0a12 ("mm: memcontrol: lockless page > counters") where thresholds were silently converted to use page units > rather than bytes when interpreting the user input. > > The fix is not complete, though, as properly pointed out by Ben > Hutchings during stable backport review. The page count is converted > to bytes but unsigned long is used to hold the value which would > be obviously not sufficient for 32b systems with more than 4G > thresholds. The same applies to usage as taken from mem_cgroup_usage > which might overflow. > > Let's remove this bytes vs. pages internal tracking differences and > handle thresholds in page units internally. Chage mem_cgroup_usage() > to return the value in page units and revert 424cdc141380 because this > should be sufficient for the consistent handling. > mem_cgroup_read_u64 as the only users of mem_cgroup_usage outside of > the threshold handling code is converted to give the proper in bytes > result. It is doing that already for page_counter output so this is > more consistent as well. > > The value presented to the userspace is still in bytes units. > > Fixes: 424cdc141380 ("memcg: convert threshold to bytes") > Fixes: 3e32cb2e0a12 ("mm: memcontrol: lockless page counters") > CC: stable@vger.kernel.org > Reported-by: Ben Hutchings > Signed-off-by: Michal Hocko Acked-by: Johannes Weiner > +++ b/mm/memcontrol.c > @@ -2802,7 +2802,7 @@ static unsigned long tree_stat(struct mem_cgroup *memcg, > return val; > } > > -static inline u64 mem_cgroup_usage(struct mem_cgroup *memcg, bool swap) > +static inline unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap) > { > u64 val; Minor nit, but this should probably be unsigned long now. -- 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