From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 3 Aug 2016 17:31:17 +0300 From: Vladimir Davydov To: Johannes Weiner CC: Michal Hocko , Andrew Morton , , , Subject: Re: [PATCH v2 1/3] mm: memcontrol: fix swap counter leak on swapout from offline cgroup Message-ID: <20160803143117.GK13263@esperanza> References: <20160802160025.GB28900@dhcp22.suse.cz> <20160803095049.GG13263@esperanza> <20160803110941.GA19196@dhcp22.suse.cz> <20160803114639.GI13263@esperanza> <20160803141203.GA12838@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20160803141203.GA12838@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-ID: On Wed, Aug 03, 2016 at 10:12:03AM -0400, Johannes Weiner wrote: > On Wed, Aug 03, 2016 at 02:46:40PM +0300, Vladimir Davydov wrote: ... > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index 1c0aa59fd333..8c8e68becee9 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -4044,7 +4044,7 @@ static struct mem_cgroup *mem_cgroup_id_get_online(struct mem_cgroup *memcg) > > * The root cgroup cannot be destroyed, so it's refcount must > > * always be >= 1. > > */ > > - if (memcg == root_mem_cgroup) { > > + if (WARN_ON_ONCE(memcg == root_mem_cgroup)) { > > VM_BUG_ON(1); > > break; > > } > > The WARN_ON_ONCE() makes sense to me. But if we warn on all configs > anyway, the VM_BUG_ON() doesn't provide any additional value. Anybody > who is testing new code and enables DEBUG_VM should notice a warning > without requiring the kernel to blow up in their face; it also allows > them to check other state that is not necessarily available in BUG(). Personally, I prefer to crash the kernel as early as possible when debugging to get vmcore for further investigation. Judging by mem_cgroup_update_lru_size(), I'm not alone. -- 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