From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx123.postini.com [74.125.245.123]) by kanga.kvack.org (Postfix) with SMTP id A54846B0103 for ; Mon, 11 Jun 2012 09:14:14 -0400 (EDT) Date: Mon, 11 Jun 2012 15:14:11 +0200 From: Michal Hocko Subject: Re: [PATCH -V8 12/16] hugetlb/cgroup: Add support for cgroup removal Message-ID: <20120611131411.GN12402@tiehlicka.suse.cz> References: <1339232401-14392-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1339232401-14392-13-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <20120611085258.GD12402@tiehlicka.suse.cz> <87fwa25gqj.fsf@skywalker.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87fwa25gqj.fsf@skywalker.in.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: "Aneesh Kumar K.V" Cc: linux-mm@kvack.org, kamezawa.hiroyu@jp.fujitsu.com, dhillf@gmail.com, rientjes@google.com, akpm@linux-foundation.org, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org On Mon 11-06-12 15:10:20, Aneesh Kumar K.V wrote: > Michal Hocko writes: [...] > >> +static int hugetlb_cgroup_move_parent(int idx, struct cgroup *cgroup, > >> + struct page *page) > > > > deserves a comment about the locking (needs to be called with > > hugetlb_lock). > > will do > > > > >> +{ > >> + int csize; > >> + struct res_counter *counter; > >> + struct res_counter *fail_res; > >> + struct hugetlb_cgroup *page_hcg; > >> + struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_cgroup(cgroup); > >> + struct hugetlb_cgroup *parent = parent_hugetlb_cgroup(cgroup); > >> + > >> + if (!get_page_unless_zero(page)) > >> + goto out; > >> + > >> + page_hcg = hugetlb_cgroup_from_page(page); > >> + /* > >> + * We can have pages in active list without any cgroup > >> + * ie, hugepage with less than 3 pages. We can safely > >> + * ignore those pages. > >> + */ > >> + if (!page_hcg || page_hcg != h_cg) > >> + goto err_out; > > > > How can we have page_hcg != NULL && page_hcg != h_cg? > > pages belonging to other cgroup ? OK, I've forgot that you are iterating over all active huge pages in hugetlb_cgroup_pre_destroy. What prevents you from doing the filtering in the caller? I am also wondering why you need to play with the page reference counting here. You are under hugetlb_lock so the page cannot disappear in the meantime or am I missing something? -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic -- 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