Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935229Ab3DHQdu (ORCPT ); Mon, 8 Apr 2013 12:33:50 -0400 Received: from cantor2.suse.de ([195.135.220.15]:39731 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1763333Ab3DHQds (ORCPT ); Mon, 8 Apr 2013 12:33:48 -0400 Date: Mon, 8 Apr 2013 18:33:44 +0200 From: Michal Hocko To: Tejun Heo Cc: Li Zefan , Andrew Morton , Glauber Costa , KAMEZAWA Hiroyuki , Johannes Weiner , LKML , Cgroups , linux-mm@kvack.org Subject: Re: [PATCH 1/8] cgroup: implement cgroup_is_ancestor() Message-ID: <20130408163344.GP17178@dhcp22.suse.cz> References: <51627DA9.7020507@huawei.com> <51627DBB.5050005@huawei.com> <20130408144750.GK17178@dhcp22.suse.cz> <20130408155726.GG3021@htj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130408155726.GG3021@htj.dyndns.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2216 Lines: 69 On Mon 08-04-13 08:57:26, Tejun Heo wrote: > Hello, > > On Mon, Apr 08, 2013 at 04:47:50PM +0200, Michal Hocko wrote: > > On Mon 08-04-13 16:20:11, Li Zefan wrote: > > [...] > > > @@ -5299,6 +5300,26 @@ struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id) > > > return css ? css : ERR_PTR(-ENOENT); > > > } > > > > > > +/** > > > + * cgroup_is_ancestor - test "root" cgroup is an ancestor of "child" > > > + * @child: the cgroup to be tested. > > > + * @root: the cgroup supposed to be an ancestor of the child. > > > + * > > > + * Returns true if "root" is an ancestor of "child" in its hierarchy. > > > + */ > > > +bool cgroup_is_ancestor(struct cgroup *child, struct cgroup *root) > > > +{ > > > + int depth = child->depth; > > > > Is this functionality helpful for other controllers but memcg? > > css_is_ancestor is currently used only by memcg code AFAICS and we can > > get the same functionality easily by using something like: > > It's a basic hierarchy operation. Which nobody seem to need ATM so it could be added later when an user emerges. > I'd prefer it to be in cgroup and in general let's try to avoid > memcg-specific infrastructure. Now that I am thinking about that some more css_is_ancestor is even not correct. Consider this for example root \ A (use_hierarchy = 0) \ B (use_hierarchy = 1) \ C __mem_cgroup_same_or_subtree(A, C) would happily return true even though this is not correct because A is not a part of the same hierarchy. So it seems that memcg will need a special treatment here anyway because cgroup core doesn't know about use_hierarchy thingy which is still with us... I will post a patch. > It doesn't seem to end well. > > Thanks. > > -- > tejun > -- > To unsubscribe from this list: send the line "unsubscribe cgroups" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/