Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754557Ab3HES5o (ORCPT ); Mon, 5 Aug 2013 14:57:44 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37859 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754298Ab3HES5l (ORCPT ); Mon, 5 Aug 2013 14:57:41 -0400 Date: Mon, 5 Aug 2013 14:57:23 -0400 From: Aristeu Rozanski To: Tejun Heo Cc: Li Zefan , Jens Axboe , Vivek Goyal , Matt Helsley , Johannes Weiner , Michal Hocko , Balbir Singh , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, containers@lists.linux-foundation.org Subject: Re: [PATCH cgroup/for-3.12] cgroup: make css_for_each_descendant() and friends include the origin css in the iteration Message-ID: <20130805185723.GD7878@redhat.com> References: <20130804230703.GA12029@htj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130804230703.GA12029@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: 2647 Lines: 63 On Sun, Aug 04, 2013 at 07:07:03PM -0400, Tejun Heo wrote: > I've been wanting to do this for some time and given all the recent > API updates now seems like a pretty good opportunity. Verified > freezer and blkcg. The conversions are mostly straight forward but > I'd much appreciate acks from controller maintainers. > > The patch is on top of > > cgroup/for-3.12 61584e3f4 ("cgroup: Merge branch 'for-3.11-fixes' into for-3.12") > + [1] cgroup: use cgroup_subsys_state as the primary subsystem interface handle > + [2] cgroup: make cgroup_event specific to memcg > > and available in the following git branch. > > git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git review-descendant-update > > Thanks. > > [1] https://lkml.org/lkml/2013/8/1/722 > [2] http://thread.gmane.org/gmane.linux.kernel.cgroups/8726 > > ------- 8< ------- > > From 0e84b0865ab8a87f1c1443e4777c20c7f14e13b6 Mon Sep 17 00:00:00 2001 > From: Tejun Heo > Date: Sun, 4 Aug 2013 19:01:23 -0400 > > Previously, all css descendant iterators didn't include the origin > (root of subtree) css in the iteration. The reasons were maintaining > consistency with css_for_each_child() and that at the time of > introduction more use cases needed skipping the origin anyway; > however, given that css_is_descendant() considers self to be a > descendant, omitting the origin css has become more confusing and > looking at the accumulated use cases rather clearly indicates that > including origin would result in simpler code overall. > > While this is a change which can easily lead to subtle bugs, cgroup > API including the iterators has recently gone through major > restructuring and no out-of-tree changes will be applicable without > adjustments making this a relatively acceptable opportunity for this > type of change. > > The conversions are mostly straight-forward. If the iteration block > had explicit origin handling before or after, it's moved inside the > iteration. If not, if (pos == origin) continue; is added. Some > conversions add extra reference get/put around origin handling by > consolidating origin handling and the rest. While the extra ref > operations aren't strictly necessary, this shouldn't cause any > noticeable difference. Looks good. Thanks for the heads up, saved some hours of head scratching :) Acked-by: Aristeu Rozanski -- Aristeu -- 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/