Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936740Ab3DICXt (ORCPT ); Mon, 8 Apr 2013 22:23:49 -0400 Received: from mail-qa0-f44.google.com ([209.85.216.44]:34323 "EHLO mail-qa0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933403Ab3DICXo (ORCPT ); Mon, 8 Apr 2013 22:23:44 -0400 From: Tejun Heo To: mingo@redhat.com Cc: a.p.zijlstra@chello.nl, paulus@samba.org, acme@ghostprotocols.net, eranian@google.com, namhyung.kim@lge.com, lizefan@huawei.com, mhocko@suse.cz, kamezawa.hiroyu@jp.fujitsu.com, cgroups@vger.kernel.org, containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Tejun Heo Subject: [PATCH 2/3] cgroup: implement cgroup_is_descendant() Date: Mon, 8 Apr 2013 19:23:32 -0700 Message-Id: <1365474213-13354-3-git-send-email-tj@kernel.org> X-Mailer: git-send-email 1.8.1.4 In-Reply-To: <1365474213-13354-1-git-send-email-tj@kernel.org> References: <1365474213-13354-1-git-send-email-tj@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2448 Lines: 73 From: Li Zefan A couple controllers want to determine whether two cgroups are in ancestor/descendant relationship. As it's more likely that the descendant is the primary subject of interest and there are other operations focusing on the descendants, let's ask is_descendent rather than is_ancestor. Implementation is trivial as the previous patch guarantees that all ancestors of a cgroup stay accessible as long as the cgroup is accessible. tj: Removed depth optimization, renamed from cgroup_is_ancestor(), rewrote descriptions. Signed-off-by: Li Zefan Signed-off-by: Tejun Heo --- include/linux/cgroup.h | 1 + kernel/cgroup.c | 20 ++++++++++++++++++++ 2 files changed, 21 insertions(+) diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 515927e..45aee0f 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -439,6 +439,7 @@ int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts); int cgroup_rm_cftypes(struct cgroup_subsys *ss, struct cftype *cfts); int cgroup_is_removed(const struct cgroup *cgrp); +bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor); int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen); diff --git a/kernel/cgroup.c b/kernel/cgroup.c index d7dfa64..678a22c 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -276,6 +276,26 @@ inline int cgroup_is_removed(const struct cgroup *cgrp) return test_bit(CGRP_REMOVED, &cgrp->flags); } +/** + * cgroup_is_descendant - test ancestry + * @cgrp: the cgroup to be tested + * @ancestor: possible ancestor of @cgrp + * + * Test whether @cgrp is a descendant of @ancestor. It also returns %true + * if @cgrp == @ancestor. This function is safe to call as long as @cgrp + * and @ancestor are accessible. + */ +bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor) +{ + while (cgrp) { + if (cgrp == ancestor) + return true; + cgrp = cgrp->parent; + } + return false; +} +EXPORT_SYMBOL_GPL(cgroup_is_descendant); + /* bits in struct cgroupfs_root flags field */ enum { ROOT_NOPREFIX, /* mounted subsystems have no named prefix */ -- 1.8.1.4 -- 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/