From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752100AbaBHQip (ORCPT ); Sat, 8 Feb 2014 11:38:45 -0500 Received: from mail-qa0-f41.google.com ([209.85.216.41]:39528 "EHLO mail-qa0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752034AbaBHQik (ORCPT ); Sat, 8 Feb 2014 11:38:40 -0500 From: Tejun Heo To: lizefan@huawei.com Cc: containers@lists.linux-foundation.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Tejun Heo Subject: [PATCH 5/8] cgroup: make cgroup hold onto its kernfs_node Date: Sat, 8 Feb 2014 11:38:26 -0500 Message-Id: <1391877509-10855-6-git-send-email-tj@kernel.org> X-Mailer: git-send-email 1.8.5.3 In-Reply-To: <1391877509-10855-1-git-send-email-tj@kernel.org> References: <1391877509-10855-1-git-send-email-tj@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org cgroup currently releases its kernfs_node when it gets removed. While not buggy, this makes cgroup->kn access rules complicated than necessary and leads to things like get/put protection around kernfs_remove() in cgroup_destroy_locked(). In addition, we want to use kernfs_name/path() and friends but also want to be able to determine a cgroup's name between removal and release. This patch makes cgroup hold onto its kernfs_node until freed so that cgroup->kn is always accessible. Signed-off-by: Tejun Heo --- kernel/cgroup.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 6da820d..da8aef0 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -957,6 +957,8 @@ static void cgroup_free_fn(struct work_struct *work) cgroup_pidlist_destroy_all(cgrp); + kernfs_put(cgrp->kn); + kfree(rcu_dereference_raw(cgrp->name)); kfree(cgrp); } @@ -3784,6 +3786,12 @@ static long cgroup_create(struct cgroup *parent, const char *name_str, } cgrp->kn = kn; + /* + * This extra ref will be put in cgroup_free_fn() and guarantees + * that @cgrp->kn is always accessible. + */ + kernfs_get(kn); + cgrp->serial_nr = cgroup_serial_nr_next++; /* allocation complete, commit to creation */ @@ -3964,7 +3972,6 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) { struct cgroup *child; struct cgroup_subsys_state *css; - struct kernfs_node *kn; bool empty; int ssid; @@ -4042,13 +4049,8 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) * clearing of cgrp->kn->priv backpointer, which should happen * after all files under it have been removed. */ - kn = cgrp->kn; - kernfs_get(kn); - - kernfs_remove(cgrp->kn); - + kernfs_remove(cgrp->kn); /* @cgrp has an extra ref on its kn */ RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv, NULL); - kernfs_put(kn); mutex_lock(&cgroup_mutex); -- 1.8.5.3