From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx170.postini.com [74.125.245.170]) by kanga.kvack.org (Postfix) with SMTP id 183DB6B0033 for ; Wed, 24 Jul 2013 06:02:42 -0400 (EDT) Message-ID: <51EFA5C7.40504@huawei.com> Date: Wed, 24 Jul 2013 18:00:39 +0800 From: Li Zefan MIME-Version: 1.0 Subject: [PATCH v2 3/8] cgroup: implement cgroup_from_id() References: <51EFA554.6080801@huawei.com> In-Reply-To: <51EFA554.6080801@huawei.com> Content-Type: text/plain; charset="GB2312" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Tejun Heo Cc: Andrew Morton , Glauber Costa , KAMEZAWA Hiroyuki , Michal Hocko , Johannes Weiner , LKML , Cgroups , linux-mm@kvack.org This will be used as a replacement for css_lookup(). There's a difference with cgroup id and css id. cgroup id starts with 0, while css id starts with 1. Signed-off-by: Li Zefan --- include/linux/cgroup.h | 2 ++ kernel/cgroup.c | 16 ++++++++++++++++ 2 files changed, 18 insertions(+) diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 8c107e9..e8eb361 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -553,6 +553,8 @@ int task_cgroup_path_from_hierarchy(struct task_struct *task, int hierarchy_id, int cgroup_task_count(const struct cgroup *cgrp); +struct cgroup *cgroup_from_id(struct cgroup_subsys *ss, int id); + /* * Control Group taskset, used to pass around set of tasks to cgroup_subsys * methods. diff --git a/kernel/cgroup.c b/kernel/cgroup.c index ee3c02e..9b27775 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -5536,6 +5536,22 @@ struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id) return css ? css : ERR_PTR(-ENOENT); } +/** + * cgroup_from_id - lookup cgroup by id + * @ss: cgroup subsys to be looked into + * @id: the cgroup id + * + * Returns the cgroup is there's valid one with @id, otherwise returns Null. + * Should be called under rcu_readlock(). + */ +struct cgroup *cgroup_from_id(struct cgroup_subsys *ss, int id) +{ + rcu_lockdep_assert(rcu_read_lock_held(), + "cgroup_from_id() needs rcu_read_lock()" + " protection"); + return idr_find(&ss->root->cgroup_idr, id); +} + #ifdef CONFIG_CGROUP_DEBUG static struct cgroup_subsys_state *debug_css_alloc(struct cgroup *cgrp) { -- 1.8.0.2 -- 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