[PATCH v3 3/8] cgroup: implement cgroup_from_id()
From: Li Zefan <hidden>
Date: 2013-07-29 07:08:46
Also in:
linux-mm, lkml
Subsystem:
control group (cgroup), the rest · Maintainers:
Tejun Heo, Johannes Weiner, Michal Koutný, Linus Torvalds
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 <redacted> Reviewed-by: Michal Hocko <redacted> --- 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 b7c7c68..dc4a749 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 if 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
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