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Commit 16af4396 authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: implement cgroup_get_from_path() and expose cgroup_put() 



Implement cgroup_get_from_path() using kernfs_walk_and_get() which
obtains a default hierarchy cgroup from its path.  This will be used
to allow cgroup path based matching from outside cgroup proper -
e.g. networking and perf.

v2: Add EXPORT_SYMBOL_GPL(cgroup_get_from_path).

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent bd96f76a

include/linux/cgroup.h

+7 −0
Original line number Diff line number Diff line
@@ -81,6 +81,8 @@ struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgroup, 
struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,

						       struct cgroup_subsys *ss);



struct cgroup *cgroup_get_from_path(const char *path);



int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);

int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
@@ -351,6 +353,11 @@ static inline void css_put_many(struct cgroup_subsys_state *css, unsigned int n) 
		percpu_ref_put_many(&css->refcnt, n);

}



static inline void cgroup_put(struct cgroup *cgrp)

{

	css_put(&cgrp->self);

}



/**

 * task_css_set_check - obtain a task's css_set with extra access conditions

 * @task: the task to obtain css_set for

kernel/cgroup.c

+34 −5
Original line number Diff line number Diff line
@@ -434,11 +434,6 @@ static bool cgroup_tryget(struct cgroup *cgrp) 
	return css_tryget(&cgrp->self);

}



static void cgroup_put(struct cgroup *cgrp)

{

	css_put(&cgrp->self);

}



struct cgroup_subsys_state *of_css(struct kernfs_open_file *of)

{

	struct cgroup *cgrp = of->kn->parent->priv;
@@ -5753,6 +5748,40 @@ struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss) 
	return id > 0 ? idr_find(&ss->css_idr, id) : NULL;

}



/**

 * cgroup_get_from_path - lookup and get a cgroup from its default hierarchy path

 * @path: path on the default hierarchy

 *

 * Find the cgroup at @path on the default hierarchy, increment its

 * reference count and return it.  Returns pointer to the found cgroup on

 * success, ERR_PTR(-ENOENT) if @path doens't exist and ERR_PTR(-ENOTDIR)

 * if @path points to a non-directory.

 */

struct cgroup *cgroup_get_from_path(const char *path)

{

	struct kernfs_node *kn;

	struct cgroup *cgrp;



	mutex_lock(&cgroup_mutex);



	kn = kernfs_walk_and_get(cgrp_dfl_root.cgrp.kn, path);

	if (kn) {

		if (kernfs_type(kn) == KERNFS_DIR) {

			cgrp = kn->priv;

			cgroup_get(cgrp);

		} else {

			cgrp = ERR_PTR(-ENOTDIR);

		}

		kernfs_put(kn);

	} else {

		cgrp = ERR_PTR(-ENOENT);

	}



	mutex_unlock(&cgroup_mutex);

	return cgrp;

}

EXPORT_SYMBOL_GPL(cgroup_get_from_path);



#ifdef CONFIG_CGROUP_DEBUG

static struct cgroup_subsys_state *

debug_css_alloc(struct cgroup_subsys_state *parent_css)