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Commit 857a2beb authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: implement task_cgroup_path_from_hierarchy() 



kdbus folks want a sane way to determine the cgroup path that a given
task belongs to on a given hierarchy, which is a reasonble thing to
expect from cgroup core.

Implement task_cgroup_path_from_hierarchy().

v2: Dropped unnecessary NULL check on the return value of
    task_cgroup_from_root() as suggested by Li Zefan.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarGreg Kroah-Hartman <greg@kroah.com>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
Cc: Kay Sievers <kay@vrfy.org>
Cc: Lennart Poettering <lennart@poettering.net>
Cc: Daniel Mack <daniel@zonque.org>
parent 1a574231

include/linux/cgroup.h

+2 −0
Original line number Diff line number Diff line
@@ -542,6 +542,8 @@ 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);

int task_cgroup_path_from_hierarchy(struct task_struct *task, int hierarchy_id,

				    char *buf, size_t buflen);



int cgroup_task_count(const struct cgroup *cgrp);

kernel/cgroup.c

+32 −0
Original line number Diff line number Diff line
@@ -1827,6 +1827,38 @@ int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen) 
}

EXPORT_SYMBOL_GPL(cgroup_path);



/**

 * task_cgroup_path_from_hierarchy - cgroup path of a task on a hierarchy

 * @task: target task

 * @hierarchy_id: the hierarchy to look up @task's cgroup from

 * @buf: the buffer to write the path into

 * @buflen: the length of the buffer

 *

 * Determine @task's cgroup on the hierarchy specified by @hierarchy_id and

 * copy its path into @buf.  This function grabs cgroup_mutex and shouldn't

 * be used inside locks used by cgroup controller callbacks.

 */

int task_cgroup_path_from_hierarchy(struct task_struct *task, int hierarchy_id,

				    char *buf, size_t buflen)

{

	struct cgroupfs_root *root;

	struct cgroup *cgrp = NULL;

	int ret = -ENOENT;



	mutex_lock(&cgroup_mutex);



	root = idr_find(&cgroup_hierarchy_idr, hierarchy_id);

	if (root) {

		cgrp = task_cgroup_from_root(task, root);

		ret = cgroup_path(cgrp, buf, buflen);

	}



	mutex_unlock(&cgroup_mutex);



	return ret;

}

EXPORT_SYMBOL_GPL(task_cgroup_path_from_hierarchy);



/*

 * Control Group taskset

 */