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cgroup: implement task_cgroup_path_from_hierarchy()

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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: Tejun Heo <tj@kernel.org>
Acked-by: Greg Kroah-Hartman <greg@kroah.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Kay Sievers <kay@vrfy.org>
Cc: Lennart Poettering <lennart@poettering.net>
Cc: Daniel Mack <daniel@zonque.org>
This commit is contained in:
Tejun Heo 2013-04-14 20:50:08 -07:00
parent 1a57423166
commit 857a2beb09
2 changed files with 34 additions and 0 deletions
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2
include/linux/cgroup.h
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@ -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);

32
kernel/cgroup.c
View File

@ -1827,6 +1827,38 @@ out:
}
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
*/