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cgroup: implement cgroup_get_from_path() and expose cgroup_put()

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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: Tejun Heo <tj@kernel.org>
This commit is contained in:
Tejun Heo
2015-11-20 15:55:52 -05:00
parent bd96f76a24
commit 16af439645
2 changed files with 41 additions and 5 deletions
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39
kernel/cgroup.c
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@@ -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)