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: Tejun Heo <tj@kernel.org>
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@ -81,6 +81,8 @@ struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgroup,
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struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
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struct cgroup_subsys *ss);
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struct cgroup *cgroup_get_from_path(const char *path);
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int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
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int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
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@ -351,6 +353,11 @@ static inline void css_put_many(struct cgroup_subsys_state *css, unsigned int n)
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percpu_ref_put_many(&css->refcnt, n);
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}
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static inline void cgroup_put(struct cgroup *cgrp)
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{
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css_put(&cgrp->self);
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}
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/**
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* task_css_set_check - obtain a task's css_set with extra access conditions
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* @task: the task to obtain css_set for
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@ -434,11 +434,6 @@ static bool cgroup_tryget(struct cgroup *cgrp)
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return css_tryget(&cgrp->self);
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}
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static void cgroup_put(struct cgroup *cgrp)
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{
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css_put(&cgrp->self);
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}
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struct cgroup_subsys_state *of_css(struct kernfs_open_file *of)
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{
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struct cgroup *cgrp = of->kn->parent->priv;
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@ -5753,6 +5748,40 @@ struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss)
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return id > 0 ? idr_find(&ss->css_idr, id) : NULL;
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}
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/**
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* cgroup_get_from_path - lookup and get a cgroup from its default hierarchy path
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* @path: path on the default hierarchy
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*
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* Find the cgroup at @path on the default hierarchy, increment its
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* reference count and return it. Returns pointer to the found cgroup on
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* success, ERR_PTR(-ENOENT) if @path doens't exist and ERR_PTR(-ENOTDIR)
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* if @path points to a non-directory.
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*/
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struct cgroup *cgroup_get_from_path(const char *path)
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{
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struct kernfs_node *kn;
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struct cgroup *cgrp;
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mutex_lock(&cgroup_mutex);
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kn = kernfs_walk_and_get(cgrp_dfl_root.cgrp.kn, path);
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if (kn) {
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if (kernfs_type(kn) == KERNFS_DIR) {
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cgrp = kn->priv;
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cgroup_get(cgrp);
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} else {
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cgrp = ERR_PTR(-ENOTDIR);
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}
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kernfs_put(kn);
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} else {
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cgrp = ERR_PTR(-ENOENT);
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}
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mutex_unlock(&cgroup_mutex);
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return cgrp;
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}
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EXPORT_SYMBOL_GPL(cgroup_get_from_path);
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#ifdef CONFIG_CGROUP_DEBUG
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static struct cgroup_subsys_state *
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debug_css_alloc(struct cgroup_subsys_state *parent_css)
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