cgroup.c

						       struct cgroup_subsys *ss)
{
	struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
	struct file_system_type *s_type = dentry->d_sb->s_type;
	struct cgroup_subsys_state *css = NULL;
	struct cgroup *cgrp;

	/* is @dentry a cgroup dir? */
	if ((s_type != &cgroup_fs_type && s_type != &cgroup2_fs_type) ||
	    !kn || kernfs_type(kn) != KERNFS_DIR)
		return ERR_PTR(-EBADF);

	rcu_read_lock();

	/*
	 * This path doesn't originate from kernfs and @kn could already
	 * have been or be removed at any point.  @kn->priv is RCU
	 * protected for this access.  See css_release_work_fn() for details.
	 */
	cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
	if (cgrp)
		css = cgroup_css(cgrp, ss);

	if (!css || !css_tryget_online(css))
		css = ERR_PTR(-ENOENT);

	rcu_read_unlock();
	return css;
}

/**
 * css_from_id - lookup css by id
 * @id: the cgroup id
 * @ss: cgroup subsys to be looked into
 *
 * Returns the css if there's valid one with @id, otherwise returns NULL.
 * Should be called under rcu_read_lock().
 */
struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss)
{
	WARN_ON_ONCE(!rcu_read_lock_held());
	return idr_find(&ss->css_idr, id);
}

/**
 * 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_live(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);

/**
 * cgroup_get_from_fd - get a cgroup pointer from a fd
 * @fd: fd obtained by open(cgroup2_dir)
 *
 * Find the cgroup from a fd which should be obtained
 * by opening a cgroup directory.  Returns a pointer to the
 * cgroup on success. ERR_PTR is returned if the cgroup
 * cannot be found.
 */
struct cgroup *cgroup_get_from_fd(int fd)
{
	struct cgroup_subsys_state *css;
	struct cgroup *cgrp;
	struct file *f;

	f = fget_raw(fd);
	if (!f)
		return ERR_PTR(-EBADF);

	css = css_tryget_online_from_dir(f->f_path.dentry, NULL);
	fput(f);
	if (IS_ERR(css))
		return ERR_CAST(css);

	cgrp = css->cgroup;
	if (!cgroup_on_dfl(cgrp)) {
		cgroup_put(cgrp);
		return ERR_PTR(-EBADF);
	}

	return cgrp;
}
EXPORT_SYMBOL_GPL(cgroup_get_from_fd);

/*
 * sock->sk_cgrp_data handling.  For more info, see sock_cgroup_data
 * definition in cgroup-defs.h.
 */
#ifdef CONFIG_SOCK_CGROUP_DATA

#if defined(CONFIG_CGROUP_NET_PRIO) || defined(CONFIG_CGROUP_NET_CLASSID)

DEFINE_SPINLOCK(cgroup_sk_update_lock);
static bool cgroup_sk_alloc_disabled __read_mostly;

void cgroup_sk_alloc_disable(void)
{
	if (cgroup_sk_alloc_disabled)
		return;
	pr_info("cgroup: disabling cgroup2 socket matching due to net_prio or net_cls activation\n");
	cgroup_sk_alloc_disabled = true;
}

#else

#define cgroup_sk_alloc_disabled	false

#endif

void cgroup_sk_alloc(struct sock_cgroup_data *skcd)
{
	if (cgroup_sk_alloc_disabled)
		return;

	/* Socket clone path */
	if (skcd->val) {
		/*
		 * We might be cloning a socket which is left in an empty
		 * cgroup and the cgroup might have already been rmdir'd.
		 * Don't use cgroup_get_live().
		 */
		cgroup_get(sock_cgroup_ptr(skcd));
		return;
	}

	rcu_read_lock();

	while (true) {
		struct css_set *cset;

		cset = task_css_set(current);
		if (likely(cgroup_tryget(cset->dfl_cgrp))) {
			skcd->val = (unsigned long)cset->dfl_cgrp;
			break;
		}
		cpu_relax();
	}

	rcu_read_unlock();
}

void cgroup_sk_free(struct sock_cgroup_data *skcd)
{
	cgroup_put(sock_cgroup_ptr(skcd));
}

#endif	/* CONFIG_SOCK_CGROUP_DATA */

#ifdef CONFIG_CGROUP_BPF
int cgroup_bpf_update(struct cgroup *cgrp, struct bpf_prog *prog,
		      enum bpf_attach_type type, bool overridable)
{
	struct cgroup *parent = cgroup_parent(cgrp);
	int ret;

	mutex_lock(&cgroup_mutex);
	ret = __cgroup_bpf_update(cgrp, parent, prog, type, overridable);
	mutex_unlock(&cgroup_mutex);
	return ret;
}
#endif /* CONFIG_CGROUP_BPF */