Example #1
0
/*
 * cgroup_rename - Only allow simple rename of directories in place.
 */
static int cgroup1_rename(struct kernfs_node *kn, struct kernfs_node *new_parent,
			  const char *new_name_str)
{
	struct cgroup *cgrp = kn->priv;
	int ret;

	if (kernfs_type(kn) != KERNFS_DIR)
		return -ENOTDIR;
	if (kn->parent != new_parent)
		return -EIO;

	/*
	 * We're gonna grab cgroup_mutex which nests outside kernfs
	 * active_ref.  kernfs_rename() doesn't require active_ref
	 * protection.  Break them before grabbing cgroup_mutex.
	 */
	kernfs_break_active_protection(new_parent);
	kernfs_break_active_protection(kn);

	mutex_lock(&cgroup_mutex);

	ret = kernfs_rename(kn, new_parent, new_name_str);
	if (!ret)
		TRACE_CGROUP_PATH(rename, cgrp);

	mutex_unlock(&cgroup_mutex);

	kernfs_unbreak_active_protection(kn);
	kernfs_unbreak_active_protection(new_parent);
	return ret;
}
Example #2
0
static int dslab_rmdir(struct kernfs_node *kn)
{
	kernfs_break_active_protection(kn);
	kernfs_remove(kn);
	kernfs_unbreak_active_protection(kn);

	return 0;
}
Example #3
0
static int dslab_rename(struct kernfs_node *kn, 
					struct kernfs_node *new_parent,
					const char *new_name_str)
{
	int ret = 0;	

	if (kernfs_type(kn) != KERNFS_DIR)
		return -ENOTDIR;
	if (kn->parent != new_parent)
		return -EIO;

	kernfs_break_active_protection(new_parent);
	kernfs_break_active_protection(kn);
	ret = kernfs_rename(kn, new_parent, new_name_str);
	kernfs_unbreak_active_protection(kn);
	kernfs_unbreak_active_protection(new_parent);

	return ret;
}
Example #4
0
/**
 * kernfs_remove_self - remove a kernfs_node from its own method
 * @kn: the self kernfs_node to remove
 *
 * The caller must be running off of a kernfs operation which is invoked
 * with an active reference - e.g. one of kernfs_ops.  This can be used to
 * implement a file operation which deletes itself.
 *
 * For example, the "delete" file for a sysfs device directory can be
 * implemented by invoking kernfs_remove_self() on the "delete" file
 * itself.  This function breaks the circular dependency of trying to
 * deactivate self while holding an active ref itself.  It isn't necessary
 * to modify the usual removal path to use kernfs_remove_self().  The
 * "delete" implementation can simply invoke kernfs_remove_self() on self
 * before proceeding with the usual removal path.  kernfs will ignore later
 * kernfs_remove() on self.
 *
 * kernfs_remove_self() can be called multiple times concurrently on the
 * same kernfs_node.  Only the first one actually performs removal and
 * returns %true.  All others will wait until the kernfs operation which
 * won self-removal finishes and return %false.  Note that the losers wait
 * for the completion of not only the winning kernfs_remove_self() but also
 * the whole kernfs_ops which won the arbitration.  This can be used to
 * guarantee, for example, all concurrent writes to a "delete" file to
 * finish only after the whole operation is complete.
 */
bool kernfs_remove_self(struct kernfs_node *kn)
{
	bool ret;

	mutex_lock(&kernfs_mutex);
	kernfs_break_active_protection(kn);

	/*
	 * SUICIDAL is used to arbitrate among competing invocations.  Only
	 * the first one will actually perform removal.  When the removal
	 * is complete, SUICIDED is set and the active ref is restored
	 * while holding kernfs_mutex.  The ones which lost arbitration
	 * waits for SUICDED && drained which can happen only after the
	 * enclosing kernfs operation which executed the winning instance
	 * of kernfs_remove_self() finished.
	 */
	if (!(kn->flags & KERNFS_SUICIDAL)) {
		kn->flags |= KERNFS_SUICIDAL;
		__kernfs_remove(kn);
		kn->flags |= KERNFS_SUICIDED;
		ret = true;
	} else {
		wait_queue_head_t *waitq = &kernfs_root(kn)->deactivate_waitq;
		DEFINE_WAIT(wait);

		while (true) {
			prepare_to_wait(waitq, &wait, TASK_UNINTERRUPTIBLE);

			if ((kn->flags & KERNFS_SUICIDED) &&
			    atomic_read(&kn->active) == KN_DEACTIVATED_BIAS)
				break;

			mutex_unlock(&kernfs_mutex);
			schedule();
			mutex_lock(&kernfs_mutex);
		}
		finish_wait(waitq, &wait);
		WARN_ON_ONCE(!RB_EMPTY_NODE(&kn->rb));
		ret = false;
	}

	/*
	 * This must be done while holding kernfs_mutex; otherwise, waiting
	 * for SUICIDED && deactivated could finish prematurely.
	 */
	kernfs_unbreak_active_protection(kn);

	mutex_unlock(&kernfs_mutex);
	return ret;
}