netprio_cgroup: simplify write_priomap()

static int write_priomap(struct cgroup *cgrp, struct cftype *cft,

			 const char *buffer)

{

	char *devname = kstrdup(buffer, GFP_KERNEL);

	int ret = -EINVAL;

	u32 prioidx = cgrp_netprio_state(cgrp)->prioidx;

	unsigned long priority;

	char *priostr;

	char devname[IFNAMSIZ + 1];

	struct net_device *dev;

	struct netprio_map *map;

	u32 prio;

	int ret;

	if (!devname)

		return -ENOMEM;

	/*

	 * Minimally sized valid priomap string

	 */

	if (strlen(devname) < 3)

		goto out_free_devname;

	priostr = strstr(devname, " ");

	if (!priostr)

		goto out_free_devname;

	/*

	 *Separate the devname from the associated priority

	 *and advance the priostr pointer to the priority value

	 */

	*priostr = '\0';

	priostr++;

	/*

	 * If the priostr points to NULL, we're at the end of the passed

	 * in string, and its not a valid write

	 */

	if (*priostr == '\0')

		goto out_free_devname;

	ret = kstrtoul(priostr, 10, &priority);

	if (ret < 0)

		goto out_free_devname;

	ret = -ENODEV;

	if (sscanf(buffer, "%"__stringify(IFNAMSIZ)"s %u", devname, &prio) != 2)

		return -EINVAL;

	dev = dev_get_by_name(&init_net, devname);

	if (!dev)

		goto out_free_devname;

		return -ENODEV;

	rtnl_lock();

	ret = write_update_netdev_table(dev);

	if (ret < 0)

		goto out_put_dev;

	if (ret)

		goto out_unlock;

	map = rtnl_dereference(dev->priomap);

	if (map)

		map->priomap[prioidx] = priority;

out_put_dev:

		map->priomap[prioidx] = prio;

out_unlock:

	rtnl_unlock();

	dev_put(dev);

out_free_devname:

	kfree(devname);

	return ret;

}