quota: Cleanup list iteration in dqcache_shrink_scan()

static unsigned long

dqcache_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)

{

	struct list_head *head;

	struct dquot *dquot;

	unsigned long freed = 0;

	spin_lock(&dq_list_lock);

	head = free_dquots.next;

	while (head != &free_dquots && sc->nr_to_scan) {

		dquot = list_entry(head, struct dquot, dq_free);

	while (!list_empty(&free_dquots) && sc->nr_to_scan) {

		dquot = list_first_entry(&free_dquots, struct dquot, dq_free);

		remove_dquot_hash(dquot);

		remove_free_dquot(dquot);

		remove_inuse(dquot);

		do_destroy_dquot(dquot);

		sc->nr_to_scan--;

		freed++;

		head = free_dquots.next;

	}

	spin_unlock(&dq_list_lock);

	return freed;