f2fs: update start nid only once each circle

	while ((found = __gang_lookup_nat_cache(nm_i,

					nid, NATVEC_SIZE, natvec))) {

		unsigned idx;

		for (idx = 0; idx < found; idx++) {

			struct nat_entry *e = natvec[idx];

			nid = nat_get_nid(e) + 1;

			__del_from_nat_cache(nm_i, e);

		}

		nid = nat_get_nid(natvec[found - 1]) + 1;

		for (idx = 0; idx < found; idx++)

			__del_from_nat_cache(nm_i, natvec[idx]);

	}

	f2fs_bug_on(nm_i->nat_cnt);

	write_unlock(&nm_i->nat_tree_lock);