import subprocess

def create(length):
    name = 'x' * length
    r = subprocess.call('dmsetup create %s --notable' % name,
                        shell=True)
    print 'Length %s: %i' % (length, r)
    subprocess.call('dmsetup ls', shell=True)
    subprocess.call('dmsetup remove %s' % name,
                    shell=True)
    return r

for i in range(126, 257):
    if create(i) != 0:
        break