First, for SWAP_ON and SWAP_CTL, the third argument to swapctl(2)
represents the priority of this swap device. Is a lower number a
higher priority or vice versa?

Second, can this syscall be used as:

	swapctl(SWAP_CTL, se, 0);

... in order to change anything BUT the priority of the swap device?
(Like, say, passed a swapent device whose se_nblks value has
changed?)

       ~ g r @ eclipsed.net