This is really just a token gesture at this point. We can't really turn
on swapping here anymore because (I think) we need to do a namei() lookup
in order to get a vnode which we can pass to swaponvp(). But to do a
namei(), we need a properly initialized proc structure, and we don't
have one. (I was hopping to toss it proc0, but that isn't initialized
until later.) We could conceiveably fabricate a dummy proc structure
to make namei() happy, but that's too much work for too little payoff.
For now, swapgeneric's only remaining saving grace is that it lets
you set the root device with -a.
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