From: Hugh Dickins <hugh@veritas.com>

The current behaviour is that once swapoff has filled memory, other tasks get
OOMkilled one by one until swapoff completes, or more likely hangs.  It is
better that swapoff be the first choice for OOMkill.

The patch changes the oom-killer so that it will kill off any
currently-running swapoff instance before killing any other task.

(Bit kludgy, couldn't think of a better way)