[PATCH] Disallow swapoff if there is insufficient memory

[PATCH] Disallow swapoff if there is insufficient memory

From: Hugh Dickins <hugh@veritas.com>

First of three small "stop swapoff" patches based on 2.5.67-mm3:

stop swapoff 1/3 vm_enough_memory?

Before embarking upon swapoff, check vm_enough_memory.  Mainly
for consistency in the overcommit_memory 2 (strict accounting) case:
fail with -ENOMEM if it wouldn't let the amount removed be committed.

Will always succeed in the overcommit_memory 1 case, as it should in
root-shoot-foot mode.  In the overcommit_memory 0 case, well, I don't
care much either way, so opted for the simplest code: no special case.
Which means it could now fail at the start; but that's unlikely (case 0
is over-generous) and only when it would have got stuck later on anyway.