Nick Piggin wrote:

> 
> I think my patch would be sufficient to handle the kswapd side
> (yours would be valid too, but no need to add the extra checks).

Here is the combined patch with Andrew's hunk added.

I guess it doesn't _really_ matter which gets tested, but this
one is probably the preferred way to go because it doesn't even
wake up kswapd for empty zones. Andrew, do you agree?

I guess it should get into -bk pretty soon if it passes testing.
It is fairly easy to see the failure cases that are fixed (and
hopefully it doesn't domino yet another latent bug :P).