[no subject]

[Michal Hocko]

Hi,
here I 3 more preparatory patches which I meant to send on Thursday but
forgot... After more thinking about pfn walkers I have realized that
the current code doesn't check offline holes in zones. From a quick
review that doesn't seem to be a problem currently. Pfn walkers can race
with memory offlining and with the original hotplug impementation those
offline pages can change the zone but I wasn't able to find any serious
problem other than small confusion. The new hotplug code, will not have
any valid zone, though so those code paths should check PageReserved
to rule offline holes. I hope I have addressed all of them in these 3
patches. I would appreciate if Vlastimil and Jonsoo double check after
me.