mm, memory_hotplug: consider offline memblocks removable

mm, memory_hotplug: consider offline memblocks removable

is_pageblock_removable_nolock() relies on having zone association to
examine all the page blocks to check whether they are movable or free.
This is just wasting of cycles when the memblock is offline.  Later
patch in the series will also change the time when the page is
associated with a zone so we let's bail out early if the memblock is
offline.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Michal Hocko <[email protected]>
Reported-by: Igor Mammedov <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Balbir Singh <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Daniel Kiper <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Jerome Glisse <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Reza Arbab <[email protected]>
Cc: Tobias Regnery <[email protected]>
Cc: Toshi Kani <[email protected]>
Cc: Vitaly Kuznetsov <[email protected]>
Cc: Xishi Qiu <[email protected]>
Cc: Yasuaki Ishimatsu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>