drain_node_pages() currently drains the complete pageset of all pages.  If
there are a large number of pages in the queues then we may hold off
interrupts for too long.

Duplicate the method used in free_hot_cold_page.  Only drain pcp->batch
pages at one time.
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>