mm, page_alloc: reserve pageblocks for high-order atomic allocations on demand -fix

mm, page_alloc: reserve pageblocks for high-order atomic allocations on demand -fix

There is a redundant check and a memory leak introduced by a patch in
mmotm.  This patch removes an unlikely(order) check as we are sure order
is not zero at the time.  It also checks if a page is already allocated to
avoid a memory leak.

This is a fix to the mmotm patch
mm-page_alloc-reserve-pageblocks-for-high-order-atomic-allocations-on-demand.patch

Signed-off-by: yalin wang <yalin.wang2010@gmail.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>