mm, cma: drain single zone pcplists

CMA allocation drains pcplists so that pages can merge back to buddy
allocator.  Since it operates on a single zone, we can reduce the
pcplists drain to the single zone, which is now possible.

The change should make CMA allocations faster and not disturbing
unrelated pcplists anymore.

Signed-off-by: Vlastimil Babka <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Yasuaki Ishimatsu <[email protected]>
Cc: Zhang Yanfei <[email protected]>
Cc: Xishi Qiu <[email protected]>
Cc: Vladimir Davydov <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Michal Nazarewicz <[email protected]>
Cc: Marek Szyprowski <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/page_alloc.c

@@ -6416,7 +6416,7 @@ int alloc_contig_range(unsigned long start, unsigned long end,
 	 */
 
 	lru_add_drain_all();
-	drain_all_pages(NULL);
+	drain_all_pages(cc.zone);
 
 	order = 0;
 	outer_start = start;