mm, vmscan: move lru_lock to the node

Node-based reclaim requires node-based LRUs and locking.  This is a
preparation patch that just moves the lru_lock to the node so later
patches are easier to review.  It is a mechanical change but note this
patch makes contention worse because the LRU lock is hotter and direct
reclaim and kswapd can contend on the same lock even when reclaiming
from different zones.

Link: http://lkml.kernel.org/r/1467970510-21195-3-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 40dfca3..9b70f9c 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2065,7 +2065,7 @@
 {
 	struct zone *zone = page_zone(page);
 
-	spin_lock_irq(&zone->lru_lock);
+	spin_lock_irq(zone_lru_lock(zone));
 	if (PageLRU(page)) {
 		struct lruvec *lruvec;
 
@@ -2089,7 +2089,7 @@
 		SetPageLRU(page);
 		add_page_to_lru_list(page, lruvec, page_lru(page));
 	}
-	spin_unlock_irq(&zone->lru_lock);
+	spin_unlock_irq(zone_lru_lock(zone));
 }
 
 static void commit_charge(struct page *page, struct mem_cgroup *memcg,
@@ -2389,7 +2389,7 @@
 
 /*
  * Because tail pages are not marked as "used", set it. We're under
- * zone->lru_lock and migration entries setup in all page mappings.
+ * zone_lru_lock and migration entries setup in all page mappings.
  */
 void mem_cgroup_split_huge_fixup(struct page *head)
 {