mm/memcg: use vm_swappiness from target memory cgroup

Use vm_swappiness from memory cgroup which is triggered this memory
reclaim.  This is more reasonable and allows to kill one argument.

[akpm@linux-foundation.org: fix build (patch skew)]
Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujtisu.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Glauber Costa <glommer@parallels.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/vmscan.c

@@ -1622,12 +1622,11 @@ static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
 	return shrink_inactive_list(nr_to_scan, mz, sc, priority, lru);
 }
 
-static int vmscan_swappiness(struct mem_cgroup_zone *mz,
-			     struct scan_control *sc)
+static int vmscan_swappiness(struct scan_control *sc)
 {
 	if (global_reclaim(sc))
 		return vm_swappiness;
-	return mem_cgroup_swappiness(mz->mem_cgroup);
+	return mem_cgroup_swappiness(sc->target_mem_cgroup);
 }
 
 /*
@@ -1695,8 +1694,8 @@ static void get_scan_count(struct mem_cgroup_zone *mz, struct scan_control *sc,
 	 * With swappiness at 100, anonymous and file have the same priority.
 	 * This scanning priority is essentially the inverse of IO cost.
 	 */
-	anon_prio = vmscan_swappiness(mz, sc);
-	file_prio = 200 - vmscan_swappiness(mz, sc);
+	anon_prio = vmscan_swappiness(sc);
+	file_prio = 200 - vmscan_swappiness(sc);
 
 	/*
 	 * OK, so we have swap space and a fair amount of page cache
@@ -1741,7 +1740,7 @@ static void get_scan_count(struct mem_cgroup_zone *mz, struct scan_control *sc,
 		unsigned long scan;
 
 		scan = zone_nr_lru_pages(mz, lru);
-		if (priority || noswap || !vmscan_swappiness(mz, sc)) {
+		if (priority || noswap || !vmscan_swappiness(sc)) {
 			scan >>= priority;
 			if (!scan && force_scan)
 				scan = SWAP_CLUSTER_MAX;