revert "vmscan, memcg: do softlimit reclaim also for targeted reclaim"

Revert commit a5b7c87f ("vmscan, memcg: do softlimit reclaim also
for targeted reclaim")

I merged this prematurely - Michal and Johannes still disagree about the
overall design direction and the future remains unclear.

Cc: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/memcontrol.h

@@ -234,8 +234,7 @@ static inline void mem_cgroup_dec_page_stat(struct page *page,
 	mem_cgroup_update_page_stat(page, idx, -1);
 }
 
-bool mem_cgroup_soft_reclaim_eligible(struct mem_cgroup *memcg,
-		struct mem_cgroup *root);
+bool mem_cgroup_soft_reclaim_eligible(struct mem_cgroup *memcg);
 
 void __mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx);
 static inline void mem_cgroup_count_vm_event(struct mm_struct *mm,
@@ -435,8 +434,7 @@ static inline void mem_cgroup_dec_page_stat(struct page *page,
 }
 
 static inline
-bool mem_cgroup_soft_reclaim_eligible(struct mem_cgroup *memcg,
-		struct mem_cgroup *root)
+bool mem_cgroup_soft_reclaim_eligible(struct mem_cgroup *memcg)
 {
 	return false;
 }

mm/memcontrol.c

@@ -1760,13 +1760,11 @@ int mem_cgroup_select_victim_node(struct mem_cgroup *memcg)
 #endif
 
 /*
- * A group is eligible for the soft limit reclaim under the given root
- * hierarchy if
+ * A group is eligible for the soft limit reclaim if
  * 	a) it is over its soft limit
  *	b) any parent up the hierarchy is over its soft limit
  */
-bool mem_cgroup_soft_reclaim_eligible(struct mem_cgroup *memcg,
-		struct mem_cgroup *root)
+bool mem_cgroup_soft_reclaim_eligible(struct mem_cgroup *memcg)
 {
 	struct mem_cgroup *parent = memcg;
 
@@ -1774,14 +1772,12 @@ bool mem_cgroup_soft_reclaim_eligible(struct mem_cgroup *memcg,
 		return true;
 
 	/*
-	 * If any parent up to the root in the hierarchy is over its soft limit
-	 * then we have to obey and reclaim from this group as well.
+	 * If any parent up the hierarchy is over its soft limit then we
+	 * have to obey and reclaim from this group as well.
 	 */
 	while ((parent = parent_mem_cgroup(parent))) {
 		if (res_counter_soft_limit_excess(&parent->res))
 			return true;
-		if (parent == root)
-			break;
 	}
 
 	return false;

mm/vmscan.c

@@ -142,7 +142,7 @@ static bool global_reclaim(struct scan_control *sc)
 
 static bool mem_cgroup_should_soft_reclaim(struct scan_control *sc)
 {
-	return !mem_cgroup_disabled();
+	return !mem_cgroup_disabled() && global_reclaim(sc);
 }
 #else
 static bool global_reclaim(struct scan_control *sc)
@@ -2195,7 +2195,7 @@ __shrink_zone(struct zone *zone, struct scan_control *sc, bool soft_reclaim)
 			struct lruvec *lruvec;
 
 			if (soft_reclaim &&
-			    !mem_cgroup_soft_reclaim_eligible(memcg, root)) {
+			    !mem_cgroup_soft_reclaim_eligible(memcg)) {
 				memcg = mem_cgroup_iter(root, memcg, &reclaim);
 				continue;
 			}