[PATCH 2/2] memcg, res_counter: replace res_counter_soft_limit_excess by a more generic helper

[Michal Hocko]

Later patches in the series will add new limits which we will want to
check for excess as well so change the current on-off
res_counter_soft_limit_excess to a more generic helper.

Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
---
 include/linux/res_counter.h | 21 +++++++++++++++------
 mm/memcontrol.c             | 10 +++++-----
 2 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/include/linux/res_counter.h b/include/linux/res_counter.h
index bea7f9f45f7a..9015013784fa 100644
--- a/include/linux/res_counter.h
+++ b/include/linux/res_counter.h
@@ -156,23 +156,32 @@ static inline unsigned long long res_counter_margin(struct res_counter *cnt)
 }
 
 /**
- * Get the difference between the usage and the soft limit
+ * Get the difference between the usage and the limit defined
+ * by the given member
  * @cnt: The counter
  *
- * Returns 0 if usage is less than or equal to soft limit
- * The difference between usage and soft limit, otherwise.
+ * Returns 0 if usage is less than or equal to the limit defined
+ * by member or the difference otherwise.
  */
 static inline unsigned long long
-res_counter_soft_limit_excess(struct res_counter *cnt)
+res_counter_limit_excess(struct res_counter *cnt, int member)
 {
 	unsigned long long excess;
+	unsigned long long limit;
 	unsigned long flags;
 
 	spin_lock_irqsave(&cnt->lock, flags);
-	if (cnt->usage <= cnt->soft_limit)
+	switch(member) {
+		case RES_SOFT_LIMIT:
+			limit = cnt->soft_limit;
+			break;
+		default:
+			BUG();
+	}
+	if (cnt->usage <= limit)
 		excess = 0;
 	else
-		excess = cnt->usage - cnt->soft_limit;
+		excess = cnt->usage - limit;
 	spin_unlock_irqrestore(&cnt->lock, flags);
 	return excess;
 }
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 1ad5d4a2bc4e..75b5db78e9be 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -773,7 +773,7 @@ static void mem_cgroup_update_tree(struct mem_cgroup *memcg, struct page *page)
 	 */
 	for (; memcg; memcg = parent_mem_cgroup(memcg)) {
 		mz = mem_cgroup_page_zoneinfo(memcg, page);
-		excess = res_counter_soft_limit_excess(&memcg->res);
+		excess = res_counter_limit_excess(&memcg->res, RES_SOFT_LIMIT);
 		/*
 		 * We have to update the tree if mz is on RB-tree or
 		 * mem is over its softlimit.
@@ -827,7 +827,7 @@ retry:
 	 * position in the tree.
 	 */
 	__mem_cgroup_remove_exceeded(mz, mctz);
-	if (!res_counter_soft_limit_excess(&mz->memcg->res) ||
+	if (!res_counter_limit_excess(&mz->memcg->res, RES_SOFT_LIMIT) ||
 	    !css_tryget_online(&mz->memcg->css))
 		goto retry;
 done:
@@ -1983,7 +1983,7 @@ static int mem_cgroup_soft_reclaim(struct mem_cgroup *root_memcg,
 		.priority = 0,
 	};
 
-	excess = res_counter_soft_limit_excess(&root_memcg->res) >> PAGE_SHIFT;
+	excess = res_counter_limit_excess(&root_memcg->res, RES_SOFT_LIMIT) >> PAGE_SHIFT;
 
 	while (1) {
 		victim = mem_cgroup_iter(root_memcg, victim, &reclaim);
@@ -2014,7 +2014,7 @@ static int mem_cgroup_soft_reclaim(struct mem_cgroup *root_memcg,
 		total += mem_cgroup_shrink_node_zone(victim, gfp_mask, false,
 						     zone, &nr_scanned);
 		*total_scanned += nr_scanned;
-		if (!res_counter_soft_limit_excess(&root_memcg->res))
+		if (!res_counter_limit_excess(&root_memcg->res, RES_SOFT_LIMIT))
 			break;
 	}
 	mem_cgroup_iter_break(root_memcg, victim);
@@ -3941,7 +3941,7 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
 			} while (1);
 		}
 		__mem_cgroup_remove_exceeded(mz, mctz);
-		excess = res_counter_soft_limit_excess(&mz->memcg->res);
+		excess = res_counter_limit_excess(&mz->memcg->res, RES_SOFT_LIMIT);
 		/*
 		 * One school of thought says that we should not add
 		 * back the node to the tree if reclaim returns 0.
-- 
2.1.0.rc1

-- 
Michal Hocko
SUSE Labs
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