mm/memcg: Remove soft_limit_tree_node()

Opencode this one-line function in its three callers.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Howells <dhowells@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>

mm/memcontrol.c

@@ -456,12 +456,6 @@ ino_t page_cgroup_ino(struct page *page)
 	return ino;
 }
 
-static struct mem_cgroup_tree_per_node *
-soft_limit_tree_node(int nid)
-{
-	return soft_limit_tree.rb_tree_per_node[nid];
-}
-
 static void __mem_cgroup_insert_exceeded(struct mem_cgroup_per_node *mz,
 					 struct mem_cgroup_tree_per_node *mctz,
 					 unsigned long new_usage_in_excess)
@@ -538,7 +532,7 @@ static void mem_cgroup_update_tree(struct mem_cgroup *memcg, int nid)
 	struct mem_cgroup_per_node *mz;
 	struct mem_cgroup_tree_per_node *mctz;
 
-	mctz = soft_limit_tree_node(nid);
+	mctz = soft_limit_tree.rb_tree_per_node[nid];
 	if (!mctz)
 		return;
 	/*
@@ -577,7 +571,7 @@ static void mem_cgroup_remove_from_trees(struct mem_cgroup *memcg)
 
 	for_each_node(nid) {
 		mz = memcg->nodeinfo[nid];
-		mctz = soft_limit_tree_node(nid);
+		mctz = soft_limit_tree.rb_tree_per_node[nid];
 		if (mctz)
 			mem_cgroup_remove_exceeded(mz, mctz);
 	}
@@ -3364,7 +3358,7 @@ unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,
 	if (order > 0)
 		return 0;
 
-	mctz = soft_limit_tree_node(pgdat->node_id);
+	mctz = soft_limit_tree.rb_tree_per_node[pgdat->node_id];
 
 	/*
 	 * Do not even bother to check the largest node if the root