On 22/02/2017 18:11, Michal Hocko wrote:

On Wed 22-02-17 16:58:11, Laurent Dufour wrote:
[...]

quoted

 static struct mem_cgroup_tree_per_node *
 soft_limit_tree_node(int nid)
 {

@@ -465,6 +497,8 @@ static void mem_cgroup_update_tree(struct mem_cgroup *memcg, struct page *page)
 	struct mem_cgroup_tree_per_node *mctz;
 
 	mctz = soft_limit_tree_from_page(page);
+	if (!mctz)
+		return;
 	/*
 	 * Necessary to update all ancestors when hierarchy is used.
 	 * because their event counter is not touched.

@@ -502,7 +536,8 @@ static void mem_cgroup_remove_from_trees(struct mem_cgroup *memcg)
 	for_each_node(nid) {
 		mz = mem_cgroup_nodeinfo(memcg, nid);
 		mctz = soft_limit_tree_node(nid);
-		mem_cgroup_remove_exceeded(mz, mctz);
+		if (mctz)
+			mem_cgroup_remove_exceeded(mz, mctz);
 	}
 }
 

this belongs to the previous patch, right?

It may. I made the first patch fixing the panic I saw but if you prefer
this to be part of the first one, fair enough.
Tell me what you like.