[PATCH] mm: fix vm-scalability regression in cgroup-aware workingset code fix

[Johannes Weiner]

Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
---
 include/linux/mm.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index b21e5f30378e..97065e1f0237 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -975,6 +975,7 @@ static inline struct mem_cgroup *page_memcg(struct page *page)
 }
 static inline struct mem_cgroup *page_memcg_rcu(struct page *page)
 {
+	WARN_ON_ONCE(!rcu_read_lock_held());
 	return READ_ONCE(page->mem_cgroup);
 }
 #else
@@ -984,6 +985,7 @@ static inline struct mem_cgroup *page_memcg(struct page *page)
 }
 static inline struct mem_cgroup *page_memcg_rcu(struct page *page)
 {
+	WARN_ON_ONCE(!rcu_read_lock_held());
 	return NULL;
 }
 #endif
-- 
2.9.0