diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index acb93c554f6e..1af057575ce9 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5965,7 +5965,13 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
 	if (!mem_cgroup_is_root(memcg))
 		page_counter_uncharge(&memcg->memory, 1);
 
-	/* Caller disabled preemption with mapping->tree_lock */
+	/*
+	 * Interrupts should be disabled here because the caller holds the
+	 * mapping->tree_lock lock which is taken with interrupts-off. It is
+	 * important here to have the interrupts disabled because it is the
+	 * only synchronisation we have for udpating the per-CPU variables.
+	 */
+	VM_BUG_ON(!irqs_disabled());
 	mem_cgroup_charge_statistics(memcg, page, -1);
 	memcg_check_events(memcg, page);
 }