diff --git a/[refs] b/[refs]
index 4060f4375bb5..da23e976c591 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: a855b84c3d8c73220d4d3cd392a7bee7c83de70e
+refs/heads/master: 67589c71456b0346500629967292dea3802230b6
diff --git a/trunk/mm/percpu.c b/trunk/mm/percpu.c
index 2473ff06dc76..3bb810a72006 100644
--- a/trunk/mm/percpu.c
+++ b/trunk/mm/percpu.c
@@ -978,6 +978,17 @@ bool is_kernel_percpu_address(unsigned long addr)
  * address.  The caller is responsible for ensuring @addr stays valid
  * until this function finishes.
  *
+ * percpu allocator has special setup for the first chunk, which currently
+ * supports either embedding in linear address space or vmalloc mapping,
+ * and, from the second one, the backing allocator (currently either vm or
+ * km) provides translation.
+ *
+ * The addr can be tranlated simply without checking if it falls into the
+ * first chunk. But the current code reflects better how percpu allocator
+ * actually works, and the verification can discover both bugs in percpu
+ * allocator itself and per_cpu_ptr_to_phys() callers. So we keep current
+ * code.
+ *
  * RETURNS:
  * The physical address for @addr.
  */