diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index f4b635526345..97ef2a9d878d 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -319,6 +319,11 @@ EXPORT_SYMBOL_GPL(dax_alive);
  * that any fault handlers or operations that might have seen
  * dax_alive(), have completed.  Any operations that start after
  * synchronize_srcu() has run will abort upon seeing !dax_alive().
+ *
+ * Note, because alloc_dax() returns an ERR_PTR() on error, callers
+ * typically store its result into a local variable in order to check
+ * the result. Therefore, care must be taken to populate the struct
+ * device dax_dev field make sure the dax_dev is not leaked.
  */
 void kill_dax(struct dax_device *dax_dev)
 {
diff --git a/include/linux/dax.h b/include/linux/dax.h
index e3ffe7c7f01d..9d3e3327af4c 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -88,11 +88,7 @@ static inline void *dax_holder(struct dax_device *dax_dev)
 static inline struct dax_device *alloc_dax(void *private,
 		const struct dax_operations *ops)
 {
-	/*
-	 * Callers should check IS_ENABLED(CONFIG_DAX) to know if this
-	 * NULL is an error or expected.
-	 */
-	return NULL;
+	return ERR_PTR(-EOPNOTSUPP);
 }
 static inline void put_dax(struct dax_device *dax_dev)
 {