android.os.storage.cts.StorageManagerTest#testMountAndUnmountObbNormal  fail     junit.framework.AssertionFailedError: OBB should be mounted
android.os.storage.cts.StorageManagerTest#testMountAndUnmountTwoObbs    fail    junit.framework.AssertionFailedError: OBB should be mounted

可以查一下kernel下面的CONFIG_BLK_DEV_LOOP這個巨集有沒有開，沒有開就不會建立loop裝置

kernel\msm-3.18\arch\arm\configs\msm8909-perf_defconfig
kernel\msm-3.18\arch\arm\configs\msm8909w_defconfig
CONFIG_BLK_DEV_LOOP=y

另外，就是sepolicy的問題：
kernel.te
+
+# MTP sync (b/15835289)
+# kernel thread "loop0", used by the loop block device, for ASECs (b/17158723)
+allow kernel priv_app:fd use;
+allow kernel untrusted_app:fd use;
+allow kernel sdcard_type:file { read write };
+
+# Allow the kernel to read OBB files from app directories. (b/17428116)
+# Kernel thread "loop0" reads a vold supplied file descriptor.
+# Fixes CTS tests:
+#  * android.os.storage.cts.StorageManagerTest#testMountAndUnmountObbNormal
+#  * android.os.storage.cts.StorageManagerTest#testMountAndUnmountTwoObbs
+allow kernel vold:fd use;
+allow kernel app_data_file:file read;
+allow kernel asec_image_file:file read;
+
+domain_auto_trans(kernel, init_exec, init)