# define MS_DETACH 0x00000002
#endif /* MNT_DETACH */
+/*
+ * Overlay mount is default in Linux, but for solaris/zfs
+ * compatibility, MS_OVERLAY is defined to explicitly have the user
+ * provide a flag (-O) to mount over a non empty directory.
+ */
+#define MS_OVERLAY 0x00000004
+
#endif /* _LIBSPL_SYS_MOUNT_H */