+/*
+ * A common holder for vdev_bdev_open() is used to relax the exclusive open
+ * semantics slightly. Internal vdev disk callers may pass VDEV_HOLDER to
+ * allow them to open the device multiple times. Other kernel callers and
+ * user space processes which don't pass this value will get EBUSY. This is
+ * currently required for the correct operation of hot spares.
+ */
+#define VDEV_HOLDER ((void *)0x2f5401de7)
+