Add linux kernel disk support

Native Linux vdev disk interfaces

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

module/zfs/vdev.c

@@ -1069,6 +1069,15 @@ vdev_open_child(void *arg)
 boolean_t
 vdev_uses_zvols(vdev_t *vd)
 {
+/*
+ * Stacking zpools on top of zvols is unsupported until we implement a method
+ * for determining if an arbitrary block device is a zvol without using the
+ * path.  Solaris would check the 'zvol' path component but this does not
+ * exist in the Linux port, so we really should do something like stat the
+ * file and check the major number.  This is complicated by the fact that
+ * we need to do this portably in user or kernel space.
+ */
+#if 0
 	int c;
 
 	if (vd->vdev_path && strncmp(vd->vdev_path, ZVOL_DIR,
@@ -1077,6 +1086,7 @@ vdev_uses_zvols(vdev_t *vd)
 	for (c = 0; c < vd->vdev_children; c++)
 		if (vdev_uses_zvols(vd->vdev_child[c]))
 			return (B_TRUE);
+#endif
 	return (B_FALSE);
 }