Possibility to physically reserve space without writing leaf blocks

@@ -219,6 +219,11 @@
 
         zfeature_register(SPA_FEATURE_EMBEDDED_DATA,
             "com.delphix:embedded_data", "embedded_data",
             "Blocks which compress very well use even less space.",
             B_FALSE, B_TRUE, B_TRUE, NULL);
+
+        zfeature_register(SPA_FEATURE_SPACE_RESERVATION,
+            "org.nexenta:space_reservation", "space_reservation",
+            "Possibility to physically reserve space on disk", B_FALSE, B_FALSE,
+            B_FALSE, NULL);
 }