--- geom_subr.c.orig	Wed Jan  7 23:29:43 2004
+++ geom_subr.c	Thu Jan  8 09:43:31 2004
@@ -581,6 +581,7 @@
 	KASSERT(cp->acr + dcr >= 0, ("access resulting in negative acr"));
 	KASSERT(cp->acw + dcw >= 0, ("access resulting in negative acw"));
 	KASSERT(cp->ace + dce >= 0, ("access resulting in negative ace"));
+	KASSERT(dcr != 0 || dcw != 0 || dce != 0, ("NOP access request"));
 	KASSERT(pp->geom->access != NULL, ("NULL geom->access"));
 
 	/*