Index: sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_file.c
===================================================================
--- sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_file.c	(revision 274580)
+++ sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_file.c	(working copy)
@@ -129,6 +129,8 @@ skip_open:
 		return (error);
 	}
 
+	vd->vdev_notrim = B_TRUE;
+
 	*max_psize = *psize = vattr.va_size;
 	*logical_ashift = SPA_MINBLOCKSHIFT;
 	*physical_ashift = SPA_MINBLOCKSHIFT;