Index: kern_shutdown.c
===================================================================
--- kern_shutdown.c	(revision 284158)
+++ kern_shutdown.c	(working copy)
@@ -136,6 +136,10 @@
 SYSCTL_INT(_kern_shutdown, OID_AUTO, show_busybufs, CTLFLAG_RW,
 	&show_busybufs, 0, "");
 
+int show_umountfs;
+SYSCTL_INT(_kern_shutdown, OID_AUTO, show_umountfs, CTLFLAG_RW,
+	&show_umountfs, 0, "Print the unmounted filesystems at shutdown");
+
 /*
  * Variable panicstr contains argument to first call to panic; used as flag
  * to indicate that the kernel has already called panic.
Index: vfs_subr.c
===================================================================
--- vfs_subr.c	(revision 284158)
+++ vfs_subr.c	(working copy)
@@ -3483,6 +3483,8 @@
     "");
 #endif
 
+extern int show_umountfs;
+
 /*
  * Unmount all filesystems. The list is traversed in reverse order
  * of mounting to avoid dependencies.
@@ -3503,7 +3505,15 @@
 	while(!TAILQ_EMPTY(&mountlist)) {
 		mp = TAILQ_LAST(&mountlist, mntlist);
 		vfs_ref(mp);
+		if (show_umountfs)
+			printf("Unmounting %s (%s)...", mp->mnt_stat.f_mntonname,
+				mp->mnt_vfc->vfc_name);
 		error = dounmount(mp, MNT_FORCE, td);
+		if (show_umountfs) {
+			if (error == 0)
+				printf("done");
+			printf("\n");
+			}
 		if (error != 0) {
 			TAILQ_REMOVE(&mountlist, mp, mnt_list);
 			/*