Index: sys/kern/vfs_init.c
===================================================================
--- sys/kern/vfs_init.c	(revision 247000)
+++ sys/kern/vfs_init.c	(working copy)
@@ -130,13 +130,18 @@
 
 	/* Try to load the respective module. */
 	*error = kern_kldload(td, fstype, &fileid);
+	if (*error == EEXIST) {
+		*error = 0;
+		fileid = 0;
+	}
 	if (*error)
 		return (NULL);
 
 	/* Look up again to see if the VFS was loaded. */
 	vfsp = vfs_byname(fstype);
 	if (vfsp == NULL) {
-		(void)kern_kldunload(td, fileid, LINKER_UNLOAD_FORCE);
+		if (fileid != 0)
+			(void)kern_kldunload(td, fileid, LINKER_UNLOAD_FORCE);
 		*error = ENODEV;
 		return (NULL);
 	}
