nfsd4: clean up validate_stateid

The logic here is better expressed with a switch statement.

While we're here, CLOSED stateids (or stateids of an unkown type--which
would indicate a server bug) should probably return nfserr_bad_stateid,
though this behavior shouldn't affect any non-buggy client.
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfs4state.c

@@ -3456,13 +3456,22 @@ static __be32 nfsd4_validate_stateid(struct nfs4_client *cl, stateid_t *stateid)
 	status = check_stateid_generation(stateid, &s->sc_stateid, 1);
 	if (status)
 		return status;
-	if (!(s->sc_type & (NFS4_OPEN_STID | NFS4_LOCK_STID)))
+	switch (s->sc_type) {
+	case NFS4_DELEG_STID:
 		return nfs_ok;
+	case NFS4_OPEN_STID:
+	case NFS4_LOCK_STID:
 		ols = openlockstateid(s);
 		if (ols->st_stateowner->so_is_open_owner
-	    && !(openowner(ols->st_stateowner)->oo_flags & NFS4_OO_CONFIRMED))
+	    			&& !(openowner(ols->st_stateowner)->oo_flags
+						& NFS4_OO_CONFIRMED))
 			return nfserr_bad_stateid;
 		return nfs_ok;
+	default:
+		printk("unknown stateid type %x\n", s->sc_type);
+	case NFS4_CLOSED_STID:
+		return nfserr_bad_stateid;
+	}
 }
 
 static __be32 nfsd4_lookup_stateid(stateid_t *stateid, unsigned char typemask,