NFS4: Fix open bug when pnfs module blacklisted

Signed-off-by: NFred Isaman <iisaman@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/pnfs.h

@@ -365,7 +365,7 @@ static inline bool
 pnfs_use_threshold(struct nfs4_threshold **dst, struct nfs4_threshold *src,
 		   struct nfs_server *nfss)
 {
-	return (dst && src && src->bm != 0 &&
+	return (dst && src && src->bm != 0 && nfss->pnfs_curr_ld &&
 					nfss->pnfs_curr_ld->id == src->l_type);
 }