NFSv4: Label stateids with the type

In order to more easily distinguish what kind of stateid we are dealing
with, introduce a type that can be used to label the stateid structure.

The label will be useful both for debugging, but also when dealing with
operations like SETATTR, READ and WRITE that can take several different
types of stateid as arguments.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index d854693..d630f9c 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -65,7 +65,10 @@
 
 #define OPENOWNER_POOL_SIZE	8
 
-const nfs4_stateid zero_stateid;
+const nfs4_stateid zero_stateid = {
+	.data = { 0 },
+	.type = NFS4_SPECIAL_STATEID_TYPE,
+};
 static DEFINE_MUTEX(nfs_clid_init_mutex);
 
 int nfs4_init_clientid(struct nfs_client *clp, struct rpc_cred *cred)