NFSv4: Ensure we do not reuse open owner names

The NFSv4 spec is ambiguous about whether or not it is permissible
to reuse open owner names, so play it safe. This patch adds a timestamp
to the state_owner structure, and combines that with the IDA based
uniquifier.
Fixes a regression whereby the Linux server returns NFS4ERR_BAD_SEQID.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index bfd0d1b..7ba3551 100644
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -312,6 +312,11 @@
 	int rpc_status;
 };
 
+struct stateowner_id {
+	__u64	create_time;
+	__u32	uniquifier;
+};
+
 /*
  * Arguments to the open call.
  */
@@ -321,7 +326,7 @@
 	int			open_flags;
 	fmode_t			fmode;
 	__u64                   clientid;
-	__u64                   id;
+	struct stateowner_id	id;
 	union {
 		struct {
 			struct iattr *  attrs;    /* UNCHECKED, GUARDED */