pNFS: Add flag to track if we've called nfs4_ff_layout_stat_io_start_read/write

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

include/linux/nfs_xdr.h

@@ -1375,6 +1375,7 @@ enum {
 	NFS_IOHDR_ERROR = 0,
 	NFS_IOHDR_EOF,
 	NFS_IOHDR_REDO,
+	NFS_IOHDR_STAT,
 };
 
 struct nfs_pgio_header {
@@ -1454,6 +1455,7 @@ struct nfs_commit_data {
 	const struct rpc_call_ops *mds_ops;
 	const struct nfs_commit_completion_ops *completion_ops;
 	int (*commit_done_cb) (struct rpc_task *task, struct nfs_commit_data *data);
+	unsigned long		flags;
 };
 
 struct nfs_pgio_completion_ops {