NFSv4: Add tracepoints for debugging delegations

Set up tracepoints to track when delegations are set, reclaimed,
returned by the client, or recalled by the server.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 4b3ba92..cbbaee2 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -4802,6 +4802,7 @@
 	if (!nfs4_sequence_done(task, &data->res.seq_res))
 		return;
 
+	trace_nfs4_delegreturn_exit(&data->args, &data->res, task->tk_status);
 	switch (task->tk_status) {
 	case -NFS4ERR_STALE_STATEID:
 	case -NFS4ERR_EXPIRED:
@@ -4905,6 +4906,7 @@
 	int err;
 	do {
 		err = _nfs4_proc_delegreturn(inode, cred, stateid, issync);
+		trace_nfs4_delegreturn(inode, err);
 		switch (err) {
 			case -NFS4ERR_STALE_STATEID:
 			case -NFS4ERR_EXPIRED: