NFSD: Trace stateids returned via DELEGRETURN

Handing out a delegation stateid is recorded with the
nfsd_deleg_read tracepoint, but there isn't a matching tracepoint
for recording when the stateid is returned.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>

fs/nfsd/nfs4state.c

@@ -6917,6 +6917,7 @@ nfsd4_delegreturn(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	if (status)
 		goto put_stateid;
 
+	trace_nfsd_deleg_return(stateid);
 	wake_up_var(d_inode(cstate->current_fh.fh_dentry));
 	destroy_delegation(dp);
 put_stateid:

fs/nfsd/trace.h

@@ -604,6 +604,7 @@ DEFINE_STATEID_EVENT(layout_recall_release);
 
 DEFINE_STATEID_EVENT(open);
 DEFINE_STATEID_EVENT(deleg_read);
+DEFINE_STATEID_EVENT(deleg_return);
 DEFINE_STATEID_EVENT(deleg_recall);
 
 DECLARE_EVENT_CLASS(nfsd_stateseqid_class,