NFSD: Add nfsd_clid_destroyed tracepoint

Record client-requested termination of client IDs.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfs4state.c

@@ -3907,6 +3907,7 @@ nfsd4_destroy_clientid(struct svc_rqst *rqstp,
 		status = nfserr_wrong_cred;
 		goto out;
 	}
+	trace_nfsd_clid_destroyed(&clp->cl_clientid);
 	unhash_client_locked(clp);
 out:
 	spin_unlock(&nn->client_lock);

fs/nfsd/trace.h

@@ -513,6 +513,7 @@ DEFINE_EVENT(nfsd_clientid_class, nfsd_clid_##name, \
 
 DEFINE_CLIENTID_EVENT(reclaim_complete);
 DEFINE_CLIENTID_EVENT(confirmed);
+DEFINE_CLIENTID_EVENT(destroyed);
 DEFINE_CLIENTID_EVENT(expired);
 DEFINE_CLIENTID_EVENT(purged);
 DEFINE_CLIENTID_EVENT(renew);