NFSD: Add nfsd_clid_verf_mismatch tracepoint

Record when a client presents a different boot verifier than the
one we know about. Typically this is a sign the client has
rebooted, but sometimes it signals a conflicting client ID, which
the client's administrator will need to address.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfs4state.c

@@ -3191,6 +3191,7 @@ nfsd4_exchange_id(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 			goto out_copy;
 		}
 		/* case 5, client reboot */
+		trace_nfsd_clid_verf_mismatch(conf, rqstp, &verf);
 		conf = NULL;
 		goto out_new;
 	}
@@ -3986,9 +3987,13 @@ nfsd4_setclientid(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	if (unconf)
 		unhash_client_locked(unconf);
 	/* We need to handle only case 1: probable callback update */
-	if (conf && same_verf(&conf->cl_verifier, &clverifier)) {
-		copy_clid(new, conf);
-		gen_confirm(new, nn);
+	if (conf) {
+		if (same_verf(&conf->cl_verifier, &clverifier)) {
+			copy_clid(new, conf);
+			gen_confirm(new, nn);
+		} else
+			trace_nfsd_clid_verf_mismatch(conf, rqstp,
+						      &clverifier);
 	}
 	new->cl_minorversion = 0;
 	gen_callback(new, setclid, rqstp);

fs/nfsd/trace.h

@@ -564,6 +564,38 @@ TRACE_EVENT(nfsd_clid_cred_mismatch,
 	)
 )
 
+TRACE_EVENT(nfsd_clid_verf_mismatch,
+	TP_PROTO(
+		const struct nfs4_client *clp,
+		const struct svc_rqst *rqstp,
+		const nfs4_verifier *verf
+	),
+	TP_ARGS(clp, rqstp, verf),
+	TP_STRUCT__entry(
+		__field(u32, cl_boot)
+		__field(u32, cl_id)
+		__array(unsigned char, cl_verifier, NFS4_VERIFIER_SIZE)
+		__array(unsigned char, new_verifier, NFS4_VERIFIER_SIZE)
+		__array(unsigned char, addr, sizeof(struct sockaddr_in6))
+	),
+	TP_fast_assign(
+		__entry->cl_boot = clp->cl_clientid.cl_boot;
+		__entry->cl_id = clp->cl_clientid.cl_id;
+		memcpy(__entry->cl_verifier, (void *)&clp->cl_verifier,
+		       NFS4_VERIFIER_SIZE);
+		memcpy(__entry->new_verifier, (void *)verf,
+		       NFS4_VERIFIER_SIZE);
+		memcpy(__entry->addr, &rqstp->rq_xprt->xpt_remote,
+			sizeof(struct sockaddr_in6));
+	),
+	TP_printk("client %08x:%08x verf=0x%s, updated=0x%s from addr=%pISpc",
+		__entry->cl_boot, __entry->cl_id,
+		__print_hex_str(__entry->cl_verifier, NFS4_VERIFIER_SIZE),
+		__print_hex_str(__entry->new_verifier, NFS4_VERIFIER_SIZE),
+		__entry->addr
+	)
+);
+
 TRACE_EVENT(nfsd_clid_inuse_err,
 	TP_PROTO(const struct nfs4_client *clp),
 	TP_ARGS(clp),