NFSD: Add nfsd_clid_confirmed tracepoint

This replaces a dprintk call site in order to get greater visibility
on when client IDs are confirmed or re-used. Simple example:

            nfsd-995   [000]   126.622975: nfsd_compound:        xid=0x3a34e2b1 opcnt=1
            nfsd-995   [000]   126.623005: nfsd_cb_args:         addr=192.168.2.51:45901 client 60958e3b:9213ef0e prog=1073741824 ident=1
            nfsd-995   [000]   126.623007: nfsd_compound_status: op=1/1 OP_SETCLIENTID status=0
            nfsd-996   [001]   126.623142: nfsd_compound:        xid=0x3b34e2b1 opcnt=1
  >>>>      nfsd-996   [001]   126.623146: nfsd_clid_confirmed:  client 60958e3b:9213ef0e
            nfsd-996   [001]   126.623148: nfsd_cb_probe:        addr=192.168.2.51:45901 client 60958e3b:9213ef0e state=UNKNOWN
            nfsd-996   [001]   126.623154: nfsd_compound_status: op=1/1 OP_SETCLIENTID_CONFIRM status=0
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfs4state.c

@@ -2816,14 +2816,14 @@ move_to_confirmed(struct nfs4_client *clp)
 
 	lockdep_assert_held(&nn->client_lock);
 
-	dprintk("NFSD: move_to_confirm nfs4_client %p\n", clp);
 	list_move(&clp->cl_idhash, &nn->conf_id_hashtbl[idhashval]);
 	rb_erase(&clp->cl_namenode, &nn->unconf_name_tree);
 	add_clp_to_name_tree(clp, &nn->conf_name_tree);
-	if (!test_and_set_bit(NFSD4_CLIENT_CONFIRMED, &clp->cl_flags) &&
-	    clp->cl_nfsd_dentry &&
-	    clp->cl_nfsd_info_dentry)
+	if (!test_and_set_bit(NFSD4_CLIENT_CONFIRMED, &clp->cl_flags)) {
+		trace_nfsd_clid_confirmed(&clp->cl_clientid);
+		if (clp->cl_nfsd_dentry && clp->cl_nfsd_info_dentry)
 			fsnotify_dentry(clp->cl_nfsd_info_dentry, FS_MODIFY);
+	}
 	renew_client_locked(clp);
 }
 

fs/nfsd/trace.h

@@ -511,6 +511,7 @@ DEFINE_EVENT(nfsd_clientid_class, nfsd_clid_##name, \
 	TP_PROTO(const clientid_t *clid), \
 	TP_ARGS(clid))
 
+DEFINE_CLIENTID_EVENT(confirmed);
 DEFINE_CLIENTID_EVENT(expired);
 DEFINE_CLIENTID_EVENT(purged);
 DEFINE_CLIENTID_EVENT(renew);