knfsd: Support adding transports by writing portlist file

Update the write handler for the portlist file to allow creating new
listening endpoints on a transport. The general form of the string is:

<transport_name><space><port number>

For example:

echo "tcp 2049" > /proc/fs/nfsd/portlist

This is intended to support the creation of a listening endpoint for
RDMA transports without adding #ifdef code to the nfssvc.c file.

Transports can also be removed as follows:

'-'<transport_name><space><port number>

For example:

echo "-tcp 2049" > /proc/fs/nfsd/portlist

Attempting to add a listener with an invalid transport string results
in EPROTONOSUPPORT and a perror string of "Protocol not supported".

Attempting to remove an non-existent listener (.e.g. bad proto or port)
results in ENOTCONN and a perror string of
"Transport endpoint is not connected"

Signed-off-by: Tom Tucker <[e-mail]>
Acked-by: Neil Brown <[e-mail]>
Reviewed-by: Chuck Lever <[e-mail]>
Reviewed-by: Greg Banks <[e-mail]>
Signed-off-by: J. Bruce Fields <[e-mail]>

fs/lockd/svc.c

···
 static int make_socks(struct svc_serv *serv, int proto)
 {
 	static int warned;
+	struct svc_xprt *xprt;
 	int err = 0;
 
-	if (proto == IPPROTO_UDP || nlm_udpport)
-		if (!svc_find_xprt(serv, "udp", 0, 0))
+	if (proto == IPPROTO_UDP || nlm_udpport) {
+		xprt = svc_find_xprt(serv, "udp", 0, 0);
+		if (!xprt)
 			err = svc_create_xprt(serv, "udp", nlm_udpport,
 					      SVC_SOCK_DEFAULTS);
-	if (err >= 0 && (proto == IPPROTO_TCP || nlm_tcpport))
-		if (!svc_find_xprt(serv, "tcp", 0, 0))
+		else
+			svc_xprt_put(xprt);
+	}
+	if (err >= 0 && (proto == IPPROTO_TCP || nlm_tcpport)) {
+		xprt = svc_find_xprt(serv, "tcp", 0, 0);
+		if (!xprt)
 			err = svc_create_xprt(serv, "tcp", nlm_tcpport,
 					      SVC_SOCK_DEFAULTS);
-
+		else
+			svc_xprt_put(xprt);
+	}
 	if (err >= 0) {
 		warned = 0;
 		err = 0;

fs/nfsd/nfsctl.c

···
 		}
 		return err < 0 ? err : 0;
 	}
-	if (buf[0] == '-') {
+	if (buf[0] == '-' && isdigit(buf[1])) {
 		char *toclose = kstrdup(buf+1, GFP_KERNEL);
 		int len = 0;
 		if (!toclose)
···
 			lockd_down();
 		kfree(toclose);
 		return len;
+	}
+	/*
+	 * Add a transport listener by writing it's transport name
+	 */
+	if (isalpha(buf[0])) {
+		int err;
+		char transport[16];
+		int port;
+		if (sscanf(buf, "%15s %4d", transport, &port) == 2) {
+			err = nfsd_create_serv();
+			if (!err) {
+				err = svc_create_xprt(nfsd_serv,
+						      transport, port,
+						      SVC_SOCK_ANONYMOUS);
+				if (err == -ENOENT)
+					/* Give a reasonable perror msg for
+					 * bad transport string */
+					err = -EPROTONOSUPPORT;
+			}
+			return err < 0 ? err : 0;
+		}
+	}
+	/*
+	 * Remove a transport by writing it's transport name and port number
+	 */
+	if (buf[0] == '-' && isalpha(buf[1])) {
+		struct svc_xprt *xprt;
+		int err = -EINVAL;
+		char transport[16];
+		int port;
+		if (sscanf(&buf[1], "%15s %4d", transport, &port) == 2) {
+			if (port == 0)
+				return -EINVAL;
+			lock_kernel();
+			if (nfsd_serv) {
+				xprt = svc_find_xprt(nfsd_serv, transport,
+						     AF_UNSPEC, port);
+				if (xprt) {
+					svc_close_xprt(xprt);
+					svc_xprt_put(xprt);
+					err = 0;
+				} else
+					err = -ENOTCONN;
+			}
+			unlock_kernel();
+			return err < 0 ? err : 0;
+		}
 	}
 	return -EINVAL;
 }

net/sunrpc/svc_xprt.c

···
 	clear_bit(XPT_BUSY, &xprt->xpt_flags);
 	svc_xprt_put(xprt);
 }
+EXPORT_SYMBOL_GPL(svc_close_xprt);
 
 void svc_close_all(struct list_head *xprt_list)
 {
···
 		if (port && port != svc_xprt_local_port(xprt))
 			continue;
 		found = xprt;
+		svc_xprt_get(xprt);
 		break;
 	}
 	spin_unlock_bh(&serv->sv_lock);