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 <tom@opengridcomputing.com>
---

 fs/nfsd/nfsctl.c      |   52 ++++++++++++++++++++++++++++++++++++++++++++++++-
 net/sunrpc/svc_xprt.c |    1 +
 2 files changed, 52 insertions(+), 1 deletions(-)

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 77dc989..5b9ed0e 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -540,7 +540,7 @@ static ssize_t write_ports(struct file *file, char *buf, size_t size)
 		}
 		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)
@@ -554,6 +554,56 @@ static ssize_t write_ports(struct file *file, char *buf, size_t size)
 		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) {
+				if (svc_find_xprt(nfsd_serv, transport,
+						  AF_UNSPEC, port))
+					return -EADDRINUSE;
+
+				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);
+					err = 0;
+				} else
+					err = -ENOTCONN;
+			}
+			unlock_kernel();
+			return err < 0 ? err : 0;
+		}
+	}
 	return -EINVAL;
 }
 
diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index 9815c6f..6708aa2 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -827,6 +827,7 @@ void svc_close_xprt(struct svc_xprt *xprt)
 	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)
 {
-
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