SUNRPC: pass buffer size to svc_sock_names()

Adjust the synopsis of svc_sock_names() to pass in the size of the
output buffer.  Add a documenting comment.

This is a cosmetic change for now.  A subsequent patch will make sure
the buffer length is passed to one_sock_name(), where the length will
actually be useful.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

fs/nfsd/nfsctl.c

@@ -966,7 +966,8 @@ static ssize_t __write_ports_delfd(char *buf)
 		return -ENOMEM;
 
 	if (nfsd_serv != NULL)
-		len = svc_sock_names(buf, nfsd_serv, toclose);
+		len = svc_sock_names(nfsd_serv, buf,
+					SIMPLE_TRANSACTION_LIMIT, toclose);
 	if (len >= 0)
 		lockd_down();
 

include/linux/sunrpc/svcsock.h

@@ -38,7 +38,9 @@ int		svc_recv(struct svc_rqst *, long);
 int		svc_send(struct svc_rqst *);
 void		svc_drop(struct svc_rqst *);
 void		svc_sock_update_bufs(struct svc_serv *serv);
-int		svc_sock_names(char *buf, struct svc_serv *serv, char *toclose);
+int		svc_sock_names(struct svc_serv *serv, char *buf,
+					const size_t buflen,
+					const char *toclose);
 int		svc_addsock(struct svc_serv *serv, const int fd,
 					char *name_return, const size_t len);
 void		svc_init_xprt_sock(void);

net/sunrpc/svcsock.c

@@ -259,8 +259,23 @@ static int one_sock_name(char *buf, struct svc_sock *svsk)
 	return len;
 }
 
-int
-svc_sock_names(char *buf, struct svc_serv *serv, char *toclose)
+/**
+ * svc_sock_names - construct a list of listener names in a string
+ * @serv: pointer to RPC service
+ * @buf: pointer to a buffer to fill in with socket names
+ * @buflen: size of the buffer to be filled
+ * @toclose: pointer to '\0'-terminated C string containing the name
+ *		of a listener to be closed
+ *
+ * Fills in @buf with a '\n'-separated list of names of listener
+ * sockets.  If @toclose is not NULL, the socket named by @toclose
+ * is closed, and is not included in the output list.
+ *
+ * Returns positive length of the socket name string, or a negative
+ * errno value on error.
+ */
+int svc_sock_names(struct svc_serv *serv, char *buf, const size_t buflen,
+		   const char *toclose)
 {
 	struct svc_sock *svsk, *closesk = NULL;
 	int len = 0;