svc: Add /proc/sys/sunrpc/transport files

Add a file that when read lists the set of registered svc
transports.
Signed-off-by: Tom Tucker <tom@opengridcomputing.com>
Acked-by: Neil Brown <neilb@suse.de>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Greg Banks <gnb@sgi.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

include/linux/sunrpc/svc_xprt.h

@@ -79,6 +79,7 @@ void	svc_xprt_copy_addrs(struct svc_rqst *rqstp, struct svc_xprt *xprt);
 void	svc_close_xprt(struct svc_xprt *xprt);
 void	svc_delete_xprt(struct svc_xprt *xprt);
 int	svc_port_is_privileged(struct sockaddr *sin);
+int	svc_print_xprts(char *buf, int maxlen);
 
 static inline void svc_xprt_get(struct svc_xprt *xprt)
 {

net/sunrpc/svc_xprt.c

@@ -112,6 +112,34 @@ void svc_unreg_xprt_class(struct svc_xprt_class *xcl)
 }
 EXPORT_SYMBOL_GPL(svc_unreg_xprt_class);
 
+/*
+ * Format the transport list for printing
+ */
+int svc_print_xprts(char *buf, int maxlen)
+{
+	struct list_head *le;
+	char tmpstr[80];
+	int len = 0;
+	buf[0] = '\0';
+
+	spin_lock(&svc_xprt_class_lock);
+	list_for_each(le, &svc_xprt_class_list) {
+		int slen;
+		struct svc_xprt_class *xcl =
+			list_entry(le, struct svc_xprt_class, xcl_list);
+
+		sprintf(tmpstr, "%s %d\n", xcl->xcl_name, xcl->xcl_max_payload);
+		slen = strlen(tmpstr);
+		if (len + slen > maxlen)
+			break;
+		len += slen;
+		strcat(buf, tmpstr);
+	}
+	spin_unlock(&svc_xprt_class_lock);
+
+	return len;
+}
+
 static void svc_xprt_free(struct kref *kref)
 {
 	struct svc_xprt *xprt =

net/sunrpc/sysctl.c

@@ -18,6 +18,7 @@
 #include <linux/sunrpc/types.h>
 #include <linux/sunrpc/sched.h>
 #include <linux/sunrpc/stats.h>
+#include <linux/sunrpc/svc_xprt.h>
 
 /*
  * Declare the debug flags here
@@ -55,6 +56,30 @@ rpc_unregister_sysctl(void)
 	}
 }
 
+static int proc_do_xprt(ctl_table *table, int write, struct file *file,
+			void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+	char tmpbuf[256];
+	int len;
+	if ((*ppos && !write) || !*lenp) {
+		*lenp = 0;
+		return 0;
+	}
+	if (write)
+		return -EINVAL;
+	else {
+		len = svc_print_xprts(tmpbuf, sizeof(tmpbuf));
+		if (!access_ok(VERIFY_WRITE, buffer, len))
+			return -EFAULT;
+
+		if (__copy_to_user(buffer, tmpbuf, len))
+			return -EFAULT;
+	}
+	*lenp -= len;
+	*ppos += len;
+	return 0;
+}
+
 static int
 proc_dodebug(ctl_table *table, int write, struct file *file,
 				void __user *buffer, size_t *lenp, loff_t *ppos)
@@ -147,6 +172,12 @@ static ctl_table debug_table[] = {
 		.mode		= 0644,
 		.proc_handler	= &proc_dodebug
 	},
+	{
+		.procname	= "transports",
+		.maxlen		= 256,
+		.mode		= 0444,
+		.proc_handler	= &proc_do_xprt,
+	},
 	{ .ctl_name = 0 }
 };