1 files changed, 58 insertions, 4 deletions

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 4ea44a2f48f7..86ab4a42769a 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -36,6 +36,7 @@
 #include <linux/inet.h>
 #include <linux/configfs.h>
 #include <linux/etherdevice.h>
+#include <linux/u64_stats_sync.h>
 #include <linux/utsname.h>
 #include <linux/rtnetlink.h>
 
@@ -90,6 +91,12 @@ static DEFINE_MUTEX(target_cleanup_list_lock);
  */
 static struct console netconsole_ext;
 
+struct netconsole_target_stats  {
+	u64_stats_t xmit_drop_count;
+	u64_stats_t enomem_count;
+	struct u64_stats_sync syncp;
+};
+
 /**
  * struct netconsole_target - Represents a configured netconsole target.
  * @list:	Links this target into the target_list.
@@ -97,6 +104,7 @@ static struct console netconsole_ext;
  * @userdata_group:	Links to the userdata configfs hierarchy
  * @userdata_complete:	Cached, formatted string of append
  * @userdata_length:	String length of userdata_complete
+ * @stats:	Packet send stats for the target. Used for debugging.
  * @enabled:	On / off knob to enable / disable target.
  *		Visible from userspace (read-write).
  *		We maintain a strict 1:1 correspondence between this and
@@ -124,6 +132,7 @@ struct netconsole_target {
 	char userdata_complete[MAX_USERDATA_ENTRY_LENGTH * MAX_USERDATA_ITEMS];
 	size_t			userdata_length;
 #endif
+	struct netconsole_target_stats stats;
 	bool			enabled;
 	bool			extended;
 	bool			release;
@@ -262,6 +271,7 @@ static void netconsole_process_cleanups_core(void)
  *				|	remote_ip
  *				|	local_mac
  *				|	remote_mac
+ *				|	transmit_errors
  *				|	userdata/
  *				|		<key>/
  *				|			value
@@ -371,6 +381,21 @@ static ssize_t remote_mac_show(struct config_item *item, char *buf)
 	return sysfs_emit(buf, "%pM\n", to_target(item)->np.remote_mac);
 }
 
+static ssize_t transmit_errors_show(struct config_item *item, char *buf)
+{
+	struct netconsole_target *nt = to_target(item);
+	u64 xmit_drop_count, enomem_count;
+	unsigned int start;
+
+	do {
+		start = u64_stats_fetch_begin(&nt->stats.syncp);
+		xmit_drop_count = u64_stats_read(&nt->stats.xmit_drop_count);
+		enomem_count = u64_stats_read(&nt->stats.enomem_count);
+	} while (u64_stats_fetch_retry(&nt->stats.syncp, start));
+
+	return sysfs_emit(buf, "%llu\n", xmit_drop_count + enomem_count);
+}
+
 /*
  * This one is special -- targets created through the configfs interface
  * are not enabled (and the corresponding netpoll activated) by default.
@@ -705,7 +730,7 @@ static void update_userdata(struct netconsole_target *nt)
 		struct userdatum *udm_item;
 		struct config_item *item;
 
-		if (child_count >= MAX_USERDATA_ITEMS)
+		if (WARN_ON_ONCE(child_count >= MAX_USERDATA_ITEMS))
 			break;
 		child_count++;
 
@@ -842,6 +867,7 @@ CONFIGFS_ATTR(, remote_ip);
 CONFIGFS_ATTR_RO(, local_mac);
 CONFIGFS_ATTR(, remote_mac);
 CONFIGFS_ATTR(, release);
+CONFIGFS_ATTR_RO(, transmit_errors);
 
 static struct configfs_attribute *netconsole_target_attrs[] = {
 	&attr_enabled,
@@ -854,6 +880,7 @@ static struct configfs_attribute *netconsole_target_attrs[] = {
 	&attr_remote_ip,
 	&attr_local_mac,
 	&attr_remote_mac,
+	&attr_transmit_errors,
 	NULL,
 };
 
@@ -1058,6 +1085,33 @@ static struct notifier_block netconsole_netdev_notifier = {
 	.notifier_call  = netconsole_netdev_event,
 };
 
+/**
+ * send_udp - Wrapper for netpoll_send_udp that counts errors
+ * @nt: target to send message to
+ * @msg: message to send
+ * @len: length of message
+ *
+ * Calls netpoll_send_udp and classifies the return value. If an error
+ * occurred it increments statistics in nt->stats accordingly.
+ * Only calls netpoll_send_udp if CONFIG_NETCONSOLE_DYNAMIC is disabled.
+ */
+static void send_udp(struct netconsole_target *nt, const char *msg, int len)
+{
+	int result = netpoll_send_udp(&nt->np, msg, len);
+
+	if (IS_ENABLED(CONFIG_NETCONSOLE_DYNAMIC)) {
+		if (result == NET_XMIT_DROP) {
+			u64_stats_update_begin(&nt->stats.syncp);
+			u64_stats_inc(&nt->stats.xmit_drop_count);
+			u64_stats_update_end(&nt->stats.syncp);
+		} else if (result == -ENOMEM) {
+			u64_stats_update_begin(&nt->stats.syncp);
+			u64_stats_inc(&nt->stats.enomem_count);
+			u64_stats_update_end(&nt->stats.syncp);
+		}
+	}
+}
+
 static void send_msg_no_fragmentation(struct netconsole_target *nt,
 				      const char *msg,
 				      int msg_len,
@@ -1085,7 +1139,7 @@ static void send_msg_no_fragmentation(struct netconsole_target *nt,
 				     MAX_PRINT_CHUNK - msg_len,
 				     "%s", userdata);
 
-	netpoll_send_udp(&nt->np, buf, msg_len);
+	send_udp(nt, buf, msg_len);
 }
 
 static void append_release(char *buf)
@@ -1178,7 +1232,7 @@ static void send_fragmented_body(struct netconsole_target *nt, char *buf,
 			this_offset += this_chunk;
 		}
 
-		netpoll_send_udp(&nt->np, buf, this_header + this_offset);
+		send_udp(nt, buf, this_header + this_offset);
 		offset += this_offset;
 	}
 }
@@ -1288,7 +1342,7 @@ static void write_msg(struct console *con, const char *msg, unsigned int len)
 			tmp = msg;
 			for (left = len; left;) {
 				frag = min(left, MAX_PRINT_CHUNK);
-				netpoll_send_udp(&nt->np, tmp, frag);
+				send_udp(nt, tmp, frag);
 				tmp += frag;
 				left -= frag;
 			}