netconsole: extract message fragmentation into send_msg_udp()

Extract the message fragmentation logic from write_msg() into a
dedicated send_msg_udp() function. This improves code readability
and prepares for future enhancements.

The new send_msg_udp() function handles splitting messages that
exceed MAX_PRINT_CHUNK into smaller fragments and sending them
sequentially. This function is placed before send_ext_msg_udp()
to maintain a logical ordering of related functions.

No functional changes - this is purely a refactoring commit.

Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/20260206-nbcon-v7-2-62bda69b1b41@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: leitao

drivers/net/netconsole.c

@@ -1876,12 +1876,24 @@ static void write_ext_msg(struct console *con, const char *msg,
 	spin_unlock_irqrestore(&target_list_lock, flags);
 }
 
+static void send_msg_udp(struct netconsole_target *nt, const char *msg,
+			 unsigned int len)
+{
+	const char *tmp = msg;
+	int frag, left = len;
+
+	while (left > 0) {
+		frag = min(left, MAX_PRINT_CHUNK);
+		send_udp(nt, tmp, frag);
+		tmp += frag;
+		left -= frag;
+	}
+}
+
 static void write_msg(struct console *con, const char *msg, unsigned int len)
 {
-	int frag, left;
 	unsigned long flags;
 	struct netconsole_target *nt;
-	const char *tmp;
 
 	if (oops_only && !oops_in_progress)
 		return;
@@ -1899,13 +1911,7 @@ static void write_msg(struct console *con, const char *msg, unsigned int len)
 			 * at least one target if we die inside here, instead
 			 * of unnecessarily keeping all targets in lock-step.
 			 */
-			tmp = msg;
-			for (left = len; left;) {
-				frag = min(left, MAX_PRINT_CHUNK);
-				send_udp(nt, tmp, frag);
-				tmp += frag;
-				left -= frag;
-			}
+			send_msg_udp(nt, msg, len);
 		}
 	}
 	spin_unlock_irqrestore(&target_list_lock, flags);