net: netconsole: split send_msg_fragmented

Refactor the send_msg_fragmented() function by extracting the logic for
sending the message body into a new function called
send_fragmented_body().

Now, send_msg_fragmented() handles appending the release and header, and
then delegates the task of breaking up the body and sending the
fragments to send_fragmented_body().

This is the final flow now:

When send_ext_msg_udp() is called to send a message, it will:
  - call send_msg_no_fragmentation() if no fragmentation is needed
  or
  - call send_msg_fragmented() if fragmentation is needed
    * send_msg_fragmented() appends the header to the buffer, which is
      be persisted until the function returns
      * call send_fragmented_body() to iterate and populate the body of
	the message. It will not touch the header, and it will only
	replace the body, writing the msgbody and/or userdata.

Also add some comment to make the code easier to review.

Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index b04d86fcea8ffca273265e10be1653040dd88f74..4ea44a2f48f7b1f9059d275f0f0edc40cc1997f0 100644 (file)
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -1096,46 +1096,30 @@ static void append_release(char *buf)
        scnprintf(buf, MAX_PRINT_CHUNK, "%s,", release);
 }
 
-static void send_msg_fragmented(struct netconsole_target *nt,
-                               const char *msg,
-                               int msg_len,
-                               int release_len)
+static void send_fragmented_body(struct netconsole_target *nt, char *buf,
+                                const char *msgbody, int header_len,
+                                int msgbody_len)
 {
-       int header_len, msgbody_len, body_len;
-       static char buf[MAX_PRINT_CHUNK]; /* protected by target_list_lock */
-       int offset = 0, userdata_len = 0;
-       const char *header, *msgbody;
        const char *userdata = NULL;
+       int body_len, offset = 0;
+       int userdata_len = 0;
 
 #ifdef CONFIG_NETCONSOLE_DYNAMIC
        userdata = nt->userdata_complete;
        userdata_len = nt->userdata_length;
 #endif
 
-       /* need to insert extra header fields, detect header and msgbody */
-       header = msg;
-       msgbody = memchr(msg, ';', msg_len);
-       if (WARN_ON_ONCE(!msgbody))
-               return;
-
-       header_len = msgbody - header;
-       msgbody_len = msg_len - header_len - 1;
-       msgbody++;
-
-       /*
-        * Transfer multiple chunks with the following extra header.
-        * "ncfrag=<byte-offset>/<total-bytes>"
+       /* body_len represents the number of bytes that will be sent. This is
+        * bigger than MAX_PRINT_CHUNK, thus, it will be split in multiple
+        * packets
         */
-       if (release_len)
-               append_release(buf);
-
-       /* Copy the header into the buffer */
-       memcpy(buf + release_len, header, header_len);
-       header_len += release_len;
-
        body_len = msgbody_len + userdata_len;
-       /* for now on, the header will be persisted, and the msgbody
-        * will be replaced
+
+       /* In each iteration of the while loop below, we send a packet
+        * containing the header and a portion of the body. The body is
+        * composed of two parts: msgbody and userdata. We keep track of how
+        * many bytes have been sent so far using the offset variable, which
+        * ranges from 0 to the total length of the body.
         */
        while (offset < body_len) {
                int this_header = header_len;
@@ -1144,7 +1128,7 @@ static void send_msg_fragmented(struct netconsole_target *nt,
                int this_chunk = 0;
 
                this_header += scnprintf(buf + this_header,
-                                        sizeof(buf) - this_header,
+                                        MAX_PRINT_CHUNK - this_header,
                                         ",ncfrag=%d/%d;", offset,
                                         body_len);
 
@@ -1199,6 +1183,41 @@ static void send_msg_fragmented(struct netconsole_target *nt,
        }
 }
 
+static void send_msg_fragmented(struct netconsole_target *nt,
+                               const char *msg,
+                               int msg_len,
+                               int release_len)
+{
+       static char buf[MAX_PRINT_CHUNK]; /* protected by target_list_lock */
+       int header_len, msgbody_len;
+       const char *msgbody;
+
+       /* need to insert extra header fields, detect header and msgbody */
+       msgbody = memchr(msg, ';', msg_len);
+       if (WARN_ON_ONCE(!msgbody))
+               return;
+
+       header_len = msgbody - msg;
+       msgbody_len = msg_len - header_len - 1;
+       msgbody++;
+
+       /*
+        * Transfer multiple chunks with the following extra header.
+        * "ncfrag=<byte-offset>/<total-bytes>"
+        */
+       if (release_len)
+               append_release(buf);
+
+       /* Copy the header into the buffer */
+       memcpy(buf + release_len, msg, header_len);
+       header_len += release_len;
+
+       /* for now on, the header will be persisted, and the msgbody
+        * will be replaced
+        */
+       send_fragmented_body(nt, buf, msgbody, header_len, msgbody_len);
+}
+
 /**
  * send_ext_msg_udp - send extended log message to target
  * @nt: target to send message to