netconsole: Simplify send_fragmented_body()

Refactor send_fragmented_body() to use separate offset tracking for
msgbody, and extradata instead of complex conditional logic.
The previous implementation used boolean flags and calculated offsets
which made the code harder to follow.

The new implementation maintains independent offset counters
(msgbody_offset, extradata_offset) and processes each section
sequentially, making the data flow more straightforward and the code
easier to maintain.

This is a preparatory refactoring with no functional changes, which will
allow easily splitting extradata_complete into separate userdata and
sysdata buffers in the next patch.

Signed-off-by: Gustavo Luiz Duarte <gustavold@gmail.com>
Reviewed-by: Breno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/20251119-netconsole_dynamic_extradata-v3-1-497ac3191707@meta.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index bb6e03a929565b1439103ac67ba08f71003cc899..5fe5896d6ff52ac46511eed3143ba560f6a8a38f 100644 (file)
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -1560,89 +1560,70 @@ static void append_release(char *buf)
 }
 
 static void send_fragmented_body(struct netconsole_target *nt,
-                                const char *msgbody, int header_len,
+                                const char *msgbody_ptr, int header_len,
                                 int msgbody_len, int extradata_len)
 {
-       int sent_extradata, preceding_bytes;
-       const char *extradata = NULL;
-       int body_len, offset = 0;
+       const char *extradata_ptr = NULL;
+       int data_len, data_sent = 0;
+       int extradata_offset = 0;
+       int msgbody_offset = 0;
 
 #ifdef CONFIG_NETCONSOLE_DYNAMIC
-       extradata = nt->extradata_complete;
+       extradata_ptr = nt->extradata_complete;
 #endif
+       if (WARN_ON_ONCE(!extradata_ptr && extradata_len != 0))
+               return;
 
-       /* body_len represents the number of bytes that will be sent. This is
+       /* data_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
         */
-       body_len = msgbody_len + extradata_len;
+       data_len = msgbody_len + extradata_len;
 
        /* In each iteration of the while loop below, we send a packet
-        * containing the header and a portion of the body. The body is
+        * containing the header and a portion of the data. The data is
         * composed of two parts: msgbody and extradata. 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.
+        * many bytes have been sent so far using the data_sent variable, which
+        * ranges from 0 to the total bytes to be sent.
         */
-       while (offset < body_len) {
-               int this_header = header_len;
-               bool msgbody_written = false;
-               int this_offset = 0;
+       while (data_sent < data_len) {
+               int extradata_left = extradata_len - extradata_offset;
+               int msgbody_left = msgbody_len - msgbody_offset;
+               int buf_offset = 0;
                int this_chunk = 0;
 
-               this_header += scnprintf(nt->buf + this_header,
-                                        MAX_PRINT_CHUNK - this_header,
-                                        ",ncfrag=%d/%d;", offset,
-                                        body_len);
-
-               /* Not all msgbody data has been written yet */
-               if (offset < msgbody_len) {
-                       this_chunk = min(msgbody_len - offset,
-                                        MAX_PRINT_CHUNK - this_header);
-                       if (WARN_ON_ONCE(this_chunk <= 0))
-                               return;
-                       memcpy(nt->buf + this_header, msgbody + offset,
-                              this_chunk);
-                       this_offset += this_chunk;
+               /* header is already populated in nt->buf, just append to it */
+               buf_offset = header_len;
+
+               buf_offset += scnprintf(nt->buf + buf_offset,
+                                        MAX_PRINT_CHUNK - buf_offset,
+                                        ",ncfrag=%d/%d;", data_sent,
+                                        data_len);
+
+               /* append msgbody first */
+               this_chunk = min(msgbody_left, MAX_PRINT_CHUNK - buf_offset);
+               memcpy(nt->buf + buf_offset, msgbody_ptr + msgbody_offset,
+                      this_chunk);
+               msgbody_offset += this_chunk;
+               buf_offset += this_chunk;
+               data_sent += this_chunk;
+
+               /* after msgbody, append extradata */
+               if (extradata_ptr && extradata_left) {
+                       this_chunk = min(extradata_left,
+                                        MAX_PRINT_CHUNK - buf_offset);
+                       memcpy(nt->buf + buf_offset,
+                              extradata_ptr + extradata_offset, this_chunk);
+                       extradata_offset += this_chunk;
+                       buf_offset += this_chunk;
+                       data_sent += this_chunk;
                }
 
-               /* msgbody was finally written, either in the previous
-                * messages and/or in the current buf. Time to write
-                * the extradata.
-                */
-               msgbody_written |= offset + this_offset >= msgbody_len;
-
-               /* Msg body is fully written and there is pending extradata to
-                * write, append extradata in this chunk
-                */
-               if (msgbody_written && offset + this_offset < body_len) {
-                       /* Track how much user data was already sent. First
-                        * time here, sent_userdata is zero
-                        */
-                       sent_extradata = (offset + this_offset) - msgbody_len;
-                       /* offset of bytes used in current buf */
-                       preceding_bytes = this_chunk + this_header;
-
-                       if (WARN_ON_ONCE(sent_extradata < 0))
-                               return;
-
-                       this_chunk = min(extradata_len - sent_extradata,
-                                        MAX_PRINT_CHUNK - preceding_bytes);
-                       if (WARN_ON_ONCE(this_chunk < 0))
-                               /* this_chunk could be zero if all the previous
-                                * message used all the buffer. This is not a
-                                * problem, extradata will be sent in the next
-                                * iteration
-                                */
-                               return;
-
-                       memcpy(nt->buf + this_header + this_offset,
-                              extradata + sent_extradata,
-                              this_chunk);
-                       this_offset += this_chunk;
-               }
+               /* if all is good, send the packet out */
+               if (WARN_ON_ONCE(data_sent > data_len))
+                       return;
 
-               send_udp(nt, nt->buf, this_header + this_offset);
-               offset += this_offset;
+               send_udp(nt, nt->buf, buf_offset);
        }
 }