sctp: Tag messages that can be Nagle delayed at creation.

When we create the sctp_datamsg and fragment the user data,
we know exactly if we are sending full segments or not and
how they might be bundled.  During this time, we can mark
messages a Nagle capable or not.  This makes the check at
transmit time much simpler.
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>

include/net/sctp/structs.h

@@ -643,17 +643,15 @@ struct sctp_pf {
 struct sctp_datamsg {
 	/* Chunks waiting to be submitted to lower layer. */
 	struct list_head chunks;
-	/* Chunks that have been transmitted. */
-	size_t msg_size;
 	/* Reference counting. */
 	atomic_t refcnt;
 	/* When is this message no longer interesting to the peer? */
 	unsigned long expires_at;
 	/* Did the messenge fail to send? */
 	int send_error;
-	char send_failed;
-	/* Control whether chunks from this message can be abandoned. */
-	char can_abandon;
+	u8 send_failed:1,
+	   can_abandon:1,   /* can chunks from this message can be abandoned. */
+	   can_delay;	    /* should this message be Nagle delayed */
 };
 
 struct sctp_datamsg *sctp_datamsg_from_user(struct sctp_association *,

net/sctp/chunk.c

@@ -58,9 +58,9 @@ static void sctp_datamsg_init(struct sctp_datamsg *msg)
 	msg->send_failed = 0;
 	msg->send_error = 0;
 	msg->can_abandon = 0;
+	msg->can_delay = 1;
 	msg->expires_at = 0;
 	INIT_LIST_HEAD(&msg->chunks);
-	msg->msg_size = 0;
 }
 
 /* Allocate and initialize datamsg. */
@@ -157,7 +157,6 @@ static void sctp_datamsg_assign(struct sctp_datamsg *msg, struct sctp_chunk *chu
 {
 	sctp_datamsg_hold(msg);
 	chunk->msg = msg;
-	msg->msg_size += chunk->skb->len;
 }
 
 
@@ -247,6 +246,7 @@ struct sctp_datamsg *sctp_datamsg_from_user(struct sctp_association *asoc,
 	if (msg_len >= first_len) {
 		msg_len -= first_len;
 		whole = 1;
+		msg->can_delay = 0;
 	}
 
 	/* How many full sized?  How many bytes leftover? */

net/sctp/output.c

@@ -674,7 +674,7 @@ static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet,
 		 * Don't delay large message writes that may have been
 		 * fragmeneted into small peices.
 		 */
-		if ((len < max) && (chunk->msg->msg_size < max)) {
+		if ((len < max) && chunk->msg->can_delay) {
 			retval = SCTP_XMIT_NAGLE_DELAY;
 			goto finish;
 		}