sctp: change to save MSG_MORE flag into assoc

David Laight noticed the support for MSG_MORE with datamsg->force_delay
didn't really work as we expected, as the first msg with MSG_MORE set
would always block the following chunks' dequeuing.

This Patch is to rewrite it by saving the MSG_MORE flag into assoc as
David Laight suggested.

asoc->force_delay is used to save MSG_MORE flag before a msg is sent.
All chunks in queue would not be sent out if asoc->force_delay is set
by the msg with MSG_MORE flag, until a new msg without MSG_MORE flag
clears asoc->force_delay.

Note that this change would not affect the flush is generated by other
triggers, like asoc->state != ESTABLISHED, queue size > pmtu etc.

v1->v2:
  Not clear asoc->force_delay after sending the msg with MSG_MORE flag.

Fixes: 4ea0c32f5f42 ("sctp: add support for MSG_MORE")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: David Laight <david.laight@aculab.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sctp/structs.h

@@ -499,7 +499,6 @@ struct sctp_datamsg {
 	/* Did the messenge fail to send? */
 	int send_error;
 	u8 send_failed:1,
-	   force_delay:1,
 	   can_delay;	    /* should this message be Nagle delayed */
 };
 
@@ -1878,6 +1877,7 @@ struct sctp_association {
 
 	__u8 need_ecne:1,	/* Need to send an ECNE Chunk? */
 	     temp:1,		/* Is it a temporary association? */
+	     force_delay:1,
 	     prsctp_enable:1,
 	     reconf_enable:1;
 

net/sctp/output.c

@@ -704,7 +704,7 @@ static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet,
 	 */
 
 	if ((sctp_sk(asoc->base.sk)->nodelay || inflight == 0) &&
-	    !chunk->msg->force_delay)
+	    !asoc->force_delay)
 		/* Nothing unacked */
 		return SCTP_XMIT_OK;
 

net/sctp/socket.c

@@ -1965,7 +1965,7 @@ static int sctp_sendmsg(struct sock *sk, struct msghdr *msg, size_t msg_len)
 		err = PTR_ERR(datamsg);
 		goto out_free;
 	}
-	datamsg->force_delay = !!(msg->msg_flags & MSG_MORE);
+	asoc->force_delay = !!(msg->msg_flags & MSG_MORE);
 
 	/* Now send the (possibly) fragmented message. */
 	list_for_each_entry(chunk, &datamsg->chunks, frag_list) {