ceph: carry explicit msg reference for currently sending message

Carry a ceph_msg reference for connection->out_msg.  This will allow us to
make out_sent optional.
Signed-off-by: Sage Weil <sage@newdream.net>

fs/ceph/messenger.c

@@ -322,7 +322,10 @@ static void reset_connection(struct ceph_connection *con)
 
 	con->connect_seq = 0;
 	con->out_seq = 0;
-	con->out_msg = NULL;
+	if (con->out_msg) {
+		ceph_msg_put(con->out_msg);
+		con->out_msg = NULL;
+	}
 	con->in_seq = 0;
 	mutex_unlock(&con->out_mutex);
 }
@@ -423,7 +426,7 @@ static void prepare_write_message_footer(struct ceph_connection *con, int v)
 	con->out_kvec_bytes += sizeof(m->footer);
 	con->out_kvec_left++;
 	con->out_more = m->more_to_follow;
-	con->out_msg = NULL;   /* we're done with this one */
+	con->out_msg_done = true;
 }
 
 /*
@@ -436,6 +439,7 @@ static void prepare_write_message(struct ceph_connection *con)
 
 	con->out_kvec_bytes = 0;
 	con->out_kvec_is_msg = true;
+	con->out_msg_done = false;
 
 	/* Sneak an ack in there first?  If we can get it into the same
 	 * TCP packet that's a good thing. */
@@ -452,8 +456,9 @@ static void prepare_write_message(struct ceph_connection *con)
 	/* move message to sending/sent list */
 	m = list_first_entry(&con->out_queue,
 		       struct ceph_msg, list_head);
+	con->out_msg = m;
+	ceph_msg_get(m);
 	list_move_tail(&m->list_head, &con->out_sent);
-	con->out_msg = m;   /* we don't bother taking a reference here. */
 
 	m->hdr.seq = cpu_to_le64(++con->out_seq);
 
@@ -1521,6 +1526,12 @@ more_kvec:
 
 	/* msg pages? */
 	if (con->out_msg) {
+		if (con->out_msg_done) {
+			ceph_msg_put(con->out_msg);
+			con->out_msg = NULL;   /* we're done with this one */
+			goto do_next;
+		}
+
 		ret = write_partial_msg_pages(con);
 		if (ret == 1)
 			goto more_kvec;  /* we need to send the footer, too! */
@@ -1533,6 +1544,7 @@ more_kvec:
 		}
 	}
 
+do_next:
 	if (!test_bit(CONNECTING, &con->state)) {
 		/* is anything else pending? */
 		if (!list_empty(&con->out_queue)) {
@@ -1923,8 +1935,10 @@ void ceph_con_revoke(struct ceph_connection *con, struct ceph_msg *msg)
 		list_del_init(&msg->list_head);
 		ceph_msg_put(msg);
 		msg->hdr.seq = 0;
-		if (con->out_msg == msg)
+		if (con->out_msg == msg) {
+			ceph_msg_put(con->out_msg);
 			con->out_msg = NULL;
+		}
 		if (con->out_kvec_is_msg) {
 			con->out_skip = con->out_kvec_bytes;
 			con->out_kvec_is_msg = false;

fs/ceph/messenger.h

@@ -182,6 +182,7 @@ struct ceph_connection {
 	/* message out temps */
 	struct ceph_msg *out_msg;        /* sending message (== tail of
 					    out_sent) */
+	bool out_msg_done;
 	struct ceph_msg_pos out_msg_pos;
 
 	struct kvec out_kvec[8],         /* sending header/footer data */