libceph: fix messenger retry

In ancient times, the messenger could both initiate and accept connections.
An artifact if that was data structures to store/process an incoming
ceph_msg_connect request and send an outgoing ceph_msg_connect_reply.
Sadly, the negotiation code was referencing those structures and ignoring
important information (like the peer's connect_seq) from the correct ones.

Among other things, this fixes tight reconnect loops where the server sends
RETRY_SESSION and we (the client) retries with the same connect_seq as last
time.  This bug pretty easily triggered by injecting socket failures on the
MDS and running some fs workload like workunits/direct_io/test_sync_io.
Signed-off-by: Sage Weil <sage@inktank.com>

include/linux/ceph/messenger.h

@@ -163,16 +163,8 @@ struct ceph_connection {
 
 	/* connection negotiation temps */
 	char in_banner[CEPH_BANNER_MAX_LEN];
-	union {
-		struct {  /* outgoing connection */
-			struct ceph_msg_connect out_connect;
-			struct ceph_msg_connect_reply in_reply;
-		};
-		struct {  /* incoming */
-			struct ceph_msg_connect in_connect;
-			struct ceph_msg_connect_reply out_reply;
-		};
-	};
+	struct ceph_msg_connect out_connect;
+	struct ceph_msg_connect_reply in_reply;
 	struct ceph_entity_addr actual_peer_addr;
 
 	/* message out temps */

net/ceph/messenger.c

@@ -1423,7 +1423,7 @@ static int process_connect(struct ceph_connection *con)
 		 * dropped messages.
 		 */
 		dout("process_connect got RESET peer seq %u\n",
-		     le32_to_cpu(con->in_connect.connect_seq));
+		     le32_to_cpu(con->in_reply.connect_seq));
 		pr_err("%s%lld %s connection reset\n",
 		       ENTITY_NAME(con->peer_name),
 		       ceph_pr_addr(&con->peer_addr.in_addr));
@@ -1450,10 +1450,10 @@ static int process_connect(struct ceph_connection *con)
 		 * If we sent a smaller connect_seq than the peer has, try
 		 * again with a larger value.
 		 */
-		dout("process_connect got RETRY my seq = %u, peer_seq = %u\n",
+		dout("process_connect got RETRY_SESSION my seq %u, peer %u\n",
 		     le32_to_cpu(con->out_connect.connect_seq),
-		     le32_to_cpu(con->in_connect.connect_seq));
-		con->connect_seq = le32_to_cpu(con->in_connect.connect_seq);
+		     le32_to_cpu(con->in_reply.connect_seq));
+		con->connect_seq = le32_to_cpu(con->in_reply.connect_seq);
 		ceph_con_out_kvec_reset(con);
 		ret = prepare_write_connect(con);
 		if (ret < 0)
@@ -1468,9 +1468,9 @@ static int process_connect(struct ceph_connection *con)
 		 */
 		dout("process_connect got RETRY_GLOBAL my %u peer_gseq %u\n",
 		     con->peer_global_seq,
-		     le32_to_cpu(con->in_connect.global_seq));
+		     le32_to_cpu(con->in_reply.global_seq));
 		get_global_seq(con->msgr,
-			       le32_to_cpu(con->in_connect.global_seq));
+			       le32_to_cpu(con->in_reply.global_seq));
 		ceph_con_out_kvec_reset(con);
 		ret = prepare_write_connect(con);
 		if (ret < 0)