libceph: don't overwrite specific con error msgs

- specific con->error_msg messages (e.g. "protocol version mismatch")
  end up getting overwritten by a catch-all "socket error on read
  / write", introduced in commit 3a140a0d ("libceph: report socket
  read/write error message")
- "bad message sequence # for incoming message" loses to "bad crc" due
  to the fact that -EBADMSG is used for both

Fix it, and tidy up con->error_msg assignments and pr_errs while at it.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

net/ceph/messenger.c

@@ -505,8 +505,6 @@ static int ceph_tcp_connect(struct ceph_connection *con)
 		pr_err("connect %s error %d\n",
 		       ceph_pr_addr(&con->peer_addr.in_addr), ret);
 		sock_release(sock);
-		con->error_msg = "connect error";
-
 		return ret;
 	}
 
@@ -2145,12 +2143,10 @@ static int process_connect(struct ceph_connection *con)
 		 * to WAIT.  This shouldn't happen if we are the
 		 * client.
 		 */
-		pr_err("process_connect got WAIT as client\n");
 		con->error_msg = "protocol error, got WAIT as client";
 		return -1;
 
 	default:
-		pr_err("connect protocol error, will retry\n");
 		con->error_msg = "protocol error, garbage tag during connect";
 		return -1;
 	}
@@ -2282,8 +2278,7 @@ static int read_partial_message(struct ceph_connection *con)
 
 	crc = crc32c(0, &con->in_hdr, offsetof(struct ceph_msg_header, crc));
 	if (cpu_to_le32(crc) != con->in_hdr.crc) {
-		pr_err("read_partial_message bad hdr "
-		       " crc %u != expected %u\n",
+		pr_err("read_partial_message bad hdr crc %u != expected %u\n",
 		       crc, con->in_hdr.crc);
 		return -EBADMSG;
 	}
@@ -2313,7 +2308,7 @@ static int read_partial_message(struct ceph_connection *con)
 		pr_err("read_partial_message bad seq %lld expected %lld\n",
 		       seq, con->in_seq + 1);
 		con->error_msg = "bad message sequence # for incoming message";
-		return -EBADMSG;
+		return -EBADE;
 	}
 
 	/* allocate message? */
@@ -2660,6 +2655,8 @@ static int try_read(struct ceph_connection *con)
 			switch (ret) {
 			case -EBADMSG:
 				con->error_msg = "bad crc";
+				/* fall through */
+			case -EBADE:
 				ret = -EIO;
 				break;
 			case -EIO:
@@ -2838,7 +2835,8 @@ static void con_work(struct work_struct *work)
 		if (ret < 0) {
 			if (ret == -EAGAIN)
 				continue;
-			con->error_msg = "socket error on read";
+			if (!con->error_msg)
+				con->error_msg = "socket error on read";
 			fault = true;
 			break;
 		}
@@ -2847,7 +2845,8 @@ static void con_work(struct work_struct *work)
 		if (ret < 0) {
 			if (ret == -EAGAIN)
 				continue;
-			con->error_msg = "socket error on write";
+			if (!con->error_msg)
+				con->error_msg = "socket error on write";
 			fault = true;
 		}
 
@@ -2869,11 +2868,13 @@ static void con_work(struct work_struct *work)
  */
 static void con_fault(struct ceph_connection *con)
 {
-	pr_warn("%s%lld %s %s\n", ENTITY_NAME(con->peer_name),
-		ceph_pr_addr(&con->peer_addr.in_addr), con->error_msg);
 	dout("fault %p state %lu to peer %s\n",
 	     con, con->state, ceph_pr_addr(&con->peer_addr.in_addr));
 
+	pr_warn("%s%lld %s %s\n", ENTITY_NAME(con->peer_name),
+		ceph_pr_addr(&con->peer_addr.in_addr), con->error_msg);
+	con->error_msg = NULL;
+
 	WARN_ON(con->state != CON_STATE_CONNECTING &&
 	       con->state != CON_STATE_NEGOTIATING &&
 	       con->state != CON_STATE_OPEN);
@@ -3295,8 +3296,8 @@ static int ceph_con_in_msg_alloc(struct ceph_connection *con, int *skip)
 		 */
 		if (*skip)
 			return 0;
-		con->error_msg = "error allocating memory for incoming message";
 
+		con->error_msg = "error allocating memory for incoming message";
 		return -ENOMEM;
 	}
 	memcpy(&con->in_msg->hdr, &con->in_hdr, sizeof(con->in_hdr));