libceph: make ceph_con_get_out_msg() return the message pointer

The caller in messenger_v1.c loads it anyway, so let's keep the
pointer in the register instead of reloading it from memory. This
eliminates a tiny bit of unnecessary overhead.

Signed-off-by: Max Kellermann <[e-mail]>
Reviewed-by: Viacheslav Dubeyko <[e-mail]>
Signed-off-by: Ilya Dryomov <[e-mail]>

include/linux/ceph/messenger.h

···
 void ceph_con_process_message(struct ceph_connection *con);
 int ceph_con_in_msg_alloc(struct ceph_connection *con,
 			  struct ceph_msg_header *hdr, int *skip);
-void ceph_con_get_out_msg(struct ceph_connection *con);
+struct ceph_msg *ceph_con_get_out_msg(struct ceph_connection *con);
 
 /* messenger_v1.c */
 int ceph_con_v1_try_read(struct ceph_connection *con);

net/ceph/messenger.c

···
 	return ret;
 }
 
-void ceph_con_get_out_msg(struct ceph_connection *con)
+struct ceph_msg *ceph_con_get_out_msg(struct ceph_connection *con)
 {
 	struct ceph_msg *msg;
 
···
 	 * message or in case of a fault.
 	 */
 	WARN_ON(con->out_msg);
-	con->out_msg = ceph_msg_get(msg);
+	return con->out_msg = ceph_msg_get(msg);
 }
 
 /*

net/ceph/messenger_v1.c

···
 			&con->v1.out_temp_ack);
 	}
 
-	ceph_con_get_out_msg(con);
-	m = con->out_msg;
+	m = ceph_con_get_out_msg(con);
 
 	dout("prepare_write_message %p seq %lld type %d len %d+%d+%zd\n",
 	     m, con->out_seq, le16_to_cpu(m->hdr.type),