libceph: record message data length

Keep track of the length of the data portion for a message in a
separate field in the ceph_msg structure.  This information has
been maintained in wire byte order in the message header, but
that's going to change soon.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
diff --git a/include/linux/ceph/messenger.h b/include/linux/ceph/messenger.h
index 3181321..b832c0c 100644
--- a/include/linux/ceph/messenger.h
+++ b/include/linux/ceph/messenger.h
@@ -139,6 +139,7 @@
 	struct kvec front;              /* unaligned blobs of message */
 	struct ceph_buffer *middle;
 
+	size_t			data_length;
 	struct ceph_msg_data	*data;	/* data payload */
 
 	struct ceph_connection *con;
@@ -270,7 +271,8 @@
 				size_t length, size_t alignment);
 extern void ceph_msg_data_set_pagelist(struct ceph_msg *msg,
 				struct ceph_pagelist *pagelist);
-extern void ceph_msg_data_set_bio(struct ceph_msg *msg, struct bio *bio);
+extern void ceph_msg_data_set_bio(struct ceph_msg *msg, struct bio *bio,
+				size_t length);
 
 extern struct ceph_msg *ceph_msg_new(int type, int front_len, gfp_t flags,
 				     bool can_fail);