libceph: record bio length

The bio is the only data item type that doesn't record its full
length.  Fix that.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

include/linux/ceph/messenger.h

@@ -116,7 +116,10 @@ struct ceph_msg_data {
 	enum ceph_msg_data_type		type;
 	union {
 #ifdef CONFIG_BLOCK
-		struct bio		*bio;
+		struct {
+			struct bio	*bio;
+			size_t		bio_length;
+		};
 #endif /* CONFIG_BLOCK */
 		struct {
 			struct page	**pages;	/* NOT OWNER. */

net/ceph/messenger.c

@@ -3032,6 +3032,7 @@ void ceph_msg_data_set_bio(struct ceph_msg *msg, struct bio *bio,
 	data = ceph_msg_data_create(CEPH_MSG_DATA_BIO);
 	BUG_ON(!data);
 	data->bio = bio;
+	data->bio_length = length;
 
 	msg->data = data;
 	msg->data_length = length;