libceph: prepare for other message data item types

This just inserts some infrastructure in preparation for handling
other types of ceph message data items.  No functional changes,
just trying to simplify review by separating out some noise.

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

1 files changed, 6 insertions, 2 deletions

diff --git a/include/linux/ceph/messenger.h b/include/linux/ceph/messenger.h
index 14862438faff..716c3fdeb257 100644
--- a/include/linux/ceph/messenger.h
+++ b/include/linux/ceph/messenger.h
@@ -97,8 +97,12 @@ static __inline__ bool ceph_msg_data_type_valid(enum ceph_msg_data_type type)
 
 struct ceph_msg_data_cursor {
         bool            last_piece;     /* now at last piece of data item */
-        struct page     *page;          /* current page in pagelist */
-        size_t          offset;         /* pagelist bytes consumed */
+        union {
+                struct {                                /* pagelist */
+                        struct page     *page;          /* page from list */
+                        size_t          offset;         /* bytes from list */
+                };
+        };
 };
 
 struct ceph_msg_data {