libceph: make message data be a pointer

Begin the transition from a single message data item to a list of
them by replacing the "data" structure in a message with a pointer
to a ceph_msg_data structure.

A null pointer will indicate the message has no data; replace the
use of ceph_msg_has_data() with a simple check for a null pointer.

Create functions ceph_msg_data_create() and ceph_msg_data_destroy()
to dynamically allocate and free a data item structure of a given type.

When a message has its data item "set," allocate one of these to
hold the data description, and free it when the last reference to
the message is dropped.

This partially resolves:
    http://tracker.ceph.com/issues/4429

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

1 files changed, 1 insertions, 4 deletions

diff --git a/include/linux/ceph/messenger.h b/include/linux/ceph/messenger.h
index 686df5bfa717..3181321bed6d 100644
--- a/include/linux/ceph/messenger.h
+++ b/include/linux/ceph/messenger.h
@@ -64,8 +64,6 @@ struct ceph_messenger {
         u32 required_features;
 };
 
-#define ceph_msg_has_data(m)            ((m)->data.type != CEPH_MSG_DATA_NONE)
-
 enum ceph_msg_data_type {
         CEPH_MSG_DATA_NONE,     /* message contains no data payload */
         CEPH_MSG_DATA_PAGES,    /* data source/destination is a page array */
@@ -141,8 +139,7 @@ struct ceph_msg {
         struct kvec front;              /* unaligned blobs of message */
         struct ceph_buffer *middle;
 
-        /* data payload */
-        struct ceph_msg_data    data;
+        struct ceph_msg_data    *data;  /* data payload */
 
         struct ceph_connection *con;
         struct list_head list_head;     /* links for connection lists */