libceph: move cursor into message

A message will only be processing a single data item at a time, so
there's no need for each data item to have its own cursor.

Move the cursor embedded in the message data structure into the
message itself.  To minimize the impact, keep the data->cursor
field, but make it be a pointer to the cursor in the message.

Move the definition of ceph_msg_data above ceph_msg_data_cursor so
the cursor can point to the data without a forward definition rather
than vice-versa.

This and the upcoming patches are part of:
    http://tracker.ceph.com/issues/3761

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

1 files changed, 22 insertions, 21 deletions

diff --git a/include/linux/ceph/messenger.h b/include/linux/ceph/messenger.h
index 4fb870a5b5fc..e7557242817c 100644
--- a/include/linux/ceph/messenger.h
+++ b/include/linux/ceph/messenger.h
@@ -88,6 +88,25 @@ static __inline__ bool ceph_msg_data_type_valid(enum ceph_msg_data_type type)
         }
 }
 
+struct ceph_msg_data {
+        enum ceph_msg_data_type         type;
+        union {
+#ifdef CONFIG_BLOCK
+                struct {
+                        struct bio      *bio;
+                        size_t          bio_length;
+                };
+#endif /* CONFIG_BLOCK */
+                struct {
+                        struct page     **pages;        /* NOT OWNER. */
+                        size_t          length;         /* total # bytes */
+                        unsigned int    alignment;      /* first page */
+                };
+                struct ceph_pagelist    *pagelist;
+        };
+        struct ceph_msg_data_cursor     *cursor;
+};
+
 struct ceph_msg_data_cursor {
         size_t          resid;          /* bytes not yet consumed */
         bool            last_piece;     /* now at last piece of data item */
@@ -112,25 +131,6 @@ struct ceph_msg_data_cursor {
         };
 };
 
-struct ceph_msg_data {
-        enum ceph_msg_data_type         type;
-        union {
-#ifdef CONFIG_BLOCK
-                struct {
-                        struct bio      *bio;
-                        size_t          bio_length;
-                };
-#endif /* CONFIG_BLOCK */
-                struct {
-                        struct page     **pages;        /* NOT OWNER. */
-                        size_t          length;         /* total # bytes */
-                        unsigned int    alignment;      /* first page */
-                };
-                struct ceph_pagelist    *pagelist;
-        };
-        struct ceph_msg_data_cursor     cursor;         /* pagelist only */
-};
-
 /*
  * a single message.  it contains a header (src, dest, message type, etc.),
  * footer (crc values, mainly), a "front" message body, and possibly a
@@ -142,8 +142,9 @@ struct ceph_msg {
         struct kvec front;              /* unaligned blobs of message */
         struct ceph_buffer *middle;
 
-        size_t                  data_length;
-        struct ceph_msg_data    *data;  /* data payload */
+        size_t                          data_length;
+        struct ceph_msg_data            *data;
+        struct ceph_msg_data_cursor     cursor;
 
         struct ceph_connection *con;
         struct list_head list_head;     /* links for connection lists */