libceph: kill last of ceph_msg_pos

The only remaining field in the ceph_msg_pos structure is
did_page_crc.  In the new cursor model of things that flag (or
something like it) belongs in the cursor.

Define a new field "need_crc" in the cursor (which applies to all
types of data) and initialize it to true whenever a cursor is
initialized.

In write_partial_message_data(), the data CRC still will be computed
as before, but it will check the cursor->need_crc field to determine
whether it's needed.  Any time the cursor is advanced to a new piece
of a data item, need_crc will be set, and this will cause the crc
for that entire piece to be accumulated into the data crc.

In write_partial_message_data() the intermediate crc value is now
held in a local variable so it doesn't have to be byte-swapped so
many times.  In read_partial_msg_data() we do something similar
(but mainly for consistency there).

With that, the ceph_msg_pos structure can go away,  and it no longer
needs to be passed as an argument to prepare_message_data().

This cleanup is related to:
    http://tracker.ceph.com/issues/4428

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

1 files changed, 1 insertions, 6 deletions

diff --git a/include/linux/ceph/messenger.h b/include/linux/ceph/messenger.h
index c76b228cb524..686df5bfa717 100644
--- a/include/linux/ceph/messenger.h
+++ b/include/linux/ceph/messenger.h
@@ -93,6 +93,7 @@ static __inline__ bool ceph_msg_data_type_valid(enum ceph_msg_data_type type)
 struct ceph_msg_data_cursor {
         size_t          resid;          /* bytes not yet consumed */
         bool            last_piece;     /* now at last piece of data item */
+        bool            need_crc;       /* new piece; crc update needed */
         union {
 #ifdef CONFIG_BLOCK
                 struct {                                /* bio */
@@ -156,10 +157,6 @@ struct ceph_msg {
         struct ceph_msgpool *pool;
 };
 
-struct ceph_msg_pos {
-        bool did_page_crc;   /* true if we've calculated crc for current page */
-};
-
 /* ceph connection fault delay defaults, for exponential backoff */
 #define BASE_DELAY_INTERVAL     (HZ/2)
 #define MAX_DELAY_INTERVAL      (5 * 60 * HZ)
@@ -217,7 +214,6 @@ struct ceph_connection {
         struct ceph_msg *out_msg;        /* sending message (== tail of
                                             out_sent) */
         bool out_msg_done;
-        struct ceph_msg_pos out_msg_pos;
 
         struct kvec out_kvec[8],         /* sending header/footer data */
                 *out_kvec_cur;
@@ -231,7 +227,6 @@ struct ceph_connection {
         /* message in temps */
         struct ceph_msg_header in_hdr;
         struct ceph_msg *in_msg;
-        struct ceph_msg_pos in_msg_pos;
         u32 in_front_crc, in_middle_crc, in_data_crc;  /* calculated crc */
 
         char in_tag;         /* protocol control byte */