xfs: combine grant heads into a single 64 bit integer

Prepare for switching the grant heads to atomic variables by
combining the two 32 bit values that make up the grant head into a
single 64 bit variable.  Provide wrapper functions to combine and
split the grant heads appropriately for calculations and use them as
necessary.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff --git a/fs/xfs/linux-2.6/xfs_trace.h b/fs/xfs/linux-2.6/xfs_trace.h
index 69b9e1f..3ff6b35 100644
--- a/fs/xfs/linux-2.6/xfs_trace.h
+++ b/fs/xfs/linux-2.6/xfs_trace.h
@@ -786,10 +786,12 @@
 		__entry->flags = tic->t_flags;
 		__entry->reserveq = list_empty(&log->l_reserveq);
 		__entry->writeq = list_empty(&log->l_writeq);
-		__entry->grant_reserve_cycle = log->l_grant_reserve_cycle;
-		__entry->grant_reserve_bytes = log->l_grant_reserve_bytes;
-		__entry->grant_write_cycle = log->l_grant_write_cycle;
-		__entry->grant_write_bytes = log->l_grant_write_bytes;
+		xlog_crack_grant_head(&log->l_grant_reserve_head,
+				&__entry->grant_reserve_cycle,
+				&__entry->grant_reserve_bytes);
+		xlog_crack_grant_head(&log->l_grant_write_head,
+				&__entry->grant_write_cycle,
+				&__entry->grant_write_bytes);
 		__entry->curr_cycle = log->l_curr_cycle;
 		__entry->curr_block = log->l_curr_block;
 		__entry->tail_lsn = log->l_tail_lsn;