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/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index 4abe7a9..1550404 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -938,10 +938,10 @@
 		log->l_curr_cycle++;
 	log->l_tail_lsn = be64_to_cpu(rhead->h_tail_lsn);
 	log->l_last_sync_lsn = be64_to_cpu(rhead->h_lsn);
-	log->l_grant_reserve_cycle = log->l_curr_cycle;
-	log->l_grant_reserve_bytes = BBTOB(log->l_curr_block);
-	log->l_grant_write_cycle = log->l_curr_cycle;
-	log->l_grant_write_bytes = BBTOB(log->l_curr_block);
+	xlog_assign_grant_head(&log->l_grant_reserve_head, log->l_curr_cycle,
+					BBTOB(log->l_curr_block));
+	xlog_assign_grant_head(&log->l_grant_write_head, log->l_curr_cycle,
+					BBTOB(log->l_curr_block));
 
 	/*
 	 * Look for unmount record.  If we find it, then we know there