xfs: convert log grant heads to atomic variables

Convert the log grant heads to atomic64_t types in preparation for
converting the accounting algorithms to atomic operations. his patch
just converts the variables; the algorithmic changes are in a
separate patch for clarity.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index d118bf8..a1d7d12 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -47,7 +47,7 @@
 				xfs_buftarg_t	*log_target,
 				xfs_daddr_t	blk_offset,
 				int		num_bblks);
-STATIC int	 xlog_space_left(struct log *log, int64_t *head);
+STATIC int	 xlog_space_left(struct log *log, atomic64_t *head);
 STATIC int	 xlog_sync(xlog_t *log, xlog_in_core_t *iclog);
 STATIC void	 xlog_dealloc_log(xlog_t *log);
 
@@ -100,7 +100,7 @@
 static void
 xlog_grant_sub_space(
 	struct log	*log,
-	int64_t		*head,
+	atomic64_t	*head,
 	int		bytes)
 {
 	int		cycle, space;
@@ -119,7 +119,7 @@
 static void
 xlog_grant_add_space(
 	struct log	*log,
-	int64_t		*head,
+	atomic64_t	*head,
 	int		bytes)
 {
 	int		tmp;
@@ -816,7 +816,7 @@
 STATIC int
 xlog_space_left(
 	struct log	*log,
-	int64_t		*head)
+	atomic64_t	*head)
 {
 	int		free_bytes;
 	int		tail_bytes;