xfs: rework log grant space calculations

The log grant space calculations are repeated for both write and
reserve grant heads. To make it simpler to convert the calculations
toa different algorithm, factor them so both the gratn heads use the
same calculation functions. Once this is done we can drop the
wrappers that are used in only a couple of place to update both
grant heads at once as they don't provide any particular value.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/xfs_log.c

@@ -98,53 +98,34 @@ STATIC void	xlog_verify_tail_lsn(xlog_t *log, xlog_in_core_t *iclog,
 STATIC int	xlog_iclogs_empty(xlog_t *log);
 
 static void
-xlog_grant_sub_space(struct log *log, int bytes)
+xlog_grant_sub_space(
+	struct log	*log,
+	int		*cycle,
+	int		*space,
+	int		bytes)
 {
-	log->l_grant_write_bytes -= bytes;
+	*space -= bytes;
-	if (log->l_grant_write_bytes < 0) {
+	if (*space < 0) {
-		log->l_grant_write_bytes += log->l_logsize;
+		*space += log->l_logsize;
-		log->l_grant_write_cycle--;
+		(*cycle)--;
-	}
-
-	log->l_grant_reserve_bytes -= bytes;
-	if ((log)->l_grant_reserve_bytes < 0) {
-		log->l_grant_reserve_bytes += log->l_logsize;
-		log->l_grant_reserve_cycle--;
-	}
-
-}
-
-static void
-xlog_grant_add_space_write(struct log *log, int bytes)
-{
-	int tmp = log->l_logsize - log->l_grant_write_bytes;
-	if (tmp > bytes)
-		log->l_grant_write_bytes += bytes;
-	else {
-		log->l_grant_write_cycle++;
-		log->l_grant_write_bytes = bytes - tmp;
 	}
 }
 
 static void
-xlog_grant_add_space_reserve(struct log *log, int bytes)
+xlog_grant_add_space(
+	struct log	*log,
+	int		*cycle,
+	int		*space,
+	int		bytes)
 {
-	int tmp = log->l_logsize - log->l_grant_reserve_bytes;
+	int tmp = log->l_logsize - *space;
 	if (tmp > bytes)
-		log->l_grant_reserve_bytes += bytes;
+		*space += bytes;
 	else {
-		log->l_grant_reserve_cycle++;
+		*space = bytes - tmp;
-		log->l_grant_reserve_bytes = bytes - tmp;
+		(*cycle)++;
 	}
 }
-
-static inline void
-xlog_grant_add_space(struct log *log, int bytes)
-{
-	xlog_grant_add_space_write(log, bytes);
-	xlog_grant_add_space_reserve(log, bytes);
-}
-
 static void
 xlog_tic_reset_res(xlog_ticket_t *tic)
 {
@@ -1344,7 +1325,10 @@ xlog_sync(xlog_t		*log,
 
 	/* move grant heads by roundoff in sync */
 	spin_lock(&log->l_grant_lock);
-	xlog_grant_add_space(log, roundoff);
+	xlog_grant_add_space(log, &log->l_grant_reserve_cycle,
+				&log->l_grant_reserve_bytes, roundoff);
+	xlog_grant_add_space(log, &log->l_grant_write_cycle,
+				&log->l_grant_write_bytes, roundoff);
 	spin_unlock(&log->l_grant_lock);
 
 	/* put cycle number in every block */
@@ -2574,7 +2558,10 @@ xlog_grant_log_space(xlog_t	   *log,
 	list_del_init(&tic->t_queue);
 
 	/* we've got enough space */
-	xlog_grant_add_space(log, need_bytes);
+	xlog_grant_add_space(log, &log->l_grant_reserve_cycle,
+				&log->l_grant_reserve_bytes, need_bytes);
+	xlog_grant_add_space(log, &log->l_grant_write_cycle,
+				&log->l_grant_write_bytes, need_bytes);
 	trace_xfs_log_grant_exit(log, tic);
 	xlog_verify_grant_head(log, 1);
 	xlog_verify_grant_tail(log);
@@ -2701,7 +2688,8 @@ xlog_regrant_write_log_space(xlog_t	   *log,
 	list_del_init(&tic->t_queue);
 
 	/* we've got enough space */
-	xlog_grant_add_space_write(log, need_bytes);
+	xlog_grant_add_space(log, &log->l_grant_write_cycle,
+				&log->l_grant_write_bytes, need_bytes);
 	trace_xfs_log_regrant_write_exit(log, tic);
 	xlog_verify_grant_head(log, 1);
 	xlog_verify_grant_tail(log);
@@ -2742,7 +2730,12 @@ xlog_regrant_reserve_log_space(xlog_t	     *log,
 		ticket->t_cnt--;
 
 	spin_lock(&log->l_grant_lock);
-	xlog_grant_sub_space(log, ticket->t_curr_res);
+	xlog_grant_sub_space(log, &log->l_grant_reserve_cycle,
+				&log->l_grant_reserve_bytes,
+				ticket->t_curr_res);
+	xlog_grant_sub_space(log, &log->l_grant_write_cycle,
+				&log->l_grant_write_bytes,
+				ticket->t_curr_res);
 	ticket->t_curr_res = ticket->t_unit_res;
 	xlog_tic_reset_res(ticket);
 
@@ -2756,7 +2749,9 @@ xlog_regrant_reserve_log_space(xlog_t	     *log,
 		return;
 	}
 
-	xlog_grant_add_space_reserve(log, ticket->t_unit_res);
+	xlog_grant_add_space(log, &log->l_grant_reserve_cycle,
+				&log->l_grant_reserve_bytes,
+				ticket->t_unit_res);
 
 	trace_xfs_log_regrant_reserve_exit(log, ticket);
 
@@ -2785,24 +2780,30 @@ STATIC void
 xlog_ungrant_log_space(xlog_t	     *log,
 		       xlog_ticket_t *ticket)
 {
+	int	bytes;
+
 	if (ticket->t_cnt > 0)
 		ticket->t_cnt--;
 
 	spin_lock(&log->l_grant_lock);
 	trace_xfs_log_ungrant_enter(log, ticket);
-
-	xlog_grant_sub_space(log, ticket->t_curr_res);
-
 	trace_xfs_log_ungrant_sub(log, ticket);
 
-	/* If this is a permanent reservation ticket, we may be able to free
+	/*
+	 * If this is a permanent reservation ticket, we may be able to free
 	 * up more space based on the remaining count.
 	 */
+	bytes = ticket->t_curr_res;
 	if (ticket->t_cnt > 0) {
 		ASSERT(ticket->t_flags & XLOG_TIC_PERM_RESERV);
-		xlog_grant_sub_space(log, ticket->t_unit_res*ticket->t_cnt);
+		bytes += ticket->t_unit_res*ticket->t_cnt;
 	}
 
+	xlog_grant_sub_space(log, &log->l_grant_reserve_cycle,
+				&log->l_grant_reserve_bytes, bytes);
+	xlog_grant_sub_space(log, &log->l_grant_write_cycle,
+				&log->l_grant_write_bytes, bytes);
+
 	trace_xfs_log_ungrant_exit(log, ticket);
 
 	xlog_verify_grant_head(log, 1);