bcache: remove macro nr_to_fifo_front()

Macro nr_to_fifo_front() is only used once in btree_flush_write(),
it is unncessary indeed. This patch removes this macro and does
calculation directly in place.
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/md/bcache/journal.c

@@ -417,8 +417,6 @@ int bch_journal_replay(struct cache_set *s, struct list_head *list)
 
 /* Journalling */
 
-#define nr_to_fifo_front(p, front_p, mask)	(((p) - (front_p)) & (mask))
-
 static void btree_flush_write(struct cache_set *c)
 {
 	struct btree *b, *t, *btree_nodes[BTREE_FLUSH_NR];
@@ -510,8 +508,7 @@ static void btree_flush_write(struct cache_set *c)
 		 *   journal entry can be reclaimed). These selected nodes
 		 *   will be ignored and skipped in the folowing for-loop.
 		 */
-		if (nr_to_fifo_front(btree_current_write(b)->journal,
-				     fifo_front_p,
+		if (((btree_current_write(b)->journal - fifo_front_p) &
 		     mask) != 0) {
 			mutex_unlock(&b->write_lock);
 			continue;