bcache: writeback: Remove unneeded variable i

Remove unneeded variable i in bch_dirty_init_thread().
Signed-off-by: NXu Wang <vulab@iscas.ac.cn>
Signed-off-by: NColy Li <colyli@suse.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

drivers/md/bcache/writeback.c

@@ -825,10 +825,8 @@ static int bch_dirty_init_thread(void *arg)
 	struct btree_iter iter;
 	struct bkey *k, *p;
 	int cur_idx, prev_idx, skip_nr;
-	int i;
 
 	k = p = NULL;
-	i = 0;
 	cur_idx = prev_idx = 0;
 
 	bch_btree_iter_init(&c->root->keys, &iter, NULL);