bcachefs: Print last line in debugfs/btree_transaction_stats

We need to turn the flush_buf() thing into a proper API, to replace
seq_file.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/debug.c

@@ -660,8 +660,7 @@ static ssize_t lock_held_stats_read(struct file *file, char __user *buf,
 	i->size = size;
 	i->ret  = 0;
 
-	while (i->iter < ARRAY_SIZE(c->btree_transaction_fns) &&
-	       c->btree_transaction_fns[i->iter]) {
+	while (1) {
 		struct btree_transaction_stats *s = &c->btree_transaction_stats[i->iter];
 
 		err = flush_buf(i);
@@ -671,6 +670,10 @@ static ssize_t lock_held_stats_read(struct file *file, char __user *buf,
 		if (!i->size)
 			break;
 
+		if (i->iter == ARRAY_SIZE(c->btree_transaction_fns) ||
+		    !c->btree_transaction_fns[i->iter])
+			break;
+
 		prt_printf(&i->buf, "%s: ", c->btree_transaction_fns[i->iter]);
 		prt_newline(&i->buf);
 		printbuf_indent_add(&i->buf, 2);