bcachefs: bch2_kthread_io_clock_wait() no longer sleeps until full amount

Drop t he loop in bch2_kthread_io_clock_wait(): this allows the code
that uses it to be woken up for other reasons, and fixes a bug where
rebalance wouldn't wake up when a scan was requested.

This raises the possibility of spurious wakeups, but callers should
always be able to handle that reasonably well.

Signed-off-by: Kent Overstreet <[e-mail]>

fs/bcachefs/clock.c

···
 	if (cpu_timeout != MAX_SCHEDULE_TIMEOUT)
 		mod_timer(&wait.cpu_timer, cpu_timeout + jiffies);
 
-	while (1) {
+	do {
 		set_current_state(TASK_INTERRUPTIBLE);
 		if (kthread && kthread_should_stop())
 			break;
···
 
 		schedule();
 		try_to_freeze();
-	}
+	} while (0);
 
 	__set_current_state(TASK_RUNNING);
 	del_timer_sync(&wait.cpu_timer);