Re: [syzbot] general protection fault in wb_timer_fn

[Christoph Hellwig]

On Mon, Aug 16, 2021 at 05:10:41PM +0800, Hillf Danton wrote:
> Remove and free all qos callbacks added, with cb->timer deleted in
> blk_stat_remove_callback().
> 
> only for thoughts.
> 
> +++ x/block/blk-sysfs.c
> @@ -800,9 +800,7 @@ static void blk_release_queue(struct kob
>  
>  	might_sleep();
>  
> -	if (test_bit(QUEUE_FLAG_POLL_STATS, &q->queue_flags))
> -		blk_stat_remove_callback(q, q->poll_cb);
> -	blk_stat_free_callback(q->poll_cb);
> +	rq_qos_exit(q);

rq_qos_exit is already called in blk_cleanup_queue, and the blk-mq
pollig doesn't even use the qos framework.  So I'm not sure what this
is supposed to help.