Re: [PATCH v7 21/23] block: Avoid that flushing triggers a lockdep complaint

[Peter Zijlstra]

On Thu, Feb 14, 2019 at 03:00:56PM -0800, Bart Van Assche wrote:
> @@ -472,7 +473,8 @@ struct blk_flush_queue *blk_alloc_flush_queue(struct 
> request_queue *q,
>       if (!fq)
>               goto fail;
>  
> -     spin_lock_init(&fq->mq_flush_lock);
> +     lockdep_register_key(&fq->key);
> +     spin_lock_init_key(&fq->mq_flush_lock, &fq->key);

What's wrong with:

        spin_lock_init(&fq->wq_flush_lock);
        lockdep_register_key(&fq->key);
        lockdep_set_class(&fq->wq_flush_lock, &fq->key);

?