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Date:   Tue, 23 May 2023 09:19:57 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Bart Van Assche <bvanassche@acm.org>
Cc:     Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
        Christoph Hellwig <hch@lst.de>,
        Mike Snitzer <snitzer@kernel.org>,
        Damien Le Moal <dlemoal@kernel.org>,
        Jaegeuk Kim <jaegeuk@kernel.org>,
        Ming Lei <ming.lei@redhat.com>
Subject: Re: [PATCH v3 4/7] block: Make it easier to debug zoned write
 reordering
Message-ID: <20230523071957.GD8758@lst.de>
References: <20230522183845.354920-1-bvanassche@acm.org> <20230522183845.354920-5-bvanassche@acm.org>
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On Mon, May 22, 2023 at 11:38:39AM -0700, Bart Van Assche wrote:
> @@ -2429,6 +2429,9 @@ static void blk_mq_request_bypass_insert(struct request *rq, blk_insert_t flags)
>  {
>  	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
>  
> +	WARN_ON_ONCE(rq->rq_flags & RQF_USE_SCHED &&
> +		     blk_rq_is_seq_zoned_write(rq));
> +
>  	spin_lock(&hctx->lock);
>  	if (flags & BLK_MQ_INSERT_AT_HEAD)
>  		list_add(&rq->queuelist, &hctx->dispatch);
> @@ -2562,6 +2565,9 @@ static blk_status_t __blk_mq_issue_directly(struct blk_mq_hw_ctx *hctx,
>  	};
>  	blk_status_t ret;
>  
> +	WARN_ON_ONCE(rq->rq_flags & RQF_USE_SCHED &&
> +		     blk_rq_is_seq_zoned_write(rq));

What makes sequential writes here special vs other requests that are
supposed to be using the scheduler and not a bypass?