linux-kernel - Re: [PATCH V5 4/7] blk-mq: introduce blk_mq_dequeue_from

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Message-ID: <20171003090109.GB21184@infradead.org>
Date:   Tue, 3 Oct 2017 02:01:09 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Ming Lei <ming.lei@...hat.com>
Cc:     Jens Axboe <axboe@...com>, linux-block@...r.kernel.org,
        Christoph Hellwig <hch@...radead.org>,
        Mike Snitzer <snitzer@...hat.com>, dm-devel@...hat.com,
        Bart Van Assche <bart.vanassche@...disk.com>,
        Laurence Oberman <loberman@...hat.com>,
        Paolo Valente <paolo.valente@...aro.org>,
        Oleksandr Natalenko <oleksandr@...alenko.name>,
        Tom Nguyen <tom81094@...il.com>, linux-kernel@...r.kernel.org,
        linux-scsi@...r.kernel.org, Omar Sandoval <osandov@...com>
Subject: Re: [PATCH V5 4/7] blk-mq: introduce blk_mq_dequeue_from_ctx()

On Sat, Sep 30, 2017 at 06:27:17PM +0800, Ming Lei wrote:
> This function is introduced for dequeuing request
> from sw queue so that we can dispatch it in
> scheduler's way.
> 
> More importantly, some SCSI devices may set
> q->queue_depth, which is a per-request_queue limit,
> and applied on pending I/O from all hctxs. This
> function is introduced for avoiding to dequeue too
> many requests from sw queue when ->dispatch isn't
> flushed completely.

Weird commit log formatting, please use your 70+ chacters to format the
text.

> @@ -882,6 +882,44 @@ void blk_mq_flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, struct list_head *list)
>  }
>  EXPORT_SYMBOL_GPL(blk_mq_flush_busy_ctxs);
>  
> +struct dispatch_rq_data {
> +	struct blk_mq_hw_ctx *hctx;
> +	struct request *rq;
> +};
> +
> +static bool dispatch_rq_from_ctx(struct sbitmap *sb, unsigned int bitnr, void *data)

Overly long line.

But except for that this looks ok to me except for the fact that you
just add an unused function.