On Mon, Nov 26, 2018 at 09:35:51AM -0700, Jens Axboe wrote:
> blk-mq passes information to the hardware about any given request being
> the last that we will issue in this sequence. The point is that hardware
> can defer costly doorbell type writes to the last request. But if we run
> into errors issuing a sequence of requests, we may never send the request
> with bd->last == true set. For that case, we need a hook that tells the
> hardware that nothing else is coming right now.
> 
> For failures returned by the drivers ->queue_rq() hook, the driver is
> responsible for flushing pending requests, if it uses bd->last to
> optimize that part. This works like before, no changes there.
> 
> Signed-off-by: Jens Axboe <[email protected]>

This looks fine, but normally I would only add the method together with
the actual user..

Reviewed-by: Christoph Hellwig <[email protected]>

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