From mboxrd@z Thu Jan  1 00:00:00 1970
From: hch@infradead.org (Christoph Hellwig)
Date: Tue, 27 Nov 2018 23:16:01 -0800
Subject: [PATCH 3/8] blk-mq: add mq_ops->commit_rqs()
In-Reply-To: <20181126163556.5181-4-axboe@kernel.dk>
References: <20181126163556.5181-1-axboe@kernel.dk>
 <20181126163556.5181-4-axboe@kernel.dk>
Message-ID: <20181128071601.GA11774@infradead.org>

On Mon, Nov 26, 2018@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 <axboe at kernel.dk>

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

Reviewed-by: Christoph Hellwig <hch at lst.de>