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Date:   Mon, 17 Dec 2018 12:16:58 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Ming Lei <ming.lei@redhat.com>
Cc:     Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
        linux-block@vger.kernel.org, Jeff Moyer <jmoyer@redhat.com>,
        Mike Snitzer <snitzer@redhat.com>
Subject: Re: [PATCH V2 3/4] blk-mq: fix dispatch from sw queue
Message-ID: <20181217111658.GA6341@lst.de>
References: <20181217104248.5828-1-ming.lei@redhat.com> <20181217104248.5828-4-ming.lei@redhat.com> <20181217110857.GA5995@lst.de> <20181217111520.GD1329@ming.t460p>
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On Mon, Dec 17, 2018 at 07:15:21PM +0800, Ming Lei wrote:
> On Mon, Dec 17, 2018 at 12:08:57PM +0100, Christoph Hellwig wrote:
> > 
> > 
> > On Mon, Dec 17, 2018 at 06:42:47PM +0800, Ming Lei wrote:
> > > When requst is added to rq list of sw queue(ctx), the rq may be from
> > > different hctx, after multi queue mapping is introduced.
> > > 
> > > So we have to put the request into one per-queue-type list inside
> > > sw queue, otherwise the request may be dispatched to wrong hw queue.
> > 
> > Hmm.  For one I don't think splitting the lock makes sense even for
> > split lists.
> > Second, do we really need different lists, or just take
> 
> It depends if the driver/existed blk-mq code can work well if one
> request is dispatched to wrong hctx.
> 
> > the type into account when dispatching from rq_list?  I'm not really
> 
> This way may be inefficient since the whole list has to be iterated once
> for finding all requests aimed to one specific hctx.

Then just update the changelog to make this clear, please!