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Date:   Mon, 17 Dec 2018 12:08:57 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Ming Lei <ming.lei@redhat.com>
Cc:     Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
        Jeff Moyer <jmoyer@redhat.com>,
        Mike Snitzer <snitzer@redhat.com>,
        Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH V2 3/4] blk-mq: fix dispatch from sw queue
Message-ID: <20181217110857.GA5995@lst.de>
References: <20181217104248.5828-1-ming.lei@redhat.com> <20181217104248.5828-4-ming.lei@redhat.com>
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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
the type into account when dispatching from rq_list?  I'm not really
sure about that one, but a rationale for splitting might be worth
adding to the changelog if you want to stick to the split lists.