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Date:   Tue, 18 Dec 2018 07:47:39 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Jens Axboe <axboe@kernel.dk>
Cc:     Ming Lei <ming.lei@redhat.com>, linux-block@vger.kernel.org,
        Jeff Moyer <jmoyer@redhat.com>, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH] blk-mq: enable IO poll if .nr_queues of type poll > 0
Message-ID: <20181218064739.GA1219@lst.de>
References: <20181218041529.27787-1-ming.lei@redhat.com> <95d4e41f-24a7-bdb5-e014-994e021f901a@kernel.dk>
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On Mon, Dec 17, 2018 at 09:34:55PM -0700, Jens Axboe wrote:
> On 12/17/18 9:15 PM, Ming Lei wrote:
> > The queue mapping of type poll only exists when set->map[HCTX_TYPE_POLL].nr_queues
> > is bigger than zero, so enhance the constraint by checking .nr_queues of type poll
> > before enabling IO poll.
> > 
> > Otherwise IO race & timeout can be observed when running block/007.
> 
> Looks good to me, but we might consider having a helper for this, since
> we have this check in 3 places now. But for now this is good, thanks
> Ming.

Jens, if you want this I can drop the nvme patch to set nr_maps to 2
as it wouldn't be needed.  Not sure which one is more elegant, but
I guess Mings version is a little more fool proof.