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Date:   Wed, 5 Dec 2018 14:47:27 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Jens Axboe <axboe@kernel.dk>
Cc:     Kirill Tkhai <ktkhai@virtuozzo.com>, hch@lst.de, sagi@grimberg.me,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: Kernel crashes after 529262d56dbe "block: remove ->poll_fn"
Message-ID: <20181205134727.GA26794@lst.de>
References: <0bd2d36e-bef0-b836-7039-124ae4d346a6@virtuozzo.com> <c374e085-a86b-6df3-2142-74968f067bc7@kernel.dk> <5e8d3302-a7d0-3483-6540-f0b87c237f7d@virtuozzo.com> <0e6c1e68-38b0-6618-40cd-a2b72dc4e240@kernel.dk> <a6efd5b2-3190-54e7-ad4c-06f9ac441641@kernel.dk>
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On Wed, Dec 05, 2018 at 06:39:26AM -0700, Jens Axboe wrote:
> > What device is this?
> 
> This might also help...

Yes, it should.  I had missed that we turned on QUEUE_FLAG_POLL
by default, which is rather odd.  The even weirder things is that
git-blame claims it was me who enabled it :)

> 
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 0b3874bdbc6a..81f1b105946b 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -606,8 +606,7 @@ struct request_queue {
>  				 (1 << QUEUE_FLAG_ADD_RANDOM))
>  
>  #define QUEUE_FLAG_MQ_DEFAULT	((1 << QUEUE_FLAG_IO_STAT) |		\
> -				 (1 << QUEUE_FLAG_SAME_COMP)	|	\
> -				 (1 << QUEUE_FLAG_POLL))
> +				 (1 << QUEUE_FLAG_SAME_COMP))
>  
>  void blk_queue_flag_set(unsigned int flag, struct request_queue *q);
>  void blk_queue_flag_clear(unsigned int flag, struct request_queue *q);
> 
> -- 
> Jens Axboe
---end quoted text---