linux-kernel - Re: [PATCH V5 2/2] nvme-pci: fixup the timeout case when reset is ongoing

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Date:   Fri, 19 Jan 2018 13:55:29 +0800
From:   "jianchao.wang" <jianchao.w.wang@...cle.com>
To:     Keith Busch <keith.busch@...el.com>
Cc:     axboe@...com, hch@....de, sagi@...mberg.me, maxg@...lanox.com,
        james.smart@...adcom.com, linux-nvme@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V5 2/2] nvme-pci: fixup the timeout case when reset is
 ongoing

Hi Keith

Thanks for your kindly response and directive.

On 01/19/2018 12:59 PM, Keith Busch wrote:
> On Thu, Jan 18, 2018 at 06:10:02PM +0800, Jianchao Wang wrote:
>> +	 * - When the ctrl.state is NVME_CTRL_RESETTING, the expired
>> +	 *   request should come from the previous work and we handle
>> +	 *   it as nvme_cancel_request.
>> +	 * - When the ctrl.state is NVME_CTRL_RECONNECTING, the expired
>> +	 *   request should come from the initializing procedure such as
>> +	 *   setup io queues, because all the previous outstanding
>> +	 *   requests should have been cancelled.
>>  	 */
>> -	if (dev->ctrl.state == NVME_CTRL_RESETTING) {
>> -		dev_warn(dev->ctrl.device,
>> -			 "I/O %d QID %d timeout, disable controller\n",
>> -			 req->tag, nvmeq->qid);
>> -		nvme_dev_disable(dev, false);
>> +	switch (dev->ctrl.state) {
>> +	case NVME_CTRL_RESETTING:
>> +		nvme_req(req)->status = NVME_SC_ABORT_REQ;
>> +		return BLK_EH_HANDLED;
>> +	case NVME_CTRL_RECONNECTING:
>> +		WARN_ON_ONCE(nvmeq->qid);
>>  		nvme_req(req)->flags |= NVME_REQ_CANCELLED;
>>  		return BLK_EH_HANDLED;
>> +	default:
>> +		break;
>>  	}
> 
> The driver may be giving up on the command here, but that doesn't mean
> the controller has. We can't just end the request like this because that
> will release the memory the controller still owns. We must wait until
> after nvme_dev_disable clears bus master because we can't say for sure
> the controller isn't going to write to that address right after we end
> the request.
> 
Yes, but the controller is going to be reseted or shutdown at the moment,
even if the controller accesses a bad address and goes wrong, everything will
be ok after reset or shutdown. :)

Thanks
Jianchao