linux-kernel - Re: [PATCH V2 0/6]nvme-pci: fixes on nvme_timeout and nvme_dev

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Date:   Sat, 10 Feb 2018 10:59:32 +0800
From:   "jianchao.wang" <jianchao.w.wang@...cle.com>
To:     Keith Busch <keith.busch@...el.com>
Cc:     axboe@...com, hch@....de, linux-kernel@...r.kernel.org,
        linux-nvme@...ts.infradead.org, Sagi Grimberg <sagi@...mberg.me>
Subject: Re: [PATCH V2 0/6]nvme-pci: fixes on nvme_timeout and
 nvme_dev_disable

Hi Keith

On 02/10/2018 10:32 AM, jianchao.wang wrote:
> Hi Keith
> 
> Thanks for your kindly response here.
> That's really appreciated.
> 
> On 02/10/2018 01:12 AM, Keith Busch wrote:
>> On Fri, Feb 09, 2018 at 09:50:58AM +0800, jianchao.wang wrote:
>>>
>>> if we set NVME_REQ_CANCELLED and return BLK_EH_HANDLED as the RESETTING case,
>>> nvme_reset_work will hang forever, because no one could complete the entered requests.
>>
>> Except it's no longer in the "RESETTING" case since you added the
>> "CONNECTING" state, so that's already broken for other reasons...
>>
> 
> Yes, but as your patch, we have to fail the IOs and even kill the controller.
> In fact, up to nvme_wait_freeze in nvme_reset_work, the RECONNECTING state has been completed.
> We even could say it is in LIVE state. Maybe we should recover the controller again instead
> of fail the IOs and kill the controller.
> 
> On the other hand, can you share with me why we cannot use blk_set_preempt_only to replace
> blk_freeze_queue ? we just want to gate the new bios out of generic_make_request and we 
> needn't use the preempt requests.
> 
> Looking forward your advice and directive.

Avoid wait_freeze in nvme_reset_work should be a better way to fix this defect.

> 
> Thanks
> Jianchao