linux-kernel - Re: [PATCH] nvme-pci: fix the timeout case when reset is ongoing

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Message-ID: <496ee23f-2dd2-9c7b-17a2-23fe02ec00e2@oracle.com>
Date:   Fri, 5 Jan 2018 13:36:11 +0800
From:   "jianchao.wang" <jianchao.w.wang@...cle.com>
To:     Christoph Hellwig <hch@....de>
Cc:     keith.busch@...el.com, axboe@...com, sagi@...mberg.me,
        linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nvme-pci: fix the timeout case when reset is ongoing

Hi Christoph

Many thanks for your kindly response.

On 01/04/2018 06:35 PM, Christoph Hellwig wrote:
> On Wed, Jan 03, 2018 at 06:31:44AM +0800, Jianchao Wang wrote:
>> NVME_CTRL_RESETTING used to indicate the range of nvme initializing
>> strictly in fd634f41(nvme: merge probe_work and reset_work), but it
>> is not now. The NVME_CTRL_RESETTING is set before queue the
>> reset_work, there could be a big gap before the reset work handles
>> the outstanding requests. So when the NVME_CTRL_RESETTING is set,
>> nvme_timeout will not only meet the admin requests from the
>> initializing procedure, but also the IO and admin requests from
>> previous work before nvme_dev_disable is invoked.
>>
>> To fix it, introduce a flag NVME_DEV_FLAG_INITIALIZING to mark the
>> range of initializing. When this flag is not set, handle the expried
>> requests as nvme_cancel_request. Otherwise, the requests should be
>> from the initializing procedure. Handle them as before. Because the
>> nvme_reset_work will see the error and disable the dev itself, so
>> discard the nvme_dev_disable here.
> 
> Instead of a parallel set of states we'll need to split
> NVME_CTRL_RESET into NVME_CTRL_RESET_SCHEDULED and NVME_CTRL_RESETTING.
> 
> And if my memory doesn't fail me we were already considering that a while
> ago.
> 
Yes, it is indeed more reasonable to split current NVME_CTRL_RESETTING into 
two states, but the nvme_dev_disable() in nvme_reset_work() should be the boundary.
After that, all the in-flight requests are requeued and request queue is quiesced,
the nvme driver is clear. So the new state maybe something like NEW_CTRL_RESET_PREPARE.:)

Thanks
Jianchao