From: James Smart <jsmart2021@gmail.com>
To: Sagi Grimberg <sagi@grimberg.me>, Keith Busch <kbusch@kernel.org>,
Chao Leng <lengchao@huawei.com>
Cc: linux-nvme@lists.infradead.org, axboe@fb.com, hch@lst.de
Subject: Re: [PATCH] nvme-fabrics: fix crash for no IO queues
Date: Tue, 16 Mar 2021 13:57:16 -0700 [thread overview]
Message-ID: <63ed162c-77a7-105f-5f29-47fcd32f57cd@gmail.com> (raw)
In-Reply-To: <21bc3b62-967c-6cb2-c9f3-7da479aef554@grimberg.me>
On 3/15/2021 10:08 PM, Sagi Grimberg wrote:
>
>>>>>>> A crash happens when set feature(NVME_FEAT_NUM_QUEUES) timeout in
>>>>>>> nvme
>>>>>>> over rdma(roce) reconnection, the reason is use the queue which
>>>>>>> is not
>>>>>>> alloced.
>>>>>>>
>>>>>>> If queue is not live, should not allow queue request.
>>>>>>
>>>>>> Can you describe exactly the scenario here? What is the state
>>>>>> here? LIVE? or DELETING?
>>>>> If seting feature(NVME_FEAT_NUM_QUEUES) failed due to time out or
>>>>> the target return 0 io queues, nvme_set_queue_count will return 0,
>>>>> and then reconnection will continue and success. The state of
>>>>> controller
>>>>> is LIVE. The request will continue to deliver by call ->queue_rq(),
>>>>> and then crash happens.
>>>>
>>>> Thinking about this again, we should absolutely fail the reconnection
>>>> when we are unable to set any I/O queues, it is just wrong to
>>>> keep this controller alive...
>>> Keith think keeping the controller alive for diagnose is better.
>>> This is the patch which failed the connection.
>>> https://lore.kernel.org/linux-nvme/20210223072602.3196-1-lengchao@huawei.com/
>>>
>>>
>>> Now we have 2 choice:
>>> 1.failed the connection when unable to set any I/O queues.
>>> 2.do not allow queue request when queue is not live.
>>
>> Okay, so there are different views on how to handles this. I
>> personally find
>> in-band administration for a misbehaving device is a good thing to
>> have, but I
>> won't 'nak' if the consensus from the people using this is for the
>> other way.
>
> While I understand that this can be useful, I've seen it do more harm
> than good. It is really puzzling to people when the controller state
> reflected is live (and even optimized) and no I/O is making progress for
> unknown reason. And logs are rarely accessed in these cases.
>
> I am also opting for failing it and rescheduling a reconnect.
Agree with Sagi. We also hit this issue a long time ago and I made the
same change (commit 834d3710a093a) that Sagi is suggesting: if the
prior controller instance had io queues, but the new/reconnected
controller fails to create io queues, then the controller create is
failed and a reconnect is scheduled.
-- james
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next prev parent reply other threads:[~2021-03-16 20:57 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-04 0:55 [PATCH] nvme-fabrics: fix crash for no IO queues Chao Leng
2021-03-05 20:58 ` Sagi Grimberg
2021-03-08 1:30 ` Chao Leng
2021-03-15 17:08 ` Sagi Grimberg
2021-03-16 1:23 ` Chao Leng
2021-03-16 2:02 ` Keith Busch
2021-03-16 5:08 ` Sagi Grimberg
2021-03-16 20:57 ` James Smart [this message]
2021-03-16 21:25 ` Keith Busch
2021-03-16 23:52 ` Sagi Grimberg
2021-03-17 0:19 ` James Smart
-- strict thread matches above, loose matches on Subject: below --
2021-03-03 2:53 Chao Leng
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