linux-kernel - Re: [PATCH v4 2/8] nvme-tcp: Update number of hardware queues before using them

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Date:   Tue, 10 Aug 2021 22:57:58 -0700
From:   Sagi Grimberg <sagi@...mberg.me>
To:     Keith Busch <kbusch@...nel.org>
Cc:     Daniel Wagner <dwagner@...e.de>, linux-nvme@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        James Smart <james.smart@...adcom.com>,
        Ming Lei <ming.lei@...hat.com>, Hannes Reinecke <hare@...e.de>,
        Wen Xiong <wenxiong@...ibm.com>
Subject: Re: [PATCH v4 2/8] nvme-tcp: Update number of hardware queues before
 using them


>> On 8/9/21 1:52 AM, Daniel Wagner wrote:
>>> Hi Sagi,
>>>
>>> On Fri, Aug 06, 2021 at 12:57:17PM -0700, Sagi Grimberg wrote:
>>>>> -	ret = nvme_tcp_start_io_queues(ctrl);
>>>>> -	if (ret)
>>>>> -		goto out_cleanup_connect_q;
>>>>> -
>>>>> -	if (!new) {
>>>>> -		nvme_start_queues(ctrl);
>>>>> +	} else if (prior_q_cnt != ctrl->queue_count) {
>>>>
>>>> So if the queue count did not change we don't wait to make sure
>>>> the queue g_usage_counter ref made it to zero? What guarantees that it
>>>> did?
>>>
>>> Hmm, good point. we should always call nvme_wait_freeze_timeout()
>>> for !new queues. Is this what you are implying?
>>
>> I think we should always wait for the freeze to complete.
> 
> Don't the queues need to be started in order for the freeze to complete?
> Any enqueued requests on the quiesced queues will never complete this
> way, so the wait_freeze() will be stuck, right? If so, I think the
> nvme_start_queues() was in the correct place already.

Exactly what I was trying to point out (poorly though)