[PATCH] nvme-fabrics: fix crash for no IO queues

[Chao Leng]

On 2021/3/16 1:08, 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.

 From a service continuity perspective, I think it is better that failed
the connection when unable to set any I/O queues.
Diagnose is less important, I prefer service continuity, because if failed
the reconnection and then try new reconnection, it is possible to recover.

> 
> This should be fixed for both rdma and tcp.
> .