[PATCH 0/2] nvme-fabrics: short-circuit connect retries

[Hannes Reinecke]

On 7/9/21 10:34 AM, Chao Leng wrote:
> 
> 
> On 2021/7/9 12:57, James Smart wrote:
>> On 7/7/2021 11:29 PM, Chao Leng wrote:
>>>
>>>
>>> On 2021/6/29 19:00, Hannes Reinecke wrote:
[ .. ]
>>>>
>>>> Please give details for the issues you are concerned with.
>>> For example, if host send a fabric cmd, but the fabric cmd is poisoned
>>> due to HBA inner error, abnormal or attacked network, and then the 
>>> target
>>> set the DNR to reply response. If do not reconnect for DNR response of
>>> old connection, thus the connecting can not aoto recovery. The fabric
>>> cmd poisoning may be transient, may success if try for reconnecting.
>>> so try to reconnecting is a better choice.
>>> If do not reconnect for DNR response, target should set DNR state just
>>> for target inner error.
>>>>
>>
>> It really doesn't matter what you describe is happening on the back 
>> end of the controllers/subsystem.  The rev 1.4 spec says "if the same 
>> command is re-submitted to any controller in the NVM subsystem, then 
>> that re-submitted command is expected to fail." - So, if there's a 
>> chance that a reconnect would succeed, which would be on a different 
>> controller - then subsystem is not following that statement. So you 
>> shouldn't be setting DNR.   If you disagree with this behavior, it 
>> will need to be taken up with the NVM Express group.
> I agree the nvme spec. I mean that linux kernel nvme target does not 
> behave exactly like this.
> So need to modify both host and target. In addition, the compatibility 
> between different versions should be considered.

Ah. You are talking about the _target_. I would be the first to admit 
that this could be cleared up quite a bit; there are lots of 
inconsistencies there.

And sure, I can do a patch for that, too.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
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