Re: [PATCH] nvme: Remove namespace when nvme_identify_ns_descs() failed

[Hannes Reinecke <hare@suse.de>]

On 1/8/25 11:49, Sagi Grimberg wrote:
> 
> 
> 
> On 07/01/2025 10:11, Hannes Reinecke wrote:
>> On 12/25/24 10:58, Sagi Grimberg wrote:
>>>
>>>
>>>
>>> On 29/11/2024 16:06, Hannes Reinecke wrote:
>>>> When a namespace gets unmapped on the target during scanning
>>>> nvme_identify_ns_descs() returns with a non-retryable error.
>>>> With the currrent code we will ignore that error on the grounds
>>>> that we failed to get information, and hence cannot make any
>>>> decisions whether to keep or remove that namespace.
>>>> But a non-retryable error implies that the namespace is _not_
>>>> present as we cannot retry that command and will never get
>>>> information about that namespace.
>>>> And we need to remove the namespace during scanning, as otherwise
>>>> the AEN informing us about a namespace change will find the NSID
>>>> present, but nvme_validate_ns() will fail, and the namespace
>>>> will never be updated with the correct information.
>>>
>>> Isn't that a bit harsh?
>>> I would expect to see a specific status line NVME_SC_INVALID_NS or 
>>> equivalent for a full removal of the namespace?
>>
>> Does it matter? If we get a DNR status back from 
>> nvme_identify_ns_descs() we _cannot_ resend that command.
>> Meaning we cannot get the namespace descriptors. As we
>> rely on these descriptors to properly map the namespace
>> we cannot correctly work with it, and we're better off
>> to pretend the namespace is gone and wait for an AEN
>> indicating that the namespace (or controller) state has changed.
> 
> I think it does matter. I don't think we should be removing the NS without
> the controller telling us that it is actually removed.

But what would be the recovery action here?
If the 'identify ns descs' command cannot be retried, how are
we going to map the namespace to an ns_head?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
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