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

[Nilay Shroff <nilay@linux.ibm.com>]

On 1/13/25 7:59 PM, Hannes Reinecke wrote:
> On 1/13/25 15:12, Nilay Shroff wrote:
>>
>>
>> On 1/13/25 1:13 PM, Hannes Reinecke wrote:
>>> On 1/11/25 15:01, Nilay Shroff wrote:
>>>>
>>>>
> [ .. ]
>>> So my argument is that in this specific case the 'ANA inaccessible' nvme
>>> state should _not_ be retried, but should be treated as identical to
>>> 'invalid namespace' errors.
>>>
>> I think I got what you're trying to propose. So when this issue manifests, on host, if we
>> could possibly differentiate between nvme_identify_ns_descs() failed reasons : is it failed
>> because the nsid has been removed/un-mapped on the target or is it failed due to "ANA inaccessible"
>> state? IMO, for "ANA inaccessible" status, we may not want to immediately remove the ns from
>> the host (due to reason I mentioned earlier per NVMe spec section 8.1.3.3), however for the
>> other error case we may remove the ns from the host.
>> I think issuing ns descriptor list command to target for a nsid which doesn't exist on the
>> target would return buffer filled with all zeros. So that might be an indication that ns has
>> been removed from the target.
>>   
> But only if the NSID has not been remapped in the meantime.
> If it has (as in my case) the ns descriptor list will be valid, it just
> refers to another namespace.
> 
If NSID has been unmapped and then remapped on the targer then in that case, 
host would hit the mismatch uuid case (under nvme_validate_ns()) and so host 
would then remove the namespace. 

I think there are two cases, 
Case1:
1. AEN triggers rescan
2. List of active nsid is retrieved
-> NSID A is removed on the target
3. Scanning of NSID A fails (i.e. nvme_identify_ns_descs() returns buffer filled with all zeros)
-> host removes the respective namespace

Case2:
1. AEN triggers rescan
2. List of active nsid is retrieved
-> NSID A is unmapped and remapped (possibly with different uuid) on target
3. Scanning of NSID A succeed 
4. host finds the mismatch uuid for NSID A (i.e. nvme_validate_ns() fails)
-> host removes the respective namespace
 
Thanks,
--Nilay