Re: [PATCH 2/2] nvme: add 'queue_if_no_path' semantics

[Hannes Reinecke <hare@suse.de>]

On 3/5/21 9:31 PM, Sagi Grimberg wrote:
> 
>> Compare that to the 'standard', non-CMIC nvme, where with the same
>> setup MD would detach the nvme on its own:
>>
>> # cat /proc/mdstat
>> Personalities : [raid10]
>> md127 : active (auto-read-only) raid10 nvme2n1[1]
>>        4189184 blocks super 1.2 2 near-copies [2/1] [_U]
>>        bitmap: 0/1 pages [0KB], 65536KB chunk
>>
>> unused devices: <none>
>> # nvme list
>> Node             SN                   Model       Namespace
>> Usage                      Format           FW Rev
>> ---------------- --------------------
>> ---------------------------------------- ---------
>> -------------------------- ---------------- --------
>> /dev/nvme0n1     SLESNVME1            QEMU NVMe Ctrl       1         
>> 17.18  GB /  17.18  GB    512   B +  0 B   1.0
>> /dev/nvme2n1     SLESNVME3            QEMU NVMe Ctrl       1          
>> 4.29  GB /   4.29  GB    512   B +  0 B   1.0
>>
>> And yes, this is exactly the same setup, the only difference being the
>> CMIC setting for the NVMe device.
> 
> I agree with Christoph that we should do exactly the same for all.
> 
> Hannes, My understanding here is that you want the device to go away
> after the last path disappeared because it breaks md, why don't you
> want to have this also for fabrics?
> 
Oh, I would _love_ to have it for fabrics per default.
If you agree with it I can resend Keiths original patch, which solves
the issue without the need for any additional settings.

> You mention that in fabrics one can manually disconnect, but why should
> the user resort to a manual disconnect?
> 
> Is something else broken with this behavior? Maybe I am missing
> something here?

I'm just trying to understand why the current logic was build into
fabrics in the first place.
But if no-one remembers (or there was none) I'd happily convert to the
PCI logic.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		           Kernel Storage Architect
hare@suse.de			                  +49 911 74053 688
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), GF: Felix Imendörffer

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