[PATCHv3] nvme-mpath: delete disk after last connection

[Hannes Reinecke]

On 5/6/21 9:43 AM, Christoph Hellwig wrote:
> On Tue, May 04, 2021 at 12:54:14PM -0700, Sagi Grimberg wrote:
>> Yes, I'm not sure I understand your comment Christoph. This addresses an
>> issue with mdraid where hot unplug+replug does not restore the device to
>> the raid group (pci and fabrics alike), where before multipath this used
>> to work.
>>
>> queue_if_no_path is a dm-multipath feature so I'm not entirely clear
>> what is the concern? mdraid on nvme (pci/fabrics) used to work a certain
>> way, with the introduction of nvme-mpath the behavior was broken (as far
>> as I understand from Hannes).
> 
> AFAIK that specific mdraid behavior is also fixed by the uevent patch
> he sent.
> 
It is most emphatically _NOT_.

These two patches are complementary.

To rephrase: with the current behaviour MD is completely hosed once one
NVMe-oF device get removed after ctrl_loss_tmo kicks in.

And _nothing_ will fix that except a system reboot.

_That_ is the issue this patch fixes.

The other patch for sending the uevent is just to tell MD that recovery
can start. But recovery _cannot_ start without this patch.

> 
> I really do not think we should change the mpath behaviors years after
> first adding it.
> 

But only because no-one ever tested MD on nvme-multipath.
It has been broken since day 1.

Cheers,

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