[PATCH V3 0/3] Ensure ordered namespace registration during async scan

[Hannes Reinecke]

On 2/26/26 19:15, Keith Busch wrote:
> On Thu, Feb 26, 2026 at 11:35:15AM -0500, John Meneghini wrote:
>> It's worse than this.  Yes, in RHEL we carry out of tree patches to tun off the async scanning with SCSI,
>> and we reverted this async namespace scanning patch in NVMe.
>>
>> We had to do this because, as soon as we turned these async scanning mechanisms on, we immediately
>> received customer escalations. Customer were not able to upgrade their systems. We have customer issues
>> and complaints open about this and we see this async namespace scanning as a barrier to adoption with NVMEe -
>> especially with NVME-OF which tends to have many more Namespaces than PCIe.
> 
> Sounds like some people just don't know how to use labels or persistent
> names. Relying on /dev/nvmeXnY or /dev/sdX to always be a handle to the
> same device is a fragile solution.
>   
Yeah. We have undergone this (admittedly, rather painful) process quite 
some time back for SLES (with the switch from SLES12 to SLES15 if memory
serves correctly). Since then our customer seem to be happy with using
persistent device links.

>> And yes, the PCIe async discovery stuff does cause some problems.  The difference is: the PCIe bus configuration does
>> not change nearly as often as, e.g., the nvme namespace configuration in a fabric, so customers don't notice the changing pci ids.
>> Unless some one is going lots of hot unplugging and plugging with their PCI bus, the PCI ids typically don't change at all.
> 
> It's not about the PCI topology changing. The async probe makes it
> non-deterministic as to which PCI device is going to claim which
> instance out of the nvme ida since they all try to run concurrently.

I really would like to go with the nsid based solution from Keith.
That would avoid quite some cumbersome code here.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
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