[LSF/MM/BPF TOPIC] Native SCSI multipath support

[John Garry]

On 13/02/2026 17:21, Hannes Reinecke wrote:
>> At ALPSS 25 I presented a proposal for Native SCSI multipath support. 
>> Let's discuss this topic at LSFMM.
>>
>> The idea for this is that SCSI could natively support multipath, like 
>> how NVMe host driver does today. It is intended as an alternative to 
>> dm- multipath support.
>>
>> I have been working on the implementation and I plan to post patches 
>> in the next cycle. I am looking at a 3-stage approach:
>> a. create a driver-agnostic multipath library, very heavily based on 
>> NVMe host multipath support.
>> The library would support features such as path management, path 
>> selection/iopolicy, failover recovery, PR, delayed removal, gendisk 
>> management etc.
>> b. switch NVMe over to use this library
>> c. add native SCSI multipath support based on this common library
>>
> Go for it, John!
> 
> I'd be very interested in that.

cheers, in the meantime, I have some comments:

- I need to test PRs for both NVMe and SCSI, any advice on that would be 
good. I don't think that blktests covers it. I did see Christoph mention 
a testsuite at: 
https://lore.kernel.org/linux-nvme/1438672271-11309-1-git-send-email-hch@lst.de/ 
- I can check that.

- I am still not sure on whether we require a multipath version of sg. 
We can still have per-path sg. NVMe does have a multipath nvme-generic 
dev, but that just handles IOCTLs/uring cmd, and nothing like sg 
read/write fops

- I have not tried to detangle ALUA support from SCSI DH, so no ALUA 
support yet