Re: [LSF/MM/BFP TOPIC] Block-layer device resets

Hannes Reinecke
2026-02-03T05:51:44Z

On 2/3/26 04:14, Ming Lei wrote:
> Hi Hannes,
>
> On Sun, Feb 01, 2026 at 06:06:52PM +0100, Hannes Reinecke wrote:
>> Hi all,
>>
>> We are currently working on implementing cross-controller resets for
>> NVMe, which requires to send a command to the target which then should
>> terminate all commands on a given controller.
>
> Can you provide a little background why this reset is required? And for
> solve which problem?
>
Sure. It got triggered by me wanting to use a ublk device as a backing
device for nvmet namespace.
During a nvme reconnect the target is supposed to abort/flush all
outstanding commands on the backing device. As this is a block device
we would need to have an interface into the block layer allowing us
to do so.

>> While we could easily terminate the controller, the specification
>> also requires us to terminate all outstanding commands.
>> Which then recurses into my all-time favourite topic on how to
>> abort outstanding commands from the fs/bio layer.
>
> nvme_quiesce_io_queues() & nvme_cancel_tagset() may do it, or do you have
> other new requirement not covered by the two helpers?
>
Possibly. But that would be an NVMe-specific way, and won't help us
for things like ublk.