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

[Hannes Reinecke]

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.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare at suse.de                                +49 911 74053 688
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