[PATCH v2 1/8] nvme-fabrics: allow to queue requests for live queues

[James Smart]

On 8/14/2020 12:22 AM, Christoph Hellwig wrote:
> On Fri, Aug 14, 2020 at 12:08:52AM -0700, Sagi Grimberg wrote:
>>> Which will still happen with the admin queue user passthrough
>>> commands with this patch, so I don't think it actually solves anything,
>>> it just reduces the exposure a bit.
>> The original version of the patch removed that as well, but james
>> indicated that it's still needed because we have no way to make sure
>> the admin (re)connect will be the first request when we unquiesce.
> Is that whole thing really a problem?  All the pass through requests
> are inserted at the head of the queue, so how could something else
> slip in before it?  If we have a race window we probably need
> to use BLK_MQ_REQ_PREEMPT or something like to force executing the
> connect on an otherwise frozen queue.

It wasn't connect I was worried about - but rather ioctls competing with 
the ios to init the controller on the admin queue. Had really odd ioctls 
getting in immediately after connect and before controller enabled.

-- james