[PATCH 1/3] nvme: remove ->cq_vector == -1 check in nvme_queue_rq()

[Jens Axboe]

On 5/17/18 9:36 AM, Jens Axboe wrote:
> On 5/17/18 9:32 AM, Keith Busch wrote:
>> On Thu, May 17, 2018 at 09:02:15AM -0600, Jens Axboe wrote:
>>> We only clear this after calling nvme_suspend_queue(), which must
>>> have called nvme_stop_queues() first. The latter ensures that no
>>> more IO is queued, or in progress of being queued, against this
>>> hardware queue.
>>>
>>> Signed-off-by: Jens Axboe <axboe at kernel.dk>
>>> ---
>>>  drivers/nvme/host/pci.c | 5 -----
>>>  1 file changed, 5 deletions(-)
>>>
>>> diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
>>> index 5277afc6e7b5..4ed3583ad3bc 100644
>>> --- a/drivers/nvme/host/pci.c
>>> +++ b/drivers/nvme/host/pci.c
>>> @@ -887,11 +887,6 @@ static blk_status_t nvme_queue_rq(struct blk_mq_hw_ctx *hctx,
>>>  	blk_mq_start_request(req);
>>>  
>>>  	spin_lock_irq(&nvmeq->q_lock);
>>> -	if (unlikely(nvmeq->cq_vector < 0)) {
>>> -		ret = BLK_STS_IOERR;
>>> -		spin_unlock_irq(&nvmeq->q_lock);
>>> -		goto out_cleanup_iod;
>>> -	}
>>>  	__nvme_submit_cmd(nvmeq, &cmnd);
>>>  	spin_unlock_irq(&nvmeq->q_lock);
>>>  	return BLK_STS_OK;
>>
>> Unfortunatley we are still relying on this to drain entered requests on
>> a dying queue: we restart them to flush to out requests to complete with
>> error. :(
>>
>> There's probably a better way to handle this.
> 
> I'd suggest we just move it to the top and get it out of the way instead,
> and ensure that the ->cq_vector to -1 includes an mb(). Then we can just
> make it:
> 
> if (unlikely(nvmeq->cq_vector < 0))
>         return BLK_STS_IOERR;

How about this:

http://git.kernel.dk/cgit/linux-block/commit/?h=nvme-4.18&id=9913686cb779a046924441cdcac275aa24147122

-- 
Jens Axboe