From mboxrd@z Thu Jan  1 00:00:00 1970
From: axboe@kernel.dk (Jens Axboe)
Date: Thu, 17 May 2018 09:36:58 -0600
Subject: [PATCH 1/3] nvme: remove ->cq_vector == -1 check in
 nvme_queue_rq()
In-Reply-To: <20180517153204.GA23555@localhost.localdomain>
References: <1526569337-3489-1-git-send-email-axboe@kernel.dk>
 <1526569337-3489-2-git-send-email-axboe@kernel.dk>
 <20180517153204.GA23555@localhost.localdomain>
Message-ID: <2d5e6a8b-b7fb-a0fa-614f-5888fdf0e8be@kernel.dk>

On 5/17/18 9:32 AM, Keith Busch wrote:
> On Thu, May 17, 2018@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;

-- 
Jens Axboe