linux-kernel - Re: [PATCH V4 2/5] nvme: add helper interface to flush in-flight requests

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Date:   Fri, 9 Mar 2018 09:59:28 +0800
From:   "jianchao.wang" <jianchao.w.wang@...cle.com>
To:     Sagi Grimberg <sagi@...mberg.me>, keith.busch@...el.com,
        axboe@...com, hch@....de
Cc:     linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org
Subject: Re: [PATCH V4 2/5] nvme: add helper interface to flush in-flight
 requests

Hi Sagi

Thanks for your precious time for review and comment.

On 03/09/2018 02:21 AM, Sagi Grimberg wrote:

>> +EXPORT_SYMBOL_GPL(nvme_abort_requests_sync);
>> +
>> +static void nvme_comp_req(struct request *req, void *data, bool reserved)
> 
> Not a very good name...

Yes, indeed.

> 
>> +{
>> +    struct nvme_ctrl *ctrl = (struct nvme_ctrl *)data;
>> +
>> +    if (!test_bit(NVME_REQ_ABORTED, &nvme_req(req)->flags))
>> +        return;
>> +
>> +    WARN_ON(!blk_mq_request_started(req));
>> +
>> +    if (ctrl->tagset && ctrl->tagset->ops->complete) {
> 
> What happens when this called on the admin tagset when the controller
> does not have an io tagset?

Yes, nvme_ctrl.admin_tagset should be used here for adminq request.


> 
>> +        clear_bit(NVME_REQ_ABORTED, &nvme_req(req)->flags);
>> +        /*
>> +         * We set the status to NVME_SC_ABORT_REQ, then ioq request
>> +         * will be requeued and adminq one will be failed.
>> +         */
>> +        nvme_req(req)->status = NVME_SC_ABORT_REQ;
>> +        /*
>> +         * For ioq request, blk_mq_requeue_request should be better
>> +         * here. But the nvme code will still setup the cmd even if
>> +         * the RQF_DONTPREP is set. We have to use .complete to free
>> +         * the cmd and then requeue it.
> 
> IMO, its better to fix nvme to not setup the command if RQF_DONTPREP is on (other than the things it must setup).

Yes, I used to consider change that.
But I'm not sure whether there is special consideration there.
If you and Keith think it is ok that not setup command when RQF_DONTPREP is set, we could do that.

> 
>> +         *
>> +         * For adminq request, invoking .complete directly will miss
>> +         * blk_mq_sched_completed_request, but this is ok because we
>> +         * won't have io scheduler for adminq.
>> +         */
>> +        ctrl->tagset->ops->complete(req);
> 
> I don't think that directly calling .complete is a good idea...

Yes, indeed.

Thanks a lot 
Jianchao