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Groups > linux.kernel > #1731328
| From | "jianchao.wang" <jianchao.w.wang@oracle.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH] blk-mq: put the driver tag of nxt rq before first one is requeued |
| Date | 2017-09-13 03:50 +0200 |
| Message-ID | <up4Yp-KK-7@gated-at.bofh.it> (permalink) |
| References | <uoPwm-7PF-21@gated-at.bofh.it> <uoQC6-8vg-11@gated-at.bofh.it> <up4lI-wf-11@gated-at.bofh.it> <up4F4-El-3@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On 09/13/2017 09:24 AM, Ming Lei wrote:
> On Wed, Sep 13, 2017 at 09:01:25AM +0800, jianchao.wang wrote:
>> Hi ming
>>
>> On 09/12/2017 06:23 PM, Ming Lei wrote:
>>>> @@ -1029,14 +1029,20 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list)
>>>> if (list_empty(list))
>>>> bd.last = true;
>>>> else {
>>>> - struct request *nxt;
>>>> -
>>>> nxt = list_first_entry(list, struct request, queuelist);
>>>> bd.last = !blk_mq_get_driver_tag(nxt, NULL, false);
>>>> }
>>>>
>>>> ret = q->mq_ops->queue_rq(hctx, &bd);
>>>> if (ret == BLK_STS_RESOURCE) {
>>>> + /*
>>>> + * If an I/O scheduler has been configured and we got a
>>>> + * driver tag for the next request already, free it again.
>>>> + */
>>>> + if (!list_empty(list)) {
>>>> + nxt = list_first_entry(list, struct request, queuelist);
>>>> + blk_mq_put_driver_tag(nxt);
>>>> + }
>>> The following way might be more simple and clean:
>>>
>>> if (nxt)
>>> blk_mq_put_driver_tag(nxt);
>>>
>>> meantime 'nxt' need to be cleared inside the 'if (list_empty(list))'
>>> before .queue_rq().
>>
>> I had ever thought about that, but to avoid add extra command in the
>> fast path, I made the patch above.
>
> Got it, so how about changing to the following way simply:
>
> if (nxt && !list_empty(list))
> blk_mq_put_driver_tag(nxt);
>
It seems that we even could change it as following:
if (!list_empty(list))
blk_mq_put_driver_tag(nxt);
thanks
jianchao
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[PATCH] blk-mq: put the driver tag of nxt rq before first one is requeued Jianchao Wang <jianchao.w.wang@oracle.com> - 2017-09-12 11:20 +0200
Re: [PATCH] blk-mq: put the driver tag of nxt rq before first one is requeued Ming Lei <ming.lei@redhat.com> - 2017-09-12 12:30 +0200
Re: [PATCH] blk-mq: put the driver tag of nxt rq before first one is requeued "jianchao.wang" <jianchao.w.wang@oracle.com> - 2017-09-13 03:10 +0200
Re: [PATCH] blk-mq: put the driver tag of nxt rq before first one is requeued Ming Lei <ming.lei@redhat.com> - 2017-09-13 03:30 +0200
Re: [PATCH] blk-mq: put the driver tag of nxt rq before first one is requeued "jianchao.wang" <jianchao.w.wang@oracle.com> - 2017-09-13 03:50 +0200
Re: [PATCH] blk-mq: put the driver tag of nxt rq before first one is requeued Ming Lei <ming.lei@redhat.com> - 2017-09-13 04:00 +0200
Re: [PATCH] blk-mq: put the driver tag of nxt rq before first one is requeued Jens Axboe <axboe@kernel.dk> - 2017-09-13 04:30 +0200
Re: [PATCH] blk-mq: put the driver tag of nxt rq before first one is requeued "jianchao.wang" <jianchao.w.wang@oracle.com> - 2017-09-13 04:50 +0200
Re: [PATCH] blk-mq: put the driver tag of nxt rq before first one is requeued Jens Axboe <axboe@kernel.dk> - 2017-09-13 04:50 +0200
Re: [PATCH] blk-mq: put the driver tag of nxt rq before first one is requeued "jianchao.wang" <jianchao.w.wang@oracle.com> - 2017-09-13 05:40 +0200
Re: [PATCH] blk-mq: put the driver tag of nxt rq before first one is requeued Jens Axboe <axboe@kernel.dk> - 2017-09-13 06:00 +0200
Re: [PATCH] blk-mq: put the driver tag of nxt rq before first one is requeued "jianchao.wang" <jianchao.w.wang@oracle.com> - 2017-09-13 06:00 +0200
Re: [PATCH] blk-mq: put the driver tag of nxt rq before first one is requeued Ming Lei <ming.lei@redhat.com> - 2017-09-13 06:00 +0200
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