From: Jens Axboe <axboe@kernel.dk>
To: "jianchao.wang" <jianchao.w.wang@oracle.com>
Cc: ming.lei@redhat.com, linux-block@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH V11 0/4] blk-mq: refactor code of issue directly
Date: Thu, 6 Dec 2018 20:42:28 -0700 [thread overview]
Message-ID: <1e183b77-2c4d-71ff-b019-2b1070d2ed6b@kernel.dk> (raw)
In-Reply-To: <a59a3a1d-94fb-938d-7ddf-969185cd5b48@oracle.com>
On 12/6/18 8:41 PM, jianchao.wang wrote:
>
>
> On 12/7/18 11:34 AM, Jens Axboe wrote:
>> On 12/6/18 8:32 PM, Jens Axboe wrote:
>>> On 12/6/18 8:26 PM, jianchao.wang wrote:
>>>>
>>>>
>>>> On 12/7/18 11:16 AM, Jens Axboe wrote:
>>>>> On 12/6/18 8:09 PM, Jianchao Wang wrote:
>>>>>> Hi Jens
>>>>>>
>>>>>> Please consider this patchset for 4.21.
>>>>>>
>>>>>> It refactors the code of issue request directly to unify the interface
>>>>>> and make the code clearer and more readable.
>>>>>>
>>>>>> This patch set is rebased on the recent for-4.21/block and add the 1st
>>>>>> patch which inserts the non-read-write request to hctx dispatch
>>>>>> list to avoid to involve merge and io scheduler when bypass_insert
>>>>>> is true, otherwise, inserting is ignored, BLK_STS_RESOURCE is returned
>>>>>> and the caller will fail forever.
>>>>>>
>>>>>> The 2nd patch refactors the code of issue request directly to unify the
>>>>>> helper interface which could handle all the cases.
>>>>>>
>>>>>> The 3rd patch make blk_mq_sched_insert_requests issue requests directly
>>>>>> with 'bypass' false, then it needn't to handle the non-issued requests
>>>>>> any more.
>>>>>>
>>>>>> The 4th patch replace and kill the blk_mq_request_issue_directly.
>>>>>
>>>>> Sorry to keep iterating on this, but let's default to inserting to
>>>>> the dispatch list if we ever see busy from a direct dispatch. I'm fine
>>>>> with doing that for 4.21, as suggested by Ming, I just didn't want to
>>>>> fiddle with it for 4.20. This will prevent any merging on the request
>>>>> going forward, which I think is a much safer default.
>>>>>
>>>>> You do this already for some cases. Let's do it unconditionally for
>>>>> a request that was ever subjected to ->queue_rq() and we didn't either
>>>>> error or finish after the fact.
>>>>>
>>>> I have done it in this version if I get your point correctly.
>>>> Please refer to the following fragment in the 2nd patch.
>>>>
>>>> + /*
>>>> + * If the request is issued unsuccessfully with
>>>> + * BLK_STS_DEV_RESOURCE or BLK_STS_RESOURCE, insert
>>>> + * the request to hctx dispatch list due to attached
>>>> + * lldd resource.
>>>> + */
>>>> + force = true;
>>>> + ret = __blk_mq_issue_directly(hctx, rq, cookie, last);
>>>> +out_unlock:
>>>> + hctx_unlock(hctx, srcu_idx);
>>>> +out:
>>>> + switch (ret) {
>>>> + case BLK_STS_OK:
>>>> + break;
>>>> + case BLK_STS_DEV_RESOURCE:
>>>> + case BLK_STS_RESOURCE:
>>>> + if (force) {
>>>> + blk_mq_request_bypass_insert(rq, run_queue);
>>>> + ret = bypass ? BLK_STS_OK : ret;
>>>> + } else if (!bypass) {
>>>> + blk_mq_sched_insert_request(rq, false,
>>>> + run_queue, false);
>>>> + }
>>>> + break;
>>>> + default:
>>>
>>> You are right, I missed that you set force = true before doing the
>>> issue. So this looks good to me!
>>
>> I applied your series. With this, we should be good to remove the
>> REQ_NOMERGE logic that was added for the corruption case, and the
>> blk_rq_can_direct_dispatch() as well?
>>
>
> Yes, it should be that.
> Every thing rejected by .queue_rq is ended or inserted into hctx dispatch
> list. And also direct-issue path is unified with normal path.
Why are we doing that return value dance, depending on whether this
is a bypass insert or not? That seems confusing.
--
Jens Axboe
next prev parent reply other threads:[~2018-12-07 3:42 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-07 3:09 [PATCH V11 0/4] blk-mq: refactor code of issue directly Jianchao Wang
2018-12-07 3:09 ` [PATCH V11 1/4] blk-mq: insert to hctx dispatch list when bypass_insert is true Jianchao Wang
2018-12-07 3:09 ` [PATCH V11 2/4] blk-mq: refactor the code of issue request directly Jianchao Wang
2018-12-07 3:09 ` [PATCH V11 3/4] blk-mq: issue directly with bypass 'false' in blk_mq_sched_insert_requests Jianchao Wang
2018-12-07 3:09 ` [PATCH V11 4/4] blk-mq: replace and kill blk_mq_request_issue_directly Jianchao Wang
2018-12-07 3:16 ` [PATCH V11 0/4] blk-mq: refactor code of issue directly Jens Axboe
2018-12-07 3:26 ` jianchao.wang
2018-12-07 3:32 ` Jens Axboe
2018-12-07 3:34 ` Jens Axboe
2018-12-07 3:41 ` jianchao.wang
2018-12-07 3:42 ` Jens Axboe [this message]
2018-12-07 3:46 ` jianchao.wang
2018-12-07 3:47 ` Jens Axboe
2018-12-10 1:18 ` jianchao.wang
2018-12-10 1:27 ` Jens Axboe
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