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 20:32:05 -0700 [thread overview]
Message-ID: <16205e68-aa5e-c59d-364e-4164a0e51dc7@kernel.dk> (raw)
In-Reply-To: <0adf3419-bcce-93d8-51fb-aee7cbb5ae17@oracle.com>
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!
--
Jens Axboe
next prev parent reply other threads:[~2018-12-07 3:32 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 [this message]
2018-12-07 3:34 ` Jens Axboe
2018-12-07 3:41 ` jianchao.wang
2018-12-07 3:42 ` Jens Axboe
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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