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 20:34:35 -0700 [thread overview]
Message-ID: <f052c016-e521-9f12-f4e5-d65f3814643a@kernel.dk> (raw)
In-Reply-To: <16205e68-aa5e-c59d-364e-4164a0e51dc7@kernel.dk>
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?
--
Jens Axboe
next prev parent reply other threads:[~2018-12-07 3:34 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 [this message]
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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