linux-kernel - Re: [PATCH v6] NVMe: conversion to blk-mq

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Message-ID: <5395CE64.6040402@fb.com>
Date:	Mon, 9 Jun 2014 09:10:28 -0600
From:	Jens Axboe <axboe@...com>
To:	Ming Lei <tom.leiming@...il.com>
CC:	Matias Bjørling <m@...rling.me>,
	Matthew Wilcox <willy@...ux.intel.com>,
	Keith Busch <keith.busch@...el.com>,
	"Sam Bradshaw (sbradshaw)" <sbradshaw@...ron.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-nvme <linux-nvme@...ts.infradead.org>
Subject: Re: [PATCH v6] NVMe: conversion to blk-mq

On 2014-06-09 09:07, Ming Lei wrote:
> On Mon, Jun 9, 2014 at 10:08 PM, Jens Axboe <axboe@...com> wrote:
>> On 2014-06-08 22:35, Ming Lei wrote:
>>>
>>> On Fri, Jun 6, 2014 at 8:20 PM, Matias Bjørling <m@...rling.me> wrote:
>>>>
>>>> This converts the current NVMe driver to utilize the blk-mq layer.
>>>
>>>
>>> Looks it can't be applied cleanly against 3.15-rc8 + Jens's for-linux
>>> branch, when I fix the conflict manually, below failure is triggered:
>>>
>>> [  487.696057] nvme 0000:00:07.0: Cancelling I/O 202 QID 1
>>> [  487.699005] nvme 0000:00:07.0: Aborting I/O 202 QID 1
>>> [  487.704074] nvme 0000:00:07.0: Cancelling I/O 202 QID 1
>>> [  487.717881] nvme 0000:00:07.0: Aborting I/O 202 QID 1
>>> [  487.736093] end_request: I/O error, dev nvme0n1, sector 91532352
>>> [  487.747378] nvme 0000:00:07.0: completed id 0 twice on queue 0
>>>
>>>
>>> when running fio randread(libaio, iodepth:64) with more than 3 jobs.
>>>
>>> And looks no such failure when jobs is 1 or 2.
>>
>>
>> It's a known issue, make sure you have this patch:
>>
>> https://urldefense.proofpoint.com/v1/url?u=http://git.kernel.dk/?p%3Dlinux-block.git%3Ba%3Dcommit%3Bh%3Df6be4fb4bcb396fc3b1c134b7863351972de081f&k=ZVNjlDMF0FElm4dQtryO4A%3D%3D%0A&r=3JMVyziIyZtZ5cv9eWNLwQ%3D%3D%0A&m=04gqJgKKgVgGynQnyGFy4OmxWZ5%2FJ%2FwBiXQH3K%2BEZ4U%3D%0A&s=b137111b72079e93492763bfa23fd3458cd9b287a5eb3b68f61b69c9cda6b7a5
>
> Looks assignment to 'rq->deadline' in blk_mq_start_request()
> may be removed,  since blk_add_timer() already did that.
>
> But that isn't the only issue.
>
> Another one is that req->start_time isn't set without IO_STAT in
> nvme, which may cause similar issue too, so req->start_time
> can be set in nvme's queue_rq callback.
>
> My real issue should be nvme specific: NVME_INTERNAL_DEV_ERROR(0x6) is
> returned from device
> with the conversion patch, but no such issue in current bio mode.

You are right, I didn't get to the bottom of the thread first.
Might be better to just have ->start_time set always, regardless of io 
stats being enabled or not.

-- 
Jens Axboe

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