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Subject: Re: [PATCH] block/bfq: fix ifdef for CONFIG_BFQ_GROUP_IOSCHED=y
To:     Jens Axboe <axboe@kernel.dk>,
        Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
        linux-block@vger.kernel.org,
        Paolo Valente <paolo.valente@linaro.org>,
        linux-kernel@vger.kernel.org
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From:   =?UTF-8?Q?Holger_Hoffst=c3=a4tte?= <holger@applied-asynchrony.com>
Organization: Applied Asynchrony, Inc.
Message-ID: <3c87a84f-9fb2-2407-a5a3-723b314d8e58@applied-asynchrony.com>
Date:   Fri, 29 Mar 2019 17:44:13 +0100
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On 3/29/19 5:15 PM, Jens Axboe wrote:
>>>> Good catch! I run without group scheduling and therefore didn't notice these
>>>> stray defines earlier. For 5.1 it should merge cleanly; adding this on top of
>>>> the pending 5.2 BFQ patches required a small context fixup in hunk #1 due to
>>>> "block, bfq: do not idle for lowest-weight queues".
>>>
>>> I'm hesitant to apply this, since the group scheduling stuff has obviously never
>>> been tested.
>>
>> This is simply a regression in 5.1 caused by 73d58118498b - nothing else,
>> and as such this fix needs to go into 5.1 as well. I'm sure Paolo will agree.
>> What you so ominously  call "the group scheduling stuff" has been there and
>> shipping in mainline since day 1 of the BFQ merge, and it works fine in 5.0.
> 
> If that's the case (I didn't check how far back it went), then yes, it should
> of course go into 5.1.

Yay.

> The ominous nature of my reply I'll chalk up to your interpretation

Fair enough ;)

A more interesting question is why upstream uses undefined defines
for patches. That's a first-rate self-grenade if I've ever seen one,
and obviously something that is easily missed. Paolo?

-h