linux-kernel - Re: [PATCH V9 09/15] mmc: core: Add parameter use_blk

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <43632dd9-65ac-8186-3c24-0a2121950872@intel.com>
Date:   Wed, 27 Sep 2017 15:02:52 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        linux-mmc <linux-mmc@...r.kernel.org>,
        linux-block <linux-block@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Bough Chen <haibo.chen@....com>,
        Alex Lemberg <alex.lemberg@...disk.com>,
        Mateusz Nowak <mateusz.nowak@...el.com>,
        Yuliy Izrailov <Yuliy.Izrailov@...disk.com>,
        Jaehoon Chung <jh80.chung@...sung.com>,
        Dong Aisheng <dongas86@...il.com>,
        Das Asutosh <asutoshd@...eaurora.org>,
        Zhangfei Gao <zhangfei.gao@...il.com>,
        Sahitya Tummala <stummala@...eaurora.org>,
        Harjani Ritesh <riteshh@...eaurora.org>,
        Venu Byravarasu <vbyravarasu@...dia.com>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH V9 09/15] mmc: core: Add parameter use_blk_mq

On 27/09/17 02:42, Linus Walleij wrote:
> On Fri, Sep 22, 2017 at 2:36 PM, Adrian Hunter <adrian.hunter@...el.com> wrote:
> 
>> Until mmc has blk-mq support fully implemented and tested, add a
>> parameter use_blk_mq, default to false unless config option MMC_MQ_DEFAULT
>> is selected.
>>
>> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
> 
>> +config MMC_MQ_DEFAULT
>> +       bool "MMC: use blk-mq I/O path by default"
>> +       depends on MMC && BLOCK
> 
> I would say:
> default y
> 
> Why not. SCSI is starting to enable this by default so IMO we should

SCSI didn't manage it yet.

> not take the
> intermediate step of having this as optional. Otherwise it never gets tested.

The argument that we don't have to take any responsibility for getting
things tested is a poor one.

Anyway, you can always send a patch later to change the default, so why the
hurry to do it now?

> 
> Set it to default y and after two kernel releases, if nothing happens, we simply
> delete the old block layer path.
> 
>> +#ifdef CONFIG_MMC_MQ_DEFAULT
>> +bool mmc_use_blk_mq = true;
>> +#else
>> +bool mmc_use_blk_mq = false;
>> +#endif
>> +module_param_named(use_blk_mq, mmc_use_blk_mq, bool, S_IWUSR | S_IRUGO);
> 
> Are people really modprobing this so it needs to be a module parameter?

Irrespective of modprobe, the parameter can be changed without re-compiling.

> 
> Maybe I'm the only developer stupid enough to just recompile and reboot

Just change the parameter and unbind and rebind the host controller.