Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Content-Type: text/plain;
        charset=utf-8
Mime-Version: 1.0 (Mac OS X Mail 12.2 \(3445.102.3\))
Subject: Re: [PATCH 1/1] block, bfq: delete "bfq" prefix from cgroup filenames
From:   Paolo Valente <paolo.valente@linaro.org>
In-Reply-To: <20190408144925.GA23021@linux-x5ow.site>
Date:   Mon, 8 Apr 2019 16:54:39 +0200
Cc:     Jens Axboe <axboe@kernel.dk>,
        linux-block <linux-block@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Linus Walleij <linus.walleij@linaro.org>,
        Mark Brown <broonie@kernel.org>,
        'Paolo Valente' via bfq-iosched 
        <bfq-iosched@googlegroups.com>,
        Oleksandr Natalenko <oleksandr@natalenko.name>,
        Angelo Ruocco <angeloruocco90@gmail.com>,
        lennart@poettering.net
Content-Transfer-Encoding: quoted-printable
Message-Id: <7B68DAA9-61D9-4AE0-9FA9-05C07C7FE408@linaro.org>
References: <20190408143935.9062-1-paolo.valente@linaro.org>
 <20190408143935.9062-2-paolo.valente@linaro.org>
 <20190408144925.GA23021@linux-x5ow.site>
To:     Johannes Thumshirn <jthumshirn@suse.de>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


> Il giorno 8 apr 2019, alle ore 16:49, Johannes Thumshirn =
<jthumshirn@suse.de> ha scritto:
>=20
> On Mon, Apr 08, 2019 at 04:39:35PM +0200, Paolo Valente wrote:
>> From: Angelo Ruocco <angeloruocco90@gmail.com>
>>=20
>> When bfq was merged into mainline, there were two I/O schedulers that
>> implemented the proportional-share policy: bfq for blk-mq and cfq for
>> legacy blk. bfq's interface files in the blkio/io controller have the
>> same names as cfq. But the cgroups interface doesn't allow two
>> entities to use the same name for their files, so for bfq we had to
>> prepend the "bfq" prefix to each of its files. However no legacy code
>> uses these modified file names. This naming also causes confusion, =
as,
>> e.g., in [1].
>>=20
>> Now cfq has gone with legacy blk, so there is no need any longer for
>> these prefixes in (the never used) bfq names. In view of this fact, =
this
>> commit removes these prefixes, thereby enabling legacy code to truly
>> use the proportional share policy in blk-mq.
>>=20
>> [1] https://github.com/systemd/systemd/issues/7057
>=20
> Hmm, but isn't this a user-space facing interface and thus some sort =
of ABI?
> Do you know what's using it and what breaks due to this conversion?
>=20

Yep, but AFAIK, the problem is exactly the opposite: nobody uses these
names for the proportional-share policy, or wants to use these names.  =
I'm
CCing Lennart too, in case he has some improbable news on this.

So the idea is to align names to what people expect, possibly before
more confusion arises.

Thanks,
Paolo

> --=20
> Johannes Thumshirn                            SUSE Labs Filesystems
> jthumshirn@suse.de                                +49 911 74053 689
> SUSE LINUX GmbH, Maxfeldstr. 5, 90409 N=C3=BCrnberg
> GF: Felix Imend=C3=B6rffer, Mary Higgins, Sri Rasiah
> HRB 21284 (AG N=C3=BCrnberg)
> Key fingerprint =3D EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850