linux-kernel - Re: [PATCH 1/1] block, bfq: delete "bfq" prefix from cgroup filenames

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Date:   Mon, 8 Apr 2019 16:49:25 +0200
From:   Johannes Thumshirn <jthumshirn@...e.de>
To:     Paolo Valente <paolo.valente@...aro.org>
Cc:     Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, ulf.hansson@...aro.org,
        linus.walleij@...aro.org, broonie@...nel.org,
        bfq-iosched@...glegroups.com, oleksandr@...alenko.name,
        Angelo Ruocco <angeloruocco90@...il.com>
Subject: Re: [PATCH 1/1] block, bfq: delete "bfq" prefix from cgroup filenames

On Mon, Apr 08, 2019 at 04:39:35PM +0200, Paolo Valente wrote:
> From: Angelo Ruocco <angeloruocco90@...il.com>
> 
> 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].
> 
> 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.
> 
> [1] https://github.com/systemd/systemd/issues/7057

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?

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Johannes Thumshirn                            SUSE Labs Filesystems
jthumshirn@...e.de                                +49 911 74053 689
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