linux-kernel - Re: [External] : Re: [PATCH] cgroup: In cgroup_no

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Message-ID: <ZR78iXWk-kTt4gf5@slm.duckdns.org>
Date:   Thu, 5 Oct 2023 08:12:25 -1000
From:   Tejun Heo <tj@...nel.org>
To:     Kamalesh Babulal <kamalesh.babulal@...cle.com>
Cc:     Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Tom Hromatka <tom.hromatka@...cle.com>,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [External] : Re: [PATCH] cgroup: In cgroup_no_v1() check v1
 controllers only

On Thu, Oct 05, 2023 at 04:51:52PM +0530, Kamalesh Babulal wrote:
> 
> 
> On 10/5/23 00:47, Tejun Heo wrote:
> > On Wed, Sep 20, 2023 at 03:55:12PM +0530, Kamalesh Babulal wrote:
> >> cgroup v1 or v2 or both controller names can be passed as arguments to
> >> the 'cgroup_no_v1' kernel parameter, though most of the controller's
> >> names are the same for both cgroup versions. This can be confusing when
> >> both versions are used interchangeably, i.e., passing cgroup_no_v1=io
> >>
> >> $ sudo dmesg |grep cgroup
> >> ...
> >> cgroup: Disabling io control group subsystem in v1 mounts
> >> cgroup: Disabled controller 'blkio'
> > 
> > So, making the printed names consistent makes sense but I'm not sure about
> > not matching "io" anymore. That's gonna break users who already use them,
> > right?
> 
> Agreed, users might pass "io" in place of "blkio", I was thinking
> in terms of cgroup v1 users, for whom it is "blkio" controller but
> as an argument, "cgroup_no_v1" makes the controllers passed to it,
> available under cgroup v2, where the controller is named "io",
> which the user may use interchangeably.
> 
> Shall I re-send the patch to print the controller legacy_name only?

Yes, let's do that.

Thanks.

-- 
tejun