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Originaldate: Tue Mar 3, 2020 at 8:50 AM
Originalfrom: "Shakeel Butt" <shakeelb@google.com>
Original: =?utf-8?q?Hi_Daniel,
 =0D=0A=0D=0AOn_Mon,_Mar_2,_2020_at_5:42_PM_Daniel_Xu_?=
 =?utf-8?q?<dxu@dxuuu.xyz>_wrote:=0D=0A>=0D=0A>_User_extended_attributes_a?=
 =?utf-8?q?re_useful_as_metadata_storage_for_kernfs=0D=0A>_consumers_like_?=
 =?utf-8?q?cgroups._Especially_in_the_case_of_cgroups,_it_is_useful=0D=0A>?=
 =?utf-8?q?_to_have_a_central_metadata_store_that_multiple_processes/servi?=
 =?utf-8?q?ces_can=0D=0A>_use_to_coordinate_actions.=0D=0A>=0D=0A>_A_concr?=
 =?utf-8?q?ete_example_is_for_userspace_out_of_memory_killers._We_want_to?=
 =?utf-8?q?=0D=0A>_let_delegated_cgroup_subtree_owners_(running_as_non-roo?=
 =?utf-8?q?t)_to_be_able_to=0D=0A>_say_"please_avoid_killing_this_cgroup".?=
 =?utf-8?q?_In_server_environments_this_is=0D=0A>_less_important_as_everyo?=
 =?utf-8?q?ne_is_running_as_root.=0D=0A=0D=0AI_would_recommend_removing_th?=
 =?utf-8?q?e_"everyone_is_running_as_root"_statement=0D=0Aas_it_is_not_gen?=
 =?utf-8?q?erally_true.=0D=0A=0D=0AShakeel=0D=0A?=
In-Reply-To: <CALvZod5m3otRRqcLBebbgiZbhoYWAMbMg+ESkacJuj64OP
 =H4Q@mail.gmail.com>
Date:   Tue, 03 Mar 2020 11:20:32 -0800
Cc:     "Cgroups" <cgroups@vger.kernel.org>, "Tejun Heo" <tj@kernel.org>,
        "Li Zefan" <lizefan@huawei.com>,
        "Johannes Weiner" <hannes@cmpxchg.org>,
        "LKML" <linux-kernel@vger.kernel.org>,
        "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
        "Kernel Team" <kernel-team@fb.com>
Subject: Re: [PATCH 0/2] Support user xattrs in cgroupfs
From:   "Daniel Xu" <dxu@dxuuu.xyz>
To:     "Shakeel Butt" <shakeelb@google.com>
Message-Id: <C11FZ3TMTIH1.2KP5NIUPPQBWT@dlxu-fedora-R90QNFJV>
Sender: linux-kernel-owner@vger.kernel.org
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On Tue Mar 3, 2020 at 8:50 AM, Shakeel Butt wrote:
> Hi Daniel,
>
>=20
> On Mon, Mar 2, 2020 at 5:42 PM Daniel Xu <dxu@dxuuu.xyz> wrote:
> >
> > User extended attributes are useful as metadata storage for kernfs
> > consumers like cgroups. Especially in the case of cgroups, it is useful
> > to have a central metadata store that multiple processes/services can
> > use to coordinate actions.
> >
> > A concrete example is for userspace out of memory killers. We want to
> > let delegated cgroup subtree owners (running as non-root) to be able to
> > say "please avoid killing this cgroup". In server environments this is
> > less important as everyone is running as root.
>
>=20
> I would recommend removing the "everyone is running as root" statement
> as it is not generally true.
>
>=20
> Shakeel

Good point, thanks.