linux-kernel - Re: [RFC PATCH bpf-next 0/3] bpf: freeze a task cgroup from bpf

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Date: Thu, 28 Mar 2024 07:58:47 -1000
From: Tejun Heo <tj@...nel.org>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Djalal Harouni <tixxdz@...il.com>, Zefan Li <lizefan.x@...edance.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...gle.com>,
	Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
	Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"open list:CONTROL GROUP (CGROUP)" <cgroups@...r.kernel.org>,
	bpf <bpf@...r.kernel.org>,
	"open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@...r.kernel.org>
Subject: Re: [RFC PATCH bpf-next 0/3] bpf: freeze a task cgroup from bpf

Hello, Alexei.

On Thu, Mar 28, 2024 at 10:32:24AM -0700, Alexei Starovoitov wrote:
> > It bothers me a bit that it's adding a dedicated interface for something
> > which already has a defined userspace interface. Would it be better to have
> > kfunc wrappers for kernel_read() and kernel_write()?
> 
> How would that look ?
> prog cannot and shouldn't open a file.

Oh, I didn't know. Why is that?

> The seq_file would be passed/pinned by user space?

Would it work if it's just "open this file, write this and then close it"?

Thanks.

-- 
tejun