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Date: Fri, 5 Jan 2024 10:45:02 +0100
From: Michal =?utf-8?Q?Koutn=C3=BD?= <mkoutny@suse.com>
To: Haitao Huang <haitao.huang@linux.intel.com>
Cc: jarkko@kernel.org, dave.hansen@linux.intel.com, tj@kernel.org, 
	linux-kernel@vger.kernel.org, linux-sgx@vger.kernel.org, x86@kernel.org, 
	cgroups@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, 
	hpa@zytor.com, sohil.mehta@intel.com, zhiquan1.li@intel.com, 
	kristen@linux.intel.com, seanjc@google.com, zhanb@microsoft.com, anakrish@microsoft.com, 
	mikko.ylinen@linux.intel.com, yangjie@microsoft.com
Subject: Re: [PATCH v6 01/12] cgroup/misc: Add per resource callbacks for CSS
 events
Message-ID: <5qfjx2vvirtffkro5u6zdbbwia2bhhbjxwgij2igdnxk5hysaq@kpqboajvuzbc>
References: <20231030182013.40086-1-haitao.huang@linux.intel.com>
 <20231030182013.40086-2-haitao.huang@linux.intel.com>
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On Mon, Oct 30, 2023 at 11:20:02AM -0700, Haitao Huang <haitao.huang@linux.=
intel.com> wrote:
> From: Kristen Carlson Accardi <kristen@linux.intel.com>
>=20
> The misc cgroup controller (subsystem) currently does not perform
> resource type specific action for Cgroups Subsystem State (CSS) events:
> the 'css_alloc' event when a cgroup is created and the 'css_free' event
> when a cgroup is destroyed.
>=20
> Define callbacks for those events and allow resource providers to
> register the callbacks per resource type as needed. This will be
> utilized later by the EPC misc cgroup support implemented in the SGX
> driver.

I notice now that the callbacks are per resource and per cgroup.
I think that is an overkill that complicates misc_cg allocation code
with parent's callbacks while freeing is done by own callbacks.
It's possibly too much liberal to keep objects' lifecycle understandable
in the long term too.=20

For some uniformity, I'd suggest struct blkcg_policy array in
block/blk-cgroup.c as the precedent. (Perhaps indexed with static enum
misc_res_type instead of dynamic index assignment as
blkcg_policy_registeer() does.)

I hope you don't really need per-cgroup callbacks :-)

Michal

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