From: Tejun Heo <tj@kernel.org>
To: Ziyang Men <ziyang.meme@gmail.com>
Cc: "Jens Axboe" <axboe@kernel.dk>,
"Josef Bacik" <josef@toxicpanda.com>,
"Alexei Starovoitov" <ast@kernel.org>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Andrii Nakryiko" <andrii@kernel.org>,
"Eduard Zingerman" <eddyz87@gmail.com>,
"Kumar Kartikeya Dwivedi" <memxor@gmail.com>,
"Martin KaFai Lau" <martin.lau@linux.dev>,
"Song Liu" <song@kernel.org>,
"Yonghong Song" <yonghong.song@linux.dev>,
"Jiri Olsa" <jolsa@kernel.org>,
"Emil Tsalapatis" <emil@etsalapatis.com>,
"Shuah Khan" <shuah@kernel.org>,
"Johannes Weiner" <hannes@cmpxchg.org>,
"Michal Koutný" <mkoutny@suse.com>,
"Roman Gushchin" <roman.gushchin@linux.dev>,
"Shakeel Butt" <shakeel.butt@linux.dev>,
"JP Kobryn" <inwardvessel@gmail.com>,
"Mykola Lysenko" <mykolal@meta.com>,
kernel-team@meta.com, linux-block@vger.kernel.org,
bpf@vger.kernel.org, cgroups@vger.kernel.org,
linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] block: add BPF kfuncs to read blkcg io.stat
Date: Mon, 10 Aug 2026 10:00:55 -1000 [thread overview]
Message-ID: <anot9w6mg9538RWm@slm.duckdns.org> (raw)
In-Reply-To: <20260807193732.4073299-2-ziyang.meme@gmail.com>
Hello,
On Fri, Aug 07, 2026 at 12:37:31PM -0700, Ziyang Men wrote:
> +__bpf_kfunc struct blkcg *bpf_get_root_blkcg(void)
> +__bpf_kfunc struct blkcg *bpf_get_blkcg(struct cgroup_subsys_state *css)
> +__bpf_kfunc void bpf_put_blkcg(struct blkcg *blkcg)
> +__bpf_kfunc void bpf_blkcg_flush_stats(struct blkcg *blkcg)
I wonder whether making the above deal with css's would make more sense so
that we don't end up with per-subsystem iterators. If casting to per-subsys
type is necessary, we can provide RCU protected cast kfucns.
> +__bpf_kfunc u64 bpf_blkg_iostat_bytes(struct blkcg_gq *blkg,
> + enum blkg_iostat_type rw)
> +__bpf_kfunc u64 bpf_blkg_iostat_ios(struct blkcg_gq *blkg,
> + enum blkg_iostat_type rw)
> +__bpf_kfunc u64 bpf_blkg_dev(struct blkcg_gq *blkg)
Ignoring 32bit split reads (do we really care for BPF accesses?), the above
can easily be done with BPF_CORE_READ(), right?
Thanks.
--
tejun
next prev parent reply other threads:[~2026-08-10 20:00 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-07 19:37 [PATCH 0/2] block: expose blkcg io.stat to BPF Ziyang Men
2026-08-07 19:37 ` [PATCH 1/2] block: add BPF kfuncs to read blkcg io.stat Ziyang Men
2026-08-10 20:00 ` Tejun Heo [this message]
2026-08-10 22:46 ` Ziyang Men
2026-08-11 0:17 ` JP Kobryn
2026-08-07 19:37 ` [PATCH 2/2] selftests/bpf: add test for blkcg io.stat BPF kfuncs Ziyang Men
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