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Mon, 17 Aug 2026 14:42:19 -0700 (PDT) From: Ziyang Men To: kernel-team@meta.com, Jens Axboe , Tejun Heo , Josef Bacik , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi Cc: Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Shuah Khan , Johannes Weiner , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Roman Gushchin , Shakeel Butt , JP Kobryn , Mykola Lysenko , Ziyang Men , linux-block@vger.kernel.org, bpf@vger.kernel.org, cgroups@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 0/2] block: expose blkcg io.stat to BPF Date: Mon, 17 Aug 2026 14:42:03 -0700 Message-ID: <20260817214205.723267-1-ziyang.meme@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Collecting cgroup statistics is expensive: the existing method is to open and parse a cgroup file for every cgroup of interest. The memory controller already has an efficient alternative through BPF; this series extends that model to the block I/O controller's per-device io.stat. Patch 1 adds the blkcg flush and per-device iterator. Patch 2 adds a selftest that performs direct I/O on a private loop device and compares every counter read by BPF with io.stat. === Changes since v1. - Drop the blkcg acquire/release helpers. The program reads the io controller's css from cgroup->subsys[] under RCU instead. - Remove the kfuncs that read the blkg device ID and counters; BPF programs can read those fields with BPF_CORE_READ(). - Keep the flush sleepable. It now takes a struct cgroup * and pins its CSS internally. - Make the blkg iterator take an RCU-protected CSS. Tested on VM with v7.2-rc5. Ziyang Men (2): block: add BPF kfuncs to read blkcg io.stat selftests/bpf: add test for blkcg io.stat BPF kfuncs MAINTAINERS | 1 + block/Makefile | 3 + block/blk-cgroup.c | 2 +- block/blk-cgroup.h | 1 + block/bpf_blkcg.c | 154 ++++++++++ tools/testing/selftests/bpf/cgroup_iter_io.h | 17 ++ tools/testing/selftests/bpf/config | 1 + .../selftests/bpf/prog_tests/cgroup_iter_io.c | 277 ++++++++++++++++++ .../selftests/bpf/progs/cgroup_iter_io.c | 99 +++++++ 9 files changed, 554 insertions(+), 1 deletion(-) create mode 100644 block/bpf_blkcg.c create mode 100644 tools/testing/selftests/bpf/cgroup_iter_io.h create mode 100644 tools/testing/selftests/bpf/prog_tests/cgroup_iter_io.c create mode 100644 tools/testing/selftests/bpf/progs/cgroup_iter_io.c -- 2.53.0-Meta