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Mon, 16 Feb 2026 10:30:18 -0800 (PST) Message-ID: Date: Mon, 16 Feb 2026 10:30:17 -0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH bpf-next v2 1/3] bpf: Use bpf_core_enum_value for stats in cgroup_iter_memcg To: Hui Zhu , Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Shuah Khan , Hui Zhu , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org References: <24ac7bab25d8d2a24a35ab87a5283263eb6a4575.1770965805.git.zhuhui@kylinos.cn> Content-Language: en-US From: "JP Kobryn (Meta)" In-Reply-To: <24ac7bab25d8d2a24a35ab87a5283263eb6a4575.1770965805.git.zhuhui@kylinos.cn> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2/12/26 11:23 PM, Hui Zhu wrote: > From: Hui Zhu > > Replace hardcoded enum values with bpf_core_enum_value() calls in > cgroup_iter_memcg test to improve portability across different > kernel versions. > > The change adds runtime enum value resolution for: > - node_stat_item: NR_ANON_MAPPED, NR_SHMEM, NR_FILE_PAGES, > NR_FILE_MAPPED > - memcg_stat_item: MEMCG_KMEM > - vm_event_item: PGFAULT > > This ensures the BPF program can adapt to enum value changes > between kernel versions, returning early if any enum value is > unavailable (returns 0). > > Signed-off-by: Hui Zhu > --- > .../selftests/bpf/progs/cgroup_iter_memcg.c | 41 +++++++++++++++---- > 1 file changed, 34 insertions(+), 7 deletions(-) > > diff --git a/tools/testing/selftests/bpf/progs/cgroup_iter_memcg.c b/tools/testing/selftests/bpf/progs/cgroup_iter_memcg.c > index 59fb70a3cc50..b020951dd7e6 100644 > --- a/tools/testing/selftests/bpf/progs/cgroup_iter_memcg.c > +++ b/tools/testing/selftests/bpf/progs/cgroup_iter_memcg.c > @@ -15,6 +15,8 @@ int cgroup_memcg_query(struct bpf_iter__cgroup *ctx) > struct cgroup *cgrp = ctx->cgroup; > struct cgroup_subsys_state *css; > struct mem_cgroup *memcg; > + int ret = 1; > + int idx; > > if (!cgrp) > return 1; > @@ -26,14 +28,39 @@ int cgroup_memcg_query(struct bpf_iter__cgroup *ctx) > > bpf_mem_cgroup_flush_stats(memcg); > > - memcg_query.nr_anon_mapped = bpf_mem_cgroup_page_state(memcg, NR_ANON_MAPPED); > - memcg_query.nr_shmem = bpf_mem_cgroup_page_state(memcg, NR_SHMEM); > - memcg_query.nr_file_pages = bpf_mem_cgroup_page_state(memcg, NR_FILE_PAGES); > - memcg_query.nr_file_mapped = bpf_mem_cgroup_page_state(memcg, NR_FILE_MAPPED); > - memcg_query.memcg_kmem = bpf_mem_cgroup_page_state(memcg, MEMCG_KMEM); > - memcg_query.pgfault = bpf_mem_cgroup_vm_events(memcg, PGFAULT); > + idx = bpf_core_enum_value(enum node_stat_item, NR_ANON_MAPPED); > + if (idx == 0) > + goto out; > + memcg_query.nr_anon_mapped = bpf_mem_cgroup_page_state(memcg, idx); > > + idx = bpf_core_enum_value(enum node_stat_item, NR_SHMEM); > + if (idx == 0) > + goto out; > + memcg_query.nr_shmem = bpf_mem_cgroup_page_state(memcg, idx); > + > + idx = bpf_core_enum_value(enum node_stat_item, NR_FILE_PAGES); > + if (idx == 0) > + goto out; > + memcg_query.nr_file_pages = bpf_mem_cgroup_page_state(memcg, idx); > + > + idx = bpf_core_enum_value(enum node_stat_item, NR_FILE_MAPPED); > + if (idx == 0) > + goto out; > + memcg_query.nr_file_mapped = bpf_mem_cgroup_page_state(memcg, idx); > + > + idx = bpf_core_enum_value(enum memcg_stat_item, MEMCG_KMEM); > + if (idx == 0) > + goto out; > + memcg_query.memcg_kmem = bpf_mem_cgroup_page_state(memcg, idx); > + > + idx = bpf_core_enum_value(enum vm_event_item, PGFAULT); > + if (idx == 0) > + goto out; This is getting messy. Most of these values should be on any system regardless of boot-params. I was expecting you would make the call inline. Let's simplify this whole series. This selftest only needs to exercise bpf_mem_cgroup_page_state() and bpf_mem_cgroup_vm_events(). I think we can remove the kmem subtest altogether and still have the coverage we need. You could then call bpf_core_enum_value() inline as an argument to the kfuncs above and not need to check if they exist (just let them give you the host-specific co-re value).