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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1745811414; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=32V32g0Ec/6L0UXIreJ3hArx8mY8wFKy2VxIfcAawIw=; b=lrtnBPLNXgwRxE1ROADeMOVv/joeCnNWdE2cgUBZ3JDih4j+ujB3VSZxNkwMdMJuK4gH9H nRnU9Y8dG1fSA0AJ5otgKGfEDeJpapwRWBeLLpLMP9GfKHOHKBZoFx3AGGmjOq4+i9Owtl PE1H4gahuHDezIQUEP649NIu+NInKaY= From: Roman Gushchin To: linux-kernel@vger.kernel.org Cc: Andrew Morton , Alexei Starovoitov , Johannes Weiner , Michal Hocko , Shakeel Butt , Suren Baghdasaryan , David Rientjes , Josh Don , Chuyi Zhou , cgroups@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org, Roman Gushchin Subject: [PATCH rfc 07/12] bpf: selftests: introduce read_cgroup_file() helper Date: Mon, 28 Apr 2025 03:36:12 +0000 Message-ID: <20250428033617.3797686-8-roman.gushchin@linux.dev> In-Reply-To: <20250428033617.3797686-1-roman.gushchin@linux.dev> References: <20250428033617.3797686-1-roman.gushchin@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: E40C580004 X-Stat-Signature: er1do4bztzbjmyamg751nonizs3pyugx X-Rspam-User: X-HE-Tag: 1745811415-204735 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Implement read_cgroup_file() helper to read from cgroup control files, e.g. statistics. Signed-off-by: Roman Gushchin --- tools/testing/selftests/bpf/cgroup_helpers.c | 39 ++++++++++++++++++++ tools/testing/selftests/bpf/cgroup_helpers.h | 2 + 2 files changed, 41 insertions(+) diff --git a/tools/testing/selftests/bpf/cgroup_helpers.c b/tools/testing/selftests/bpf/cgroup_helpers.c index e4535451322e..3ffd4b764f91 100644 --- a/tools/testing/selftests/bpf/cgroup_helpers.c +++ b/tools/testing/selftests/bpf/cgroup_helpers.c @@ -125,6 +125,45 @@ int enable_controllers(const char *relative_path, const char *controllers) return __enable_controllers(cgroup_path, controllers); } +static size_t __read_cgroup_file(const char *cgroup_path, const char *file, + char *buf, size_t size) +{ + char file_path[PATH_MAX + 1]; + size_t ret; + int fd; + + snprintf(file_path, sizeof(file_path), "%s/%s", cgroup_path, file); + fd = open(file_path, O_RDONLY); + if (fd < 0) { + log_err("Opening %s", file_path); + return -1; + } + + ret = read(fd, buf, size); + close(fd); + return ret; +} + +/** + * read_cgroup_file() - Read to a cgroup file + * @relative_path: The cgroup path, relative to the workdir + * @file: The name of the file in cgroupfs to read to + * @buf: Buffer to read from the file + * @size: Size of the buffer + * + * Read to a file in the given cgroup's directory. + * + * If successful, the number of read bytes is returned. + */ +size_t read_cgroup_file(const char *relative_path, const char *file, + char *buf, size_t size) +{ + char cgroup_path[PATH_MAX - 24]; + + format_cgroup_path(cgroup_path, relative_path); + return __read_cgroup_file(cgroup_path, file, buf, size); +} + static int __write_cgroup_file(const char *cgroup_path, const char *file, const char *buf) { diff --git a/tools/testing/selftests/bpf/cgroup_helpers.h b/tools/testing/selftests/bpf/cgroup_helpers.h index 502845160d88..821cb76db1f7 100644 --- a/tools/testing/selftests/bpf/cgroup_helpers.h +++ b/tools/testing/selftests/bpf/cgroup_helpers.h @@ -11,6 +11,8 @@ /* cgroupv2 related */ int enable_controllers(const char *relative_path, const char *controllers); +size_t read_cgroup_file(const char *relative_path, const char *file, + char *buf, size_t size); int write_cgroup_file(const char *relative_path, const char *file, const char *buf); int write_cgroup_file_parent(const char *relative_path, const char *file, -- 2.49.0.901.g37484f566f-goog