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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1761607367; 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=rJ5jF1KqqBtpRr4lYaVGPUnGDQslbYhlpMRXuPv0AtM=; b=acx+GaZ/3IyRJBXp7KA1NErrPT//rMvPKOxJHJZoj5KpfXo9fjcmBYbgjKgqG6BVB5kRXl DtpNkULE9kwRHtW+fa8iZuz/RQQyN/Gkncab8G5m595kp90vn7WBM+GZ9LtPi0+cpouzWD WWt6B9Fc88j+Q3xIvgjeoaHogKqZLVE= From: Roman Gushchin To: Andrew Morton Cc: linux-kernel@vger.kernel.org, Alexei Starovoitov , Suren Baghdasaryan , Michal Hocko , Shakeel Butt , Johannes Weiner , Andrii Nakryiko , JP Kobryn , linux-mm@kvack.org, cgroups@vger.kernel.org, bpf@vger.kernel.org, Martin KaFai Lau , Song Liu , Kumar Kartikeya Dwivedi , Tejun Heo , Roman Gushchin Subject: [PATCH v2 17/23] bpf: selftests: introduce read_cgroup_file() helper Date: Mon, 27 Oct 2025 16:22:00 -0700 Message-ID: <20251027232206.473085-7-roman.gushchin@linux.dev> In-Reply-To: <20251027232206.473085-1-roman.gushchin@linux.dev> References: <20251027232206.473085-1-roman.gushchin@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: yfwn38i4nx63i4u8e751p9ca1qh3pgc3 X-Rspamd-Queue-Id: AF52F20007 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1761607368-496742 X-HE-Meta: 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 smGQSSYE ym+3A+fwifTDlBoLHSx+PJQODpMuePw9MlimurtEOvTR0O/bUHUfc8N/YeP4PPZq13eXSzaPRbZ+SiSdBA+WuNxlKNwg3/rvuTym04fUGIG0Jpdo6oNSJGOaCuKpDFuqaoqqXXJKfkFHHrwtFn1uV8hy6UdwxRtZE+AZxOtwlodKiwr6RrQY/dBrQA4nFcO+GW5zAtJDxAqBEvWDnylCumMWWdgaWST+0PRULb9xn7r3Li40xqTrCLmIpHA== 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 20cede4db3ce..8fb02fe4c4aa 100644 --- a/tools/testing/selftests/bpf/cgroup_helpers.c +++ b/tools/testing/selftests/bpf/cgroup_helpers.c @@ -126,6 +126,45 @@ 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 3857304be874..9f9bb6b5d992 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, -- 2.51.0