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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1769481906; 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=5kycmWS+Mn50NTNG9vDPdXnOmThXS8tkuWasjOZWHyE=; b=MVYbxj8bguPU/jWUxphCtMV2M4pyasjfYogGFJ2vNcT1KF2goib3pEeYc8kLCil+Me1cqA A+YE5JjAKsshrTPbuVZ0E9j1WggR0qhRanDpJE3AsiU2VhodIOexFViw0YdvUqPvkcyoBD IpQB4/liQnnBeuM18rgJmTEtSMseg/k= From: Roman Gushchin To: bpf@vger.kernel.org Cc: Michal Hocko , Alexei Starovoitov , Matt Bobrowski , Shakeel Butt , JP Kobryn , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Suren Baghdasaryan , Johannes Weiner , Andrew Morton , Roman Gushchin Subject: [PATCH bpf-next v3 11/17] bpf: selftests: introduce read_cgroup_file() helper Date: Mon, 26 Jan 2026 18:44:14 -0800 Message-ID: <20260127024421.494929-12-roman.gushchin@linux.dev> In-Reply-To: <20260127024421.494929-1-roman.gushchin@linux.dev> References: <20260127024421.494929-1-roman.gushchin@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: DBA0A160010 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: e7gmwdngf3aop3sbkawn3rqtimqhwq5b X-HE-Tag: 1769481907-579445 X-HE-Meta: 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 ATIyWS9j 4LLSyjY1NLfibseVYobeeF2GWPOHWRyJQ6Nx9T7tTWCNHX5hf2ygI5qBnF4x/a71lm9RruxTJgxNiLCNgpjlgfwP+Y6hU50E6KDD135aS1OZ5UHpSU46Q0tSP9kof2s+spmX3Er7fL649Un+k/GzWyFuk26rMi8ZGqTu8FxmH7frakZu/lzP0ryEZDZnENF2rECkUCVmk+1IGFU16JRx2ajBBpriREYUowcdADpqB3/LCs+sdQrRjgl5Vzw== 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 | 45 ++++++++++++++++++++ tools/testing/selftests/bpf/cgroup_helpers.h | 3 ++ 2 files changed, 48 insertions(+) diff --git a/tools/testing/selftests/bpf/cgroup_helpers.c b/tools/testing/selftests/bpf/cgroup_helpers.c index 20cede4db3ce..fc5f22409ce5 100644 --- a/tools/testing/selftests/bpf/cgroup_helpers.c +++ b/tools/testing/selftests/bpf/cgroup_helpers.c @@ -126,6 +126,51 @@ int enable_controllers(const char *relative_path, const char *controllers) return __enable_controllers(cgroup_path, controllers); } +static ssize_t __read_cgroup_file(const char *cgroup_path, const char *file, + char *buf, size_t size) +{ + char file_path[PATH_MAX + 1]; + ssize_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); + if (ret < 0) { + close(fd); + log_err("Reading %s", file_path); + return -1; + } + + close(fd); + return ret; +} + +/** + * read_cgroup_file() - Read from a cgroup file + * @relative_path: The cgroup path, relative to the workdir + * @file: The name of the file in cgroupfs to read from + * @buf: Buffer to read from the file + * @size: Size of the buffer + * + * Read from a file in the given cgroup's directory. + * + * If successful, the number of read bytes is returned. + */ +ssize_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..66a08b64838b 100644 --- a/tools/testing/selftests/bpf/cgroup_helpers.h +++ b/tools/testing/selftests/bpf/cgroup_helpers.h @@ -4,6 +4,7 @@ #include #include +#include #define clean_errno() (errno == 0 ? "None" : strerror(errno)) #define log_err(MSG, ...) fprintf(stderr, "(%s:%d: errno: %s) " MSG "\n", \ @@ -11,6 +12,8 @@ /* cgroupv2 related */ int enable_controllers(const char *relative_path, const char *controllers); +ssize_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, -- 2.52.0