Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
Date:   Thu,  7 Apr 2022 22:42:42 +0000
In-Reply-To: <20220407224244.1374102-1-yosryahmed@google.com>
Message-Id: <20220407224244.1374102-3-yosryahmed@google.com>
Mime-Version: 1.0
References: <20220407224244.1374102-1-yosryahmed@google.com>
Subject: [PATCH v2 2/4] selftests: cgroup: return the errno of write() in
 cg_write() on failure
From:   Yosry Ahmed <yosryahmed@google.com>
To:     Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@kernel.org>,
        Shakeel Butt <shakeelb@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Roman Gushchin <roman.gushchin@linux.dev>
Cc:     David Rientjes <rientjes@google.com>, Tejun Heo <tj@kernel.org>,
        Zefan Li <lizefan.x@bytedance.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Shuah Khan <shuah@kernel.org>, Yu Zhao <yuzhao@google.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Wei Xu <weixugc@google.com>, Greg Thelen <gthelen@google.com>,
        Chen Wandun <chenwandun@huawei.com>,
        Vaibhav Jain <vaibhav@linux.ibm.com>, Huang@google.com,
        Ying <ying.huang@intel.com>,
        "=?UTF-8?q?Michal=20Koutn=C3=BD?=" <mkoutny@suse.com>,
        Tim Chen <tim.c.chen@linux.intel.com>, cgroups@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linux-kselftest@vger.kernel.org,
        Yosry Ahmed <yosryahmed@google.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Currently, cg_write() returns 0 on success and -1 on failure. Modify it
to return the errno of write() syscall on failure.

Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
---
 tools/testing/selftests/cgroup/cgroup_util.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/cgroup/cgroup_util.c b/tools/testing/selftests/cgroup/cgroup_util.c
index dbaa7aabbb4a..ef76db6026aa 100644
--- a/tools/testing/selftests/cgroup/cgroup_util.c
+++ b/tools/testing/selftests/cgroup/cgroup_util.c
@@ -48,6 +48,8 @@ static ssize_t write_text(const char *path, char *buf, ssize_t len)
 
 	len = write(fd, buf, len);
 	if (len < 0) {
+		/* preserve the errno of write() */
+		len = errno;
 		close(fd);
 		return len;
 	}
@@ -177,17 +179,16 @@ long cg_read_lc(const char *cgroup, const char *control)
 	return cnt;
 }
 
+/* Returns 0 on success, or the errno of write() on failure. */
 int cg_write(const char *cgroup, const char *control, char *buf)
 {
 	char path[PATH_MAX];
-	ssize_t len = strlen(buf);
+	ssize_t len = strlen(buf), ret;
 
 	snprintf(path, sizeof(path), "%s/%s", cgroup, control);
 
-	if (write_text(path, buf, len) == len)
-		return 0;
-
-	return -1;
+	ret = write_text(path, buf, len);
+	return ret == len ? 0 : ret;
 }
 
 int cg_find_unified_root(char *root, size_t len)
-- 
2.35.1.1178.g4f1659d476-goog