linux-kernel - [PATCH v3 2/4] selftests: cgroup: return the errno of write() in cg

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Date:   Fri,  8 Apr 2022 04:57:41 +0000
From:   Yosry Ahmed <yosryahmed@...gle.com>
To:     Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>
Cc:     David Rientjes <rientjes@...gle.com>, Tejun Heo <tj@...nel.org>,
        Zefan Li <lizefan.x@...edance.com>,
        Jonathan Corbet <corbet@....net>,
        Shuah Khan <shuah@...nel.org>, Yu Zhao <yuzhao@...gle.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Wei Xu <weixugc@...gle.com>, Greg Thelen <gthelen@...gle.com>,
        Chen Wandun <chenwandun@...wei.com>,
        Vaibhav Jain <vaibhav@...ux.ibm.com>,
        "Michal Koutný" <mkoutny@...e.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>, cgroups@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
        Yosry Ahmed <yosryahmed@...gle.com>
Subject: [PATCH v3 2/4] selftests: cgroup: return the errno of write() in
 cg_write() on failure

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

Signed-off-by: Yosry Ahmed <yosryahmed@...gle.com>
---
 tools/testing/selftests/cgroup/cgroup_util.c | 32 +++++++++++---------
 1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/tools/testing/selftests/cgroup/cgroup_util.c b/tools/testing/selftests/cgroup/cgroup_util.c
index dbaa7aabbb4a..3b6bb09985fa 100644
--- a/tools/testing/selftests/cgroup/cgroup_util.c
+++ b/tools/testing/selftests/cgroup/cgroup_util.c
@@ -38,23 +38,23 @@ static ssize_t read_text(const char *path, char *buf, size_t max_len)
 	return len;
 }
 
-static ssize_t write_text(const char *path, char *buf, ssize_t len)
+/*
+ * Returns:
+ *	success -> 0
+ *	open() failure -> -1
+ *	write() failure -> errno
+ */
+static int write_text(const char *path, char *buf, ssize_t len)
 {
-	int fd;
+	int fd, ret;
 
 	fd = open(path, O_WRONLY | O_APPEND);
 	if (fd < 0)
 		return fd;
 
-	len = write(fd, buf, len);
-	if (len < 0) {
-		close(fd);
-		return len;
-	}
-
+	ret = write(fd, buf, len) < 0 ? errno : 0;
 	close(fd);
-
-	return len;
+	return ret;
 }
 
 char *cg_name(const char *root, const char *name)
@@ -177,17 +177,19 @@ long cg_read_lc(const char *cgroup, const char *control)
 	return cnt;
 }
 
+/*
+ * Returns:
+ *	success -> 0
+ *	open() failure -> -1
+ *	write() failure -> errno
+ */
 int cg_write(const char *cgroup, const char *control, char *buf)
 {
 	char path[PATH_MAX];
 	ssize_t len = strlen(buf);
 
 	snprintf(path, sizeof(path), "%s/%s", cgroup, control);
-
-	if (write_text(path, buf, len) == len)
-		return 0;
-
-	return -1;
+	return write_text(path, buf, len);
 }
 
 int cg_find_unified_root(char *root, size_t len)
-- 
2.35.1.1178.g4f1659d476-goog