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

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Message-ID: <YlDiWvL9fo0OU4Ep@carbon.dhcp.thefacebook.com>
Date:   Fri, 8 Apr 2022 18:33:14 -0700
From:   Roman Gushchin <roman.gushchin@...ux.dev>
To:     Yosry Ahmed <yosryahmed@...gle.com>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        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
Subject: Re: [PATCH v3 2/4] selftests: cgroup: return the errno of write() in
 cg_write() on failure

On Fri, Apr 08, 2022 at 04:57:41AM +0000, Yosry Ahmed wrote:
> 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

Is there a reason why we can't return errno in this case as well?
It would be more straightforward.

Otherwise the change looks good to me.