Re: [PATCH v3 2/4] selftests: cgroup: return the errno of write() in cg_write() on failure

On Fri, Apr 8, 2022 at 6:44 PM Roman Gushchin roman.gushchin@linux.dev wrote:

On Fri, Apr 08, 2022 at 06:21:55PM -0700, Yosry Ahmed wrote:

...

On Thu, Apr 7, 2022 at 9:57 PM Yosry Ahmed yosryahmed@google.com 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@google.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);
  

}

I have changed this in v4 to a cleaner implementation that either returns 0 on success or -errno on failure. I also made sure to check that the full buffer was being written, and updated cg_read() as well for the interface to be consistent.

Will send out once the discussion on patch 1 in v3 reaches a consensus.

Ok, sounds good, please feel free to add my Acked-by: Roman Gushchin roman.gushchin@linux.dev for the whole series. It looks really nice and ready for merging upstream to me.

Thanks!

Thanks a lot for reviewing it! I would appreciate it if you still took a look at the v4 version of this patch when I send it (probably early next week) as it's significantly different and includes changes to cg_read() and read_text() as well.