Re: [PATCH bpf-next 3/4] selftests/bpf: enable all available cgroup v2 controllers

[Stanislav Fomichev <sdf@fomichev.me>]

On 05/22, Roman Gushchin wrote:
> Enable all available cgroup v2 controllers when setting up
> the environment for the bpf kselftests. It's required to properly test
> the bpf prog auto-detach feature. Also it will generally increase
> the code coverage.
> 
> Signed-off-by: Roman Gushchin <guro@fb.com>
> ---
>  tools/testing/selftests/bpf/cgroup_helpers.c | 58 ++++++++++++++++++++
>  1 file changed, 58 insertions(+)
> 
> diff --git a/tools/testing/selftests/bpf/cgroup_helpers.c b/tools/testing/selftests/bpf/cgroup_helpers.c
> index 6692a40a6979..4533839c0ce0 100644
> --- a/tools/testing/selftests/bpf/cgroup_helpers.c
> +++ b/tools/testing/selftests/bpf/cgroup_helpers.c
> @@ -33,6 +33,61 @@
>  	snprintf(buf, sizeof(buf), "%s%s%s", CGROUP_MOUNT_PATH, \
>  		 CGROUP_WORK_DIR, path)
>  
> +/**
> + * enable_all_controllers() - Enable all available cgroup v2 controllers
> + *
> + * Enable all available cgroup v2 controllers in order to increase
> + * the code coverage.
> + *
> + * If successful, 0 is returned.
> + */
> +int enable_all_controllers(char *cgroup_path)
> +{
> +	char path[PATH_MAX + 1];
> +	char buf[PATH_MAX];
> +	char *c, *c2;
> +	int fd, cfd;
> +	size_t len;
> +
> +	snprintf(path, sizeof(path), "%s/cgroup.controllers", cgroup_path);
> +	fd = open(path, O_RDONLY);
> +	if (fd < 0) {
> +		log_err("Opening cgroup.controllers: %s", path);
> +		return -1;
> +	}
> +
> +	len = read(fd, buf, sizeof(buf) - 1);
> +	if (len < 0) {
> +		close(fd);
> +		log_err("Reading cgroup.controllers: %s", path);
> +		return -1;
> +	}
> +
> +	close(fd);
> +
> +	/* No controllers available? We're probably on cgroup v1. */
> +	if (len == 0)
> +		return 0;
> +
> +	snprintf(path, sizeof(path), "%s/cgroup.subtree_control", cgroup_path);
> +	cfd = open(path, O_RDWR);
> +	if (cfd < 0) {
> +		log_err("Opening cgroup.subtree_control: %s", path);
> +		return -1;
> +	}
> +

[..]
> +	buf[len] = 0;
nit: move this up a bit? Right after:

	if (len < 0) {
		...
	}
	buf[len] = 0;
	close(fd);

I was actually writing a comment about missing buf[len]=0 until I
somehow spotted it :-)

> +	for (c = strtok_r(buf, " ", &c2); c; c = strtok_r(NULL, " ", &c2)) {
> +		if (dprintf(cfd, "+%s\n", c) <= 0) {
> +			log_err("Enabling controller %s: %s", c, path);
> +			close(cfd);
> +			return -1;
> +		}
> +	}
> +	close(cfd);
> +	return 0;
> +}
> +
>  /**
>   * setup_cgroup_environment() - Setup the cgroup environment
>   *
> @@ -71,6 +126,9 @@ int setup_cgroup_environment(void)
>  		return 1;
>  	}
>  
> +	if (enable_all_controllers(cgroup_workdir))
> +		return 1;
> +
>  	return 0;
>  }
>  
> -- 
> 2.20.1
>