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

[Roman Gushchin <guro@fb.com>]

On Wed, May 22, 2019 at 03:18:43PM -0700, Stanislav Fomichev wrote:
> 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:

Ok, np. Thanks!