[v3,bpf-next,10/11] selftests/bpf: Add a new cgroup helper get_cgroup_hierarchy_id()

Commit Message

Yafang Shao Oct. 29, 2023, 6:14 a.m. UTC

A new cgroup helper function, get_cgroup1_hierarchy_id(), has been
introduced to obtain the ID of a cgroup1 hierarchy based on the provided
cgroup name. This cgroup name can be obtained from the /proc/self/cgroup
file.

Signed-off-by: Yafang Shao <[e-mail]>
---
 tools/testing/selftests/bpf/cgroup_helpers.c | 49 ++++++++++++++++++++++++++++
 tools/testing/selftests/bpf/cgroup_helpers.h |  1 +
 2 files changed, 50 insertions(+)

Comments

Tejun Heo Nov. 9, 2023, 9:32 p.m. UTC | #1

Hello,

On Sun, Oct 29, 2023 at 06:14:37AM +0000, Yafang Shao wrote:
> +int get_cgroup1_hierarchy_id(const char *cgrp_name)

Maybe use subsys_name or controller? cgroup name usually means the cgroup
directory name.

Thanks.

Yafang Shao Nov. 10, 2023, 2:40 a.m. UTC | #2

On Fri, Nov 10, 2023 at 5:32 AM Tejun Heo <[e-mail]> wrote:
>
> Hello,
>
> On Sun, Oct 29, 2023 at 06:14:37AM +0000, Yafang Shao wrote:
> > +int get_cgroup1_hierarchy_id(const char *cgrp_name)
>
> Maybe use subsys_name or controller? cgroup name usually means the cgroup
> directory name.
>

will use subsys_name instead. Thanks for your suggestion.

Patch

diff --git a/tools/testing/selftests/bpf/cgroup_helpers.c b/tools/testing/selftests/bpf/cgroup_helpers.c
index 63bfa72..d75bb87 100644
--- a/tools/testing/selftests/bpf/cgroup_helpers.c
+++ b/tools/testing/selftests/bpf/cgroup_helpers.c
@@ -637,3 +637,52 @@  unsigned long long get_classid_cgroup_id(void)
 	format_classid_path(cgroup_workdir);
 	return get_cgroup_id_from_path(cgroup_workdir);
 }
+
+/**
+ * get_cgroup1_hierarchy_id - Retrieves the ID of a cgroup1 hierarchy from the cgroup1 name
+ * @cgrp_name: The cgroup1 name, which can be retrieved from /proc/self/cgroup.
+ */
+int get_cgroup1_hierarchy_id(const char *cgrp_name)
+{
+	char *c, *c2, *c3, *c4;
+	bool found = false;
+	char line[1024];
+	FILE *file;
+	int i, id;
+
+	if (!cgrp_name)
+		return -1;
+
+	file = fopen("/proc/self/cgroup", "r");
+	if (!file) {
+		log_err("fopen /proc/self/cgroup");
+		return -1;
+	}
+
+	while (fgets(line, 1024, file)) {
+		i = 0;
+		for (c = strtok_r(line, ":", &c2); c && i < 2; c = strtok_r(NULL, ":", &c2)) {
+			if (i == 0) {
+				id = strtol(c, NULL, 10);
+			} else if (i == 1) {
+				if (!strcmp(c, cgrp_name)) {
+					found = true;
+					break;
+				}
+
+				/* Multiple subsystems may share one single mount point */
+				for (c3 = strtok_r(c, ",", &c4); c3;
+				     c3 = strtok_r(NULL, ",", &c4)) {
+					if (!strcmp(c, cgrp_name)) {
+						found = true;
+						break;
+					}
+				}
+			}
+			i++;
+		}
+		if (found)
+			break;
+	}
+	return found ? id : -1;
+}
diff --git a/tools/testing/selftests/bpf/cgroup_helpers.h b/tools/testing/selftests/bpf/cgroup_helpers.h
index e71da4e..a80c417 100644
--- a/tools/testing/selftests/bpf/cgroup_helpers.h
+++ b/tools/testing/selftests/bpf/cgroup_helpers.h
@@ -20,6 +20,7 @@  int write_cgroup_file_parent(const char *relative_path, const char *file,
 int create_and_get_cgroup(const char *relative_path);
 void remove_cgroup(const char *relative_path);
 unsigned long long get_cgroup_id(const char *relative_path);
+int get_cgroup1_hierarchy_id(const char *cgrp_name);
 
 int join_cgroup(const char *relative_path);
 int join_root_cgroup(void);