cgroup_core02: Requires cgroup2 mounted with nsdelegate

If cgroup2 is not mounted with the nsdelegate option, this test will
fail.  It has been patched in kernel kselftests commit 4793cb599b1b
("selftests: cgroup: skip test_cgcore_lesser_ns_open when cgroup2
mounted without nsdelegate"), therefore port it to LTP as well.

This adds an additional tst_test configuration option,
needs_cgroup_nsdelegate, to check for the mount option.

Link: https://lore.kernel.org/linux-kernel/[email protected]/
Link: https://www.mail-archive.com/[email protected]/msg02400.html
Link: https://lore.kernel.org/ltp/[email protected]/
Reviewed-by: Petr Vorel <[email protected]>
Signed-off-by: Edward Liaw <[email protected]>
Signed-off-by: Petr Vorel <[email protected]>

include/tst_cgroup.h

@@ -104,6 +104,7 @@ struct tst_cg_opts {
 	 * directory as opposed to the default pid of the calling process.
 	 */
 	int test_pid;
+	int needs_nsdelegate;
 };
 
 /* A Control Group in LTP's aggregated hierarchy */

include/tst_test.h

@@ -578,6 +578,8 @@ struct tst_fs {
 	const enum tst_cg_ver needs_cgroup_ver;
 
 	const char *const *needs_cgroup_ctrls;
+
+	int needs_cgroup_nsdelegate:1;
 };
 
 /**

lib/tst_cgroup.c

@@ -71,6 +71,8 @@ struct cgroup_root {
 	/* CGroup for current test. Which may have children. */
 	struct cgroup_dir test_dir;
 
+	int nsdelegate:1;
+
 	int we_mounted_it:1;
 	/* cpuset is in compatability mode */
 	int no_cpuset_prefix:1;
@@ -344,6 +346,11 @@ static int cgroup_v1_mounted(void)
 	return !!roots[1].ver;
 }
 
+static int cgroup_v2_nsdelegate(void)
+{
+	return !!roots[0].nsdelegate;
+}
+
 static int cgroup_mounted(void)
 {
 	return cgroup_v2_mounted() || cgroup_v1_mounted();
@@ -568,6 +575,7 @@ static void cgroup_root_scan(const char *const mnt_type,
 	struct cgroup_ctrl *ctrl;
 	uint32_t ctrl_field = 0;
 	int no_prefix = 0;
+	int nsdelegate = 0;
 	char buf[BUFSIZ];
 	char *tok;
 	const int mnt_dfd = SAFE_OPEN(mnt_dir, O_PATH | O_DIRECTORY);
@@ -582,6 +590,9 @@ static void cgroup_root_scan(const char *const mnt_type,
 		if (const_ctrl)
 			add_ctrl(&ctrl_field, const_ctrl);
 	}
+	for (tok = strtok(mnt_opts, ","); tok; tok = strtok(NULL, ",")) {
+		nsdelegate |= !strcmp("nsdelegate", tok);
+	}
 
 	if (root->ver && ctrl_field == root->ctrl_field)
 		goto discard;
@@ -632,6 +643,7 @@ static void cgroup_root_scan(const char *const mnt_type,
 	root->mnt_dir.dir_fd = mnt_dfd;
 	root->ctrl_field = ctrl_field;
 	root->no_cpuset_prefix = no_prefix;
+	root->nsdelegate = nsdelegate;
 
 	for_each_ctrl(ctrl) {
 		if (has_ctrl(root->ctrl_field, ctrl))
@@ -869,6 +881,10 @@ void tst_cg_require(const char *const ctrl_name,
 
 mkdirs:
 	root = ctrl->ctrl_root;
+
+	if (options->needs_nsdelegate && cgroup_v2_mounted() && !cgroup_v2_nsdelegate())
+		tst_brk(TCONF, "Requires cgroup2 to be mounted with nsdelegate");
+
 	add_ctrl(&root->mnt_dir.ctrl_field, ctrl);
 
 	if (cgroup_ctrl_on_v2(ctrl) && options->needs_ver == TST_CG_V1) {

lib/tst_test.c

@@ -1130,6 +1130,7 @@ static void do_cgroup_requires(void)
 {
 	const struct tst_cg_opts cg_opts = {
 		.needs_ver = tst_test->needs_cgroup_ver,
+		.needs_nsdelegate = tst_test->needs_cgroup_nsdelegate,
 	};
 	const char *const *ctrl_names = tst_test->needs_cgroup_ctrls;
 

testcases/kernel/controllers/cgroup/cgroup_core02.c

@@ -121,6 +121,7 @@ static struct tst_test test = {
 	.needs_root = 1,
 	.needs_cgroup_ctrls = (const char *const[]){"memory",  NULL},
 	.needs_cgroup_ver = TST_CG_V2,
+	.needs_cgroup_nsdelegate = 1,
 	.tags = (const struct tst_tag[]) {
 		{"linux-git", "e57457641613"},
 		{"CVE", "2021-4197"},