selftests: cgroup: Optionally set up v1 environment

Use the missing mount of the unifier hierarchy as a hint of legacy
system and prepare our own named v1 hierarchy for tests.

The code is only in test_core.c and not cgroup_util.c because other
selftests are related to controllers which will be exposed on v2
hierarchy but named hierarchies are only v1 thing.

Signed-off-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/tools/testing/selftests/cgroup/test_core.c b/tools/testing/selftests/cgroup/test_core.c
index 338e276aae5da8742dce3842191a67baf6ea0806..452c2abf9794e4016088233b0db29b9d89c0fda0 100644 (file)
--- a/tools/testing/selftests/cgroup/test_core.c
+++ b/tools/testing/selftests/cgroup/test_core.c
@@ -5,6 +5,8 @@
 #include <linux/sched.h>
 #include <sys/types.h>
 #include <sys/mman.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
 #include <sys/wait.h>
 #include <unistd.h>
 #include <fcntl.h>
@@ -863,6 +865,38 @@ cleanup:
        return ret;
 }
 
+static int setup_named_v1_root(char *root, size_t len, const char *name)
+{
+       char options[PATH_MAX];
+       int r;
+
+       r = snprintf(root, len, "/mnt/cg_selftest");
+       if (r < 0)
+               return r;
+
+       r = snprintf(options, sizeof(options), "none,name=%s", name);
+       if (r < 0)
+               return r;
+
+       r = mkdir(root, 0755);
+       if (r < 0 && errno != EEXIST)
+               return r;
+
+       r = mount("none", root, "cgroup", 0, options);
+       if (r < 0)
+               return r;
+
+       return 0;
+}
+
+static void cleanup_named_v1_root(char *root)
+{
+       if (!cg_test_v1_named)
+               return;
+       umount(root);
+       rmdir(root);
+}
+
 #define T(x) { x, #x }
 struct corecg_test {
        int (*fn)(const char *root);
@@ -888,13 +922,18 @@ int main(int argc, char *argv[])
        char root[PATH_MAX];
        int i, ret = EXIT_SUCCESS;
 
-       if (cg_find_unified_root(root, sizeof(root), &nsdelegate))
-               ksft_exit_skip("cgroup v2 isn't mounted\n");
+       if (cg_find_unified_root(root, sizeof(root), &nsdelegate)) {
+               if (setup_named_v1_root(root, sizeof(root), CG_NAMED_NAME))
+                       ksft_exit_skip("cgroup v2 isn't mounted and could not setup named v1 hierarchy\n");
+               cg_test_v1_named = true;
+               goto post_v2_setup;
+       }
 
        if (cg_read_strstr(root, "cgroup.subtree_control", "memory"))
                if (cg_write(root, "cgroup.subtree_control", "+memory"))
                        ksft_exit_skip("Failed to set memory controller\n");
 
+post_v2_setup:
        for (i = 0; i < ARRAY_SIZE(tests); i++) {
                switch (tests[i].fn(root)) {
                case KSFT_PASS:
@@ -910,5 +949,6 @@ int main(int argc, char *argv[])
                }
        }
 
+       cleanup_named_v1_root(root);
        return ret;
 }