[PATCH bpf-next v2 3/3] bpf: selftests: Skip kmem test when cgroup.memory=nokmem is set

[Hui Zhu]

From: Hui Zhu <zhu...@kylinos.cn>

When cgroup.memory=nokmem is set in the kernel command line, kmem
accounting is disabled. This causes the test_kmem subtest in
cgroup_iter_memcg to fail because it expects non-zero kmem values.

Fix this by checking /proc/cmdline for the nokmem parameter. If
found, verify that kmem value is zero and return early, skipping
the pipe creation test that would otherwise fail.

Signed-off-by: Hui Zhu <zhu...@kylinos.cn>
---
 .../bpf/prog_tests/cgroup_iter_memcg.c        | 30 +++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/cgroup_iter_memcg.c 
b/tools/testing/selftests/bpf/prog_tests/cgroup_iter_memcg.c
index 897b17b58df3..2b9c148cebf0 100644
--- a/tools/testing/selftests/bpf/prog_tests/cgroup_iter_memcg.c
+++ b/tools/testing/selftests/bpf/prog_tests/cgroup_iter_memcg.c
@@ -134,11 +134,41 @@ static void test_shmem(struct bpf_link *link, struct 
memcg_query *memcg_query)
        shm_unlink("/tmp_shmem");
 }
 
+static bool cmdline_has(const char *arg)
+{
+       char cmdline[4096];
+       int fd;
+       ssize_t len;
+       bool ret = false;
+
+       fd = open("/proc/cmdline", O_RDONLY);
+       if (fd < 0)
+               return false;
+
+       len = read(fd, cmdline, sizeof(cmdline) - 1);
+       close(fd);
+       if (len < 0)
+               return false;
+
+       cmdline[len] = '\0';
+       if (strstr(cmdline, arg))
+               ret = true;
+
+       return ret;
+}
+
 #define NR_PIPES 64
 static void test_kmem(struct bpf_link *link, struct memcg_query *memcg_query)
 {
        int fds[NR_PIPES][2], i;
 
+       if (cmdline_has("cgroup.memory=nokmem")) {
+               if (!ASSERT_OK(read_stats(link), "read stats"))
+                       return;
+               ASSERT_EQ(memcg_query->memcg_kmem, 0, "kmem value");
+               return;
+       }
+
        /*
         * Increase kmem value by creating pipes which will allocate some
         * kernel buffers.
-- 
2.43.0