Fix test_cgroup_iter_memcg issues found during back-porting

From: Hui Zhu <[email protected]>

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.

Remove the kmem subtest altogether since the remaining subtests (shmem, file, pgfault) already provide sufficient coverage for the cgroup iter memcg functionality.

Signed-off-by Hui Zhu <[email protected]>

---
  .../testing/selftests/bpf/cgroup_iter_memcg.h |  2 --
  .../bpf/prog_tests/cgroup_iter_memcg.c        | 28 -------------------
  .../selftests/bpf/progs/cgroup_iter_memcg.c   |  1 -
  3 files changed, 31 deletions(-)

tools/testing/selftests/bpf/cgroup_iter_memcg.h +0 -2

index 3f59b127943b..ff20ec537164 100644
@@ -9,8 +9,6 @@ struct memcg_query {
  	unsigned long nr_shmem;
  	unsigned long nr_file_pages;
  	unsigned long nr_file_mapped;
-	/* some memcg_stat_item */
-	unsigned long memcg_kmem;
  	/* some vm_event_item */
  	unsigned long pgfault;
  };

tools/testing/selftests/bpf/prog_tests/cgroup_iter_memcg.c +0 -28

index a5afd16705f0..88fc3e83d2b7 100644
@@ -126,32 +126,6 @@ static void test_shmem(struct bpf_link *link, struct memcg_query *memcg_query)
  	shm_unlink("/tmp_shmem");
  }
 
-#define NR_PIPES 64
-static void test_kmem(struct bpf_link *link, struct memcg_query *memcg_query)
-{
-	int fds[NR_PIPES][2], i;
-
-	/*
-	 * Increase kmem value by creating pipes which will allocate some
-	 * kernel buffers.
-	 */
-	for (i = 0; i < NR_PIPES; i++) {
-		if (!ASSERT_OK(pipe(fds[i]), "pipe"))
-			goto cleanup;
-	}
-
-	if (!ASSERT_OK(read_stats(link), "read stats"))
-		goto cleanup;
-
-	ASSERT_GT(memcg_query->memcg_kmem, 0, "kmem value");
-
-cleanup:
-	for (i = i - 1; i >= 0; i--) {
-		close(fds[i][0]);
-		close(fds[i][1]);
-	}
-}
-
  static void test_pgfault(struct bpf_link *link, struct memcg_query *memcg_query)
  {
  	void *map;

@@ -209,8 +183,6 @@ void test_cgroup_iter_memcg(void)
  		test_shmem(link, &skel->data_query->memcg_query);
  	if (test__start_subtest("cgroup_iter_memcg__file"))
  		test_file(link, &skel->data_query->memcg_query);
-	if (test__start_subtest("cgroup_iter_memcg__kmem"))
-		test_kmem(link, &skel->data_query->memcg_query);
  	if (test__start_subtest("cgroup_iter_memcg__pgfault"))
  		test_pgfault(link, &skel->data_query->memcg_query);
 

tools/testing/selftests/bpf/progs/cgroup_iter_memcg.c +0 -0

index 59fb70a3cc50..12f79a44133e 100644

From: Hui Zhu <[email protected]>

Replace hardcoded enum values with bpf_core_enum_value() calls in cgroup_iter_memcg test to improve portability across different kernel versions.

The change adds runtime enum value resolution for:
- node_stat_item: NR_ANON_MAPPED, NR_SHMEM, NR_FILE_PAGES, NR_FILE_MAPPED
- vm_event_item: PGFAULT

This ensures the BPF program can adapt to enum value changes between kernel versions.

Signed-off-by Hui Zhu <[email protected]>

---
  .../selftests/bpf/progs/cgroup_iter_memcg.c     | 17 ++++++++++++-----
  1 file changed, 12 insertions(+), 5 deletions(-)

tools/testing/selftests/bpf/progs/cgroup_iter_memcg.c +5 -5

index 12f79a44133e..06a385c9d85b 100644
@@ -26,11 +26,18 @@ int cgroup_memcg_query(struct bpf_iter__cgroup *ctx)
 
  	bpf_mem_cgroup_flush_stats(memcg);
 
-	memcg_query.nr_anon_mapped = bpf_mem_cgroup_page_state(memcg, NR_ANON_MAPPED);
-	memcg_query.nr_shmem = bpf_mem_cgroup_page_state(memcg, NR_SHMEM);
-	memcg_query.nr_file_pages = bpf_mem_cgroup_page_state(memcg, NR_FILE_PAGES);
-	memcg_query.nr_file_mapped = bpf_mem_cgroup_page_state(memcg, NR_FILE_MAPPED);
-	memcg_query.pgfault = bpf_mem_cgroup_vm_events(memcg, PGFAULT);
+	memcg_query.nr_anon_mapped = bpf_mem_cgroup_page_state(
+		memcg,
+		bpf_core_enum_value(enum node_stat_item, NR_ANON_MAPPED));
+	memcg_query.nr_shmem = bpf_mem_cgroup_page_state(
+		memcg, bpf_core_enum_value(enum node_stat_item, NR_SHMEM));

From: Hui Zhu <[email protected]>

When back-porting test_progs to different kernel versions, I encountered an issue where the test_cgroup_iter_memcg test would falsely pass even when bpf_mem_cgroup_page_state() failed.

This patch adds explicit checks to ensure bpf_mem_cgroup_page_state() doesn't return -1 before validating the actual statistics values.

Signed-off-by Hui Zhu <[email protected]>

---
  .../selftests/bpf/prog_tests/cgroup_iter_memcg.c       | 10 ++++++++++
  1 file changed, 10 insertions(+)

tools/testing/selftests/bpf/prog_tests/cgroup_iter_memcg.c +8 -0

index 88fc3e83d2b7..9eadfbd3fdb9 100644
@@ -53,6 +53,8 @@ static void test_anon(struct bpf_link *link, struct memcg_query *memcg_query)
  	if (!ASSERT_OK(read_stats(link), "read stats"))
  		goto cleanup;
 
+	ASSERT_NEQ(memcg_query->nr_anon_mapped, (unsigned long)-1,
+		  "bpf_mem_cgroup_page_state NR_ANON_MAPPED");
  	ASSERT_GT(memcg_query->nr_anon_mapped, 0, "final anon mapped val");
 
  cleanup:

@@ -88,6 +90,10 @@ static void test_file(struct bpf_link *link, struct memcg_query *memcg_query)
  	if (!ASSERT_OK(read_stats(link), "read stats"))
  		goto cleanup_map;
 
+	ASSERT_NEQ(memcg_query->nr_file_pages, (unsigned long)-1,
+		  "bpf_mem_cgroup_page_state NR_FILE_PAGES");
+	ASSERT_NEQ(memcg_query->nr_file_mapped, (unsigned long)-1,
+		  "bpf_mem_cgroup_page_state NR_FILE_MAPPED");
  	ASSERT_GT(memcg_query->nr_file_pages, 0, "final file value");
  	ASSERT_GT(memcg_query->nr_file_mapped, 0, "final file mapped value");
 

@@ -119,6 +125,8 @@ static void test_shmem(struct bpf_link *link, struct memcg_query *memcg_query)
  	if (!ASSERT_OK(read_stats(link), "read stats"))
  		goto cleanup;
 
+	ASSERT_NEQ(memcg_query->nr_shmem, (unsigned long)-1,
+		  "bpf_mem_cgroup_page_state NR_SHMEM");
  	ASSERT_GT(memcg_query->nr_shmem, 0, "final shmem value");
 
  cleanup: