Re: [PATCH bpf 2/2] selftests/bpf: check inner map deletion

Add a test case to check whether an unsuccessful creation of an outer
map of a BTF-defined map-in-map destroys the inner map.

As bpf_object__create_map() is a static function, we cannot just call it
from the test case and then check whether a map accessible via
map->inner_map_fd has been closed. Instead, we iterate over all maps and
check whether the map "$MAP_NAME.inner" does not exist.

Signed-off-by: Martynas Pumputis <redacted>
---
 .../bpf/progs/test_map_in_map_invalid.c       | 26 ++++++++
 tools/testing/selftests/bpf/test_maps.c       | 64 ++++++++++++++++++-
 2 files changed, 89 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/bpf/progs/test_map_in_map_invalid.c

diff --git a/tools/testing/selftests/bpf/progs/test_map_in_map_invalid.c b/tools/testing/selftests/bpf/progs/test_map_in_map_invalid.c
new file mode 100644
index 000000000000..2918caea1e3d
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_map_in_map_invalid.c

@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Isovalent, Inc. */
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+struct inner {
+       __uint(type, BPF_MAP_TYPE_ARRAY);
+       __type(key, __u32);
+       __type(value, int);
+       __uint(max_entries, 4);
+};
+
+struct {
+       __uint(type, BPF_MAP_TYPE_ARRAY_OF_MAPS);
+       __uint(max_entries, 0); /* This will make map creation to fail */
+       __uint(key_size, sizeof(__u32));
+       __array(values, struct inner);
+} mim SEC(".maps");
+
+SEC("xdp_noop")

+int xdp_noop0(struct xdp_md *ctx)
+{
+       return XDP_PASS;
+}
+
+char _license[] SEC("license") = "GPL";

diff --git a/tools/testing/selftests/bpf/test_maps.c b/tools/testing/selftests/bpf/test_maps.c
index 30cbf5d98f7d..d4184dde04df 100644
--- a/tools/testing/selftests/bpf/test_maps.c
+++ b/tools/testing/selftests/bpf/test_maps.c

@@ -1153,12 +1153,16 @@ static void test_sockmap(unsigned int tasks, void *data)
 }

 #define MAPINMAP_PROG "./test_map_in_map.o"
+#define MAPINMAP_INVALID_PROG "./test_map_in_map_invalid.o"
 static void test_map_in_map(void)
 {
        struct bpf_object *obj;
        struct bpf_map *map;
        int mim_fd, fd, err;
        int pos = 0;
+       struct bpf_map_info info = {};
+       __u32 len = sizeof(info);
+       __u32 id = 0;

        obj = bpf_object__open(MAPINMAP_PROG);

@@ -1229,10 +1233,68 @@ static void test_map_in_map(void)

        close(fd);