selftests/bpf: Add tests for automatic map unpinning on load failure

This add tests for the different variations of automatic map unpinning on
load failure.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/157333184838.88376.8243704248624814775.stgit@toke.dk

tools/testing/selftests/bpf/prog_tests/pinning.c

@@ -163,12 +163,15 @@ void test_pinning(void)
 		goto out;
 	}
 
-	/* swap pin paths of the two maps */
+	/* set pin paths so that nopinmap2 will attempt to reuse the map at
+	 * pinpath (which will fail), but not before pinmap has already been
+	 * reused
+	 */
 	bpf_object__for_each_map(map, obj) {
 		if (!strcmp(bpf_map__name(map), "nopinmap"))
+			err = bpf_map__set_pin_path(map, nopinpath2);
+		else if (!strcmp(bpf_map__name(map), "nopinmap2"))
 			err = bpf_map__set_pin_path(map, pinpath);
-		else if (!strcmp(bpf_map__name(map), "pinmap"))
-			err = bpf_map__set_pin_path(map, NULL);
 		else
 			continue;
 
@@ -181,6 +184,17 @@ void test_pinning(void)
 	if (CHECK(err != -EINVAL, "param mismatch load", "err %d errno %d\n", err, errno))
 		goto out;
 
+	/* nopinmap2 should have been pinned and cleaned up again */
+	err = stat(nopinpath2, &statbuf);
+	if (CHECK(!err || errno != ENOENT, "stat nopinpath2",
+		  "err %d errno %d\n", err, errno))
+		goto out;
+
+	/* pinmap should still be there */
+	err = stat(pinpath, &statbuf);
+	if (CHECK(err, "stat pinpath", "err %d errno %d\n", err, errno))
+		goto out;
+
 	bpf_object__close(obj);
 
 	/* test auto-pinning at custom path with open opt */

tools/testing/selftests/bpf/progs/test_pinning.c

@@ -21,7 +21,7 @@ struct {
 } nopinmap SEC(".maps");
 
 struct {
-	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__uint(type, BPF_MAP_TYPE_HASH);
 	__uint(max_entries, 1);
 	__type(key, __u32);
 	__type(value, __u64);