selftests/bpf: Remove the liveness test for inner map

Even before the introduction of deferred-map-put for inner map, the
liveness test for inner map is not correct, because inner_map1 and
inner_map2 are released directly in a kworker and there is no need for
invoking kern_sync_rcu().

After deferring the invocation of bpf_map_put() for inner map, the time
when the inner map is released is more complicated: each overwrite of
the inner map will delay the release of the inner map after both one RCU
grace period and one tasks trace RCU grace period. To avoid such
complexity in selftest, just remove the liveness test for inner map.

Signed-off-by: Hou Tao <[email protected]>

Author: Hou Tao

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

@@ -25,7 +25,7 @@ static void test_lookup_update(void)
 	int map1_fd, map2_fd, map3_fd, map4_fd, map5_fd, map1_id, map2_id;
 	int outer_arr_fd, outer_hash_fd, outer_arr_dyn_fd;
 	struct test_btf_map_in_map *skel;
-	int err, key = 0, val, i, fd;
+	int err, key = 0, val, i;
 
 	skel = test_btf_map_in_map__open_and_load();
 	if (CHECK(!skel, "skel_open", "failed to open&load skeleton\n"))
@@ -102,30 +102,6 @@ static void test_lookup_update(void)
 	CHECK(map1_id == 0, "map1_id", "failed to get ID 1\n");
 	CHECK(map2_id == 0, "map2_id", "failed to get ID 2\n");
 
-	test_btf_map_in_map__destroy(skel);
-	skel = NULL;
-
-	/* we need to either wait for or force synchronize_rcu(), before
-	 * checking for "still exists" condition, otherwise map could still be
-	 * resolvable by ID, causing false positives.
-	 *
-	 * Older kernels (5.8 and earlier) freed map only after two
-	 * synchronize_rcu()s, so trigger two, to be entirely sure.
-	 */
-	CHECK(kern_sync_rcu(), "sync_rcu", "failed\n");
-	CHECK(kern_sync_rcu(), "sync_rcu", "failed\n");
-
-	fd = bpf_map_get_fd_by_id(map1_id);
-	if (CHECK(fd >= 0, "map1_leak", "inner_map1 leaked!\n")) {
-		close(fd);
-		goto cleanup;
-	}
-	fd = bpf_map_get_fd_by_id(map2_id);
-	if (CHECK(fd >= 0, "map2_leak", "inner_map2 leaked!\n")) {
-		close(fd);
-		goto cleanup;
-	}
-
 cleanup:
 	test_btf_map_in_map__destroy(skel);
 }