selftests: bpf: test batch lookup on array of maps with holes

JIRA: https://issues.redhat.com/browse/RHEL-85486

commit d66b773
Author: Yan Zhai <yan@cloudflare.com>
Date:   Sun Feb 9 23:22:39 2025 -0800

    selftests: bpf: test batch lookup on array of maps with holes

    Iterating through array of maps may encounter non existing keys. The
    batch operation should not fail on when this happens.

    Signed-off-by: Yan Zhai <yan@cloudflare.com>
    Acked-by: Hou Tao <houtao1@huawei.com>
    Link: https://lore.kernel.org/r/9007237b9606dc2ee44465a4447fe46e13f3bea6.1739171594.git.yan@cloudflare.com
    Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>

Author: jeromemarchand

tools/testing/selftests/bpf/map_tests/map_in_map_batch_ops.c

@@ -120,11 +120,12 @@ static void validate_fetch_results(int outer_map_fd,
 
 static void fetch_and_validate(int outer_map_fd,
 			       struct bpf_map_batch_opts *opts,
-			       __u32 batch_size, bool delete_entries)
+			       __u32 batch_size, bool delete_entries,
+			       bool has_holes)
 {
-	__u32 *fetched_keys, *fetched_values, total_fetched = 0;
-	__u32 batch_key = 0, fetch_count, step_size;
-	int err, max_entries = OUTER_MAP_ENTRIES;
+	int err, max_entries = OUTER_MAP_ENTRIES - !!has_holes;
+	__u32 *fetched_keys, *fetched_values, total_fetched = 0, i;
+	__u32 batch_key = 0, fetch_count, step_size = batch_size;
 	__u32 value_size = sizeof(__u32);
 
 	/* Total entries needs to be fetched */
@@ -134,9 +135,8 @@ static void fetch_and_validate(int outer_map_fd,
 	      "Memory allocation failed for fetched_keys or fetched_values",
 	      "error=%s\n", strerror(errno));
 
-	for (step_size = batch_size;
-	     step_size <= max_entries;
-	     step_size += batch_size) {
+	/* hash map may not always return full batch */
+	for (i = 0; i < OUTER_MAP_ENTRIES; i++) {
 		fetch_count = step_size;
 		err = delete_entries
 		      ? bpf_map_lookup_and_delete_batch(outer_map_fd,
@@ -155,6 +155,7 @@ static void fetch_and_validate(int outer_map_fd,
 		if (err && errno == ENOSPC) {
 			/* Fetch again with higher batch size */
 			total_fetched = 0;
+			step_size += batch_size;
 			continue;
 		}
 
@@ -184,18 +185,19 @@ static void fetch_and_validate(int outer_map_fd,
 }
 
 static void _map_in_map_batch_ops(enum bpf_map_type outer_map_type,
-				  enum bpf_map_type inner_map_type)
+				  enum bpf_map_type inner_map_type,
+				  bool has_holes)
 {
+	__u32 max_entries = OUTER_MAP_ENTRIES - !!has_holes;
 	__u32 *outer_map_keys, *inner_map_fds;
-	__u32 max_entries = OUTER_MAP_ENTRIES;
 	LIBBPF_OPTS(bpf_map_batch_opts, opts);
 	__u32 value_size = sizeof(__u32);
 	int batch_size[2] = {5, 10};
 	__u32 map_index, op_index;
 	int outer_map_fd, ret;
 
-	outer_map_keys = calloc(max_entries, value_size);
-	inner_map_fds = calloc(max_entries, value_size);
+	outer_map_keys = calloc(OUTER_MAP_ENTRIES, value_size);
+	inner_map_fds = calloc(OUTER_MAP_ENTRIES, value_size);
 	CHECK((!outer_map_keys || !inner_map_fds),
 	      "Memory allocation failed for outer_map_keys or inner_map_fds",
 	      "error=%s\n", strerror(errno));
@@ -209,6 +211,24 @@ static void _map_in_map_batch_ops(enum bpf_map_type outer_map_type,
 			((outer_map_type == BPF_MAP_TYPE_ARRAY_OF_MAPS)
 			 ? 9 : 1000) - map_index;
 
+	/* This condition is only meaningful for array of maps.
+	 *
+	 * max_entries == OUTER_MAP_ENTRIES - 1 if it is true. Say
+	 * max_entries is short for n, then outer_map_keys looks like:
+	 *
+	 *   [n, n-1, ... 2, 1]
+	 *
+	 * We change it to
+	 *
+	 *   [n, n-1, ... 2, 0]
+	 *
+	 * So it will leave key 1 as a hole. It will serve to test the
+	 * correctness when batch on an array: a "non-exist" key might be
+	 * actually allocated and returned from key iteration.
+	 */
+	if (has_holes)
+		outer_map_keys[max_entries - 1]--;
+
 	/* batch operation - map_update */
 	ret = bpf_map_update_batch(outer_map_fd, outer_map_keys,
 				   inner_map_fds, &max_entries, &opts);
@@ -219,15 +239,17 @@ static void _map_in_map_batch_ops(enum bpf_map_type outer_map_type,
 	/* batch operation - map_lookup */
 	for (op_index = 0; op_index < 2; ++op_index)
 		fetch_and_validate(outer_map_fd, &opts,
-				   batch_size[op_index], false);
+				   batch_size[op_index], false,
+				   has_holes);
 
 	/* batch operation - map_lookup_delete */
 	if (outer_map_type == BPF_MAP_TYPE_HASH_OF_MAPS)
 		fetch_and_validate(outer_map_fd, &opts,
-				   max_entries, true /*delete*/);
+				   max_entries, true /*delete*/,
+				   has_holes);
 
 	/* close all map fds */
-	for (map_index = 0; map_index < max_entries; map_index++)
+	for (map_index = 0; map_index < OUTER_MAP_ENTRIES; map_index++)
 		close(inner_map_fds[map_index]);
 	close(outer_map_fd);
 
@@ -237,16 +259,20 @@ static void _map_in_map_batch_ops(enum bpf_map_type outer_map_type,
 
 void test_map_in_map_batch_ops_array(void)
 {
-	_map_in_map_batch_ops(BPF_MAP_TYPE_ARRAY_OF_MAPS, BPF_MAP_TYPE_ARRAY);
+	_map_in_map_batch_ops(BPF_MAP_TYPE_ARRAY_OF_MAPS, BPF_MAP_TYPE_ARRAY, false);
 	printf("%s:PASS with inner ARRAY map\n", __func__);
-	_map_in_map_batch_ops(BPF_MAP_TYPE_ARRAY_OF_MAPS, BPF_MAP_TYPE_HASH);
+	_map_in_map_batch_ops(BPF_MAP_TYPE_ARRAY_OF_MAPS, BPF_MAP_TYPE_HASH, false);
 	printf("%s:PASS with inner HASH map\n", __func__);
+	_map_in_map_batch_ops(BPF_MAP_TYPE_ARRAY_OF_MAPS, BPF_MAP_TYPE_ARRAY, true);
+	printf("%s:PASS with inner ARRAY map with holes\n", __func__);
+	_map_in_map_batch_ops(BPF_MAP_TYPE_ARRAY_OF_MAPS, BPF_MAP_TYPE_HASH, true);
+	printf("%s:PASS with inner HASH map with holes\n", __func__);
 }
 
 void test_map_in_map_batch_ops_hash(void)
 {
-	_map_in_map_batch_ops(BPF_MAP_TYPE_HASH_OF_MAPS, BPF_MAP_TYPE_ARRAY);
+	_map_in_map_batch_ops(BPF_MAP_TYPE_HASH_OF_MAPS, BPF_MAP_TYPE_ARRAY, false);
 	printf("%s:PASS with inner ARRAY map\n", __func__);
-	_map_in_map_batch_ops(BPF_MAP_TYPE_HASH_OF_MAPS, BPF_MAP_TYPE_HASH);
+	_map_in_map_batch_ops(BPF_MAP_TYPE_HASH_OF_MAPS, BPF_MAP_TYPE_HASH, false);
 	printf("%s:PASS with inner HASH map\n", __func__);
 }