selftests/bpf: Fix overflow tests to reflect iter size increase

bpf iter size increase to PAGE_SIZE << 3 means overflow tests assuming
page size need to be bumped also.
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/1601292670-1616-7-git-send-email-alan.maguire@oracle.com

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

@@ -352,7 +352,7 @@ static void test_overflow(bool test_e2big_overflow, bool ret1)
 	struct bpf_map_info map_info = {};
 	struct bpf_iter_test_kern4 *skel;
 	struct bpf_link *link;
-	__u32 page_size;
+	__u32 iter_size;
 	char *buf;
 
 	skel = bpf_iter_test_kern4__open();
@@ -374,19 +374,19 @@ static void test_overflow(bool test_e2big_overflow, bool ret1)
 		  "map_creation failed: %s\n", strerror(errno)))
 		goto free_map1;
 
-	/* bpf_seq_printf kernel buffer is one page, so one map
+	/* bpf_seq_printf kernel buffer is 8 pages, so one map
 	 * bpf_seq_write will mostly fill it, and the other map
 	 * will partially fill and then trigger overflow and need
 	 * bpf_seq_read restart.
 	 */
-	page_size = sysconf(_SC_PAGE_SIZE);
+	iter_size = sysconf(_SC_PAGE_SIZE) << 3;
 
 	if (test_e2big_overflow) {
-		skel->rodata->print_len = (page_size + 8) / 8;
-		expected_read_len = 2 * (page_size + 8);
+		skel->rodata->print_len = (iter_size + 8) / 8;
+		expected_read_len = 2 * (iter_size + 8);
 	} else if (!ret1) {
-		skel->rodata->print_len = (page_size - 8) / 8;
-		expected_read_len = 2 * (page_size - 8);
+		skel->rodata->print_len = (iter_size - 8) / 8;
+		expected_read_len = 2 * (iter_size - 8);
 	} else {
 		skel->rodata->print_len = 1;
 		expected_read_len = 2 * 8;