Re: [PATCH] selftests: arg_parsing: Ensure data is flushed to disk before reading.

[Jiri Olsa <olsajiri@gmail.com>]

On Tue, Oct 14, 2025 at 04:03:23PM +0800, Xing Guo wrote:
> Recently, I noticed a selftest failure in my local environment. The
> test_parse_test_list_file writes some data to
> /tmp/bpf_arg_parsing_test.XXXXXX and parse_test_list_file() will read
> the data back.  However, after writing data to that file, we forget to
> call fsync() and it's causing testing failure in my laptop.  This patch
> helps fix it by adding the missing fsync() call.
> 
> Signed-off-by: Xing Guo <higuoxing@gmail.com>
> ---
>  tools/testing/selftests/bpf/prog_tests/arg_parsing.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/arg_parsing.c b/tools/testing/selftests/bpf/prog_tests/arg_parsing.c
> index bb143de68875..4f071943ffb0 100644
> --- a/tools/testing/selftests/bpf/prog_tests/arg_parsing.c
> +++ b/tools/testing/selftests/bpf/prog_tests/arg_parsing.c
> @@ -140,6 +140,7 @@ static void test_parse_test_list_file(void)
>  	fprintf(fp, "testA/subtest2\n");
>  	fprintf(fp, "testC_no_eof_newline");
>  	fflush(fp);
> +	fsync(fd);


could we just close the fp stream instead flushing it twice?

maybe something like below, but not sure ferror will work
after the fclose call

jirka


---
diff --git a/tools/testing/selftests/bpf/prog_tests/arg_parsing.c b/tools/testing/selftests/bpf/prog_tests/arg_parsing.c
index bb143de68875..5a4c1bca2a1e 100644
--- a/tools/testing/selftests/bpf/prog_tests/arg_parsing.c
+++ b/tools/testing/selftests/bpf/prog_tests/arg_parsing.c
@@ -139,10 +139,10 @@ static void test_parse_test_list_file(void)
 	fprintf(fp, "testA/subtest # subtest duplicate\n");
 	fprintf(fp, "testA/subtest2\n");
 	fprintf(fp, "testC_no_eof_newline");
-	fflush(fp);
+	fclose(fp);
 
 	if (!ASSERT_OK(ferror(fp), "prepare tmp"))
-		goto out_fclose;
+		goto out_remove;
 
 	init_test_filter_set(&set);
 
@@ -160,8 +160,6 @@ static void test_parse_test_list_file(void)
 
 	free_test_filter_set(&set);
 
-out_fclose:
-	fclose(fp);
 out_remove:
 	remove(tmpfile);
 }