Re: [PATCH 2/2] selftests/nolibc: Add a very basic test for fallocate()

["Thomas Weißschuh" <linux@weissschuh.net>]

On 2026-04-15 23:32:25+0900, Daniel Palmer wrote:
> Create a tmp file, fallocate() to make it a bit bigger, check the
> size is what was expected.
> 
> Signed-off-by: Daniel Palmer <daniel@thingy.jp>
> ---
>  tools/testing/selftests/nolibc/nolibc-test.c | 33 ++++++++++++++++++++
>  1 file changed, 33 insertions(+)
> 
> diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
> index d3c4facb54c0..066f436561e7 100644
> --- a/tools/testing/selftests/nolibc/nolibc-test.c
> +++ b/tools/testing/selftests/nolibc/nolibc-test.c
> @@ -896,6 +896,38 @@ int test_getpagesize(void)
>  	return !c;
>  }
>  
> +int test_fallocate(void)
> +{
> +	struct stat st;
> +	int fd, r;
> +
> +	/* Create a new tmp file */
> +	fd = open("/tmp", O_TMPFILE | O_RDWR, 0644);
> +	if (fd == -1)
> +		return -1;
> +
> +	/* Expand it to 42 bytes */
> +	r = fallocate(fd, 0, 0, 42);
> +	if (r)
> +		goto close_tmpfile;
> +
> +	/* Get the new stat */
> +	r = fstat(fd, &st);
> +	if (r)
> +		goto close_tmpfile;
> +
> +	/* It should be 42 bytes long */
> +	if (st.st_size != 42) {
> +		r = -1;
> +		goto close_tmpfile;
> +	}

This should also check that full 64-bit values are passed through.

> +
> +close_tmpfile:
> +	close(fd);
> +
> +	return r;
> +}

(...)