Re: [PATCH] generic: test zero-byte writes to new file

["Darrick J. Wong" <djwong@kernel.org>]

On Thu, Feb 13, 2025 at 12:06:24PM -0600, Eric Sandeen wrote:
> A bug was recently fixed in exfat where attempting to do a zero-byte
> write would yield -EFAULT; test for that here.
> 
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
> ---
> 
> diff --git a/tests/generic/761 b/tests/generic/761
> new file mode 100755
> index 00000000..e933eb83
> --- /dev/null
> +++ b/tests/generic/761
> @@ -0,0 +1,28 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2025 Red Hat, Inc.  All Rights Reserved.
> +#
> +# FS QA Test 761
> +#
> +# test zero-byte writes
> +#
> +# exfat had a regression where a zero-byte write to a file would
> +# yield -EfAULT. Should work on all filesystems - write should
> +# succeed and the zero-byte file should be created.
> +#
> +. ./common/preamble
> +_begin_fstest auto quick
> +
> +[ "$FSTYP" = "exfat" ] && _fixed_by_kernel_commit dda0407a2026 \
> +	"exfat: short-circuit zero-byte writes in exfat_file_write_iter"
> +
> +# Modify as appropriate.
> +_require_test
> +
> +rm -f $TEST_DIR/testfile.$seq
> +$XFS_IO_PROG -f -c "pwrite 0 0" $TEST_DIR/testfile.$seq
> +test -f $TEST_DIR/testfile.$seq || _fail "file not created"

When does the file not get created?

--D

> +
> +# success, all done
> +status=0
> +exit
> diff --git a/tests/generic/761.out b/tests/generic/761.out
> new file mode 100644
> index 00000000..72ebba4c
> --- /dev/null
> +++ b/tests/generic/761.out
> @@ -0,0 +1,2 @@
> +QA output created by 761
> +Silence is golden
> 
>