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

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

On Fri, Feb 21, 2025 at 10:44:09AM +0530, Nirjhar Roy (IBM) wrote:
> On Thu, 2025-02-13 at 12:06 -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"
> Minor: Maybe just remove the test file that is created above (since we
> are using the TEST_DIR)and not leave any test artifacts? Or, maybe use
> the scratch device? 

Agreed, the _cleanup should remove the testfile.

Using the scratch device (== additional runtime for mkfs) is overkill
since this test creates a single file but writes nothing to it.

--D

> --NR
> > +
> > +# 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
> > 
> 
>