Re: [PATCH] generic: test i_blocks for truncated large files

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

On Tue, Sep 06, 2022 at 05:53:20PM +0200, Pavel Reichl wrote:
> This is a regression test for an incorrect computation of i_blocks for
> truncated files larger than 4 GiB. Bug was filed for exFAT.
> 
> Test is based on reproducer provied by Christophe Vu-Brugier as part
> of kernel patch-fix submission.
> 
> Signed-off-by: Pavel Reichl <preichl@redhat.com>
> ---
>  tests/generic/698     | 47 +++++++++++++++++++++++++++++++++++++++++++
>  tests/generic/698.out |  2 ++
>  2 files changed, 49 insertions(+)
>  create mode 100755 tests/generic/698
>  create mode 100644 tests/generic/698.out
> 
> diff --git a/tests/generic/698 b/tests/generic/698
> new file mode 100755
> index 00000000..217641e6
> --- /dev/null
> +++ b/tests/generic/698
> @@ -0,0 +1,47 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2022  Red Hat Inc. All Rights Reserved.
> +#
> +# FS QA Test 698
> +#
> +# Verify that i_blocks for truncated files larger than 4 GiB have correct
> +# values.
> +#
> +# This test verifies the problem fixed in kernel with commit
> +# 92fba084b79e exfat: fix i_blocks for files truncated over 4 GiB
> +#
> +. ./common/preamble
> +_begin_fstest auto
> +
> +# Override the default cleanup function.
> +_cleanup()
> +{
> +	cd /
> +	rm -r -f $tmp.* $junk_dir
> +}
> +
> +_supported_fs generic
> +_require_test
> +_require_fs_space $TEST_DIR $((5 * 1024 * 1024)) #kB
> +
> +echo "Silence is golden"
> +
> +junk_dir=$TEST_DIR/$seq
> +junk_file=$junk_dir/junk
> +mkdir -p $junk_dir
> +
> +$XFS_IO_PROG -f -c "pwrite -W 0 5G" $junk_file > /dev/null
> +
> +
> +truncate -s $((4 * 1024 * 1024 * 1024)) $junk_file
> +
> +iblocks_after_truncate=`stat -c '%b' $junk_file`
> +iblocks_expected=$((4 * 1024 * 1024 * 2))

What happens if the filesystem allocates a substantial number of blocks
to store block mappings (e.g. ext2)?  Those are accounted to i_blocks.

> +
> +if [ "$iblocks_expected" != "$iblocks_after_truncate" ]; then
> +	echo "Number of blocks needs to be same: $iblocks_expected, $iblocks_after_truncate"

_within_range?

--D

> +fi
> +
> +status=0
> +
> +exit
> diff --git a/tests/generic/698.out b/tests/generic/698.out
> new file mode 100644
> index 00000000..222db0de
> --- /dev/null
> +++ b/tests/generic/698.out
> @@ -0,0 +1,2 @@
> +QA output created by 698
> +Silence is golden
> -- 
> 2.37.3
>