Re: [PATCH 08/13] xfs/2303: test that data checksums detect data misplacement

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

On Thu, Sep 24, 2026 at 12:07:49PM +0200, Christoph Hellwig wrote:
> Test that data checksums detect data corruption due to misplacement
> by changing the backing files for two zones using the zloop driver.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  tests/xfs/2303     | 88 ++++++++++++++++++++++++++++++++++++++++++++++
>  tests/xfs/2303.out |  5 +++
>  2 files changed, 93 insertions(+)
>  create mode 100755 tests/xfs/2303
>  create mode 100644 tests/xfs/2303.out
> 
> diff --git a/tests/xfs/2303 b/tests/xfs/2303
> new file mode 100755
> index 000000000000..7f53fdf94bff
> --- /dev/null
> +++ b/tests/xfs/2303
> @@ -0,0 +1,88 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2026 Christoph Hellwig
> +#
> +# FS QA Test No. 2303
> +#
> +# Test that data checksums detect data corruption due to misplacement
> +# by changing the backing files for two zones using the zloop driver.
> +#
> +. ./common/preamble
> +. ./common/filter
> +. ./common/renameat2
> +. ./common/zoned
> +
> +_begin_fstest auto zone quick datacsum
> +
> +_cleanup()
> +{
> +	[ -n "$mnt" ] && _unmount $mnt 2>/dev/null
> +	[ -n "$loop_dev" ] && _destroy_loop_device $loop_dev
> +	_destroy_zloop $zloop_dev
> +	cd /
> +	rm -rf $loopfile $zloopdir $mnt
> +}
> +
> +_require_test
> +_require_renameat2 "exchange"
> +_require_loop
> +_require_zloop
> +# hack to only run for block based file systems
> +_require_block_device $SCRATCH_DEV
> +
> +loopfile="$TEST_DIR/loopfile"
> +zloopdir="$TEST_DIR/zloop"
> +mnt="$TEST_DIR/mnt"
> +
> +rm -rf $loopfile $zloopdir $mnt
> +mkdir -p $mnt
> +truncate -s 1g $loopfile
> +
> +loop_dev=$(_create_loop_device $loopfile)
> +zloop_dev=$(_create_zloop $zloopdir 256 0)
> +zloop_id=$(echo $zloop_dev | grep -oE '[0-9]+$')
> +
> +_try_mkfs_dev $loop_dev -r rtdev=$zloop_dev,csum=crc32c \
> +	>> $seqres.full 2>&1 || \
> +	_notrun "cannot mkfs filesystem with data checksums"
> +_mount $loop_dev -o rtdev=$zloop_dev $mnt
> +
> +dd if=/dev/urandom of=$mnt/file1 bs=4k count=1 conv=fsync >/dev/null 2>&1
> +dd if=/dev/zero of=$mnt/file2 bs=4k count=1 conv=fsync >/dev/null 2>&1
> +
> +xfs_bmap -v $mnt/file1 >> $seqres.full 2>&1
> +xfs_bmap -v $mnt/file2 >> $seqres.full 2>&1
> +
> +rg1=`xfs_bmap -v $mnt/file1 | head -n 3 | _filter_bmap_gno`
> +rg2=`xfs_bmap -v $mnt/file2 | head -n 3 | _filter_bmap_gno`
> +if [ "$rg1" == "$rg2" ]; then
> +	_fail "both files placed in same RG: $rg1 $rg2"
> +fi
> +
> +zloop_filename1=$(printf "seq-%06u\n" $rg1)
> +backing_file1="$zloopdir/$zloop_id/$zloop_filename1"
> +zloop_filename2=$(printf "seq-%06u\n" $rg2)
> +backing_file2="$zloopdir/$zloop_id/$zloop_filename2"
> +
> +_unmount $mnt 2>/dev/null
> +_destroy_zloop $zloop_dev
> +
> +# intentionally corrupt data by swapping the two zone files
> +ls -i $backing_file1 $backing_file2 >> $seqres.full
> +echo "swapping file $backing_file1 and $backing_file2" >> $seqres.full
> +$here/src/renameat2 -x $backing_file1 $backing_file2
> +ls -i $backing_file1 $backing_file2 >> $seqres.full

Heh, this is an amusing way to induce a data checksum verification
failure -- switching the zone backing files. :)  Given that one of the
previous tests directly writes to the rt dev I think this one is less
important, but I guess that's one way to simulate an evil-maid device.

(Same nitpicks as the previous test)

--D

> +
> +zloop_dev=$(_create_zloop $zloopdir 256 0)
> +zloop_id=$(echo $zloop_dev | grep -oE '[0-9]+$')
> +_mount $loop_dev -o rtdev=$zloop_dev $mnt
> +
> +# should return an error on buffered read
> +echo "Reading file1 using cat - should fail"
> +cat $mnt/file1 > /dev/null | _filter_test_dir
> +
> +# same with direct I/O
> +echo "Reading file2 using O_DIRECT - should fail"
> +xfs_io -d $mnt/file2 -c 'pread 0 200M' | _filter_test_dir
> +
> +_exit 0
> diff --git a/tests/xfs/2303.out b/tests/xfs/2303.out
> new file mode 100644
> index 000000000000..fca2c4830e3c
> --- /dev/null
> +++ b/tests/xfs/2303.out
> @@ -0,0 +1,5 @@
> +QA output created by 2303
> +Reading file1 using cat - should fail
> +cat: /mnt/test/mnt/file1: Input/output error
> +Reading file2 using O_DIRECT - should fail
> +pread: Input/output error
> -- 
> 2.53.0
> 
>