Re: [PATCH v8 13/13] fstests: test UUID consistency for clones with metadata_uuid

[Anand Suveer Jain <asj@kernel.org>]

On 2/9/26 04:51, Zorro Lang wrote:
> On Sat, Jul 25, 2026 at 03:39:10PM +0800, Anand Jain wrote:
>> Btrfs and xfs uses the metadata_uuid superblock feature to change the
>> on-disk UUID without rewriting every block header. This patch adds a
>> sanity check to ensure UUID consistency when a filesystem with
>> metadata_uuid enabled is cloned.
>>
>> Signed-off-by: Anand Jain <asj@kernel.org>
>> ---
>>  tests/generic/806     | 74 +++++++++++++++++++++++++++++++++++++++++++
>>  tests/generic/806.out |  6 ++++
>>  2 files changed, 80 insertions(+)
>>  create mode 100644 tests/generic/806
>>  create mode 100644 tests/generic/806.out
>>
>> diff --git a/tests/generic/806 b/tests/generic/806
>> new file mode 100644
>> index 000000000000..6d3166491006
>> --- /dev/null
>> +++ b/tests/generic/806
>> @@ -0,0 +1,74 @@
>> +#! /bin/bash
>> +# SPDX-License-Identifier: GPL-2.0
>> +# Copyright (c) 2026 Anand Jain <asj@kernel.org>.  All Rights Reserved.
>> +#
>> +# FS QA Test 806
>> +#
>> +# Verify that the cloned filesystem UUID remains consistent, even when the
>> +# `metadata_uuid` feature is enabled.
>> +#
>> +
>> +. ./common/preamble
>> +. ./common/filter
>> +
>> +_begin_fstest auto quick mount clone
>> +
>> +_require_test
>> +_require_block_device $TEST_DEV
>> +_require_loop
>> +
>> +_cleanup()
>> +{
>> +	cd /
>> +	rm -r -f $tmp.*
>> +	umount $mnt1 $mnt2 2>/dev/null
>> +	_loop_image_destroy "${devs[@]}" 2> /dev/null
>> +}
>> +
>> +filter_pool()
>> +{
>> +	sed -e "s|${devs[0]}|DEV1|g" -e "s|${mnt1}|MNT1|g" \
>> +	    -e "s|${devs[1]}|DEV2|g" -e "s|${mnt2}|MNT2|g" | _filter_spaces
>> +}
>> +


>> +# Create base loop device and its clone, applying the metadata_uuid tuning
>> +# callback to the base filesystem before the copy occurs.
>> +devs=()
>> +_loop_image_create_clone devs _change_metadata_uuid
> 
> Should we have and run a _require_metadata_uuid before changing it?
> As I know, btrfs can do `_require_btrfs_fs_feature metadata_uuid`.
> 

_require_metadata_uuid() is better than doing the same thing within
_change_metadata_uuid(). Now _change_metadata_uuid() calls
_require_metadata_uuid(), as shown below.


_require_metdata_uuid()
{
        case $FSTYP in
        xfs)
                _require_command "$XFS_ADMIN_PROG" "xfs_admin"
                ;;
        btrfs)
                _require_btrfs_fs_feature "metadata_uuid"
                _require_command "$BTRFS_TUNE_PROG" "btrfstune"
                ;;
        *)
                _notrun "Require filesystem with metadata_uuid feature"
                ;;
        esac
}


_change_metadata_uuid()
{
        local dev=$1

        _require_metdata_uuid

        case $FSTYP in
        xfs)
                $XFS_ADMIN_PROG -U generate $dev >> $seqres.full
                ;;
        btrfs)
                $BTRFS_TUNE_PROG -m $dev
                ;;
        esac
}



>> +mkdir -p $TEST_DIR/$seq
>> +mnt1=$TEST_DIR/$seq/mnt1
>> +mnt2=$TEST_DIR/$seq/mnt2
>> +mkdir -p $mnt1
>> +mkdir -p $mnt2
>> +
>> +# Get the uuid from the source device
>> +fsuuid=$(blkid -s UUID -o value ${devs[0]})
>> +
>> +# Mount both clone and baseline
>> +_mount $(_common_dev_mount_options) $(_clone_mount_option) ${devs[0]} $mnt1 || \
>> +						_fail "Failed to mount dev1"
>> +_mount $(_common_dev_mount_options) $(_clone_mount_option) ${devs[1]} $mnt2 || \
>> +						_fail "Failed to mount dev2"
>> +
>> +findmnt -o SOURCE,TARGET,UUID "${devs[0]}" | tail -n +2 | \
>> +				sed -e "s/${fsuuid}/FSUUID/g" | filter_pool
>> +findmnt -o SOURCE,TARGET,UUID "${devs[1]}" | tail -n +2 | \
>> +				sed -e "s/${fsuuid}/FSUUID/g" | filter_pool
>> +
>> +# Cycle mounts and reverse the initialization order to ensure UUID tracking
>> +# doesn't mismatch or flip when metadata_uuid optimization is active.
>> +echo "**** mount cycle ****"
>> +_unmount $mnt1
>> +_unmount $mnt2
>> +_mount $(_common_dev_mount_options) $(_clone_mount_option) ${devs[1]} $mnt2 || \
>> +						_fail "Failed to mount dev2"
>> +_mount $(_common_dev_mount_options) $(_clone_mount_option) ${devs[0]} $mnt1 || \
>> +						_fail "Failed to mount dev1"
>> +
>> +findmnt -o SOURCE,TARGET,UUID "${devs[0]}" | tail -n +2 | \
>> +				sed -e "s/${fsuuid}/FSUUID/g" | filter_pool
>> +findmnt -o SOURCE,TARGET,UUID "${devs[1]}" | tail -n +2 | \
>> +				sed -e "s/${fsuuid}/FSUUID/g" | filter_pool
>> +
>> +status=0
>> +exit
>> diff --git a/tests/generic/806.out b/tests/generic/806.out
>> new file mode 100644
>> index 000000000000..918f422ecddf
>> --- /dev/null
>> +++ b/tests/generic/806.out
>> @@ -0,0 +1,6 @@
>> +QA output created by 806
>> +DEV1 MNT1 FSUUID
>> +DEV2 MNT2 FSUUID
>> +**** mount cycle ****
>> +DEV1 MNT1 FSUUID
>> +DEV2 MNT2 FSUUID
>> -- 
>> 2.43.0
>>