Re: [PATCH 4/9] fstests: add test for inotify isolation on cloned devices

[Amir Goldstein <amir73il@gmail.com>]

On Thu, Feb 26, 2026 at 10:41:45PM +0800, Anand Jain wrote:
> Add a new test, to verify that the kernel correctly differentiates between
> two block devices sharing the same FSID/UUID.
> 
> Signed-off-by: Anand Jain <asj@kernel.org>
> ---
>  common/config         |  1 +
>  tests/generic/790     | 78 +++++++++++++++++++++++++++++++++++++++++++
>  tests/generic/790.out |  7 ++++
>  3 files changed, 86 insertions(+)
>  create mode 100644 tests/generic/790
>  create mode 100644 tests/generic/790.out
> 
> diff --git a/common/config b/common/config
> index 1420e35ddfee..c08f828575a2 100644
> --- a/common/config
> +++ b/common/config
> @@ -228,6 +228,7 @@ export BTRFS_MAP_LOGICAL_PROG=$(type -P btrfs-map-logical)
>  export PARTED_PROG="$(type -P parted)"
>  export XFS_PROPERTY_PROG="$(type -P xfs_property)"
>  export FSCRYPTCTL_PROG="$(type -P fscryptctl)"
> +export INOTIFYWAIT_PROG="$(type -P inotifywait)"
>  
>  # udev wait functions.
>  #
> diff --git a/tests/generic/790 b/tests/generic/790
> new file mode 100644
> index 000000000000..3809fced622d
> --- /dev/null
> +++ b/tests/generic/790
> @@ -0,0 +1,78 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2026 Anand Jain <asj@kernel.org>.  All Rights Reserved.
> +#
> +# FS QA Test 790
> +#
> +# Verify if the kernel or userspace becomes confused when two block devices
> +# share the same fid/fsid/uuid. Create inotify on both original and cloned
> +# filesystem. Monitor the notification in the respective logs.
> +
> +. ./common/preamble
> +
> +_begin_fstest auto quick mount clone
> +
> +_require_test
> +_require_scratch_dev_pool 2
> +_require_command "$INOTIFYWAIT_PROG" inotifywait
> +
> +_cleanup()
> +{
> +	cd /
> +	rm -r -f $tmp.*
> +	umount $mnt1 $mnt2 2>/dev/null
> +	_scratch_dev_pool_put
> +}
> +
> +_scratch_dev_pool_get 2
> +_scratch_mkfs_sized_clone >$seqres.full 2>&1
> +devs=($SCRATCH_DEV_POOL)
> +mnt2=$TEST_DIR/mnt2
> +mkdir -p $mnt2
> +
> +_scratch_mount $(_clone_mount_option)
> +_mount $(_common_dev_mount_options) $(_clone_mount_option) ${devs[1]} $mnt2 || \
> +						_fail "Failed to mount dev2"
> +
> +log1=$tmp.inotify1
> +log2=$tmp.inotify2
> +
> +echo "Setup inotify watchers on both SCRATCH_MNT and mnt2"
> +$INOTIFYWAIT_PROG -m -e create --format '%f' $SCRATCH_MNT > $log1 2>&1 &
> +pid1=$!
> +$INOTIFYWAIT_PROG -m -e create --format '%f' $mnt2 > $log2 2>&1 &
> +pid2=$!
> +sleep 2
> +
> +echo "Trigger file creation on SCRATCH_MNT"
> +touch $SCRATCH_MNT/file_on_scratch_mnt
> +sync
> +sleep 1
> +
> +echo "Trigger file creation on mnt2"
> +touch $mnt2/file_on_mnt2
> +sync
> +sleep 1
> +
> +echo "Verify inotify isolation"
> +kill $pid1 $pid2
> +wait $pid1 $pid2 2>/dev/null

I think you also need to take care of killing the bg process
in _cleanup() so that the test could be cleanly aborted.

Thanks,
Amir.

> +
> +if grep -q "file_on_scratch_mnt" $log1 && ! grep -q "file_on_mnt2" $log1; then
> +	echo "SUCCESS: SCRATCH_MNT events isolated."
> +else
> +	echo "FAIL: SCRATCH_MNT inotify confusion!"
> +	[ ! -s $log1 ] && echo "  - SCRATCH_MNT received no events."
> +	grep -q "file_on_mnt2" $log1 && echo "  - SCRATCH_MNT received event from mnt2."
> +fi
> +
> +if grep -q "file_on_mnt2" $log2 && ! grep -q "file_on_scratch_mnt" $log2; then
> +	echo "SUCCESS: mnt2 events isolated."
> +else
> +	echo "FAIL: mnt2 inotify confusion!"
> +	[ ! -s $log2 ] && echo "  - mnt2 received no events."
> +	grep -q "file_on_scratch_mnt" $log2 && echo "  - mnt2 received event from SCRATCH_MNT."
> +fi
> +
> +status=0
> +exit
> diff --git a/tests/generic/790.out b/tests/generic/790.out
> new file mode 100644
> index 000000000000..3c92c34ffbda
> --- /dev/null
> +++ b/tests/generic/790.out
> @@ -0,0 +1,7 @@
> +QA output created by 790
> +Setup inotify watchers on both SCRATCH_MNT and mnt2
> +Trigger file creation on SCRATCH_MNT
> +Trigger file creation on mnt2
> +Verify inotify isolation
> +SUCCESS: SCRATCH_MNT events isolated.
> +SUCCESS: mnt2 events isolated.
> -- 
> 2.43.0
>