[PATCH v7 0/11] fstests: add test coverage for cloned filesystem ids

[PATCH v7 0/11] fstests: add test coverage for cloned filesystem ids

[Anand Jain]

v7:
. 803, 806: Trimmed down the UUID checks to only what is required, mountinfo
   and libblkid.
. 802: Dropped the unnecessary echo statements previously used for logical
   flow in the golden output. On second thought, it looks fine without them.
. Swapped _fixed_by_kernel_commit for _fixed_by_fs_commit.
. _clone_mount_option(): Now echoes directly from the case block itself.
. _require_unique_f_fsid(): add the link to the ref. discussions.

v6:
  https://lore.kernel.org/fstests/cover.1779939330.git.asj@kernel.org

v5:
  https://lore.kernel.org/fstests/cover.1779367627.git.asj@kernel.org

v4:
  https://lore.kernel.org/fstests/cover.1777357320.git.asj@kernel.org

v3:
  https://lore.kernel.org/fstests/cover.1777281778.git.asj@kernel.org

v2:
  https://lore.kernel.org/fstests/cover.1774090817.git.asj@kernel.org

v1:
  https://lore.kernel.org/fstests/cover.1772095513.git.asj@kernel.org

This series adds fstests infrastructure and test cases to verify correct
filesystem identity when a filesystem is cloned (block-level copy).
Test covers inotify, fanotify, f_fsid, libblkid, IMA, exportfs file handles
and libblkid tools verify with metadata_uuid.
  New helpers:
   _loop_image_create_clone() and _loop_image_destroy() to help create fs and clone
   _clone_mount_option() helper to apply per-filesystem clone mount options
   _change_metadata_uuid() changes the UUID before the clone

  New tests:
  - fanotify events are isolated between cloned filesystems
  - f_fsid is unique across cloned filesystem instances
  - libblkid correctly resolves duplicate UUIDs to distinct devices
    with and without metadata_uuid
  - IMA distinct identity for each cloned filesystem
  - exportfs file handles resolve correctly on cloned filesystems

Kernel Patches:
  Requires Btrfs kernel patches for all tests to pass.
   [1] https://lore.kernel.org/linux-btrfs/cover.1777281686.git.asj@kernel.org

Anand Jain (11):
  fstests: add _loop_image_create_clone() helper
  fstests: add _clone_mount_option() helper
  fstests: add FSNOTIFYWAIT_PROG
  fstests: add _require_unique_f_fsid() helper
  fstests: verify fanotify isolation on cloned filesystems
  fstests: verify f_fsid for cloned filesystems
  fstests: verify libblkid resolution of duplicate UUIDs
  fstests: verify IMA isolation on cloned filesystems
  fstests: verify exportfs file handles on cloned filesystems
  fstests: add _change_metadata_uuid helper
  fstests: test UUID consistency for clones with metadata_uuid

 common/config         |   1 +
 common/rc             | 120 +++++++++++++++++++++++++++++++++++++
 tests/generic/801     | 135 ++++++++++++++++++++++++++++++++++++++++++
 tests/generic/801.out |   7 +++
 tests/generic/802     |  64 ++++++++++++++++++++
 tests/generic/802.out |   4 ++
 tests/generic/803     |  72 ++++++++++++++++++++++
 tests/generic/803.out |   6 ++
 tests/generic/804     | 108 +++++++++++++++++++++++++++++++++
 tests/generic/804.out |  10 ++++
 tests/generic/805     |  80 +++++++++++++++++++++++++
 tests/generic/805.out |   2 +
 tests/generic/806     |  74 +++++++++++++++++++++++
 tests/generic/806.out |   6 ++
 14 files changed, 689 insertions(+)
 create mode 100644 tests/generic/801
 create mode 100644 tests/generic/801.out
 create mode 100644 tests/generic/802
 create mode 100644 tests/generic/802.out
 create mode 100644 tests/generic/803
 create mode 100644 tests/generic/803.out
 create mode 100644 tests/generic/804
 create mode 100644 tests/generic/804.out
 create mode 100644 tests/generic/805
 create mode 100644 tests/generic/805.out
 create mode 100644 tests/generic/806
 create mode 100644 tests/generic/806.out

-- 
2.43.0

[PATCH v7 01/11] fstests: add _loop_image_create_clone() helper

[Anand Jain]

Introduce _loop_image_create_clone() and _loop_image_destroy() to mkfs an
image file and clone it to another image file, and attach a loop device to
them. And its destroy part.

Signed-off-by: Anand Jain <asj@kernel.org>
---
 common/rc | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)

diff --git a/common/rc b/common/rc
index 79189e7e6e94..d7e3e0bdfb1e 100644
--- a/common/rc
+++ b/common/rc
@@ -1520,6 +1520,69 @@ _scratch_resvblks()
 	esac
 }
 
+# Create a small loop image, run an optional tuning function ($2) on it,
+# clone it, and attach both to loop devices, returned in ($1).
+# Args:
+#   $1: Nameref to return the array of allocated loop devices [base, clone].
+#   $2: Optional callback function to tune the base filesystem before cloning.
+_loop_image_create_clone()
+{
+	local -n _ret=$1
+	local pre_clone_tune_func="$2"
+	local img_file=$TEST_DIR/${seq}.img
+	local img_file_clone=$TEST_DIR/${seq}_clone.img
+	local size=$(_small_fs_size_mb 128) # Smallest possible
+	local loop_devs
+
+	# Since we copy the block device image, we keep its size small.
+	_require_fs_space $TEST_DIR $((size * 1024))
+
+	_create_file_sized $((size * 1024 * 1024)) $img_file ||
+				_fail "Failed: Create $img_file $size"
+
+	loop_devs=$(_create_loop_device $img_file)
+	_ret=($loop_devs)
+
+	case $FSTYP in
+	xfs)
+		_mkfs_dev "-s size=4096" ${loop_devs[0]}
+		;;
+	btrfs)
+		_mkfs_dev ${loop_devs[0]}
+		;;
+	*)
+		_mkfs_dev ${loop_devs[0]}
+		;;
+	esac
+
+	# Only execute if the function argument is not empty
+	if [ -n "$pre_clone_tune_func" ]; then
+		$pre_clone_tune_func ${loop_devs[0]}
+	fi
+
+	sync ${loop_devs[0]}
+	cp $img_file $img_file_clone
+
+	loop_devs="$loop_devs $(_create_loop_device $img_file_clone)"
+
+	_ret=($loop_devs)
+}
+
+# Teardown loop devices and delete their underlying backing image files.
+# Accepts a list of loop device paths (e.g., /dev/loop0 /dev/loop1).
+_loop_image_destroy()
+{
+	for d in "$@"; do
+		# Retrieve the path of the backing file
+		local f=$(losetup --noheadings --output BACK-FILE $d)
+
+		# Detach the loop device from the backing file
+		_destroy_loop_device "$d"
+
+		# Clean up the backing disk image file
+		[ -n "$f" ] && rm -f "$f"
+	done
+}
 
 # Repair scratch filesystem.  Returns 0 if the FS is good to go (either no
 # errors found or errors were fixed) and nonzero otherwise; also spits out
-- 
2.43.0

[PATCH v7 02/11] fstests: add _clone_mount_option() helper

[Anand Jain]

Adds _clone_mount_option() helper function to handle filesystem-specific
requirements for mounting cloned devices. Abstract the need for -o nouuid
on XFS.

Signed-off-by: Anand Jain <asj@kernel.org>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
---
 common/rc | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/common/rc b/common/rc
index d7e3e0bdfb1e..968ba33686f3 100644
--- a/common/rc
+++ b/common/rc
@@ -414,6 +414,19 @@ _scratch_mount_options()
 					$SCRATCH_DEV $SCRATCH_MNT
 }
 
+# Return filesystem-specific mount options required for mounting clone/snapshot
+# devices.
+_clone_mount_option()
+{
+	case "$FSTYP" in
+	xfs)
+		# Allow mounting a duplicate filesystem on the same host
+		echo "-o nouuid"
+		;;
+	*)
+	esac
+}
+
 _supports_filetype()
 {
 	local dir=$1
-- 
2.43.0

[PATCH v7 03/11] fstests: add FSNOTIFYWAIT_PROG

[Anand Jain]

Define `FSNOTIFYWAIT_PROG` for an upcoming test case that uses `fsnotifywait`.

Signed-off-by: Anand Jain <asj@kernel.org>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
---
 common/config | 1 +
 1 file changed, 1 insertion(+)

diff --git a/common/config b/common/config
index d5299d5b926f..5661fa0ec310 100644
--- a/common/config
+++ b/common/config
@@ -242,6 +242,7 @@ 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 FSNOTIFYWAIT_PROG="$(type -P fsnotifywait)"
 
 # udev wait functions.
 #
-- 
2.43.0

[PATCH v7 04/11] fstests: add _require_unique_f_fsid() helper

[Anand Jain]

Add a helper to check if the target filesystem supports unique f_fsid
tracking across cloned or snapshot instances.

Certain filesystems like XFS, Btrfs, and F2FS ensure unique f_fsid
identifiers per filesystem instance. However, Ext4 derives its f_fsid
directly from its superblock UUID, which leads to identical f_fsid
values on cloned images until the UUID is manually modified by userspace.

Introduce _require_unique_f_fsid() to allow test cases requiring strict
f_fsid uniqueness to skip gracefully on unsupported filesystems.

Signed-off-by: Anand Jain <asj@kernel.org>
---
 common/rc | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/common/rc b/common/rc
index 968ba33686f3..d95eec94f7b7 100644
--- a/common/rc
+++ b/common/rc
@@ -6310,6 +6310,27 @@ _require_fanotify_ioerrors()
 	_notrun "$FSTYP does not support fanotify ioerrors"
 }
 
+# Ext4 derives f_fsid from the superblock UUID, meaning clones share the
+# same f_fsid until their UUIDs diverge. Conversely, XFS, Btrfs,
+# and F2FS ensure f_fsid remains unique per filesystem instance (often by
+# deriving it from the UUID and underlying block device.)
+#
+# Across all filesystems, a UUID collision causes libblkid tools to return
+# non-deterministic device mappings. It is ultimately the responsibility
+# of the userspace utility or use-case to enforce uniqueness when a clone
+# diverges. For details, see mailing list thread discussions:
+#   Link: https://lore.kernel.org/linux-ext4/20260409131238.GC18443@macsyma-wired.lan/
+_require_unique_f_fsid()
+{
+	# Skip the test if the filesystem does not enforce unique f_fsids
+	# natively. Checking this dynamically requires recreating a clone
+	# layout, so we use a static lookup based on FSTYP.
+	if [ "$FSTYP" == "ext4" ]; then
+		_notrun "Target filesystem ($FSTYP) does not guarantee unique f_fsid on clones."
+	fi
+}
+
+
 # Computes a percentage of the available space in a filesystem and
 # returns that quantity in MB. The percentage must not contain a percent
 # sign ("%").
-- 
2.43.0

[PATCH v7 05/11] fstests: verify fanotify isolation on cloned filesystems

[Anand Jain]

Verify that fanotify events are correctly routed to the appropriate
watcher when cloned filesystems are mounted.
Helps verify kernel's event notification distinguishes between devices
sharing the same FSID/UUID.

Signed-off-by: Anand Jain <asj@kernel.org>
---
 tests/generic/801     | 135 ++++++++++++++++++++++++++++++++++++++++++
 tests/generic/801.out |   7 +++
 2 files changed, 142 insertions(+)
 create mode 100644 tests/generic/801
 create mode 100644 tests/generic/801.out

diff --git a/tests/generic/801 b/tests/generic/801
new file mode 100644
index 000000000000..3bfb87d41922
--- /dev/null
+++ b/tests/generic/801
@@ -0,0 +1,135 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2026 Anand Jain <asj@kernel.org>.  All Rights Reserved.
+#
+# FS QA Test 801
+# Verify fanotify FID functionality on cloned filesystems by setting up
+# watchers and making sure notifications are in the correct logs files.
+
+. ./common/preamble
+
+_begin_fstest auto quick mount clone
+
+_require_test
+_require_block_device $TEST_DEV
+_require_loop
+_require_command "$FSNOTIFYWAIT_PROG" fsnotifywait
+_require_unique_f_fsid
+
+_cleanup()
+{
+	cd /
+	[[ -n $pid1 ]] && { kill -TERM "$pid1" 2> /dev/null; wait $pid1; }
+	[[ -n $pid2 ]] && { kill -TERM "$pid2" 2> /dev/null; wait $pid2; }
+
+	if [ "$semanage_added" = "yes" ]; then
+		semanage permissive -d unconfined_t >/dev/null 2>&1 || true
+	fi
+
+	umount $mnt1 $mnt2 2>/dev/null
+	_loop_image_destroy "${devs[@]}" 2> /dev/null
+	rm -r -f $tmp.*
+}
+
+# Run fsnotifywait in unbuffered mode to watch filesystem-wide create events
+monitor_fanotify()
+{
+	local mmnt=$1
+	exec stdbuf -oL $FSNOTIFYWAIT_PROG -m -F -S -e create "$mmnt" 2>&1
+}
+
+# Transform f_fsid into the hi.lo format used in fanotify FID logs
+fsid_to_fid_parts()
+{
+	local fsid=$1
+	# Pad to 16 hex chars (64-bit), then split into two 32-bit halves
+	local padded=$(printf '%016x' "0x${fsid}")
+	local hi=$(printf '%x' "0x${padded:0:8}")   # strips leading zeros
+	local lo=$(printf '%x' "0x${padded:8:8}")   # strips leading zeros
+	echo "${hi}.${lo}"
+}
+
+# Create base loop device and its clone
+devs=()
+_loop_image_create_clone devs
+mkdir -p $TEST_DIR/$seq
+mnt1=$TEST_DIR/$seq/mnt1
+mnt2=$TEST_DIR/$seq/mnt2
+mkdir -p $mnt1
+mkdir -p $mnt2
+
+# Mount both base and clone filesystems using required clone mount options
+_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]} $mnt2 || \
+						_fail "Failed to mount dev2"
+
+# Fetch filesystem IDs to verify the kernel can differentiate between them
+fsid1=$(stat -f -c "%i" $mnt1)
+fsid2=$(stat -f -c "%i" $mnt2)
+
+log1=$tmp.fanotify1
+log2=$tmp.fanotify2
+
+pid1=""
+pid2=""
+echo "Setup FID fanotify watchers on both mnt1 and mnt2"
+
+# Permit unconfined_t domains when SELinux is enforcing to prevent fanotify
+# blockages
+semanage_added="no"
+if [ "$(getenforce 2>/dev/null)" = "Enforcing" ]; then
+    if ! semanage permissive -l | grep -q "unconfined_t"; then
+        semanage permissive -a unconfined_t >/dev/null 2>&1 && semanage_added="yes"
+    fi
+fi
+
+# Start asynchronous fanotify monitors
+( monitor_fanotify "$mnt1" > "$log1" ) &
+pid1=$!
+( monitor_fanotify "$mnt2" > "$log2" ) &
+pid2=$!
+sleep 2
+
+echo "Trigger file creation on mnt1"
+touch $mnt1/file_on_mnt1
+sync
+sleep 1
+
+echo "Trigger file creation on mnt2"
+touch $mnt2/file_on_mnt2
+sync
+sleep 1
+
+echo "Verify fsid in the fanotify"
+kill $pid1 $pid2
+wait $pid1 $pid2 2>/dev/null
+pid1=""
+pid2=""
+
+e_fsid1=$(fsid_to_fid_parts "$fsid1")
+e_fsid2=$(fsid_to_fid_parts "$fsid2")
+
+# Dump debug details to the full log
+echo $fsid1 $e_fsid1 $fsid2 $e_fsid2 >> $seqres.full
+cat $log1 >> $seqres.full
+cat $log2 >> $seqres.full
+
+# Ensure monitor 1 only captured events belonging to mnt 1 and fsid 1
+if grep -qF "$e_fsid1" "$log1" && ! grep -qF "$e_fsid2" "$log1"; then
+	echo "SUCCESS: mnt1 events found"
+else
+	[ ! -s "$log1" ] && echo "  - mnt1 received no events."
+	grep -qF "$e_fsid2" "$log1" && echo "  - mnt1 received event from mnt2."
+fi
+
+# Ensure monitor 2 only captured events belonging to mnt 2 and fsid 2
+if grep -qF "$e_fsid2" "$log2" && ! grep -qF "$e_fsid1" "$log2"; then
+	echo "SUCCESS: mnt2 events found"
+else
+	[ ! -s "$log2" ] && echo "  - mnt2 received no events."
+	grep -qF "$e_fsid1" "$log2" && echo "  - mnt2 received event from mnt1."
+fi
+
+status=0
+exit
diff --git a/tests/generic/801.out b/tests/generic/801.out
new file mode 100644
index 000000000000..d7b318d9f27c
--- /dev/null
+++ b/tests/generic/801.out
@@ -0,0 +1,7 @@
+QA output created by 801
+Setup FID fanotify watchers on both mnt1 and mnt2
+Trigger file creation on mnt1
+Trigger file creation on mnt2
+Verify fsid in the fanotify
+SUCCESS: mnt1 events found
+SUCCESS: mnt2 events found
-- 
2.43.0

[PATCH v7 06/11] fstests: verify f_fsid for cloned filesystems

[Anand Jain]

Verify that the cloned filesystem provides an f_fsid that is persistent
across mount cycles, yet unique from the original filesystem's f_fsid.

Signed-off-by: Anand Jain <asj@kernel.org>
---
 tests/generic/802     | 64 +++++++++++++++++++++++++++++++++++++++++++
 tests/generic/802.out |  4 +++
 2 files changed, 68 insertions(+)
 create mode 100644 tests/generic/802
 create mode 100644 tests/generic/802.out

diff --git a/tests/generic/802 b/tests/generic/802
new file mode 100644
index 000000000000..910807c11584
--- /dev/null
+++ b/tests/generic/802
@@ -0,0 +1,64 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2026 Anand Jain <asj@kernel.org>.  All Rights Reserved.
+#
+# FS QA Test 802
+# Check that the cloned filesystem provides an f_fsid that is persistent
+# across mount cycles if the block device maj:min remains unchanged.
+
+. ./common/preamble
+
+_begin_fstest auto quick mount clone
+
+_require_test
+_require_block_device $TEST_DEV
+_require_loop
+
+_fixed_by_fs_commit btrfs xxxxxxxxxxxx \
+	"btrfs: use on-disk uuid for s_uuid in temp_fsid mounts"
+_fixed_by_fs_commit btrfs xxxxxxxxxxxx \
+	"btrfs: derive f_fsid from on-disk fsuuid and dev_t"
+
+_cleanup()
+{
+	cd /
+	rm -r -f $tmp.*
+	umount $mnt1 $mnt2 2>/dev/null
+	_loop_image_destroy "${devs[@]}" 2> /dev/null
+}
+
+# Setup base loop device and its clone
+devs=()
+_loop_image_create_clone devs
+mkdir -p $TEST_DIR/$seq
+mnt1=$TEST_DIR/$seq/mnt1
+mnt2=$TEST_DIR/$seq/mnt2
+mkdir -p $mnt1
+mkdir -p $mnt2
+
+# Mount both filesystems simultaneously using mandatory clone mount options
+_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]} $mnt2 || \
+						_fail "Failed to mount dev2"
+
+# Capture baseline filesystem IDs for comparison
+fsid_scratch=$(stat -f -c "%i" $mnt1)
+fsid_clone=$(stat -f -c "%i" $mnt2)
+
+# Verify that the fsids remain stable after a mount cycle, even when the
+# mount order is reversed.
+echo "**** fsid after 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"
+
+# Compare post mount-cycle values against the baseline
+stat -f -c "%i" $mnt1 | sed -e "s/$fsid_scratch/FSID_SCRATCH/g"
+stat -f -c "%i" $mnt2 | sed -e "s/$fsid_clone/FSID_CLONE/g"
+
+status=0
+exit
diff --git a/tests/generic/802.out b/tests/generic/802.out
new file mode 100644
index 000000000000..0202a9a2c108
--- /dev/null
+++ b/tests/generic/802.out
@@ -0,0 +1,4 @@
+QA output created by 802
+**** fsid after mount cycle ****
+FSID_SCRATCH
+FSID_CLONE
-- 
2.43.0

[PATCH v7 07/11] fstests: verify libblkid resolution of duplicate UUIDs

[Anand Jain]

Verify how findmnt, df (libblkid) resolve device paths when multiple
block devices share the same FSUUID.

Signed-off-by: Anand Jain <asj@kernel.org>
---
 tests/generic/803     | 72 +++++++++++++++++++++++++++++++++++++++++++
 tests/generic/803.out |  6 ++++
 2 files changed, 78 insertions(+)
 create mode 100644 tests/generic/803
 create mode 100644 tests/generic/803.out

diff --git a/tests/generic/803 b/tests/generic/803
new file mode 100644
index 000000000000..77901592366c
--- /dev/null
+++ b/tests/generic/803
@@ -0,0 +1,72 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2026 Anand Jain <asj@kernel.org>.  All Rights Reserved.
+#
+# FS QA Test 803
+# Check if the mountinfo based findmnt would resolve to the common uuid
+# as per the blkid (libblkid based).
+
+. ./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
+}
+
+# Normalize pool devices and mount points names
+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
+}
+
+# Setup base loop device and its clone
+devs=()
+_loop_image_create_clone devs
+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 identical UUID filesystems simultaneously
+_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
+
+# Btrfs assigned a random uuid for the clone fs before the fix.
+# Cycle mounts and reverse the initialization (source and clone fs) order.
+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/803.out b/tests/generic/803.out
new file mode 100644
index 000000000000..3a130c662430
--- /dev/null
+++ b/tests/generic/803.out
@@ -0,0 +1,6 @@
+QA output created by 803
+DEV1 MNT1 FSUUID
+DEV2 MNT2 FSUUID
+**** mount cycle ****
+DEV1 MNT1 FSUUID
+DEV2 MNT2 FSUUID
-- 
2.43.0

[PATCH v7 08/11] fstests: verify IMA isolation on cloned filesystems

[Anand Jain]

Add testcase to verify IMA measurement isolation when multiple devices
share the same FSUUID.

Signed-off-by: Anand Jain <asj@kernel.org>
---
 tests/generic/804     | 108 ++++++++++++++++++++++++++++++++++++++++++
 tests/generic/804.out |  10 ++++
 2 files changed, 118 insertions(+)
 create mode 100644 tests/generic/804
 create mode 100644 tests/generic/804.out

diff --git a/tests/generic/804 b/tests/generic/804
new file mode 100644
index 000000000000..ced32e6d79dd
--- /dev/null
+++ b/tests/generic/804
@@ -0,0 +1,108 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2026 Anand Jain <asj@kernel.org>.  All Rights Reserved.
+#
+# FS QA Test 804
+# Verify IMA isolation on cloned filesystems:
+# . Mount two devices sharing the same FSUUID (cloned).
+# . Apply an IMA policy to measure files based on that FSUUID.
+# . Create unique files on each mount point to trigger measurements.
+# . Confirm the IMA log correctly attributes events to the respective mounts.
+
+. ./common/preamble
+. ./common/filter
+
+_begin_fstest auto quick clone
+
+_require_test
+_require_block_device $TEST_DEV
+_require_loop
+
+_fixed_by_fs_commit btrfs xxxxxxxxxxxx \
+	"btrfs: use on-disk uuid for s_uuid in temp_fsid mounts"
+_fixed_by_fs_commit btrfs xxxxxxxxxxxx \
+	"btrfs: derive f_fsid from on-disk fsuuid and dev_t"
+
+_cleanup()
+{
+	cd /
+	rm -r -f $tmp.*
+	_unmount $mnt1 2>/dev/null
+	_unmount $mnt2 2>/dev/null
+	_loop_image_destroy "${devs[@]}" 2> /dev/null
+}
+
+# Normalize device names and mount points
+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
+}
+
+# Core helper to set IMA policy and check measurement logs
+do_ima()
+{
+	local ima_policy="/sys/kernel/security/ima/policy"
+	local ima_log="/sys/kernel/security/ima/ascii_runtime_measurements"
+	local fsuuid
+	local mnt=$1
+	local enable=$2
+
+	# Since the in-memory IMA audit log is only cleared upon reboot,
+	# use unique random filenames to avoid log collisions.
+	local foofile=$(mktemp --dry-run foobar_XXXXX)
+
+	echo $mnt $enable | filter_pool
+
+	[ -w "$ima_policy" ] || _notrun "IMA policy not writable"
+
+	fsuuid=$(blkid -s UUID -o value ${devs[0]})
+
+	# Load IMA policy to measure file access specifically for this
+	# filesystem UUID.
+	if [[ $enable -eq 1 ]]; then
+		echo "measure func=FILE_CHECK fsuuid=$fsuuid" > "$ima_policy" || \
+			_notrun "Policy rejected"
+	fi
+
+	# Create a file to trigger measurement and verify its entry in
+	# the IMA log.
+	echo "test_data" > $mnt/$foofile
+
+	# IMA log extract
+	grep $foofile "$ima_log" | awk '{ print $5 }' | filter_pool | \
+						sed "s/$foofile/FOOBAR_FILE/"
+
+	echo "dbg: $mnt $fsuuid $foofile" >> $seqres.full
+	cat $ima_log | tail -1 >> $seqres.full
+	echo >> $seqres.full
+}
+
+# Initialize loop base and cloned instances
+devs=()
+_loop_image_create_clone devs
+mnt1=$TEST_DIR/$seq/mnt1
+mnt2=$TEST_DIR/$seq/mnt2
+mkdir -p $mnt1
+mkdir -p $mnt2
+
+# Concurrently mount both clones
+_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"
+
+#  IMA response on baseline and clone configuration
+do_ima $mnt1 1
+do_ima $mnt2 0
+
+# Cycle mount on the second device.
+echo mount cycle
+_unmount $mnt2
+_mount $mount_opts ${devs[1]} $mnt2 || _fail "Failed to mount dev2"
+
+do_ima $mnt1 0
+do_ima $mnt2 0
+
+status=0
+exit
diff --git a/tests/generic/804.out b/tests/generic/804.out
new file mode 100644
index 000000000000..9804181d6c17
--- /dev/null
+++ b/tests/generic/804.out
@@ -0,0 +1,10 @@
+QA output created by 804
+MNT1 1
+MNT1/FOOBAR_FILE
+MNT2 0
+MNT2/FOOBAR_FILE
+mount cycle
+MNT1 0
+MNT1/FOOBAR_FILE
+MNT2 0
+MNT2/FOOBAR_FILE
-- 
2.43.0

[PATCH v7 09/11] fstests: verify exportfs file handles on cloned filesystems

[Anand Jain]

Ensure that exportfs can correctly decode file handles on a cloned
filesystem across a mount cycle, by file handles generated on a
cloned device remain valid after mount cycle.

Signed-off-by: Anand Jain <asj@kernel.org>
---
 tests/generic/805     | 80 +++++++++++++++++++++++++++++++++++++++++++
 tests/generic/805.out |  2 ++
 2 files changed, 82 insertions(+)
 create mode 100644 tests/generic/805
 create mode 100644 tests/generic/805.out

diff --git a/tests/generic/805 b/tests/generic/805
new file mode 100644
index 000000000000..5827eee039df
--- /dev/null
+++ b/tests/generic/805
@@ -0,0 +1,80 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2026 Anand Jain <asj@kernel.org>.  All Rights Reserved.
+#
+# FS QA Test No. 805
+# Verify that file handles encoded on a cloned filesystem remain valid and
+# resolvable via open_by_handle across a mount cycle and mount order swap.
+
+. ./common/preamble
+
+_begin_fstest auto quick exportfs clone
+
+_require_test
+_require_block_device $TEST_DEV
+_require_exportfs
+_require_loop
+_require_test_program "open_by_handle"
+
+_cleanup()
+{
+	cd /
+	rm -r -f $tmp.*
+	_unmount $mnt1 2>/dev/null
+	_unmount $mnt2 2>/dev/null
+	_loop_image_destroy "${devs[@]}" 2> /dev/null
+}
+
+# Create test dir and test files, encode file handles and store to tmp file
+create_test_files()
+{
+	rm -rf $testdir
+	mkdir -p $testdir
+	$here/src/open_by_handle -cwp -o $tmp.handles_file $testdir $NUMFILES
+}
+
+# Attempt to read and decode the saved file handles on the targeted mount point.
+test_file_handles()
+{
+	local opt=$1
+	local when=$2
+
+	echo test_file_handles after $when
+	$here/src/open_by_handle $opt -i $tmp.handles_file $mnt2 $NUMFILES
+}
+
+# Setup base loop device and its clone
+devs=()
+_loop_image_create_clone devs
+mkdir -p $TEST_DIR/$seq
+mnt1=$TEST_DIR/$seq/mnt1
+mnt2=$TEST_DIR/$seq/mnt2
+mkdir -p $mnt1
+mkdir -p $mnt2
+
+# Mount both identical UUID filesystems simultaneously
+_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]} $mnt2 || \
+						_fail "Failed to mount dev2"
+
+NUMFILES=1
+testdir=$mnt2/testdir
+
+# Decode file handles of files/dir after cycle mount
+create_test_files
+
+# Cycle mounts and reverse initialization sequence to check if
+# file handle lookups are okay
+_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"
+
+# Verify file handles can still be resolved post-mount-cycle
+test_file_handles -rp "cycle mount"
+
+status=0
+exit
diff --git a/tests/generic/805.out b/tests/generic/805.out
new file mode 100644
index 000000000000..29b11ec77ffb
--- /dev/null
+++ b/tests/generic/805.out
@@ -0,0 +1,2 @@
+QA output created by 805
+test_file_handles after cycle mount
-- 
2.43.0

[PATCH v7 10/11] fstests: add _change_metadata_uuid helper

[Anand Jain]

_change_metadata_uuid changes the UUID of the golden filesystem before it
is cloned.

Signed-off-by: Anand Jain <asj@kernel.org>
---
 common/rc | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/common/rc b/common/rc
index d95eec94f7b7..5cd4e025293b 100644
--- a/common/rc
+++ b/common/rc
@@ -1533,6 +1533,29 @@ _scratch_resvblks()
 	esac
 }
 
+# Change the metadata UUID of the given device to a newly generated one.
+# Args:
+#   $1: Block device path to modify.
+_change_metadata_uuid()
+{
+	local temp_mnt=$TEST_DIR/${seq}_mnt
+	local dev=$1
+
+	case $FSTYP in
+	xfs)
+		_require_command "$XFS_ADMIN_PROG" "xfs_admin"
+		$XFS_ADMIN_PROG -U generate $dev >> $seqres.full
+		;;
+	btrfs)
+		_require_command "$BTRFS_TUNE_PROG" "btrfstune"
+		$BTRFS_TUNE_PROG -m $dev
+		;;
+	*)
+		_notrun "Require filesystem with metadata_uuid feature"
+		;;
+	esac
+}
+
 # Create a small loop image, run an optional tuning function ($2) on it,
 # clone it, and attach both to loop devices, returned in ($1).
 # Args:
-- 
2.43.0

[PATCH v7 11/11] fstests: test UUID consistency for clones with metadata_uuid

[Anand Jain]

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
+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