[PATCH v8 0/13] fstests: add test coverage for cloned filesystem ids

[PATCH v8 0/13] fstests: add test coverage for cloned filesystem ids

[Anand Jain]

v8:
- _require_fs_space: double the required space (x2) to account for both source and clone
- Use proper quoting/unquoting for _mkfs_dev (Thanks Darrick)
- Call _fail() if cp fails
- _require_fanotify_function: check for kernel fsnotify support
- _require_unique_f_fsid: reorganize comments and replace 'if' with 'case' statement (Thanks Darrick)
- Add SEMANAGE_PROG variable (Thanks Darrick)
- fanotify verification: add checks for SEMANAGE_PROG and _require_fanotify_function
- Verify that the monitoring process is actually created

v7:
  https://lore.kernel.org/fstests/cover.1781694879.git.asj@kernel.org

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
   _require_fanotify_function check if kernel supports fs notification
   _require_unique_f_fsid() helper to handle fs difference in fsid implementation

  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 (13):
  fstests: add _loop_image_create_clone() helper
  fstests: add _clone_mount_option() helper
  fstests: add FSNOTIFYWAIT_PROG
  fstests: add _require_fanotify_function
  fstests: add _require_unique_f_fsid() helper
  fstests: add SEMANAGE_PROG
  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         |   2 +
 common/rc             | 135 +++++++++++++++++++++++++++++++++++++++
 tests/generic/801     | 143 ++++++++++++++++++++++++++++++++++++++++++
 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, 713 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 v8 01/13] 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 | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)

diff --git a/common/rc b/common/rc
index 106f044adc2d..e8ff5be0c547 100644
--- a/common/rc
+++ b/common/rc
@@ -1520,6 +1520,71 @@ _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 * 2))
+
+	_create_file_sized $((size * 1024 * 1024)) $img_file ||
+				_fail "Failed: Create $img_file $size"
+
+	loop_devs=("$(_create_loop_device $img_file)")
+
+	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 $img_file_clone || _fail "Failed to copy cloned image"
+
+	loop_devs+=("$(_create_loop_device $img_file_clone)")
+
+	_ret=()
+	for i in "${loop_devs[@]}"; do
+		_ret+=("$i")
+	done
+}
+
+# Teardown loop devices and delete their underlying backing image files.
+# Accepts a list of loop device paths (e.g., /dev/loop0 /dev/loop1).
+_loop_image_destroy()
+{
+	for d in "$@"; 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 v8 02/13] 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 e8ff5be0c547..53e5d9d43af6 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 v8 03/13] 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 v8 04/13] fstests: add _require_fanotify_function

[Anand Jain]

fanotify support may not be compiled into the kernel. Add
_require_fanotify_function to skip tests when fanotify is disabled.

Signed-off-by: Anand Jain <asj@kernel.org>
---
 common/rc | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/common/rc b/common/rc
index 53e5d9d43af6..21b516accdf7 100644
--- a/common/rc
+++ b/common/rc
@@ -6329,6 +6329,13 @@ _require_max_file_range_blocks()
 	esac
 }
 
+_require_fanotify_function()
+{
+        if $FSNOTIFYWAIT_PROG 2>&1 | grep -q "Function not implemented"; then
+                _notrun "Need CONFIG_FANOTIFY and CONFIG_FANOTIFY_ACCESS_PERMISSIONS to be enabled"
+        fi
+}
+
 _require_fanotify_ioerrors()
 {
 	local x
-- 
2.43.0

[PATCH v8 05/13] 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 | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/common/rc b/common/rc
index 21b516accdf7..f73251365a60 100644
--- a/common/rc
+++ b/common/rc
@@ -6356,6 +6356,33 @@ _require_fanotify_ioerrors()
 	_notrun "$FSTYP does not support fanotify ioerrors"
 }
 
+# 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.
+#
+# 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()
+{
+	case "$FSTYP" in
+	ext*)
+		# Ext4 derives f_fsid from the superblock UUID, meaning
+		# clones share the same f_fsid until their UUIDs
+		# diverge.
+		_notrun "Target filesystem ($FSTYP) does not guarantee unique f_fsid on clones."
+		;;
+	*)
+		# Conversely, XFS, Btrfs, and F2FS ensure f_fsid remains
+		# unique per filesystem instance (often by deriving it
+		# from the UUID and underlying block device.)
+		;;
+	esac
+}
+
+
 # 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 v8 06/13] fstests: add SEMANAGE_PROG

[Anand Jain]

Define `SEMANAGE_PROG` for an upcoming test case that uses `semanage(8)`.

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

diff --git a/common/config b/common/config
index 5661fa0ec310..d760b796ce86 100644
--- a/common/config
+++ b/common/config
@@ -243,6 +243,7 @@ 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)"
+export SEMANAGE_PROG="$(type -P semanage)"
 
 # udev wait functions.
 #
-- 
2.43.0

[PATCH v8 07/13] 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     | 143 ++++++++++++++++++++++++++++++++++++++++++
 tests/generic/801.out |   7 +++
 2 files changed, 150 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..904ba9440b3d
--- /dev/null
+++ b/tests/generic/801
@@ -0,0 +1,143 @@
+#! /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 $TEST_DEV
+_require_loop
+_require_command "$SEMANAGE_PROG" semanage
+_require_command "$FSNOTIFYWAIT_PROG" fsnotifywait
+_require_fanotify_function
+_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 $mnt2 >/dev/null 2>&1
+	_loop_image_destroy "${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
+
+if ! kill -0 "$pid1" 2>/dev/null || ! kill -0 "$pid2" 2>/dev/null; then
+	cat "$log1"
+	cat "$log2"
+	_fail "$FSNOTIFYWAIT_PROG setup failed"
+fi
+
+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 v8 08/13] 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 v8 09/13] 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 v8 10/13] 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 v8 11/13] 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 v8 12/13] 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 f73251365a60..45cf9360ba73 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 v8 13/13] 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

Re: [PATCH v8 0/13] fstests: add test coverage for cloned filesystem ids

[Anand Suveer Jain]

Zorro, Ping?

Cheers, Anand

On 25/7/26 15:38, Anand Jain wrote:
> v8:
> - _require_fs_space: double the required space (x2) to account for both source and clone
> - Use proper quoting/unquoting for _mkfs_dev (Thanks Darrick)
> - Call _fail() if cp fails
> - _require_fanotify_function: check for kernel fsnotify support
> - _require_unique_f_fsid: reorganize comments and replace 'if' with 'case' statement (Thanks Darrick)
> - Add SEMANAGE_PROG variable (Thanks Darrick)
> - fanotify verification: add checks for SEMANAGE_PROG and _require_fanotify_function
> - Verify that the monitoring process is actually created
> 
> v7:
>   https://lore.kernel.org/fstests/cover.1781694879.git.asj@kernel.org
> 
> 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
>    _require_fanotify_function check if kernel supports fs notification
>    _require_unique_f_fsid() helper to handle fs difference in fsid implementation
> 
>   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 (13):
>   fstests: add _loop_image_create_clone() helper
>   fstests: add _clone_mount_option() helper
>   fstests: add FSNOTIFYWAIT_PROG
>   fstests: add _require_fanotify_function
>   fstests: add _require_unique_f_fsid() helper
>   fstests: add SEMANAGE_PROG
>   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         |   2 +
>  common/rc             | 135 +++++++++++++++++++++++++++++++++++++++
>  tests/generic/801     | 143 ++++++++++++++++++++++++++++++++++++++++++
>  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, 713 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
> 

Re: [PATCH v8 01/13] fstests: add _loop_image_create_clone() helper

[Zorro Lang]

On Sat, Jul 25, 2026 at 03:38:58PM +0800, Anand Jain wrote:
> 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 | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 65 insertions(+)
> 
> diff --git a/common/rc b/common/rc
> index 106f044adc2d..e8ff5be0c547 100644
> --- a/common/rc
> +++ b/common/rc
> @@ -1520,6 +1520,71 @@ _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()

To capture both the relationship and distinction between this function and
existing _create_loop_device, I'd like to rename it to *_create_cloned_loop_devs*.

> +{
> +	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 * 2))
> +
> +	_create_file_sized $((size * 1024 * 1024)) $img_file ||
> +				_fail "Failed: Create $img_file $size"
> +
> +	loop_devs=("$(_create_loop_device $img_file)")
> +
> +	case $FSTYP in
> +	xfs)
> +		_mkfs_dev -s size=4096 "${loop_devs[0]}"

Why xfs needs a specific "-s size=4096" ? Hardcoding this parameter might cause
failures in certain incompatible environments.

> +		;;
> +	btrfs)
> +		_mkfs_dev "${loop_devs[0]}"

If btrfs is handled the same way as the default `*)` branch below, there is
no need to have a dedicated branch for it.

> +		;;
> +	*)
> +		_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]}"

Since the mkfs command above operates directly on a loop device, I wanted to
make sure, can the sync command be targeted at a block device, and does it
guarantee a cache flush or blockdev page cache sync ?

How about:
  sync -d "${loop_devs[0]}"
  blockdev --flushbufs "${loop_devs[0]}"
or any better idea?

> +	cp $img_file $img_file_clone || _fail "Failed to copy cloned image"
> +
> +	loop_devs+=("$(_create_loop_device $img_file_clone)")
> +
> +	_ret=()
> +	for i in "${loop_devs[@]}"; do
> +		_ret+=("$i")
> +	done

How about:
  _ret=("${loop_devs[@]}")
directly?

> +}
> +
> +# 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()

To keep it consistent with the renamed function above, we could rename this
to *_destroy_cloned_loop_devs*. Alternatively, if we don't consider it
clone-specific, *destroy_loop_devs* would also be good to me.

Thanks,
Zorro

> +{
> +	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
> 

Re: [PATCH v8 02/13] fstests: add _clone_mount_option() helper

[Zorro Lang]

On Sat, Jul 25, 2026 at 03:38:59PM +0800, Anand Jain wrote:
> 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 e8ff5be0c547..53e5d9d43af6 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()

Just a minor nitpick :) For consistency with other *_mount_options functions
(in common/rc), I suggest using "options" instead of "option" -- _clone_mount_options

> +{
> +	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
> 

Re: [PATCH v8 01/13] fstests: add _loop_image_create_clone() helper

[Anand Suveer Jain]

On 1/9/26 20:33, Zorro Lang wrote:
> On Sat, Jul 25, 2026 at 03:38:58PM +0800, Anand Jain wrote:
>> 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 | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 65 insertions(+)
>>
>> diff --git a/common/rc b/common/rc
>> index 106f044adc2d..e8ff5be0c547 100644
>> --- a/common/rc
>> +++ b/common/rc
>> @@ -1520,6 +1520,71 @@ _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()
> 
> To capture both the relationship and distinction between this function and
> existing _create_loop_device, I'd like to rename it to *_create_cloned_loop_devs*.

 I'm fine with _create_cloned_loop_devs() and other patches must be
updated accordingly.

>> +{
>> +	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 * 2))
>> +
>> +	_create_file_sized $((size * 1024 * 1024)) $img_file ||
>> +				_fail "Failed: Create $img_file $size"
>> +


>> +	loop_devs=("$(_create_loop_device $img_file)")
>> +
>> +	case $FSTYP in
>> +	xfs)
>> +		_mkfs_dev -s size=4096 "${loop_devs[0]}"
> 
> Why xfs needs a specific "-s size=4096" ? Hardcoding this parameter might cause
> failures in certain incompatible environments.
>> +		;;
>> +	btrfs)
>> +		_mkfs_dev "${loop_devs[0]}"
> 
> If btrfs is handled the same way as the default `*)` branch below, there is
> no need to have a dedicated branch for it.
> 
>> +		;;
>> +	*)
>> +		_mkfs_dev "${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 "${loop_devs[0]}"
> 
> Since the mkfs command above operates directly on a loop device, I wanted to
> make sure, can the sync command be targeted at a block device, and does it
> guarantee a cache flush or blockdev page cache sync ?
> 
> How about:
>   sync -d "${loop_devs[0]}"
>   blockdev --flushbufs "${loop_devs[0]}"
> or any better idea?
> 

Spotted stale code here while refactoring pre_clone_tune_func.
The updated code with the suggested renames is below.

Agreed that <dev> in sync is redundant. Adding sync serves
as a safeguard if a future mkfs fails to do so. Flushing
via blockdev --flushbufs followed by a global sync properly
follows the data flow path it may not be strictly required
but it is safer.


>> +	cp $img_file $img_file_clone || _fail "Failed to copy cloned image"
>> +
>> +	loop_devs+=("$(_create_loop_device $img_file_clone)")
>> +
>> +	_ret=()
>> +	for i in "${loop_devs[@]}"; do
>> +		_ret+=("$i")
>> +	done
> 
> How about:
>   _ret=("${loop_devs[@]}")
> directly?
> 

yeah. added.

>> +}
>> +
>> +# 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()
> 
> To keep it consistent with the renamed function above, we could rename this
> to *_destroy_cloned_loop_devs*. Alternatively, if we don't consider it
> clone-specific, *destroy_loop_devs* would also be good to me.
> 

 _destroy_cloned_loop_devs() is fine.



Updated code:

---------------------------------
diff --git a/common/rc b/common/rc
index 45cf9360ba73..285463b4e3db 100644
--- a/common/rc
+++ b/common/rc
@@ -1561,7 +1561,7 @@ _change_metadata_uuid()
 # 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()
+_create_cloned_loop_devs()
 {
 	local -n _ret=$1
 	local pre_clone_tune_func="$2"
@@ -1578,37 +1578,28 @@ _loop_image_create_clone()

 	loop_devs=("$(_create_loop_device $img_file)")

-	case $FSTYP in
-	xfs)
-		_mkfs_dev -s size=4096 "${loop_devs[0]}"
-		;;
-	btrfs)
-		_mkfs_dev "${loop_devs[0]}"
-		;;
-	*)
-		_mkfs_dev "${loop_devs[0]}"
-		;;
-	esac
+	_mkfs_dev "${loop_devs[0]}"

 	# 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 "${loop_devs[0]}"
+	# We are about to copy the loop device's backing file
+	# Flush loop device's buffer cache
+	blockdev --flushbufs "${loop_devs[0]}"
+	# Sync system's dirty pages including backing file's
+	sync
 	cp $img_file $img_file_clone || _fail "Failed to copy cloned image"

 	loop_devs+=("$(_create_loop_device $img_file_clone)")

-	_ret=()
-	for i in "${loop_devs[@]}"; do
-		_ret+=("$i")
-	done
+	_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()
+_destroy_cloned_loop_devs()
 {
 	for d in "$@"; do
 		# Retrieve the path of the backing file
-------------------------------


Thanks.
Anand


> Thanks,
> Zorro
> 
>> +{
>> +	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
>>

Re: [PATCH v8 02/13] fstests: add _clone_mount_option() helper

[Anand Suveer Jain]

On 1/9/26 20:39, Zorro Lang wrote:
> On Sat, Jul 25, 2026 at 03:38:59PM +0800, Anand Jain wrote:
>> 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 e8ff5be0c547..53e5d9d43af6 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()
> 
> Just a minor nitpick :) For consistency with other *_mount_options functions
> (in common/rc), I suggest using "options" instead of "option" -- _clone_mount_options
> 

I'm okay with that, though this rename will impact the rest of the patch
series too.

Thanks, Anand


>> +{
>> +	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
>>

Re: [PATCH v8 03/13] fstests: add FSNOTIFYWAIT_PROG

[Zorro Lang]

On Sat, Jul 25, 2026 at 03:39:00PM +0800, Anand Jain wrote:
> 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)"

OK, new *notifywait command.

Reviewed-by: Zorro Lang <zlang@kernel.org>

>  
>  # udev wait functions.
>  #
> -- 
> 2.43.0
> 

Re: [PATCH v8 04/13] fstests: add _require_fanotify_function

[Zorro Lang]

On Sat, Jul 25, 2026 at 03:39:01PM +0800, Anand Jain wrote:
> fanotify support may not be compiled into the kernel. Add
> _require_fanotify_function to skip tests when fanotify is disabled.
> 
> Signed-off-by: Anand Jain <asj@kernel.org>
> ---
>  common/rc | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/common/rc b/common/rc
> index 53e5d9d43af6..21b516accdf7 100644
> --- a/common/rc
> +++ b/common/rc
> @@ -6329,6 +6329,13 @@ _require_max_file_range_blocks()
>  	esac
>  }
>  
> +_require_fanotify_function()
> +{
> +        if $FSNOTIFYWAIT_PROG 2>&1 | grep -q "Function not implemented"; then
> +                _notrun "Need CONFIG_FANOTIFY and CONFIG_FANOTIFY_ACCESS_PERMISSIONS to be enabled"
> +        fi

What happens if $FSNOTIFYWAIT_PROG fails with an error other than
'Function not implemented'?

Thanks,
Zorro

> +}
> +
>  _require_fanotify_ioerrors()
>  {
>  	local x
> -- 
> 2.43.0
> 

Re: [PATCH v8 05/13] fstests: add _require_unique_f_fsid() helper

[Zorro Lang]

On Sat, Jul 25, 2026 at 03:39:02PM +0800, Anand Jain wrote:
> 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 | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
> 
> diff --git a/common/rc b/common/rc
> index 21b516accdf7..f73251365a60 100644
> --- a/common/rc
> +++ b/common/rc
> @@ -6356,6 +6356,33 @@ _require_fanotify_ioerrors()
>  	_notrun "$FSTYP does not support fanotify ioerrors"
>  }
>  
> +# Skip the test if the filesystem does not enforce unique f_fsids
> +# natively. Checking this dynamically requires recreating a clone
> +# layout, so we use a static lookup based on FSTYP.
> +#
> +# Across all filesystems, a UUID collision causes libblkid tools to return
> +# non-deterministic device mappings. It is ultimately the responsibility
> +# of the userspace utility or use-case to enforce uniqueness when a clone
> +# diverges. For details, see mailing list thread discussions:
> +#   Link: https://lore.kernel.org/linux-ext4/20260409131238.GC18443@macsyma-wired.lan/
> +_require_unique_f_fsid()
> +{
> +	case "$FSTYP" in
> +	ext*)
> +		# Ext4 derives f_fsid from the superblock UUID, meaning
> +		# clones share the same f_fsid until their UUIDs
> +		# diverge.
> +		_notrun "Target filesystem ($FSTYP) does not guarantee unique f_fsid on clones."
> +		;;
> +	*)
> +		# Conversely, XFS, Btrfs, and F2FS ensure f_fsid remains
> +		# unique per filesystem instance (often by deriving it
> +		# from the UUID and underlying block device.)
> +		;;
> +	esac

I would prefer to let the experts of each filesystem confirm whether their
fs guarantees a unique f_fsid. How about switching this logic to an *allowlist*
*(whitelist)* approach, where we _notrun by default and only allow filesystems
that explicitly guarantee unique f_fsid support?

  case "$FSTYP" in
  btrfs|xfs|f2fs)
        ;;
  *)
        _notrun "Target filesystem ($FSTYP) does not guarantee unique f_fsid on clones."
        ;;
  esac

Thanks,
Zorro

> +}
> +
> +
>  # 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
> 

Re: [PATCH v8 07/13] fstests: verify fanotify isolation on cloned filesystems

[Zorro Lang]

On Sat, Jul 25, 2026 at 03:39:04PM +0800, Anand Jain wrote:
> 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     | 143 ++++++++++++++++++++++++++++++++++++++++++

`g/801` is already taken. To avoid merge conflicts, you can use a higher
temporary number, and I'll assign the proper number when merging.

>  tests/generic/801.out |   7 +++
>  2 files changed, 150 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..904ba9440b3d
> --- /dev/null
> +++ b/tests/generic/801
> @@ -0,0 +1,143 @@
> +#! /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

Which test condition requires `TEST_DEV` to be a block device?

> +_require_loop
> +_require_command "$SEMANAGE_PROG" semanage
> +_require_command "$FSNOTIFYWAIT_PROG" fsnotifywait
> +_require_fanotify_function
> +_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 $mnt2 >/dev/null 2>&1
> +	_loop_image_destroy "${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

Looks like semanage/SELinux isn't a necessary requirement of this test case,
if so that `_require_command "$SEMANAGE_PROG" semanage` also can be:

  if [ "$(getenforce 2>/dev/null)" = "Enforcing" ]; then
      _require_command "$SEMANAGE_PROG" semanage
  fi

right? And please replace semanage with $SEMANAGE_PROG.

> +
> +# Start asynchronous fanotify monitors
> +( monitor_fanotify "$mnt1" > "$log1" ) &
> +pid1=$!
> +( monitor_fanotify "$mnt2" > "$log2" ) &
> +pid2=$!
> +sleep 2

Are you using `sleep 2` to ensure `fsnotifywait` is fully set up?
I'm not sure if `sleep 2` is 100% reliable here. Since the subsequent tests
strictly depend on `fsnotifywait` starting up properly, is there a more
robust approach than `sleep 2`? For example, could we check the output
in `$log1` and `$log2` to make sure that? Or any other better idea?

> +
> +if ! kill -0 "$pid1" 2>/dev/null || ! kill -0 "$pid2" 2>/dev/null; then

`kill 0` only can make sure the process is running, can't make sure it's
fully set up, right?

> +	cat "$log1"
> +	cat "$log2"
> +	_fail "$FSNOTIFYWAIT_PROG setup failed"
> +fi
> +
> +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=""

unset pid1

> +pid2=""

unset 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

_exit 0

Thanks,
Zorro

> 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
> 

Re: [PATCH v8 08/13] fstests: verify f_fsid for cloned filesystems

[Zorro Lang]

On Sat, Jul 25, 2026 at 03:39:05PM +0800, Anand Jain wrote:
> 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

Better to `rm -rf $TEST_DIR/$seq` before creating a new one.

> +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"

Hmm... what if "$fsid_scratch" is same with "$fsid_clone"?

> +
> +status=0
> +exit

_exit 0

> 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
> 

Re: [PATCH v8 09/13] fstests: verify libblkid resolution of duplicate UUIDs

[Zorro Lang]

On Sat, Jul 25, 2026 at 03:39:06PM +0800, Anand Jain wrote:
> Verify how findmnt, df (libblkid) resolve device paths when multiple

I didn't find the `df` test part in this test case.

> 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 -n (or --noheadings) can be used here (and below) to avoid piping to
`tail -n +2`.

> +findmnt -o SOURCE,TARGET,UUID "${devs[1]}" | tail -n +2 | \
> +				sed -e "s/${fsuuid}/FSUUID/g" | filter_pool

Same here

> +
> +# 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

Same here

> +findmnt -o SOURCE,TARGET,UUID "${devs[1]}" | tail -n +2 | \
> +				sed -e "s/${fsuuid}/FSUUID/g" | filter_pool

Same here

> +
> +status=0
> +exit

_exit 0

> 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
> 

Re: [PATCH v8 10/13] fstests: verify IMA isolation on cloned filesystems

[Zorro Lang]

On Sat, Jul 25, 2026 at 03:39:07PM +0800, Anand Jain wrote:
> 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"

How about a _require_security_ima to make sure there's securityfs
and IMA supporting in current kernel.

> +
> +	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" || \

I'm not sure if we should have this test, especially add it into
auto and quick group. Once an IMA policy is loaded, there is no way to
clear or roll it back, and I am concerned it might potentially interfere
with subsequent tests.

Hmm... how about use `unshare` command to rewrite the do_ima as do_ima_in_ns?
For example:
do_ima_in_ns()
{
	...

    unshare -U -m -p --fork --map-root-user bash <<EOF
		mount -t securityfs securityfs /sys/kernel/security
        ima_policy="/sys/kernel/security/ima/policy"
        ima_log="/sys/kernel/security/ima/ascii_runtime_measurements"
        echo "measure func=FILE_CHECK fsuuid=$uuid" > "\$ima_policy" || exit 1
        ...
EOF
    ret=$?
}

Thanks,
Zorro

> +			_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
> 

Re: [PATCH v8 11/13] fstests: verify exportfs file handles on cloned filesystems

[Zorro Lang]

Re: [PATCH v8 11/13] fstests: verify exportfs file handles on cloned filesystems

[Zorro Lang]

On Sat, Jul 25, 2026 at 03:39:08PM +0800, Anand Jain wrote:
> 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

NUMFILES=${LOAD_FACTOR} ?

> +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
> 

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

[Zorro Lang]

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`.

> +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
> 

Re: [PATCH v8 12/13] fstests: add _change_metadata_uuid helper

[Zorro Lang]

On Sat, Jul 25, 2026 at 03:39:09PM +0800, Anand Jain wrote:
> _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 f73251365a60..45cf9360ba73 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"

How about split this function to _require_metadata_uuid_tool and
_chanage_metadata_uuid ?

> +		$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
>