[PATCH 12/21] fstests: verify libblkid resolution of duplicate UUIDs

[Anand Jain <asj@kernel.org>]

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/903     | 71 +++++++++++++++++++++++++++++++++++++++++++
 tests/generic/903.out |  6 ++++
 2 files changed, 77 insertions(+)
 create mode 100644 tests/generic/903
 create mode 100644 tests/generic/903.out

diff --git a/tests/generic/903 b/tests/generic/903
new file mode 100644
index 000000000000..d8aeba691fd4
--- /dev/null
+++ b/tests/generic/903
@@ -0,0 +1,71 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2026 Anand Jain <asj@kernel.org>.  All Rights Reserved.
+#
+# FS QA Test No. 903
+# 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 tempfsid
+
+_require_test
+_require_loop
+
+_cleanup()
+{
+	cd /
+	rm -r -f $tmp.*
+	umount $mnt1 $mnt2 2>/dev/null
+	_destroy_cloned_loop_devs "${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
+}
+
+rm -rf $TEST_DIR/$seq 2>/dev/null
+mkdir -p $TEST_DIR/$seq
+# Setup base loop device and its clone
+devs=()
+_create_cloned_loop_devs devs
+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_options) ${devs[0]} $mnt1 || \
+						_fail "Failed to mount dev1"
+_mount $(_common_dev_mount_options) $(_clone_mount_options) ${devs[1]} $mnt2 || \
+						_fail "Failed to mount dev2"
+
+findmnt --noheadings -o SOURCE,TARGET,UUID "${devs[0]}" | \
+				sed -e "s/${fsuuid}/FSUUID/g" | filter_pool
+findmnt --noheadings -o SOURCE,TARGET,UUID "${devs[1]}" | \
+				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_options) ${devs[1]} $mnt2 || \
+						_fail "Failed to mount dev2"
+_mount $(_common_dev_mount_options) $(_clone_mount_options) ${devs[0]} $mnt1 || \
+						_fail "Failed to mount dev1"
+
+findmnt --noheadings -o SOURCE,TARGET,UUID "${devs[0]}" | \
+				sed -e "s/${fsuuid}/FSUUID/g" | filter_pool
+findmnt --noheadings -o SOURCE,TARGET,UUID "${devs[1]}" | \
+				sed -e "s/${fsuuid}/FSUUID/g" | filter_pool
+
+_exit 0
diff --git a/tests/generic/903.out b/tests/generic/903.out
new file mode 100644
index 000000000000..7683506e1c94
--- /dev/null
+++ b/tests/generic/903.out
@@ -0,0 +1,6 @@
+QA output created by 903
+DEV1 MNT1 FSUUID
+DEV2 MNT2 FSUUID
+**** mount cycle ****
+DEV1 MNT1 FSUUID
+DEV2 MNT2 FSUUID
-- 
2.43.0