[PATCH 0/2] fstests: new testcase to verify show_devname.

[PATCH 0/2] fstests: new testcase to verify show_devname.

[Anand Jain]

Mismatch causes mount -a (UUID) to fail with -EBUSY in libmount 2.37.4.
In libmount 2.40.2 with Btrfs, it shows 'successfully mounted' instead
of 'already mounted', kernel without fix.

Anand Jain (2):
  fstests: new test case to verify show_devname() device path
  fstests: btrfs: new test: show_devname() on multi-device volumes

 tests/btrfs/329       | 107 ++++++++++++++++++++++++++++++++++++++++++
 tests/btrfs/329.out   |  19 ++++++++
 tests/generic/765     |  74 +++++++++++++++++++++++++++++
 tests/generic/765.out |   6 +++
 4 files changed, 206 insertions(+)
 create mode 100755 tests/btrfs/329
 create mode 100644 tests/btrfs/329.out
 create mode 100755 tests/generic/765
 create mode 100644 tests/generic/765.out

-- 
2.49.0

[PATCH 1/2] fstests: new test case to verify show_devname() device path

[Anand Jain]

If the device path under /proc/self/mounts does not match the path shown
by findmnt --uuid, commands like mount -a may fail to recognize that the
device is already mounted and attempt to mount it again. This test case
verifies that the two paths match.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 tests/generic/765     | 74 +++++++++++++++++++++++++++++++++++++++++++
 tests/generic/765.out |  6 ++++
 2 files changed, 80 insertions(+)
 create mode 100755 tests/generic/765
 create mode 100644 tests/generic/765.out

diff --git a/tests/generic/765 b/tests/generic/765
new file mode 100755
index 000000000000..9d4b69344678
--- /dev/null
+++ b/tests/generic/765
@@ -0,0 +1,74 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2025 Oracle.  All Rights Reserved.
+#
+# FS QA Test 765
+#
+# Test if the device paths are compatible with systemd udev tools like
+# mount -a and findmnt.
+# Provide the device dm path to the mount command and verify that it is
+# correctly resolved to the mapper path in the kernel.
+#
+. ./common/preamble
+_begin_fstest auto
+
+node="fstests_${seq}"
+
+_cleanup()
+{
+	cd /
+	rm -r -f $tmp.*
+
+	sed -i "\|[[:space:]]$SCRATCH_MNT[[:space:]]|d" /etc/fstab
+	_systemd_installed && _systemd_reload
+
+	_unmount $SCRATCH_MNT > /dev/null 2>&1
+	udevadm control --start-exec-queue
+	_dmsetup_remove $node
+}
+
+. ./common/systemd
+. ./common/filter
+
+_require_scratch
+_require_block_device $SCRATCH_DEV
+_require_dm_target linear
+
+[ "$FSTYP" = btrfs ] && _fixed_by_kernel_commit XXXXXXXXXXXX \
+		"btrfs: pass device path update from mount thread"
+
+filter_mapper()
+{
+	sed -e "s,\B$scratch_mapper_dev,MAPPER_PATH,g" |\
+		sed -e "s,/dev/dm-[^ ]*,DM_PATH,g" |\
+		_filter_scratch
+}
+
+#size doesn't matter just create it to the device size
+sectors=$(blockdev --getsz $SCRATCH_DEV)
+table="0 $sectors linear  $SCRATCH_DEV 0"
+_dmsetup_create $node --table "$table" || _fail "setup dm device failed"
+
+scratch_mapper_dev=/dev/mapper/$node
+scratch_dm_dev=$(realpath ${scratch_mapper_dev})
+
+# Block external triggers that alter the device path inside the kernel,
+# they are unreliable.
+udevadm control --stop-exec-queue
+_mkfs_dev $scratch_dm_dev
+
+# mount resolves dm path to its mapper path
+_mount --verbose $scratch_dm_dev $SCRATCH_MNT | filter_mapper
+
+fsid=$(findmnt -n -o UUID ${scratch_dm_dev})
+blkid --uuid ${fsid} | filter_mapper
+findmnt --source UUID=${fsid} --noheadings --output SOURCE | filter_mapper
+cat /proc/self/mounts | grep ${SCRATCH_MNT} | \
+				$AWK_PROG '{print $1" "$2}' | filter_mapper
+
+echo "UUID=${fsid} ${SCRATCH_MNT} $FSTYP defaults 0 0" >> /etc/fstab
+_systemd_installed && _systemd_reload
+_mount --verbose -a | grep $SCRATCH_MNT | filter_mapper
+
+status=0
+exit
diff --git a/tests/generic/765.out b/tests/generic/765.out
new file mode 100644
index 000000000000..62abea736f4d
--- /dev/null
+++ b/tests/generic/765.out
@@ -0,0 +1,6 @@
+QA output created by 765
+mount: MAPPER_PATH mounted on SCRATCH_MNT.
+MAPPER_PATH
+MAPPER_PATH
+MAPPER_PATH SCRATCH_MNT
+SCRATCH_MNT             : already mounted
-- 
2.49.0

[PATCH 2/2] fstests: btrfs: new test: show_devname() on multi-device volumes

[Anand Jain]

If the device path under /proc/self/mounts does not match the path shown
by findmnt --uuid, commands like mount -a may fail to recognize that the
device is already mounted and attempt to mount it again. This test case
verifies that the two paths match.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 tests/btrfs/329     | 107 ++++++++++++++++++++++++++++++++++++++++++++
 tests/btrfs/329.out |  19 ++++++++
 2 files changed, 126 insertions(+)
 create mode 100755 tests/btrfs/329
 create mode 100644 tests/btrfs/329.out

diff --git a/tests/btrfs/329 b/tests/btrfs/329
new file mode 100755
index 000000000000..c73e0175c6a4
--- /dev/null
+++ b/tests/btrfs/329
@@ -0,0 +1,107 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2025 Oracle.  All Rights Reserved.
+#
+# FS QA Test 329
+#
+# Test that show_devname() returns a device path that matches findmnt,
+# ensuring that mount -a works correctly for multi-device Btrfs filesystems.
+
+. ./common/preamble
+_begin_fstest auto volume
+
+node="fstests_${seq}"
+
+_cleanup()
+{
+	cd /
+	rm -r -f $tmp.*
+
+	clean_per_iteration
+
+	udevadm control --start-exec-queue
+	_dmsetup_remove $node
+}
+
+. ./common/systemd
+. ./common/filter
+
+_require_scratch_dev_pool 2
+_require_btrfs_forget_or_module_loadable
+_require_block_device $SCRATCH_DEV
+_require_dm_target linear
+
+_fixed_by_kernel_commit XXXXXXXXXXXX \
+	"btrfs: pass device path update from mount thread"
+
+_scratch_dev_pool_get 3
+scratch_devs=($SCRATCH_DEV_POOL)
+#size doesn't matter just create it to the device size
+sectors=$(blockdev --getsz ${scratch_devs[0]})
+table="0 $sectors linear  ${scratch_devs[0]} 0"
+_dmsetup_create $node --table "$table" || _fail "setup dm device failed"
+scratch_mapper_dev=/dev/mapper/$node
+scratch_dm_dev=$(realpath ${scratch_mapper_dev})
+
+clean_per_iteration()
+{
+	_unmount $SCRATCH_MNT > /dev/null 2>&1
+	sed -i "\|[[:space:]]$SCRATCH_MNT[[:space:]]|d" /etc/fstab
+	_systemd_installed && _systemd_reload
+}
+
+filter_mapper()
+{
+	sed -e "s,\B$scratch_mapper_dev,MAPPER_PATH,g" |\
+		sed -e "s,/dev/dm-[^ ]*,DM_PATH,g" |\
+		_filter_scratch_pool
+}
+
+test_dev_path()
+{
+	clean_per_iteration
+	_btrfs_forget_or_module_reload
+
+	echo --- ${devs[@]} ---- | filter_mapper
+	_mkfs_dev "${devs[0]} ${devs[1]}"
+
+	# mount resolves dm path to its mapper path
+	_mount --verbose ${devs[0]} -o device=${devs[1]} $SCRATCH_MNT | \
+								filter_mapper
+
+	fsid=$(findmnt -n -o UUID ${devs[0]})
+	blkid --uuid ${fsid} | filter_mapper
+	findmnt --source UUID=${fsid} --noheadings --output SOURCE | \
+								filter_mapper
+	cat /proc/self/mounts | grep ${SCRATCH_MNT} | \
+				$AWK_PROG '{print $1" "$2}' | filter_mapper
+
+	echo "UUID=${fsid} ${SCRATCH_MNT} $FSTYP defaults 0 0" >> /etc/fstab
+	_systemd_installed && _systemd_reload
+
+	# The error output from `mount -a --verbose` varies.
+        # In libmount 2.37.4, the `mount -a` command will fail with -EBUSY.
+        # In libmount 2.40.2, it will report "Successfully mounted" instead
+        # of "already mounted."
+	_mount --verbose -a | grep $SCRATCH_MNT | _filter_scratch
+}
+
+# Block external triggers such as (64-btrfs-dm.rules) that alter the device path
+# inside the kernel, they are unreliable.
+udevadm control --stop-exec-queue
+secnarios=(
+	"$scratch_dm_dev ${scratch_devs[1]}"
+	"${scratch_devs[2]} ${scratch_devs[1]}"
+	"${scratch_devs[1]} ${scratch_devs[2]}"
+)
+
+devs=()
+for devs_str in "${secnarios[@]}"; do
+	devs=($devs_str)
+	test_dev_path
+done
+udevadm control --start-exec-queue
+
+_scratch_dev_pool_put
+status=0
+exit
diff --git a/tests/btrfs/329.out b/tests/btrfs/329.out
new file mode 100644
index 000000000000..96891dcc68b4
--- /dev/null
+++ b/tests/btrfs/329.out
@@ -0,0 +1,19 @@
+QA output created by 329
+--- DM_PATH SCRATCH_DEV ----
+mount: MAPPER_PATH mounted on /mnt/scratch.
+MAPPER_PATH
+MAPPER_PATH
+MAPPER_PATH /mnt/scratch
+SCRATCH_MNT             : already mounted
+--- SCRATCH_DEV SCRATCH_DEV ----
+mount: SCRATCH_DEV mounted on /mnt/scratch.
+SCRATCH_DEV
+SCRATCH_DEV
+SCRATCH_DEV /mnt/scratch
+SCRATCH_MNT             : already mounted
+--- SCRATCH_DEV SCRATCH_DEV ----
+mount: SCRATCH_DEV mounted on /mnt/scratch.
+SCRATCH_DEV
+SCRATCH_DEV
+SCRATCH_DEV /mnt/scratch
+SCRATCH_MNT             : already mounted
-- 
2.49.0