[PATCH 15/14] xfs: test xfs_healer can follow private mntns mount moves

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

Make sure that when xfs_healer needs to reopen a filesystem to repair
it, it can still find the filesystem even if it has been mount --move'd.
This requires a bunch of private namespace magic.

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
---
 tests/xfs/1904     |  129 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 tests/xfs/1904.out |    3 +
 2 files changed, 132 insertions(+)
 create mode 100755 tests/xfs/1904
 create mode 100755 tests/xfs/1904.out

diff --git a/tests/xfs/1904 b/tests/xfs/1904
new file mode 100755
index 00000000000000..78e8f5dcb0e834
--- /dev/null
+++ b/tests/xfs/1904
@@ -0,0 +1,129 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2026 Oracle.  All Rights Reserved.
+#
+# FS QA Test 1904
+#
+# Ensure that autonomous self healing fixes the filesystem correctly even if
+# the original mount has moved somewhere else via --move.
+#
+. ./common/preamble
+_begin_fstest auto selfhealing
+
+. ./common/filter
+. ./common/fuzzy
+. ./common/systemd
+
+if [ -n "$IN_MOUNTNS" ]; then
+	_mount --make-rprivate /
+	findmnt -o TARGET,PROPAGATION >> $seqres.full
+
+	_scratch_mount
+	_scratch_invoke_xfs_healer "$tmp.healer" --repair
+
+	# Move the scratch filesystem to a completely different mountpoint so that
+	# we can test if the healer can find it again.
+	new_dir=$TEST_DIR/moocow
+	mkdir -p $new_dir
+	_mount --move $SCRATCH_MNT $new_dir
+
+	df -t xfs >> $seqres.full
+
+	# Access the broken directory to trigger a repair, then poll the directory
+	# for 5 seconds to see if it gets fixed without us needing to intervene.
+	ls $new_dir/some/victimdir > /dev/null 2> $tmp.err
+	_filter_scratch < $tmp.err | _filter_test_dir
+	try=0
+	while [ $try -lt 50 ] && grep -q 'Structure needs cleaning' $tmp.err; do
+		echo "try $try saw corruption" >> $seqres.full
+		sleep 0.1
+		ls $new_dir/some/victimdir > /dev/null 2> $tmp.err
+		try=$((try + 1))
+	done
+	echo "try $try no longer saw corruption or gave up" >> $seqres.full
+	_filter_scratch < $tmp.err | _filter_test_dir
+
+	# List the dirents of /victimdir to see if it stops reporting corruption
+	ls $new_dir/some/victimdir > /dev/null 2> $tmp.err
+	try=0
+	while [ $try -lt 50 ] && grep -q 'Structure needs cleaning' $tmp.err; do
+		echo "retry $try still saw corruption" >> $seqres.full
+		sleep 0.1
+		ls $SCRATCH_MNT/some/victimdir > /dev/null 2> $tmp.err
+		try=$((try + 1))
+	done
+	echo "retry $try no longer saw corruption or gave up" >> $seqres.full
+
+	new_dir_unmount() {
+		_unmount $new_dir
+	}
+
+	# Unmount to kill the healer
+	_scratch_kill_xfs_healer new_dir_unmount
+	cat $tmp.healer >> $seqres.full
+
+	# No need to clean up, the mount ns destructor will detach the
+	# filesystems for us.
+	exit
+fi
+
+_cleanup()
+{
+	command -v _kill_fsstress &>/dev/null && _kill_fsstress
+	cd /
+	rm -r -f $tmp.*
+	if [ -n "$new_dir" ]; then
+		_unmount "$new_dir" &>/dev/null
+		rm -rf "$new_dir"
+	fi
+}
+
+_require_unshare
+_require_test
+_require_scrub
+_require_xfs_io_command "repair"	# online repair support
+_require_xfs_db_command "blocktrash"
+_require_command "$XFS_HEALER_PROG" "xfs_healer"
+_require_command "$XFS_PROPERTY_PROG" "xfs_property"
+_require_scratch
+
+_scratch_mkfs >> $seqres.full
+_scratch_mount
+
+_xfs_has_feature $SCRATCH_MNT rmapbt || \
+	_notrun "reverse mapping required to test directory auto-repair"
+_xfs_has_feature $SCRATCH_MNT parent || \
+	_notrun "parent pointers required to test directory auto-repair"
+_require_xfs_healer $SCRATCH_MNT --repair
+
+# Configure the filesystem for automatic repair of the filesystem.
+$XFS_PROPERTY_PROG $SCRATCH_MNT set autofsck=repair >> $seqres.full
+
+# Create a largeish directory
+dblksz=$(_xfs_get_dir_blocksize "$SCRATCH_MNT")
+echo testdata > $SCRATCH_MNT/a
+mkdir -p "$SCRATCH_MNT/some/victimdir"
+for ((i = 0; i < (dblksz / 255); i++)); do
+	fname="$(printf "%0255d" "$i")"
+	ln $SCRATCH_MNT/a $SCRATCH_MNT/some/victimdir/$fname
+done
+
+# Did we get at least two dir blocks?
+dirsize=$(stat -c '%s' $SCRATCH_MNT/some/victimdir)
+test "$dirsize" -gt "$dblksz" || echo "failed to create two-block directory"
+
+# Break the directory, remount filesystem
+_scratch_unmount
+_scratch_xfs_db -x \
+	-c 'path /some/victimdir' \
+	-c 'bmap' \
+	-c 'dblock 1' \
+	-c 'blocktrash -z -0 -o 0 -x 2048 -y 2048 -n 2048' >> $seqres.full
+
+# mount --move only works if mount propagation is disabled, so we have to start
+# a subshell with a separate mount namespace, disable propagation for the
+# entire directory tree, and only then can we run our tests.
+IN_MOUNTNS=1 unshare -m bash "$0"
+
+status=0
+exit
diff --git a/tests/xfs/1904.out b/tests/xfs/1904.out
new file mode 100755
index 00000000000000..34a46298dd439a
--- /dev/null
+++ b/tests/xfs/1904.out
@@ -0,0 +1,3 @@
+QA output created by 1904
+QA output created by 1904
+ls: reading directory 'TEST_DIR/moocow/some/victimdir': Structure needs cleaning