[PATCH v4 6/6] f2fs/009: detect and repair nlink corruption

[Chao Yu <chao@kernel.org>]

This is a regression test to check whether fsck can handle corrupted
nlinks correctly, it uses inject.f2fs to inject nlinks w/ wrong value,
and expects fsck.f2fs can detect such corruption and do the repair.

Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Chao Yu <chao@kernel.org>
---
v4:
- remove unnecessary "_require_command fsck.f2fs"
- clean up _fixed_by_git_commit line
- fix to clean all tmp files in _cleanup
 tests/f2fs/009     | 147 +++++++++++++++++++++++++++++++++++++++++++++
 tests/f2fs/009.out |   2 +
 2 files changed, 149 insertions(+)
 create mode 100755 tests/f2fs/009
 create mode 100644 tests/f2fs/009.out

diff --git a/tests/f2fs/009 b/tests/f2fs/009
new file mode 100755
index 00000000..9120d8a5
--- /dev/null
+++ b/tests/f2fs/009
@@ -0,0 +1,147 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2025 Chao Yu.  All Rights Reserved.
+#
+# FS QA Test No. f2fs/009
+#
+# This is a regression test to check whether fsck can handle corrupted
+# nlinks correctly, it uses inject.f2fs to inject nlinks w/ wrong value,
+# and expects fsck.f2fs can detect such corruption and do the repair.
+#
+. ./common/preamble
+_begin_fstest auto quick
+
+if [ ! -x "$(type -P socket)" ]; then
+	_notrun "Couldn't find socket"
+fi
+
+_require_scratch
+_require_command "$F2FS_INJECT_PROG" inject.f2fs
+
+_fixed_by_git_commit f2fs-tools 958cd6e \
+	"fsck.f2fs: support to repair corrupted i_links"
+
+filename=$SCRATCH_MNT/foo
+hardlink=$SCRATCH_MNT/bar
+
+_cleanup()
+{
+	if [ -n "$pid" ]; then
+		kill $pid &> /dev/null
+		wait
+	fi
+	cd /
+	rm -r -f $tmp.*
+}
+
+for ((i=0;i<14;i++)) do
+	echo "round: " $i >> $seqres.full
+
+	_scratch_mkfs >> $seqres.full
+	_scratch_mount
+
+	if [ $i == 0 ]; then
+		touch $filename
+		ino=`stat -c '%i' $filename`
+		nlink=0
+	elif [ $i == 1 ]; then
+		mkdir $filename
+		ino=`stat -c '%i' $filename`
+		nlink=1
+	elif [ $i == 2 ]; then
+		mknod $filename c 9 0
+		ino=`stat -c '%i' $filename`
+		nlink=0
+	elif [ $i == 3 ]; then
+		mknod $filename b 8 0
+		ino=`stat -c '%i' $filename`
+		nlink=0
+	elif [ $i == 4 ]; then
+		mkfifo $filename
+		ino=`stat -c '%i' $filename`
+		nlink=0
+	elif [ $i == 5 ]; then
+		socket -s $filename >> $seqres.full 2>&1 &
+		pid=$!
+		sleep 2
+		ino=`stat -c '%i' $filename`
+		kill $pid >> $seqres.full 2>&1
+		nlink=0
+	elif [ $i == 6 ]; then
+		ln -s $SCRATCH_MNT/empty $filename
+		ino=`stat -c '%i' $filename`
+		nlink=0
+	elif [ $i == 7 ]; then
+		# orphan inode
+		touch $filename
+		ino=`stat -c '%i' $filename`
+		$F2FS_IO_PROG write 1 0 1 zero atomic_commit $filename 5000 >> $seqres.full 2>&1 &
+		stat $filename >> $seqres.full
+		rm $filename
+		$F2FS_IO_PROG shutdown 1 $SCRATCH_MNT/ >> $seqres.full
+		sleep 6
+		nlink=1
+	elif [ $i == 8 ]; then
+		# hardlink on file
+		touch $filename
+		ino=`stat -c '%i' $filename`
+		ln $filename $hardlink
+		nlink=0
+	elif [ $i == 9 ]; then
+		# hardlink on charactor
+		mknod $filename c 9 0
+		ino=`stat -c '%i' $filename`
+		ln $filename $hardlink
+		nlink=0
+	elif [ $i == 10 ]; then
+		# hardlink on blockdev
+		mknod $filename b 8 0
+		ino=`stat -c '%i' $filename`
+		ln $filename $hardlink
+		nlink=0
+	elif [ $i == 11 ]; then
+		# hardlink on pipe
+		mkfifo $filename
+		ino=`stat -c '%i' $filename`
+		ln $filename $hardlink
+		nlink=0
+	elif [ $i == 12 ]; then
+		# hardlink on socket
+		socket -s $filename >> $seqres.full 2>&1 &
+		pid=$!
+		sleep 2
+		ino=`stat -c '%i' $filename`
+		kill $pid >> $seqres.full 2>&1
+		ln $filename $hardlink
+		nlink=0
+	elif [ $i == 13 ]; then
+		# hardlink on symlink
+		ln -s $SCRATCH_MNT/empty $filename
+		ino=`stat -c '%i' $filename`
+		ln $filename $hardlink
+		nlink=0
+	fi
+
+	if [ $i != 7 ]; then
+		stat $SCRATCH_MNT/* >> $seqres.full
+	fi
+	echo "ino:"$ino >> $seqres.full
+	echo "nlink:"$nlink >> $seqres.full
+
+	_scratch_unmount
+
+	$F2FS_INJECT_PROG --node --mb i_links --nid $ino --val $nlink $SCRATCH_DEV \
+		>> $seqres.full || _fail "fail to inject"
+
+	_check_scratch_fs >> $seqres.full 2>&1 && _fail "can't find corruption"
+	_repair_scratch_fs >> $seqres.full
+	_check_scratch_fs >> $seqres.full 2>&1 || _fail "fsck can't fix corruption"
+
+	_scratch_mount
+	_scratch_unmount
+done
+
+echo "Silence is golden"
+
+status=0
+exit
diff --git a/tests/f2fs/009.out b/tests/f2fs/009.out
new file mode 100644
index 00000000..7e977155
--- /dev/null
+++ b/tests/f2fs/009.out
@@ -0,0 +1,2 @@
+QA output created by 009
+Silence is golden
-- 
2.48.1