#! /bin/bash
# SPDX-License-Identifier: GPL-2.0
# Copyright (C) 2020 CTERA Networks. All Rights Reserved.
#
# FS QA Test 072
#
# Test overlay nlink when adding upper hardlinks.
#
# nlink of overlay inode could be dropped indefinitely by adding
# unaccounted upper hardlinks underneath a mounted overlay and
# trying to remove them.
#
# This is a variant of test overlay/034 with mangling of upper instead
# of lower hardlinks. Unlike overlay/034, this test does not require the
# inode index feature and will pass whether is it enabled or disabled
# by default.
#
# This is a regression test for kernel commit 83552eacdfc0
# ("ovl: fix WARN_ON nlink drop to zero").
# Without the fix, the test triggers
# WARN_ON(inode->i_nlink == 0) in drop_link().
#
seq=`basename $0`
seqres=$RESULT_DIR/$seq
echo "QA output created by $seq"

tmp=/tmp/$$
status=1	# failure is the default!
trap "_cleanup; exit \$status" 0 1 2 3 15

_cleanup()
{
	cd /
	rm -f $tmp.*
}

# get standard environment, filters and checks
. ./common/rc
. ./common/filter

# remove previous $seqres.full before test
rm -f $seqres.full

# real QA test starts here
_supported_fs overlay
_require_scratch

upperdir=$OVL_BASE_SCRATCH_MNT/$OVL_UPPER

# Remove all files from previous tests
_scratch_mkfs

# Create upper hardlink
mkdir -p $upperdir
touch $upperdir/0
ln $upperdir/0 $upperdir/1

_scratch_mount

# Verify overlay inode nlink 2 same as upper inode
stat -c '%h' $SCRATCH_MNT/0

# Add upper hardlinks while overlay is mounted - overlay inode nlink
# is not being updated
ln $upperdir/0 $upperdir/2
ln $upperdir/0 $upperdir/3

# Unlink the 2 un-accounted upper hardlinks - overlay inode nlinks
# drops 2 and may reach 0 if the situation is not detected
rm $SCRATCH_MNT/2
rm $SCRATCH_MNT/3

# Check if getting ENOENT when trying to link !I_LINKABLE with nlink 0
ln $SCRATCH_MNT/0 $SCRATCH_MNT/4

# Unlink all hardlinks - if overlay inode nlink is 0, this will trigger
# WARN_ON() in drop_nlink()
rm $SCRATCH_MNT/0
rm $SCRATCH_MNT/1
rm $SCRATCH_MNT/4

echo "Silence is golden"
status=0
exit