--- /dev/null
+#! /bin/bash
+# FS QA Test 049
+#
+# Test multiple redirects to the same lower dir.
+#
+# Multiple redirects to the same lower dir will falsely return the same
+# st_ino/st_dev for two different upper dirs and will cause 'diff' to
+# falsely report that content of directories is the same when it is not.
+#
+# This test checks that overlayfs detects and fails lookup of a multiply
+# redirected dir.
+#
+# The check for multiply redirected dir was implemented by kernel titled
+# "ovl: hash directory inodes for fsnotify"
+#
+#-----------------------------------------------------------------------
+# Copyright (C) 2018 CTERA Networks. All Rights Reserved.
+# Author: Amir Goldstein <amir73il@gmail.com>
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it would be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write the Free Software Foundation,
+# Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+#-----------------------------------------------------------------------
+#
+
+seq=`basename $0`
+seqres=$RESULT_DIR/$seq
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+status=1 # failure is the default!
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+_cleanup()
+{
+ cd /
+ rm -f $tmp.*
+}
+
+# Rename lower dir to create a redirected upper dir and
+# touch lower file to create copy up with origin xattr
+create_redirect()
+{
+ local redirect=$1
+
+ mkdir -p $lowerdir/origin
+ touch $lowerdir/origin/file
+
+ _scratch_mount -o redirect_dir=on
+ touch $SCRATCH_MNT/origin/file
+ mv $SCRATCH_MNT/origin $SCRATCH_MNT/$redirect
+
+ $UMOUNT_PROG $SCRATCH_MNT
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+
+rm -f $seqres.full
+
+# real QA test starts here
+_supported_fs overlay
+_supported_os Linux
+_require_scratch
+_require_scratch_feature redirect_dir
+
+# remove all files from previous runs
+_scratch_mkfs
+
+upperdir=$OVL_BASE_SCRATCH_MNT/$OVL_UPPER
+lowerdir=$OVL_BASE_SCRATCH_MNT/$OVL_LOWER
+
+# Create redirected dir with copied up file
+create_redirect redirect1
+# Duplicate the redirected dir and copied up file
+cp -a $upperdir/redirect1 $upperdir/redirect2
+
+# Diverge the content of the two copies of file
+# and the content of two copies of redirected dir
+echo right >> $upperdir/redirect1/file
+touch $upperdir/redirect1/right
+echo wrong >> $upperdir/redirect2/file
+touch $upperdir/redirect2/wrong
+
+_scratch_mount -o redirect_dir=on
+
+# If both copies of file/dir use the same st_dev/st_ino in overlay
+# diff won't detect that their content differs
+diff -q $SCRATCH_MNT/redirect1/file $SCRATCH_MNT/redirect2/file &>/dev/null && \
+ echo "diff on files inside duplicate redirect parent doesn't know right from wrong!"
+
+diff -q $SCRATCH_MNT/redirect1 $SCRATCH_MNT/redirect2 &> /dev/null && \
+ echo "diff on duplicate redirect dirs doesn't know right from wrong!"
+
+# success, all done
+echo "Silence is golden"
+status=0
+exit