Demonstrate overlay bug with opaque directories using multiple lowers

overlay_test.sh

#!/bin/sh

set -e

root=$(mktemp -d)

echo "--- Running in $root"
cd $root

mkdir -p lower1/lib
touch lower1/lib/hidden

mkdir -p lower2/lib
touch $root/lower2/lib/not-hidden
setfattr -n trusted.overlay.opaque -v y lower2/lib

mkdir upper
mkdir work
mkdir merged

mount -t overlay overlay -o lowerdir=lower2:lower1,upperdir=upper,workdir=work merged

echo "--- Expect \"not-hidden\""
ls merged/lib

touch merged/lib/newfile

echo "--- Expect \"not-hidden\" and \"newfile\""
ls merged/lib

echo "--- Expect no trusted.overlay.opaque xattr"
getfattr -n trusted.overlay.opaque upper/lib

umount merged

mount -t overlay overlay -o lowerdir=lower2:lower1,upperdir=upper,workdir=work merged

echo "--- Expect \"not-hidden\" and \"newfile\""
ls merged/lib

umount merged