Adding overlay-bug test

This test checks that the OverlayFS fixup for CRIU works correctly
by dumping and restoring a process that has an open file in an
OverlayFS mounted directory. This should work no matter if the
Kernel has the OverlayFS bug or not.
Signed-off-by: Gabriel Guimaraes <gabriellimaguimaraes@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

test/Makefile

@@ -13,7 +13,7 @@ all:
 
 .PHONY: all
 
-TESTS = unix-callback mem-snap rpc libcriu mounts/ext security pipes crit socketpairs
+TESTS = unix-callback mem-snap rpc libcriu mounts/ext security pipes crit socketpairs overlayfs
 
 other: .FORCE
 	for t in $(TESTS); do			\

test/overlayfs/Makefile

+run:
+	./run.sh
+
+clean:
+	umount -f overlay_test/z
+	rm -rf overlay_test

test/overlayfs/run.sh

+#!/bin/bash
+
+set -eu
+
+CRIU=../../../criu
+
+setup() {
+	setup_mount
+	sleep 10 3>z/file &
+	PROC_PID=$!
+	echo "PROC_PID=$PROC_PID"
+	sleep 1
+}
+
+setup_mount() {
+	mkdir -p overlay_test
+	cd overlay_test
+	mkdir -p a b c z checkpoint
+	mount -t overlay -o lowerdir=a,upperdir=b,workdir=c overlayfs z
+}
+
+check_criu() {
+	echo "Dumping $PROC_PID..."
+	if ! $CRIU dump -D checkpoint --shell-job -t "${PROC_PID}"; then
+		echo "ERROR! dump failed"
+		return 1
+	fi
+
+	echo "Restoring..."
+	if ! $CRIU restore -d -D checkpoint --shell-job; then
+		echo "ERROR! restore failed"
+		return 1
+	fi
+	return 0
+}
+
+cleanup() {
+	kill -INT "${PROC_PID}" > /dev/null 2>&1
+	umount z
+	cd "${ORIG_WD}"
+	rm -rf overlay_test
+}
+
+main() {
+	ORIG_WD=$(pwd)
+	setup
+
+	check_criu || {
+		cleanup
+		exit 1
+	}
+
+	cleanup
+	echo "OverlayFS C/R successful."
+	exit 0
+}
+
+main