+SCRIPT_DIR=$(dirname $(readlink -f "$0"))
+if [ -z "$TOP" ]; then
+ TOP=$(readlink -f "$SCRIPT_DIR/../")
+ if [ -f "$TOP/configure.ac" ]; then
+ # inside git
+ TEST_TOP="$TOP/tests/"
+ INTERNAL_BIN="$TOP"
+ else
+ # external, defaults to system binaries
+ TOP=$(dirname `which btrfs`)
+ TEST_TOP="$SCRIPT_DIR"
+ INTERNAL_BIN="$TEST_TOP"
+ fi
+else
+ # assume external, TOP set from commandline
+ TEST_TOP="$SCRIPT_DIR"
+ INTERNAL_BIN="$TEST_TOP"
+fi
+if ! [ -x "$TOP/btrfs" ]; then
+ echo "ERROR: cannot execute btrfs from TOP=$TOP"
+ exit 1
+fi