added mount_subvolume

modules/btrfs.mod

@@ -92,3 +92,9 @@ sudo /bin/find $1 -maxdepth $2 -type d -exec sh -c '
 #            btrfs subvolume show "$d" >/dev/null 2>&1 && printf "%s\n" "$d"
 #         done
 #      ' find-sh {} + \) \)
+
+mount_subvolume () {
+  mkdir -p $3
+  echo msudo mount $1 -o subvol=$2 $3
+  sudo mount $1 -o subvol=$2 $3
+}