[Libguestfs] guestfish zerofree on LVM ?

Hi- Is it safe to use the zerofree utility on an ext4 partition inside an LVM with guestfish? I know zerofree works on ext4, but I am unsure about LVM. The info page uses the syntax "zerofree <device>", so using the info page example, could I (safely) do something like the following? $ guestfish Welcome to guestfish, the libguestfs filesystem interactive shell for editing virtual machine filesystems. Type: 'help' for a list of commands 'man' to read the manual 'quit' to quit the shell

<fs> add disk.img

<fs> run

<fs> list-filesystems

/dev/sda1: ext4 /dev/vg_guest/lv_root: ext4 /dev/vg_guest/lv_swap: swap

<fs> zerofree /dev/vg_guest/lv_root

Thanks for any light you can shed on this. -Ben