Another post mainly for myself, just so I know where to find the information quickly the next time I need it. If you have swap on a LVM volume, these commands can be used to resize it (in this case, increase by 100MB):
swapoff /dev/vg_foo/lv_swap lvextend -L+100M /dev/vg_foo/lv_swap mkswap /dev/vg_foo/lv_swap swapon /dev/vg_foo/lv_swap
That is: disable swapping on the volume, extend it, re-create the swap area and enable swapping again.