[root@localhost lohr]# lvextend -L +2G /dev/thomas/thomas-lv 
  Size of logical volume thomas/thomas-lv changed from 1.00 GiB (256 extents) to 3.00 GiB (768 extents).
  Logical volume thomas/thomas-lv successfully resized.

[root@localhost lohr]# resize2fs /dev/thomas/thomas-lv 
resize2fs 1.42.9 (28-Dec-2013)
Filesystem at /dev/thomas/thomas-lv is mounted on /mnt/thomas-lv; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 1
The filesystem on /dev/thomas/thomas-lv is now 786432 blocks long.

[root@localhost lohr]# xfs_growfs /dev/thomas/thomas-lv