I know this thread is quite old but I think my input might help someone out there.
Firstly, You got that error because you did not reference the full file path : /dev/mapper/vg_splat-lv_log.
So the command should be below.
[Expert@r80_mgr:0]# resize2fs /dev/mapper/vg_splat-lv_log
Secondly if that command does not work and comes up with the error:
"resize2fs: Bad magic number in super-block while trying to open /dev/mapper/vg_splat-lv_log
Couldn't find valid filesystem superblock."
Use this command instead: xfx_growfs
[Expert@r80_mgr:0]#xfs_growfs /dev/mapper/vg_splat-lv_log
https://stackoverflow.com/questions/26305376/resize2fs-bad-magic-number-in-super-block-while-trying-...