Default [Q] make /data to f2fs problem, help !!

Hello,
I'm a new developer and try to reference other people's steps to change /data to f2fs. However, I have some problems and it have bothered me a few days. When I chose format /data and type yes, it showed error message " E: Unable to mount '/data' ". As a result, I decided to format then mount /data by myself. Unfortunately, when I used modified TWRP to mount /data which have already formatted by mkfs.f2fs , it showed error message "mounting /data, operation not supported on transport endpoint". However when I mount /data which formatted by make_ext4, it was success. I have already read my threads but I couldn't find a solution. Did any thing I forget to modified? Can anyone help me or give me some hints? Plz

Here is my modify step: (reference ss2man44 's thread in Nexus 7 Developer Discussion ,#Use of F2FS for /data)
1. use f2fs patch to modified kernel, turn on f2fs then flash to my device. It works.
2. modified twrp.fstab and fstab.grouper
3. give statically link to TWRP

Here is my environment:
Device: Nexus 7 (2012)
Kernel version: 3.1.10 (nightly)
Android version: 4.4.3
ROM: CyanogenMod(cm-11)
TWRP: 2.7.1.0 (support F2FS)