on CoW fs dolphin not using file clone as cp --reflink=auto and create physical copy file on disk

Reproducible: Always

Steps to Reproduce:
1. on btrfs: create big file (4G for example) ~/4G.bin
2. copy it in dolphin (as cp ~/4G.bin ~/4G(1).bin)
Actual Results:  
files copy bit by bit and writing data

Expected Results:  
file clone momentaly as cp --reflink=auto

Arch linux
Kernel 3.13 rc7 x86_64
$ cat /etc/fstab
LABEL=system /          auto rw,commit=600,relatime,compress=lzo,discard,subvol=@root 0 0
LABEL=system /home auto rw,commit=600,relatime,compress,discard,subvol=@home     0 0