Default [Q] Sony Xperia M can't recognize linux parititon on SD card and bricks

Hello,
I have rooted Sony Xperia M and want to use link2sd app for more space. So I created new primary partition ( ext4 ) on my SD card ( by GParted on my linux desktop ). When I use this SD card in my phone, the phone is not able to boot. It makes cycles black screen - SONY logo - short displaing colour screen - black screen .... again. No possibility to use hw buttons to restart. I must remove batery. When I delete linux partition from SD ( or remove SD from slot ), the phone boots normaly. I google that I propably need a new kernel .... I have Rashr app and CWM recovery prepared on my phone ... according to some threat/advice on this forum. Should I flash this recovery? Does this procedure help me? Or does this problem need more complicated diagnostic and repairing? I'm afraid I lose root and totaly brick of this phone ( especially when I will solve this problem alone )

Thank you very much for your help. ( Don't worry I'll click thanks )

my Sony: Android 4.3 kernel 3.4.0 building 15.4.A.0.23 root by Towelroot; superSU ( Framaroot doesn't work on this phone and displayed error which means not rootable )