How to root Huawei P8 Lite with Marshmallow (ALE-L21)
so follow this process at your own responsibility.
This Process in tested on (ALE-L21,L23,L02) other users follow at your own risk.
1. Enable USB debugging
2. Your bootloader should be unlocked ( How to unlock bootloader? )
3. Download TWRP recovery from this link: TWRP 3.0.2
4. After download extract twrp zip file and double click on “install.bat” as shown in image
6. Reboot your phone normally
7. Download and copy these 2 files inside your internal phone memory: Root1.zip , Root2.zip
8. Restart your phone in TWRP mode, Press & hold volume up + power button.
10. Now in TWRP swipe to allow modification, then tap on Install & select “Root1.zip“, follow steps as shown in images.
11. once you have installed Root1 file, Don’t reboot, Install Root2 by following same steps.
12. you are done, your phone is now rooted.
Source: Lordbannakaffalatta of XDA