[Nexus 6P Android Development] bmg1001:
This is my own little tutorial I made for converting to F2FS. Before following it, I'd like someone to tell me if it's accurate. (It's what I did on my own device...)

When I decided to switch to F2FS literally last night, I decided I wanted to preserve my data, so I'll try my best to explain how to get F2FS working perfectly.

First, you'll want to download a few things.

You'll need a kernel that supports F2FS. I'm using Flash Kernel, for example. Then, you'll need to download this version of TWRP, which was modified to add support for F2FS.

Now, flash the F2FS-enabled version of TWRP using fastboot or TWRP's built-in image flasher (like I did.)

If you've previously used a kernel besides the one that came with your ROM (for example, I was using ElementalX), you should dirty flash your ROM again, along with your GAPPS and any other mods you may use (in my case, Magisk.) Once you have done this, you can go ahead and flash the kernel you downloaded with support for F2FS.

Now, if you want to keep your data, make a backup of your data partition with TWRP and save it somewhere like on a USB-OTG Drive (in my case) or somewhere else safe that isn't on the phone itself, as you'll be needing it later. If you're going for a clean and fresh install, you can skip this step. REMEMBER: Either way, your internal storage will be wiped (meaning your downloads and such.)

Once you have your data partition backed up and saved elsewhere, it's time to begin the process of converting to F2FS. I decided to convert both my data partition and cache partition to F2FS. (If you have previously attempted an F2FS conversion, make sure rm -rf is OFF in TWRP Settings. If on, your partitions will remain as EXT4.) In TWRP, go to "Wipe", then "Advanced Wipe" then either Data or Cache, then "change file system", then select F2FS of course. Repeat for the other partition (data or cache) if you wish to convert that too.

Do not change system, some ROMs do support F2FS for /system, but its very uncommon/rare. If the ROM you're using explicitly states to have F2FS support for /system, then go ahead and change that too (untested by me.) If you do this, you may want to backup your system partition as well to a safe place(not system image.)

Once you have your partitions formatted to F2FS, reboot recovery, and confirm that the partitions you formatted are indeed F2FS by going back to the advanced wipe menu. If you're doing a clean flash, having modified only data and cache, you're all set. Go ahead and reboot.

Now, either plug in your USB-OTG Drive or transfer back your TWRP backup to your device.

THIS NEXT STEP IS CRUCIAL!

Before restoring, go to Settings, then make sure "Use rm -rf instead of formatting" is turned on, otherwise a restore will change your partition back to EXT4. Now, go ahead and restore your data partition, cache isn't necessary, (if doing a /system conversion too, restore /system.)

When it finished, reboot recovery and make sure that the partitions are still F2FS. If so, congratulations! You converted your phone into a F2FS beast without wiping your data (for the most part...) Reboot and if it works, then great! If not, then I messed up this tutorial and I need YOU to tell me what went wrong :/