create a swap file in Btrfs filesystem

I have spent a lot of time to find out how to create a swap file in my Ubuntu 18.04

However, it is still fail until I found the following article.

Swapon failed: Invalid argument on a Linux system with Btrfs filesystem

There is a limitation in Btrfs filesystem.

Why did I choose Btrfs system, that is because I can use snapshot in my NAS only when I choose Btrfs for my QNAP's filesystem.

Anyway, I can use a swapfile in my Ubuntu with Btrfs filesystem.

please reference the following article.
Swap



Reference:
Swapon failed: Invalid argument on a Linux system with Btrfs filesystem
Swap