Gentoo ebuilds

From btrfs Wiki

Stable Packages

Official ebuilds are available for both the kernel module (up to 0.17 only) and the utils. Versions of the btrfs filesystem above 0.17 are in Linux kernel sources starting with 2.6.29.

Even though these are the "stable" btrfs versions, they are not marked "stable" in the Gentoo tree, so you will need to add them to /etc/portage/package.keywords (file or dir, whichever you use). For example, on x86:

sys-fs/btrfs ~x86 (only up to version 0.17)
sys-fs/btrfs-progs ~x86

To emerge both (for version 0.18 or above, please only install gentoo btrfs-progs (matching btrfs is already in the kernel):

emerge -av btrfs (only up to version 0.17)
emerge -av btrfs-progs

Then proceed with Getting started.