Chris Mason sent in the Btrfs Linux 3.6 pull request on Thursday as part of two branches due to the number of changes as "this pull request is very large."
The two key features added for this next kernel release include:
Sub-Volume Quotas: This allows for full tracking of how many blocks are allocated to each sub-volume (and snapshots) with limits being allowed on a per-sub-volume basis. Chris mentions this could be used so a web-hosting company could give each user their own sub-volume while limiting the amount of space permitted. The user-space side of the Btrfs quota code is still being worked on for a new release soon.
Send/Receive Support: This feature was talked about on Phoronix earlier this month for details.
The pull request for the Btrfs file-system in the Linux 3.6 kernel can be seen at LKML.org.