raid 5/6 - is this implemented?

["Hendrik Friedel" <hendrik@friedels.name>]

Hello,

I stumbled upon this:
https://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg91938.html

<<This is why scrub after a crash or powerloss with raid56 is important,
while the array is still whole (not degraded). The two problems with
that are:

a) the scrub isn't initiated automatically, nor is it obvious to the
user it's necessary
b) the scrub can take a long time, Btrfs has no partial scrubbing.

Wheras mdadm arrays offer a write intent bitmap to know what blocks to
partially scrub, and to trigger it automatically following a crash or
powerloss.

It seems Btrfs already has enough on-disk metadata to infer a
functional equivalent to the write intent bitmap, via transid. Just
scrub the last ~50 generations the next time it's mounted. Either do
this every time a Btrfs raid56 is mounted. Or create some flag that
allows Btrfs to know if the filesystem was not cleanly shutdown. >>

Has this been implemented in the meantime? If not: Are there any plans 
to?

Regards,
Hendrik