Excerpts from krzf83@gmail.com's message of 2011-08-13 17:59:34 -0400:

I wonder if it would be possible to implement instant unlinking
directory with files in it. Since btrfs is based on b trees it could
be possible. Filesystem would have to "loose" all information on
directory and object in it, and allow overwriting this information.
This would be great feature, because everyone knows that recursive
deleting large directories, with milions of files require huge io
traffic.

I'm afraid the huge IO traffic is required in order to find the files in
the directory and free all the blocks reference by those files.

-chris