"Recently, it became apparent that Btrfs has not met the stipulated
criteria. The main reason for this continues to be the still ongoing
development of a decent program for testing and repairing Btrfs file
systems. Bacik had previously hoped that such a program would be
released in May; now, the developer has mentioned a time frame of "a few
weeks", but has also said that the developers' target is the Linux
Plumbers Conference, which will start on 7 September. The Fedora project
will probably make a second attempt to switch in Fedora 17."