We are working on it. We know what patch introduced the regression and 0.7.8 is going out soon to revert it. Until then, users should downgrade to 0.7.6 if they have not already. The Gentoo and EPEL maintainers have pulled the affected releases from the repositories (technically masked on Gentoo). Ubuntu was never affected.
The regression makes it so that creating a new file could fail with ENOSPC after which files created in that directory could become orphaned. Existing files seem okay, but I have yet to confirm that myself and I cannot speak for what others know. It is incredibly difficult to reproduce on systems running coreutils 8.23 or later. So far, reports have only come from people using coreutils 8.22 or older. The directory size actually gets incremented for each orphaned file, which makes it wrong after orphan files happen.
We will likely have some way to recover the orphaned files (like ext4’s lost+found) and fix the directory sizes in the very near future. Snapshots of the damaged datasets are problematic though. Until we have a subcommand to fix it (not including the snapshots, which we would have to list), the damage can be removed from a system that has it either by rolling back to a snapshot before it happened or creating a new dataset with 0.7.6 (or another release other than 0.7.7), moving everything to the new dataset and destroying the old. That will restore things to pristine condition.
It should also be possible to check for pools that are affected, but I have yet to finish my analysis to be certain that no false negatives occur when checking, so I will avoid saying how for now.
