Hi all, this series adds the always_cow mode support after improving our COW write support a little bit first. The always_cow mode stresses the COW path a lot, but with a few xfstests fixups it generall looks good, except for: - a few tests that complain about fragmentation, which is rather inherent in this mode - generic/208 crashing a lot (and generic/095 with 1k block similarly) because a COW fork extent has changed under writeback. As far as I can tell this is because nothing prevents another thread from moving a COW fork extent to the data fork while we are under writeback. I'm currently fully root causing this and looking into a potential fix - xfs/017 crashes occasionally in log recovery because we can't find a refcount tree record that we try to free. I haven't really fully understood this one yet.
