With the release of 2.6.8.1-mm2, in addition to a probable fix for the memory leak some reported when writing audio CDs [story], Andrew Morton [interview] announced that the long awaited [story] Resier4 filesystem has been merged into his -mm patchset [story]. Hans Reiser provided some information about the history and usage of Reiser4, beginning:

"Reiser4 is a file system based on dancing tree algorithms, and is described at http://www.namesys.com. One should be able to get it up and running just like any of the other filesystems supported by Linux. Configure it to be compiled either builtin or as a module. Create reiser4 filesystem with mkfs.reiser4, mount and use it. More detailed info can be found at http://thebsh.namesys.com/snapshots/LATEST/READ.ME."

In question and answer format - questions from Andrew, answers from Hans - we go on to learn where to obtain the latest Reiser4 tools, and about the current limitations of the filesystem. Hans explains, "Reiser4 has [only] been tested on i386 [...]. Quota support is not ready yet. Should be ready soon. [...] Only the very core functionality is working. Exotic plugins, an API for multiple operation transactions and accessing multiple small files in one syscall, compression, inheritance, all have been postponed until after the core functionality is shipped." Read on for more information, including tips on benchmarking the new filesystem.