The Reiser4 file-system
has been ported to run on the Linux 3.7 kernel
. Separately, TRIM/DISCARD support for Reiser4 on solid-state drives is being discussed amongst the remaining Reiser4 developers.
Edward Shishkin, the main developer left working on the Reiser4 file-system in his spare time, announced the port of Reiser4 for Linux 3.7 earlier this month. The actual porting to the 3.7 kernel was largely done by Ivan Shapovalov while Shishkin also made some other changes to be found in the latest version of the Reiser4 file-system patch. The new Reiser4 release was made on the reiserfs-devel mailing list
and the patch to apply against the vanilla/mainline kernel can be found at SourceForge
It's a bit surprising to see Reiser4 ported to Linux 3.7 so quickly considering new kernel support hasn't been a priority
. The most recent Reiser4 file-system benchmarks I did were published on the Linux 3.5 kernel
The only other new Reiser4 development to report on at this time is that there's talk about SSD TRIM/DISCARD support. Most Linux file-systems support the TRIM/DISCARD operation for modern solid-state drives while Reiser4 does not. Reiser4 has no form of solid-state drive optimizations at this point. However, a developer is looking at making this SSD feature available on Reiser4, per this mailing list post
While there's still occasional Reiser4 activity, don't expect it to be merged into the mainline Linux kernel
anytime in the foreseeable future.