Ending the debate as to whether XFS will ever be merged [earlier story], it can now be found in Linus' 2.5 BK tree, and will be part of the upcoming 2.5.36 kernel. You can see the XFS-related BK changeset details here.
XFS is a GPL'd high-performance journaling file system under development by SGI since 1994. Version 1.0 was released for Linux on May 1, 2001, with the current release being version 1.1. XFS joins several other journaling filesystems available in the mainline Linux kernel, including ext3, ReiserFS and JFS.
how far is the mainline version from 1.1?
I seem to remember seeing on lkml that the version of XFS in the mainline kernel does not have the full feature set of the XFS 1.1 release that's outside the mainline kernel.
Does anyone have any details?
xfs merge status
look at that ... there's a merge status maintained by Christoph Hellwig.
http://verein.lst.de/~hch/xfs/status.txt