There's currently an open Ubuntu bug[0], with the intent to compile NFS_FSCACHE
(and possibly AFS_FSCACHE, 9P_FSCACHE) into the standard Ubuntu kernel.
However, since *_FSCACHE still depends on EXPERIMENTAL, this won't happen.
As Arjan van de Ven pointed out[1], the EXPERIMENTAL flag doesn't mean that
much any more, I propose the following patch to fs/nfs/Kconfig. I'd do the
same for fs/9p/Kconfig and fs/afs/Kconfig, but as I did not test 9p or AFS, I
feel it would not be appropriate for me to remove the flag.