XFS (read-only) support committed to CURRENT

[Jon Dama]

> On the downside, ext3fs and write caches don't mix well, unless you have
> battery backup units sitting on your RAID controllers (I do, and
> switching this MegaRAID - RAID5 on 2+1 - to writeback mode improved
> write speed by a factor of 5 - no database loads though).

This an issue that Kirk has been looking into.  Ideally the problem will
go away completely when both request barriers and NCQ are implemented.
(The latter for people with high-end SATA drives and the former for the
rest of the consumers of ATA).

-Jon