Btrfs devel - Dec 2007 - Extent back references pushed to -unstable

Hello everyone,

I've just pushed out a large change to btrfs-unstable adding extent
back pointers.  These will be a big part of online fsck, and migrating
blocks around in storage pools as devices change.

This is a disk format change for both the progs and the kernel.  It
does have a small performance impact, but the gain in features is well
worth it.  I've documented how the back pointers work here:

http://oss.oracle.com/projects/btrfs/dist/documentation/btrfs-backrefs.html

Soonish it'll have pretty pictures.

Next on my list is back references from inodes back to the directory
item that references them.  This is much less complex than the extent
stuff and should be fairly simple.

After that, I'll update btrfsck to actually verify the back references,
and maybe include some code for online expand/shrink of the FS.

-chris