Improving ext4: bigalloc, inline data, and metadata checksums

udev is prone to creating frothing-at-the-mouth even in otherwise reasonable people, due to the udev authors' patent lack of concern for backward compatibility. Twice now they've broken existing systems without so much as a by-your-leave: firstly with the massive migration of all system-provided state out of /etc/udev.d/rules into /lib/udev/rules: what, you customized them? sucks to be you, now you have to customize them before *building* udev, and more recently with the abrupt movement of /sbin/udevd into /lib/udev without even leaving behind a symlink! Oh, you were starting that at bootup and relying on it to be there? Sorry, we just broke your bootup, your own fault for not reading the release notes! Hope you don't need to downgrade!

(Yes, I read the release notes, so didn't fall into these traps, but FFS, at least the latter problem was trivial to work around -- one line in the makefile to drop a symlink in /sbin -- and they just didn't bother.)