UDP memory usage accounting(take 2)

This patch set try to introduce memory usage accounting for

UDP(currently ipv4 only).

3 points are improved along with some feedback.

(a) to improve scalability, avoiding atomic_*()s as small as

possible

(b) avoiding UDP specific code in IP layer

(c) supporting socket destruction accounting

To implement (b), there is a side effect which affects

accounting on TCP socket. If you find the good solution

to avoid this side effect, please let me know.

Unfortunately, I don't have any NIC with UFO.

So this patch set is not tested with UFO supported

device.

This patch set is for 2.6.23-rc8.

I appreciate your comment/test/feedback.

Satoshi Oshima