Speaking of generic stats; i have a patch netlink ready which may need
some extensions. I did post it  a while back on netdev but didnt get
feedback.

The code looks good and I couldn't spot any errors but I'm not
sure if the locking in gen_copy_[x]stats is a good thing.
Shouldn't that be done earlier by the caller? This prevents
corruption but it allows duplicated TLVs in an skb. I suggest
to make the caller have a lock on his data and only allow one
dumper at the same time until the dump is complete, or at least
provide a lockless variant for callers doing the locking on
their own.