From: Hideo AOKI <redacted>
Date: Wed, 26 Mar 2008 16:47:35 -0400

I think that it is inconvenient for caller functions to need
updateing truesize by themselves.

Most cases what I can see are in spots where skb->truesize
cannot be modified because the SKB is possibly charged
to a socket.

In these limited situations where skb->truesize adjustments
really are needed, and legal, it is no harm to open code
things.