The mail at [0] contains some more background and rationale but
basically the completed series will allow entities which inject pages
into the networking stack to receive a notification when the stack has
really finished with those pages (i.e. including retransmissions,
clones, pull-ups etc) and not just when the original skb is finished
with, which is beneficial to many subsystems which wish to inject

pages

into the network stack without giving up full ownership of those

page's

lifecycle. It implements something broadly along the lines of what was
described in [1].

If you are doing that, then the network drivers must ensure they
free such skb as soon as the transmit completes - rather than
deferring the 'end of tx' processing until some later time.

Without that the sending code can't reuse the 'page' for another
request - which is one of the things I presume this allows.

(We had issues with this on SVR4 with STREAMS buffers allocated
with esballoc()...)

	David