Zero-copy transfer with kiobufs: URGENT

[Fabrice Tchakountio <ftchakou@ftchakountio.bbn.com>]

Does some one know how a user program and kernel can exchange
a potentially large chunk of memory with a zero-copy operation (using
kiobufs)?

The key point here is to have the kernel memory pointed to by k_ptr being
handed off to a userland VM area pointed to by u_ptr and the initial
userland memory reassigned to k_ptr without a copy operation.

Here is the thought process:
. first locking down the current user pages into physical memory
. access the physical pages of both userland and kernel and then swap
  the links to those physical pages. (thus updating pgd, pmd entries)
. finally unwire the new userland pages.

Any idea on how to accomplish that on Linux (possibly using kiobufs) ?
A positive reply will be greatly appreciated.

Thanks






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