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From: "Mike Durian" <durian@plutotech.com>
To: hackers@freebsd.org
Subject: user vm addr to kernel vm addr
Date: Mon, 20 Oct 1997 20:01:11 -0600
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  In my virtual file system I'd like to speed up reads and writes
by copying directly from the uio structure to a vm address of
a buffer in the user process running on behalf of the filesystem.
I'm currently shoving all the data through a socket that the
user process reads from and copies into a buffer.  I'd like to
go direct and skip the socket writing part.  Does that make sense?
  Anyway, I want to copy from a uio to a different process's vm space.
I can get the vm address of the destination buffer over a socket and
think I can use vm_fault_wire to make sure it stays accessable, but
I don't know how to convert that user space vm address into a
kernel space vm address that I can then use with copyout.
  Is there an easy (or any) way to do this?

mike