Re: copy_one_pte()
From: Matt Keenan
Date: Thu Mar 15 2007 - 15:52:06 EST
Andrew Morton wrote:
(cc restored. Please always do reply-to-all).
On Wed, 14 Mar 2007 08:35:07 +0000 Matt Keenan <tank.en.mate@xxxxxxxxx> wrote:
Christoph Hellwig wrote:
On Tue, Mar 13, 2007 at 08:15:25PM +0100, Zoltan Menyhart wrote:
I had a look at copy_one_pte().
I cannot see any ioproc_update_page() call, not even for the COW pages.
Is it intentional?
There is no such thing as ioproc_update_page in any mainline tree.
You must be looking at some vendor tree with braindead patches applied.
It looks like this function exists as a part of patches to support
Quadrics NICs / RDMA (HPC platforms). The patches are there so the
driver doesn't need to pin pages, it can be informed of page updates
directly. A patch was submitted to l-k sometime in 2005.
Oh Dear.
Which vendor's kernel are we talking about here?
I don't know of any vendor's kernels that support this (but then I run
vanilla kernels on Debian). I just grep'ed for the patch because it
sounded interesting. There was a posting for it to l-k on 26th April
2005 from David Addison of Quadrics Ltd xref
http://lkml.org/lkml/2005/4/26/198 According to David, you (Andrew) and
Andrea Arcangeli asked for it to be posted for some feedback, the main
feedback was on whitespace issues and COWs w.r.t. fork(). Brice Goglin
made an interesting comment about using a similar method but tracking
VMAs rather than address spaces. By the looks of things it never went
into the mainline kernel. I lurk a bit (I sometimes miss things) on l-k
but I hadn't noticed any other methods for dynamic DMA direct to user
space (other than pinning pages), is there anything planned?
Matt
p.s. I Cc'ed Brice Goglin and David Addison
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