Re: mapping user space buffer to kernel address space

From: Stephen Tweedie (sct@redhat.com)
Date: Mon Oct 16 2000 - 11:40:47 EST


Hi,

On Fri, Oct 13, 2000 at 12:30:49PM +0100, Malcolm Beattie wrote:

> free_kiovec(1, &iobuf); /* does an implicit unlock_kiovec */
>
> It doesn't do an unmap_kiobuf(iobuf) so I don't understand where
> the per-page map->count that map_user_kiobuf incremented gets
> decremented again. Anyone?

The 2.4 raw code I'm looking at does an explicit unmap_kiobuf after
each brw_kiovec().

> Lowlevel I/O on a kiovec can be done
> with something like an ll_rw_kiovec which sct said was going to get
> put in but since I haven't read anything more recent than
> 2.4.0-test5 at the moment, I can't say if it's there or what it
> looks like.

It's being maintained inside the SGI XFS tree right now. They've got
it pretty stable under XFS load so I'll probably put together the
ll_rw_kio functionality using their low level code the next time I do
a kiovec release. I believe that the XFS tree has 2.4.0-test9 support
for this code.

Cheers,
 Stephen
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