Re: [patch 2/6] mmu_notifier: Callbacks to invalidate address ranges

Jack Steiner
2008-01-30T20:29:31Z

On Wed, Jan 30, 2008 at 11:41:29AM -0800, Christoph Lameter wrote:
> On Wed, 30 Jan 2008, Jack Steiner wrote:
>
> > I see what you mean. I need to review to mail to see why this changed
> > but in the original discussions with Christoph, the invalidate_range
> > callouts were suppose to be made BEFORE the pages were put on the freelist.
>
> Seems that we cannot rely on the invalidate_ranges for correctness at all?
> We need to have invalidate_page() always. invalidate_range() is only an
> optimization.
>

I don't understand your point "an optimization". How would invalidate_range
as currently defined be correctly used?

It _looks_ like it would work only if xpmem/gru/etc takes a refcnt on
the page & drops it when invalidate_range is called. That may work (not sure)
for xpmem but not for the GRU.

--- jack