On Wed, Nov 02, 2005 at 10:02:49PM +0000, Hugh Dickins wrote:
> On Thu, 3 Nov 2005, Benjamin Herrenschmidt wrote:
> > On Wed, 2005-11-02 at 21:41 +0000, Hugh Dickins wrote:
> >
> > > The only extant problem here is if the pages are private, and you
> > > fork while this is going on, and the parent user process writes to the
> > > area before completion: then COW leaves the child with the page being
> > > DMAed into, giving the parent a copied page which may be incomplete.
> >
> > Won't happen, and if it does, it's a user error to rely on that working,
> > so it doesn't matter.
>
> I wish everyone else would see it that way! (But some people do
> have valid scenarios where it can't just be ruled out completely.)
>
I am one of those people :)
Last discussion about this issue ended without resolution, but I remember
you mentioned the possibility to leave ptes writable in parent during fork
for private pages mapped for DMA. Is this approach acceptable?
--
Gleb.
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