Re: Nick's core remove PageReserved broke vmware...

[Hugh Dickins]

On Mon, 14 Nov 2005, Michael S. Tsirkin wrote:
> Quoting Gleb Natapov <gleb@xxxxxxxxxxxxx>:
> > On Mon, Nov 14, 2005 at 02:25:35PM +0200, Michael S. Tsirkin wrote:
> > > 
> > > There's one thing that I have thought about: what happens
> > > if I set DONTFORK on a page which already has COW set
> > > (e.g. after fork)?
> > > 
> > > It seems that the right thing would be to force a page copy -
> > > otherwise the page can get copied on write.

No, keep it simple, DONTFORK simply marks the area as not to be included
in a fork from that time onwards (until perhaps a DOFORK follows).

> > I thought about it. It should not happen for OpenIB since get_user_pages
> > will break COW for us and I don't think we should complicate DONTFORK
> > implementation by doing break during madvise().

Exactly.

> Hmm, I assumed we call madvise before driver does get_user_pages,
> otherwise an application could fork in between.

I think we're all of us assuming that.

> Should we worry about this?

About what?

Hugh
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