On Fri, Feb 01, 2008 at 04:05:08PM -0800, Christoph Lameter wrote: > On Fri, 1 Feb 2008, Robin Holt wrote: > > > On Fri, Feb 01, 2008 at 03:19:32PM -0800, Christoph Lameter wrote: > > > On Fri, 1 Feb 2008, Robin Holt wrote: > > > > > > > We are getting this callout when we transition the pte from a read-only > > > > to read-write. Jack and I can not see a reason we would need that > > > > callout. It is causing problems for xpmem in that a write fault goes > > > > to get_user_pages which gets back to do_wp_page that does the callout. > > > > > > Right. You placed it there in the first place. So we can drop the code > > > from do_wp_page? > > > > No, we need a callout when we are becoming more restrictive, but not > > when becoming more permissive. I would have to guess that is the case > > for any of these callouts. It is for both GRU and XPMEM. I would > > expect the same is true for KVM, but would like a ruling from Andrea on > > that. > > do_wp_page is entered when the pte shows that the page is not writeable > and it makes the page writable in some situations. Then we do not > invalidate the remote reference. > > However, when we do COW then a *new* page is put in place of the existing > readonly page. At that point we need to remove the remote pte that is > readonly. Then we install a new pte pointing to a *different* page that is > writable. > > Are you saying that you get the callback when transitioning from a read > only to a read write pte on the *same* page?
I believe that is what we saw. We have not put in any more debug information yet. I will try to squeze it in this weekend. Otherwise, I will probably have to wait until early Monday. Thanks Robin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
