On Wednesday 18 June 2008 05:28, Lee Schermerhorn wrote: > On Tue, 2008-06-17 at 19:33 +0100, Hugh Dickins wrote: > > On Tue, 17 Jun 2008, Lee Schermerhorn wrote: > > > Now I wonder if the assertion that newpage count == 1 could be > > > violated? I don't see how. We've just allocated and filled it and > > > haven't unlocked it yet, so we should hold the only reference. Do you > > > agree? > > > > Disagree: IIRC, excellent example of the kind of assumption > > that becomes invalid with Nick's speculative page references. > > > > Someone interested in the previous use of the page may have > > incremented the refcount, and in due course will find that > > it's got reused for something else, and will then back off. > > Yeah. Kosaki-san mentioned that we'd need some rework for the > speculative page cache work. Looks like we'll need to drop the > VM_BUG_ON(). > > I need to go read up on the new invariants we can trust with the > speculative page cache. I don't know if I've added a summary, which is something I should do. The best thing to do is never use page_count, but just use get and put to refcount it. If you really must use it: - If there are X references to a page, page_count will return >= X. - If page_count returns Y, there are no more than Y references to the page. -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
