Re: [PATCH -v2] rmap: make anon_vma_prepare link in all the anon_vmasof a mergeable VMA

[Rik van Riel]

On 04/12/2010 11:44 AM, Linus Torvalds wrote:
> On Sun, 11 Apr 2010, Rik van Riel wrote:
> > Looking around the code some more, zap_pte_range()
> > calls page_remove_rmap(), which leaves the
> > page->mapping in place and has this comment:
>
> See my earlier email about this exact issue. It's well-known that there
> are stale page->mapping pointers. The "page_mapped()" check _should_ have
> meant that in that case we never follow them, though.

Good point.  I wonder if we have some SMP reordering
issue then?

> > I wonder if we can clear page->mapping here, if
> > list_is_singular(anon_vma->head).  That way we
> > will not leave stale pointers behind.
>
> What does that help? What if list _isn't_ singular?

Yeah, that was a bad idea.  Looking at the same code for
11 days straight seems to have put some knots in my brain :)
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