On 04/12/2010 11:44 AM, Linus Torvalds wrote:
quoted text
> 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?

quoted text
>> 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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