On Wed, Aug 10, 2005 at 09:37:28PM +0200, Blaisorblade wrote:
> Just noticed: you can drop them (except the first, which is a nice cleanup).
>
> set_pte handles that, and include/asm-generic/pgtable.h uses coherently
> set_pte_at. I've checked UML by examining "grep pte", and either mk_pte or
> set_pte are used.
>
> Exceptions: fixaddr_user_init (but that should be ok as we shouldn't map it
> actually), pte_modify() (which handles that only for present pages).
>
> But pte_modify is used with set_pte, so probably we could as well drop that
> handling.
>
> Also look, on the "set_pte" theme, at the attached patch. I realized this when
> I needed those lines to work - I was getting a segfault loop.
OK, this sounds right. To recap, we were concerned that when the page
scanner went around clearing dirty (accessed) bits, that
fix_range_common wasn't write (read) protecting the page in order to
emulate the cleared bits.
However, set_pte does set _PAGE_NEWPAGE, which forces the page through
a full update, including dirty/accessed bit emulation.
Correct?
However, I did add some parenthesis to your patch:
WARN_ON(!pte_young(*pte) || (pte_write(*pte) && !pte_dirty(*pte)));
This seems clearer to me.
So, your pte consolidation patch is still in my tree, the other two
pte patches are dropped.
> After using set_pte(), things worked. I have now an almost perfectly working
> implementation of remap_file_pages with protection support.
> There will probably be some other things to update, like swapping locations,
> but I can't get this kernel to fail (it's easier to find bugs in the
> test-program, it grew quite complex).
Excellent.
> I'm going to clean up the code and write changelogs, to send then the patches
> for -mm (hoping the page fault scalability patches don't get in the
> way).
Good.
Jeff
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