On Thu, 28 Dec 2006, David Miller wrote:
>
> What happens when we writeback, to the PTEs?
Not a damn thing.
We clear the PTE's _before_ we even start the write. The writeback does
nothing to them. If the user dirties the page while writeback is in
progress, we'll take the page fault and re-dirty it _again_.
> page_mkclean_file() iterates the VMAs and when it finds a shared
> one it goes:
>
> entry = ptep_clear_flush(vma, address, pte);
> entry = pte_wrprotect(entry);
> entry = pte_mkclean(entry);
>
> and that's fine, but that PTE is still marked writable, and
> I think that's key.
No it's not. It's right there. "pte_wrprotect(entry)". You even copied it
yourself.
> What does the fault path do in this situation?
>
> if (write_access) {
> if (!pte_write(entry))
> return do_wp_page(mm, vma, address,
> pte, pmd, ptl, entry);
So we call "do_wp_page()", and that does everythign right.
Linus
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