On 10/26/2012 02:48 PM, Linus Torvalds wrote:
On Fri, Oct 26, 2012 at 11:46 AM, Rik van Riel <r...@redhat.com> wrote:

The function ptep_set_access_flags is only ever used to upgrade
access permissions to a page.

NOTE: It's *not* "access permissions". It's "access flags".

Big difference. This is not about permissions at all.

It looks like do_wp_page also sets the write bit in the pte
"entry" before passing it to ptep_set_access_flags, making
that the place where the write bit is set in the pte.

Is this a bug in do_wp_page?

Am I reading things wrong?

reuse:
                flush_cache_page(vma, address, pte_pfn(orig_pte));
                entry = pte_mkyoung(orig_pte);
                entry = maybe_mkwrite(pte_mkdirty(entry), vma);
if (ptep_set_access_flags(vma, address, page_table, entry,1))
                        update_mmu_cache(vma, address, page_table);

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