Messages in this thread | | | From | Nadav Amit <> | Subject | Re: [RFC PATCH 01/14] userfaultfd: set dirty and young on writeprotect | Date | Wed, 20 Jul 2022 18:09:26 +0000 |
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On Jul 20, 2022, at 11:00 AM, David Hildenbrand <david@redhat.com> wrote:
> My patch review skills have seen better days. I thought you'd be > removing the pte_write() check ... :( Tired eyes ... > >> Having said that, I do notice now that pte_mkdirty() should not be done >> only this condition is fulfilled. Instead we should just have >> something like: >> >> if (will_need) { >> ptent = pte_mkyoung(ptent); >> if (pte_write(ptent)) >> ptent = pte_mkdirty(ptent); >> } > > As can_change_pte_writable() will fail if it stumbles over a !pte_dirty > page in current code ... so I assume you would have that code before the > actual pte_mkwrite() logic, correct?
No, I thought this should go after for 2 reasons:
1. You want to allow the PTE to be made writable following the can_change_pte_writable().
2. You do not want to set a non-writable PTE as dirty, especially since it might then be used to determine that the PTE can become writable. Doing so would circumvent cases in which set_page_dirty() needs to be called and break things down.
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