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Date: Tue, 25 Aug 2020 15:19:50 +1000 From: Alistair Popple <alistair@...ple.id.au> To: Peter Xu <peterx@...hat.com> Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>, Jérôme Glisse <jglisse@...hat.com>, John Hubbard <jhubbard@...dia.com>, Ralph Campbell <rcampbell@...dia.com>, stable@...r.kernel.org Subject: Re: [PATCH 2/2] mm/rmap: Fixup copying of soft dirty and uffd ptes On Tuesday, 25 August 2020 1:43:59 AM AEST Peter Xu wrote: > > --- a/mm/migrate.c > > +++ b/mm/migrate.c > > @@ -2427,9 +2427,11 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > > > > entry = make_migration_entry(page, mpfn & > > > > MIGRATE_PFN_WRITE); > > > > swp_pte = swp_entry_to_pte(entry); > > > > - if (pte_soft_dirty(pte)) > > + if ((is_swap_pte(pte) && pte_swp_soft_dirty(pte)) > > + || (!is_swap_pte(pte) && pte_soft_dirty(pte))) > > > > swp_pte = pte_swp_mksoft_dirty(swp_pte); > > > > - if (pte_uffd_wp(pte)) > > + if ((is_swap_pte(pte) && pte_swp_uffd_wp(pte)) > > + || (!is_swap_pte(pte) && pte_uffd_wp(pte))) > > > > swp_pte = pte_swp_mkuffd_wp(swp_pte); > > > > set_pte_at(mm, addr, ptep, swp_pte); > > The worst case is we'll call is_swap_pte() four times for each entry. Also > considering we know it's not a pte_none() when reach here, how about: > > if (pte_present(pte)) { > // pte handling of both soft dirty and uffd-wp > } else { > // swap handling of both soft dirty and uffd-wp > } > > ? Works for me, I'd missed we knew it was not a pte_none() so will respin. Thanks! - Alistair > Thanks,
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