Messages in this thread | | | Date | Thu, 16 Feb 2023 18:04:53 +0100 | Subject | Re: [PATCH] mm/migrate: Fix wrongly apply write bit after mkdirty on sparc64 | From | David Hildenbrand <> |
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On 16.02.23 16:30, Peter Xu wrote: > Nick Bowler reported another sparc64 breakage after the young/dirty > persistent work for page migration (per "Link:" below). That's after a > similar report [2]. > > It turns out page migration was overlooked, and it wasn't failing before > because page migration was not enabled in the initial report test environment. > > David proposed another way [2] to fix this from sparc64 side, but that > patch didn't land somehow. Neither did I check whether there's any other > arch that has similar issues. > > Let's fix it for now as simple as moving the write bit handling to be after > dirty, like what we did before. > > Note: this is based on mm-unstable, because the breakage was since 6.1 and > we're at a very late stage of 6.2 (-rc8), so I assume for this specific > case we should target this at 6.3. > > [1] https://lore.kernel.org/all/20221021160603.GA23307@u164.east.ru/ > [2] https://lore.kernel.org/all/20221212130213.136267-1-david@redhat.com/ > > Cc: regressions@leemhuis.info > Fixes: 2e3468778dbe ("mm: remember young/dirty bit for page migrations") > Link: https://lore.kernel.org/all/CADyTPExpEqaJiMGoV+Z6xVgL50ZoMJg49B10LcZ=8eg19u34BA@mail.gmail.com/ > Reported-by: Nick Bowler <nbowler@draconx.ca> > Tested-by: Nick Bowler <nbowler@draconx.ca> > Signed-off-by: Peter Xu <peterx@redhat.com> > --- > mm/huge_memory.c | 6 ++++-- > mm/migrate.c | 2 ++ > 2 files changed, 6 insertions(+), 2 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 1343a7d88299..4fc43859e59a 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -3274,8 +3274,6 @@ void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new) > pmde = mk_huge_pmd(new, READ_ONCE(vma->vm_page_prot)); > if (pmd_swp_soft_dirty(*pvmw->pmd)) > pmde = pmd_mksoft_dirty(pmde); > - if (is_writable_migration_entry(entry)) > - pmde = maybe_pmd_mkwrite(pmde, vma); > if (pmd_swp_uffd_wp(*pvmw->pmd)) > pmde = pmd_mkuffd_wp(pmde); > if (!is_migration_entry_young(entry)) > @@ -3283,6 +3281,10 @@ void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new) > /* NOTE: this may contain setting soft-dirty on some archs */ > if (PageDirty(new) && is_migration_entry_dirty(entry)) > pmde = pmd_mkdirty(pmde); > + if (is_writable_migration_entry(entry)) > + pmde = maybe_pmd_mkwrite(pmde, vma); > + else > + pmde = pmd_wrprotect(pmde); > > if (PageAnon(new)) { > rmap_t rmap_flags = RMAP_COMPOUND; > diff --git a/mm/migrate.c b/mm/migrate.c > index ef68a1aff35c..40c63e77e91f 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -225,6 +225,8 @@ static bool remove_migration_pte(struct folio *folio, > pte = maybe_mkwrite(pte, vma); > else if (pte_swp_uffd_wp(*pvmw.pte)) > pte = pte_mkuffd_wp(pte); > + else > + pte = pte_wrprotect(pte); > > if (folio_test_anon(folio) && !is_readable_migration_entry(entry)) > rmap_flags |= RMAP_EXCLUSIVE;
I'd really rather focus on fixing the root cause instead, anyhow if my patch won't make it:
Acked-by: David Hildenbrand <david@redhat.com>
-- Thanks,
David / dhildenb
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