Hello, On Fri, Oct 12, 2018 at 12:20:54PM -0400, Zi Yan wrote: > On 12 Oct 2018, at 12:09, [email protected] wrote: > > > From: Jérôme Glisse <[email protected]> > > > > Inside set_pmd_migration_entry() we are holding page table locks and > > thus we can not sleep so we can not call invalidate_range_start/end() > > > > So remove call to mmu_notifier_invalidate_range_start/end() and add > > call to mmu_notifier_invalidate_range(). Note that we are already
Why the call to mmu_notifier_invalidate_range if we're under range_start and followed by range_end? (it's not _range_only_end, if it was _range_only_end the above would be needed) > > calling mmu_notifier_invalidate_range_start/end() inside the function > > calling set_pmd_migration_entry() (see try_to_unmap_one()). > > > > Signed-off-by: Jérôme Glisse <[email protected]> > > Reported-by: Andrea Arcangeli <[email protected]> > > Cc: Andrew Morton <[email protected]> > > Cc: Greg Kroah-Hartman <[email protected]> > > Cc: Zi Yan <[email protected]> > > Cc: Kirill A. Shutemov <[email protected]> > > Cc: "H. Peter Anvin" <[email protected]> > > Cc: Anshuman Khandual <[email protected]> > > Cc: Dave Hansen <[email protected]> > > Cc: David Nellans <[email protected]> > > Cc: Ingo Molnar <[email protected]> > > Cc: Mel Gorman <[email protected]> > > Cc: Minchan Kim <[email protected]> > > Cc: Naoya Horiguchi <[email protected]> > > Cc: Thomas Gleixner <[email protected]> > > Cc: Vlastimil Babka <[email protected]> > > Cc: Michal Hocko <[email protected]> > > Cc: Andrea Arcangeli <[email protected]> > > --- > > mm/huge_memory.c | 7 +------ > > 1 file changed, 1 insertion(+), 6 deletions(-) > > > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > > index 533f9b00147d..93cb80fe12cb 100644 > > --- a/mm/huge_memory.c > > +++ b/mm/huge_memory.c > > @@ -2885,9 +2885,6 @@ void set_pmd_migration_entry(struct > > page_vma_mapped_walk *pvmw, > > if (!(pvmw->pmd && !pvmw->pte)) > > return; > > > > - mmu_notifier_invalidate_range_start(mm, address, > > - address + HPAGE_PMD_SIZE); > > - > > flush_cache_range(vma, address, address + HPAGE_PMD_SIZE); > > pmdval = *pvmw->pmd; > > pmdp_invalidate(vma, address, pvmw->pmd); > > @@ -2898,11 +2895,9 @@ void set_pmd_migration_entry(struct > > page_vma_mapped_walk *pvmw, > > if (pmd_soft_dirty(pmdval)) > > pmdswp = pmd_swp_mksoft_dirty(pmdswp); > > set_pmd_at(mm, address, pvmw->pmd, pmdswp); > > + mmu_notifier_invalidate_range(mm, address, address + HPAGE_PMD_SIZE); It's not obvious why it's needed, if it's needed maybe a comment can be added. > > page_remove_rmap(page, true); > > put_page(page); > > - > > - mmu_notifier_invalidate_range_end(mm, address, > > - address + HPAGE_PMD_SIZE); > > } > > > > void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page > > *new) > > -- > > 2.17.2 > > Yes, these are the redundant calls to > mmu_notifier_invalidate_range_start/end() > in set_pmd_migration_entry(). Thanks for the patch. They're not just redundant, it's called in non blockable path with __mmu_notifier_invalidate_range_start(blockable=true). Furthermore mmu notifier API doesn't support nesting. KVM is actually robust against the nesting: kvm->mmu_notifier_count++; kvm->mmu_notifier_count--; and KVM is always fine with non blockable calls, but that's not universally true for all mmu notifier users. Thanks, Andrea
