On Thu, Jan 03, 2019 at 09:29:59AM -0500, Jerome Glisse wrote: > On Wed, Jan 02, 2019 at 08:18:33PM -0800, Matthew Wilcox wrote: > > On Wed, Jan 02, 2019 at 07:32:08PM -0800, John Hubbard wrote: > > > Having the range struct declared in separate places from the mmu_notifier_range_init() > > > calls is not great. But I'm not sure I see a way to make it significantly cleaner, given > > > that __follow_pte_pmd uses the range pointer as a way to decide to issue the mmn calls. > > > > Yeah, I don't think there's anything we can do. But I started reviewing > > the comments, and they don't make sense together: > > > > /* > > * Note because we provide range to follow_pte_pmd it will > > * call mmu_notifier_invalidate_range_start() on our behalf > > * before taking any lock. > > */ > > if (follow_pte_pmd(vma->vm_mm, address, &range, > > &ptep, &pmdp, &ptl)) > > continue; > > > > /* > > * No need to call mmu_notifier_invalidate_range() as we are > > * downgrading page table protection not changing it to point > > * to a new page. > > * > > * See Documentation/vm/mmu_notifier.rst > > */ > > > > So if we don't call mmu_notifier_invalidate_range, why are we calling > > mmu_notifier_invalidate_range_start and mmu_notifier_invalidate_range_end? > > ie, why not this ... > > Thus comments looks wrong to me ... we need to call > mmu_notifier_invalidate_range() those are use by > IOMMU. I might be to blame for those comments thought. Yes, you're to blame for both of them. a4d1a88525138 (Jérôme Glisse 2017-08-31 17:17:26 -0400 791) * Note because we provide start/end to follow_pte_pmd it will a4d1a88525138 (Jérôme Glisse 2017-08-31 17:17:26 -0400 792) * call mmu_notifier_invalidate_range_start() on our behalf a4d1a88525138 (Jérôme Glisse 2017-08-31 17:17:26 -0400 793) * before taking any lock. 0f10851ea475e (Jérôme Glisse 2017-11-15 17:34:07 -0800 794) * No need to call mmu_notifier_invalidate_range() as we are 0f10851ea475e (Jérôme Glisse 2017-11-15 17:34:07 -0800 795) * downgrading page table protection not changing it to point 0f10851ea475e (Jérôme Glisse 2017-11-15 17:34:07 -0800 796) * to a new page.
