On Wed 29-08-18 14:14:25, Jerome Glisse wrote: > On Wed, Aug 29, 2018 at 10:24:44AM -0700, Mike Kravetz wrote: [...] > > What would be the best mmu notifier interface to use where there are no > > start/end calls? > > Or, is the best solution to add the start/end calls as is done in later > > versions of the code? If that is the suggestion, has there been any change > > in invalidate start/end semantics that we should take into account? > > start/end would be the one to add, 4.4 seems broken in respect to THP > and mmu notification. Another solution is to fix user of mmu notifier, > they were only a handful back then. For instance properly adjust the > address to match first address covered by pmd or pud and passing down > correct page size to mmu_notifier_invalidate_page() would allow to fix > this easily. > > This is ok because user of try_to_unmap_one() replace the pte/pmd/pud > with an invalid one (either poison, migration or swap) inside the > function. So anyone racing would synchronize on those special entry > hence why it is fine to delay mmu_notifier_invalidate_page() to after > dropping the page table lock. > > Adding start/end might the solution with less code churn as you would > only need to change try_to_unmap_one(). What about dependencies? 369ea8242c0fb sounds like it needs work for all notifiers need to be updated as well. Anyway, I am wondering why we haven't see any bugs coming from incomplete range invalidation. How would those exhibit? -- Michal Hocko SUSE Labs
