On Wed 11-07-18 14:10:52, Kirill A. Shutemov wrote: [...] > It's okay. I have another suggestion that also doesn't require VM_DEAD > trick too :) > > 1. Take mmap_sem for write; > 2. Adjust VMA layout (split/remove). After the step all memory we try to > unmap is outside any VMA. > 3. Downgrade mmap_sem to read. > 4. Zap the page range. > 5. Drop mmap_sem. > > I believe it should be safe. > > The pages in the range cannot be re-faulted after step 3 as find_vma() > will not see the corresponding VMA and deliver SIGSEGV. > > New VMAs cannot be created in the range before step 5 since we hold the > semaphore at least for read the whole time. > > Do you see problem in this approach? Yes this seems to be safe. At least from the first glance. -- Michal Hocko SUSE Labs
