On Thu, May 05, 2016 at 05:24:06PM +0200, Andrea Arcangeli wrote: > On Thu, May 05, 2016 at 06:11:10PM +0300, Kirill A. Shutemov wrote: > > Hm. How total_mapcount equal to NULL wouldn't lead to NULL-pointer > > dereference inside page_trans_huge_mapcount()? > > Sorry for the confusion, this was still work in progress and then I've > seen the email from Alex and I sent the last version I had committed > right away. An earlier version of course had the proper checks for > NULL but they got wiped as I transitioned from one model to another > and back. > > > > + page_move_anon_rmap(old_page, vma, address); > > > > compound_head() is missing, I believe. > > Oh yes, fixed that too. > > if (total_mapcount == 1) { > /* > * The page is all ours. Move it to > * our anon_vma so the rmap code will > * not search our parent or siblings. > * Protected against the rmap code by > * the page lock. > */ > page_move_anon_rmap(compound_head(old_page), > vma, address); > } > > > If there's no other issue I can git send-email. I don't see any. > Then we should look into calling page_move_anon_rmap from THP COWs > too, hugetlbfs calls it too. I think we probably need to make > page_move_anon_rmap smarter and optionally let it take the lock for us > after reading page->mapping first to be sure it's really moving it. > > The question is then if trylock or lock_page should be used, my > preference would be just trylock. trylock is probably fine. It's not big deal if we wouldn't move the page to new anon_vma, just nice-to-have. -- Kirill A. Shutemov -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>