On Thu, 19 Jun 2008 17:00:59 +0900 Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx> wrote: > > > > - unlock = putback_lru_page(newpage); > > > > + putback_lru_page(newpage); > > > > } else > > > > newpage->mapping = NULL; > > > > > > originally move_to_lru() called in unmap_and_move(). > > > unevictable infrastructure patch move to this point for > > > calling putback_lru_page() under page locked. > > > > > > So, your patch remove page locked dependency. > > > move to unmap_and_move() again is better. > > > > > > it become page lock holding time reducing. > > > > > ok, will look into again. > > > > I agree with Kosaki-san. > > And VM_BUG_ON(page_count(newpage) != 1) in unmap_and_move() > is not correct again, IMHO. > I got this BUG actually when testing this patch(with > migratin_entry_wait fix). > > unmap_and_move() > move_to_new_page() > migrate_page() > remove_migration_ptes() > putback_lru_page() (*1) > : > if (!newpage->mapping) (*2) > VM_BUG_ON(page_count(newpage) != 1) > > If a anonymous page(without mapping) is migrated successfully, > this page is moved back to lru by putback_lru_page()(*1), > and the page count becomes 1(pte only). > yes. > At the same time(between *1 and *2), if the process > that owns this page are freeing this page, the page count > becomes 0 and ->mapping becomes NULL by free_hot_cold_page(), > so this BUG is caused. > Agree, I see. > I've not seen this BUG on real HW yet(seen twice on fake-numa > hvm guest of Xen), but I think it can happen theoretically. > That's (maybe) because page->mapping is not cleared when it's removed from rmap. (and there is pagevec to dealy freeing....) But ok, I see your point. KOSAKI-san is now writing patch set to fix the whole. please see it. Thanks, -Kame -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
