Dave Hansen wrote: > On 05/11/2013 06:23 PM, Kirill A. Shutemov wrote: > > From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> > > > > active/inactive lru lists can contain unevicable pages (i.e. ramfs pages > > that have been placed on the LRU lists when first allocated), but these > > pages must not have PageUnevictable set - otherwise shrink_active_list > > goes crazy: > > > > kernel BUG at /home/space/kas/git/public/linux-next/mm/vmscan.c:1122! > > invalid opcode: 0000 [#1] SMP > > CPU 0 > > Pid: 293, comm: kswapd0 Not tainted 3.8.0-rc6-next-20130202+ #531 > > RIP: 0010:[<ffffffff81110478>] [<ffffffff81110478>] isolate_lru_pages.isra.61+0x138/0x260 > > RSP: 0000:ffff8800796d9b28 EFLAGS: 00010082' > ... > > I'd much rather see a code snippet and description the BUG_ON() than a > register and stack dump. That line number is wrong already. ;) Good point. > > For lru_add_page_tail(), it means we should not set PageUnevictable() > > for tail pages unless we're sure that it will go to LRU_UNEVICTABLE. > > Let's just copy PG_active and PG_unevictable from head page in > > __split_huge_page_refcount(), it will simplify lru_add_page_tail(). > > > > This will fix one more bug in lru_add_page_tail(): > > if page_evictable(page_tail) is false and PageLRU(page) is true, page_tail > > will go to the same lru as page, but nobody cares to sync page_tail > > active/inactive state with page. So we can end up with inactive page on > > active lru. > > The patch will fix it as well since we copy PG_active from head page. > > This all seems good, and if it fixes a bug, it should really get merged > as it stands. Have you been actually able to trigger that bug in any > way in practice? I was only able to trigger it on ramfs transhuge pages split. I doubt there's a way to reproduce it on current upstream code. > Acked-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Thanks! -- 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>