On Thu, 6 May 2010 18:40:39 -0700 (PDT) Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > > > On Fri, 7 May 2010, Mel Gorman wrote: > > > > Page migration requires rmap to be able to find all migration ptes > > created by migration. If the second rmap_walk clearing migration PTEs > > misses an entry, it is left dangling causing a BUG_ON to trigger during > > fault. For example; > > So I still absolutely detest this patch. > > Why didn't the other - much simpler - patch work? The one Rik pointed to: > > http://lkml.org/lkml/2010/4/30/198 > > and didn't do that _disgusting_ temporary anon_vma? > I vote for simple one rather than temporal anon_vma. IIUC, this patch is selected for not to leak exec's problem out to mm/ by magical check. > Alternatively, why don't we just take the anon_vma lock over this region, > so that rmap can't _walk_ the damn thing? > IIUC, move_page_tables() may call "page table allocation" and it cannot be done under spinlock. Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>