On Thu, Apr 16, 2015 at 11:57:15AM -0700, Hugh Dickins wrote: > > @@ -1098,6 +1098,8 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, > > if (!swapwrite) > > current->flags |= PF_SWAPWRITE; > > > > + alloc_tlb_ubc(); > > + > > for(pass = 0; pass < 10 && retry; pass++) { > > retry = 0; > > > > @@ -1144,6 +1146,8 @@ out: > > if (!swapwrite) > > current->flags &= ~PF_SWAPWRITE; > > > > + try_to_unmap_flush(); > > This is the right place to aim to flush, but I think you have to make > more changes before it is safe to do so here. > > The putback_lru_page(page) in unmap_and_move() is commented "A page > that has been migrated has all references removed and will be freed". > > If you leave TLB flushing until after the page has been freed, then > there's a risk that userspace will see, not the data it expects at > whatever virtual address, but data placed in there by the next user > of this freed page. > > So you'll need to do a little restructuring first. > Well spotted. I believe you are correct and it almost certainly applies to patch 2 as well for similar reasons. It also impacts the maximum reasonable batch size that can be managed while maintaing safety. I'll do the necessary shuffling tomorrow or Monday. -- Mel Gorman SUSE Labs -- 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>