On 12/13/2016 12:01 PM, James Bottomley wrote: >> > Second aspect is that even if memory i am dealing with is un >> > -addressable i still have struct page for it and i want to be able to >> > use regular page migration. > Tmem keeps a struct page ... what's the problem with page migration? > the fact that tmem locks the page when it's not addressable and you > want to be able to migrate the page even when it's not addressable? Hi James, Why do you say that tmem keeps a 'struct page'? For instance, its ->put_page operation _takes_ a 'struct page', but that's in the delete_from_page_cache() path where the page's last reference has been dropped and it is about to go away. The role of 'struct page' here is just to help create a key so that tmem can find the contents later *without* the original 'struct page'. Jerome's pages here are a new class of half-crippled 'struct page' which support more VM features than ZONE_DEVICE pages, but not quite a full feature set. It supports (and needs to support) a heck of a lot more VM features than memory in tmem would, though. -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
