On Mon, Jul 20, 2015 at 01:27:55PM +0200, Vlastimil Babka wrote: > On 07/16/2015 02:06 AM, Minchan Kim wrote: > >On Wed, Jul 15, 2015 at 03:33:59PM +0900, Joonsoo Kim wrote: > >>@@ -2003,7 +2005,7 @@ int __isolate_free_page(struct page *page, unsigned int order) > >> zone->free_area[order].nr_free--; > >> rmv_page_order(page); > >> > >>- set_page_owner(page, order, 0); > >>+ set_page_owner(page, order, __GFP_MOVABLE); > > > >It seems the reason why __GFP_MOVABLE is okay is that __isolate_free_page > >works on a free page on MIGRATE_MOVABLE|MIGRATE_CMA's pageblock. But if we > >break the assumption in future, here is broken again? > > I didn't study the page owner code yet and I'm catching up after > vacation, but I share your concern. But I don't think the > correctness depends on the pageblock we are isolating from. I think > the assumption is that the isolated freepage will be used as a > target for migration, and that only movable pages can be > successfully migrated (but also CMA pages, and that information can > be lost?). However there are also efforts to allow migrate e.g. > driver pages that won't be marked as movable. And I'm not sure which > migratetype are balloon pages which already have special migration > code. I am one of people who want to migrate driver pages from compaction from zram point of view so I agree with you. However, If I make zram support migratepages, I will use __GFP_MOVABLE. So, I'm not sure there is any special driver that it can support migrate via migratepage but it doesn't set __GFP_MOVABLE. Having said that, I support your opinion because __GFP_MOVABLE is not only gfp mask for allocating so we should take care of complete gfp mask from original page. > > So what I would think (without knowing all details) that the page > owner info should be transferred during page migration with all the > other flags, and shouldn't concern __isolate_free_page() at all? > I agree. Thanks. -- 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>