On Fri, May 06, 2011 at 07:32:46PM +0800, Figo.zhang wrote: > > in isolate_migratepages() have check page in LRU twice, the next one > at _isolate_lru_page(). hugetlbfs or any other compound page won't have PageLRU set and they may go away from under us leading to compound_order not being reliable if we remove the PageLRU check before compound_order. So we need to verify the page is in LRU before running compound_order safely. And if we hold the lru_lock, the page won't be isolated under us, and we know it's not going to get splitted either. We might use compound_trans_order but that's only reliable if run on the head page so it's not so reliable, and so far it's only used by memory-failure to "diminish" the risk of races in reading the compound order, but it's not the best having to use compound_trans_order (and memory-failure remains unsafe w.r.t to hugetlbfs being released during hwpoisoning, so compound_trans_order might have to be improved for it). -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>