On Fri, Jun 03, 2011 at 05:59:13AM +0900, Minchan Kim wrote: > Now that I look code more, it would meet VM_BUG_ON of get_page if the page is really > freed. I think if we hold zone->lock to prevent prep_new_page racing, it would be okay. There would be problems with split_huge_page too, we can't even use get_page_unless_zero unless it's a lru page and we hold the lru_lock and that's an hot lock too. > But it's rather overkill so I will add my sign to your patch if we don't have better idea > until tomorrow. :) Things like compound_trans_head are made to protect against split_huge_page like in ksm, not exactly to get to the head page when the page is being freed, so it's a little tricky. If we could get to the head page safe starting from a tail page it'd solve some issues for memory-failure too, which is currently using compound_head unsafe too, but at least that's running after a catastrophic hardware failure so the safer the better but the little race is unlikely to ever be an issue for memory-failure (and it's same issue for hugetlbfs and slub order 3). -- 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>