From de426dbe9a60706b91b40397f69f819a39a06b6b Mon Sep 17 00:00:00 2001 From: Minchan Kim Date: Thu, 13 Sep 2012 10:59:00 +1000 Subject: [PATCH] memory-hotplug: bug fix race between isolation and allocation Like below, memory-hotplug makes race between page-isolation and page-allocation so it can hit BUG_ON in __offline_isolated_pages. CPU A CPU B start_isolate_page_range set_migratetype_isolate spin_lock_irqsave(zone->lock) free_hot_cold_page(Page A) /* without zone->lock */ migratetype = get_pageblock_migratetype(Page A); /* * Page could be moved into MIGRATE_MOVABLE * of per_cpu_pages */ list_add_tail(&page->lru, &pcp->lists[migratetype]); set_pageblock_isolate move_freepages_block drain_all_pages /* Page A could be in MIGRATE_MOVABLE of free_list. */ check_pages_isolated __test_page_isolated_in_pageblock /* * We can't catch freed page which * is free_list[MIGRATE_MOVABLE] */ if (PageBuddy(page A)) pfn += 1 << page_order(page A); /* So, Page A could be allocated */ __offline_isolated_pages /* * BUG_ON hit or offline page * which is used by someone */ BUG_ON(!PageBuddy(page A)); This patch checks page's migratetype in freelist in __test_page_isolated_in_pageblock. So now __test_page_isolated_in_pageblock can check the page caused by above race and can fail of memory offlining. Signed-off-by: Minchan Kim Acked-by: KAMEZAWA Hiroyuki Reviewed-by: Yasuaki Ishimatsu Acked-by: Mel Gorman Cc: Xishi Qiu Cc: Wen Congyang Signed-off-by: Andrew Morton --- mm/page_isolation.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/page_isolation.c b/mm/page_isolation.c index 87a7929acf7b..7ba740551d8c 100644 --- a/mm/page_isolation.c +++ b/mm/page_isolation.c @@ -193,8 +193,11 @@ __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn) continue; } page = pfn_to_page(pfn); - if (PageBuddy(page)) + if (PageBuddy(page)) { + if (get_freepage_migratetype(page) != MIGRATE_ISOLATE) + break; pfn += 1 << page_order(page); + } else if (page_count(page) == 0 && get_freepage_migratetype(page) == MIGRATE_ISOLATE) pfn += 1; -- 2.39.5