Most free pages in the buddy system have no PG_buddy set. Introduce is_free_buddy_page() for detecting them reliably. CC: Andi Kleen CC: Nick Piggin CC: Mel Gorman Signed-off-by: Wu Fengguang --- mm/internal.h | 3 +++ mm/memory-failure.c | 9 +++++++-- mm/page_alloc.c | 21 +++++++++++++++++++++ 3 files changed, 31 insertions(+), 2 deletions(-) --- linux-mm.orig/mm/memory-failure.c 2009-11-30 20:04:51.000000000 +0800 +++ linux-mm/mm/memory-failure.c 2009-11-30 20:06:00.000000000 +0800 @@ -783,8 +783,13 @@ int __memory_failure(unsigned long pfn, * that may make page_freeze_refs()/page_unfreeze_refs() mismatch. */ if (!ref && !get_page_unless_zero(compound_head(p))) { - action_result(pfn, "free or high order kernel", IGNORED); - return PageBuddy(compound_head(p)) ? 0 : -EBUSY; + if (is_free_buddy_page(p)) { + action_result(pfn, "free buddy", DELAYED); + return 0; + } else { + action_result(pfn, "high order kernel", IGNORED); + return -EBUSY; + } } /* --- linux-mm.orig/mm/internal.h 2009-11-30 11:08:34.000000000 +0800 +++ linux-mm/mm/internal.h 2009-11-30 20:06:01.000000000 +0800 @@ -50,6 +50,9 @@ extern void putback_lru_page(struct page */ extern void __free_pages_bootmem(struct page *page, unsigned int order); extern void prep_compound_page(struct page *page, unsigned long order); +#ifdef CONFIG_MEMORY_FAILURE +extern bool is_free_buddy_page(struct page *page); +#endif /* --- linux-mm.orig/mm/page_alloc.c 2009-11-30 11:08:34.000000000 +0800 +++ linux-mm/mm/page_alloc.c 2009-11-30 20:06:01.000000000 +0800 @@ -5085,3 +5085,24 @@ __offline_isolated_pages(unsigned long s spin_unlock_irqrestore(&zone->lock, flags); } #endif + +#ifdef CONFIG_MEMORY_FAILURE +bool is_free_buddy_page(struct page *page) +{ + struct zone *zone = page_zone(page); + unsigned long pfn = page_to_pfn(page); + unsigned long flags; + int order; + + spin_lock_irqsave(&zone->lock, flags); + for (order = 0; order < MAX_ORDER; order++) { + struct page *page_head = page - (pfn & ((1 << order) - 1)); + + if (PageBuddy(page_head) && page_order(page_head) >= order) + break; + } + spin_unlock_irqrestore(&zone->lock, flags); + + return order < MAX_ORDER; +} +#endif -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/