HWPOISON: detect free buddy pages explicitly
Wu Fengguang [Wed, 16 Dec 2009 11:19:58 +0000 (12:19 +0100)]
Most free pages in the buddy system have no PG_buddy set.
Introduce is_free_buddy_page() for detecting them reliably.

CC: Nick Piggin <npiggin@suse.de>
CC: Mel Gorman <mel@linux.vnet.ibm.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

mm/internal.h
mm/memory-failure.c
mm/page_alloc.c

index 4fe67a1..49b2ff7 100644 (file)
@@ -50,6 +50,9 @@ extern void putback_lru_page(struct page *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
 
 
 /*
index 676ab39..5055b94 100644 (file)
@@ -807,8 +807,13 @@ int __memory_failure(unsigned long pfn, int trapno, int flags)
         */
        if (!(flags & MF_COUNT_INCREASED) &&
                !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;
+               }
        }
 
        /*
index 59d2e88..6867b4d 100644 (file)
@@ -5081,3 +5081,24 @@ __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
        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