X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=mm%2Fpage_alloc.c;h=d73bfad1c32f2e2254aaa1f47de3bda7db0b8b88;hb=cf03613e9662c28372b8c83538fb402df37c53f5;hp=4ffed1cd158b5a9731d90b2e870de3b42feec38a;hpb=cae2f9c46d69edb1aee565917735d79aba3a3267;p=linux-2.6

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 4ffed1cd15..d73bfad1c3 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -847,8 +847,19 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order,
 		struct page *page = __rmqueue(zone, order, migratetype);
 		if (unlikely(page == NULL))
 			break;
+
+		/*
+		 * Split buddy pages returned by expand() are received here
+		 * in physical page order. The page is added to the callers and
+		 * list and the list head then moves forward. From the callers
+		 * perspective, the linked list is ordered by page number in
+		 * some conditions. This is useful for IO devices that can
+		 * merge IO requests if the physical pages are ordered
+		 * properly.
+		 */
 		list_add(&page->lru, list);
 		set_page_private(page, migratetype);
+		list = &page->lru;
 	}
 	spin_unlock(&zone->lock);
 	return i;
@@ -3265,6 +3276,16 @@ static void inline setup_usemap(struct pglist_data *pgdat,
 #endif /* CONFIG_SPARSEMEM */
 
 #ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE
+
+/* Return a sensible default order for the pageblock size. */
+static inline int pageblock_default_order(void)
+{
+	if (HPAGE_SHIFT > PAGE_SHIFT)
+		return HUGETLB_PAGE_ORDER;
+
+	return MAX_ORDER-1;
+}
+
 /* Initialise the number of pages represented by NR_PAGEBLOCK_BITS */
 static inline void __init set_pageblock_order(unsigned int order)
 {
@@ -3280,7 +3301,16 @@ static inline void __init set_pageblock_order(unsigned int order)
 }
 #else /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */
 
-/* Defined this way to avoid accidently referencing HUGETLB_PAGE_ORDER */
+/*
+ * When CONFIG_HUGETLB_PAGE_SIZE_VARIABLE is not set, set_pageblock_order()
+ * and pageblock_default_order() are unused as pageblock_order is set
+ * at compile-time. See include/linux/pageblock-flags.h for the values of
+ * pageblock_order based on the kernel config
+ */
+static inline int pageblock_default_order(unsigned int order)
+{
+	return MAX_ORDER-1;
+}
 #define set_pageblock_order(x)	do {} while (0)
 
 #endif /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */
@@ -3365,7 +3395,7 @@ static void __meminit free_area_init_core(struct pglist_data *pgdat,
 		if (!size)
 			continue;
 
-		set_pageblock_order(HUGETLB_PAGE_ORDER);
+		set_pageblock_order(pageblock_default_order());
 		setup_usemap(pgdat, zone, size);
 		ret = init_currently_empty_zone(zone, zone_start_pfn,
 						size, MEMMAP_EARLY);