1 files changed, 28 insertions, 2 deletions

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 6c90461ed99f..b97054bbc394 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -487,6 +487,28 @@ struct mem_section {
         unsigned long section_mem_map;
 };
 
+#ifdef CONFIG_ARCH_SPARSEMEM_EXTREME
+/*
+ * Should we ever require GCC 4 or later then the flat array scheme
+ * can be eliminated and a uniform solution for EXTREME and !EXTREME can
+ * be arrived at.
+ */
+#define SECTION_ROOT_SHIFT      (PAGE_SHIFT-3)
+#define SECTION_ROOT_MASK       ((1UL<<SECTION_ROOT_SHIFT) - 1)
+#define SECTION_TO_ROOT(_sec)   ((_sec) >> SECTION_ROOT_SHIFT)
+#define NR_SECTION_ROOTS        (NR_MEM_SECTIONS >>  SECTION_ROOT_SHIFT)
+
+extern struct mem_section *mem_section[NR_SECTION_ROOTS];
+
+static inline struct mem_section *__nr_to_section(unsigned long nr)
+{
+        if (!mem_section[SECTION_TO_ROOT(nr)])
+                return NULL;
+        return &mem_section[SECTION_TO_ROOT(nr)][nr & SECTION_ROOT_MASK];
+}
+
+#else
+
 extern struct mem_section mem_section[NR_MEM_SECTIONS];
 
 static inline struct mem_section *__nr_to_section(unsigned long nr)
@@ -494,6 +516,10 @@ static inline struct mem_section *__nr_to_section(unsigned long nr)
         return &mem_section[nr];
 }
 
+#define sparse_index_init(_sec, _nid)  do {} while (0)
+
+#endif
+
 /*
  * We use the lower bits of the mem_map pointer to store
  * a little bit of information.  There should be at least
@@ -513,12 +539,12 @@ static inline struct page *__section_mem_map_addr(struct mem_section *section)
 
 static inline int valid_section(struct mem_section *section)
 {
-        return (section->section_mem_map & SECTION_MARKED_PRESENT);
+        return (section && (section->section_mem_map & SECTION_MARKED_PRESENT));
 }
 
 static inline int section_has_mem_map(struct mem_section *section)
 {
-        return (section->section_mem_map & SECTION_HAS_MEM_MAP);
+        return (section && (section->section_mem_map & SECTION_HAS_MEM_MAP));
 }
 
 static inline int valid_section_nr(unsigned long nr)