2 files changed, 41 insertions, 6 deletions

diff --git a/mm/Kconfig b/mm/Kconfig
index cd379936cac6..fc644c5c065d 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -89,3 +89,12 @@ config NEED_MULTIPLE_NODES
 config HAVE_MEMORY_PRESENT
         def_bool y
         depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM
+
+#
+# Architectecture platforms which require a two level mem_section in SPARSEMEM
+# must select this option. This is usually for architecture platforms with
+# an extremely sparse physical address space.
+#
+config ARCH_SPARSEMEM_EXTREME
+        def_bool n
+        depends on SPARSEMEM && 64BIT
diff --git a/mm/sparse.c b/mm/sparse.c
index b54e304df4a7..b2b456bf0a5d 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -13,7 +13,26 @@
  *
  * 1) mem_section       - memory sections, mem_map's for valid memory
  */
-struct mem_section mem_section[NR_MEM_SECTIONS];
+#ifdef CONFIG_ARCH_SPARSEMEM_EXTREME
+struct mem_section *mem_section[NR_SECTION_ROOTS]
+        ____cacheline_maxaligned_in_smp;
+
+static void sparse_index_init(unsigned long section, int nid)
+{
+        unsigned long root = SECTION_TO_ROOT(section);
+
+        if (mem_section[root])
+                return;
+        mem_section[root] = alloc_bootmem_node(NODE_DATA(nid), PAGE_SIZE);
+        if (mem_section[root])
+                memset(mem_section[root], 0, PAGE_SIZE);
+        else
+                panic("memory_present: NO MEMORY\n");
+}
+#else
+struct mem_section mem_section[NR_MEM_SECTIONS]
+        ____cacheline_maxaligned_in_smp;
+#endif
 EXPORT_SYMBOL(mem_section);
 
 /* Record a memory area against a node. */
@@ -24,8 +43,13 @@ void memory_present(int nid, unsigned long start, unsigned long end)
         start &= PAGE_SECTION_MASK;
         for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION) {
                 unsigned long section = pfn_to_section_nr(pfn);
-                if (!mem_section[section].section_mem_map)
-                        mem_section[section].section_mem_map = SECTION_MARKED_PRESENT;
+                struct mem_section *ms;
+
+                sparse_index_init(section, nid);
+
+                ms = __nr_to_section(section);
+                if (!ms->section_mem_map)
+                        ms->section_mem_map = SECTION_MARKED_PRESENT;
         }
 }
 
@@ -85,6 +109,7 @@ static struct page *sparse_early_mem_map_alloc(unsigned long pnum)
 {
         struct page *map;
         int nid = early_pfn_to_nid(section_nr_to_pfn(pnum));
+        struct mem_section *ms = __nr_to_section(pnum);
 
         map = alloc_remap(nid, sizeof(struct page) * PAGES_PER_SECTION);
         if (map)
@@ -96,7 +121,7 @@ static struct page *sparse_early_mem_map_alloc(unsigned long pnum)
                 return map;
 
         printk(KERN_WARNING "%s: allocation failed\n", __FUNCTION__);
-        mem_section[pnum].section_mem_map = 0;
+        ms->section_mem_map = 0;
         return NULL;
 }
 
@@ -114,8 +139,9 @@ void sparse_init(void)
                         continue;
 
                 map = sparse_early_mem_map_alloc(pnum);
-                if (map)
-                        sparse_init_one_section(&mem_section[pnum], pnum, map);
+                if (!map)
+                        continue;
+                sparse_init_one_section(__nr_to_section(pnum), pnum, map);
         }
 }