4 files changed, 49 insertions, 37 deletions

diff --git a/arch/i386/Kconfig b/arch/i386/Kconfig
index 619d843ba231..dcb0ad098c60 100644
--- a/arch/i386/Kconfig
+++ b/arch/i386/Kconfig
@@ -754,6 +754,7 @@ config NUMA
         depends on SMP && HIGHMEM64G && (X86_NUMAQ || X86_GENERICARCH || (X86_SUMMIT && ACPI))
         default n if X86_PC
         default y if (X86_NUMAQ || X86_SUMMIT)
+        select SPARSEMEM_STATIC
 
 # Need comments to help the hapless user trying to turn on NUMA support
 comment "NUMA (NUMA-Q) requires SMP, 64GB highmem support"
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index b97054bbc394..79cf578e21b9 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -487,39 +487,29 @@ 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)
+#ifdef CONFIG_SPARSEMEM_EXTREME
+#define SECTIONS_PER_ROOT       (PAGE_SIZE / sizeof (struct mem_section))
+#else
+#define SECTIONS_PER_ROOT       1
+#endif
 
-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];
-}
+#define SECTION_NR_TO_ROOT(sec) ((sec) / SECTIONS_PER_ROOT)
+#define NR_SECTION_ROOTS        (NR_MEM_SECTIONS / SECTIONS_PER_ROOT)
+#define SECTION_ROOT_MASK       (SECTIONS_PER_ROOT - 1)
 
+#ifdef CONFIG_SPARSEMEM_EXTREME
+extern struct mem_section *mem_section[NR_SECTION_ROOTS];
 #else
-
-extern struct mem_section mem_section[NR_MEM_SECTIONS];
+extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT];
+#endif
 
 static inline struct mem_section *__nr_to_section(unsigned long nr)
 {
-        return &mem_section[nr];
+        if (!mem_section[SECTION_NR_TO_ROOT(nr)])
+                return NULL;
+        return &mem_section[SECTION_NR_TO_ROOT(nr)][nr & SECTION_ROOT_MASK];
 }
 
-#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
diff --git a/mm/Kconfig b/mm/Kconfig
index fc644c5c065d..4e9937ac3529 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -91,10 +91,23 @@ config HAVE_MEMORY_PRESENT
         depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM
 
 #
+# SPARSEMEM_EXTREME (which is the default) does some bootmem
+# allocations when memory_present() is called.  If this can not
+# be done on your architecture, select this option.  However,
+# statically allocating the mem_section[] array can potentially
+# consume vast quantities of .bss, so be careful.
+#
+# This option will also potentially produce smaller runtime code
+# with gcc 3.4 and later.
+#
+config SPARSEMEM_STATIC
+        def_bool n
+
+#
 # 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
+config SPARSEMEM_EXTREME
+        def_bool y
+        depends on SPARSEMEM && !SPARSEMEM_STATIC
diff --git a/mm/sparse.c b/mm/sparse.c
index b2b456bf0a5d..fa01292157a9 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -13,28 +13,36 @@
  *
  * 1) mem_section       - memory sections, mem_map's for valid memory
  */
-#ifdef CONFIG_ARCH_SPARSEMEM_EXTREME
+#ifdef CONFIG_SPARSEMEM_EXTREME
 struct mem_section *mem_section[NR_SECTION_ROOTS]
         ____cacheline_maxaligned_in_smp;
+#else
+struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT]
+        ____cacheline_maxaligned_in_smp;
+#endif
+EXPORT_SYMBOL(mem_section);
+
+static void sparse_alloc_root(unsigned long root, int nid)
+{
+#ifdef CONFIG_SPARSEMEM_EXTREME
+        mem_section[root] = alloc_bootmem_node(NODE_DATA(nid), PAGE_SIZE);
+#endif
+}
 
 static void sparse_index_init(unsigned long section, int nid)
 {
-        unsigned long root = SECTION_TO_ROOT(section);
+        unsigned long root = SECTION_NR_TO_ROOT(section);
 
         if (mem_section[root])
                 return;
-        mem_section[root] = alloc_bootmem_node(NODE_DATA(nid), PAGE_SIZE);
+
+        sparse_alloc_root(root, nid);
+
         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. */
 void memory_present(int nid, unsigned long start, unsigned long end)
 {