sparsemem: ensure we initialise the node mapping for SPARSEMEM_STATIC

Booting SPARSEMEM on NUMA systems trips a BUG in page_alloc.c:

	Initializing HighMem for node 0 (00038000:00100000)
	Initializing HighMem for node 1 (00100000:001ffe00)
	------------[ cut here ]------------
	kernel BUG at /home/apw/git/linux-2.6/mm/page_alloc.c:456!
	[...]

This occurs because the section to node id mapping is not being
setup correctly during init under SPARSEMEM_STATIC, leading to an
attempt to free pages from all nodes into the zones on node 0.

When the zone_table[] was removed in the following commit, a new
section to node mapping table was introduced:

    commit 89689ae7f95995723fbcd5c116c47933a3bb8b13
    [PATCH] Get rid of zone_table[]

That conversion inadvertantly only initialised the node mapping in
SPARSEMEM_EXTREME.  Ensure we initialise the node mapping in
SPARSEMEM_STATIC.

[akpm@linux-foundation.org: make the stubs static inline]
Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Cc: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/sparse.c

@@ -41,6 +41,15 @@ int page_to_nid(struct page *page)
 	return section_to_node_table[page_to_section(page)];
 }
 EXPORT_SYMBOL(page_to_nid);
+
+static void set_section_nid(unsigned long section_nr, int nid)
+{
+	section_to_node_table[section_nr] = nid;
+}
+#else /* !NODE_NOT_IN_PAGE_FLAGS */
+static inline void set_section_nid(unsigned long section_nr, int nid)
+{
+}
 #endif
 
 #ifdef CONFIG_SPARSEMEM_EXTREME
@@ -68,10 +77,6 @@ static int __meminit sparse_index_init(unsigned long section_nr, int nid)
 	struct mem_section *section;
 	int ret = 0;
 
-#ifdef NODE_NOT_IN_PAGE_FLAGS
-	section_to_node_table[section_nr] = nid;
-#endif
-
 	if (mem_section[root])
 		return -EEXIST;
 
@@ -148,6 +153,7 @@ void __init memory_present(int nid, unsigned long start, unsigned long end)
 		struct mem_section *ms;
 
 		sparse_index_init(section, nid);
+		set_section_nid(section, nid);
 
 		ms = __nr_to_section(section);
 		if (!ms->section_mem_map)