[PATCH] sparsemem: record nid during memory present

Record the node id as we mark sections for instantiation.  Use this nid
during instantiation to direct allocations.
Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Cc: Mike Kravetz <kravetz@us.ibm.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Bob Picco <bob.picco@hp.com>
Cc: Jack Steiner <steiner@sgi.com>
Cc: Yasunori Goto <y-goto@jp.fujitsu.com>
Cc: Martin Bligh <mbligh@google.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/mmzone.h

@@ -509,6 +509,10 @@ struct mem_section {
 	 * pages.  However, it is stored with some other magic.
 	 * (see sparse.c::sparse_init_one_section())
 	 *
+	 * Additionally during early boot we encode node id of
+	 * the location of the section here to guide allocation.
+	 * (see sparse.c::memory_present())
+	 *
 	 * Making it a UL at least makes someone do a cast
 	 * before using it wrong.
 	 */
@@ -548,6 +552,7 @@ extern int __section_nr(struct mem_section* ms);
 #define SECTION_HAS_MEM_MAP	(1UL<<1)
 #define SECTION_MAP_LAST_BIT	(1UL<<2)
 #define SECTION_MAP_MASK	(~(SECTION_MAP_LAST_BIT-1))
+#define SECTION_NID_SHIFT	2
 
 static inline struct page *__section_mem_map_addr(struct mem_section *section)
 {

mm/sparse.c

@@ -99,6 +99,22 @@ int __section_nr(struct mem_section* ms)
 	return (root_nr * SECTIONS_PER_ROOT) + (ms - root);
 }
 
+/*
+ * During early boot, before section_mem_map is used for an actual
+ * mem_map, we use section_mem_map to store the section's NUMA
+ * node.  This keeps us from having to use another data structure.  The
+ * node information is cleared just before we store the real mem_map.
+ */
+static inline unsigned long sparse_encode_early_nid(int nid)
+{
+	return (nid << SECTION_NID_SHIFT);
+}
+
+static inline int sparse_early_nid(struct mem_section *section)
+{
+	return (section->section_mem_map >> SECTION_NID_SHIFT);
+}
+
 /* Record a memory area against a node. */
 void memory_present(int nid, unsigned long start, unsigned long end)
 {
@@ -113,7 +129,8 @@ void memory_present(int nid, unsigned long start, unsigned long end)
 
 		ms = __nr_to_section(section);
 		if (!ms->section_mem_map)
-			ms->section_mem_map = SECTION_MARKED_PRESENT;
+			ms->section_mem_map = sparse_encode_early_nid(nid) |
+							SECTION_MARKED_PRESENT;
 	}
 }
 
@@ -164,6 +181,7 @@ static int sparse_init_one_section(struct mem_section *ms,
 	if (!valid_section(ms))
 		return -EINVAL;
 
+	ms->section_mem_map &= ~SECTION_MAP_MASK;
 	ms->section_mem_map |= sparse_encode_mem_map(mem_map, pnum);
 
 	return 1;
@@ -172,8 +190,8 @@ static int sparse_init_one_section(struct mem_section *ms,
 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);
+	int nid = sparse_early_nid(ms);
 
 	map = alloc_remap(nid, sizeof(struct page) * PAGES_PER_SECTION);
 	if (map)