[PATCH_FOR_REVIEW 2.6.12-rc1 2/3] mm: manual page migration-rc1 -- add node_map arg to try_to_migrate_pages()

[Ray Bryant <raybry@sgi.com>]

This patch changes the interface to try_to_migrate_pages() so that one
can specify the nodes where the pages are to be migrated to.  This is
done by adding a "node_map" argument to try_to_migrate_pages(), node_map
is of type "short *".

If this argument is NULL, then try_to_migrate_pages() behaves exactly
as before and this is the interface the rest of the memory hotplug
patch should use.  (Note:  This patchset does not include the changes
for the rest of the memory hotplug patch that will be necessary to use
this new interface [if it is accepted].  Those chagnes will be provided
as a distinct patch.)

If the argument is non-NULL, the node_map points at an array of shorts
of size MAX_NUMNODES.   node_map[N] is either the id of an online node
or -1.  If node_map[N] >=0 then pages found in the page list passed
to try_to_migrate_pages() that are found on node N are migrated to node
node_map[N].  if node_map[N] == -1, then pages found on node N are left
where they are.

This change depends on previous changes to migrate_onepage()
that support migrating a page to a specified node.  These changes 
are already part of the memory migration sub-patch of the memory
hotplug patch.

Signed-off-by:  Ray Bryant <raybry@sgi.com>

Index: linux-2.6.12-rc1-mhp3-page-migration/include/linux/mmigrate.h
===================================================================
--- linux-2.6.12-rc1-mhp3-page-migration.orig/include/linux/mmigrate.h	2005-03-28 22:10:27.000000000 -0800
+++ linux-2.6.12-rc1-mhp3-page-migration/include/linux/mmigrate.h	2005-03-28 22:20:37.000000000 -0800
@@ -16,7 +16,23 @@ extern int migrate_page_buffer(struct pa
 extern int page_migratable(struct page *, struct page *, int,
 					struct list_head *);
 extern struct page * migrate_onepage(struct page *, int nodeid);
-extern int try_to_migrate_pages(struct list_head *);
+extern int try_to_migrate_pages(struct list_head *, short *);
+
+#ifdef CONFIG_NUMA
+static inline struct page *node_migrate_onepage(struct page *page, short *node_map) 
+{
+	if (node_map)
+		return migrate_onepage(page, node_map[page_to_nid(page)]);
+	else
+		return migrate_onepage(page, MIGRATE_NODE_ANY); 
+		
+}
+#else
+static inline struct page *node_migrate_onepage(struct page *page, short *node_map) 
+{
+	return migrate_onepage(page, MIGRATE_NODE_ANY); 
+}
+#endif
 
 #else
 static inline int generic_migrate_page(struct page *page, struct page *newpage,
Index: linux-2.6.12-rc1-mhp3-page-migration/mm/mmigrate.c
===================================================================
--- linux-2.6.12-rc1-mhp3-page-migration.orig/mm/mmigrate.c	2005-03-28 22:10:25.000000000 -0800
+++ linux-2.6.12-rc1-mhp3-page-migration/mm/mmigrate.c	2005-03-28 22:20:18.000000000 -0800
@@ -501,9 +501,11 @@ out_unlock:
 /*
  * This is the main entry point to migrate pages in a specific region.
  * If a page is inactive, the page may be just released instead of
- * migration.
+ * migration.  node_map is supplied in those cases (on NUMA systems)
+ * where the caller wishes to specify to which nodes the pages are
+ * migrated.  If node_map is null, the target node is MIGRATE_NODE_ANY.
  */
-int try_to_migrate_pages(struct list_head *page_list)
+int try_to_migrate_pages(struct list_head *page_list, short *node_map)
 {
 	struct page *page, *page2, *newpage;
 	LIST_HEAD(pass1_list);
@@ -541,7 +543,7 @@ int try_to_migrate_pages(struct list_hea
 	list_for_each_entry_safe(page, page2, &pass1_list, lru) {
 		list_del(&page->lru);
 		if (PageLocked(page) || PageWriteback(page) ||
-		    IS_ERR(newpage = migrate_onepage(page, MIGRATE_NODE_ANY))) {
+		    IS_ERR(newpage = node_migrate_onepage(page, node_map))) {
 			if (page_count(page) == 1) {
 				/* the page is already unused */
 				putback_page_to_lru(page_zone(page), page);
@@ -559,7 +561,7 @@ int try_to_migrate_pages(struct list_hea
 	 */
 	list_for_each_entry_safe(page, page2, &pass2_list, lru) {
 		list_del(&page->lru);
-		if (IS_ERR(newpage = migrate_onepage(page, MIGRATE_NODE_ANY))) {
+		if (IS_ERR(newpage = node_migrate_onepage(page, node_map))) {
 			if (page_count(page) == 1) {
 				/* the page is already unused */
 				putback_page_to_lru(page_zone(page), page);

-- 
Best Regards,
Ray
-----------------------------------------------
Ray Bryant                       raybry@sgi.com
The box said: "Requires Windows 98 or better",
           so I installed Linux.
-----------------------------------------------
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