mm: numa: Copy cpupid on page migration

After page migration, the new page has the nidpid unset. This makes
every fault on a recently migrated page look like a first numa fault,
leading to another page migration.

Copying over the nidpid at page migration time should prevent erroneous
migrations of recently migrated pages.
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1381141781-10992-46-git-send-email-mgorman@suse.deSigned-off-by: Ingo Molnar <mingo@kernel.org>

mm/migrate.c

@@ -443,6 +443,8 @@ int migrate_huge_page_move_mapping(struct address_space *mapping,
  */
 void migrate_page_copy(struct page *newpage, struct page *page)
 {
+	int cpupid;
+
 	if (PageHuge(page) || PageTransHuge(page))
 		copy_huge_page(newpage, page);
 	else
@@ -479,6 +481,13 @@ void migrate_page_copy(struct page *newpage, struct page *page)
 			__set_page_dirty_nobuffers(newpage);
  	}
 
+	/*
+	 * Copy NUMA information to the new page, to prevent over-eager
+	 * future migrations of this same page.
+	 */
+	cpupid = page_cpupid_xchg_last(page, -1);
+	page_cpupid_xchg_last(newpage, cpupid);
+
 	mlock_migrate_page(newpage, page);
 	ksm_migrate_page(newpage, page);
 	/*