mm: numa: Account for failed allocations and isolations as migration failures

Subject says it all. Allocation failures and a failure to isolate should
be accounted as a migration failure. This is partially another
difference between base page and transhuge page migration. A base page
migration makes multiple attempts for these conditions before it would
be accounted for as a failure.
Signed-off-by: Mel Gorman <mgorman@suse.de>

mm/migrate.c

@@ -1635,12 +1635,15 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm,
 
 	new_page = alloc_pages_node(node,
 		(GFP_TRANSHUGE | GFP_THISNODE) & ~__GFP_WAIT, HPAGE_PMD_ORDER);
-	if (!new_page)
+	if (!new_page) {
+		count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
 		goto out_dropref;
+	}
 	page_xchg_last_nid(new_page, page_last_nid(page));
 
 	isolated = numamigrate_isolate_page(pgdat, page);
 	if (!isolated) {
+		count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
 		put_page(new_page);
 		goto out_keep_locked;
 	}