mm, vmstat: skip reporting offline pages in pagetypeinfo

pagetypeinfo_showblockcount_print skips over invalid pfns but it would
report pages which are offline because those have a valid pfn.  Their
migrate type is misleading at best.

Now that we have pfn_to_online_page() we can use it instead of
pfn_valid() and fix this.

[[email protected]: fix build]
  Link: http://lkml.kernel.org/r/[email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Michal Hocko <[email protected]>
Reported-by: Joonsoo Kim <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Balbir Singh <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Daniel Kiper <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Igor Mammedov <[email protected]>
Cc: Jerome Glisse <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Reza Arbab <[email protected]>
Cc: Tobias Regnery <[email protected]>
Cc: Toshi Kani <[email protected]>
Cc: Vitaly Kuznetsov <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Xishi Qiu <[email protected]>
Cc: Yasuaki Ishimatsu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: Michal Hocko

mm/vmstat.c

@@ -1223,11 +1223,10 @@ static void pagetypeinfo_showblockcount_print(struct seq_file *m,
 	for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
 		struct page *page;
 
-		if (!pfn_valid(pfn))
+		page = pfn_to_online_page(pfn);
+		if (!page)
 			continue;
 
-		page = pfn_to_page(pfn);
-
 		/* Watch for unexpected holes punched in the memmap */
 		if (!memmap_valid_within(pfn, page, zone))
 			continue;