mm: introduce dump_page() and print symbolic flag names

- introduce dump_page() to print the page info for debugging some error
  condition.

- convert three mm users: bad_page(), print_bad_pte() and memory offline
  failure.

- print an extra field: the symbolic names of page->flags

Example dump_page() output:

[  157.521694] page:ffffea0000a7cba8 count:2 mapcount:1 mapping:ffff88001c901791 index:0x147
[  157.525570] page flags: 0x100000000100068(uptodate|lru|active|swapbacked)

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alex Chiang <achiang@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Mel Gorman <mel@linux.vnet.ibm.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memory_hotplug.c

@@ -688,9 +688,9 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 			if (page_count(page))
 				not_managed++;
 #ifdef CONFIG_DEBUG_VM
-			printk(KERN_INFO "removing from LRU failed"
-					 " %lx/%d/%lx\n",
-				pfn, page_count(page), page->flags);
+			printk(KERN_ALERT "removing pfn %lx from LRU failed\n",
+			       pfn);
+			dump_page(page);
 #endif
 		}
 	}