mm: print more details for bad_page()

bad_page() is cool in that it prints out a bunch of data about the page.
But, I can never remember which page flags are good and which are bad,
or whether ->index or ->mapping is required to be NULL.

This patch allows bad/dump_page() callers to specify a string about why
they are dumping the page and adds explanation strings to a number of
places.  It also adds a 'bad_flags' argument to bad_page(), which it
then dumps out separately from the flags which are actually set.

This way, the messages will show specifically why the page was bad,
*specifically* which flags it is complaining about, if it was a page
flag combination which was the problem.

[akpm@linux-foundation.org: switch to pr_alert]
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Christoph Lameter <cl@linux.com>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/balloon_compaction.c

@@ -267,7 +267,7 @@ void balloon_page_putback(struct page *page)
 		put_page(page);
 	} else {
 		WARN_ON(1);
-		dump_page(page);
+		dump_page(page, "not movable balloon page");
 	}
 	unlock_page(page);
 }
@@ -287,7 +287,7 @@ int balloon_page_migrate(struct page *newpage,
 	BUG_ON(!trylock_page(newpage));
 
 	if (WARN_ON(!__is_movable_balloon_page(page))) {
-		dump_page(page);
+		dump_page(page, "not movable balloon page");
 		unlock_page(newpage);
 		return rc;
 	}