[PATCH] rmap 30 fix bad mapcount

From: Hugh Dickins <hugh@veritas.com>

From: Andrea Arcangeli <andrea@suse.de>

page_alloc.c's bad_page routine should reset a bad mapcount; and it's more
revealing to show the bad mapcount than just the boolean mapped.

mm/page_alloc.c

@@ -73,9 +73,9 @@ static void bad_page(const char *function, struct page *page)
 {
 	printk(KERN_EMERG "Bad page state at %s (in process '%s', page %p)\n",
 		function, current->comm, page);
-	printk(KERN_EMERG "flags:0x%08lx mapping:%p mapped:%d count:%d\n",
+	printk(KERN_EMERG "flags:0x%08lx mapping:%p mapcount:%d count:%d\n",
 		(unsigned long)page->flags, page->mapping,
-		page_mapped(page), page_count(page));
+		(int)page->mapcount, page_count(page));
 	printk(KERN_EMERG "Backtrace:\n");
 	dump_stack();
 	printk(KERN_EMERG "Trying to fix it up, but a reboot is needed\n");
@@ -90,6 +90,7 @@ static void bad_page(const char *function, struct page *page)
 			1 << PG_writeback);
 	set_page_count(page, 0);
 	page->mapping = NULL;
+	page->mapcount = 0;
 }
 
 #ifndef CONFIG_HUGETLB_PAGE