From a6fc86d2b43bf1086557f023a24adf91db915559 Mon Sep 17 00:00:00 2001
From: Petr Holasek <pholasek@redhat.com>
Date: Wed, 12 Jan 2011 17:00:34 -0800
Subject: kpagecount: add slab page checking because _mapcount is in a union

Add a PageSlab() check before adding the _mapcount value to /kpagecount.
page->_mapcount is in a union with the SLAB structure so for pages
controlled by SLAB, page_mapcount() returns nonsense.

Signed-off-by: Petr Holasek <pholasek@redhat.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/proc/page.c b/fs/proc/page.c
index 3b8b456..b06c674 100644
--- a/fs/proc/page.c
+++ b/fs/proc/page.c
@@ -40,7 +40,7 @@ static ssize_t kpagecount_read(struct file *file, char __user *buf,
 			ppage = pfn_to_page(pfn);
 		else
 			ppage = NULL;
-		if (!ppage)
+		if (!ppage || PageSlab(ppage))
 			pcount = 0;
 		else
 			pcount = page_mapcount(ppage);
-- 
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