From 1d148e218a0d0566b1c06f2f45f1436d53b049b2 Mon Sep 17 00:00:00 2001
From: "Wang, Yalin" <Yalin.Wang@sonymobile.com>
Date: Wed, 11 Feb 2015 15:24:48 -0800
Subject: [PATCH] mm: add VM_BUG_ON_PAGE() to page_mapcount()

Add VM_BUG_ON_PAGE() for slab pages.  _mapcount is an union with slab
struct in struct page, so we must avoid accessing _mapcount if this page
is a slab page.  Also remove the unneeded bracket.

Signed-off-by: Yalin Wang <yalin.wang@sonymobile.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
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