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>
---
include/linux/mm.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 8dd4fde9d2e53..c6bf813a6b3d7 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -484,7 +484,8 @@ static inline void page_mapcount_reset(struct page *page)
static inline int page_mapcount(struct page *page)
{
- return atomic_read(&(page)->_mapcount) + 1;
+ VM_BUG_ON_PAGE(PageSlab(page), page);
+ return atomic_read(&page->_mapcount) + 1;
}
static inline int page_count(struct page *page)
--
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