The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
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
diff --git a/include/linux/mm.h b/include/linux/mm.h index 8dd4fde9d2e5..c6bf813a6b3d 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)