On Mon, Jun 01, 2020 at 01:07:24PM +0200, gregkh@xxxxxxxxxxxxxxxxxxx wrote: > > 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@xxxxxxxxxxxxxxx>. Please don't. The patch known to cause trouble and going to be effectively reverted: https://lore.kernel.org/r/159032779896.957378.7852761411265662220.stgit@buzz If you have it in any other stable queue, please drop it. > ------------------ original commit in Linus's tree ------------------ > > From 1d148e218a0d0566b1c06f2f45f1436d53b049b2 Mon Sep 17 00:00:00 2001 > From: "Wang, Yalin" <Yalin.Wang@xxxxxxxxxxxxxx> > 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@xxxxxxxxxxxxxx> > Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > > 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) > -- Kirill A. Shutemov
