Re: [next-20150119]regression (mm)?

["Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>]

Russell King - ARM Linux wrote:
> On Tue, Jan 20, 2015 at 02:16:43AM +0200, Kirill A. Shutemov wrote:
> > Better option would be converting 2-lvl ARM configuration to
> > <asm-generic/pgtable-nopmd.h>, but I'm not sure if it's possible.
> 
> Well, IMHO the folded approach in asm-generic was done the wrong way
> which barred ARM from ever using it.

Okay, I see.

Regarding the topic bug. Completely untested patch is below. Could anybody
check if it helps?

>From 34b9182d08ef2b541829e305fcc91ef1d26b27ea Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Date: Tue, 20 Jan 2015 15:47:22 +0200
Subject: [PATCH] arm: define __PAGETABLE_PMD_FOLDED for !LPAE

ARM uses custom implementation of PMD folding in 2-level page table case.
Generic code expects to see __PAGETABLE_PMD_FOLDED to be defined if PMD is
folded, but ARM doesn't do this. Let's fix it.

Defining __PAGETABLE_PMD_FOLDED will drop out unused __pmd_alloc().
It also fixes problems with recently-introduced pmd accounting on ARM
without LPAE.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: Nishanth Menon <nm@ti.com>
---
 arch/arm/include/asm/pgtable-2level.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm/include/asm/pgtable-2level.h b/arch/arm/include/asm/pgtable-2level.h
index bcc5e300413f..bfd662e49a25 100644
--- a/arch/arm/include/asm/pgtable-2level.h
+++ b/arch/arm/include/asm/pgtable-2level.h
@@ -10,6 +10,8 @@
 #ifndef _ASM_PGTABLE_2LEVEL_H
 #define _ASM_PGTABLE_2LEVEL_H
 
+#define __PAGETABLE_PMD_FOLDED
+
 /*
  * Hardware-wise, we have a two level page table structure, where the first
  * level has 4096 entries, and the second level has 256 entries.  Each entry
-- 
2.1.4