Subject: Re: mmotm 2015-01-22-15-04: qemu failures due to 'mm: account pmd page tables to the process'

From: Guenter Roeck <[email-masked]>
Date: Fri, 23 Jan 2015 21:52:07 -0800

On Fri, Jan 23, 2015 at 01:55:19PM -0800, Andrew Morton wrote:
> On Fri, 23 Jan 2015 07:07:56 -0800 Guenter Roeck <[email-masked]> wrote:
> 
> > >>
> > >> qemu:microblaze generates warnings to the console.
> > >>
> > >> WARNING: CPU: 0 PID: 32 at mm/mmap.c:2858 exit_mmap+0x184/0x1a4()
> > >>
> > >> with various call stacks. See
> > >> http://server.roeck-us.net:8010/builders/qemu-microblaze-mmotm/builds/15/steps/qemubuildcommand/logs/stdio
> > >> for details.
> > >
> > > Could you try patch below? Completely untested.
> > >
> > >>From b584bb8d493794f67484c0b57c161d61c02599bc Mon Sep 17 00:00:00 2001
> > > From: "Kirill A. Shutemov" <[email-masked]>
> > > Date: Fri, 23 Jan 2015 13:08:26 +0200
> > > Subject: [PATCH] microblaze: define __PAGETABLE_PMD_FOLDED
> > >
> > > Microblaze uses custom implementation of PMD folding, but doesn't define
> > > __PAGETABLE_PMD_FOLDED, which generic code expects to see. Let's fix it.
> > >
> > > Defining __PAGETABLE_PMD_FOLDED will drop out unused __pmd_alloc().
> > > It also fixes problems with recently-introduced pmd accounting.
> > >
> > > Signed-off-by: Kirill A. Shutemov <[email-masked]>
> > > Reported-by: Guenter Roeck <[email-masked]>
> > 
> > Tested working.
> > 
> > Tested-by: Guenter Roeck <[email-masked]>
> > 
> > Any idea how to fix the sh problem ?
> 
> Can you tell us more about it?  All I'm seeing is "qemu:sh fails to
> shut down", which isn't very clear.

Turns out that the include file defining __PAGETABLE_PMD_FOLDED
was not always included where used, resulting in a messed up mm_struct.

The patch below fixes the problem for the sh architecture.
No idea if the patch is correct/acceptable for other architectures.

Guenter

---
>>From 2a11491a5d0642c924db1d78f2b8f21985459062 Mon Sep 17 00:00:00 2001
From: Guenter Roeck <[email-masked]>
Date: Fri, 23 Jan 2015 21:44:06 -0800
Subject: [PATCH] mm_types: include asm/pgtable.h

Commit 22310c209483 ("mm: account pmd page tables to the process") starts using
__PAGETABLE_PMD_FOLDED in mm_types.h. This define is usually declared in
pgtable.h, so pgtable.h neeeds to be included.

Fixes runtime error with sh targets.

Fixes: 22310c209483 ("mm: account pmd page tables to the process")
Signed-off-by: Guenter Roeck <[email-masked]>
---
 include/linux/mm_types.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 79cdf6f..65db573 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -13,6 +13,7 @@
 #include <linux/uprobes.h>
 #include <linux/page-flags-layout.h>
 #include <asm/page.h>
+#include <asm/pgtable.h>
 #include <asm/mmu.h>
 
 #ifndef AT_VECTOR_SIZE_ARCH
-- 
2.1.0

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