linux-kernel - Re: [Stable-review] [36/55] [PARISC] slub: fix panic with DISCONTIGMEM

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Date:	Tue, 3 May 2011 15:46:13 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Ben Hutchings <ben@...adent.org.uk>
cc:	James Bottomley <James.Bottomley@...e.de>,
	Michael Schmitz <schmitzmic@...glemail.com>,
	linux-kernel@...r.kernel.org, stable@...nel.org,
	Pekka Enberg <penberg@...nel.org>, akpm@...ux-foundation.org,
	torvalds@...ux-foundation.org, stable-review@...nel.org,
	alan@...rguk.ukuu.org.uk, Greg KH <gregkh@...e.de>
Subject: Re: [Stable-review] [36/55] [PARISC] slub: fix panic with
 DISCONTIGMEM

On Mon, 2 May 2011, Ben Hutchings wrote:

> > From: James Bottomley <James.Bottomley@...senPartnership.com>
> > 
> > commit 4a5fa3590f09999f6db41bc386bce40848fa9f63 upstream.
> > 
> > Slub makes assumptions about page_to_nid() which are violated by
> > DISCONTIGMEM and !NUMA.  This violation results in a panic because
> > page_to_nid() can be non-zero for pages in the discontiguous ranges and
> > this leads to a null return by get_node().  The assertion by the
> > maintainer is that DISCONTIGMEM should only be allowed when NUMA is also
> > defined.  However, at least six architectures: alpha, ia64, m32r, m68k,
> > mips, parisc violate this.  The panic is a regression against slab, so
> > just mark slub broken in the problem configuration to prevent users
> > reporting these panics.
> 
> This stable series also included the patches:
> 
> commit 6a682f634ba9615d3498d1e20a23e9d4fcb39f16
> Author: David Rientjes <rientjes@...gle.com>
> Date:   Wed Apr 20 19:27:13 2011 -0700
> 
>     set memory ranges in N_NORMAL_MEMORY when onlined
>     
>     commit d9b41e0b54fd7e164daf1e9c539c1070398aa02e upstream.
> 
> commit 8858587af25efc06d5cce42676786b3d7a9160f2
> Author: Michael Schmitz <schmitzmic@...glemail.com>
> Date:   Tue Apr 26 14:51:53 2011 +1200
> 
>     m68k/mm: Set all online nodes in N_NORMAL_MEMORY
>     
>     commit 4aac0b4815ba592052758f4b468f253d383dc9d6 upstream.
> 
> which look like they're supposed to make slub work on these two
> architectures (parisc and m68k).  Do they?  If not, do they fix a
> different problem?
> 

SLUB relies heavily on N_NORMAL_MEMORY, so these two patches fix that 
allocator but the problem is actually not just isolated to that subsystem; 
it fixes an issue with anything that uses N_NORMAL_MEMORY.

The former patch sets the nodes correctly for parisc and Michael's patch 
sets the nodes correctly for m68k, so it's the same fix for two different 
previously-broken architectures.
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