Date: Fri, 22 Jun 2007 05:46:42 +0100 (BST)
From: Hugh Dickins <hugh@veritas.com>
To: Christoph Lameter <clameter@sgi.com>
cc: Nicolas Ferre <nicolas.ferre@rfo.atmel.com>,
       ARM Linux Mailing List 
	<linux-arm-kernel@lists.arm.linux.org.uk>,
       Linux Kernel list <linux-kernel@vger.kernel.org>,
       Marc Pignat <marc.pignat@hevs.ch>, Andrew Victor <andrew@sanpeople.com>,
       Pierre Ossman <drzeus@drzeus.cx>,
       Andrew Morton <akpm@linux-foundation.org>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Russell King <rmk@arm.linux.org.uk>, Matthew Wilcox <matthew@wil.cx>
Subject: Re: Oops in a driver while using SLUB as a SLAB allocator
In-Reply-To: <Pine.LNX.4.64.0706211839440.11717@schroedinger.engr.sgi.com>
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References: <467A4532.40301@rfo.atmel.com> <Pine.LNX.4.64.0706212244090.19755@blonde.wat.veritas.com>
 <Pine.LNX.4.64.0706211839440.11717@schroedinger.engr.sgi.com>
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On Thu, 21 Jun 2007, Christoph Lameter wrote:
> On Thu, 21 Jun 2007, Hugh Dickins wrote:
> 
> > Seems a little odd that it's gone throughout 2.6.22-rc unnoticed
> > until now - nobody else trying SLUB on ARM or PA-RISC yet perhaps.
> 
> The impact is only on a subset of ARM machines.
> 
> PA_RISC? It looks like they run their own flushing function for byte 
> ranges called flush_kernel_dache_range. That does not use the page struct.

PA-RISC does have a function of that name, and I'm guessing that
you came across it in looking at the PA-RISC dma_map_single.

But PA-RISC also has a function called flush_dcache_page, which uses
page_mapping and expects a struct address_space * from it.  If that
can ever be get applied to a SLOB page (which is not so clear as in
the ARM case, but cannot easily be ruled out completely), we're
in trouble without a PageSlab test within page_mapping.

Hugh
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