linux-kernel - Re: [PATCH] mm: fix page_mkclean_one (was: 2.6.19 file content corruption on ext3)

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Date:	Wed, 27 Dec 2006 16:42:40 -0800 (PST)
From:	Linus Torvalds <torvalds@...l.org>
To:	Martin Schwidefsky <schwidefsky@...ibm.com>
cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Martin Michlmayr <tbm@...ius.com>,
	Hugh Dickins <hugh@...itas.com>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Arjan van de Ven <arjan@...radead.org>,
	Andrei Popa <andrei.popa@...eo.ro>,
	Andrew Morton <akpm@...l.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Florian Weimer <fw@...eb.enyo.de>,
	Marc Haber <mh+linux-kernel@...schlus.de>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Arnd Bergmann <arnd.bergmann@...ibm.com>,
	gordonfarquharson@...il.com
Subject: Re: [PATCH] mm: fix page_mkclean_one (was: 2.6.19 file content
 corruption on ext3)



On Thu, 28 Dec 2006, Martin Schwidefsky wrote:
> 
> For s390 there are two aspects to consider:
> 1) the pte values are 100% software controlled.

That's fine. In that situation, you shouldn't need any atomic ops at all, 
I think all our sw page-table operations are already done under the pte 
lock. 

The reason x86 needs to be careful is exactly the fact that the hardware 
will obviously do a lot on its own, and the hardware is _not_ going to 
honor our page table locking ;)

In an all-sw situation, a lot of this should be easier. S390 has _other_ 
things that are inconvenient (the strange "dirty bit is not in the page 
tables" thing that makes it look different from everybody else), but hey, 
it's a balance..

So for s390, ptep_exchange() in my example should be able to be a simple 
"load old value and store new one", assuming everybody honors the pte lock 
(and they _should_).

		Linus
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