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

[Linus Torvalds <torvalds@osdl.org>]

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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