Subject: Re: [PATCH] mm: fix page_mkclean_one (was: 2.6.19 file content
	corruption on ext3)
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: Linus Torvalds <torvalds@osdl.org>, Martin Michlmayr <tbm@cyrius.com>,
       Hugh Dickins <hugh@veritas.com>, Nick Piggin <nickpiggin@yahoo.com.au>,
       Arjan van de Ven <arjan@infradead.org>,
       Andrei Popa <andrei.popa@i-neo.ro>, Andrew Morton <akpm@osdl.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Florian Weimer <fw@deneb.enyo.de>,
       Marc Haber <mh+linux-kernel@zugschlus.de>,
       Martin Schwidefsky <schwidefsky@de.ibm.com>,
       Heiko Carstens <heiko.carstens@de.ibm.com>,
       Arnd Bergmann <arnd.bergmann@de.ibm.com>, gordonfarquharson@gmail.com
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Date: Thu, 21 Dec 2006 09:10:38 +0100
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On Wed, 2006-12-20 at 21:36 -0500, Trond Myklebust wrote:
> On Wed, 2006-12-20 at 23:15 +0100, Peter Zijlstra wrote:
> > I think this is also needed:
> 
> NAK
> 
> invalidate_inode_pages2() should _not_ be pretending that dirty pages
> are clean. This patch is incorrect both for the NFS usage and for the
> directIO usage.
> 
> In the latter case, if someone has the page mmapped, resulting in the
> page getting marked as dirty _after_ a directIO write, then it would be
> wrong to discard that data. Only dirty data from _before_ the directIO
> write should needs to be discarded (and that is achieved by unmapping,
> then cleaning the page prior to the directIO call)...
> 
> For the NFS case, the race is a bit more tricky, since you have the
> "unstable write" case which means that the page is neither marked as
> dirty, nor is entirely clean ('cos we don't know that the server has
> committed the data to permanent storage yet).

Then this patch:
http://kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.20-rc1/2.6.20-rc1-mm1/broken-out/nfs-fix-nr_file_dirty-underflow.patch

is equally wrong, right?

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