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

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Message-Id: <1166688638.30008.22.camel@twins>
Date:	Thu, 21 Dec 2006 09:10:38 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Trond Myklebust <trond.myklebust@....uio.no>
Cc:	Linus Torvalds <torvalds@...l.org>,
	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>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	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 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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