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Subject: Re: [PATCH] mm: fix page_mkclean_one (was: 2.6.19 file content
	corruption on ext3)
From: Andrei Popa <andrei.popa@i-neo.ro>
Reply-To: andrei.popa@i-neo.ro
To: Andrew Morton <akpm@osdl.org>
Cc: Linus Torvalds <torvalds@osdl.org>,
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Date: Sun, 24 Dec 2006 14:14:38 +0200
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On Sun, 2006-12-24 at 00:57 -0800, Andrew Morton wrote: 
> On Sun, 24 Dec 2006 00:43:54 -0800 (PST)
> Linus Torvalds <torvalds@osdl.org> wrote:
> 
> > I now _suspect_ that we're talking about something like
> > 
> >  - we started a writeout. The IO is still pending, and the page was 
> >    marked clean and is now in the "writeback" phase.
> >  - a write happens to the page, and the page gets marked dirty again. 
> >    Marking the page dirty also marks all the _buffers_ in the page dirty, 
> >    but they were actually already dirty, because the IO hasn't completed 
> >    yet.
> >  - the IO from the _previous_ write completes, and marks the buffers clean 
> >    again.
> 
> Some things for the testers to try, please:
> 
> - mount the fs with ext2 with the no-buffer-head option.  That means either:
> 
>   grub.conf:  rootfstype=ext2 rootflags=nobh
>   /etc/fstab: ext2 nobh

ierdnac ~ # mount
/dev/sda7 on / type ext2 (rw,noatime,nobh)

I have corruption.

> 
> - mount the fs with ext3 data=writeback, nobh
> 
>   grub.conf:  rootfstype=ext3 rootflags=nobh,data=writeback  (I hope this works)
>   /etc/fstab: ext2 data=writeback,nobh

ierdnac ~ # mount
/dev/sda7 on / type ext3 (rw,noatime,nobh)

ierdnac ~ # dmesg|grep EXT3
EXT3-fs: mounted filesystem with writeback data mode.
EXT3 FS on sda7, internal journal

I don't have corruption. I tested twice.

> 
> if that still fails we can rule out buffer_head funnies.
>