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Date: Thu, 28 Dec 2006 15:54:00 -0800 (PST)
From: Linus Torvalds <torvalds@osdl.org>
To: Anton Altaparmakov <aia21@cam.ac.uk>
cc: Andrew Morton <akpm@osdl.org>, Guillaume Chazarain <guichaz@yahoo.fr>,
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Subject: Re: 2.6.19 file content corruption on ext3
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On Thu, 28 Dec 2006, Anton Altaparmakov wrote:
> 
> But are chunks 3 and 4 in separate buffer heads?  Sorry could not see it 
> immediately from the output you showed...

No, this is a 4kB filesystem. A single bh per page.

> It is just that there may be a different cause rather than buffer dirty 
> state...

Sure.

> A shot in the dark I know but it could perhaps be that a "COW for 
> MAP_PRIVATE" like event happens when the page is dirty already thus the 
> second write never actually makes it to the shared page thus it never gets 
> written out.

There are no private mappings anywhere, and no forks. Just a single mmap 
(well, we unmap and remap in order to force the page cache to be 
invalidated properly with the posix_fadvise() thing, but that's literally 
the only user).

		Linus