linux-kernel - Re: 2.6.19 file content corruption on ext3

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Message-ID: <Pine.LNX.4.64.0612281552100.4473@woody.osdl.org>
Date:	Thu, 28 Dec 2006 15:54:00 -0800 (PST)
From:	Linus Torvalds <torvalds@...l.org>
To:	Anton Altaparmakov <aia21@....ac.uk>
cc:	Andrew Morton <akpm@...l.org>,
	Guillaume Chazarain <guichaz@...oo.fr>,
	David Miller <davem@...emloft.net>, ranma@...edrich.de,
	gordonfarquharson@...il.com,
	Marc Haber <mh+linux-kernel@...schlus.de>,
	Nick Piggin <nickpiggin@...oo.com.au>, andrei.popa@...eo.ro,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Hugh Dickins <hugh@...itas.com>,
	Florian Weimer <fw@...eb.enyo.de>,
	Martin Michlmayr <tbm@...ius.com>, arjan@...radead.org,
	Chen Kenneth W <kenneth.w.chen@...el.com>
Subject: Re: 2.6.19 file content corruption on ext3



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
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