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Date: Mon, 17 Mar 2003 19:27:38 -0800
From: Andrew Morton <akpm@digeo.com>
To: Neil Brown <neilb@cse.unsw.edu.au>
Cc: gilbertd@treblig.org, linux-kernel@vger.kernel.org, ext3-users@redhat.com
Subject: Re: 2.4.20: ext3/raid5 - allocating block in system zone/multiple 1
 requests for sector
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Neil Brown <neilb@cse.unsw.edu.au> wrote:
>
> These two symptoms strongly suggest a buffer aliasing problem.
> i.e. you have two buffers (one for data and one for metadata)
> that refer to the same location on disc.
> One is part of a file that was recently deleted, but the buffer hasn't
> been flushed yet.  The other is part of a new directory.
> The old buffer and the new buffer both get written to disc at much the
> same time (hence the "multiple 1 requests"), but the old buffer hits
> the disc second and so corrupts the filesystem.

This aliasing can happen very easily with direct-io, and it is something
which drivers should be able to cope with.

I hope RAID is not still assuming that all requests are unique in this way?

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