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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
Date: Mon, 17 Mar 2003 19:27:38 -0800	[thread overview]
Message-ID: <20030317192738.6a420ed0.akpm@digeo.com> (raw)
In-Reply-To: <15990.28660.687262.457216@notabene.cse.unsw.edu.au>

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?


  reply	other threads:[~2003-03-18  3:17 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2003-03-16 15:01 Dr. David Alan Gilbert
2003-03-18  1:01 ` Neil Brown
2003-03-18  3:27   ` Andrew Morton [this message]
2003-03-18  5:59     ` Neil Brown
2003-03-18 14:04   ` Dave Gilbert (Home)

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