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From: Edward Thornber <thornber@redhat.com>
To: Dennis Yang <dennisyang@qnap.com>
Cc: device-mapper development <dm-devel@redhat.com>
Subject: Re: Possible data corruption with dm-thin
Date: Fri, 24 Jun 2016 09:55:11 -0400	[thread overview]
Message-ID: <20160624135510.GA13946@roamer.bos.redhat.com> (raw)
In-Reply-To: <CAAR726JWQ4VKOVR87QX6Tmuhu1JnCymm7coLT=TFn3BseKm8XA@mail.gmail.com>

Hi Dennis,

On Tue, Jun 21, 2016 at 03:56:26PM +0800, Dennis Yang wrote:
> So my question is, does dm-thin have any mechanism to eliminate the race
> when
> discarded block is reused right away by another device?

I'll try and recreate your scenario.  The transaction-manager will not
reallocate a block that's been freed within a transaction so that we
can always rollback.  So as long as there hasn't been a commit,
reallocation shouldn't be possible.  This is what normally guards
allocation, but in your case I think you may be onto something and we
may have to hold onto the data cell until the passdown discards are
complete.

- Joe

  parent reply	other threads:[~2016-06-24 13:55 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-21  7:56 Possible data corruption with dm-thin Dennis Yang
2016-06-21  8:59 ` Zdenek Kabelac
2016-06-21 10:40   ` Dennis Yang
2016-06-21 10:46     ` Zdenek Kabelac
2016-06-24 13:55 ` Edward Thornber [this message]
2016-06-27  9:32   ` Dennis Yang
2016-07-01 13:18     ` Edward Thornber
2016-09-06  4:51       ` Dennis Yang

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