From mboxrd@z Thu Jan  1 00:00:00 1970
From: Joe Thornber <thornber@redhat.com>
Subject: Re: dm-thin: commit metadata bug
Date: Fri, 5 Aug 2011 14:13:39 +0100
Message-ID: <20110805131338.GA1882@ubuntu>
References: <Pine.LNX.4.64.1108050856100.19545@hs20-bc2-1.build.redhat.com>
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To: Mikulas Patocka <mpatocka@redhat.com>
Cc: dm-devel@redhat.com, "Alasdair G. Kergon" <agk@redhat.com>
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On Fri, Aug 05, 2011 at 08:59:09AM -0400, Mikulas Patocka wrote:
> There is a bug in committing metadata --- you can't commit metadata if 
> there is any copying or zeroing in flight. The problem is that in this 
> case, the block you are copying to is already allocated, but it is not 
> linked anywhere in the metadata. So it creates lost blocks in case of 
> crash.

Yes, well known and documented.  We take this hit, fsck will repair.

- Joe