[Bug 1292234] Re: qcow2 image corruption in trusty (qemu 1.7 and 2.0 candidate)

[Chris J Arges]

Serge,
So I was able to just compile my own qemu and test with that.

I did attempt a reverse bisect, and was able to reproduce as early as v1.1 and also reproduce on master HEAD.
v1.0 was inconclusive because qcow2 format I made with the newer binary seemed to be incompatible with v1.0; however from Jamies testing this seems to be a working version; so I'd say somewhere between v1.0.0, v1.1.0 lies the original change that enabled this issue. As I've been unable to reproduce this without virsh, reverse bisecting and using older qemu versions is a bit challenging as machine types change, features virsh wants to use aren't available, etc.

Another interesting thing I tested today was I was able to reproduce
with ext4 with extents disabled; maybe that gives more clues. Just to
make sure I wasn't crazy, mkfs'd the partition to vanilla ext4 and
iterated for most of the afternoon with no failures.

My next steps are going to be enabling verbose output for qcow2, looking
more deeply into what gets corrupted in the file, and  turning on host
filesystem debugging.

--chris

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Title:
  qcow2 image corruption in trusty (qemu 1.7 and 2.0 candidate)

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