Comment 9 for bug 1040033

I haven't yet reproduced this, but looking through the git commit logs the following seems a possible fix:

commit 206e6d8551839008b6858cf8f500d2e644d2b561
Author: Stefan Hajnoczi <email address hidden>
Date: Mon Jun 18 14:00:57 2012 +0100

    qcow2: preserve free_byte_offset when qcow2_alloc_bytes() fails

    When qcow2_alloc_clusters() error handling code was introduced in commit
    5d757b563d59142ca81e1073a8e8396750a0ad1a, the value of free_byte_offset
    was clobbered in the error case. This patch keeps free_byte_offset at 0
    so we will try to allocate clusters again next time this function is
    called.

    Signed-off-by: Stefan Hajnoczi <email address hidden>
    Signed-off-by: Kevin Wolf <email address hidden>

:100644 100644 66f3915... 5e3f915... M block/qcow2-refcount.c

Further encouraging is that the bug this fixes was introduced after 1.0 (the precise version).

It also could possibly be:

commit 166acf546f476d3594a1c1746dc265f1984c5c85
Author: Kevin Wolf <email address hidden>
Date: Fri May 11 18:18:36 2012 +0200

    qcow2: Support for fixing refcount inconsistencies

    Signed-off-by: Kevin Wolf <email address hidden>