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Date: Mon, 23 Dec 2013 10:57:27 +0800
From: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
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Subject: Re: [Qemu-devel] [PATCH V7 4/6] qcow2: cancel the modification on
 fail in qcow2_snapshot_create()
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To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: kwolf@redhat.com, jcody@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com, mreitz@redhat.com

于 2013/12/20 22:20, Stefan Hajnoczi 写道:
> On Thu, Dec 05, 2013 at 08:02:50PM +0800, Wenchao Xia wrote:
>> +restore_refcount:
>> +    if (qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, -1)
>> +        < 0 && errp) {
>> +        /* Nothing can be done now, need image check later */
>> +        error_setg(&err, "%s\nqcow2: Error in restoring refcount in snapshot",
>> +                   error_get_pretty(*errp));
>> +        error_free(*errp);
>> +        *errp = NULL;
>> +        error_propagate(errp, err);
>> +    }
>
> We get here if writing the new snapshot list failed.  If
> qcow2_update_snapshot_refcount(..., -1) also fails I think we should
> skip qcow2_free_clusters() below.  We don't know the exact state of the
> disk image anymore - better to leak clusters than to have a dangling
> reference.
>

   Make sense, dangling point should be avoid in any case, will fix,
Thanks for reviewing!

>> +dealloc_cluster:
>> +    qcow2_free_clusters(bs, sn->l1_table_offset,
>> +                        sn->l1_size * sizeof(uint64_t),
>> +                        QCOW2_DISCARD_ALWAYS);
>> +
>>   fail:
>>       g_free(sn->id_str);
>>       g_free(sn->name);
>> --
>> 1.7.1
>>
>>
>