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From: Wen Congyang <wency@cn.fujitsu.com>
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Date: Tue, 13 Oct 2015 17:08:17 +0800
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Subject: Re: [Qemu-devel] [Qemu-block] [PATCH v10 08/10] Implement new
 driver for block replication
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To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Fam Zheng <famz@redhat.com>, zhanghailiang <zhang.zhanghailiang@huawei.com>, qemu block <qemu-block@nongnu.org>, Jiang Yunhong <yunhong.jiang@intel.com>, Dong Eddie <eddie.dong@intel.com>, qemu devel <qemu-devel@nongnu.org>, "Michael R. Hines" <mrhines@linux.vnet.ibm.com>, Max Reitz <mreitz@redhat.com>, Gonglei <arei.gonglei@huawei.com>, Stefan Hajnoczi <stefanha@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Yang Hongyang <yanghy@cn.fujitsu.com>, "Dr. David Alan Gilbert" <dgilbert@redhat.com>

On 10/13/2015 12:27 AM, Stefan Hajnoczi wrote:
> On Fri, Sep 25, 2015 at 02:17:36PM +0800, Wen Congyang wrote:
>> +        /* start backup job now */
>> +        bdrv_op_unblock(s->hidden_disk, BLOCK_OP_TYPE_BACKUP_TARGET,
>> +                        s->active_disk->backing_blocker);
>> +        bdrv_op_unblock(s->secondary_disk, BLOCK_OP_TYPE_BACKUP_SOURCE,
>> +                        s->hidden_disk->backing_blocker);
> 
> Why is it safe to unblock these operations?
> 
> Why do they have to be blocked for non-replication users?

hidden_disk and secondary disk are opened as backing file, so it is blocked for
non-replication users.
What can I do if I don't unblock it and want to do backup?

Thanks
Wen Congyang

> 
> Stefan
> .
>