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Date: Thu, 26 Feb 2015 15:07:34 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [RFC PATCH 06/14] NBD client: connect to nbd
 server later
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To: Max Reitz <mreitz@redhat.com>, Wen Congyang <wency@cn.fujitsu.com>, qemu devel <qemu-devel@nongnu.org>, Kevin Wolf <kwolf@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>, Jiang Yunhong <yunhong.jiang@intel.com>, Dong Eddie <eddie.dong@intel.com>, "Dr. David Alan Gilbert" <dgilbert@redhat.com>, Gonglei <arei.gonglei@huawei.com>, Yang Hongyang <yanghy@cn.fujitsu.com>, zhanghailiang <zhang.zhanghailiang@huawei.com>



On 25/02/2015 15:22, Max Reitz wrote:
> 3. nbd_co_discard()
>     quorum doens't call bdrv_co_discard(), so it is OK to return -EIO here. 

That can change, so I think you should return -EIO either everywhere or
nowhere.  Which probably means nowhere.

> Hm, okay. How about adding an option to quorum for ignoring errors from
> a specific child? It's probably not possible to do something like
> "children.1.ignore-errors=true", but maybe you can just ignore errors in
> quorum from any but the first child if the read pattern is set to
> "first", that would make sense to me.
> 
> But if you don't want to do that, I guess just making NBD some kind of
> /dev/null before it's connected should be fine.

I think what Wen is doing is okay, especially since it's only the
special nbd+colo:// URIs that are acting as /dev/null.

Paolo