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From: Alberto Garcia <berto@igalia.com>
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Date: Tue, 09 Feb 2016 16:39:50 +0100
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Subject: Re: [Qemu-devel] [PATCH 1/3] block: Allow x-blockdev-del on a BB
	with a monitor-owned BDS
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To: Eric Blake <eblake@redhat.com>, qemu-devel@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>, qemu-block@nongnu.org, Max Reitz <mreitz@redhat.com>

On Tue 09 Feb 2016 04:34:09 PM CET, Eric Blake wrote:
> On 02/08/2016 07:14 AM, Alberto Garcia wrote:
>
> When sending a multi-patch series, you should always include a 0/3 cover
> letter.  The cover letter is optional only for a lone patch.

Sorry, I didn't know. The description of the first patch already
contains everything that would go into the cover letter, that's why I
decided to do it like this. I'll include the cover letter in the future.

>>          if (bs->refcnt > 1) {
>> -            error_setg(errp, "Block device %s is in use",
>> -                       bdrv_get_device_or_node_name(bs));
>> -            goto out;
>> +            /* We allow deleting a BlockBackend that has a BDS with an
>> +             * extra reference if that extra reference is from the
>> +             * monitor. */
>> +            bool bs_has_only_monitor_ref =
>> +                blk && bs->monitor_list.tqe_prev && bs->refcnt == 2;
>> +            if (!bs_has_only_monitor_ref) {
>
> I don't think the temporary bool or nested 'if' are necessary; but at
> the same time, I don't think the following is any more legible:
>
> /* Prohibit deleting a BlockBackend whose BDS is in use by any more than
> a single monitor */
> if (bs->refcnt > 1 + (blk && bs->monitor_list.tqe_prev)) {
>     error_setg(...

Exactly, I considered several options and I thought the one I finally
chose would be the easiest to read.

Thanks!

Berto