Re: [Qemu-devel] [PATCH 2/3] block: Add 'blockdev-del' QMP command

[Alberto Garcia]

On Sat 17 Oct 2015 08:06:19 PM CEST, Max Reitz wrote:
>> +    if (blk_get_refcnt(blk) > 1 ||
>> +        (bs && (bs->refcnt > 1 || !QLIST_EMPTY(&bs->parents)))) {
>> +        error_setg(errp, "Block device %s is being used", device);
>> +        goto out;
>> +    }
>
> I can't think of a way off the top of my head that a BB with a refcount
> of one or a BDS with a refcount of one without any parents would not be
> monitor-owned, but I don't quite like assuming it just from the refcount
> and the parent list anyway.

I agree, I would also like to have a clearer way to do it.

I'll try to go over all possible ways to create a BDS and see other
cases that I might have missed. At the very list I would like to extend
the iotest and make it as comprehensive as possible.

> The two patches which are significant for this patch are:
> - "blockdev: Keep track of monitor-owned BDS" from the first series
> - "blockdev: Add list of monitor-owned BlockBackends" from the second
>
> Explaining what they do and why they are relevant to this patch doesn't
> really seem necessary, but anyway: They add one list for the
> monitor-owned BDSs and one for the monitor-owned BBs.

Yeah, those would be handy indeed.

> It's up to you. It probably works just how you implemented it, and
> considering the pace of the "BB and media" series (and other series of
> mine in the past year), getting those two series merged may be a
> matter of decades. So it's probably best to do it like this for now
> and I'll fix it up then...

I think I'll first try to go over all possible cases and see what I
find.

Thanks,

Berto