On 09.11.2015 16:05, Alberto Garcia wrote:
> On Wed 04 Nov 2015 07:57:44 PM CET, Max Reitz wrote:
>> @@ -3519,11 +3537,18 @@ void qmp_x_blockdev_del(bool has_id, const char *id,
>> bdrv_get_device_or_node_name(bs));
>> goto out;
>> }
>> +
>> + if (!blk && !bs->monitor_list.tqe_prev) {
>> + error_setg(errp, "Node %s is not owned by the monitor",
>> + bs->node_name);
>> + goto out;
>> + }
>> }
>>
>> if (blk) {
>> blk_unref(blk);
>> } else {
>> + QTAILQ_REMOVE(&monitor_bdrv_states, bs, monitor_list);
>> bdrv_unref(bs);
>> }
>
> blk_unref(blk) will also unref the BDS (if there's any), so you also
> need to update monitor_bdrv_states in that case, don't you?If we get to blk_unref(blk), that means there is a BB attached to that BDS (if there is any). If that BDS is monitor-owned, that means its refcount is at least 2 (one from the BB, one from the monitor). Therefore, blockdev-del will fail before that point. > Anyway, wouldn't it make more sense to do this in bdrv_delete() ? No, I don't think so. The monitor_bdrv_states is not a plain list of BDSs, but actually contains strong references. Every time a BDS is entered there, that reference should be counted (which we don't actually have to call bdrv_ref() for since we're just keeping the initial refcount of 1 in qmp_blockdev_add()), and every time a BDS is removed, its reference should be dropped, just like is done here. That's the issue I had with this implementation of blockdev-del. It's just dropping references without actually having those references. Now we at least have the reference through monitor_bdrv_states, and in the future, we'll have such a list of monitor references for BBs, too. Max
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