Re: [Qemu-devel] [PATCH v6 11/12] qed: Implement .bdrv_drain

[Paolo Bonzini]

On 22/10/2015 12:53, Kevin Wolf wrote:
> Am 22.10.2015 um 08:32 hat Fam Zheng geschrieben:
>> The "need_check_timer" is used to clear the "NEED_CHECK" flag in the
>> image header after a grace period once metadata update has finished. In
>> compliance to the bdrv_drain semantics we should make sure it remains
>> deleted once .bdrv_drain is called.
>>
>> We cannot reuse qed_need_check_timer_cb because it calls bdrv_aio_flush
>> with a completion callback that starts more I/O, bdrv_drain cannot cope
>> with this.
> 
> For the record: I discussed this with Fam on IRC and we came to the
> conclusion that we should instead fix bdrv_drain() to correctly drain
> in-flight flushes.
> 
> In order to achieve this, Fam will send a series that adds a
> BdrvTrackedRequest to all remaining asynchronous operations. So far we
> have identified flush, discard and aio_ioctl. At the same time he will
> send a rebased version of this series that goes back to asynchronous
> flushing in bdrv_qed_drain().

This is a completely separate bug. Can you at least merge all patches
except this, so that everything except QED can do snapshots with
dataplane?  Of course there will be a v7 at least for patch 9.

Paolo