Re: [Qemu-devel] [Qemu-block] [PATCH 10/29] qed: Remove callback from qed_write_header()

[Paolo Bonzini]

On 01/06/2017 17:59, Kevin Wolf wrote:
> Am 31.05.2017 um 14:32 hat Stefan Hajnoczi geschrieben:
>> On Fri, May 26, 2017 at 10:21:51PM +0200, Kevin Wolf wrote:
>>>  static void qed_clear_need_check(void *opaque, int ret)
>>>  {
>>>      BDRVQEDState *s = opaque;
>>>  
>>>      if (ret) {
>>> -        qed_unplug_allocating_write_reqs(s);
>>> -        return;
>>> +        goto out;
>>>      }
>>>  
>>>      s->header.features &= ~QED_F_NEED_CHECK;
>>> -    qed_write_header(s, qed_flush_after_clear_need_check, s);
>>> +    ret = qed_write_header(s);
>>> +    (void) ret;
>>> +
>>> +    ret = bdrv_flush(s->bs);
>>> +    (void) ret;
>>> +
>>> +out:
>>> +    qed_unplug_allocating_write_reqs(s);
>>>  }
>>
>> Should we unplug allocating write reqs before flushing?  The async code
>> kicks off a flush but doesn't wait for it to complete.
> 
> You're right that moving it up would match the old code. Not sure if it
> would make much of a difference, though, isn't the request queue drained
> in the kernel anyway while doing a flush?

No, it isn't AFAIK.

Paolo

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