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Re: [Qemu-devel] [RFC PATCH v2 6/8] dma: Implement .cancel_async
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [RFC PATCH v2 6/8] dma: Implement .cancel_async |
Date: |
Tue, 26 Aug 2014 11:57:29 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.7.0 |
Il 26/08/2014 11:21, Fam Zheng ha scritto:
> On Tue, 08/26 10:46, Paolo Bonzini wrote:
>> Il 26/08/2014 08:08, Fam Zheng ha scritto:
>>> + if (dbs->cancelled) {
>>> + ret = -ECANCELED;
>>> + }
>>
>> Why is dbs->cancelled necessary?
>
> Request may complete after bdrv_aio_cancel_async with other status, this flag
> is checked to fix the status to -ECANCELED.
Ah, that's because the operation could be partly incomplete?
I think it would be better to call dma_complete with -ECANCELED, instead
of doing the same dbs->cancelled check twice. For example, in dma_bdrv_cb:
if (dbs->sg_cur_index == dbs->sg->nsg || ret < 0) {
dma_complete(dbs, ret);
return;
}
if (dbs->cancelled) {
dma_complete(dbs, -ECANCELED);
return;
}
>>> +static void dma_aio_cancel_async(BlockDriverAIOCB *acb)
>>> +{
>>> + DMAAIOCB *dbs = container_of(acb, DMAAIOCB, common);
>>> +
>>> + trace_dma_aio_cancel(dbs);
>>> +
>>> + dbs->cancelled = true;
>>> + if (dbs->acb) {
>>> + acb = dbs->acb;
>>> + dbs->acb = NULL;
>>
>> Why do you need to set dbs->acb to NULL, since the callback is going to
>> be called?
>
> Just copied from dma_aio_cancel, but seems not particularly useful. It reminds
> me that the one in dma_aio_cancel also looks suspicious.
Yeah, that one looks useless too...
Paolo
- [Qemu-devel] [RFC PATCH v2 1/8] block: Add refcnt in BlockDriverAIOCB, (continued)
- [Qemu-devel] [RFC PATCH v2 1/8] block: Add refcnt in BlockDriverAIOCB, Fam Zheng, 2014/08/26
- [Qemu-devel] [RFC PATCH v2 2/8] block: Add bdrv_aio_cancel_async, Fam Zheng, 2014/08/26
- [Qemu-devel] [RFC PATCH v2 3/8] tests: Add testing code for bdrv_aio_cancel_async, Fam Zheng, 2014/08/26
- [Qemu-devel] [RFC PATCH v2 4/8] linux-aio: Implement .cancel_async, Fam Zheng, 2014/08/26
- [Qemu-devel] [RFC PATCH v2 5/8] thread-pool: Implement .cancel_async, Fam Zheng, 2014/08/26
- [Qemu-devel] [RFC PATCH v2 6/8] dma: Implement .cancel_async, Fam Zheng, 2014/08/26
- [Qemu-devel] [RFC PATCH v2 7/8] block: Implement bdrv_em_co_aiocb_info.cancel_async, Fam Zheng, 2014/08/26
- [Qemu-devel] [RFC PATCH v2 8/8] iscsi: Implement .cancel_async in acb info, Fam Zheng, 2014/08/26