On Wed, Aug 10, 2011 at 5:37 PM, Stefan Hajnoczi
<stefanha@xxxxxxxxxxxxxxxxxx> wrote:
> On Wed, Aug 10, 2011 at 01:54:33PM +0800, Zhi Yong Wu wrote:
>> On Tue, Aug 9, 2011 at 8:49 PM, Stefan Hajnoczi <stefanha@xxxxxxxxx> wrote:
>> > On Tue, Aug 9, 2011 at 5:17 AM, Zhi Yong Wu <wuzhy@xxxxxxxxxxxxxxxxxx> wrote:
>> >> +BlockDriverAIOCB *qemu_block_queue_enqueue(BlockQueue *queue,
>> >> + BlockDriverState *bs,
>> >> + BlockRequestHandler *handler,
>> >> + int64_t sector_num,
>> >> + QEMUIOVector *qiov,
>> >> + int nb_sectors,
>> >> + BlockDriverCompletionFunc *cb,
>> >> + void *opaque)
>> >> +{
>> >> + BlockIORequest *request;
>> >> + BlockDriverAIOCB *acb;
>> >> +
>> >> + request = qemu_malloc(sizeof(BlockIORequest));
>> >> + request->bs = bs;
>> >> + request->handler = handler;
>> >> + request->sector_num = sector_num;
>> >> + request->qiov = qiov;
>> >> + request->nb_sectors = nb_sectors;
>> >> + request->cb = cb;
>> >> + request->opaque = opaque;
>> >> +
>> >> + QTAILQ_INSERT_TAIL(&queue->requests, request, entry);
>> >
>> > It would be simpler to define BlockQueueAIOCB and using it as our acb
>> > instead of managing an extra BlockIORequest structure. That way you
>> > don't need to worry about extra mallocs and frees.
>> Sorry, i don't get what you mean. how to define it? Can you elaborate?
>
> BlockDriverAIOCB is designed to be embedded inside a bigger struct. For
> example, QEDAIOCB is a larger struct that contains BlockDriverAIOCB as
> its first field:
>
> typedef struct QEDAIOCB {
> BlockDriverAIOCB common;
> ...
> } QEDAIOCB;
>
> And the QED AIOPool contains the size of QEDAIOCB so that qemu_aio_get() can
> allocate the full QEDAIOCB struct:
>
> static AIOPool qed_aio_pool = {
> .aiocb_size = sizeof(QEDAIOCB),
> .cancel = qed_aio_cancel,
> };
>
> This allows QED to store per-request state in QEDAIOCB for the lifetime of a
> request:
>
> QEDAIOCB *acb = qemu_aio_get(&qed_aio_pool, bs, cb, opaque);
>
> acb->is_write = is_write;
> acb->finished = NULL;
> acb->qiov = qiov;
> ...
>
> I suggest creating a BlockQueueAIOCB that contains the fields from
> BlockIORequest (which is no longer needed as a separate struct):
>
> typedef struct BlockQueueAIOCB {
> BlockDriverAIOCB common;
> BlockRequestHandler *handler;
> int64_t sector_num;
> QEMUIOVector *qiov;
> int nb_sectors;
> QTAILQ_ENTRY(BlockQueueAIOCB) entry; /* pending request queue */
> } BlockQueueAIOCB;
Its name is a bit confusing. One ACB is inserted into block queue.
>
> Now you can drop the malloc and simply qemu_aio_get() a new
> BlockQueueAIOCB.
>
> Stefan
>
--
Regards,
Zhi Yong Wu
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