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;
Now you can drop the malloc and simply qemu_aio_get() a new
BlockQueueAIOCB.
Stefan
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