On Thu, Sep 1, 2011 at 12:44 PM, Zhi Yong Wu <wuzhy@xxxxxxxxxxxxxxxxxx> wrote:
> +struct BlockIORequest {
> + QTAILQ_ENTRY(BlockIORequest) entry;
> + BlockDriverState *bs;
> + BlockRequestHandler *handler;
> + int64_t sector_num;
> + QEMUIOVector *qiov;
> + int nb_sectors;
> + BlockDriverCompletionFunc *cb;
> + void *opaque;
> + BlockDriverAIOCB *acb;
> +};
> +
> +struct BlockQueue {
> + QTAILQ_HEAD(requests, BlockIORequest) requests;
> + BlockIORequest *request;
> + bool flushing;
> +};
> +
> +struct BlockQueueAIOCB {
> + BlockDriverAIOCB common;
> + BlockDriverCompletionFunc *real_cb;
> + BlockDriverAIOCB *real_acb;
> + void *opaque;
> + BlockIORequest *request;
> +};
Now it's pretty easy to merge BlockIORequest and BlockQueueAIOCB into
one struct. That way we don't need to duplicate fields or link
structures together:
typedef struct BlockQueueAIOCB {
BlockDriverAIOCB common;
QTAILQ_ENTRY(BlockQueueAIOCB) entry; /* held requests */
BlockRequestHandler *handler; /* dispatch function */
BlockDriverAIOCB *real_acb; /* dispatched aiocb */
/* Request parameters */
int64_t sector_num;
QEMUIOVector *qiov;
int nb_sectors;
} BlockQueueAIOCB;
This struct is kept for the lifetime of a request (both during
queueing and after dispatch).
> +
> +static void qemu_block_queue_dequeue(BlockQueue *queue, BlockIORequest *request)
> +{
> + BlockIORequest *req;
> +
> + while (!QTAILQ_EMPTY(&queue->requests)) {
> + req = QTAILQ_FIRST(&queue->requests);
> + if (req == request) {
> + QTAILQ_REMOVE(&queue->requests, req, entry);
> + break;
> + }
> + }
> +}
> +
> +static void qemu_block_queue_cancel(BlockDriverAIOCB *acb)
> +{
> + BlockQueueAIOCB *blkacb = container_of(acb, BlockQueueAIOCB, common);
> + if (blkacb->real_acb) {
> + bdrv_aio_cancel(blkacb->real_acb);
> + } else {
> + assert(blkacb->common.bs->block_queue);
> + qemu_block_queue_dequeue(blkacb->common.bs->block_queue,
> + blkacb->request);
Can we use QTAILQ_REMOVE() and eliminate qemu_block_queue_dequeue()?
If the aiocb exists and is not dispatched (real_acb != NULL) then it
must be queued.
> + }
> +
> + qemu_aio_release(blkacb);
> +}
> +
> +static AIOPool block_queue_pool = {
> + .aiocb_size = sizeof(struct BlockQueueAIOCB),
> + .cancel = qemu_block_queue_cancel,
> +};
> +
> +static void qemu_block_queue_callback(void *opaque, int ret)
> +{
> + BlockQueueAIOCB *acb = opaque;
> +
> + if (acb->real_cb) {
> + acb->real_cb(acb->opaque, ret);
> + }
> +
> + qemu_aio_release(acb);
> +}
> +
> +BlockQueue *qemu_new_block_queue(void)
> +{
> + BlockQueue *queue;
> +
> + queue = g_malloc0(sizeof(BlockQueue));
> +
> + QTAILQ_INIT(&queue->requests);
> +
> + queue->flushing = false;
> + queue->request = NULL;
> +
> + return queue;
> +}
> +
> +void qemu_del_block_queue(BlockQueue *queue)
> +{
> + BlockIORequest *request, *next;
> +
> + QTAILQ_FOREACH_SAFE(request, &queue->requests, entry, next) {
> + QTAILQ_REMOVE(&queue->requests, request, entry);
> + g_free(request);
What about the acbs? There needs to be a strategy for cleanly
shutting down completely. In fact we should probably use cancellation
here or assert that the queue is already empty.
> + }
> +
> + g_free(queue);
> +}
> +
> +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;
> + BlockQueueAIOCB *blkacb;
> +
> + if (queue->request) {
> + request = queue->request;
> + assert(request->acb);
> + acb = request->acb;
> + QTAILQ_INSERT_TAIL(&queue->requests, request, entry);
> + queue->request = NULL;
I don't think we need this behavior. There is already requeuing logic
in the flush function: if request->handler() fails then the request is
put back onto the queue and we stop flushing.
So all we need here is:
if (queue->flushing) {
return NULL;
}
This results in the request->handler() failing (returning NULL) and
the flush function then requeues this request.
In other words, during flushing we do not allow any new requests to be enqueued.
> + } else {
> + request = g_malloc0(sizeof(BlockIORequest));
> + request->bs = bs;
> + request->handler = handler;
> + request->sector_num = sector_num;
> + request->qiov = qiov;
> + request->nb_sectors = nb_sectors;
> + request->cb = qemu_block_queue_callback;
> + QTAILQ_INSERT_TAIL(&queue->requests, request, entry);
> +
> + acb = qemu_aio_get(&block_queue_pool, bs,
> + qemu_block_queue_callback, opaque);
> + blkacb = container_of(acb, BlockQueueAIOCB, common);
> + blkacb->real_cb = cb;
> + blkacb->real_acb = NULL;
> + blkacb->opaque = opaque;
> + blkacb->request = request;
> +
> + request->acb = acb;
> + request->opaque = (void *)blkacb;
Here's what this initialization code looks like when BlockIORequest
and BlockQueueAIOCB are merged:
acb = qemu_aio_get(&block_queue_pool, bs, cb, opaque);
acb->handler = handler;
acb->sector_num = sector_num;
acb->qiov = qiov;
acb->nb_sectors = nb_sectors;
acb->real_acb = NULL;
QTAILQ_INSERT_TAIL(&queue->requests, acb, entry);
> + }
> +
> + return acb;
> +}
> +
> +static int qemu_block_queue_handler(BlockIORequest *request)
> +{
> + int ret;
> + BlockDriverAIOCB *res;
> +
> + res = request->handler(request->bs, request->sector_num,
> + request->qiov, request->nb_sectors,
> + request->cb, request->opaque);
Please pass qemu_block_queue_callback and request->acb directly here
instead of using request->cb and request->opaque. Those fields aren't
needed and just add indirection.
> + if (res) {
> + BlockQueueAIOCB *blkacb =
> + container_of(request->acb, BlockQueueAIOCB, common);
> + blkacb->real_acb = res;
> + }
> +
> + ret = (res == NULL) ? 0 : 1;
> +
> + return ret;
> +}
> +
> +void qemu_block_queue_flush(BlockQueue *queue)
> +{
> + queue->flushing = true;
> + while (!QTAILQ_EMPTY(&queue->requests)) {
> + BlockIORequest *request = NULL;
> + int ret = 0;
> +
> + request = QTAILQ_FIRST(&queue->requests);
> + QTAILQ_REMOVE(&queue->requests, request, entry);
> +
> + queue->request = request;
> + ret = qemu_block_queue_handler(request);
> +
> + if (ret == 0) {
> + QTAILQ_INSERT_HEAD(&queue->requests, request, entry);
> + queue->request = NULL;
> + break;
> + }
> +
> + if (queue->request) {
> + g_free(request);
> + }
> +
> + queue->request = NULL;
> + }
> +
> + queue->flushing = false;
> +}
> +
> +bool qemu_block_queue_has_pending(BlockQueue *queue)
> +{
> + return !queue->flushing && !QTAILQ_EMPTY(&queue->requests);
> +}
> diff --git a/block/blk-queue.h b/block/blk-queue.h
> new file mode 100644
> index 0000000..84c2407
> --- /dev/null
> +++ b/block/blk-queue.h
> @@ -0,0 +1,63 @@
> +/*
> + * QEMU System Emulator queue declaration for block layer
> + *
> + * Copyright (c) IBM, Corp. 2011
> + *
> + * Authors:
> + * Zhi Yong Wu <zwu.kernel@xxxxxxxxx>
> + * Stefan Hajnoczi <stefanha@xxxxxxxxx>
Please use linux.vnet.ibm.com addresses and not GMail.
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a copy
> + * of this software and associated documentation files (the "Software"), to deal
> + * in the Software without restriction, including without limitation the rights
> + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
> + * copies of the Software, and to permit persons to whom the Software is
> + * furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
> + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
> + * THE SOFTWARE.
> + */
> +
> +#ifndef QEMU_BLOCK_QUEUE_H
> +#define QEMU_BLOCK_QUEUE_H
> +
> +#include "block.h"
> +#include "qemu-queue.h"
> +
> +typedef BlockDriverAIOCB* (BlockRequestHandler) (BlockDriverState *bs,
> + int64_t sector_num, QEMUIOVector *qiov,
> + int nb_sectors, BlockDriverCompletionFunc *cb,
> + void *opaque);
> +
> +typedef struct BlockIORequest BlockIORequest;
BlockIORequest does not need a forward declaration because only
blk-queue.c uses it. It's a private type that the rest of QEMU should
not know about.
> +
> +typedef struct BlockQueue BlockQueue;
> +
> +typedef struct BlockQueueAIOCB BlockQueueAIOCB;
This is also a private type, callers only know about BlockDriverAIOCB.
Please move to blk-queue.c.
Stefan
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
