Re: [Qemu-devel] [PATCH v5 2/4] block: add the block queue support

[Ram Pai <linuxram@us.ibm.com>]

On Tue, Aug 09, 2011 at 12:17:50PM +0800, Zhi Yong Wu wrote:
> The patch introduce one block queue for QEMU block layer.
> 
> Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
> ---
>  block/blk-queue.c |  141 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  block/blk-queue.h |   73 +++++++++++++++++++++++++++
>  2 files changed, 214 insertions(+), 0 deletions(-)
>  create mode 100644 block/blk-queue.c
>  create mode 100644 block/blk-queue.h
> 
> diff --git a/block/blk-queue.c b/block/blk-queue.c
> new file mode 100644
> index 0000000..f36f3e2
> --- /dev/null
> +++ b/block/blk-queue.c
> @@ -0,0 +1,141 @@
> +/*
> + * QEMU System Emulator queue definition for block layer
> + *
> + * Copyright (c) 2011 Zhi Yong Wu  <zwu.kernel@gmail.com>
> + *
> + * 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.
> + */
> +
> +#include "block_int.h"
> +#include "qemu-queue.h"
> +#include "block/blk-queue.h"
> +
> +/* The APIs for block request queue on qemu block layer.
> + */
> +
> +static void qemu_block_queue_cancel(BlockDriverAIOCB *acb)
> +{
> +    qemu_aio_release(acb);
> +}
> +
> +static AIOPool block_queue_pool = {
> +    .aiocb_size         = sizeof(struct BlockDriverAIOCB),
> +    .cancel             = qemu_block_queue_cancel,
> +};
> +
> +static void qemu_block_queue_callback(void *opaque, int ret)
> +{
> +    BlockDriverAIOCB *acb = opaque;
> +
> +    qemu_aio_release(acb);
> +}
> +
> +BlockQueue *qemu_new_block_queue(void)
> +{
> +    BlockQueue *queue;
> +
> +    queue = qemu_mallocz(sizeof(BlockQueue));
> +
> +    QTAILQ_INIT(&queue->requests);
> +
> +    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);
> +        qemu_free(request);
> +    }
> +
> +    qemu_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;
> +
> +    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);
> +
> +    acb = qemu_aio_get(&block_queue_pool, bs,
> +                       qemu_block_queue_callback, opaque);
> +
> +    request->acb = acb;
> +
> +    return acb;
> +}
> +
> +int qemu_block_queue_handler(BlockIORequest *request)
> +{
> +    int ret;
> +    BlockDriverAIOCB *res;
> +
> +    /* indicate this req is from block queue */
> +    request->bs->req_from_queue = true;
> +
> +    res = request->handler(request->bs, request->sector_num,
> +                           request->qiov, request->nb_sectors,
> +                           request->cb, request->opaque);


should'nt you return with a failure here if res == NULL?
Otherwise  qemu_block_queue_callback() gets called which 
will release the acb.


> +
> +    if (request->acb) {
> +        qemu_block_queue_callback(request->acb, 0);
> +    }
> +
> +    ret = (res == NULL) ? 0 : 1;
> +
> +    return ret;
> +}


RP