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

[Zhi Yong Wu]

On Tue, Aug 9, 2011 at 4:46 PM, Ram Pai <address@hidden> wrote:
> 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 <address@hidden>
>> ---
>>  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  <address@hidden>
>> + *
>> + * 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.
Thanks, Pai. When req handler fails, acb should not be released. A
condition determination should be done before callback function is
invoked. It should be like as below:
    res = request->handler(request->bs, request->sector_num,
                           request->qiov, request->nb_sectors,
                           request->cb, request->opaque);

    ret = (res == NULL) ? 0 : 1;

    if ( ret && request->acb) {
        qemu_block_queue_callback(request->acb, 0);
    }

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



-- 
Regards,

Zhi Yong Wu