Re: [Qemu-devel] [PATCH 4/6] block: switch bdrv_aio_readv() to coroutines

[Kevin Wolf <kwolf@redhat.com>]

Am 05.10.2011 18:17, schrieb Stefan Hajnoczi:
> More sync, aio, and coroutine unification.  Make bdrv_aio_readv() go
> through coroutine request processing.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
> ---
>  block.c |   48 +++++++++++++++++++++++++++++++++++-------------
>  1 files changed, 35 insertions(+), 13 deletions(-)
> 
> diff --git a/block.c b/block.c
> index 90c29db..b83e911 100644
> --- a/block.c
> +++ b/block.c
> @@ -78,6 +78,15 @@ static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,
>      int64_t sector_num, int nb_sectors, QEMUIOVector *qiov);
>  static int coroutine_fn bdrv_co_do_writev(BlockDriverState *bs,
>      int64_t sector_num, int nb_sectors, QEMUIOVector *qiov);
> +static BlockDriverAIOCB *bdrv_co_aio_rw_vector(BlockDriverState *bs,
> +                                               int64_t sector_num,
> +                                               QEMUIOVector *qiov,
> +                                               int nb_sectors,
> +                                               BlockDriverCompletionFunc *cb,
> +                                               void *opaque,
> +                                               bool is_write,
> +                                               CoroutineEntry *entry);
> +static void coroutine_fn bdrv_co_do_rw(void *opaque);
>  
>  static QTAILQ_HEAD(, BlockDriverState) bdrv_states =
>      QTAILQ_HEAD_INITIALIZER(bdrv_states);
> @@ -2346,17 +2355,10 @@ BlockDriverAIOCB *bdrv_aio_readv(BlockDriverState *bs, int64_t sector_num,
>                                   QEMUIOVector *qiov, int nb_sectors,
>                                   BlockDriverCompletionFunc *cb, void *opaque)
>  {
> -    BlockDriver *drv = bs->drv;
> -
>      trace_bdrv_aio_readv(bs, sector_num, nb_sectors, opaque);
>  
> -    if (!drv)
> -        return NULL;
> -    if (bdrv_check_request(bs, sector_num, nb_sectors))
> -        return NULL;
> -
> -    return drv->bdrv_aio_readv(bs, sector_num, qiov, nb_sectors,
> -                               cb, opaque);
> +    return bdrv_co_aio_rw_vector(bs, sector_num, qiov, nb_sectors,
> +                                 cb, opaque, false, bdrv_co_do_rw);
>  }
>  
>  typedef struct BlockCompleteData {
> @@ -2803,6 +2805,7 @@ static void bdrv_co_rw_bh(void *opaque)
>      qemu_aio_release(acb);
>  }
>  
> +/* Invoke .bdrv_co_readv/.bdrv_co_writev */
>  static void coroutine_fn bdrv_co_rw(void *opaque)
>  {
>      BlockDriverAIOCBCoroutine *acb = opaque;
> @@ -2820,13 +2823,32 @@ static void coroutine_fn bdrv_co_rw(void *opaque)
>      qemu_bh_schedule(acb->bh);
>  }
>  
> +/* Invoke bdrv_co_do_readv/bdrv_co_do_writev */
> +static void coroutine_fn bdrv_co_do_rw(void *opaque)
> +{
> +    BlockDriverAIOCBCoroutine *acb = opaque;
> +    BlockDriverState *bs = acb->common.bs;
> +
> +    if (!acb->is_write) {
> +        acb->req.error = bdrv_co_do_readv(bs, acb->req.sector,
> +            acb->req.nb_sectors, acb->req.qiov);
> +    } else {
> +        acb->req.error = bdrv_co_do_writev(bs, acb->req.sector,
> +            acb->req.nb_sectors, acb->req.qiov);
> +    }
> +
> +    acb->bh = qemu_bh_new(bdrv_co_rw_bh, acb);
> +    qemu_bh_schedule(acb->bh);
> +}

The difference between the existing bdrv_co_rw and the new bdrv_co_do_rw
is that the former directly calls drv->... whereas the latter does some
checks first.

I think you could just switch bdrv_co_rw to do the checks. If I'm not
mistaken, the other path is dead code anyway after this change.
Actually, it looks like this series leaves quite a bit of dead code
behind, but I need to apply all patches and check the result to be sure.

Kevin