Re: [Qemu-devel] [Qemu-block] [PATCH 25/29] qed: Implement .bdrv_co_readv/writev

[Stefan Hajnoczi <stefanha@gmail.com>]

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On Fri, May 26, 2017 at 10:22:06PM +0200, Kevin Wolf wrote:
> Most of the qed code is now synchronous and matches the coroutine model.
> One notable exception is the serialisation between requests which can
> still schedule a callback. Before we can replace this with coroutine
> locks, let's convert the driver's external interfaces to the coroutine
> versions.
> 
> We need to be careful to handle both requests that call the completion
> callback directly from the calling coroutine (i.e. fully synchronous
> code) and requests that involve some callback, so that we need to yield
> and wait for the completion callback coming from outside the coroutine.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/qed.c | 94 +++++++++++++++++++++++++------------------------------------
>  1 file changed, 39 insertions(+), 55 deletions(-)
> 
> diff --git a/block/qed.c b/block/qed.c
> index 6a83df2..29c3dc5 100644
> --- a/block/qed.c
> +++ b/block/qed.c
> @@ -1326,16 +1326,31 @@ static void qed_aio_next_io(QEDAIOCB *acb)
>      }
>  }
>  
> -static BlockAIOCB *qed_aio_setup(BlockDriverState *bs,
> -                                 int64_t sector_num,
> -                                 QEMUIOVector *qiov, int nb_sectors,
> -                                 BlockCompletionFunc *cb,
> -                                 void *opaque, int flags)
> +typedef struct QEDRequestCo {
> +    Coroutine *co;
> +    bool done;
> +    int ret;
> +} QEDRequestCo;
> +
> +static void coroutine_fn qed_co_request_cb(void *opaque, int ret)
> +{
> +    QEDRequestCo *co = opaque;
> +
> +    co->done = true;
> +    co->ret = ret;
> +    qemu_coroutine_enter_if_inactive(co->co);
> +}
> +
> +static int qed_co_request(BlockDriverState *bs, int64_t sector_num,
> +                          QEMUIOVector *qiov, int nb_sectors, int flags)

Missing coroutine_fn.

>  {
> -    QEDAIOCB *acb = qemu_aio_get(&qed_aiocb_info, bs, cb, opaque);
> +    QEDRequestCo co = {
> +        .co     = qemu_coroutine_self(),
> +        .done   = false,
> +    };
> +    QEDAIOCB *acb = qemu_aio_get(&qed_aiocb_info, bs, qed_co_request_cb, &co);
>  
> -    trace_qed_aio_setup(bs->opaque, acb, sector_num, nb_sectors,
> -                        opaque, flags);
> +    trace_qed_aio_setup(bs->opaque, acb, sector_num, nb_sectors, &co, flags);
>  
>      acb->flags = flags;
>      acb->qiov = qiov;
> @@ -1348,43 +1363,24 @@ static BlockAIOCB *qed_aio_setup(BlockDriverState *bs,
>  
>      /* Start request */
>      qed_aio_start_io(acb);
> -    return &acb->common;
> -}
>  
> -static BlockAIOCB *bdrv_qed_aio_readv(BlockDriverState *bs,
> -                                      int64_t sector_num,
> -                                      QEMUIOVector *qiov, int nb_sectors,
> -                                      BlockCompletionFunc *cb,
> -                                      void *opaque)
> -{
> -    return qed_aio_setup(bs, sector_num, qiov, nb_sectors, cb, opaque, 0);
> +    if (!co.done) {
> +        qemu_coroutine_yield();
> +    }
> +
> +    return co.ret;
>  }
>  
> -static BlockAIOCB *bdrv_qed_aio_writev(BlockDriverState *bs,
> -                                       int64_t sector_num,
> -                                       QEMUIOVector *qiov, int nb_sectors,
> -                                       BlockCompletionFunc *cb,
> -                                       void *opaque)
> +static int bdrv_qed_co_readv(BlockDriverState *bs, int64_t sector_num,
> +                             int nb_sectors, QEMUIOVector *qiov)

Missing coroutine_fn.  More below.

>  {
> -    return qed_aio_setup(bs, sector_num, qiov, nb_sectors, cb,
> -                         opaque, QED_AIOCB_WRITE);
> +    return qed_co_request(bs, sector_num, qiov, nb_sectors, 0);
>  }
>  
> -typedef struct {
> -    Coroutine *co;
> -    int ret;
> -    bool done;
> -} QEDWriteZeroesCB;
> -
> -static void coroutine_fn qed_co_pwrite_zeroes_cb(void *opaque, int ret)
> +static int bdrv_qed_co_writev(BlockDriverState *bs, int64_t sector_num,
> +                                      int nb_sectors, QEMUIOVector *qiov)
>  {
> -    QEDWriteZeroesCB *cb = opaque;
> -
> -    cb->done = true;
> -    cb->ret = ret;
> -    if (cb->co) {
> -        aio_co_wake(cb->co);
> -    }
> +    return qed_co_request(bs, sector_num, qiov, nb_sectors, QED_AIOCB_WRITE);
>  }
>  
>  static int coroutine_fn bdrv_qed_co_pwrite_zeroes(BlockDriverState *bs,
> @@ -1392,9 +1388,7 @@ static int coroutine_fn bdrv_qed_co_pwrite_zeroes(BlockDriverState *bs,
>                                                    int count,
>                                                    BdrvRequestFlags flags)
>  {
> -    BlockAIOCB *blockacb;
>      BDRVQEDState *s = bs->opaque;
> -    QEDWriteZeroesCB cb = { .done = false };
>      QEMUIOVector qiov;
>      struct iovec iov;
>  
> @@ -1411,19 +1405,9 @@ static int coroutine_fn bdrv_qed_co_pwrite_zeroes(BlockDriverState *bs,
>      iov.iov_len = count;
>  
>      qemu_iovec_init_external(&qiov, &iov, 1);
> -    blockacb = qed_aio_setup(bs, offset >> BDRV_SECTOR_BITS, &qiov,
> -                             count >> BDRV_SECTOR_BITS,
> -                             qed_co_pwrite_zeroes_cb, &cb,
> -                             QED_AIOCB_WRITE | QED_AIOCB_ZERO);
> -    if (!blockacb) {
> -        return -EIO;
> -    }
> -    if (!cb.done) {
> -        cb.co = qemu_coroutine_self();
> -        qemu_coroutine_yield();
> -    }
> -    assert(cb.done);
> -    return cb.ret;
> +    return qed_co_request(bs, offset >> BDRV_SECTOR_BITS, &qiov,
> +                          count >> BDRV_SECTOR_BITS,
> +                          QED_AIOCB_WRITE | QED_AIOCB_ZERO);
>  }
>  
>  static int bdrv_qed_truncate(BlockDriverState *bs, int64_t offset, Error **errp)
> @@ -1619,8 +1603,8 @@ static BlockDriver bdrv_qed = {
>      .bdrv_create              = bdrv_qed_create,
>      .bdrv_has_zero_init       = bdrv_has_zero_init_1,
>      .bdrv_co_get_block_status = bdrv_qed_co_get_block_status,
> -    .bdrv_aio_readv           = bdrv_qed_aio_readv,
> -    .bdrv_aio_writev          = bdrv_qed_aio_writev,
> +    .bdrv_co_readv            = bdrv_qed_co_readv,
> +    .bdrv_co_writev           = bdrv_qed_co_writev,
>      .bdrv_co_pwrite_zeroes    = bdrv_qed_co_pwrite_zeroes,
>      .bdrv_truncate            = bdrv_qed_truncate,
>      .bdrv_getlength           = bdrv_qed_getlength,
> -- 
> 1.8.3.1
> 
> 

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