Re: [Qemu-devel] [PATCH 2/8] block: add driver operation callbacks

["Benoît Canet" <benoit.canet@irqsave.net>]

The Monday 01 Sep 2014 à 15:43:08 (+0800), Liu Yuan wrote :
> Driver operations are defined as callbacks passed from block upper drivers to
> lower drivers and are supposed to be called by lower drivers.
> 
> Requests handling(queuing, submitting, etc.) are done in protocol tier in the
> block layer and connection states are also maintained down there. Driver
> operations are supposed to notify the upper tier (such as quorum) of the states
> changes.
> 
> For now only two operation are added:
> 
> driver_disconnect: called when connection is off
> driver_reconnect: called when connection is on after disconnection
> 
> Which are used to notify upper tier of the connection state.
> 
> Cc: Eric Blake <eblake@redhat.com>
> Cc: Benoit Canet <benoit@irqsave.net>
> Cc: Kevin Wolf <kwolf@redhat.com>
> Cc: Stefan Hajnoczi <stefanha@redhat.com>
> Signed-off-by: Liu Yuan <namei.unix@gmail.com>
> ---
>  block.c                   | 7 +++++++
>  include/block/block.h     | 7 +++++++
>  include/block/block_int.h | 3 +++
>  3 files changed, 17 insertions(+)
> 
> diff --git a/block.c b/block.c
> index c12b8de..22eb3e4 100644
> --- a/block.c
> +++ b/block.c
> @@ -2152,6 +2152,13 @@ void bdrv_set_dev_ops(BlockDriverState *bs, const BlockDevOps *ops,
>      bs->dev_opaque = opaque;
>  }
>  
> +void bdrv_set_drv_ops(BlockDriverState *bs, const BlockDrvOps *ops,
> +                      void *opaque)
> +{
> +    bs->drv_ops = ops;
> +    bs->drv_opaque = opaque;

We need to be very carefull of the mix between these fields and the infamous
bdrv_swap function.

Also I don't know if "driver operations" is the right name since the BlockDriver structure's
callback could also be named "driver operations".

> +}
> +
>  static void bdrv_dev_change_media_cb(BlockDriverState *bs, bool load)
>  {
>      if (bs->dev_ops && bs->dev_ops->change_media_cb) {
> diff --git a/include/block/block.h b/include/block/block.h
> index 8f4ad16..a61eaf0 100644
> --- a/include/block/block.h
> +++ b/include/block/block.h
> @@ -82,6 +82,11 @@ typedef struct BlockDevOps {
>      void (*resize_cb)(void *opaque);
>  } BlockDevOps;
>  
> +typedef struct BlockDrvOps {
> +    void (*driver_reconnect)(BlockDriverState *bs);
> +    void (*driver_disconnect)(BlockDriverState *bs);
> +} BlockDrvOps;
> +
>  typedef enum {
>      BDRV_REQ_COPY_ON_READ = 0x1,
>      BDRV_REQ_ZERO_WRITE   = 0x2,
> @@ -234,6 +239,8 @@ void bdrv_detach_dev(BlockDriverState *bs, void *dev);
>  void *bdrv_get_attached_dev(BlockDriverState *bs);
>  void bdrv_set_dev_ops(BlockDriverState *bs, const BlockDevOps *ops,
>                        void *opaque);
> +void bdrv_set_drv_ops(BlockDriverState *bs, const BlockDrvOps *ops,
> +                      void *opaque);
>  void bdrv_dev_eject_request(BlockDriverState *bs, bool force);
>  bool bdrv_dev_has_removable_media(BlockDriverState *bs);
>  bool bdrv_dev_is_tray_open(BlockDriverState *bs);
> diff --git a/include/block/block_int.h b/include/block/block_int.h
> index 2334895..9fdec7f 100644
> --- a/include/block/block_int.h
> +++ b/include/block/block_int.h
> @@ -319,6 +319,9 @@ struct BlockDriverState {
>      const BlockDevOps *dev_ops;
>      void *dev_opaque;
>  
> +    const BlockDrvOps *drv_ops;
> +    void *drv_opaque;
> +
>      AioContext *aio_context; /* event loop used for fd handlers, timers, etc */
>  
>      char filename[1024];
> -- 
> 1.9.1
>